|Needle-age related variability in nitrogen, mobile carbohydrates, and δ13C within Pinus koraiensis tree crowns.|
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|PMID: 22493732 Owner: NLM Status: MEDLINE|
|For both ecologists and physiologists, foliar physioecology as a function of spatially and temporally variable environmental factors such as sunlight exposure within a tree crown is important for understanding whole tree physiology and for predicting ecosystem carbon balance and productivity. Hence, we studied concentrations of nitrogen (N), non-structural carbohydrates (NSC = soluble sugars + starch), and δ(13)C in different-aged needles within Pinus koraiensis tree crowns, to understand the needle age- and crown position-related physiology, in order to test the hypothesis that concentrations of N, NSC, and δ(13)C are needle-age and crown position dependent (more light, more photosynthesis affecting N, NSC, and δ(13)C), and to develop an accurate sampling strategy. The present study indicated that the 1-yr-old needles had significantly higher concentration levels of mobile carbohydrates (both on a mass and an area basis) and N(area) (on an area basis), as well as NSC-N ratios, but significantly lower levels of N(mass) (on a mass basis) concentration and specific leaf area (SLA), compared to the current-year needles. Azimuthal (south-facing vs. north-facing crown side) effects were found to be significant on starch [both on a mass (ST(mass)) and an area basis (ST(area))], δ(13)C values, and N(area), with higher levels in needles on the S-facing crown side than the N-facing crown side. Needle N(mass) concentrations significantly decreased but needle ST(mass), ST(area), and δ(13)C values significantly increased with increasing vertical crown levels. Our results suggest that the sun-exposed crown position related to photosynthetic activity and water availability affects starch accumulation and carbon isotope discrimination. Needle age associated with physiological activity plays an important role in determining carbon and nitrogen physiology. The present study indicates that across-scale sampling needs to carefully select tissue samples with equal age from a comparable crown position.|
|Cai-Feng Yan; Shi-Jie Han; Yu-Mei Zhou; Cun-Guo Wang; Guan-Hua Dai; Wen-Fa Xiao; Mai-He Li|
|Type: Journal Article; Research Support, Non-U.S. Gov't Date: 2012-04-06|
|Title: PloS one Volume: 7 ISSN: 1932-6203 ISO Abbreviation: PLoS ONE Publication Date: 2012|
|Created Date: 2012-04-11 Completed Date: 2012-09-04 Revised Date: 2013-06-26|
Medline Journal Info:
|Nlm Unique ID: 101285081 Medline TA: PLoS One Country: United States|
|Languages: eng Pagination: e35076 Citation Subset: IM|
|State Key Laboratory of Forest and Soil Ecology, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang, China.|
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Carbon Isotopes / metabolism
Nitrogen / physiology*
Photosynthesis / physiology*
Pinus / physiology*
Plant Leaves / physiology*
Starch / metabolism
Water / metabolism
|0/Carbohydrates; 0/Carbon Isotopes; 7727-37-9/Nitrogen; 7732-18-5/Water; 9005-25-8/Starch|
Journal ID (nlm-ta): PLoS One
Journal ID (iso-abbrev): PLoS ONE
Journal ID (publisher-id): plos
Journal ID (pmc): plosone
Publisher: Public Library of Science, San Francisco, USA
Yan et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Received Day: 5 Month: 7 Year: 2011
Accepted Day: 12 Month: 3 Year: 2012
collection publication date: Year: 2012
Electronic publication date: Day: 6 Month: 4 Year: 2012
Volume: 7 Issue: 4
E-location ID: e35076
PubMed Id: 22493732
Publisher Id: PONE-D-11-12793
|Needle-Age Related Variability in Nitrogen, Mobile Carbohydrates, and δ13C within Pinus koraiensis Tree Crowns Alternate Title:Carbon and Nitrogen within Tree Crowns|
1State Key Laboratory of Forest and Soil Ecology, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang, China
2Graduate University of Chinese Academy of Sciences, Beijing, China
3Research Station of Changbai Moutain Forest Ecosystems, Chinese Academy of Sciences, Erdaobaihe, China
4Key Laboratory of Forest Ecology and Environment, State Forestry Administration, Chinese Academy of Forestry, Beijing, China
5Tree Physioecology, Swiss Federal Research Institute WSL, Birmensdorf, Switzerland
|Friedrich-Alexander-University Erlangen-Nurenberg, Germany
|Correspondence: * E-mail: email@example.com
Contributed by footnote: Conceived and designed the experiments: CY MHL SH. Performed the experiments: CY YZ CW GD WX. Analyzed the data: CY MHL. Wrote the paper: CY MHL.
The crown of a tree is important because it contains foliage which captures light, photosynthesizes and provides energy for tree growth and reproduction. A tree’s crown also interacts with other atmospheric variables such as CO2, temperature, and humidity. Physioecology of leaves/needles in relation to temporal and spatial variability of those factors within a crown is of direct interest to ecologists and physiologists , , to understand the whole tree physiology and to predict the carbon balance and productivity at individual and ecosystem level.
A tree’s geometrical structure and foliar characteristics affect the solar radiation interception, leading to spatial heterogeneity of photosynthesis, growth, and biomass within a crown –. For example, net photosynthetic rates have been found to be higher on the S-facing crown side and at the top crown level than on the N-facing side and at the bottom crown level –. Peters et al.  reported that sun-exposed Pinus canariensis needles at the upper crown levels had higher net photosynthetic rates and stomatal conductance than needles which were shaded. Such effects have been explained as light effects, since more radiation should be intercepted on the sunlit crown side or at the upper crown levels, leading to significant crown position effects. Single leaf area, length and thickness, and stomatal parameters were also found to vary with crown position –. Significant azimuthal effects on both leaf thickness and density within Fagus crenata crown were also reported, with greater leaf thickness and density on the N-facing than the S-facing crown side .
