This article was downloaded by: [Florida Atlantic University]On: 17 November 2014, At: 16:29Publisher: Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954 Registered office: MortimerHouse, 37-41 Mortimer Street, London W1T 3JH, UK

Scandinavian Journal of Forest ResearchPublication details, including instructions for authors and subscription information:http://www.tandfonline.com/loi/sfor20

Changes in nutrient concentrations andnutrient release in decomposing needle litter inmonocultural systems of Pinus contorta and Pinussylvestris—a comparison and synthesisBjörn Berg a & Ryszard Laskowski ba Department of Forest Soils , Swedish University of Agricultural Sciences , P.O. Box7001, Uppsala, S‐750 07, Swedenb Department of Ecosystem Studies , Jagiellonian University , Ingardena 6, Cracow,PL‐30–060, PolandPublished online: 10 Dec 2008.

To cite this article: Björn Berg & Ryszard Laskowski (1997) Changes in nutrient concentrations and nutrient release indecomposing needle litter in monocultural systems of Pinus contorta and Pinus sylvestris—a comparison and synthesis,Scandinavian Journal of Forest Research, 12:2, 113-121, DOI: 10.1080/02827589709355392

To link to this article: http://dx.doi.org/10.1080/02827589709355392

PLEASE SCROLL DOWN FOR ARTICLE

Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”)contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensorsmake no representations or warranties whatsoever as to the accuracy, completeness, or suitability for anypurpose of the Content. Any opinions and views expressed in this publication are the opinions and viewsof the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Contentshould not be relied upon and should be independently verified with primary sources of information.Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs,expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly inconnection with, in relation to or arising out of the use of the Content.

This article may be used for research, teaching, and private study purposes. Any substantial or systematicreproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in anyform to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http://www.tandfonline.com/page/terms-and-conditions

Scand. J. For. Res. 12: 113-121, 1997

Changes in Nutrient Concentrations and Nutrient Release inDecomposing Needle Litter in Monocultural Systems of Pinuscontorta and Pinus sylvestris—a Comparison and Synthesis

BJÖRN BERG1 and RYSZARD LASKOWSKI2

1Department of Forest Soils, P.O. Box 7001, Swedish University of Agricultural Sciences, S-750 07 Uppsala, Sweden, and2Department of Ecosystem Studies, Ingardena 6, Jagiellonian University PL-30-060 Cracow, Poland

Scandinavian Journalof Forest Research

Berg, B.1 and Laskowski, R.2 (1Department of Forest Soils, P.O. Box 7001, Swedish Universityof Agricultural Sciences, S-750 07 Uppsala, Sweden, and 2Department of Ecosystem Studies,Ingardena 6, Jagiellonian University, PL-30-060 Cracow, Poland). Changes in nutrient concen-trations and nutrient release in decomposing needle litter in monocultural systems of Pinuscontorta and Pinus sylvestris—a comparison and synthesis. Received Febr. 12, 1996. AcceptedSept. 29, 1996. Scand. J. For. Res. 12: 113-121, 1997.

Scots pine (Pinus sylvestris) and lodgepole pine (Pinus contorta) needle litters were comparedin terms of nutrient composition and its change during decomposition. Initial nutrientcomposition differed between the species, with lodgepole pine needle litter having significantlyhigher concentrations of P, Mg and Mn. However, no difference was found for concentrationsof N, Ca or K. Increases in concentrations of N, P and K during decomposition weresignificant in both litter types. For Ca the pattern of concentration changes followed aquadratic function as decomposition proceeded. Concentrations of Mg and Mn decreased inlodgepole pine needle litter. In Scots pine litter there was also an initial decrease, but it wasfollowed by an increase in most incubations. For both Mg and Mn, changes in concentrationsduring decomposition differed significantly between species. In the late decomposition stages,concentrations of Mg and Mn became similar in both litter types. Nutrient concentrationsgenerated by the models were compared with those of the humus (F and H) layer in thestands. The model was quite accurate in predicting concentrations of N and P for both speciesand the concentration of Mg for lodgepole pine. By contrast, it was not accurate in predictingconcentrations of Ca and Mn. Nutrient release was estimated for the two species using bothmeasured litterfall data and long-term estimates, and regression models were used to predictconcentration changes. Rates of release of P, Mg and Mn in the lodgepole pine stands werefound to be about twice as high compared with those in Scots pine. Calcium was also releasedto a greater extent although the difference was not significant. Key words: decomposition,humus, mineral nutrients, needle litter, Pinus contorta, Pinus sylvestris.

