Treeline dynamics with climate change at the central Nepal Himalaya

Clim Past 10 1277ndash1290 2014wwwclim-pastnet1012772014doi105194cp-10-1277-2014copy Author(s) 2014 CC Attribution 30 License

Treeline dynamics with climate change at the central NepalHimalaya

N P Gaire12 M Koirala 2 D R Bhuju12 and H P Borgaonkar3

1Faculty of Science Nepal Academy of Science and Technology Khumaltar Lalitpur GPO Box 3323 Kathmandu Nepal2Central Department of Environmental Science Tribhuvan University Kathmandu Nepal3Indian Institute of Tropical Meteorology Pune India

Correspondence toN P Gaire (npgaire2007gmailcom)

Received 7 August 2013 ndash Published in Clim Past Discuss 28 October 2013Revised 22 April 2014 ndash Accepted 15 May 2014 ndash Published 4 July 2014

Abstract Treeline shifting in tandem with climate changehas widely been reported from various parts of the world InNepal several impacts of climate change on the physical en-vironment have been observed but study on the biologicalimpacts is lacking This dendrochronological study was car-ried out at the treeline in the high mountain slope of Kalchu-man Lake (3750ndash4003 m asl) area of Manaslu Conserva-tion Area in the central Nepal Himalaya to explore the impactof climate change on the treeline dynamic Two belt transectplots (size 20 m widegt 250 m long) were laid which in-cluded treeline as well as tree species limit Ecological map-ping of all individuals of dominant treesAbies spectabilisandBetula utilis was done and their tree cores were collectedStand character and age distribution revealed an occurrenceof more maturedB utilis (max age 198 years) compared toA spectabilis(max age 160 years)A spectabiliscontainedan overwhelmingly high population (89 ) of younger plants(lt 50 years) indicating its high recruitment rate Populationage structure along the elevation gradient revealed an upwardshifting of A spectabilisat the rate of 261 m yearminus1 sinceAD 1850 The upper distribution limit ofB utilis was foundto be stagnant in the past few decades An increment in plantdensity as well as upward shifting in the studied treeline eco-tones was observed The temporal growth ofA spectabiliswas correlated negatively with the monthly mean and min-imum temperature of June to September of the current andprevious year The regeneration ofA spectabilis on the otherhand was positively correlated with August precipitation andmonthly maximum temperature of the month of the currentyear The growth and regeneration ofA spectabiliswas moresensitive to maximum and minimum temperature rather than

average temperature The growth of theB utilis was mainlylimited by moisture stress during the pre-monsoon seasonAs these two species presented species-specific responses toclimate change with differential pattern in regeneration con-dition much wider differences are anticipated in their pop-ulation status as climate continues to change throughout thecentury

1 Introduction

During the past 100 years the global average surface temper-ature has increased by 074Cplusmn02C and it is projected torise by 14ndash58C by AD 2100 (IPCC 2007) with the mostpronounced and rapid changes at high altitudes and latitudesHowever recent studies have shown spatial and temporal he-terogeneity in the past long-term temperature trend (Marcottet al 2013 PAGES 2k Consortium 2013) Rapid climatechange has many biophysical impacts (IPCC 2007) and al-ready left several biological fingerprints including change inspecies composition of ecological communities range anddistribution shift of species as well as changes in phenologyof the organisms (Parmesan and Yohe 2003 Root et al2003 Parolo and Rossi 2008 Chen et al 2011 Gottfriedet al 2012 Kirdyanov et al 2012 Pauli et al 2012 Webbet al 2012)

The high-altitude limit of forests commonly known astreeline timberline or forest line represents one of themost conspicuous vegetation boundaries (Koumlrner 1998Holtmeier 2009) The position of a treeline is mainly dueto strong growth limitation by low-temperature conditions

Published by Copernicus Publications on behalf of the European Geosciences Union

1278 N P Gaire et al Treeline dynamics with climate change at the Himalaya

(Koumlrner and Paulsen 2004 Holtmeier 2009) Worldwidehigh-altitude climatic treelines are associated with a seasonalmean ground temperature of 67Cplusmn08 SD during the grow-ing period (Koumlrner and Paulsen 2004) So natural treelineecotones are sensitive biomonitors of past and recent climatechange and variability (Kullman 1998) and are well suitedfor monitoring climate change impact (Becker et al 2007)The high-elevation treeline is assumed to represent an idealearly-warning feature that responds to climate change po-sitionally structurally and compositionally (Kullman 19982001 2007 Kirdyanov et al 2012) Many dendroecologi-cal studies have documented that trees at the treeline oftenrespond to climatic warming with an increase in recruitmentor tree density as well as upward advances in the treelineposition (Bradley and Jones 1993 Camarero and Gutieacuterrez2004 Danby and Hik 2007 Kullman 2002 2007 Batlloriand Gutieacuterrez 2008 Kullman and Oumlberg 2009 Leonelliet al 2011 Kirdyanov et al 2012) A meta-analysis of aglobal data set including 166 sites for which treeline dynam-ics had been recorded since AD 1900 showed that the tree-line either advanced (52 of sites) or remained unchangedwhile only few treelines (1 ) declined under heavy anthro-pogenic disturbance (Harsch et al 2009) Treelines that ex-perienced strong winter warming and treelines with a diffuseform are more likely to advance (Harsch et al 2009)

Himalayan ecosystems are facing the impacts of climatechange However uncertainties about our knowledge on therelationships of Hindu KushndashKarakoramndashHimalaya (HKH)treelines to other ecological conditions and processes suchas carbon balance freezing and frost drought soil temper-ature wind snow cover soils regeneration etc are yet tobe explored (Schickhoff 2005) Treelines from Tibet and ad-jacent mountainous regions have shifted very little with cli-mate change (Liang et al 2011 Gou et al 2012 Lv andZhang 2012) However a previous study reported an upwardmovement of the tree species limit due to climate change inthe Himalayas (Dubey et al 2003) High-altitude regions inthe interior of the Nepal Himalaya are little affected by an-thropogenic activities and may therefore provide valuable in-formation to evaluate the isolated consequences of climatechange (Cook et al 2003)

The atmospheric temperature of Nepal has been increas-ing consistently after the mid-1970s with higher rate than theglobal average (Shrestha et al 1999 IPCC 2007) and thewarming has been found to be even more pronounced in thehigh altitudes of the Nepal Himalaya (Shrestha et al 1999Shrestha 2008) However no specific trend in precipitationhas been observed (Shrestha 2008) The effect of warmingtemperature in the Nepal Himalaya is reflected by shrink-ing permafrost areas (Fukui et al 2007) and rapidly retreat-ing glaciers (Fujita et al 1998 Bajaracharya et al 2007Bolch et al 2012 Yao et al 2012) among other phenom-ena Impacts on biological processes including range shiftingof species are also expected but scientific studies on these as-pects are scarce (Schickhoff 2005) Past works on tree rings

in Nepal have identified several promising species for den-drochronological study includingAbies spectabilisandBe-tula utilis (Bhattacharyya et al 1992 Cook et al 2003 Sanoet al 2005 Dawadi et al 2013) which can grow up to thetreeline ecotone (Schickhoff 2005 Ghimire et al 2008) Re-cently researchers from Nepal have initiated dendroecolog-ical studies covering various treeline sites of the Nepal Hi-malaya (Bhuju et al 2010 Suwal 2010 Gaire et al 2011)However concrete results on the treeline shifting due to cli-mate change are yet to be explored

The present study was carried out to (i) ascertain thepresent position of upper forest treeline and species limits(ii) characterize the stand structure and dynamics at the forestline and treeline and (iii) analyse the response of tree growthand regeneration with climate change using both dendroeco-logical and dendroclimatological techniques For this studythe treeline is defined as the ecotone up to where 2 m tall treescan be found and the species limit is defined as the highestposition to which seedlings or saplings of the tree species arepresent Treeline dynamics describe changes in the regenera-tion and population dynamics as well as positional change ofthe tree species in the treeline ecotone

2 Materials and methods

21 Site and species selection

The study was carried out at Manaslu Conservation Area(MCA area 1663 km2) a high mountain protected site inthe central Nepal Himalaya established in AD 1998 MCAhas a diverse natural resource base with sparse human pop-ulation and is relatively inaccessible The area includes ninebioclimatic zones ranging from the lower subtropics to thenival zone with only marginal infrastructure such as roadsIt is the least explored protected area of the country Localpeople depend on agriculture animal husbandry and utiliza-tion of natural resources for their sustenance Buddhism haspositively contributed in protecting the forest and biodiver-sity (Chhetri 2009)

The study site is a mountain slope adjacent to KalchumanLake situated at 3690 m above mean sea level (amsl) Withhuman settlements located not more than 2500 m amslthe study site is little disturbed anthropogenically There isa dense forest in between the settlement and study sitesSoil is rich in humus dark in colour and its depth varieslocally with the steepness of the slope The tree canopyof the treeline ecotone is formed byA spectabilisandB utiliswith aRhododendron campanulatumunderstory andsome scatteredSorbus microphylla Above the treeline oc-cur scrubs ofRhododendron anthopogonand some herba-ceous species The Himalayan silver firA spectabilisis atall evergreen tree endemic to the Himalaya and found be-tween the lower temperate and lower alpine zone (2400ndash4400 m) from Afghanistan to Bhutan (Ghimire et al 2008)

Clim Past 10 1277ndash1290 2014 wwwclim-pastnet1012772014

N P Gaire et al Treeline dynamics with climate change at the Himalaya 1279

Similarly B utilis is a medium-sized deciduous tree whichforms monospecific as well as mixed forests at the upperlimit of the treeline (Ghimire et al 2008)

The climate of the study area is monsoon dominated Themean annual rainfall over the past 30 years (1980ndash2009)at nearby meteorological station at Chame was 967 mm(SD = 280) The monthly average temperature was foundto be highest in July and lowest in November (Fig 1a)The highest recorded temperatures were 234C during June1998 the lowestminus45C during January of 1999 and 2000Over the past 30 years the station experienced a decreas-ing trend in rainfall by 39 mm yearminus1 (n = 30R2