Younger needles are located on the outer crown and older needles in the inner crown position within a tree’s crown. Hence, needle age within a conifer crown not only indicates needle age-dependent physiology but also implies a position effect . Needle morphology and biochemistry were found to be needle-age dependent , –. Different aged needles of conifers showed different eco-physiological performance and, thus, may represent different levels of N and mobile carbohydrate concentrations. Li et al.  found that current-year needles had significantly lower concentrations of soluble sugars, starch, and NSC than 1-yr-old needles in Pinus cembra trees in July when the current-year needles were not fully mature. But at the end of the growing season, this difference disappeared . The lower concentrations of mobile carbohydrates in current-year needles during the growing season was explained by dilution effects caused by lower density in non-mature organs , since younger needles had higher SLA (cm2g−1 as the ratio of projected needle area to needle dry mass) or lower leaf mass per unit leaf area (LMA) than older needles , .
Leaf δ13C values are closely correlated with chemical components and leaf morphology, such as leaf N  and starch concentration , and stomatal conductance . Li et al.  demonstrated that δ13C in leaves was positively correlated with N and negatively correlated with SLA in Quercus aquifolioides. Values of δ13C have also been found to be associated with leaf or needle age , . Barszczowska and Jedrysek  found more negative δ13C values in older foliage than in younger needles of Pinus nigra trees. Studies in several evergreen and deciduous species have also found less negative values of δ13C in younger leaves than in older leaves –. Other studies documented that δ13C values tended to be less negative at the upper canopy level compared to the lower canopy level –. For example, for the same-aged foliage across 10 tree species, δ13C values were significantly less negative in the upper canopy than in the lower canopy, and there were markedly differences in foliage δ13C values between the S- and N-facing crown side for 4 coniferous species but no such differences for 6 broad-leaved tree species .
Pinus koraiensis, a national protected plant species in China, is a dominant tree species of the climax vegetation (broad-leaved Korean pine mixed forest) in northeastern China. Recently, many national and international projects related to this species have been initiated, due to its economic and ecological importance (Han SJ, personal communication). These projects need more accurate sampling strategies to achieve the desired sample, in order to get comparable and comprehensive data across scales. To our knowledge, no studies have tested the temporal and spatial variations of N, mobile carbohydrates, and stable carbon isotope in different-aged needles within a P. koraiensis crown. Hence, we studied N, NSC, and δ13C within P. koraiensis crowns to understand needle age- and crown position-related physiology, in order to develop an accurate sampling strategy. We hypothesized that 1) concentrations of N, NSC (soluble sugars, starch), and δ13C are needle-age dependent, since the leaf morphology and physiological activity are age-dependent –, , , , and 2) the concentrations of N, NSC, and δ13C in needles on the S-facing crown side or at the top crown level are higher than those on the N-facing side or at the bottom crown level, respectively, due to the differences in sunlight exposure within a crown –, , .
No specific permits were required for the described field studies. The relatively widely distributed species P. koraiensis has been protected in the study region, the present study related to conservation eco-physiology of this species did not need a special permit, and was carried out within the research area of our long-term forest ecosystem research station (Changbai Mountain Forest Research Station) established in 1979. On the other hand, the field sampling had no damage on the sample trees because we took only 20 grams of fresh needles for each sample.
The study forest, close to the Changbai Mountain Forest Ecosystem Research Station (127°47′E, 42°19′N, 738 m a.s.l.), ranged from 1000 to 1200 m a.s.l. on Changbai Mountain, Jilin Province, northeastern China. According to the climate data collected in the research station from 1970 to 2008, the mean annual temperature is 3.2°C, and the average temperature in January and July is −15.6°C and 19.7°C, respectively. The mean growing season temperature is 14.6°C (May to October). The mean annual precipitation ranges from 600 to 900 mm year–1, 70% of which falls between June and August. Soils were classified as mountain brown clay coniferous forest soil developed from lava. The forest is a naturally generated, mixed Pinus koraiensis-broadleaved forest dominated by P. koraiensis, Tilia amurensis, Quercus mongolica, Fraxinus mandshurica and Acer mono, .
Fifteen healthy P. koraiensis trees were randomly selected from the upper canopy layer (i.e. no stressed and shaded trees) within a 10 km2 area. Sample trees were 70–90 years old, 17.5–18.2 m in height and 30–50 cm in diameter at breast height. The length and width of crowns were 6–8 m and 5–7 m, respectively. The crown length of each sample tree was divided into 3 equal segments of top, middle, and bottom crown level.
New needles of P. koraiensis emerge in May at the beginning of the growing season and mature in summer (Zhou YM, personal communication), and the needle longevity is two years and rarely reaches 3 years in the study region. Li et al.  indicated that concentrations of carbohydrates in immature needles were instable. Given the large seasonal variation in mobile carbohydrates in Pinus species , , , we decided to take needle samples at the end of growing season, as suggested by Shi et al. , in order to have comparable samples of mature needles. From October 5 to 6, 2010, one leading branch was cut from the N-facing and S-facing crown side at the top, middle, and bottom crown level, respectively, using a pruning saw. A total of 6 branches were cut from each sample tree, climbed using climbing spikes strapped to the climber’s feet. Current-year and 1-yr-old needles were collected separately from the outer shoots in each branch cut. All samples were kept in a cool box and killed in a microwave oven (at the middle-high temperature for 45–60 seconds) and dried to constant weight at 65°C . Dried needle materials were ground into fine powder (passed through 100 meshes) for analysis.
The dried needle powder (approx. 0.2 mg) was put in a tin foil cup and then combusted in an elemental analyzer (Flash EA-1112, Carlo Erba Thermoquest, Italy) interfaced (Conflo II, Thermo Finnigan, Bremen, Germany) to a continuous-flow isotope ratio mass spectrometer (DELTA plus XL, Thermo Finnigan, Bremen, Germany).
Carbon isotope composition was reported by the following conventional δ13C values notation relative to Vienna Pee Dee Belemnite international standard :
δ13C(‰) = (Rsa/Rsd - 1) × 1000
where Rsa and Rsd are the molecular abundance ratios of carbon isotope (13C/12C) of the sample and the standard, respectively. The overall precision of the replicate samples measurements was estimated to be better than ±0.2‰ standard deviation.