INTRODUCTION

In decomposing litter, patterns of change in mineralnutrient concentrations vary, depending on the typeof nutrient (Staaf & Berg 1982). Nitrogen (cf. Berg &Staaf 1981), P (cf. Berg & McClaugherty 1989) and K(Laskowski et al. 1995a) appear to have relativelypredictable dynamics. By contrast, no clear patternhas yet been discerned concerning the dynamics ofCa, Mg, and Mn. As decomposition proceeds, con-centrations of N, P and S tend to increase linearly inrelation to accumulated mass loss. In highly decom-posed litter a concentration decrease may occur, ashas been reported for grey alder and white birch leaflitter (Berg & Cortina 1995). Nutrients that are highlymobile, such as K and Mn, and not limiting formicroorganisms, tend to decrease in concentration(Staaf & Berg 1982). However, at low initial concen-

trations of K some increase in its concentration mayoccur (Laskowski et al. 1995a).

Now that exotic coniferous species have been intro-duced into Scandiavia the nutrient composition anddynamics of decomposing needle litter should be ofconsiderable silvicultural interest, because the speciesintroduced may change the nutrient dynamics patternin the forest floor completely. For example, a highconcentration of N in litter may enhance the mass-loss rate initially, but delays decomposition in laterstages (Berg & Ekbohm 1991), thereby indirectlyaffecting the dynamics of soil organic matter as wellas nutrient release.

Plant nutrients are released from litter througheither mechanical leaching or the decomposition ofstructural organic components by soil organisms. Of-ten the latter process is quantitatively the most im-

© 1997 Scandinavian University Press ISSN 0282-7581

Dow

nloa

ded

by [

Flor

ida

Atla

ntic

Uni

vers

ity]

at 1

6:29

17

Nov

embe

r 20

14

114 B. Berg and R. Laskowski Scand. J. For. Res. 12 (1997)

Table 1. List of sites used, their geographical location and some site data

Site

name

Annual mean

Latitude; Altitude precipitation temperaturenumber longitude (m) (mm) (°C) Soil type Species

Kappsjön 17:1

17:2

Anundberget 18:1

Nyhusen

18:2

19: 1

19:2

60°33' N;13°44'E

60°38'N13°37'E

60°35' N;13°34'E

375

400

435

450

450

450

2.8

2.0

1.8

Fine sandy till Lodgepole pine

Scots pine

Sandy till Lodgepole pine

Scots pine

Fine sandy till Lodgepole pine

Scots pine

portant, and the rate at which elements are releasedcould thus be expected to be governed largely bydecomposition rate. However, patterns of releasediffer between elements, and elements differ interms of the strength with which they are bound tothe litter. This is in part a reflection of the natureof chemical bonds that bind elements to the organicmatter. Elements such as Na, K, Mg and Mn, thecontents of which are usually low in structuralcomponents of the litter, are sensitive to initialleaching losses (Staaf 1980). It should be empha-sized that when we use the word "released" there isno implication of a synonymity with "mineraliza-tion". For example, N released from primary litterstructures may be bound to secondary organicmolecules prior to mineralization.

The aim of the present study was to look fordifferences in nutrient concentration dynamics be-tween lodgepole pine (Pinus contorta) and Scotspine (Pinus sylvestris) needle litters. In an attemptto discern a basic pattern of mass loss, chemicalchanges and nutrient dynamics during decomposi-tion, lodgepole pine and Scots pine needle litterswere incubated concurrently in their respectivestands at nearby and very similar sites. All basicdata collected in this study are available in a report(Berg & Lundmark 1985).

In earlier studies, Berg & Lundmark (1987) andBerg & Ekbohm (1993), using basic informationfrom the same study, presented data on the initialchemical composition of newly fallen litter, on theinfluence of lignin on litter mass-loss rates and onfinal decomposition values that may influence thehumus build-up rate.

MATERIALS AND METHODS

Site description

Three sites were used in the study (Table 1). Thereference numbers given in Table 1 are the same asthose used by Berg et al. (1986) and Berg & Lund-mark (1987). At each site two plots were used: onewith a monoculture of lodgepole pine and the otherwith a monoculture of Scots pine. Each site includedthree ground vegetation types: bilberry shrub (Vac-cinium myrtillus), heather (Calluna vulgaris) and cow-berry shrub (Vaccinium vitis-idaea).

Needle litter collection, storage and sample preparation

Local needle litter was sampled on two occasions, i.e.in February 1978 (sites 17 and 18) and in August/September 1978 (all sites). Brown needles from thefalling needle generation were taken at abscission(second sampling) from trees, all of which were lo-cated in an area of less than 40 m x 40 m. The mainlitter-fall period for the two pine species roughlycoincided at both sites. When branches were shakenin connection with collection work, some greenneedles as well as older, partly decomposed, needlesfell on to the spread-out tarpaulins. Both these frac-tions were removed in order to obtain a fractionconsisting of the newly formed needle litter only.Needles were air-dried and stored at — 20°C prior tosample preparation.