= 0014p lt 052) (Fig 1b) and an increasing trend in mean an-nual temperature by 0017C yearminus1 (Fig 1c) In this stationmonthly mean minimum temperature was decreasing whilemonthly mean maximum temperature was increasing signifi-cantly (Supplementary Fig S1) Similarly mean annual rain-fall at Larke Gorkha was 1252 mm (SD = 535) In Larkeduring the past 30 years (1980ndash2009) there was a significant(n = 30 R2

= 026 p lt 0003) decreasing trend of rainfallby 28 mm yearminus1 (Fig 1b) This decreasing trend is morepronounced and significant (p lt 00003R2

= 046n = 23)after 1987 with a decrease in annual rainfall by 55 mm yearminus1

between 1987 and 2009

22 Field visit and data collection

Field work was carried out in three expeditions two in2010 (MayndashJune and SeptemberndashOctober) and one in 2012(October) After careful observation in transect walk at thetreeline ecotone the upper species limits ofA spectabilisandB utilis were ascertained Two altitudinal transect plots(20 m wide andgt 250 m long) named Transect 1 (T1) andTransect 2 (T2) were marked at two sites of the treeline eco-tone The plots were oriented with their longer side parallelto the maximum slope and covered the current species limitand treeline ecotone (Fig 2) T1 was above the continuousforest while T2 was situated above the middle part of thelake It was also assumed that the lake might hinder the dis-persal of seedlings in the area Individual plants were catego-rized and enumerated into three height classes trees (gt 2 m)saplings (05ndash2 m) and seedlings (lt 05 m) following Wanget al (2006) and Kullman (2007)

Census counts were carried out inside each plot forA spectabilisandB utilis For everyA spectabilisindivid-ual their geographic location in the plot (latitude longitudeand altitude) size (diameter at breast height (DBH) height)growth form and internodes interval of all individuals lessthan 2 m were recorded The age of trees was calculated bytree core analysis while that of seedlings and saplings wereestimated by counting the branch whorls and scars left alongthe main stem (Camarero and Gutieacuterrez 2004 Wang et al2006 Liang et al 2011) This age estimation was also val-idated by comparing it with the age obtained by the numberof tree rings in the basal sections collected from the root col-

1980 1985 1990 1995 2000 2005 2010

Annu

al p

reci

pita

tion

(mm

)

0

500

1000

1500

2000

2500ChameLarke

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Prec

ipita

tion

(mm

)

0

50

100

150

200

250

Tem

pera

ture

(degC

)

2

4

6

8

10

12

14

16

PrecipitationTemperature

1980 1985 1990 1995 2000 2005 2010

Aver

age

annu

al te

mpe

ratu

re (deg

C)

95

100

105

110

115

y = 0017 x + 1055R2 = 0114 p = 0067

(a)

(b)

(c)

y = -3855 x + 8657R2 = 0014 plt052

y = -2822 x + 57365R2 = 0262 plt0003

Figure 1Climatic trend in the local stations mean monthly (1980ndash2009) precipitation and temperature at Chame Manang station(a)annual trend of precipitation at Larke Gorkha and Chame(b) andtrend of mean annual temperature at Chame(c)

lar of saplings and seedlings (n = 34) The age estimates bywhorl count and ring count correlated positively (R2

= 091P lt 00001) but the internodes or whorl count ages aresystematically lower by 157plusmn 033 years (max 4 years) insaplings and 127 years in seedlings These suggest that thewhorl count method can give a fairly accurate indicationof the age of saplings and seedlings of conifer species likeA spectabilis

23 Tree core and cut-stump collection and analysis

Tree cores were collected using the increment borer (HagloumlfSweden) following the standard technique suggested byFritts (1976) and Speer (2010) The cores were collectedfrom the base of each and breast (13 m) height of some indi-viduals ofA spectabilisandB utilis in the plots Cores werealso collected from the largerA spectabilisandB utilis treesoutside of the plots A total of 249 cores and cut-stump sam-ples (172A spectabilisand 77B utilis) were collected (Sup-plementary Table S1) Collected core and cut-stump samples

wwwclim-pastnet1012772014 Clim Past 10 1277ndash1290 2014


Figure 2 Location map of the study area showing the position ofthe study plots and local meteorological stations(a) and a photo ofthe study site showing treeline species limit and some portion ofKalchuman Lake(b)

were taken to the Dendro-lab of the Nepal Academy of Sci-ence and Technology for laboratory analysis

Collected cores were air dried mounted sanded and pol-ished using successively finer grades of sand paper (100ndash1000 grits size) until optimal surface resolution allowed an-nual rings to be visible under the microscope Each ringwas counted under the stereo zoom microscope and assigneda calendar year The width of each ring was measured tothe nearest 001 mm precision with the LINTABTM mea-suring system attached to a PC with the TSAP Win soft-ware package (Rinn 1996) All the tree cores were cross-dated by matching patterns of relatively wide and narrowrings to account for the possibility of ring-growth anomaliessuch as missing or false rings or measurement error Cross-dating was done using the alignment plotting technique andalso looking the math graphs The quality of cross-datingof each sample was checked using the computer programCOFECHA (Holmes 1983)

The corrected ring-width data were standardized usingthe computer program ARSTAN (Cook 1985) The ring-width series were standardized using conventional detrend-ing methods with appropriate options of a negative expo-nential linear or cubic spline curve to each series Eachring-width-index series was then pre-whitened using autore-gressive modelling to remove any autocorrelation effects(Cook 1987) Finally three chronologies ndash namely standardresidual and ARSTAN ndash were prepared using the correctedsample Various chronology statistics like mean sensitivitystandard deviation autocorrelation mean series correlationsignal-to-noise ratio expressed population signal (EPS) andvariance explained were calculated to assess the quality ofthe site chronologies Temporal changes in the mean ra-dial growth were assessed by doing regime shift (significantchanges in mean radial growth) analysis (Rodionov 2004)Regime shift was detected based on a statistical test wherebydata are processed in time sequence and the hypothesis ofa regime shift or discontinuity is tested for each new obser-vation (Rodionov 2004 2006) We set the cutoff parameterat 10 years in order to detect changes in mean radial growthdriven by high-frequency events and used a 95 level of sig-nificance

24 Population demography regeneration and treelinedynamics

The age obtained from cross-dated samples was used for de-mographic analysis after the necessary correction for years tocore height and years to centre of missed pith Such correc-tion was made using agendashheight regression and agendashdiameterregression combined with the fitting of a circle template tothe ring curvature so as to estimate the distance of the coreto the centre (Camarero and Gutieacuterrez 2004 Speer 2010)For B utilis cores from representative sample trees cover-ing different diameter at breast height (DBH) classes werecollected Based on the ages of 39Betula trees a regres-sion analysis model between DBH and age was established(Fig 3) and the relationship was used to estimate the age ofall B utilis trees from which tree cores were not taken

The regeneration rate was determined by age histogramusing the number of seedlings saplings and tree individualsThe treeline dynamics was analysed by density distributionof tree sapling and seedling as well as the elevation-wise agedistribution of the studied species The upper species limitexpansion was studied by observing the age of each indi-vidual in the entire plot following Camarero and Gutieacuterrez(2004) and Liang et al (2011) In order to calculate the rateof species limit shift the maximum elevation of live indi-viduals and the position of the oldest individual within eachtransect was determined Then the species limit shift rate(m yearminus1) was calculated by dividing the change in specieslimit elevation (position) by the time elapsed



DBH (cm)

0 10 20 30 40 50 60

Age

(yea

rs)

0

50

100

150

200

250

300

Age = 3765 DBH + 2334

R2 = 0847 p lt 00005

Figure 3 Diameter at breast height (DBH) versus age ofBetulautilis from the Kalchuman Lake area Manaslu Conservation Area

25 Climatic influence on radial growth andregeneration

Before proceeding to the response analysis of tree growth andclimate the seasonality of tree growth was defined Field ob-servation and tree ring data have shown that radial growth ofA spectabilisat treeline sites ceases in SeptemberndashOctober(Sano et al 2005) Because climate in the preceding grow-ing season often influences tree growth in the following year(Fritts 1976) we analysed the influence of temperature andprecipitation since June of the previous growth year until Oc-tober of the current growth year Simple Pearson correlationcoefficients were used to quantify relationships between tree-ring chronologies and climate variables ie monthly average(Tmean) maximum (Tmax) and minimum (Tmin) temperatureand total monthly precipitation Similarly influence of sea-sonal climate on radial growth was also assessed for fourseasons ndash namely winter (DecemberndashFebruary DJF) pre-monsoon (MarchndashMay MAM) monsoon (JunendashSeptemberJJAS) and post-monsoon (OctoberndashNovember ON) In ad-dition to this influence of annual average temperature andtotal precipitation was also calculated One of the major dif-ficulties in undertaking dendroclimatic research in Nepal re-lates to the paucity of long meteorological records for statis-tically calibrating the tree rings because most of the weatherstations in Nepal were only established after 1960 for pre-cipitation and 1970 for temperature (Bhattacharyya et al1992 Cook et al 2003) Available climatic data (1980ndash2009) of the nearest stations at Chame (2833prime N 8414prime Eand 2680 m asl) of Manang and Larke Samdo (2840prime N8437prime E and 3650 m asl) of Gorkha were used (Fig 2)Missing values were replaced by average value of the samemonthrsquos data

To investigate the relationship between regeneration andclimate change recruitment or age data were summed across5-year intervals as the finest resolution to take into account

uncertainties in age estimates and compared with monthlyclimate records compiled into 5-year averages over the sametime period (Camarero and Gutieacuterrez 1999 Wang et al2006) To describe the climatendashrecruitment relationshipsmonthly climatic data (mean maximum and minimum tem-peratures and total precipitation) from Chame Jagat andLarke stations were used Climatic factors limiting regenera-tion were identified from linear correlation analysis betweenregeneration and climatic data

3 Results

31 Treeline position and structural parameters

The species limit ofA spectabiliswas recorded at 3984 m(GPS e-Trex) in Transect 1 (T1) and 3955 m in Transect 2(T2) and its treeline at 3907 m in T1 and 3830 m in T2 In thecase ofB utilis the treeline and species limit were recordedat the same elevation in both transects ie at 3996 m in T1and 4003 m in T2