Twenty-five fresh needles from each sample were scanned (Founder Z1000, Founder Technology Group Inc., Beijing, China) at 600 dpi, and analyzed using public Scion Image software (Image 4.02 for windows, online available via http://www.scioncorp.com, National Institutes of Health, Bethesda MD, USA) to determine the projected needle area . Afterwards the needle dry mass (70°C, 3 days) was determined and the SLA was calculated. SLA was then used to calculate concentrations of N and carbohydrates expressed on a projected needle area basis.
The powdered leaf material (0.1 g) was put into a 10 ml centrifuge tube, where 5 ml of 80% ethanol were added. The mixture was incubated at 80°C in a water bath shaker for 30 min, and then centrifuged at 4000 rpm for 5 min. The pellets were extracted two more times with 80% ethanol. Supernatants were retained, combined, and stored at −20°C for soluble sugar determinations. The soluble sugar fraction was measured. Soluble sugars in the collected extracts were determined using the anthrone method . An aliquot of the extract was hydrolysed in 5 ml of 0.4% anthrone solution (4 g anthrone in 1000 ml 95% H2SO4) in a boiling water bath for 15 min. After cooling, the sugar concentration was determined spectrophotometrically (ultraviolet-visible spectrophotometer 752S, Cany Precision Instruments Co., Ltd., Shanghai, China) at 620 nm. Glucose was used as a standard. The sugar concentration was calculated on a dry mass basis (SUmass, % d.m.) and a projected needle area basis (SUarea, g m–2), respectively.
The ethanol-insoluble pellet was used for starch extraction. Ethanol was removed by evaporation. Starch in the residue was released in 2 ml distilled water for 15 min in a boiling water bath. After cooling to room temperature, 2 ml of 9.2 mol/L HClO4 were added. Starch was hydrolyzed for 15 min. Four ml distilled water was added to the samples. Samples were then centrifuged at 4000 rpm for 10 min. The pellets were extracted one more time with 2 ml of 4.6 mol/L HClO4. Supernatants were retained, combined, and filled to 20 ml. The starch concentration was measured spectrophotometrically (ultraviolet-visible spectrophotometer 752S) at 620 nm using anthrone reagent, and calculated by multiplying glucose concentrations by the conversion factor of 0.9. Glucose was used as a standard. The starch concentration was calculated on a dry mass basis (STmass, % d.m.) and a projected needle area basis (STarea, g m–2), respectively.
The concentration of total N was determined in finely ground oven-dried samples by the micro Kjeldahl procedure, using CuSO4, K2SO4, and H2SO4 for digestion, and NH3 was determined on an auto-analyzer, using the indophenol-blue colorimetric method . The N concentration was expressed both on a dry mass basis (Nmass, % d.m.) and a projected needle area basis (Narea, g m–2), respectively.
All presented and discussed concentrations data, except where otherwise noted, are expressed on a dry mass basis (% d.m.). NSC is defined as the sum of the starch plus the total soluble sugars for each sample , . NSC-N ratio is defined as the ratio of NSC concentration to N concentration for each sample , . All data (NSC, starch, total soluble sugars, and N concentrations, δ13C, and SLA) were checked for normality by Kolmogorov–Smirnov-Tests. To test differences in the parameters mentioned above within a tree crown, three-factor ANOVAs were performed with needle age (current-year needles, and 1-yr-old needles), azimuthal direction (S-facing vs. N-facing crown side), and vertical crown level (top, middle, and bottom crown level) as factors, and followed, if significant, by one-factor ANOVAs to compare the means of those parameters within each factor (i.e. needle age, or azimuthal direction, or vertical crown level). To get a clear feature of the parameters studied within a tree crown, data were pooled, according to needle age, azimuthal direction, and vertical crown level, respectively, and the pooled data were analyzed using one-way ANOVAs. Pearson’s correlation coefficients were used to examine the relationships between variables. All statistical analyses were performed using SPSS 11.5 for windows.
Needle age significantly affected the leaf total N and carbohydrates (NSC, soluble sugars, and starch) concentrations expressed both on a mass basis (Table 1) and on an area basis (data not shown), NSC-N ratios, and SLA, but not δ13C values (Table 1). The needle age effects seemed to be more pronounced at the middle- and bottom-crown rather than at the top-crown level (Table 2). Current-year needles had significantly lower Narea (−9.7%) but higher Nmass (+22.0%) and greater SLA (+34.7%) than 1-yr-old needles (Table 3). Conversely, both mass-based and area-based concentrations of NSC (−13.8% and −36.0%, respectively), sugars (−8.2%, −35.6%), and starch (−15.0%, −37.2%), as well as NSC-N ratio (−28.4%), reduced significantly in current-year needles compared to 1-year-old needles (Table 3). But the current-year needles and the 1-yr-old needles had the same sugar-starch ratio (∼4.15; Table 3).
Effects of crown directions were found to be significant on starch and δ13C values in needles (Table 1), but these effects were dependent upon the crown-levels (crown direction x crown-level interaction for both starch and δ13C with p < 0.01) (Table 1). The crown direction effects seem to be more pronounced at the lower crown levels rather than at the upper crown levels (Table 2). Needles on the S-facing crown side had significantly higher starch concentrations (+9.5% for STmass, +11.7% for STarea) and higher δ13C values (−28.83‰ vs. −29.34‰) compared to needles on the N-facing crown side (Table 3). Not Nmass but Narea showed significantly lower levels in needles on the N-facing crown side (−9.2%) than on the S-facing crown side (Table 3). Needle SLA did not significantly vary with crown directions (Table 1) but tended to have lower level in the sun-exposure crown side (Table 3).
Increasing crown levels significantly affected needle δ13C values, starch, and Nmass concentration (Table 1) but not Narea (statistical data not shown; see also Table 3). The crown level effects on needle starch and δ13C were found to be dependent upon the crown-direction (e.g. crown direction x crown level interaction for both starch and δ13C with p<0.01; Table 1). Needle Narea did not change, but Nmass concentrations significantly decreased, and needle STmass, STarea, and δ13C values significantly increased with increasing crown level (Table 3). Although concentrations of sugars and NSC did not change, the sugar-starch ratio decreased with increasing crown level from 4.64 (bottom), to 4.45 (middle) and 3.49 (top crown level) (Table 3). Needle SLA did not significantly vary with crown levels (Table 1) but tended to decrease with increasing crown levels (Table 3).
