| Ecological chemometrics is a science to study the energy balance and multiple chemical element balance of biological system,which provides a new idea to study the interaction between plant and soil,and the cycle of carbon(C),nitrogen(N),phosphorus(P).Ecological stoichiometry of plant and soil is an important indicator of forest ecosystem health,the study of elemental ecological stoichiometry is of great significance to reveal the availability of nutrients and the cycle and balance mechanism of C,N,P and other elements.As an important part of forest ecosystem in Qilian Mountain,shrub community plays an indispensable role in maintaining ecological security in northwest China.Thus,it is very important to study the ecological stoichiometric characteristics of shrub communities for revealing the adaptability and feedback ability of shrub plants to the environment,and it can provide basic data and scientific basis for the protection,restoration and reconstruction of forest ecosystem in Qilian Mountain.Then,we selected Caragana tangutica,Berberis diaphana,Potentilla fruticose,Caragana jubata and Salix gilashanica which distributed in Dayekou watershed of Qilian Mountain as the research objects,and studied the variation of species composition,life form composition and species diversity of five typical shrub communities,as well as stoichiometric characteristics of different shrub communities and their relationships with soil physical and chemical factors.The results are shown below.(1)There were 48 plant species in shrub vegetation,belonging to 26 families and 38genera,and most of them were rosaceae,gramineae,compositae and leguminaceae in Dayekou watershed of Qilian Mountain.Ground bud plants accounted for the largest proportion of life form spectrum(37.09%).The H diversity index of different shrub communities showed that Potentilla fruticose>Caragana jubata>Berberis diaphana>Caragana tangutica>Salix gilashanica.The D diversity index of different shrub communities showed that Potentilla fruticose>Caragana jubata>Salix gilashanica>Berberis diaphana>Caragana tangutica.On the whole,the species diversity index of shrub community was low,H diversity index ranged from 1.12 to 2.26,and D diversity index ranged from 0.60 to 0.74.(2)Among the five shrub types,the average contents of C and N in the soil of Salix gilashanica shrub were significantly higher than those of the other shrubs,which were 74.93g·kg-1 and 6.10 g·kg-1,respectively,which indicated that the Salix gilashanica shrub had a strong accumulation effect on soil nutrients,and it was of great significance to improve the soil nutrient content.The Salix gilashanica shrub had higher C:P in all soil layers than the other four shrub types,which was the most potential shrub type for phosphorus fixation.The distribution pattern of soil organic carbon and total nitrogen was“inverted pyramid”in the profile;Soil alkali-hydrolyzable nitrogen,soil mass water content,and soil available phosphorus were the main soil factors that affected soil ecological stoichiometry of shrub communities.Soil C:P and N:P could be used to evaluate the P availability and nutrient restriction in this region.The soil nutrients of shrub communities were mainly restricted by N.(3)Soil mass water content,soil bulk density and soil total porosity were the main soil factors that affected the leaf stoichiometry;Soil bulk density,soil available phosphorus content and soil mass water content were the main soil factors that affected stem stoichiometry;Soil available phosphorus content and soil mass water content were the main soil factors that affected coarse root stoichiometric;Soil available phosphorus content and soil p H were the main soil factors that affected fine root stoichiometry.(4)Compared with the global average levels of C,N and P,the leaves,coarse roots and fine roots had higher C content of five typical shrub plants in Dayekou watershed of Qilian Mountain,while the leaves had lower N content and higher P content.Compared with the global land plants C:N:P,the leaves had higher C:N and C:P,and the coarse roots and fine roots had higher C:N.The N:P ratio of five typical shrub plants was less than 14,which indicated that the growth of shrub plants was more easily limited by N in Dayekou watershed of Qilian Mountain. |
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