Structural parameters (age DBH and basal area) revealedthat both of the species were more matured in T1 thanin T2 (Supplementary Table S2) The maximum age ofA spectabilisand B utilis was higher in T1 than in T2A spectabilistree density ranged from 50 to 280 trees haminus1The total basal area ofB utilis in both plots was higher thanA spectabilis The DBH distribution ofA spectabilisshowedbimodal distribution in T1 with peaks at 0ndash10 cm and 35ndash40 cm DBH class (Supplementary Fig S2) In T2 the DBHdistribution of the same species had an inverse-J-shaped dis-tribution indicating continuous regeneration in the area DBHdistribution ofB utilis in T1 presents a unimodal bell shapeindicating poor regeneration in recent years However DBHdistribution of the same species in T2 indicates better recruit-ment of individuals Similar trends were observed in heightdistribution Age class distribution of the species was het-erogeneous with an inverse-J-shaped and unimodal to multi-modal bell-shaped distribution (Supplementary Fig S3)

32 Age structure regeneration and treeline dynamics

The demographic distribution ofA spectabilisandB utilisrevealed the recruitment and mortality pattern over time(Supplementary Fig S3 and Fig 4) The age distribution ofA spectabilisindicated that the species was established in theearly 1850s in T1 (Fig 4a) and in the 1950s in T2 (Fig 4b)The population ofA spectabiliswas dominated by young in-dividuals comprising 89 of the population below 50 yearsage The recruitment ofA spectabiliswas slow in the 1850saccelerating after 1950 and again after 1980 This could berelated to increased temperature in the area The recruitmentof B utilis started from the 1820s in T1 then reached T2 inthe 1840s (Fig 4a b) The proportion of young populationof B utilis was low (13 of the populationlt 50 years old)as compared to middle-aged trees (42 being 50ndash100 years



old) and older ones (45 over 100 years old) Recruitmentof B utilis was lower at the beginning in both transects butincreased slowly to peak in the 1880s in T1 and the 1930sin T2 Regeneration oscillated between the 1880s and 1940sand declined steadily since then

The comparative age of the two tree species shows thatthe regeneration of theB utilis was higher before the recruit-ment of A spectabilisin the treeline community Spatialndashtemporal assessment of the upper species limit distributionof A spectabilisand B utilis revealed that the position ofB utilis was higher than the position ofA spectabilisin bothtransects (Fig 4a b) SimilarlyB utilis colonized the areaearlier thanA spectabilis Seedlings of theA spectabilisspecies were found about 80 m higher than trees indicat-ing upward migration (Fig 4c) Matured trees and youngseedlings were mostly dominant at lower elevation indicat-ing stand densification as well T2 had a lower number ofseedlings than T1 Seedlings ofB utilis were not recorded inboth transects but some were observed just outside the plotsOn the basis of the temporal and spatial distribution of theages ofB utilis at an elevation gradient we calculated thatthe seedlings of the species were established at 3860 m be-tween the 1810s and 1820s and at 3990 m during the 1890s(Fig 4a) TheA spectabilison the other hand made a tree-line community around 1850 at 3765 m and reached 3907 m(presentA spectabilistreeline) during the 1950s Seedlingsof this species are now established at 3984 m which isclose to the upper limit ofB utilis The average upwardmovement of the upper distribution limit ofA spectabilisat the study sites was calculated to be 261 m yearminus1 (156ndash366 m yearminus1) The upward shifting ofA spectabiliswasmore pronounced in T2 with migration rate of 366 m yearminus1while it was 156 m yearminus1 in T1

The densities of saplings and seedlings ofA spectabilis(Supplementary Table S3) indicated that its regeneration washigher in T1 than in T2 and also higher than that ofB utilisin both transects As there was a presence of a large numberof saplings and seedlings ofA spectabilisin the site but noseedlings ofB utilis it is anticipated that the structure andcomposition of this treeline community will change in thefuture

33 Tree-ring chronology

A 229-year-long (AD 1782ndash2010) standard tree ring chronol-ogy of A spectabiliswas prepared using 46 cores from29 trees (Fig 5) The chronology revealed that there was noconstant increment in the growth of trees but it fluctuatedthrough time The years 1818 1819 1974 and 1999 werecharacterized by particularly poor growth whereas the years1789 1814 and 2009 resulted in particularly wide rings Re-sults of the regime shift analysis suggest that there have beenconstant changes in mean radial growth which are domi-nated by short periods of above-average radial growth Twomajor periods with low radial growth were 36 years start-

Figure 4 (a b) Spatial and temporal variation in the recruitmentof tree species in T1 and T2(c) Temporal upward shifting ofAbiesspectabilisalong an elevation gradient in the study site

ing in 1854 and 63 years starting in 1940 The period cen-tred on 1905 is one of the shortest with below-average radialgrowth In the recent period (after 2000) the radial growthis increased Several statistics that were calculated for thetime span of AD 1782ndash2010 and for the period of overlap(AD 1920ndash2005) of all tree-ring series indicated a high den-drochronological potential (Supplementary Table S4) The



0

5

10

15

20

25

30

35

40

45

50

0

02

04

06

08

1

12

14

16

1827 1847 1867 1887 1907 1927 1947 1967 1987 2007

Nu

mb

er

of

rad

ii

Rin

g w

idth

in

de

x

Year

Std chronology

Regime shift

Number of radii

EPSlt85

Figure 5 Tree-ring standard chronology ofAbies spectabilisfromthe Kalchuman Lake area of Manaslu central Nepal

value of mean sensitivity and standard deviation is 0136and 018 respectively The mean series correlation withintree was high (0467) as compared to the mean correlationbetween tree (0192) and among all radii (0196) The EPSan indication of how well the site chronology estimates thepopulation chronology was above (0918) the threshold limitof 085 (Wigley et al 1984) The signal-to-noise ratio was1123 and the percentage of variance explained by the firsteigenvector was 244

34 Response of tree growth and regeneration to climatechange

The radial growth of theAbies spectabilisat the studied tree-line was limited by the low temperature with a positive corre-lation between the ring width chronology and monthly max-imum temperature in most of the month and a negative re-lationship with minimum temperature (Fig 6a) The radialgrowth inA spectabiliscorrelated negatively with the meanand minimum monthly temperature of JunendashSeptember (r gt

minus045 P lt 001) months of the current year (Fig 6a)However above-average monthly mean and minimum tem-perature in the previous year growing period (ie JunendashSeptember) influence negatively the current year growthLooking at the influence of seasonal climate on the growtheffect of monsoon season (JJAS) temperature on the growthwas stronger than individual counterpart months with a sig-nificant negative correlation with seasonal mean (r = minus058P lt 001) and minimum (r = minus066 P lt 001) tempera-ture

Though weak radial growth was negatively correlatedwith monthly precipitation of most months of the currentyear (Fig 6a) The relationship between ring width and pre-cipitation of February of the current year was slightly nega-tive (r = minus038P lt 005) The precipitation during the pre-vious year June correlated positively (r = 045 P lt 005)with current year growth The correlation between the radialgrowth and seasonal sum of precipitation was weak and notsignificant statistically

-08

-07

-06

-05

-04

-03

-02

-01

00

01

02

03

04

05

06

pJ pJ pA pS pO pN pD J F M A M J J A S O Avg MAM JJAS ON DJF

Co

rrela

tio

n co

eff

icie

nt

Month and season

Tmean Tmax Tmin Precipitation(a)

-10

-08

-06

-04

-02

00

02

04

06

08

10

12

J F M A M J J A S O N D Avg

Co

rrela

tio

n c

oeff

icie

nt

Month

Tmean Tmax Tmin Precipitation(b)

Figure 6Relationship between theAbies spectabilisrsquo radial growthwith climate data (monthly mean maximum minimum seasonalaverage temperature and monthly and seasonal sum of precipita-tion) (a) and relationship between regenerationA spectabiliswithmonthly climate(b) the black horizontal line indicates a signifi-cant correlation at the 95 confidence limit for a two-tailed testand dashed horizontal line indicates a significant correlation at the99 confidence limit for a two-tailed test(a) shows the responseof radial growth to the monthly climate of June in the previousyear to October of the current year as well as seasonal averagespJndashpD signify JunendashDecember of the previous year MAM JJASON and DJF are the mean temperature and the sum of precipitationof MarchndashMay JunendashSeptember OctoberndashNovember and previousyear December to the current year February respectively For cli-matic influence on the regeneration of theA spectabilisa climaticwindow of 12 months of current years as well as annual average oftemperature or annual sum of precipitation are used

Regeneration of theA spectabiliswas favoured posi-tively by the above-average monthly maximum tempera-ture during most of the months and above-average precipi-tation during dry warm summer months (Fig 6b) The rela-tionship between regeneration and monthly maximum tem-perature of the most of the months of the current yearwas positive and statistically significant (r gt 08 P lt 005)while the relationship was negative but significant with themonthly minimum temperature of JunendashSeptember of thecurrent year (r gt minus07 P lt 005) (Fig 6b) The relation



between regeneration and precipitation in August (r = 096P lt 001) was positive and statistically significant (Fig 6b)

It is also evident from Fig 6a and b that the growth and re-generation ofA spectabilisis more sensitive to minimum ormaximum temperature rather than average temperature be-cause correlation with these is more positive or negative thanaverage

4 Discussion

41 Position structure and dynamics of treeline

The position and dynamics of the treeline are the result ofthe interaction of several factors including topoclimate (ra-diation temperature precipitation length of growing sea-son and snow cover) topography (slope inclination reliefforms) ecology of tree species (regeneration seed disper-sal successional stage) site history (climate oscillationsfire human impact insect attacks) current biotic (browsingtrampling diseases and insect pests) and anthropogenic in-fluences (burning logging grazing recreation and tourism)(Holtmeier 2009) The position of the treeline species lineand species composition varies across the globe as well as atsites within the region (Koumlrner 1998 Miehe et al 2007)