The present study found that the total Nmass concentration was significantly higher in current-year needles than in 1-yr-old needles within a crown (Table 3). Leaf age-effects on foliage N concentration have already been reported for several coniferous , – and broad-leaved species , . Needle Nmass declined steadily with leaf age for both Pinus aristata and Pinus contorta and Pinus sylvestries. The same age-related results of Nmass were also reported for other different coniferous species –. For broad-leaved species, Tateno and Kawaguchi  found that foliage Nmass concentrations decreased with increasing leaf age in both Podocarpus nagi and Neolitsea aciculate, and Mickelbart  observed that older leaves had higher Nmass than younger leaves in Acer×freemanii trees. These results may suggest that the contents of mobile nutrients (e.g. N) in the younger needles/leaves represent both N uptake and re-translocation form older foliages since the younger foliages are physiologically more active than the older ones.
Total Nmass concentrations did not differ between needles on the S-facing crown side and N-facing crown side (Table 3). Similarly, Mickelbart  also found that foliage Nmass was slightly higher but not statistically different in leaves on the S-facing crown side compared to the N- and W-facing crown side of Acer×freemanii trees. But Perica  reported that leaf Nmass concentrations were significantly higher (+11.8%, p<0.001) on the S-facing crown side than on the N-facing crown side in olive (Olea europaea L.) trees.
Needle Nmass concentrations decreased significantly with increasing vertical levels within a crown (Table 3). Previous studies documented an increase , , a decrease , , or no change ,  in leaf N concentrations with increasing crown levels. For example, Nippert and Marshall  found that the mean Nmass was significantly (p<0.0001) higher in sun foliage than in shade foliage in Abies grandis and Pseudotsuga menziesii var. glauca throughout the growing season. Foliar Narea was significantly greater in the top third than in the bottom third of the crown for Pinus contorta ssp. latifolia. But Dale and Causton  found that higher Nmass concentration occurred in shaded conditions rather than in higher light conditions for Veronica spp. because N uptake in shaded conditions exceeded its metabolic requirement. Han et al.  found that needle Narea concentration decreased by 22–27% from the upper to the lower crown level, as well as from the outer crown to the inner crown, corresponding to the decrease in photosynthetic photon flux density, in Pinus densiflora trees. Livingston et al.  found that there were poor relationships between N concentration allocation and intercepted radiation in young Pinus radiata trees grown in a plantation in New Zealand.
However, our results indicated that the effects of needle age or crown position on N depended upon whether N concentration was expressed on a mass basis or an area basis (Table 3). McGarvey et al.  found that not Nmass but Narea increased significantly with increasing vertical crown levels in Pinus taeda and Pinus elliottii var. elliottii. Griffin  observed that leaf Nmass significantly decreased by 17.5% (4.0%, 3.8%, and 3.3% for foliage at lower, middle, and upper canopy, respectively), but leaf Narea significantly increased (2.6, 2.7, and 3.0 g m–2 for foliage at lower, middle, and upper canopy, respectively) from lower canopy leaves to upper canopy leaves in Populus deltoides trees.
In line with previous findings gained from different conifers , , , we found that needle N concentration was positively correlated with SLA (R2 = 0.741, p < 0.01) (Table 4), and that SLA decreased significantly with increasing needle age (Table 3). Similar age effects on needle SLA have been widely reported for Pinus species ,  and other coniferous species . Compared to current-year needles with greater SLA, older needles with lower SLA (i.e. higher LMA) contained more structural compounds (e.g. lignin), which diluted needle total N concentration expressed on a dry mass basis , . Niinemets  indicated that LMA of Picea abies needles increased with increasing needle age due to greater needle density, thickness and width in older needles.
Leaves exposed to high light at the higher crown level tended to have lower SLA (Table 3). Decreases in needle SLA with increasing crown level have already been widely observed in Pinus and other coniferous species , –. Increases in SLA with canopy depth (Table 3) may be a mechanism of needles to capture more light per unit leaf mass at lower irradiances . Previous studies also proposed that water stress and hydraulic limitations may be two main reasons to influence needle morphology, resulting in smaller thicker needles in the upper crown of large old trees , , . Lower needle SLA on the S-facing crown side and at the higher crown level found in the present paper may be a result of starch accumulation in the sun-exposed needles (Table 3).
Leaf N concentration was found to be strongly positively correlated with leaf photosynthetic capacity both in tropical and temperate forest trees , , , . Schoettle  found that current-year needles had higher N concentration and higher photosynthetic capacity than 1-yr-old needles in adult Pinus aristata trees. A strongly positive relationship between foliar Nmass and light-saturated photosynthesis rates (Amax) was reported for Pinus taeda trees . Leaves having higher photosynthetic rate may produce sugar more efficiently.
Our study showed that concentrations of NSC, soluble sugars, and starch were higher in 1-yr-old needles than in current-year needles (Table 3). This finding is consistent with the results gained from Pinus cembra. According to Niinemets , older needles have higher abilities to capture light and accumulate NSC. However, Li et al.  found that needle NSC concentrations increased with needle age for younger needles (<2 years old) and decreased with needle age for older needles (>2 years old) in Abies georgei trees. Concentrations of sugars and NSC in needles did not differ with azimuthal direction between the S- and N-facing crown side (Table 3) and also did not vary with increasing crown level (Table 3). Similar results gained from Pinus cambra trees have been reported . Li et al.  did not detect any crown position effects on needle NSC in Abies georgei and in Juniperus saltuaria grown in Tibetan Plateau. Würth et al.  also did not find any significant differences in NSC concentration in leaves between sun and shade positions in 17 tropical tree species ranging from 75 to150 years old in Panama. These findings , , together with the present results (see Table 3), indicated that the effects of sunlight exposure (S-facing vs. N-facing crown side, and top, middle, and bottom crown level) within a crown play only negligible role in determining NSC and soluble sugars in needles or leaves. According to Hoch and Körne , levels of mobile carbohydrates in needles/leaves may be mainly affected by low temperature.