Before weighing, the needles were air-dried at roomtemperature to an even moisture level (about 5%-8%). Dry mass was determined after drying at 85°C,and the largest difference in moisture was less than0.5% units of the average (n = 20).

Dow

nloa

ded

by [

Flor

ida

Atla

ntic

Uni

vers

ity]

at 1

6:29

17

Nov

embe

r 20

14

Scand. J. For. Res. 12 (1997) Nutrient concentrations and nutrient release 115

The litter bags, made of terylene net with a meshsize of about 1 mm, measured 8 cm x 8 cm. About0.7 g of needle litter was enclosed in each bag.

Field incubations

The incubation of litter bags was started on twooccasions: in May 1978 (sites 17 and 18) and inNovember 1978 (all sites). Bags were incubated onthe litter (L) layer in 25 randomized blocks (1 m x 1m) in each of six stands (ca 50 m x 50 m). They werefastened to the ground with metal pegs that were 10to 15 cm long.

Sampling was carried out three times annually atall sites for 4 yrs. From each of the 25 blocks onelitter bag was collected at each sampling. Litter bagswere transported directly to the laboratory andcleaned (i.e. all ingrown material was removed). Afterthe remaining needle samples had been dried at 85CC,they were weighed individually and then combined toform one composite sample prior to chemical analy-sis.

Chemical analyses

Samples were ground ( < 1 mm) in a laboratory mill,and the milled samples were analysed for total con-tents of N, P, Ca, Mg, Mn and K. All analyses weremade in duplicate. Nitrogen was determined by asemi-micro Kjeldahl procedure using a flow-injectionanalysis apparatus (Bifok FIA 05, Tecator, Höganäs,Sweden) with gas diffusion and using phenol red asan indicator (Svensson & Anfält 1982). To determinecontents of P, Mg, Ca, Mn and K, samples weredigested for 2 days in a 2.5 : 1 (v/v) mixture of nitricand perchloric acids. The analyses were performed byplasma atomic emission spectrometry ICP-AES (In-strumentation Laboratory IL P-200, Andover, Mas-sachusetts, USA). Ash content was determined byheating at 600°C for 3 h.

Statistical methods

Differences between the Scots pine and lodgepolepine litters in the dynamics of chemical elementsduring decomposition were analysed using regressionanalysis with dummy variables. For the sake of sim-plicity, we chose the quadratic regression model todescribe the relation between accumulated mass lossand the concentration of a particular element. Withthis approach the results of the dummy-variable testwere still interpretable, and in addition, a satisfactoryfit to the empirical data was obtained. In cases wherethe quadratic term was not significant, simple linear

regression was used to further simplify the modelwherever possible.

Comparisons of the dynamics of chemical elementsbetween litters of the two species were made pairwise;i.e. litters from the two stands in the same experimen-tal plot that had been incubated at the same timewere compared. Because few pairwise differenceswere found, we eventually tested for any differencesbetween species in the dynamics of a particular ele-ment irrespective of site and time of incubation.

If the dynamics of a certain nutrient could bedescribed by a linear regression the model used was:

Cx = Bo + BXA + B3D + B4DA

where Cx is the concentration of an element X (mgg"1), A is the accumulated mass loss (%), D is thedummy variable, and B0-B4 are the estimated regres-sion parameters. Thus, the significance of B3 ac-counted for significant differences in the intercept(initial concentration), and the significance of BA

accounted for significant differences in the slope (i.e.the dynamics of the concentration change).

In cases where the quadratic regression was used,we also tested for the difference in the quadratic termof the model (the "shape" of the relation):

Cx = Bo + BXA + B3A2 + B4D + B5DA + B6DA2

using the symbols and interpretations describedabove.

RESULTS AND DISCUSSION

Initial chemical composition of local litter

There were clear differences in chemical compositionbetween the two needle-litter types (Table 2). Onaverage, needles of lodgepole pine had significantlyhigher concentrations of P, Mg and Mn than those ofScots pine. The average initial needle concentrationof P was 0.38 mg g"1 in lodgepole pine and 0.29 mgg"1 in Scots pine. Corresponding figures were 0.96and 0.61 mg g~' for Mg, and 2.44 and 1.58 mg g~'for Mn, respectively. There were no differences inaverage concentrations of N, K, Ca, or ash. In pair-wise comparisons there was one case of a differencein initial concentration of Ca, with the concentrationbeing higher in lodgepole pine litter.

