Vertical Zonation Of Plant And Soil Ecological Stoichiometry On The Northern Slope Of Tianshan Mountains

Ecological stoichiometry of terrestrial ecosystem has been a hot issue in current research. The proportional relationships of nutritional elements with plants, soil, and the environment have been studied intensely. Relationships that occur along continuous environmental gradients should be analyzed to better understand these issues. While the researches in arid region most focused on desert ecosystem, rare focused on intrazonal vegetation. There are obvious differences in plant and soil types at different points along the hydrothermal gradient, which provide a unique advantage to examine the vertical spectrum of plants and soil ecological stoichiometry.In this study, we collected plant(trees, shrubs and herb) and topsoil(0-20 cm) samples respectively in plots that were set up every 100 m per altitude gradient in the northern slope of Tianshan Mountains(the altitude of which varies from 1000 to 3840 m), then examined content of organic carbon(C), total nitrogen(N), total phosphorus(P) and total potassium(K). Through the analysis of experimental data, we revealed the vertical zonality of vegetation and soil ecological stoichiometric characteristics in the north slope of Tianshan Mountains, discuss the contact of plant and soil in ecological stoichiometry, and analyzed the effect of climatic factors on vegetation and soil ecological stoichiometric characteristics. The results showed that:(1)Vegetation and soil nutrient contents on the northern slope of Tianshan Mountains were high, the average C, N, P, K content in plant leaves were 51.90%,1.80%, 0.17% and 2.33% respectively and those in soil were respectively 7.35%, 0.14%, 0.09% and 2.25%.(2)With the increase of altitude, the nutrient content and their stoichiometric ratios in plants changed differently. C content remained stable, and N content, C:P, N:P, C:K, N:K increased at first and then decreased, on contrast, the content of P, K and C: N decreased at first and then increased, while P:K decreased with the increase of altitude.(3)From the perspective of growth form, the C and N content and C:N were not significantly different among different growth forms. The P and K content of herbs plants both were significantly higher than those of trees and shrubs. C:P and N:P of shrubs was significantly higher than that of herbs. P: K and N:K of trees were significantly higher than herbs.C:K of trees,shrubs and herbs were significantly different with each other(P<0.05).(4)With the increase of altitude, the content of C, N, P and K, C: P, N: P, C: K, N: K, P:K in soil were increased at first and then decreased, and soil C: N showed a decrease trend.(5)Form the correlation analysis of plant and soil ecological stiochiometric characteristics,we found that only plant C:P and C:K ratio were significantly correlated with the soil C:P and C:K ratio, the correlation coefficients of plant and soil C, N, P and K content were smaller than that of the stoichiometric ratio. These results suggest that plants are mainly influenced by soil through stoichiometric ratios in the vertical zone.(6)There were differences in stoichiometry homeostasis of different growth form s, and the rank of H basically was: tree > herb > shrub. Stoichiometry homeostasis of ratios was higher than that of elements in plants.(7)The growth and development of plants in this area are mainly restricted by N. From the perspective of vegetation type, only coniferous forest and sub alpine shrub meadow are P restricted type; the other vegetation types are N restricted. From the perspective of growth form, trees and shrubs are more restricted by P, and herbs are more restricted by N.(8) The single factor precipitation had the greatest influence on plant growth and soil element content, followed by the change of hydrothermal ratio.In this thesis, we choose Tianshan Mountains which is very suitable for studying vegetation ecological stoichiometry along the elevation to carry out our research work, and then make clear its vertical zonation of plant and soil ecological stoichiometry. This work can be a good reference for studying vertical zonality of ecological stoichiometry, and make certain scientific contribution to enrich and promote the study of terrestrial ecosystem stoichiometry.