Levels of NSC concentrations were determined by soluble sugars (p < 0.01) rather than by starch (Table 4). Not soluble sugars and NSC but starch concentrations in needles significantly increased with sun exposure (Table 3). This result may be explained as a result of (1) light-induced increases in photosynthesis ,  and (2) sucrose-starch conversion and partitioning changed by excess photosynthetic capacity over respiration and other use with increasing crown level associated with sun exposure. The light-saturated photosynthetic rate was found to be greater for needles in the upper crown than for needles in either the middle or lower crown locations for different Pinus species , . Excess sugars are rapidly converted to starch temporarily stored in the leaves. Insufficient photosynthesis (e.g. lower light intensity or other disturbance) leads to conversion of starch to sugars to meet the needs of a plant. These also indirectly explained why the sugar-starch ratio decreased steadily with increasing crown level (Table 3).
The present study showed that the NSC-N ratio was significantly higher in 1-yr-old needles (+40.8%) compared to current-year needles (Table 3). Similarly, Li et al.  found that old tissues had higher C-N ratios than younger ones in Quercus aquifolioides in SW China. In contrast, Griffin et al.  showed significant decrease in C-N ratios from upper canopy to lower canopy leaves in Populus deltoides.
Barszczowska and Jedrysek  reported that δ13C values were higher (less negative) in younger needles (2 to 7 months old) than in older needles (1 to 2 years old) in Pinus nigra trees in Croatia and southern Spain. Würth et al.  and Holtum and Winter  also found that δ13C values in young leaves of several tropical tree species were less negative than those in older leaves in Panama throughout a seasonal cycle. Our results showed that the δ13C value in current-yr needles did not differ with that in 1-yr old needles (Table 3). This result may be caused by a combined effect of positive effects of starch and negative effects of sugars and NSC on δ13C (Table 4). In line with the present study, Gebauer and Schulze  found that the δ13C values of needles (Picea abies) did not change consistently with needle age, but did decrease from the sun- to the shade-crown.
Crown position including azimuthal direction and vertical crown level significantly affected needle δ13C values in our study (Table 3), which is consistent with some previous studies , . Holtum and Winter  investigated 9 tree species in tropical forests and found that canopy position significantly influenced leaf δ13C values. A lower rate of photosynthesis in shaded needles, due to light limitation, might result in more negative δ13C values at lower crown levels . Another possible explanation is the hydraulic limitation hypothesis , ,  that expects decreasing water potential and increasing water stress in foliage at upper crown level, leading to declines in carbon isotope discrimination (less negative δ13C values) . For example, Ishii et al.  found that bulk leaf water potential (Ψ) decreased and δ13C content values increased with increasing crown level in Sequoia sempervirens trees in California, USA. Less negative δ13C may be associated with higher stomatal conductance and higher photosynthetic capacity in the upper canopy compared to the lower canopy, as has been observed for different Pinus species , . This trend could also be caused by the accumulation of starch in the needles at the higher crown level (Table 3). Our results showed that δ13C values were not correlated with the concentrations of NSC and soluble sugars, but significantly positively correlated with the starch concentration (R2 = 0.533, p<0.01, Table 4). In line with our results, Jäggi et al.  pointed out that needle δ13C value had a strong correlation with starch concentration in Picea abies trees in the Swiss Plateau.
The present study indicated that needle age had significant effects on nitrogen and carbon physiology. Azimuthal (S-facing vs. N-facing crown side) effects were found to be significant on starch and δ13C values with higher levels in needles on the S-facing crown side compared to the N-facing crown side. Needle Nmass significantly decreased, but needle starch and δ13C significantly increased with increasing vertical crown levels. Previous studies have reported marked age effects and effects of crown position associated with sunlight exposure on leaf physioecological performance , , . Our results suggest that the sun-exposed crown position related to photosynthetic activity and water availability affects starch accumulation and carbon isotope discrimination. Needle age associated with physiological activity plays an important role in determining carbon and nitrogen physiology. The present study indicates that across-scale sampling needs to adhere to a strict age specific tissue selection from a comparable crown position.
Competing Interests: The authors have declared that no competing interests exist.
Funding: This study was supported by the National Natural Science Foundation of China (Project no. 40930107), Key Laboratory of Forest Ecology and Environment, State Forestry Administration, Chinese Academy of Forestry (CAFIFEEPYBB2007001), and the Major State Basic Research Development Program (2011CB403200). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
We would like to express gratitude to Yan Zhang and Xubing Cheng for the assistance in carbohydrates analysis.