Nutrient concentration changes

At sites 17 and 18 (Table 1) all nutrients (N, P, K,Ca, Mg and Mn) were studied in both incubations,whereas at site 19 only N was followed. This gave a

Dow

nloa

ded

by [

Flor

ida

Atla

ntic

Uni

vers

ity]

at 1

6:29

17

Nov

embe

r 20

14

116 B. Berg and R. Laskowski Scand. J. For. Res. 12 (1997)

Table 2. A comparison of the initial concentrations of the nutrients N, P, Mg, Ca, K and Mn in needle litter fromlodgepole pine (LPP) and Scots pine (SP) grown at the same sitesAverages given with standard deviation; n.d., not determined; n.s., not significant. Sampling no. 1 took place in February1978 and sampling no. 2 in September 1978

Site and species

17, sampling, 1 LPPSP

17, sampling 2, LPPSP

18, sampling 1, LPPSP

18, sampling 2, LPPSP

19, sampling 2, LPPSP

Average: LPPSP

Concentration

N

3.44.14.04.4

3.83.63.74.6

4.24.7

3.8 + 0.34.3 + 0.4

(mg g"1)

P

0.310.230.440.37

0.310.230.460.32

n.d.n.d.

0.38 + 0.080.29 + 0.07

Mg

0.880.451.060.67

0.850.561.060.74

n.d.n.d.

0.96 ±0.110.61+0.13

Ca

6.86.39.15.3

5.626.425.686.91

n.d.n.d.

6.80 + 1.636.23 + 0.68

K

0.400.500.521.38

0.500.380.930.58

n.d.n.d.

0.59 + 0.230.71 + 0.45

Mn

2.191.663.071.43

2.331.482.171.76

n.d.n.d.

2.44 + 0.431.58 + 0.15

total of 10 studies on N dynamics and eight on thedynamics of the other nutrients.

In a first step we regressed the individual litter setsand compared concentration changes pairwise for thepaired stands. In most cases we obtained highly sig-nificant regressions describing changes in nutrientconcentrations during litter decomposition. Therewere five exceptions to this (out of 50 regressions): Pin incubation 2 with Scots pine at site 17 (due to a faroutlier), presumably caused by an analytical error;exclusion of the outlier made the regression signifi-cant at p< 0.005); K in the same incubation (thehigh initial concentration followed by the fast releasecould have rendered the quadratic model inadequate;cf. Laskowski et al. 1995a,è); Mn in incubation 2with lodgepole pine; and Ca and Mn in incubation 2with Scots pine at site 18, in which the regressionswere nearly significant (p = 0.061 and 0.053 respec-tively).

The nutrient-concentration changes in litter of thesame origin, i.e. from Scots pine or lodgepole pine,revealed similar dynamics independently of the incu-bation. As a consequence, we decided to combine alldata for each species and make a general comparisonof nutrient dynamics between species. This revealedthat N-concentration dynamics were virtually thesame in the two types of decomposing litters. Theconcentration of N increased throughout the decom-position period, from an initial average of 4.05 mg

g"1 to 11.55 mg g"1 at approximately 70%-75% ofaccumulated mass loss (Fig. 1). Such increases in Nconcentration during litter decomposition have beencommonly reported (Staaf & Berg 1982, Berg &Cortina 1995, Laskowski et al. 1995a, b) and can beattributed to the demand of soil microorganisms forthis nutrient as well as to the N being bound to thelignin fraction (Berg & Theander 1984).

Although the regression intercept of P differedsignificantly between litter types, the dynamics of Pduring decomposition followed the same linear pat-tern in relation to litter mass loss, giving very similarrates of increase in concentration. Concentrations ofthis nutrient increased in lodgepole pine litter from aninitial 0.38 mg g"1 to a final value of 1.02 mg g"1,and increased in Scots pine litter from 0.29 mg g~' to0.88 mg g-1 (Fig. 1).

The dynamics of Ca followed a unique patternamong the nutrients studied, with a negative X2 curvebeing fitted to the data for each of the species. Nosignificant differences between litter types were found(Table 3). Following an initial increase, a maximumwas reached, and the concentration started to de-crease after approximately 30% of accumulated massloss (Fig. 1). The average concentration of Ca de-creased during decomposition from an initial 6.52 mgg"1 to 4.22 mg g~' at the end of the incubation.

Potassium dynamics were similar in the two littertypes, increasing from 0.65 mg g~' to the final con-

Dow

nloa

ded

by [

Flor

ida

Atla

ntic

Uni

vers

ity]

at 1

6:29

17

Nov

embe

r 20

14

Scand. J. For. Res. 12(1997) Nutrient concentrations and nutrient release 117

GO

co

cj

OO

c

W

5

2

9

6

3

0

intercept: n.s.slope: n.s.

