Studies On Stoichiometric Characteristics Of Nitraria Leaf And Nebkhas Soil On Minqin

Nitrogen and phosphorus are basic nutrient elements of plants, and their cyclings affect most processes in ecosystem. N:P ratio of plant leaf tissues was often used as an index of resource limitation in many studies on ecological stoichiometry of leaf tissue nitrogen and phosphorus concentrations, suitable for ecosystems from sea and lake to land. Diverse N:P stoichiometry for different plant species, due to the species-specific differences on resource acquisition and use efficiency, and the response to disturbance, may result in adaption of species to particular environment. And the concentrations of N and P in the same plant species are affected by environment and phylogeny.This paper focused on Nitraria and its nebkhas, and our main goals were twofold: 1) we analyzed the N and P concentrations of leaf tissues of two dominant species Nitraria praevisa and N. tangutorun in the arid Minqin oasis, and N, P and soil organic matter (SOM) of three 20 cm deep layers of the sited nebkhas soil, and investigated the relationships of the ecological stoichiometry of plant leaf and the sited nebkhas soil; 2) we analyzed the N, P and SOM of N. tangutorun nebkhas with three different successional stages (rudimental stage, developing stage, stabilizing stage) to investigate the stoichiometry of nebkhas during succession.The results indicated:1) There was a significant positive relationship for leaf N and P concentrations between the two species; 2) N, P and SOM in the same layer differ significantly between the two species sited soils (P< 0.01); 3) N was concentrated at soil layer of 0-20 cm for N. praevisa and N, P and SOM at soil layer of 20-40 cm for N. tangutorun; 4) Further studies are necessary to reveal whether or not N:P ratio can be used as an index of resource limitation in the extreme environments, such as desert ecosystem with water as the primary limiting factor; 5) the order of the nutrition conditions of N. tangutorun nebkhas from high to low was stabilizing stage> developing stage> rudimental stage; 6) the "fertile island" effect was operating in the developing stage and stabilizing stage, and the nutrition was concentrated in the surface of the nebkhas soil.