RESEARCH EXTENESION NOTE NO. 7 · This sampling approach was necessary as the height of the trees did not allow for the use of a ladder or extending pole pruner. Four field assistants

RESEARCH EXTENESION NOTE

NO. 7 – November 2012

Foliar nutrient concentrations and potential

limitations of white spruce (Picea glauca (Moench)

Voss) in Yukon, Canada.

By

Alyson Watt, Arthur L. Fredeen &

Paul T. Sanborn

Watt, Fredeen & Sanborn Foliar nutrient concentrations and limitations of white spruce ii

Alyson Watt is a Masters student in the Natural Resources and Environmental

Studies Graduate Program at the University of Northern British Columbia, Prince

George, B.C., Canada. Dr. Art Fredeen and Dr. Paul Sanborn are faculty in the

Ecosystem Science and Management Program and members of the Natural

Resources and Environmental Studies Institute, University of Northern British

Columbia, Prince George, B.C., Canada.

The correct citation for this paper is:

Watt, A., Fredeen, A. L. and Sanborn, P. T. 2012. Foliar nutrient concentrations and potential limitations of white spruce (Picea glauca (Moench) Voss) in Yukon, Canada. Natural Resources and Environmental Studies Institute Research Extension Note No. 7, University of Northern British Columbia, Prince George, B.C., Canada.

This paper can be downloaded without charge from

http://www.unbc.ca/nres/research_extension_notes.html

http://www.unbc.ca/nres/research_extension_notes.html

iii Research Extension Note No.7 Nov 2012

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1 Research Extension Note No.7 Nov 2012

CONTENTS

Abstract ........................................................................................................................................... 2

Introduction ..................................................................................................................................... 3

Methods........................................................................................................................................... 3

Study Sites ...................................................................................................................................3

Foliage sampling and chemical analysis ......................................................................................4

Data analysis ................................................................................................................................6

Results and Discussion ................................................................................................................... 6

Macronutrients .............................................................................................................................6

Micronutrients ..............................................................................................................................9

Conclusion .................................................................................................................................... 11

References ..................................................................................................................................... 13

.

Watt, Fredeen & Sanborn Foliar nutrient concentrations and limitations of white spruce 2

Abstract

Although nutrient deficiencies are not

uncommon in forests across the north, little is

known about these limitations in the Yukon,

and even less about how these limitations have

been and/or will be affected by climate. To

address existing edaphic limitations to forests

in the Yukon, an investigation of the nutrient

concentrations of white spruce (Picea glauca

(Moench) Voss) foliage was undertaken

throughout various regions of Yukon in 2009.

By comparing individual nutrient

concentrations to critical values and reviewing

nutrient ratios, the results identified nitrogen

(N) as being commonly severely deficient.

Phosphorus (P) and sulphur (S) were also

commonly deficient, whereas magnesium

(Mg) and potassium (K) were mostly adequate

with few reports of slight deficiency levels. In

contrast, calcium (Ca) was adequate at all

locations. Of the micronutrients, zinc (Zn) and

manganese (Mn) were the only elements in

adequate supply at all sites while slight to

moderate deficiencies were commonly

indicated for all other micronutrients across

the study area. Nutrient limitations may

ultimately restrict the growth response of

white spruce to climate changes and/or

increasing atmospheric CO2.


Introduction

Research has suggested that boreal forests

may be able to take advantage of the

increasing CO2 concentrations through

enhanced photosynthesis (Chapin 1991a,

Perry 1994, Reich et al. 2006). However, the

ability of plants to capitalize on increased CO2

concentrations in the atmosphere will depend

on nutrient availability (Perry 1994, Reich et

al. 2006). While nutrient concentrations are a

function of soil attributes such as active layer

depth and weathering rate of parent material,

soil richness is also dictated by environmental

stresses (Chapin 1991b), e.g., when soil

temperatures are below 0°C, soil microbial

activity decreases restricting nutrient turn-over

rates (Jefferies et al. 2010). The ability of a

tree to photosynthesize is affected by the

nutrients it has available to it (Miller 1995)

and when nutrient availability is limiting,

growth rates are limited (Kozlowski and

Pallardy 1997).

Information about the nutrient status of stands

and its effects on tree growth is important not

only to improve understanding of forest

productivity, but also for forest managers who

are making management decisions (Wang and

Klinka 1997, Yarie and Van Cleve 2010). A

common method for evaluating tree nutritional

status is measuring foliar nutrient

concentrations (Ballard and Carter 1986).