-

_F~=ö%:o?rT

-

N • . '

-

-

20 40 60 80

11

9

7

5

3

~

-o

*

-

oo

O 4.j-r^"~ 0 _ ^ .

" o ° ° +4-

intercept: n.s.slope: n.s.

Ca

o +

o

o

04-

-? ° 4^ . +

°%O

4-

O

0CHOo

Q

4-

+

o

-

-

-

Çp o4*-X4.4°\o \ _

20 40 60 80

1.2

1.0

0.8

0.6

0.4

0.2

0

. intercept: p<0.0001slope: n.s.

-

.9 ^rC^^í_ * * *" +

P

^ " ^ O*"*í ***

-

-

-

20 40 60 80

1.1

0.9

0.7

0.5

0.3

o

"84-

4-

+

4-

- ,

co

\

)

OO

^V ooo \ .

+

Mg

4- &

~ *4-

-

intercept: p<0.0001slope: p<0.0001

0 +

QO'TP'ft0'* "

20 40 60 80

3.2

2.8

2.4

2.0

1.6

1.2

08

o

'o0

4-

*

O

o<h ° °

o o°o

" + - ^ * **" "* - --t

Mno

o.^_^ 0

D O

o<

•"•H-4-

intercept: p<0.0001slope: p<0.005

o

o ° o° ° ++ + ° "

20 40 60 80

Accumulated mass loss (%)Fig. 1. Dynamics of chemical elements in decomposing Scots pine ( + ; dashed curve) and lodgepole pine ( O ; solid curve)needle litter; intercept (Co) significance level (/>) for differences between the two litter types in intercepts of the regression(initial concentrations of the element); slope, significance level (p) for the difference between the two litter types in slopesof the regressions; n.s., not significant.

centration of 1.07 mg g"1 (Fig. 1). As found byLaskowski et al. (1995a, b), K dynamics in freshlyfallen litter depends to a large extent on the initialconcentration of this element. Although K is a mobileelement and is usually leached quickly from decom-posing litter at high initial concentrations (approxi-mately above 1 mg g"1), at low concentrations, suchas those found in this study, its concentration maybegin increasing as soon as the litter starts to decay.

The only two elements with dynamics that clearlydiffered between the two litter types were Mg andMn, which also showed significantly different concen-trations in the initial material. Concentrations of Mgdecreased in lodgepole pine from an initial average of0.96 mg g"1 to a final value of 0.51 mg g"1. Corre-sponding values in Scots pine were 0.61 mg g"1 and0.57 mg g"1. The concentration of Mn in lodgepolepine needle litter decreased from 2.44 mg g~" to 1.76

Dow

nloa

ded

by [

Flor

ida

Atla

ntic

Uni

vers

ity]

at 1

6:29

17

Nov

embe

r 20

14

118 B. Berg and R. Laskowski Scand. J. For. Res. 12 (1997)

Table 3. Regression analysis for the dynamics of nutrient concentration during decomposition of Scots pine (SP)and lodgepole pine (LPP) needle litter

Data from three sites were combined. The parameters shown relate to the model: Cx = Bo + BjA + B^A2 + BtD + B5DA+ B6DA2. Significance levels of the regressions: *, p < 0.05; **, p < 0.001; ***, p < 0.0001

Regression parameters and fit Differences between Scots and lodepole pine

Nutrient

N

P

Mg

Ca

K

Mn

Species

LPPSP

LPPSP

LPPSP

LPPSP

LPPSP

LPPSP

3.624.08

0.310.24

1.020.64

6.616.01

0.420.60

2.581.65

B,

0.0180.004

0.00980.0093

-0.013-0.011

0.100.11

0.0240.012

-0.013-0.022

B3

0.00130.0015

n.s.n.s.

0.000080.00013

-0.0018-0.0019

-0.00016n.s.

n.s.0.00025

•^adj

0.90***0.91***

0.85***0.80***

0.78***0.34**

0.46***0.64***

0.66***0.44***

0.36***0.14*

* 4

n.s.

p< 0.0001

p< 0.0001

n.s.

n.s.

p< 0.0001

n.s.

n.s.

p< 0.0001

n.s.

n.s.

n.s.

n.s.

n.s.

p < 0.005

mg g ', whereas in Scots pine it remained almostconstant, with an average initial concentration of 1.58mg g~' and a final concentration of 1.56 mg g"1. Still,the quadratic regression describing Mn dynamics inScots pine litter was significant at p < 0.05 and ex-plained 14% of the total variability in Mn concentra-tion (Fig. 1). These two elements, which showedsignificant differences in the slope and shape of theirdynamics curves during decomposition, were also thetwo elements differing most in initial concentrations(Table 2). However, at approximately 70% of accu-mulated mass loss, the two elements reached similarconcentrations in both litter types. This suggests thatthe differences found in the dynamics of these twonutrients between litter types can be ascribed to dif-ferent initial concentrations rather than to differencesin species-specific phenomena.

