| The annual rainfall and soil erosion is scarce and serious in Loess Region of Western Shanxi Province.Research ideas and methods of ecological stoichiometry can help to understand the characteristics of nutrient elements in complex ecosystem.A combination of field investigation and analytical experiments was used to study the contents of soil organic carbon,total nitrogen and total phosphorus in different organs(leaf,branch,trunk and root)of six typical tree species(Populus davidiana,Larix gmeini,Quercus liaotungensis,Platycladus orientalis,Pinus tabuliformis,Robinia pseudoacacia)and in litter and forest soil.The correlation and stability of C,N and P contents in different tree species,litter and soil were also discussed.The main research results are as follows:(1)The leaf C contents decreased in the order of Q.liaotungensis>P.davidiana>P.tabuliformis>R.pseudoacacia>P.orientalis>L.gmeini,the leaf N contents decreased in the order of R.pseudoacacia>P.davidiana>L.gmeini>Q.liaotungensis>P.tabuliformis>P.orientalis,the leaf P contents decreased in the order of L.gmeini>Q.liaotungensis>P.orientalis>P.tabuliformis>P.davidiana>R.pseudoacacia.The leaf C:N value of P.davidiana,,L.gmeini and R.pseudoacacia were low,resulting in lower N utilization efficiency and C assimilation capacity.The leaf C:N value of P.orientalis,P.tabuliformis,Q.liaotungensis were high,resulting in higher N utilization efficiency and C assimilation capacity;The C:P value,C assimilation capacity and P utilization efficiency of R.pseudoacacia were higher than that of the other five tree species.(2)The growth of R.pseudoacacia was restricted by P,P.davidiana growth by N and P restriction,Q.liaotungensis,L.gmeini,P.tabuliformis and P.orientalis growth was limited by N;Six species of litter C content was rich,three kinds of broad-leaved forest(Q.liaotungensis,P.davidiana,R.pseudoacacia)litter N was higher,while the three coniferous forest(P.orientalis,P.tabuliformis,L.gmeini)litter is lack of N.The P.davidiana forest litter is the lack of P,other five species were not found in P deficiency phenomenon.The mineralization and decomposition effect of three broad-leaved forest litter and decomposition rate were stronger than three kinds of coniferous forest litter.The six kinds of forest soil C,N,P content decreased with the soil depth increased,and(0-10cm)content was the highest.The C and P elements in the 6 kinds of forest land were relatively deficient,the P element was the most serious,and the N element was not lacking.(3)The highest C content of six species mainly concentrated in the branch and trunk,The lowest C content of three broad-leaved species was located in the root,while the lowest C content in the leaf of three coniferous species;The highest N and P content of six species were in the leaf and branch,the lowest concentration in the trunk and root;The C:N and C:P of the six species were mainly located in the trunk and root,and the lowest in the leaf and branch;Six tree species N:P highest in leaf,lowest in the trunk and branch.(4)There was no significant correlation among C,N and P in the leaf of six species,while there was a extremely significant or significant correlation between leaf and litter,leaf and soil,litter and soil in the six species;When the external environment is the change of soil element content,the homeostasis of organs of five species(P.davidiana,L.gmeini,P.orientalis,P.tabuliformis,R.pseudoacacia)was stronger than that of the external environment is the change of litter elements content,However,the homeostasis of the organs of Q.liaotungensis was lower than that of the external environment is the change of the litter elements content.The results of this study can help to reveal the utilization status,constraints and allocation patterns of forest ecosystem nutrient and have certain significance to the restoration and management of fragile habitats in Loess region of Western Shanxi. |
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