Foliar sampling and elemental analysis are a

relatively simple way to investigate nutritional

health of trees and identify severe deficiencies

(Carter 1992). The purpose of this

exploratory study was to investigate the

current foliar nutrient status of white spruce

(Picea glauca (Moench) Voss) trees located in

central and southern Yukon in order to gain

insight into the potential for growth

limitations in this species.

Methods

Study Sites

Twenty sites were sampled throughout the

Boreal Cordillera eco-zone of Yukon (Figure

1). The sites were all located at mesic

locations with southern exposures. Summary

characteristics of the site locations are

provided in Table 1. The Boreal Cordillera

eco-zone is found in the midsection of the

western cordilleran system of Canada and

extends from northern British Columbia into

the southern and central Yukon. It is

composed of mountains, valleys and lowlands

and experiences moderating effects

influencing the climate because of the close

proximity to the Pacific Ocean. Mean annual

temperatures range from 1.5-5°C, winters are

long and cold, while summers are short and

warm. This climate allows for widespread

permafrost in alpine and northern areas. The

forests grow only in the valleys and lowlands

and are dominated by white spruce; sub-

dominant species include lodgepole pine

(Pinus contorta Dougl. ex Loud. var. latifolia

Engelm), subalpine fir (Abies lasiocarpa

(Hook.) Nutt.), trembling aspen (Populus

tremuloides Michx.), black spruce (Picea

mariana (Mill.) BSP), balsam poplar (Populus

balsamifera L.), and paper birch (Betula

papyrifera Marsh.) (Smith et al. 2004).


Foliage sampling and chemical

analysis

All foliar sampling procedures were

conducted in accordance with Brockley

(2001). Foliar samples were collected in mid

to late August in 2009, after trees had gone

into dormancy. Four dominant trees were

selected at each site to be sampled. For

nutrient assessment work often more trees

(10+) are sampled at each site. The intention

of this work, however, was to conduct an

initial investigation of available nutrients

throughout white spruce stands. Therefore

emphasis was put on sampling more sites

instead of more trees per site. Budget and time

were additional constraints in this study.

Foliage from each of the 4 trees at each site

were sampled using a shotgun (Winchester

Marine 12 gauge with 12 gauge - 2 ¾ inch - 1

1/8oz, 4 shot). This sampling approach was

necessary as the height of the trees did not

allow for the use of a ladder or extending pole

pruner. Four field assistants observed the

impacts of the shot, as well as the foliage

falling to the ground, assuring that the samples

were taken from the top third of the canopy of

the intended tree. Multiple samples were

collected from each tree to create a composite

Figure 1. Spatial distribution of the 2009 white spruce foliar nutrient sampling sites across

the eco-regions of the Boreal Cordillera eco-zone in Yukon, Canada.


sample from the current year foliage. The

sampled foliage was placed directly into pre-

labelled sealable plastic bags that were stored

in a cooler on ice (1-5°C).

In the laboratory, samples were dried in a

drying oven at 70°C for a 24-hour period or

until samples were oven-dried, needles

separated from twigs and then needles ground

to a fine powder using a stainless steel electric

Table 1: Location, elevation and eco-region of white spruce foliar nutrient research plots within Yukon, Canada.