Comparison with humus

Because the litters had reached slightly different accu-mulated mass losses by the end of the experiment, weused the calculated regression equations to estimatemore comparable values of concentrations of chemi-cal elements at late stages, namely at 70% (C70), 80%(C80) and 90% (C90) accumulated mass loss. Theresults obtained indicate clearly that at these latestages of decomposition the chemical compositions ofthe two litters become more similar (Table 4). This

would mean that the humus from the two speciescould have similar compositions with regard to thesenutrients. However, when comparing the very samesets of litter, namely those incubated at sites 17 and18, Berg & Ekbohm (1993) found that the decompo-sition reached limit values. In other words, at acertain mass loss decomposition rate became so low itwas no longer measureable. The mass loss values usedallowed these limit values to be estimated accurately.The average asymptotic value calculated for decom-position was 82.7% for Scots pine needle litter and94.1% for the lodgepole pine litter. The test was runon each incubated pair of litter as well as on thewhole material, and in all cases the differences weresignificant (Berg & Ekbohm 1993). This suggests thatthe needle litter of lodgepole pine would be decom-posed almost completely (only 6% remaining),whereas for Scots pine there would be a residue ofabout 17%. We can assume that for up to about 80%mass loss the chemical composition estimated (Table4) was similar for the two species. Furthermore, itseems likely that the composition of Scots pine litterwould stabilize at this mass-loss level, whereas thelitter of lodgepole pine would continue decomposingwith some changes in litter chemical composition.Thus, it can be concluded that for Scots pine litterC80 gives a good estimate of the chemical composi-tion of humus in the Scots pine stand, whereas for

Dow

nloa

ded

by [

Flor

ida

Atla

ntic

Uni

vers

ity]

at 1

6:29

17

Nov

embe

r 20

14

Scand. J. For. Res. 12(1997) Nutrient concentrations and nutrient release 119

Table 4. Estimated concentrations of nutrients for decomposing lodgepole pine and Scots pine needle litter at 70%(C70), 80% (Cso) and 90% (C90) accumulated mass loss

The values were calculated using the best-fit regressions and the whole data set. The humus data are in part from Laskowski& Berg (1993)

Nutrient

N

P

Mg

Ca

K

Mn

Species

Lodgepole pineScots pine

Lodgepole pineScots pine

Lodgepole pineScots pine

Lodgepole pineScots pine

Lodgepole pineScots pine

Lodgepole pineScots pine

Í-70

11.311.4

1.010.89

0.480.50

4.734.54

1.281.25

1.571.35

13.413.7

1.120.98

0.460.59

2.992.81

1.281.31

1.351.51

Cgo

15.816.2

1.231.08

0.460.70

0.880.70

1.241.36

1.101.72

Humus

13.213.7

0.920.87

0.3880.374

2.503.00

0.830.83

0.410.44

lodgepole pine C90 probably would give a betterestimate. We should emphasize, however, that theestimated C90 values are based on a substantial ex-trapolation from the regression model, which makesthem less reliable than the C80 and C70 values. Forthis reason we compared the chemical compositionso.f the needle litters with those of the humus in bothtypes of stands (cf. Laskowski & Berg 1993). Thesecomparisons revealed that some relatively good pre-dictions of the humus composition were made. Thusfor Scots pine good agreement was obtained betweenC80 and measured values for N and P, and acceptableagreement was obtained for Mg, Ca and K. For Mnthere was a considerable difference between predictedand measured values at Cso for which no explanationcan be offered. For lodgepole pine, the agreementbetween C90 and measured values for N and P con-centrations was quite good, but not as good as forScots pine C80 values. Also, the value for K wasacceptable. However, for Mg and Ca there wereconsiderable deviations. For Ca, as can be seen fromthe strong difference in C80 and C90 values, the slopeof the line is very steep in this interval. The measuredvalue would fit very well with that at a mass loss ofabout 87% and would deviate relatively little from alimit value of 82.7% mass loss. For the deviationbetween measured and estimated for Mn concentra-tion we do not have a good explanation.

