Leaf life span as a simple predictor of evergreen forest zonation in China


Tianxiang Luo, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Shuangqing Road 18, Haidian District, PO Box 2871, Beijing 100085, China.
E-mail: luotx@itpcas.ac.cn


Aim  Our aim was to investigate how the average life span of canopy leaves might be used to predict the geographical distribution of natural forests at large geographical scales, and to explore the link between leaf characteristics and ecosystem functioning. We examine whether there is a general relationship between canopy mean leaf life span and climate (i.e. temperature and precipitation) that can be used to predict evergreen forest zonation in China.

Location  Forest areas in China.

Methods  During July and August of 2002–2004, we conducted a latitudinal forest transect spanning about 30° of latitude in eastern China. The canopy mean leaf life span was calculated to include all tree species (groups) in each forest plot through weighted averages scaled up from branch-level measurements. Data from our previous work conducted in the Tibetan Alpine Vegetation Transects (TAVT) and from other investigators were compiled to supplement our results. Based on regression equations developed on the pooled data, and using gridded temperature and precipitation datasets, we simulated the distribution of canopy mean leaf life span for forests in China. The predicted leaf life span zonation was compared with a map of Chinese forest vegetation divisions published in 1980.

Results  Canopy mean leaf life span across 10 evergreen forest plots in eastern China showed a decreasing trend as mean annual temperature increased, following a common logistic pattern consistent with the data from the TAVT and other investigators. In pooled data for 40 evergreen forest plots across tropical and boreal regions, canopy mean leaf life span generally showed a negative relationship with mean annual temperature (r2 = 0.72, < 0.001), and a positive correlation with mean annual precipitation where mean annual temperature was > 8°C (r2 = 0.45, < 0.01). The climate-based simulations of leaf life span zonation compared well with the previously published boundaries of forest vegetation divisions in eastern China.

Main conclusions  Our results reveal that mean leaf life span in evergreen forests follows a common logistic pattern associated with mean annual temperature and precipitation, which can in turn be used to predict evergreen forest zonation in eastern China.