Site Location Latitude Longitude Elevation (m) Eco-region1

Teslin 1 60o 17' 21.0" N 132

o58'54" W 745 YSL

Jake1 60o 20' 43.2" N 134

o2'3.7" W 755 YSL

Teslin 3 60o 7' 34.706" N 132

o35'53.6" W 761 YSL

Ranch 1 60o 4' 29.0" N 130

o53'6.3" W 1030 LB

Ranch 3 60o 10' 11.0" N 130

o9'44.6" W 847 LB

Junction 1 60o 1' 44.5" N 129

o0'13.3" W 665 LB

Dempster 64o14’12.8” N 138

o31’33.7” W 739 YPN

Dawson 2 64o04’10.4” N 139

o30’54.9” W 715 KP

Dawson 4 64o07’27.7” N 139

o42’51.5” W 1072 KP

Dawson 5 64o09’08.7” N 139

o45’58.6” W 1140 KP

Klondike 1 63o57’27.0” N 138

o41’37.1” W 460 KP

Klondike 2 63o55’32.7” N 138

o32’50.1” W 538 KP

Klondike 3 63o35’11.9” N 137

o28’22.8” W 454 YPN

Keno 2 63o56’41.9” N 135

o23’04.2” W 870 YPN

Duncan 1 63o44’15.5” N 135

o50’38.7” W 665 YPN

Mayo 2 63o35’27.2” N 136

o00’18.2” W 562 YPN

Stewart 2 63o25’39.2” N 136

o30’23.3” W 503 YPN

Pelly 1 63o00’20.6” N 136

o29’08.6” W 688 YPC

Twin 1 61o50’19.9” N 136

o05’37.1” W 590 YPC

Fox 2 61o13’24.2” N 135

o25’59.0” W 810 YPC

1 YSL-Yukon Southern Lakes, LB-Liard Basin, YPN-Yukon Plateau North, KP- Klondike Plateau,

YPC-Yukon Plateau Central


coffee grinder. Ground samples were sent to

the Ministry of Forest and Range lab in

Victoria, BC, Canada, for analysis of total

carbon (C), nitrogen (N), phosphorus (P),

potassium (K), calcium (Ca), zinc (Zn), iron

(Fe), magnesium (Mg), boron (B), manganese

(Mn), aluminum (Al), copper (Cu), sulphur

(S), and sulphate-S (SO4-S). Foliage samples

were digested in a very strong oxidizing acid

mix in a closed vessel microwave digestion

process (Questron QLab 6000) for analysis of

P, K, Ca, Mg, Zn, Fe, Mn, B, Al, and Cu

(Kalra and Maynard 1991). Nutrients were

analyzed using a Teledyne/Leeman Prodigy

dual-view Inductively Coupled Plasma (ICP)

spectrometer. For the processing of total C, N

and S, ground samples were combusted in tin

capsules. This process converted all elements

of interest into oxide gases that were measured

using gas chromatography and mass

spectrometry (Fisons NA-1500, Carlo-Erba;

Kalra and Maynard 1991). SO4-S was

extracted by boiling ground material in 0.01M

HCl, and quantified using a Waters Ion

Chromatography System with a Grace/Vydac

302IC column (Lambert (1989; as outlined in

Kalra and Maynard 1991).

Data analysis

Assessment of foliar concentrations involved

relating them to published critical values,

defined as concentrations minimally adequate

for growth of a given tree species (Brockley

2001). The nutrient status of white spruce

trees sampled throughout Yukon were

analysed using critical values for white spruce

from Carter (1992), except for S and SO4-S

where values from Ballard and Carter (1986)

were used. The diagnosis of each essential

element was averaged at each site before

being compared to the critical value. Foliar

nutrient concentrations are expressed as

percent (macronutrients) or ppm

(micronutrients) concentrations on an oven

dry mass basis.

Critical ranges are ratios that are used as a

diagnostic tool to investigate the interactions

between nutrients (i.e., N/S or N/P) and help

to further identify which, if either, of the

nutrients are in deficient concentrations at a

site (Koerselman and Meuleman 1996, Zhang

et al. 2010). The critical ranges of these

nutrient ratios were also compared to values

from Ballard and Carter (1986). The

classification scheme for these critical ranges

is the same: deficient, possibly deficient and

adequate.

Results and Discussion

Macronutrients

The prevalence of macronutrient deficiencies

in white spruce across all 20 sites in Yukon

are listed in Table 2 and illustrated in Figure

2. Eighteen sites showed severe N deficiency

(<1.05%) and two sites moderate N deficiency

(1.05-1.25%). Nitrogen deficiencies in boreal

forests are common (Boonstra et al. 2008),

thus finding 18 of 20 sites N deficient was not

unexpected. Phosphorus was adequate at only

site, but was less deficient overall than N, with

19 sites exhibiting moderate to slight

deficiencies. White spruce has been

considered to be a more nutrient demanding

conifer and requires higher concentrations of

P than other boreal conifers (Wilde 1966). In

previous work, widespread P deficiencies in


white spruce have been observed in eastern

Canada (Quesnel et al. 2006).

There are several probable explanations why

some sites reported deficient concentrations of

P. Phosphorus leaching may have occurred if

sites were located on old weathered soils or in

areas with coarse or sandy soils (Alfaro et al.

2004). Weathered soils may be the cause of

deficiencies found in the sites (Dawson 2,

Dawson 4, Dawson 5, Klondike 1 and

Klondike 2) located in the Klondike plateau

eco-region. Areas of this eco-region known as

the Beringia have not experienced recent

glaciation, which has allowed soils to weather

to a greater degree than surrounding glaciated

soils (Bond and Sanborn 2006). Another

potential explanation may lie in decreased soil

microbial activity (Jefferies et al. 2010) and/or

decreased mineral P weathering rates in cold

and/or drier soils with short growing seasons

(Mengel and Kirby 2001). In either case, will

continued global warming induced

enhancement of tree growth outpace any

associated improvements in soil P

availability? Further work is needed to

address this and all other potential tree

nutrient limitations in Yukon in the face of

continued warming.