Nutrient release

To estimate the relative release of nutrients we usedregression equations to compare the initial amount inthe fresh litter with amounts estimated at 80% massloss. We can see that release rates were highest forMg, Ca and Mn, for which 80 to 91% of the initialamounts were released (Table 5). Nitrogen and Pwere released to a clearly lower extent (30-41%), andK came in between (56-63%). In general, up to 80%litter mass loss the lodgepole pine needle litter re-leased more P, Mg, Mn and Ca, whereas the Scotspine needle litter released more N and K.

Using the differences in chemical compositionnoted and the needle litterfall values of Lundmark etal. (1982) of 1235 and 970 kg ha"1 yr~' for lodgepolepine and Scots pine respectively, we compared theannual amounts of nutrients released on a per hectarebasis, emphasizing those nutrients for which therehad been significant differences initially and in theestimates, namely P, Mg and Mn (Table 3). For Pthere should be annual additions from needle litter of457 and 252 g ha"1 from lodgepole pine and Scotspine respectively. Thus the amount released fromlodgepole pine litter was about twice that releasedfrom Scots pine litter. For a long-term estimate weassume that litter mass-loss rates are similar (Berg &Lundmark 1987) and that the same amounts of P as

Dow

nloa

ded

by [

Flor

ida

Atla

ntic

Uni

vers

ity]

at 1

6:29

17

Nov

embe

r 20

14

120 B. Berg and R. Laskowski Scand. J. For. Res. 12 (1997)

Table 5. Comparison of initial concentrations of nutrients in lodgepole pine (LPP) and Scots pine (SP) needlelitter and that at a litter mass loss of 80%

A comparison was also made between the annual amounts of nutrients released per hectare from litter up to 80% mass lossusing actually measured litterfall values (annual release from measured litterfall—ARML). For comparison relative valuesare given assuming this difference in accumulaterd litterfall over a stand age (AF) and assuming equal litterfall betweenspecies (EF) over a stand age

Species

LPPSPLPPSPLPPSPLPPSPLPPSPLPPSP

Nutrient

NNPPMgMgCaCaKKMnMn

Initialconcentration(mg g"1)

3.84.30.380.290.960.616.806.230.590.712.441.58

(mg g"1)

13.413.71.120.980.460.592.992.811.281.311.351.51

Nutrient

%

29.536.341.132.490.480.791.279.956.663.188.980.9

released

mg (g initiallitter)"1

1.121.560.1560.0940.8680.4986.204.980.3340.4482.171.278

AMRL(kg ha"1 yr"1)

1.381.510.1930.0911.0720.4837.6574.830.4120.4352.681.24

Comparativeamounts over astand

AF

9010021010022010016010090

100216100

age

EF

7010017010017010012510090

100170100

above are released per unit litter, then the nutrientcirculation in a 100-yr period should be about 20 kgha"1 higher in a lodgepole pine stand.

The corresponding figures for Mg were 1200 g and560 g ha"1 yr"1 for lodgepole pine and Scots pine,respectively, which means that in this case as well,about twice as much Mg would be released fromlodgepole pine litter. For Mn the annual figures were3090 and 1640 g ha"1 respectively, again indicatingthat about double the amount was released in thelodgepole pine forest. For N, Ca, and K there wereno significant differences in initial concentration. Wecan therefore assume that the circulation would beincreased in proportion to the litterfall; i.e. it wouldbe about 25% higher in the lodgepole pine forest.

The results of this comparison should be inter-preted with caution, however, because the litterfallvalues were measured for just a few years. Morever,measurements were made at an age when stronggrowth resulted in a difference in growth rate be-tween the stands, which may later disappear. How-ever, if we assume that the accumulated litterfall overa stand age is similar in two stands, then the differ-ence observed would still hold, although it would beless pronounced.

These estimates were made using nutrient data for80% litter mass loss. Berg & Ekbohm (1993) esti-

mated that Scots pine needle litter would reach a limitvalue of 82.7%; thus the estimates may be realistic forthis species. On the other hand, with the limit valueof 94.1% for lodgepole pine it is reasonable to assumethat the values presented for this species are anunderestimate. This would have strengthened the dif-ference between species in terms of nutrient concen-tration.

The increased circulation of a critical nutrient suchas P might affect the ground vegetation. However, acomparison of the frequencies of herb species andbilberry (Vaccinium myrtillus) which was the domi-nant shrub, did not reveal any clear differences be-tween stands that could be ascribed to a specificnutrient. It seems likely that the higher amount of Padded to the ground is used by the lodgepole pinesthemselves, considering that this species P demandwas reported to be relatively higher than that of Scotspine (van Driessche & Wareing 1966). It should alsobe kept in mind that a change in the understoreymight go undetected. The same goes for the othernutrients.

