C, N, P Stoichiometry Of Tree, Shrub, Herb Leaves And Litter In Forest Ecosystem Of Shaanxi Province

121 sampling sites were selected to study the C:N:P stoichiometric characteristics among leaves of tree, shrub, herb and litter of the majority forest community of Shaanxi Province. We also studied their relationships with geographical factors. We divided forest ecosystem in Shaanxi Province into Shaanbei, Guanzhong, Shaannan 3 regions, then we studied the similarities and differences in C, N, P stoichiometry among different layers(tree, shrub, herb leaves and litter) and different kind of trees(evergreen trees and deciduous trees). We also compared leaf and litter C, N, P stoichiometry in trees of different families(Robinia pseucdoacacia, Quercus liaotungensis, Pinus tabulaeformis) and the same genre(Quercus liaotungensis, Quercus variabilis, Quercus acutissima), and we also aimed to distinguish their relationships with environmental factors(latitude, longitude, altitude, mean annual tempreture and mean annual precipitation). The main findings are as follows:1) The results showed that the C, N concentrations were highest in tree leaves, and the P concentration was highest in herb leaves, and the C, N, P concentrations were lowest in litter. The N:P ratios of tree, shrub and herb leaves were not significantly different, but theirs were all significantly higher than litter layer’s, indicating that N:P ratio of different living life forms’ leaves was significantly stable. The relationships of leaves C, N, P stoichiometry between tree and herb leaves were better than those of between tree and shrub leaves, indicating that the herb layer had stronger competitiveness. Correlation analysis results showed that the relationship between the shrub layer and latitude was closest, while the relationship between the herb layer and longitude was closest. Multivariate linear regression analysis results show that the influence of geographical factors to herb leaves was longitude > latitude > altitude, while to tree, herb leaves and litter was latitude > longitude > altitude.2) The leaf C, N, P concentration of evergreen trees was smaller than those of deciduous trees. In 3 regions, C concentration and C:N, C:P ratios of evergreen trees was bigger than those of deciduous trees, while N concentration of evergreen trees was smaller than that of deciduous trees. P concentration in Shaanbei and Shaannan and N:P ratios in Shaanbei and Guanzhong of evergreen trees was smaller than that of deciduous trees. Decomposition rate of litter was negatively correlated relationships with C:N, C:P, N:P ratios, then we can judge that evergreen trees in Shaanbei had the slowest decomposition rate. While the deciduous trees in Shaanbei had the highest decomposition rate, and the deciduous trees in Shaannan had the slowest decomposition rate. In 3 regions, C concentration in tree layer was all the biggest. And C concentration of each layer was all biggest in Shaannan.3) In different families, leaf and litter C concentration and C:N, C:P ratios were all Pinus tabulaeformis > Quercus liaotungensis > Robinia pseucdoacacia. Except the N:P ratio in litter was Quercus liaotungensis > Robinia pseucdoacacia > Pinus tabulaeformis, leaf and litter N, P concentration and N:P ratios was all Robinia pseucdoacacia > Quercus liaotungensis > Pinus tabulaeformis. In the same genre, leaf C, N concentration and C:N, C:P ratios were all Quercus acutissima > Quercus variabilis > Quercus liaotungensis, while the P concentration was Quercus liaotungensis > Quercus variabilis > Quercus acutissima, and the C:P ratios was Quercus variabilis > Quercus acutissima > Quercus liaotungensis. Coefficient of variation of leaf N, P concentration and N:P ratios was all smallest in Quercus liaotungensis. Leaf N and P concentration were significantly positive correlated, indicating that the absorption of N, P had a certain proportional relationship in the process of building blade. Compared with leaves, litter N, P concentration was significantly decreased, which showed the nutrition resorption characteristics.4) Leaf and litter C, N, P concentration and their ratios in 5 species, approximately showed the trends of decreasing with latitude and longitude, and increasing with the mean annual temperature and precipatition, except the C:N ratios. Leaf C:N ratios showed the trend of increasing with the longitude. Compared with other environmental factors, altitude had smaller correlations among leaf and litter C, N, P stoichometry. Compared with Quercus liaotungensis and Quercus acutissima, leaf and litter C, N, P concentration and their ratios in Quercus variabilis was less affected by the environment. Compared with other environment factors, altitude had little influence on leaf and litter C, N, P stoichometry. No matter trees in different families or in the same genre, different kind of trees had different response to environmental factors. Indicating that different kind of trees had different of adaptation strategies to environmental change, and this may form in the long-term evolution of plants and related to the genetic characteristics of plants themselves. There were excellent relationships among leaf and litter C, N, P stoichometry and environmental factors, and they can be expressed in the regression equation. Under the background of global warming, the regression equation can help a better understanding on leaves and litter C, N, P stoichiometric characteristics and environmental factors in regional scale.