In Nepal the position of the treeline varies between theeastern central and western region (Schickhoff 2005) Re-gardless of the plots theA spectabilistreeline in the presentstudy was found at 3907 m asl and theB utilis treelineat 4003 m asl which is comparable to the other studies(Koumlrner and Paulsen 2004 Bhuju et al 2010 Liang etal 2014) However along the western slope of Mt An-napurna the upper timberline (B utilis R campanulatum)at north-facing slopes ascends to 4000ndash4100 m asl and toeven 4400 m asl on the Nilgiri northern slope (Schickhoff2005) Bhuju et al (2010) found the treeline at 4050 m aslin Pangboche of Sagarmatha (Everest) region in easternNepal while at the Lauribina of Langtang in central Nepalit was observed at about 3900 m asl (Gaire et al 2011)Generally the upper treeline elevations in the Hindu KushndashKarakoramndashHimalaya (HKH) region increases along twogradients a NWndashSE gradient (corresponding to higher tem-perature sums at the same elevations along the mountainarc) and a peripheralndashcentral gradient from the Himalayansouthern slope to the Great Himalayan range and the Tibetanhighlands (related to the combined effects of continentalityand mass elevation both leading to higher temperature sums)(Schickhoff 2005)

The size class distribution of the tree species reflects itsregeneration status (Lv and Zhang 2012) In our study thestructural parameters of the studied species not only var-ied between the plots but also between the species Com-pared to T1 the smaller maximum DBH and younger ageof both theA spectabilisandB utilis in T2 indicated someinfluence of the Kalchuman Lake in the seed dispersal in

the T2 from downside seed source The DBH class dis-tribution of A spectabilisshows a bimodal distribution inT1 with peaks in lower and intermediate DBH classes Thepeak in low DBH class indicates that regeneration in re-cent years is good The DBH distribution ofB utilis indi-cated poor regeneration during recent years The age dis-tribution was an inverse-J-shaped to multimodal bell-shapedwith intra and inter-species differences Such kind of differ-ences in the age and DBH class distribution ofA spectabilisand B utilis have been observed in the other treeline eco-tones of Nepal (Shrestha et al 2007 Bhuju et al 2010Suwal 2010 Gaire et al 2011) indicating site- and species-specific regeneration condition in the Nepal Himalaya Sim-ilarly at the A spectabilistreeline near the Everest regionon the Tibetan side Lv and Zhang (2012) observed a mul-timodal age distribution with peaks during 1840ndash1860 andin recent years The differential spatio-temporal regenerationpattern reflected in the multimodal size (age andor DBH)class distributions were also observed in various treelinesites of different mountains for examplePicea schrenkianain central Tianshan mountains NW China (Wang et al2006) Juniperus przewalskiiin the Qilian Mountains NETibetan Plateau (Gou et al 2012)Pinus uncinatain thePyrenees Mountains NE Spain (Camarero and Gutieacuterrez2007 Batllori and Gutieacuterrez 2008)Picea glaucain SWYukon Canada (Danby and Hik 2007)Larix gmelinii inthe Putorana Mountains northern Siberia (Kirdyanov et al2012) Picea glauca Picea marianaand Larix laricinaAbies lasiocarpanear Churchill Manitoba Canada (Mametand Kershaw 2012)

Recruitment critical determinant of the rate of forest ortreeline shift (Camarero and Gutieacuterrez 2007) has been foundto be more sensitive to climate than adult mortality in harshenvironments where competition is low because recruitmenthas lower climatic thresholds than adult mortality (Lloyd1997) The recruitment ofA spectabiliswas high during the1940ndash1950s and after the 1980s which might have been facil-itated by the warm winter temperature in the area and in thecountry (Cook et al 2003 Sano et al 2005) In the presentstudy the establishment ofA spectabiliswas high in recentdecades as compared to the previous decades which is con-sistent to the findings of other studies in the treeline in the Hi-malaya and other mountains (eg Gaire et al 2011 Batlloriand Gutieacuterrez 2008 Liang et al 2011 Lv and Zhang 2012)Lv and Zhang (2012) found a significant tree recruitment inthe recent three decades and sporadic recruitment in earlierperiods AD 1760ndash1960 in the treeline of the Tibetan sideof the Everest region Liang et al (2011) also found an in-creased recruitment of Smith fir (Abies georgei) after the1950s with an abrupt increase in the 1970s in the Tibetanmountains Batllori and Gutieacuterrez (2008) also observed pastand recent synchronous recruitment trends ofPinus uncinatawith climate change at the treelines in the Iberian easternrange of the Pyrenees



The regeneration at the treeline can be sporadic or episodic(Cuevas 2002 Lv and Zhang 2012) Patchy spatial distri-bution of A spectabilis with gaps in some diameter andage classes observed in the present study indicates episodicregeneration The dominance of multimodal age distribu-tions also observed in other alpine or forestndashtundra ecotonestudies suggested that recruitment in treeline forest ecosys-tems is episodic or sporadic rather than gradual (Szeiczand MacDonald 1995 Cuevas 2002 Batllori and Gutieacuter-rez 2008 Lv and Zhang 2012) The spatial distribution ofB utilis was more regular compared toA spectabilis In thisstudy establishment ofB utilis in recent decades has beenvery poor as compared to previous decades A similar trendhas been reported from other treeline sites (eg Bhuju et al2010) Recruitment of the species was slow in the beginningin both transects and increased gradually to reach at peakin the 1880s in T1 and the 1930s in T2 with a slight oscil-lation between the 1880s and 1940s Similarly the regen-eration ofB utilis before the arrival ofA spectabiliswashigh The maximum age ofB utilis was higher thanRhodo-dendron campanulatum(Prabina Rana personal communi-cation 2013) and the maximum age ofR campanulatumwashigher than that ofA spectabilis Hence this area might havebeen colonized by shade intolerantB utilis trees followedby shade tolerant understory treeR campanulatumand waslater invaded byA spectabilistrees

Seedling establishment is an important factor dictating thealtitudinal limits of treeline species (Hughes et al 2009)Evidently treeline rise depends on seeds produced at the lo-cal treeline rather than propagulae from more distant sourcesat lower elevations (Kullman 2007) At and above the tree-line in the study site in the Kalchuman Lake area we ob-served neither long-living krummholz nor sub-fossil woodof A spectabilisandB utilis Matured and young seedlingsof A spectabilisand maturedBetula were mostly domi-nant in the lower elevation However some seedlings ofA spectabilis probably due to global warming have beenthriving at much higher elevation than tree individuals Thisstudy indicated both stand densification and upward migra-tion as recorded in many other areas (Camarero and Gutieacuter-rez 2004 Danby and Hik 2007 Gehrig-Fasel et al 2007Kullman 2007 Vittoz et al 2008 Batllori and Gutieacuterrez2008 Kullman and Oumlberg 2009 Kirdyanov et al 2012)

Consistent with the observed trend in the other treelines(Kullman 2001 2002 Wang et al 2006 Kullman andOumlberg 2009 Gou et al 2012) spatio-temporal age distri-bution showed that there was regeneration as well as upwardmigration of theB utilis until the end of the 1960s thoughthe exact rate is not calculated The peak in the tree estab-lishment in the past corresponds to the warm episode in bothwinter and summer reconstructed temperature in the country(Cook et al 2003) However we observed a stagnant upperdistribution limit or treeline ofB utilis in the recent decadesalong with poor regeneration in spite of temperature warm-ing in the area

Average upward shifting of the upper distribution limit ofA spectabilisat the treeline ecotone was about 261 m yearminus1

with some local variation in the area This upward migra-tion trend of A spectabilisis consistent with the upwardmigration (34 m per decade) ofA spectabilisin the tree-line of the Samagaun region of the MCA (Suwal 2010)and ofPinus wallichiana(19 and 14 m per decade on south-and north-facing slope) in the western Himalayas (Dubey etal 2003) Several other studies have reported treeline shift-ing in different regions of the world (eg Camarero andGutieacuterrez 2004 Danby and Hik 2007 Gehrig-Fasel et al2007 Harsch et al 2009 Kullman 2001 2002 Kullman andOumlberg 2009 Chauchard et al 2010 Leonelli et al 2011Mamet and Kershaw 2012 Kirdyanov et al 2012) Kullmanand Oumlberg (2009) presented a regional-scale treeline rise ofBetula pubescenssspczerepanovii Picea abiesandPinussylvestrisin the southern Swedish Scandes of 70ndash90 m on av-erage with maximum up-shifts of about 200 m since aroundAD 1915 Danby and Hik (2007) found an increased tree den-sity as well as an advancement of Spruce (Picea glauca) tree-line elevation by 65ndash85 m on south-facing slopes in south-west Yukon Canada during the early to mid-20th centurySimilarly Kirdyanov et al (2012) observed an upslope shiftof theLarix gmelinii treeline position by approximately 30ndash50 m in altitude in the Putorana Mountains northern Siberiaduring the last century However Liang et al (2011) foundno significant upward movement in fir treelines in the Ti-betan Plateau despite the warming in the region in the past200 years

42 Climatic factors affecting tree growth andregeneration dynamics

Growth of a tree is associated with several abiotic fac-tors including climate (Fritts 1976) The radial growth ofA spectabilisfluctuated over time with changing climate andwe did not observe constant increment or decrement in thegrowth However a few studies have reported enhanced ra-dial growth of the western Himalayan conifer during recentyears (eg Borgaonkar et al 2011)

