Causes for the unimodal pattern of leaf carbon iso

Authors: Hongxia Zhao Baoli Duan Yanbao Lei

Publish Date: 2015/01/31

Volume: 12, Issue: 1, Pages: 39-48

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Abstract

Leaf morphological and physiological traits of Abies faxoniana growing in a natural forest along an altitudinal gradient were measured with the aim to identify the central mechanism for the marked variation in foliar δ13C determined by an isotope ratio mass spectrometer There is a unimodal pattern of plant functional traits in these temperate and semihumid areas Stomatal parameters specific leaf area and C/N ratio increased whereas C N and δ13C values decreased with increasing altitude below 3000 m asl In contrast they exhibited opposite trends above 3000 m asl Our results demonstrated that highaltitude plants achieve higher water use efficiency WUE at the expense of decreasing nitrogen use efficiency NUE whereas plants at 3000 m can maintain a relatively higher NUE but a lower WUE Such intraspecific differences in the tradeoff between NUE and WUE may partially explain the altitudinal distribution of the plants in relation to moisture and nutrient availability Our results clearly indicate that the functional relations between nutritional status and the structure of leaves are responsible for the altitudinal variations associated with δ13C The pivotal role of specific leaf area in regulating plant adaptive responses provides a potential physiological mechanism for the observed growth advantage of populations occupying the medium altitude These adaptive responses to altitudinal gradients showed that an altitude of approximately 3000 m asl is the optimum distribution zone for A faxoniana allowing the most vigorous growth and metabolism These results improve our understanding of the various roles of environmental and biotic variables upon δ13C dynamics and provide useful information for subalpine coniferous forest management

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