Leaf nitrogen:phosphorus (N:P) stoichiometry is a novel diagnostic method that can indicate plant growth limitation in terrestrial ecosystem. Soil nitrogen (N) and phosphorus (P) are considered to be the most important factors influencing plant growth in the karst ecosystem. However, the biotic and abiotic factors controlling the patterns of leaf N:P in different functional groups of the karst ecosystem of southwestern China remain unknown.

A research team led by Prof. WANG Kelin at the Institute of Subtropical Agriculture (ISA) of Chinese Academy of Sciences conducted a research on karst ecosystem in Huanjiang County, Guangxi Zhuang Autonomous Region, in southwestern China. They analyzed the effects of the functional groups, diversity, soil N and P concentrations, and nutrient availability on the variance of leaf N, P, and N:P ratios.

The plants, which can adapt their resource strategies to high-resource habitats in the karst ecosystem, will have high growth rate. For example, due to the use of N₂ fixation, legumes have high N:P ratios and are affected by P limitation but not N limitation. The leaf N and N:P ratios were higher in legumes than that in nonlegumes. Grasses had higher leaf P but lower leaf N and N:P ratios (N:P < 10) than shrubs and trees. It suggested the growth of grasses is limited by nitrogen. Soil total N and total P had major effects on the leaf N:P ratios of all the studied plants in the karst region.

Besides, revegetation and restoration have achieved little success in the region due to the great variability of environmental variables such as topographic conditions and soil heterogeneity associated with high pH, nutrient and water deficiencies. Soil P is higher at low elevations on hillslopes. The shrubs cover a wide area of 60–80 % of the karst ecosystem in southwest China. Thus, the plants that easily colonize at low elevation of shrub areas should be selected to increase the success of vegetation restoration.

This research project was financially supported by the Major State Basic Research Program of the People’s Republic of China (2006BACO1A10), the Knowledge Innovation Program of the Chinese Academy of Sciences (KZCX2-YW-436), and the National Natural Science Foundation of China (31270555; 30800162).

The study entitled "Leaf N:P stoichiometry across plant functional groups in the karst region of southwestern China" has been published in Trees.