The radial growth ofA spectabilisin the treeline is moreresponsive to temperature change Tree growth was posi-tively correlated with temperature (Tmean Tmax and Tmin)from October of the previous year to April of the current yearwhich indicates that temperature before the growing seasonhas a main influence on the radial growth during the subse-quent growing period High winter temperature may induceearly melting of snow with the easy availability of melt waterfor growth in the growing season Studies also have reportedthat monthly and seasonal winter temperatures are morelimiting than growing-season temperatures to annual radialgrowth in many upper treeline sites with a positive relation-ship with winter temperature (Braumluning 2004 Pederson etal 2004 Borgaonkar et al 2011) Braumluning (2004) found astrong positive relationship between theA spectabilisring



width chronology and temperature from November of theprevious year to January of the current year in western NepalBorgaonkar et al (2011) found a strong positive relation-ship between the mean annual and winter (DJF) temperaturesof the concurrent year and growth of western Himalayanconifers The negative relationship observed in the presentstudy with the pre-monsoon (MAM) and monsoon season(JJAS) temperature points towards some threshold temper-ature or moisture stress because increase in temperature inthe pre-monsoon and monsoon season without adequate rain-fall increases the evapotranspiration which leads to a soil-moisture deficit and limits tree growth (Fritts 1976 Cook etal 2003 Yadav et al 2004) Other studies from the NepalHimalaya revealed that tree-ring width ofA spectabilisiscontrolled by pre-monsoon (MarchndashMay) climate with neg-ative correlation with temperature and positive correlationwith precipitation indicating that moisture availability in thisseason limits tree growth (Cook et al 2003 Sano et al2005 Chhetri and Thapa 2010 Gaire et al 2011) Mostof these studies were carried out in the areas much lowerthan treeline ecotone Similarly Yadav et al (2004) ob-tained a negative as well as weakened relationship betweenthe mean temperature of the summer months and growth ofA spectabilisfrom treeline sites of the western Himalaya Inthe present study responses of radial growth ofA spectabilisto minimum and maximum temperatures in the current yearwere in the opposite direction This indicated to the preva-lence of threshold temperature above or below which theresponses become less sensitive to temperature or nonlin-ear to inverted U-shaped relationship (Paulsen et al 2000DrsquoArrigo et al 2004 Yadav et al 2004 Kullman 2007)

In this study the radial growth ofA spectabiliswas lessstrongly correlated with precipitation having significant neg-ative correlation only with February precipitation As pre-cipitation in these months falls in the form of snow highsnow accumulation delays the growth initiation shorten-ing the growth period and ultimately resulting in the for-mation of a narrow ring A deep snow pack in late win-ter has been shown to effectively reduce radial growth ratesby maintaining low soil temperatures and delaying initiationof cambial expansion (Fritts 1976 Pederson et al 2004)Above-average moisture during the June of the previous yearpositively affects the current yearrsquos growth because above-average moisture during summer and early autumn may pro-mote storage of carbohydrates and bud formation thus en-hancing growth during the following year (DrsquoArrigo et al2001 Fritts 1976) The weak correlation ofA spectabilisra-dial growth with the precipitation also might be due to its sen-sitivity to temperature compared to precipitation Converselythe weak correlation could be due to variation in the precip-itation between the sampling sites and the local stations be-cause in the Himalaya precipitation fluctuates greatly evenwithin a small geographic area (Barros et al 2004)

The relationship between regeneration ofA spectabilisand the monthly maximum temperature of Januaryndash

December of the current year was positive while the rela-tion was negative with the monthly minimum temperature ofthe current year indicating that low temperature adverselyaffects seedling survival Severe soil frosts during cold win-ters were considered to be critical factors in the control ofseedling survival by causing needle and shoot desiccationor fine-root mortality (Koumlrner 2003 Pederson et al 2004Kullman 2007) Since extremely low cool-season temper-atures facilitate the formation of abrasive ice crystals thatphysically damage trees and as a result often limit estab-lishment at the treeline this research also supports other re-cent studies documenting the critical impact of warmer win-ter temperatures on increased tree establishment in the high-elevation ecotones (Kullman 2007 Kullman and Oumlberg2009 Harsch et al 2009) The regeneration ofA spectabiliswas positively correlated with the precipitation of MayndashAugust months The positive relationship with the precipi-tation of these summer months implies that as the temper-ature had already attained the minimum threshold requiredfor growth high rainfall aids the survival and growth ofseedlings and saplings During summer months the temper-ature in the study area would often be high So low rainfallmay create a desiccation situation and will have a strongereffect on recruitment because germinants are more sensitiveto drought stress (Hughes et al 2009 Fajardo and McIn-tire 2012) Comparing with the past long-term reconstructedclimatic data (Cook et al 2003) the regeneration ofAbiesseems to be good during the episode of warm winter and coolsummer Hence temperature plays a crucial role in growthand regeneration ofA spectabilisat the natural climatic tree-line of the Himalaya

From a similar study at the timberline on the Tibetanside of the Everest region Lv and Zhang (2012) found thatA spectabilisrecruitments in 5-year classes were positivelycorrelated with their corresponding monthly mean air tem-peratures in June and September and with Palmer DroughtSeverity Index in June The relationship was inverse for re-generation and ring width From a study in a treeline on thesoutheastern Tibetan Plateau Liang et al (2011) found asignificant positive correlation between the Smith fir (Abiesgeorgeivarsmithii) recruitment and both summer and wintertemperatures Wang et al (2006) reported that several con-secutive years of high minimum summer temperature andspring precipitation was the main factors favouring the estab-lishment ofPicea schrenkianafollowing germination withinthe treeline ecotone in the central Tianshan mountains

Due to the lack of young seedlings and saplings as wellas long climatic data we could not calculate the climaticvariables limiting growth and regeneration ofB utilis How-ever in a recent study in birch timberlines from the NepalHimalaya including our study site Liang et al (2014) usingCRU grid-based data found a significant positive relationshipbetween tree-ring width chronologies ofB utilis and pre-cipitation in May and the pre-monsoon (MAM) season anda less strong negative relationship with temperature They



concluded that Himalayan birch growth at the upper timber-lines is persistently limited by moisture availability duringthe pre-monsoon season The poor regeneration and lack ofrecent shifting of theB utilis in the area might result fromthe increasing moisture stress (Liang et al 2014) as avail-able precipitation data from the nearby station have shown adecreasing trend in the precipitation In addition to the influ-ence of climate change the lack of recent regeneration of theB utilis seedlings could be due to the influence of increasedcanopy cover by its own and associated tree species as wellas dense shrub scrub becauseB utilis seedlings could not es-tablish under their own closed canopy even if they produceviable seeds (Shrestha et al 2007) because the birch seedlinggrowth is facilitated by direct sunlight (Shrestha et al 2007Hughes et al 2009)

43 Treeline dynamics with climate change

The relationships between regeneration treeline shifts andclimate change may be more complex because climate mayaffect tree recruitment and treeline advance rate in differ-ent ways (Camarero and Gutieacuterrez 2004 Wang et al 2006Kirdyanov et al 2012) A treeline ascent implies severalconsecutive processes production of viable seeds disper-sal availability of adequate regeneration sites germinationseedling survival and persistence until the individual reachesadulthood (Wang et al 2006 Kullman 2007) Climate vari-ability affects all these sequential stages but the same cli-matic variable can enhance one of these processes while in-hibiting another one (Camarero and Gutieacuterrez 2004 Wanget al 2006) At a global scale treelines are consideredto be constrained primarily by growing season temperature(Koumlrner and Paulsen 2004) However at many alpine tree-line ecotones both winter and summer temperatures are of-ten key constraints on tree recruitment (Harsch et al 2009Liang et al 2011) including other local site conditionsspeciesrsquo traits and feedback effects (Danby and Hik 2007Batllori and Gutieacuterrez 2008) In the present alpine treelinestudy the establishment of theA spectabilisis also controlledby both winter and summer climatic events

An increasing number of studies have demonstrated thattree population density at treelines can respond quickly to ris-ing temperatures (Camarero and Gutieacuterrez 2004 Kullman2007 Liang et al 2011) compared to the changes in tree-line position because of the great longevity and phenotypicplasticity of tree individuals (MacDonald et al 1998 Lloyd2005) If temperature is the primary and dominant driverfor both recruitment and growth these processes should bepositively synchronized (Fajardo and McIntire 2012) Someprevious studies at treelines found concurrent synchronies(MacDonald et al 1998 Batllori and Gutieacuterrez 2008) andlagged synchronies of tree growth and regeneration in bothpositive and negative directions with climate change (Fajardoand McIntire 2012) We found a synchronous regenera-tion of A spectabilisin the treeline ecotone with climate

warming The climatic conditions that enhance radial growthof A spectabiliswere almost similar to the climatic con-ditions that enhance regeneration with slight variation insome months which is similar to the findings of other stud-ies (Szeicz and MacDonald 1995 Camarero and Gutieacuterrez1999) In this study both the recruitment and radial growth ofA spectabiliswas found to be associated positively with win-ter temperature and negatively with summer (MayndashAugust)monthsrsquo mean and minimum temperature

In spite of the regeneration ofA spectabilisabove the ex-isting treeline the pace of future treeline shifting with cli-mate change may not necessarily be the same because aseedling takes many years from establishment to reach itstree height (in the treelineAbies took more than 30 yearsto reach 2 m height) and then to develop into a forest stand(Lloyd 2005) On the other hand there are no seedlings ofB utilis in and above the treeline It will take several decadesfor newly establishedBetulaseedlings to develop and form atreeline even if they establish now AsA spectabilisin thetreeline is more responsive to temperature change an ad-vance of this at the natural treeline of the Himalaya withclimate change may continue if a long-term warming trendstimulates growth frequently enough even in cooler years orif low temperature eventsperiods which limit growth and re-generation are insignificant or if there would not be waterdeficit in plants which could offset the expected positive ef-fects from temperature increase in tree establishment growthand the upslope advance of treeline (Paulsen et al 2000Daniels and Veblen 2004 Wang et al 2006 Kullman andOumlberg 2009) In the case ofB utilis Liang et al (2014) re-ported that the birch treeline of the Himalaya is a rare caseof a drought-induced alpine timberline and Himalayan birchat its upper distribution boundary is increasingly at risk ofsurvival Therefore downslope range shift may occur as a re-sponse to global-change-type droughts (Liang et al 2014)With the supportive evidence of differential life history re-generation condition and the species-specific response ofthese two treeline species to climate change it is clear that inaddition to treeline position the community structure in thestudied treeline in the Himalaya is going to change if currentclimate change and response pattern continues

