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Optimal balance of water use efficiency and leaf construction cost with a link to the drought thresh
Haixia Wei,Tianxiang Luo and Bo Wu Background and Aims In arid environments, a high nitrogen content per leaf area (Narea) induced by drought can
enhance water use efficiency (WUE) of photosynthesis, but may also lead to high leaf construction cost (CC). Our
aim was to investigate how maximizing Narea could balance WUE and CC in an arid-adapted, widespread species
along a rainfall gradient, and how such a process may be related to the drought threshold of the desert–steppe ecotone
in northern China. Methods Along rainfall gradients with a moisture index (MI) of 017–041 in northern China and the northern
Tibetan Plateau, we measured leaf traits and stand variables including specific leaf area (SLA), nitrogen content
relative to leaf mass and area (Nmass, Narea) and construction cost (CCmass, CCarea), d13C (indicator of WUE), leaf
area index (LAI) and foliage N-pool across populations of Artemisia ordosica. Key Results In samples from northern China, a continuous increase of Narea with decreasing MI was achieved by
a higher Nmass and constant SLA (reduced LAI and constant N-pool) in high-rainfall areas (MI> 029), but by a
lower SLA and Nmass (reduced LAI and N-pool) in low-rainfall areas (MI 029). While d13C, CCmass and CCarea
continuously increased with decreasing MI, the low-rainfall group had higher Narea and d13C at a given CCarea, compared
with the high-rainfall group. Similar patterns were also found in additional data for the same species in the
northern Tibetan Plateau. The observed drought threshold where MI¼ 029 corresponded well to the zonal boundary
between typical and desert steppes in northern China. Conclusions Our data indicated that below a climatic drought threshold, drought-resistant plants tend to maximize
their intrinsic WUE through increased Narea at a given CCarea, which suggests a linkage between leaf functional
traits and arid vegetation zonation. Key words: Carbon isotope, drought threshold, leaf area index, leaf trait relation, moisture index, sandy land, vegetation
zonation, Artemisia ordosica.
INTRODU 原文链接：
 Optimal balance of water use efficiency and leaf construction cost with a link to the drought thresh.pd
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