Stoichiometric Characteristics of Leaf Nutrients in Karst Plant Species during Natural Restoration in Maolan National Nature Reserve, Guizhou, China

The cycling process of carbon (C), nitrogen (N), phosphorus (P), and potassium (K) elements plays a crucial role in ecosystem functions of karst forests. The leaf stoichiometry characteristics in four successional stages are studied in a karst area, southwest China. The N and P contents in each successional stage are generally higher in the growth phase (May-June 2016) than in the senescence phase (October-November 2015) but there are lower N: P ratios in the growth phase than in the senescence phase, showing a clear seasonal controls and coinciding with the Growth Rate Hypothesis. In the growth phase, the phytocommunity is mainly limited by the N content. In the senescence phase, all communities from the early successional stage to the mid successional stage are prone to N limitation but they are significantly affected by a combination of N, P, and K from the late successional stage to the climax successional stage and the P limitation are stronger in the climax successional stage. The specific leaf area is the most important impact factor to leaf stoichiometric characteristics at each successional stage. These results indicate that nitrogen addition in growth stage may promote vegetation restoration and karst forest ecosystem stability.