5 Conclusions

The present study provided a recruitment pattern and dynam-ics history of Himalayan fir and Mountain birch at the high-altitude treeline of the Manaslu region central Nepal Hi-malaya Although regeneration patterns varied between thespecies increasing trends of stand densification as well asupward shifting of the studied treeline is evident The up-ward shift of A spectabilisat MCA was estimated to be261 m yearminus1 In spite of upward migration ofB utilis upto the mid-20th century its upper distribution limit has beenstagnant in recent years The regeneration ofA spectabilis



was positively related with monthly maximum temperaturein most of the months of the current year and precipitation inMayndashAugust although the growth of theB utilis can be alsolimited by pre-monsoon precipitation (Liang et al 2014)Spatial and temporal variations in age structure and regen-eration pattern of these two species and their species-specificresponse to climate indicated that the plant communities atthe treeline ecotone in the Nepal Himalaya were sensitive toclimate change and the studied treeline is changing Stud-ies incorporating multiple species and covering other proxyevidence like pollen from lake sediments could enhance ourunderstanding of spatio-temporal treeline and vegetation dy-namics in association with climate change

The Supplement related to this article is available onlineat doi105194cp-10-1277-2014-supplement

AcknowledgementsNAST provided a PhD fellowship to the firstauthor We are grateful to the National Trust for Nature Conserva-tion for the permission to conduct this study at MCA We thankArbindra Shrestha Janardan Mainali and local field assistants fortheir help during field work Amalava Bhattarcharyya MoinuddinAhmed Kumar Mainali and Madan Krishna Suwal provided withvaluable suggestions in improving the paper and plotting the fig-ures Russell E Train Education for Nature Programme WWFUSprovided a professional grant to the first author to participate indendrochronology training in China APN and PAGES supportedparticipation in the PAGES Goa 2013 meetings We are grateful tothe four anonymous reviewers Thorsten Kiefer and Anne-LaureDaniau for their constructive comments

Edited by A-L Daniau

References

Bajaracharya S M Mool P K and Shrestha B R Impacts ofclimate change on Himalayan glaciers and glacial lakes casestudies on GLOF and associated hazard in Nepal and BhutanICIMOD and UNEP Kathmandu 2007

Barros A P Kim G Williams E and Nesbitt S W Probingorographic controls in the Himalayas during the monsoon us-ing satellite imagery Nat Hazards Earth Syst Sci 4 29ndash51doi105194nhess-4-29-2004 2004

Batllori E and Gutieacuterrez E Regional tree line dynamics in re-sponse to global change in the Pyrenees J Ecology 96 1275ndash1288 doi101111j1365-2745200801429x 2008

Becker A Korner C Brun J J Gusian A and TappeinerU Ecological and land use studies along elevational gradientsMt Res Dev 27 59ndash65 2007

Bhattacharyya A Lamarche V C J and Hughes M K Tree ringchronologies from Nepal Tree Ring Bulletin 52 59ndash66 1992

Bhuju D R Carrer M Gaire N P Soraruf L Riondato RSalerno F and Maharjan S R Dendroecological study of high

altitude forest at Sagarmatha National Park Nepal in Con-temporary research in Sagarmatha (Mt Everest) region Nepaledited by Jha P K and Khanal I P Nepal Academy of Sci-ence and Technology Lalitpur 119ndash130 2010

Bolch T Kulkarni A Kaumlaumlb A Huggel C Paul F Cogley J GFrey H Kargel J S Fujita K Scheel M Bajracharya S andStoffe M The state and fate of Himalayan glaciers Science336 310ndash314 doi101126science1215828 2012

Borgaonkar H P Sikder A B and Ram S High altitude for-est sensitivity to the recent warming A tree-ring analysis ofconifers from Western Himalaya India Quatern Int 236 158ndash166 2011

Bradley R S and Jones P D Little Ice Agersquo summer temperaturevariations their nature and relevance to recent global warmingtrends Holocene 3 367ndash376 1993

Braumluning A Tree-ring studies in the Dolpo-Himalya (westernNepal) TRACE ndash Tree Rings in Archaeology Climatology andEcology 2 8ndash12 2004

Camarero J J and Gutieacuterrez E Structure and recent recruitmentat alpine forest-pasture ecotones in the Spanish central PyreneesEcoscience 6 451ndash464 1999

Camarero J J and Gutieacuterrez E Pace and pattern of recent treeline dynamics response of ecotones to climatic variability in theSpanish Pyrenees Climatic Change 63 181ndash200 2004

Camarero J J and Gutieacuterrez E Response ofPinus uncinatare-cruitment to climate warming and changes in grazing pressure inan isolated population of the Iberian System (NE Spain) ArctAntarct Alp Res 39 210ndash217 2007

Chauchard S Beilhe F Denis N and Carcaillet C An increasein the upper tree-limit of silver fir (Abies albaMill) in the Alpssince the mid-20th century A land-use change phenomenonForest Ecol Manag 259 1406ndash1415 2010

Chen I-C Hill J K Ohlemuumlller R Roy D B andThomas C D Rapid range shifts of species associated withhigh levels of climate warming Science 333 1024ndash1026doi101126science1206432 2011

Chhetri M Culture environment and biodiversity ndash linkages andadapting strategy of the local inhabitants in Tsum Valley of Man-aslu Conservation Area Nepal Prakriti 19ndash21 2009

Chhetri P K and Thapa S Tree ring and climate change in Lang-tang National Park central Nepal Our Nature 8 139ndash143 2010

Cook E R A time series analysis approach to tree-ring standard-ization PhD thesis The University of Arizona Arizona USA1985

Cook E R The decomposition of tree-ring series for environmen-tal studies Tree-Ring Bulletin 47 37ndash59 1987

Cook E R Krusic P J and Jones P D Dendroclimatic signalsin long tree-ring chronologies from the Himalayas of Nepal IntJ Climatol 23 707ndash732 2003

Cuevas J G Episodic regeneration at theNothofagus pumilioalpine timberline in Tierra del Fuego Chile J Ecology 90 52ndash60 2002

DrsquoArrigo R D Schuster W S F Lawrence D M Cook E Dand Wiljanen M Climate-growth relationships of eastern hem-lock and chestnut oak from Black Rock Forest in the highlands ofsoutheastern New York Tree-Ring Research 57 183ndash190 2001

DrsquoArrigo R D Kaufmann R K Davi N Jacoby G CLaskowski C Myneni R B and Cherubini P Thresholds forwarming-induced growth decline at elevational tree line in the



Yukon Territory Canada Global Biogeochem Cy 18 GB3021doi1010292004GB002249 2004

Danby R K and Hik D S Variability contingency and rapidchange in recent subarctic alpine tree line dynamics J Ecology95 352ndash363 doi101111j1365-2745200601200x 2007

Daniels L D and Veblen T T Spatiotemporal influences of cli-mate on altitudinal treeline in northern Patagonia Ecology 851284ndash1296 2004

Dawadi B Liang E Tian L Devkota L P and Yao T Pre-monsoon precipitation signal in tree rings of timberlineBe-tula utilis in the central Himalayas Quatern Int 283 72ndash77doi101016jquaint201205039 2013

Dubey B Yadav R R Singh J and Chaturvedi R Upward shiftof Himalayan pine in Western Himalaya India Current Sci 851135ndash1136 2003

Fajardo A and McIntire E J B Reversal of multicentury treegrowth improvements and loss of synchrony at mountain treelines point to changes in key drivers J Ecol 100 782ndash794doi101111j1365-2745201201955x 2012

Fritts H C Tree Rings and Climate Cambridge University PressCambridge 567 pp 1976

Fujita K Takeuchi N and Seko K Glaciological observationsof Yala Glacier in Langtang Valley Nepal Himalayas 1994 and1996 Bulletin of Glacier Research 16 75ndash81 1998

Fukui K Fujii Y Ageta Y and Asahi K Changes in the lowerlimit of Mountain permafrost between 1973 and 2004 in theKhumbu Himal the Nepal Himalayas Global Planet Change55 251ndash256 2007

Gaire N P Dhakal Y R Lekhak H C Bhuju D R andShah S K Dynamics ofAbies spectabilisin Relation to Cli-mate Change at the Treeline Ecotone in Langtang National ParkNepal Journal of Science and Technology 12 220ndash229 2011

Gehrig-Fasel J Guisan A and Zimmermann N E Tree lineshifts in the Swiss Alps Climate change or land abandonmentJ Veg Sci 18 571ndash582 2007

Ghimire S K Sapkota I B Oli B R and Prajuli R R Nontimber forest products of Nepal Himalaya WWF Nepal Kath-mandu Nepal 2008

Gottfried M Pauli H Futschik A Akhalkatsi M Barancok PAlonso J L B Coldea G Dick J Erschbamer B CalzadoM R F Kazakis G Krajci J Larsson P Mallaun MMichelsen O Moiseev D Moiseev P Molau U MerzoukiA Nagy L Nakhutsrishvili G Pedersen B Pelino G Pus-cas M Rossi G Stanisci A Theurillat J P Tomaselli MVillar L Vittoz P Vogiatzakis I and Grabherr G Continent-wide response of mountain vegetation to climate change NatureClimate Change 2 111ndash115 doi101038nclimate1329 2012

Gou X Zhang F Yang Deng Ettl G J Yang M GaoL and Fang K Patterns and dynamics of tree-line re-sponse to climate change in the eastern Qilian Moun-tains northwestern China Dendrochronologia 30 121ndash126doi101016jdendro201105002 2012

Harsch M A Hulme P E McGlone M S and DuncanR P Are treelines advancing A global meta-analysis of tree-line response to climate warming Ecol Lett 12 1040ndash1049doi101111j1461-0248200901355x 2009

Holmes R L Computer assisted quality control in tree ring datingand measuring Tree-Ring Bulletin 43 69ndash78 1983

Holtmeier F K Mountain timberlines Ecology patchiness anddynamics Springer Havixbeck Germanybdquo 2009

Hughes N M Johnson D M Akhalkatsi M and Ab-daladze O CharacterizingBetula litwinowii seedling mi-crosites at the alpine-treeline ecotone central Greater CaucasusMountains Georgia Arct Antarct Alpine Res 41 112ndash118doi1016571938-4246(08-021)[HUGHES]20CO2 2009

