Needle-Age Related Variability in Nitrogen, Mobile Carbohydrates, and δ13C within Pinus koraiensis Tree Crowns

Abstract

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 δ13C 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 δ13C are needle-age and crown position dependent (more light, more photosynthesis affecting N, NSC, and δ13C), 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 Narea (on an area basis), as well as NSC-N ratios, but significantly lower levels of Nmass (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 (STmass) and an area basis (STarea)], δ13C values, and Narea, with higher levels in needles on the S-facing crown side than the N-facing crown side. Needle Nmass concentrations significantly decreased but needle STmass, STarea, and δ13C 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.

On the challenges of using field spectroscopy to measure the impact of soil type on leaf traits

“…Additionally they found that foliar concentrations of P and other rock-derived minerals varied strongly with site, while nitrogen concentrations varied little; soluble carbon, structural and defensive traits hardly varied between sites; and pigment (in their case just chlorophyll) was the least predictable of traits, probably because photosynthesis is rapidly up-and downregulated in response to light in the environment among other factors . Similarly, δ 13 C is known to vary strongly with light and relative humidity (Buchmann et al, 1997;Yan et al, 2012), which may be why species and soil explained little of its variance in our study. These parallels between tropical and temperate systems suggest broad similarities in plant responses to soil across different regions that differ greatly in temperature.…”

How timing of stem girdling affects needle xylem structure in Scots pine

“…For both ecologists and physiologists, foliar morphology and anatomy are important for understanding the physiology of the whole tree (Yan et al 2012). The control of leaf size, and, by extension, leaf form, is a principle way in which plants adapt to environmental conditions.…”

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