|1.||Bond BJ. Year: 2000Age-related changes in photosynthesis of woody plants.Trends Plant Science5349353|
|2.||Ozanne CMP,Anhuf D,Boulter SL,Keller M,Kitching RL,et al. Year: 2003Biodiversity Meets the Atmosphere: A global view of forest canopies.Science30118318612855799|
|3.||Sabatier S,Barthelemy D. Year: 1999Growth dynamics and morphology of annual shoots, according to their architectural position, in young Cedrus atlantica (Endl.) Manetti ex Carrière (Pinaceae).Annals of Botany84387392|
|4.||Suzuki M. Year: 2003Size structure of current-year shoots in mature crowns.Annals of Botany9233934712853280|
|5.||Li MC,Kong GQ,Zhu JJ. Year: 2009Vertical and leaf-age-related variations of nonstructural carbohydrates in two alpine timberline species, southeastern Tibetan Plateau.Journal of Forest Research14229235|
|6.||Johnson IR,Riha SJ,Wilks DS. Year: 1996Modelling daily net canopy photosynthesis and its adaptation to irradiance and atmospheric CO2 concentration.Agricultural Systems50135|
|7.||Gonzalez-Real MM,Baille A. Year: 2000Changes in leaf photosynthetic parameters with leaf position and nitrogen content within a rose plant canopy (Rosa hybrida).Plant, Cell and Environment23351363|
|8.||Peters J,Gonzalez-Rodriguez AM,Jimenez MS,Morales D,Wieser G. Year: 2008Influence of canopy position, needle age and season on the foliar gas exchange of Pinus canariensis.European Journal of Forest Research127293299|
|9.||England JR,Attiwill PM. Year: 2005Changes in leaf morphology and anatomy with tree age and height in the broadleaved evergreen species, Eucalyptus regnans F. Muell.Trees207990|
|10.||Geiger J. Year: 1961Zur elastischen und unelastischen streuung von elektronen an silberfolien.Zeitschrift Für Physik161243251|
|11.||Maguire DA,Batista JLF. Year: 1996Sapwood taper models and implied sapwood volume and foliage profiles for coastal Douglas-fir.Canadian Journal of Forest Research26849863|
|12.||Niinemets U,Ellsworth DS,Lukuanova A,Tobias M. Year: 2001Site fertility and the morphological and photosynthetic acclimation of Pinus sylvestris needles to light.Tree Physiology211231124411696411|
|13.||Niinemets U,Kull K. Year: 2003Leaf structure vs. nutrient relationships vary with soil conditions in temperate shrubs and trees.Acta Oecologica24209219|
|14.||Iio A,Fukasawa H,Nose Y,Kato S,Kakubari Y. Year: 2005Vertical, horizontal and azimuthal variations in leaf photosynthetic characteristics within a Fagus crenata crown in relation to light acclimation.Tree Physiology2553354415741146|
|15.||Zha TS,Wang KY,Ryyppo A,Kellomaki S. Year: 2002Needle dark respiration in relation to within-crown position in Scots pine trees grown in long-term elevation of CO2 concentration and temperature.New Phytologist1563341|
|16.||Li MH,Kräuchi N,Dobbertin M. Year: 2006Biomass distribution of different-aged needles in young and old Pinus cembra trees at highland and lowland sites.Trees20611618|
|17.||Xiao CW,Janssens IA,Yuste J,Ceulemans R. Year: 2006Variation of specific leaf area and upscaling to leaf area index in mature Scots pine.Trees20304310|
|18.||Li CY,Wu CC,Duan BL,Korpelainen H,Luukkanen O. Year: 2009Age-related nutrient content and carbon isotope composition in the leaves and branches of Quercus aquifolioides along an altitudinal gradient.Trees2311091121|
|19.||Li MH,Hoch G,Körner C. Year: 2001Spatial variability of mobile carbonhydrate within Pinus cembra trees at the alpine treeline.Phyton41203213|
|20.||Morecroft MD,Woodward FI. Year: 1996Experiments on the causes of altitudinal differences in the leaf nutrient contents, size and δ13C of Alchemilla alpina.New Phytologist134471479|
|21.||Jäggi M,Saurer M,Fuhrer J,Siegwolf R. Year: 2002The relationship between the stable carbon isotope composition of needle bulk material, starch, and tree rings in Picea abies.Oecologia131325332|
|22.||Meinzer FC,Goldstein G,Neufeld HS,Grantz DA,Crisosto GM. Year: 1992Carbon isotope composition in relation to leaf gas exchange and environmental conditions in hawaiian Metrosideros polymorpha populations.Oecologia91305311|
|23.||Constable GA,Rawson HM. Year: 1980Carbon production and utilization in cotton - inferences from a carbon budget.Australian Journal of Plant Physiology7539553|
|24.||Brendel O,Handley L,Griffiths H. Year: 2003The δ13C of Scots pine (Pinus sylvestris L.) needles: spatial and temporal variations.Annals of Forest Science6097104|
|25.||Barszczowska L,Jedrysek MO. Year: 2005Carbon isotope distribution along pine needles (Pinus nigra Arnold).Acta Societatis Botanicorum Poloniae749398|
|26.||Terwilliger VJ. Year: 1997Changes in the δ13C values of trees during a tropical rainy season: Some effects in addition to diffusion and carboxylation by Rubisco?American Journal of Botany841693170021708573|
|27.||Helle G,Schleser GH. Year: 2004Beyond CO2-fixation by Rubisco - an interpretation of 13C/12C variations in tree rings from novel intra-seasonal studies on broad-leaf trees.Plant, Cell and Environment27367380|
|28.||Chevillat V,Siegwolf R,Pepin S,Körner C. Year: 2005Tissue-specific variation of δ13C in mature canopy trees in a temperate forest in central Europe.Basic and Applied Ecology6519534|
|29.||Broadmeadow MSJ,Griffiths H,Maxwell C,Borland AM. Year: 1992The carbon isotope ratio of plant organic material reflects temporal and spatial variations in CO2 within tropical forest formations in trinidad.Oecologia89435441|
|30.||Livingston N,Whitehead D,Kelliher FM,Wang YP,Grace JC,et al. Year: 1998Nitrogen allocation and carbon isotope fractionation in relation to intercepted radiation and position in a young Pinus radiata D. Don tree.Plant, Cell and Environment21795803|
|31.||Gutierrez MV,Meinzer FC. Year: 1994Carbon isotope discrimination and photosynthetic gas exchange in coffee hedgerows during canopy development.Australian Journal of Plant Physiology21207219|
