Characteristics of Element Contents and Ecological Stoichiometry in Leaves of Common Calcicole Species in Maolan Karst Forest

Ecological adaptability mechanism of karst plants and their ecological response to environmental variation are essential for stability maintenance of karst forest ecosystem and restoration and reconstruction of degraded ecosystem. To investigate the ecological adaptability mechanism of plant in karst forest, the characteristics of 10 elements in plant leaves collected from Maolan Karst Forest were investigated. The results showed that the contents of N, K and Ca were greater than 10000 mg·kg-1, those of P, Mg and S varied between 1000 and 10000 mg·kg-1, those of Fe and Mn varied between 100 and 1000 mg·kg-1, and those of Zn and Ni were lower than 100 mg·kg-1. Except for element P, the contents of other elements were higher than those reported concentrations of the terrestrial higher plant required from the appropriate tissue, but all were within the scope of the average level of land vascular plants in the world. The element contents were characterized as w(Ca) w(K) w(Mg) type. The contents of elements P, Mg and Fe followed normal distribution, while the contents of elements N, K, Ca, S, Mn, Zn and Ni followed lognormal distribution. The correlations between N, S and P; Mg and K; S, Ca and Mg; Ca and Zn were statistically significant in different plant species( P ≤ 0.05). According to the element contents of w(Ca + Mg) in plant leaves, Pilea notate, Chirita liboensis and Handeliodendron bodinieri belonged to calciphile type plant, Evodia calcicola belonged to calciphilous plants, Beniodendron minus, Kmeria septentrionalis, Nandina domestica, Mallotus philippensis, Cinnamomum calcareum and Dendrocalamus tsiangii belonged to calcium-indifferent, Ampelocalamus calcareous belonged to calcifuges, while Carpinus lipoensis and Elaeagnus calcarea are between calciphilous plants and calcium-indifferent, Phoebe calcarea was between calcium-indifferent and calcifuges. The calcicole species were almost defined as P limited plants, and were characterized by lower content of P, K and higher content of Ca, Mg based on the element content ratios in the leaves. According to analysis of element ratios, coefficients of variation and correlation coefficients, these karst plants had relatively constant composition and coordinated relationship for necessary nutrient elements.