IPCC Climate change 2007 the physical sciences basis Summaryfor policy makers Geneva IPCC 2007

Kirdyanov A V Hagedorn F Knorre A A Fedotova E VVaganov E A Naurzbaev M M Moiseev P A and RiglingA 20th century treeline advance and vegetation changes alongan altitudinal transect in the Putorana Mountains northernSiberia Boreas 41 56ndash67 2012

Koumlrner C Re-assessment of high elevation tree line positions andtheir explanation Oecologia 115 445ndash459 1998

Koumlrner C Alpine Plant Life 2nd Edn Springer 2003Koumlrner C and Paulsen J A world-wide study of high altitude tree-

line temperatures J Biogeogr 31 713ndash732 2004Kullman L Tree-limits and montane forests in the Swedish Scan-

des sensitive biomonitors of climate change and variability Am-bio 27 312ndash321 1998

Kullman L 20th century climate warming trend and tree-limit risein the southern Scandes of Sweden Ambio 30 72ndash80 2001

Kullman L Rapid recent range-margin rise of tree and shrubspecies in the Swedish Scandes J Ecol 90 68ndash77 2002

Kullman L Tree line population monitoring ofPinus sylvestrisin the Swedish Scandes 1973ndash2005 implications for tree linetheory and climate change ecology J Ecol 95 41ndash52 2007

Kullman L and Oumlberg L Post-Little Ice Age tree line rise andclimate warming in the Swedish Scandes a landscape ecologicalperspective J Ecol 97 415ndash429 2009

Leonelli G Pelfini M di Cella U M and Garavaglia V Cli-mate warming and the recent treeline shift in the European Alpsthe role of geomorphological factors in high-altitude sites AM-BIO 40 264ndash273 doi101007s13280-010-0096-2 2011

Liang E Wang Y Eckstein D and Luo T Little change inthe fir tree-line position on the southeastern Tibetan Plateau after200 years of warming New Phytol 190 760ndash769 2011

Liang E Dawadi B Pederson N and Eckstein D Is the growthof birch at the upper timberline in the Himalayas limited bymoisture or by temperature Ecology in press doi10189013-19041 2014

Lloyd A H Response of tree-line populations of foxtail pine (Pi-nus balfouriana) to climate variation over the last 1000 yearsCan J Forest Res 27 936ndash942 1997

Lloyd A H Ecological histories from Alaskan tree lines provideinsight into future change Ecology 86 1687ndash1695 2005

Lv X and Zhang Q B Asynchronous recruitment history ofAbiesspectabilisalong an altitudinal gradient in the Mt Everest regionJ Plant Ecol 5 147ndash156 2012

MacDonald G M Szeicz J M Claricoates J and Dale K AResponse of the central Canadian treeline to recent climatechanges Ann Assoc Am Geogr 88 183ndash208 1998

Mamet S D and Kershaw G P Subarctic and alpine tree linedynamics during the last 400 years in north-western and cen-tral Canada J Biogeogr 39 855ndash868 doi101111j1365-2699201102642x 2012



Marcott S A Shakun J D Clark P U and MixA C A reconstruction of regional and global tempera-ture for the past 11300 years Science 339 1198ndash1201doi101126science1228026 2013

Miehe G Miehe S Vogel J Co S and Duo L Highest tree-line in the northern hemisphere found in southern Tibet Mt ResDev 27 169ndash173 2007

PAGES 2k Consortium Continental-scale temperature variabilityduring the past two millennia Nature Geosci 6 339ndash346doi101038NGEO1797 2013

Parmesan C and Yohe G A globally coherent fingerprint of cli-mate change impacts across natural systems Nature 42 37ndash422003

Parolo G and Rossi G Upward migration of vascular plants fol-lowing a climate warming trend in the Alps Basic Appl Ecol9 100ndash107 2008

Pauli H Gottfried M Dullinger S Abdaladze O AkhalkatsiM Benito Alonso J L Coldea G Dick J Erschbamer BFernaacutendez Calzado R Ghosn D Holten J I Kanka R Kaza-kis G Kollaacuter J Larsson P Moiseev P Moiseev D MolauU Molero Mesa J Nagy L Pelino G Puscas M Rossi GStanisci A Syverhuset A-O Theurillat J P Tomaselli MUnterluggauer P Villar L Vittoz P and Grabherr G Recentplant diversity changes on Europersquos mountain summits Science336 353ndash355 doi101126science1219033 2012

Paulsen J Weber U M and Koumlrner C Tree growth near treelineabrupt or gradual reduction with altitude Arct Antarct AlpRes 32 14ndash20 2000

Pederson N Cook E R Jacoby G C Peteet D M and Grif-fin K L The influence of winter temperatures on the annualradial growth of six northern range margin tree species Den-drochronologia 22 7ndash29 doi101016jdendro2004090052004

Rinn F TSAP-Win Reference Manual Version 053 RinntechHeidelberg 1996

Rodionov S N A sequential algorithm for testing cli-mate regime shifts Geophys Res Lett 31 L09204doi1010292004GL019448 2004

Rodionov S N Use of prewhitening in climate regimeshift detection Geophys Res Lett 33 L12707doi1010292006GL025904 2006

Root T L Price J T Hall K R Schneider S H RosenzweigkC and Pounds J A Fingerprints of global warming on wildanimals and plants Nature 421 57ndash60 2003

Sano M Furuta F Kobayashi O and Sweda T Temperaturevariations since the mid-18th century for western Nepal as re-constructed from tree-ring width and density ofAbies spectabilisDendrochronologia 23 83ndash92 2005

Schickhoff U The upper timberline in the Himalayas Hindu Kushand Karakorum a review of geographical and ecological aspectsin Mountain ecosystems studies in treeline ecology edited byBroll G and Keplin B Springer Berlin Germany 275ndash3542005

Shrestha A B Wake C P Mayewski P A and Dibb J E Max-imum temperatrure trend in the Himalaya and its vicinityAnanalysis based on temperature records from Nepal for period1971ndash94 J Climate 12 2775ndash2787 1999

Shrestha B B Ghimire B Lekhak H D and Jha P K Regen-eration of tree line Birch (Betula utilisD Don) forest in trans-Himalayan dry valley in central Nepal Mt Res Dev 27 250ndash258 2007

Shrestha M L Challenging climates adapting to change Nepalbaseline study British Council 100 pp 2008

Speer J H Fundamentals of tree ring research The University ofArizona Press Tucson 2010

Suwal M K Tree species line advance ofAbies spectabilisinManaslu Conservation Area Nepal Himalaya MSc thesis Cen-tral Department of Botany Tribhuvan University Kathmandu2010

Szeicz J M and MacDonald G M Recent white spruce dynam-ics at the subarctic alpline tree line of north-western CanadaJ Ecol 83 873ndash885 1995

Vittoz P Rulence B Largey T and Freleacutechoux F Effects ofclimate and land-use change on the establishment and growth ofcembran pine (Pinus cembraL) over the altitudinal treeline eco-tone in the central Swiss Alps Arct Antarct Alp Res 40 225ndash232 doi1016571523-0430(06-010)[VITTOZ]20CO2 2008

Wang T Zhang Q-B and Ma K Tree line dynamics in relationto climatic variability in the central Tianshan Mountains north-western China Global Ecol Biogeogr 15 406ndash415 2006

Webb L B Whetton P H Bhend J Darbyshire R Briggs P Rand Barlow E W R Earlier wine-grape ripening driven by cli-matic warming and drying and management practices NatureClimate Change 2 259ndash264 doi101038NCLIMATE14172012

Wigley T M L Briffa K R and Jones P D The average valueof correlated time series with applications in dendroclimatologyand hydrometeorology Int J Climatol 8 33ndash54 1984

Yadav R R Singh J Dubey B and Chaturvedi R Varyingstrength of relationship between temperature and growth of high-level fir at marginal ecosystems in western Himalaya India Cur-rent Sci 86 1152ndash1156 2004

Yao T Thompson L Yang W Yu W Gao Y Guo X YangX Duan K Zhao H Xu B Pu J Lu A Xiang Y KattelD B and Joswiak D Different glacier status with atmosphericcirculations in Tibetan Plateau and surroundings Nature ClimateChange 2 663ndash667 doi101038NCLIMATE1580 2012



(Koumlrner and Paulsen 2004 Holtmeier 2009) Worldwidehigh-altitude climatic treelines are associated with a seasonalmean ground temperature of 67Cplusmn08 SD during the grow-ing period (Koumlrner and Paulsen 2004) So natural treelineecotones are sensitive biomonitors of past and recent climatechange and variability (Kullman 1998) and are well suitedfor monitoring climate change impact (Becker et al 2007)The high-elevation treeline is assumed to represent an idealearly-warning feature that responds to climate change po-sitionally structurally and compositionally (Kullman 19982001 2007 Kirdyanov et al 2012) Many dendroecologi-cal studies have documented that trees at the treeline oftenrespond to climatic warming with an increase in recruitmentor tree density as well as upward advances in the treelineposition (Bradley and Jones 1993 Camarero and Gutieacuterrez2004 Danby and Hik 2007 Kullman 2002 2007 Batlloriand Gutieacuterrez 2008 Kullman and Oumlberg 2009 Leonelliet al 2011 Kirdyanov et al 2012) A meta-analysis of aglobal data set including 166 sites for which treeline dynam-ics had been recorded since AD 1900 showed that the tree-line either advanced (52 of sites) or remained unchangedwhile only few treelines (1 ) declined under heavy anthro-pogenic disturbance (Harsch et al 2009) Treelines that ex-perienced strong winter warming and treelines with a diffuseform are more likely to advance (Harsch et al 2009)

Himalayan ecosystems are facing the impacts of climatechange However uncertainties about our knowledge on therelationships of Hindu KushndashKarakoramndashHimalaya (HKH)treelines to other ecological conditions and processes suchas carbon balance freezing and frost drought soil temper-ature wind snow cover soils regeneration etc are yet tobe explored (Schickhoff 2005) Treelines from Tibet and ad-jacent mountainous regions have shifted very little with cli-mate change (Liang et al 2011 Gou et al 2012 Lv andZhang 2012) However a previous study reported an upwardmovement of the tree species limit due to climate change inthe Himalayas (Dubey et al 2003) High-altitude regions inthe interior of the Nepal Himalaya are little affected by an-thropogenic activities and may therefore provide valuable in-formation to evaluate the isolated consequences of climatechange (Cook et al 2003)