ACKNOWLEDGEMENTS

We are most indebted to the skilful technical as-sistance of Mrs Solveig Geidnert. This work

Dow

nloa

ded

by [

Flor

ida

Atla

ntic

Uni

vers

ity]

at 1

6:29

17

Nov

embe

r 20

14

Scand. J. For. Res. 12 (1997) Nutrient concentrations and nutrient release 121

was supported by the Swedish Board of Environ-mental Protection, through the Project VAMOS inthe EEC research program "Environment" (No.EV5VCT920141).

REFERENCES

Berg, B. & Cortina, J. 1995. Nutrient dynamics in someleaf and needle litter types of different chemical compo-sition in a Scots pine forest. Scand. J. For. Res. 10:1-11.

Berg, B. & Ekbohm, G. 1991. Litter mass-loss rates anddecomposition patterns in some needle and leaf littertypes. Long-term decomposition in a Scots pine forestVII. Can. J. Bot. 69: 1449-1456.

Berg, B. & Ekbohm, G. 1993. Decomposing needle litter inLodgepole pine (Pinus contorta) and Scots pine (Pinussylvestris) monocultural systems. Is there a maximummass loss? Scand. J. For. Res. 8: 457-465.

Berg, B. & Lundmark, J.-E. 1985. Decomposition of needleand root litter in lodgepole pine and Scots pine mono-cultural systems. Dept. For. Ecol. For. Soils, SwedishUniv. Agric. Sci. Research Notes No. 53, 74 pp. ISSN0348-3398.

Berg, B. & Lundmark, J.-E. 1987. Decomposition ofneedle litter in lodgepole pine and Scots pine monocul-tural systems—a comparison. Scand. J. For. Res. 2:3-12.

Berg, B. & McClaugherty, C. 1989. Nitrogen and phospho-rus release from decomposing litter in relation to thedisappearance of lignin. Can. J. Bot. 67: 1148-1156.

Berg, B. & Staaf, H. 1981. Leaching, accumulation andrelease of nitrogen from decomposing forest litter. InTerrestrial Nitrogen Cycles. Processes, EcosystemStrategies and Management Impacts. Ecol. Bull. (Stock-holm) 33: 163-178.

Berg, B. & Theander, O. 1984. The dynamics of some

nitrogen fractions in decomposing Scots pine needles.Pedobiologia 27: 161-167.

Berg, B., Ewertsson, A., Holm, B., Jansson, P.-E., Koi-vuoja, S., Meentemeyer, V., Nyman, P., Ferenzi, J.,Staaf, H. & Staaf, I. 1986. Data on needle litter decom-position and soil climate as well as site characteristicsfor some coniferous forest sites. 1st edition. Departmentof Ecology and Environmental Research. Swedish Uni-versity of Agricultural Sciences. Report No. 22, 386 pp.ISSN 0348-422X.

Laskowski, R. & Berg, B. 1993. Dynamics of some mineralnutrients and heavy metals in decomposing forest litter.Scand. J. For. Res. 8: 446-456.

Laskowski, R., Berg, B., Johansson, M. & McClaugherty,C. 1995a. Release pattern for potassium from decom-posing forest leaf litter. Long-term decomposition in aScots pine forest X. Can. J. Bot. 73: 2019-2027.

Laskowski, R., Niklinska, M. & Maryañski M. 1995ft. Thedynamics of chemical elements in forest litter. Ecology76: 1393-1406.

Lundmark, J-E., Berg, B. & Nilsson, Å. 1982. The influenceof Pinus contorta on the soil and ground vegetation incomparison with Pinus sylvestris. Sver. Skogsvårdsförb.Tidskr. 1-2: 43-48. (In Swedish with English sum-mary.)

Staaf, H. 1980. Release of plant nutrients from decompos-ing leaf litter in a South Swedish beech forest. HolarcticEcol. 3: 129-136.

Staaf, H. & Berg, B. 1982. Accumulation and release ofplant nutrients in decomposing Scots pine needle litter.Long-term decomposition in a Scots pine forest II. Can.J. Bot. 60: 1561-1568.

Svensson, G. & Anfält, T. 1982. Rapid determination ofammonia in whole blood and plasma using flow injec-tion analysis. Clin. Chim. Acta 119: 7-14.

Van Dreissche, R. & Wareing, P. F. 1966. Nutrient supply,dry matter production and nutrient uptake of forest treeseedlings. Annales of Botany 30: 659-672.

Dow

nloa

ded

by [

Flor

ida

Atla

ntic

Uni

vers

ity]

at 1

6:29

17

Nov

embe

r 20

14