N and P are commonly limiting nutrients for

plants, as they are required in large amounts

(both are macronutrients) and are very

important for plant growth and development

(Chapin et al. 1986, Koerselman and

Meuleman 1996, Zhang et al. 2010). The ratio

of N/P is also an important diagnostic tool

when investigating the relative importance of

these nutrient limitations (Koerselman and

Meuleman 1996, Zhang et al. 2010). For

example, the ratio between N and P is often a

better tool for identifying their relative

limitations of N or P to plant growth

(Koerselman and Meuleman 1996). The N/P

Table 2: Summary of the macronutrients analysis from 80 white spruce trees sampled across 20 sites throughout Yukon, Canada. The concentrations were compared with critical values from Carter 1992 with exception of S-ICP (Inductive coupled plasma is a spectrometer used in laboratories to determine total S in an extract) and SO4-S, which are compared to critical values from Ballard and Carter (1986). Ballard and Carter (1986) do not classify nutrient levels as severe, moderate, slight and adequate, therefore, severe for S and SO4-S is merely indicating deficiency versus adequate concentrations.

Foliar Nutrient

Macronutrient Concentrations (%)

No. of plots diagnosed as deficient

Range Mean (SD) Severe Moderately Slight Adequate

N 0.569-1.304 0.835 (0.146) 18 2 0 0

P 0.088-0.202 0.134 (0.022) 0 14 5 1

K 0.307-1.004 0.520 (0.120) 0 0 5 15

Ca 0.234-1.096 0.522 (0.163) 0 0 0 20

Mg 0.109-0.128 0.098 (0.019) 0 4 16 0

S-ICP 0.036-0.086 0.061 (0.011) 19 0 0 1 SO4-S

0.300-154.400 73.770 (39.567) 9 0 0 11


ratios from these data suggest that none of

these sites were experiencing a true P

limitation (Figure 3) or that because of the

limiting N, the nutrients are in balance. For

example, if N were to become more available

in these areas (with improved environmental

conditions and warmer soils) it is unknown if

there would be enough P in the soils to

maintain a balance.

Of the cationic macronutrients, Mg was the

most deficient; slightly (0.08-0.12%, 16 sites)

or moderately (0.05-0.08%, 4 sites) at all of

the sites. K levels were mostly found to be

adequate (>0.50%, 15 sites) with a minority of

sites showing slight deficiencies (0.30-0.50%,

5 sites). By contrast, Ca was the only

macronutrient present in adequate amounts at

every location with concentrations ranging

from 0.23-1.10%.

S concentrations were identified as deficient at

all except one site. These results are

comparable to findings of Wang and Klinka

(1997) where similar macronutrient

deficiencies occurred in hybrid spruce in the

Figure 2. Map showing the reported macro-nutrient concentrations from the foliage of white spruce trees at each research site in Yukon, Canada. The nutrients read from left to right at all sites; N, P, K, Ca and Mg. Circles of various sizes and colors indicate foliar nutrient concentrations ranked according to the ‘critical level’ classification scheme for the macro-nutrients: severely deficient, moderately deficient, possible deficient or adequate, according to Carter (1992).


Figure 3. Summary of the P and N/P ratio from the white spruce foliage sampled from 20 research sites throughout Yukon, Canada. Circle size is as defined in Figure 2.

Sub-Boreal Spruce (SBS) bio-geoclimatic

zone of BC. These S results are also

consistent with widespread S deficiencies

identified in lodgepole pine foliage within the

SBS zone (Sanborn et al. 2005). These

similarities are potentially highlighting a trend

of limiting S concentrations occurring from

central BC to southern and central Yukon.

There was some discrepancy between total S,

N/S ratio and SO4-S determinations of S

deficiency (Figure 4). Although total S levels

indicated S-deficiencies occurred in 19 of 20

sites, N/S ratios suggested that only 11 sites

were S-deficient and SO4-S analyses indicated

9 of the 20 sites were S-deficient. All

analyses indicated that Teslin 3, Klondike 3

and Dawson 2 sites had the most deficient

levels of S and Duncan 1 was uniformly S-

sufficient. Research has identified SO4-S as

being a good indicator of N and S deficiencies

within trees and it is accepted that if SO4-S

concentrations are insufficient, it will affect

the ability of a tree to acquire N (Brockley

2000, Sanborn et al. 2005). This suggests that

sites Teslin 3, Klondike 2 and Dawson 2,

which had severely deficient levels of SO4-S,

will be predisposed to N-deficiency.