|32.||El-Sharkawy MA,De Tafur SM. Year: 2007Genotypic and within canopy variation in leaf carbon isotope discrimination and its relation to short-term leaf gas exchange characteristics in cassava grown under rain-fed conditions in the tropics.Photosynthetica45515526|
|33.||Hao ZQ,Yu DY,Yang XM,Ding ZH. Year: 2002α diversity of communities and their variety along altitude gradient on northern slope of Changbai Mountain.Chinese Journal of Applied Ecology1378578912385204|
|34.||Wu JL,Wang M,Lin F,Hao ZQ,Ji LZ,et al. Year: 2009Effects of precipitation and interspecific competition on Quercus mongolica and Pinus koraiensis seedlings growth.Chinese Journal of Applied Ecology2023524019459358|
|35.||Fischer C,Holl W. Year: 1991Food Reserves of Scots Pine (Pinus sylvestris L) .1. Seasonal Changes in the Carbohydrate and Fat Reserves of Pine Needles.Trees5187195|
|36.||Ludovici KH,Allen HL,Albaugh TG,Dougherty PM. Year: 2002The influence of nutrient and water availability on carbohydrate storage in loblolly pine.Forest Ecology and Management159261270|
|37.||Shi PL,Körner C,Hoch G. Year: 2006End of season carbon supply status of woody species near the treeline in western China.Basic and Applied Ecology7370377|
|38.||Li MH,Xiao WF,Shi PL,Wang SS,Zhong YD,et al. Year: 2008Nitrogen and carbon source-sink relationships in trees at the Himalayan treelines compared with lower elevations.Plant, Cell and Environment3113771387|
|39.||Craig H. Year: 1957Isotopic standards for carbon and oxygen and correction factors for mass-spectrometric analysis of carbon dioxide.Geochimica et cosmochimica acta12133149|
|40.||O’Neal ME,Landis DA,Isaacs R. Year: 2002An Inexpensive, Accurate Method for Measuring Leaf Area and Defoliation Through Digital Image Analysis.Journal of Economic Entomology951190119412539831|
|41.||Lowther WL,Bonish PM. Year: 1980Field-evaluation of commercially pelleted clover seed.New Zealand Journal of Experimental Agriculture8249253|
|42.||Seifter S,Muntwyler E,Harkness DM. Year: 1950Some effects of continued protein deprivation, with and without methionine supplementation, on intracellular liver components.Proceedings of the Society for Experimental Biology and Medicine75465014797731|
|43.||Li MH,Hoch G,Körner C. Year: 2002Source/sink removal affects mobile carbohydrates in Pinus cembra at the Swiss treeline.Trees16331337|
|44.||Li MH,Xiao WF,Wang SG,Cheng GE,Cherubini P,et al. Year: 2008Mobile carbohydrates in Himalayan treeline trees I. Evidence for carbon gain limitation but not for growth limitation.Tree Physiology281287129618519260|
|45.||Schoettle AW. Year: 1994Influence of tree size on shoot structure and physiology of pinus contorta and pinus aristata.Tree Physiology141055106814967670|
|46.||Heljä-Sisko Helmisaari. Year: 1992Spatial and age-related variation in nutrient concentrations of Pinus sylvestris needles.Silva Fennica26145153|
|47.||Niinemets U. Year: 1997Acclimation to low irradiance in Picea abies: influences of past and present light climate on foliage structure and function.Tree Physiology1772373214759897|
|48.||Gebauer G,Giesemann A,Schulze ED,Jäger HJ. Year: 1994Isotope ratios and concentrations of sulfur and nitrogen in needles and soils of Picea abies stands as influenced by atmospheric deposition of sulfur and nitrogen compounds.Plant and Soil164267281|
|49.||Hatcher PE. Year: 1990Seasonal and age-related variation in the needle quality of five conifer species.Oecologia85200212|
|50.||Tateno R,Kawaguchi H. Year: 2002Differences in nitrogen use efficience between leaves from canopy and subcanopy trees.Ecological Research17695704|
|51.||Mickelbart MV. Year: 2010Variation in Leaf Nutrient Concentrations of Freeman Maple Resulting from Canopy Position, Leaf Age, and Petiole Inclusion.Hortscience45428431|
|52.||Perica S. Year: 2001Seasonal fluctuation and intracanopy variation in leaf nitrogen level in olive.Journal of Plant Nutrition24779787|
|53.||Nippert J,Marshall J. Year: 2003Sources of variation in ecophysiological parameters in Douglas-fir and grand fir canopies.Tree Physiology2359160112750052|
|54.||Hollinger D. Year: 1996Optimality and nitrogen allocation in a tree canopy.Tree Physiology1662763414871700|
|55.||Dale M,Causton D. Year: 1992The Ecophysiology of Veronica chamaedrys, V. montana and V. officinalis. IV. Effects of Shading on Nutrient Allocations - A Field Experiment.Journal of Ecology80517526|
|56.||Schoettle AW,Smith WK. Year: 1998Interrelationships among light, photosynthesis and nitrogen in the crown of mature Pinus contorta ssp. latifolia.Tree Physiology19132212651327|
|57.||Han Q,Kawasaki T,Katahata S,Mukai Y,Chiba Y. Year: 2003Horizontal and vertical variations in photosynthetic capacity in a Pinus densiflora crown in relation to leaf nitrogen allocation and acclimation to irradiance.Tree Physiology2385185712865251|
|58.||McGarvey RC,Martin TA,White TL. Year: 2004Integrating within-crown variation in net photosynthesis in loblolly and slash pine families.Tree Physiology241209122015339730|
|59.||Griffin K,Turnbull M,Murthy R. Year: 2002Canopy position affects the temperature response of leaf respiration in Populus deltoides.New Phytologist154609619|
|60.||Koch G,Sillett SC,Jennings GM,Davis SD. Year: 2004The limits to tree height.Nature42885185415103376|
|61.||Yoder BJ,Ryan MG,Waring RH,Schoettle AW,Kautmann MR. Year: 1994Evidence of reduced photosynthetic rates in old trees.Forest Science40513527|
|62.||van Hees AFM,Bartelink HH. Year: 1993Needle area relationships of Scots pine in the Netherlands.Forest Ecology and Management581931|
|63.||Perterer J,Körner C. Year: 1990The problem of reference parameters in physiological-ecological research with conifer needles.Forstwissenschaftliches Centralblatt109220241|
