A high nitrogen content per leaf area (Narea) induced by drought can enhance water use efficiency (WUE), but may also increase leaf construction cost (CC). Wei et al. hypothesize that maximizing Narea would constitute a process to balance WUE and CC in drought-resistant plants along a rainfall gradient.
They find that below a drought threshold with moisture index ≤0.29, drought-resistant plants tend to maximize their WUE through increased Narea at a given CCarea. The drought threshold corresponds well to the zonal boundary between typical and desert steppes in northern China, suggesting a linkage between leaf traits and arid vegetation zonation.
Haixia Wei, Tianxiang Luo, Bo Wu, 2016, 'Optimal balance of water use efficiency and leaf construction cost with a link to the drought threshold of the desert steppe ecotone in northern China', Annals of Botany, vol. 118, no. 3, pp. 541-553 http://dx.doi.org/10.1093/aob/mcw127