Micronutrients

Micro-nutrient deficiencies are depicted in

Table 3 and demonstrate variable levels of

deficiency across the sites (Figure 5). B was

likely deficient (<5ppm, 19 sites) at all


locations except the Dawson 5 site where

possibly deficiency (5-12 ppm, 1 site) was

reported. Because the intake of B is reliant on

mass flow and water availability in the soil

horizon (Mengel and Kirby 2001), these B

deficiencies might be attributed to well

drained soils and/or low precipitation or

periodic drought. All sites showed a possible

moderate deficiency (1-2 ppm, 5 sites) and

possible deficiency in Cu (2-3 ppm, 15 sites).

Only 1 site had an adequate level of Fe (>50

ppm) with the remaining sites showing

possible (25-50 ppm) and likely deficiency

(<25 ppm) levels at 13 and 6 sites

respectively. Iron deficiencies are normally

associated with calcareous soils because it

becomes insoluble at higher soil pH levels

(Van Dijk and Bienfait 1993, Mengel and

Kirby 2001). The variability and reported

deficiencies of Fe for these sites in the boreal

forest, where soils normally have lower pH’s

(Ste-Marie and Paré 1999), were not expected.

Research involving Fe and white spruce is

limited; one study by Ballard (1985) identified

Fe deficiency in white spruce that were

located in cut blocks that had been burned for

site preparation before the seedlings were

planted. Adequate levels of Zn and Mn were

identified at all 20 sites with concentrations of

Zn and Mn ranging from 21.5-76.3 ppm and

Figure 4. Summary of the S, SO4-S (SS) and N/S ratios diagnosed from white spruce foliage sampled from 20 research sites throughout Yukon, Canada. Circle size is as defined in Figure 2, but the threshold used were deficient, possibly deficient, and adequate (Ballard and Carter 1986).


33.5-731.3 ppm respectively. Zinc

deficiencies, like Fe, arise with increasing soil

pH’s (Mengel and Kirby 2001), which is

likely why there were no Zn deficiencies

reported from any of the sites.

Conclusion

Seasonal patterns of temperature and

precipitation are changing over this northern

landscape. The predictions of continued and

amplified warming and drying at these

latitudes are expected to impose significant

impacts on these ecosystems (Spittlehouse and

Stewart 2003, IPCC 2007). Both positive

(enhanced growth) and negative impacts

(increased natural disturbance occurrence and

severity) are expected to occur (Nitschke

2009). The prediction that boreal forests will

grow better under warmer and drier climates

(Chapin 1991a, Perry 1994, Reich et al. 2006)

could be questioned given the high potential

for nutrient limitations indicated by this study.

With the exception of Ca and K, all of the

macronutrients were found in deficient levels

Figure 5. Map showing the reported micro-nutrient concentrations identified from the foliage of white spruce at each research site in the Yukon, Canada. The nutrients read from left to right at all sites; B, Cu, Fe, Zn and Mn. Circle size is as in Figure 2 but micro nutrients the thresholds were: severe deficiency, possible moderate deficiency, possible deficiency or no deficiency (adequate).


at most of the sites. Nitrogen and S, both of

which are important macronutrients for

protein synthesis and photosynthesis

exclusively fell in the severely deficient and

deficient range at all sites sampled across

Yukon. Phosphorus, a major macronutrient,

and B and Fe, major micro-nutrients, all

exhibited lower deficiencies, but are still

possibly in inadequate supply at many sites.

Knowing that nutrient concentrations and

availability are one of the most important

resources that will help to define plant

communities and productivity (Koerselman

and Meuleman 1996), the common nutrient

deficiencies reported in this study could

suggest that the white spruce in the sampled

areas may not be capable of taking full

advantage of improved local climatic

conditions such as warming (Miller 1995) if

nutrient limitations ‘bottleneck’ growth (Yarie

and Van Cleve 2010).

Table 3. Summary of the micronutrients analyses from 80 white spruce trees sampled across 20 sites throughout Yukon, Canada. The concentrations were compared with critical values from Carter (1992).

Micronutrients (ppm)

Foliar Nutrient

Concentration No. of plots diagnosed as deficient

Range Mean (SD) Severely deficient

Moderately deficient

Mildly deficient Adequate

B 3.8-14.8 8.0 (2.5) 1 19 0 0

Cu 1.3-5.5 2.1 (0.6) 0 5 15 0

Fe 15.2-128.2 30.0 (24.3) 0 13 6 1

Mn 33.5-731.3 238.8 (133.6) 0 0 0 20

Zn 21.5-76.3 37.1 (11.9) 0 0 0 20


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RESEARCH EXTENESION NOTE NO. 7 · This sampling approach was necessary as the height of the trees did not allow for the use of a ladder or extending pole pruner. Four field assistants