Leaf-trait relationships of Quercus liaotungensis along an altitudinal gradient in Dongling Mountain, Beijing

Few studies have examined leaf-trait relationships in the distribution of individual species along an environmental gradient. Here we address the issue by testing for the leaf-trait relationships of Quercus liaotungensis, a dominant deciduous woody species in northern China, along an altitudinal gradient in Dongling Mountain, Beijing. These leaf traits included specific leaf area (SLA), leaf dry matter content (LDMC), and leaf nitrogen, phosphorus, and potassium concentration on mass basis (Nmass, Pmass and Kmass, respectively). Along the altitudinal gradient, negative relationships between SLA and LDMC and Nmass were found, and Nmass, Pmass and Kmass correlated with each other positively. Relationship between Nmass and Pmass was stronger than the ones between Nmass and Kmass, and between Pmass and Kmass. The weak and negative relationship between SLA and Nmass might result from trade-offs that limit photosynthesis and water use efficiency along the altitudinal gradient, suggesting many environmental factors of local site being the collective forcing of drivers. Out of our expectations, Nmass and Pmass related very weakly to soil N and P, and no significant relationship between Kmass and soil K was found along elevation. These relationships could be used to predict the productivity of the population with changing environment in this region.