Grass (Poaceae) richness patterns across China's nature reserves

摘要

Explaining grass richness patterns over broad geographic scales is a central issue of biogeography and macroecology. In this investigation, we document the richness patterns of grasses across China's nature reserves, and discuss their possible explanations at national and regional scales using grass richness data coupled with information from climatic and topographical variables. Our results suggest that the water- and energy-related variables and elevation range (a surrogate of topographical heterogeneity) represent the primary explanations for the variation in grass richness across China's nature reserves. Significant relationships were found between energy and all grasses, water and C-3 grasses, and the combination of water and energy and C-4 grasses at the national scale. Topographical heterogeneity is strongly associated with grass richness across China, whereas climatic constraints to grass diversity vary regionally. In regions of high rainfall, the presence of C-4 grasses is determined by annual potential evapotranspiration and sunshine hours; the climatic constraint to C-3 grass richness in a large and varied region is sunshine hours; whereas in regions of low soil temperature, the temperature determines the grass richness pattern. Our results also suggest that water variables alone do not represent the primary predictor of grass richness at the regional scale.