The atmospheric temperature of Nepal has been increas-ing consistently after the mid-1970s with higher rate than theglobal average (Shrestha et al 1999 IPCC 2007) and thewarming has been found to be even more pronounced in thehigh altitudes of the Nepal Himalaya (Shrestha et al 1999Shrestha 2008) However no specific trend in precipitationhas been observed (Shrestha 2008) The effect of warmingtemperature in the Nepal Himalaya is reflected by shrink-ing permafrost areas (Fukui et al 2007) and rapidly retreat-ing glaciers (Fujita et al 1998 Bajaracharya et al 2007Bolch et al 2012 Yao et al 2012) among other phenom-ena Impacts on biological processes including range shiftingof species are also expected but scientific studies on these as-pects are scarce (Schickhoff 2005) Past works on tree rings

in Nepal have identified several promising species for den-drochronological study includingAbies spectabilisandBe-tula utilis (Bhattacharyya et al 1992 Cook et al 2003 Sanoet al 2005 Dawadi et al 2013) which can grow up to thetreeline ecotone (Schickhoff 2005 Ghimire et al 2008) Re-cently researchers from Nepal have initiated dendroecolog-ical studies covering various treeline sites of the Nepal Hi-malaya (Bhuju et al 2010 Suwal 2010 Gaire et al 2011)However concrete results on the treeline shifting due to cli-mate change are yet to be explored

The present study was carried out to (i) ascertain thepresent position of upper forest treeline and species limits(ii) characterize the stand structure and dynamics at the forestline and treeline and (iii) analyse the response of tree growthand regeneration with climate change using both dendroeco-logical and dendroclimatological techniques For this studythe treeline is defined as the ecotone up to where 2 m tall treescan be found and the species limit is defined as the highestposition to which seedlings or saplings of the tree species arepresent Treeline dynamics describe changes in the regenera-tion and population dynamics as well as positional change ofthe tree species in the treeline ecotone

2 Materials and methods

21 Site and species selection

The study was carried out at Manaslu Conservation Area(MCA area 1663 km2) a high mountain protected site inthe central Nepal Himalaya established in AD 1998 MCAhas a diverse natural resource base with sparse human pop-ulation and is relatively inaccessible The area includes ninebioclimatic zones ranging from the lower subtropics to thenival zone with only marginal infrastructure such as roadsIt is the least explored protected area of the country Localpeople depend on agriculture animal husbandry and utiliza-tion of natural resources for their sustenance Buddhism haspositively contributed in protecting the forest and biodiver-sity (Chhetri 2009)

The study site is a mountain slope adjacent to KalchumanLake situated at 3690 m above mean sea level (amsl) Withhuman settlements located not more than 2500 m amslthe study site is little disturbed anthropogenically There isa dense forest in between the settlement and study sitesSoil is rich in humus dark in colour and its depth varieslocally with the steepness of the slope The tree canopyof the treeline ecotone is formed byA spectabilisandB utiliswith aRhododendron campanulatumunderstory andsome scatteredSorbus microphylla Above the treeline oc-cur scrubs ofRhododendron anthopogonand some herba-ceous species The Himalayan silver firA spectabilisis atall evergreen tree endemic to the Himalaya and found be-tween the lower temperate and lower alpine zone (2400ndash4400 m) from Afghanistan to Bhutan (Ghimire et al 2008)












1980 1985 1990 1995 2000 2005 2010

Annu

al p

reci

pita

tion

(mm

)

0

500

1000

1500

2000

2500ChameLarke


Prec

ipita

tion

(mm

)

0

50

100

150

200

250

Tem

pera

ture

(degC

)

2

4

6

8

10

12

14

16


1980 1985 1990 1995 2000 2005 2010

Aver

age

annu

al te

mpe

ratu

re (deg

C)

95

100

105

110

115

y = 0017 x + 1055R2 = 0114 p = 0067

(a)

(b)

(c)

y = -3855 x + 8657R2 = 0014 plt052

y = -2822 x + 57365R2 = 0262 plt0003

















DBH (cm)

0 10 20 30 40 50 60

Age

(yea

rs)

0

50

100

150

200

250

300

Age = 3765 DBH + 2334

R2 = 0847 p lt 00005






3 Results

















0

5

10

15

20

25

30

35

40

45

50

0

02

04

06

08

1

12

14

16

1827 1847 1867 1887 1907 1927 1947 1967 1987 2007

Nu

mb

er

of

rad

ii

Rin

g w

idth

in

de

x

Year

Std chronology

Regime shift

Number of radii

EPSlt85







-08

-07

-06

-05

-04

-03

-02

-01

00

01

02

03

04

05

06


Co

rrela

tio

n co

eff

icie

nt

Month and season


-10

-08

-06

-04

-02

00

02

04

06

08

10

12


Co

rrela

tio

n c

oeff

icie

nt

Month








4 Discussion

































5 Conclusions








References






































































































1980 1985 1990 1995 2000 2005 2010

Annu

al p

reci

pita

tion

(mm

)

0

500

1000

1500

2000

2500ChameLarke


Prec

ipita

tion

(mm

)

0

50

100

150

200

250

Tem

pera

ture

(degC

)

2

4

6

8

10

12

14

16


1980 1985 1990 1995 2000 2005 2010

Aver

age

annu

al te

mpe

ratu

re (deg

C)

95

100

105

110

115

y = 0017 x + 1055R2 = 0114 p = 0067

(a)

(b)

(c)

y = -3855 x + 8657R2 = 0014 plt052

y = -2822 x + 57365R2 = 0262 plt0003

















DBH (cm)

0 10 20 30 40 50 60

Age

(yea

rs)

0

50

100

150

200

250

300

Age = 3765 DBH + 2334

R2 = 0847 p lt 00005






3 Results

















0

5

10

15

20

25

30

35

40

45

50

0

02

04

06

08

1

12

14

16

1827 1847 1867 1887 1907 1927 1947 1967 1987 2007

Nu

mb

er

of

rad

ii

Rin

g w

idth

in

de

x

Year

Std chronology

Regime shift

Number of radii

EPSlt85







-08

-07

-06

-05

-04

-03

-02

-01

00

01

02

03

04

05

06


Co

rrela

tio

n co

eff

icie

nt

Month and season


-10

-08

-06

-04

-02

00

02

04

06

08

10

12


Co

rrela

tio

n c

oeff

icie

nt

Month








4 Discussion

































5 Conclusions








References






































































































DBH (cm)

0 10 20 30 40 50 60

Age

(yea

rs)

0

50

100

150

200

250

300

Age = 3765 DBH + 2334

R2 = 0847 p lt 00005






3 Results

















0

5

10

15

20

25

30

35

40

45

50

0

02

04

06

08

1

12

14

16

1827 1847 1867 1887 1907 1927 1947 1967 1987 2007

Nu

mb

er

of

rad

ii

Rin

g w

idth

in

de

x

Year

Std chronology

Regime shift

Number of radii

EPSlt85







-08

-07

-06

-05

-04

-03

-02

-01

00

01

02

03

04

05

06


Co

rrela

tio

n co

eff

icie

nt

Month and season


-10

-08

-06

-04

-02

00

02

04

06

08

10

12


Co

rrela

tio

n c

oeff

icie

nt

Month








4 Discussion

































5 Conclusions








References





























































































DBH (cm)

0 10 20 30 40 50 60

Age

(yea

rs)

0

50

100

150

200

250

300

Age = 3765 DBH + 2334

R2 = 0847 p lt 00005






3 Results

















0

5

10

15

20

25

30

35

40

45

50

0

02

04

06

08

1

12

14

16

1827 1847 1867 1887 1907 1927 1947 1967 1987 2007

Nu

mb

er

of

rad

ii

Rin

g w

idth

in

de

x

Year

Std chronology

Regime shift

Number of radii

EPSlt85







-08

-07

-06

-05

-04

-03

-02

-01

00

01

02

03

04

05

06


Co

rrela

tio

n co

eff

icie

nt

Month and season


-10

-08

-06

-04

-02

00

02

04

06

08

10

12


Co

rrela

tio

n c

oeff

icie

nt

Month








4 Discussion

































5 Conclusions








References






































































































0

5

10

15

20

25

30

35

40

45

50

0

02

04

06

08

1

12

14

16

1827 1847 1867 1887 1907 1927 1947 1967 1987 2007

Nu

mb

er

of

rad

ii

Rin

g w

idth

in

de

x

Year

Std chronology

Regime shift

Number of radii

EPSlt85







-08

-07

-06

-05

-04

-03

-02

-01

00

01

02

03

04

05

06


Co

rrela

tio

n co

eff

icie

nt

Month and season


-10

-08

-06

-04

-02

00

02

04

06

08

10

12


Co

rrela

tio

n c

oeff

icie

nt

Month








4 Discussion

































5 Conclusions








References





























































































0

5

10

15

20

25

30

35

40

45

50

0

02

04

06

08

1

12

14

16

1827 1847 1867 1887 1907 1927 1947 1967 1987 2007

Nu

mb

er

of

rad

ii

Rin

g w

idth

in

de

x

Year

Std chronology

Regime shift

Number of radii

EPSlt85







-08

-07

-06

-05

-04

-03

-02

-01

00

01

02

03

04

05

06


Co

rrela

tio

n co

eff

icie

nt

Month and season


-10

-08

-06

-04

-02

00

02

04

06

08

10

12


Co

rrela

tio

n c

oeff

icie

nt

Month








4 Discussion

































5 Conclusions








References































































































4 Discussion

































5 Conclusions








References





















































































































5 Conclusions








References











































































































5 Conclusions








References



































































































5 Conclusions








References

































































































References


























































































































































































Documents

Treeline dynamics with climate change at the central Nepal Himalaya