|64.||Bond BJ,Farnsworth BT,Coulombe RA,Winner WE. Year: 1999Foliage physiology and biochemistry in response to light gradients in conifers with varying shade tolerance.Oecologia120183192|
|65.||Ishii H,Ford ED,Boscolo ME,Manriquez AC,Wilson ME,et al. Year: 2002Variation in specific needle area of old-growth Douglas-fir in relation to needle age, within-crown position and epicormic shoot production.Tree Physiology22314011772553|
|66.||Marshall JD,Monserud RA. Year: 2003Foliage height influences specific leaf area of three conifer species.Canadian Journal of Forest Research33164170|
|67.||Chmura DJ,Tjoelker MG. Year: 2008Leaf traits in relation to crown development, light interception and growth of elite families of loblolly and slash pine.Tree Physiology2872974218316305|
|68.||Weiskittel AR,Temesgen H,Wilson DS,Maguire DA. Year: 2007Sources of within- and between-stand variability in specific leaf area of three ecologically distinct conifer species.Annals of Forest Science65103|
|69.||Woodruff DR,McCulloh KA,Warren JM,Meinzer FC,Lachenbruch B. Year: 2007Impacts of tree height on leaf hydraulic architecture and stomatal control in Douglas-fir.Plant, Cell and Environment30559569|
|70.||Würth MKR,Pelaez-Riedl S,Wright SJ,Körner C. Year: 2005Non-structural carbohydrate pools in a tropical forest.Oecologia143112415578227|
|71.||Hoch G,Körner C. Year: 2003The carbon charging of pines at the climatic treeline: a global comparison.Oecologia135102112647099|
|72.||Würth MKR,Winter K,Körner C. Year: 1998Leaf carbohydrate responses to CO2 enrichment at the top of a tropical forest.Oecologia1161825|
|73.||Holtum J,Winter K. Year: 2005Carbon isotope composition of canopy leaves in a tropical forest in Panama throughout a seasonal cycle.Trees19545551|
|74.||Gebauer G,Schulze ED. Year: 1991Carbon and nitrogen isotope ratios in different compartments of a healthy and a declining Picea abies forest in the Fichtelgebirge, NE Bavaria.Oecologia87198207|
|75.||Roux-Swarthout DL,Terwilliger V,Christianson M,Martin C,Madhavan S. Year: 2001Carbon isotopic ratios of atmospheric CO2 affect the δ13C values of heterotrophic growth in Nicotiana tabacum.Plant Science16056357011166444|
|76.||Ometto J,Flanagan LB,Martinelli LA,Moreira MZ,Higuchi N,et al. Year: 2002Carbon isotope discrimination in forest and pasture ecosystems of the Amazon Basin, Brazil.Global Biogeochemical Cycles 161109, doi:10.1029/2001GB001462, 2002|
|77.||Ryan M,Phillips N,Bond B. Year: 2006The hydraulic limitation hypothesis revisited.Plant, Cell and Environment29367381|
|78.||Ishii HT,Jennings GM,Sillett SC,Koch GW. Year: 2008Hydrostatic constraints on morphological exploitation of light in tall Sequoia sempervirens trees.Oecologia15675176318392856|
|79.||Takeuchi Y,Kubiske ME,Isebrands JG,Pregtizer KS,Hendrey G,et al. Year: 2001Photosynthesis, light and nitrogen relationships in a, young deciduous forest canopy under open-air CO2 enrichment.Plant, Cell and Environment2412571268|
Table 1 Effects of needle age, crown direction, and crown level on soluble sugars, starch, non-structural carbohydrates (NSC), and total nitrogen concentrations expressed on a dry mass basis, NSC-N ratio, δ13C, and SLA in Pinus koraiensis needles. F- and P-values are given (n = 15).
|Nitrogen||Soluble sugars||Starch||NSC||δ13C||NSC-N ratio||SLA|
|Needle age (A)||1||27.485||< 0.001||3.930||0.050||17.977||< 0.001||6.227||0.028||1.268||0.282||25.268||< 0.001||22.051||0.002|
|Crown direction (D)||1||3.683||0.079||0.027||0.872||6.969||0.022||0.256||0.622||8.822||0.012||0.270||0.613||0.144||0.714|
|Crown level (L)||2||4.816||0.029||1.085||0.369||10.289||0.002||0.774||0.483||19.265||< 0.001||1.675||0.228||0.281||0.764|
Note (1) significant differences (P < 0.05) are highlighted in bold, and (2) statistical analyses using data expressed on a projected area basis and on a dry mass basis showed the same results and were then not repeated.
Table 2 Mean values (±SE, n = 15) of concentrations (%, expressed on a dry mass basis) of soluble sugars, starch, non-structural carbohydrates (NSC), and nitrogen, NSC-N ratio, δ13C (‰), and SLA (cm2 g–1) in current year and one-year-old needles within Pinus koraiensis tree crown.
|Top crown level||Middle crown level||Bottom crown level|
|Current-yr needles||1-yr-old needles||Current-yr needles||1-yr-old needles||Current-yr needles||1-yr-old needles||Current-yr needles||1-yr-old needles||Current-yr needles||1-yr-old needles||Current-yr needles||1-yr-old needles|
Note (1) different letters indicated statistically significant (P < 0.05) difference in each parameter between current-year needles and one-year-old needles within each crown position (no letters = no statistical difference), and (2) analyses using data expressed on a projected area basis and on a dry mass basis showed the same statistical results between current-yr and 1-yr-old needles within each category, and were then not repeated.
Table 3 Mean values (n = 15) of concentrations of needle soluble sugars, starch, non-structural carbohydrates (NSC), and total nitrogen expressed on a dry mass basis (dM-based, % d.m.) and on a projected area basis (pA-based, g m–2), as well as NSC-N ratio, δ13C content values (‰), and SLA (cm2 g–1) in needles within Pinus koraiensis tree crown.
|Nitrogen||Sugars||Starch||NSC||NSC-N ratio||Sugar-starch ratio||δ13C||SLA|
|Vertical crown level|
Different letters indicate statistically significant (P < 0.05) difference within column for each category (no letters = no statistical difference).
Table 4 Correlation coefficients among NSC (non-structural carbohydrates), soluble sugars, starch, nitrogen contents, NSC-N ratio, δ13C contents, and SLA for Pinus koraiensis needles.
|Nitrogen||Soluble Sugars||Starch||NSC||δ13C||NSC-N ratio||SLA|
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