State Key Laboratory of Forest and Soil Ecology, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang, China.
PLoS One. 2012;7(4):e35076. doi: 10.1371/journal.pone.0035076. Epub 2012 Apr 6.
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.
对于生态学家和生理学家来说，叶面生理生态学作为树冠内空间和时间上变化的环境因素（如阳光照射）的函数，对于理解整棵树的生理学以及预测生态系统碳平衡和生产力非常重要。因此，我们研究了红松树冠内不同年龄针叶的氮（N）、非结构性碳水化合物（NSC=可溶糖+淀粉）和δ（13）C 浓度，以了解与针叶年龄和树冠位置相关的生理学，以验证以下假设：N、NSC 和 δ（13）C 的浓度与针叶年龄和树冠位置有关（更多的光，更多的光合作用影响 N、NSC 和 δ（13）C），并制定一个准确的采样策略。本研究表明，与当年生针叶相比，一年生针叶的移动性碳水化合物（无论是在质量基础上还是在面积基础上）和 N（面积）（在面积基础上）浓度以及 NSC-N 比值显著更高，但 N（质量）（在质量基础上）浓度和比叶面积（SLA）显著更低。发现方位（南面对比北面对树冠侧）效应对淀粉[无论是在质量（ST（mass））还是在面积基础上（ST（area））]、δ（13）C 值和 N（面积）都有显著影响，树冠南侧的针叶水平高于树冠北侧。随着树冠垂直水平的增加，针叶 N（质量）浓度显著降低，但针叶 ST（质量）、ST（面积）和 δ（13）C 值显著增加。我们的研究结果表明，与光合作用和水分可用性相关的阳光照射树冠位置会影响淀粉积累和碳同位素分馏。与生理活性相关的针叶年龄在确定碳和氮生理学方面起着重要作用。本研究表明，跨尺度采样需要从可比的树冠位置仔细选择具有相等年龄的组织样本。
