Effects Of Fire Intensity On Stoichiometric Characteristics Of Twigs And Leaves Of Major Plant In Larix Gmelinii Forests Of The Great Xing’an Mountains

Fire will change the environmental conditions such as light,temperature,water and nutrients in the forest,however,how carbon(C),nitrogen(N),phosphorus(P)contents and their stoichiometric characteristics of different life forms plants under different fire intensities adapt to environmental changes is still unclear.In this study,trees,shrubs and herbs are three types of life-form plants of Larix gmelinii forest in the Great Xing’an Mountains was selected as the research object,the contents of C,N and P in leaves and twigs of three types of life-form plants under different fire intensities(non-fire light fire and severe fire)and the contents of soil organic carbon(SOC),total nitrogen(TN)and total phosphorus(TP)in each plant were determined,the changes of plant ecological stoichiometry under different fire intensities were analyzed,the distribution of C,N and P contents in plant leaves and twigs under different fire intensities was studied,and the influence of fire intensities on the relationship between soil nutrients and stoichiometric characteristics of plant leaves and twigs was discussed.The results showed that:(1)P content in tree,shrub and herb leaves and C content in shrub leaves increased with the increase of fire intensity,C:P N:P in tree and herb leaves decreased with the increase of fire intensity,the content of C in tree leaves N:P in shrub leaves and N in herb leaves increased first and then decreased with the increase of fire intensity,the leaf C:N of shrub and herb decreased firstly and then increased with the increase of fire intensity,however,there were no significant differences in N content,C:N content in tree leaves,C:P content in shrub leaves and C content in herb leaves under different fire intensities.Life form was the main source of stoichiometric variation of plant leaves.Different fire intensities had no significant effect on C N P content and stoichiometric ratio of tree,shrub twigs.Only life form had significant influence on C content and C:P variation of twigs.There was no significant change in the pattern of in Stoichiometric characteristics of plant twigs and leaves under different fire intensities.(2)There was a significant difference in allometric index between twigs N and leaves N of tree under different fire intensities,and the distribution of N content in leaves of tree changed greatly in non-fire plots,the distribution of N content between twigs and leaves of trees in lightly fired and severely fired plots was constant.Different fire intensity had no significant effect on allometric growth index between tree and shrub twigs C and leaves C twigs P and leaves P and shrub twigs N and leaves N.There were significant differences in allometric index between leaves P and leaves N under different fire intensities,the distribution of P content in leaves of trees varied greatly in non-fire plot and lightly fired plot,however,P content and N content were equally distributed in the leaves of tree under severe fire.There were significant differences in allometric indices between twigs P and N of tree under different fire intensities.With the increase of fire intensities,the change of P content in twig was greater than that of N content.However,there was no significant difference in allometric index between P and N of shrub and herb leaves and between P and N of shrub twigs under different fire intensities.(3)The TN content of soil under trees and shrubs decreased with the increase of fire intensity,TP content in soil under shrub decreased firstly and then increased with the increase of fire intensity,however,there was no significant difference in SOC content under tree,shrub and herb soil TN content under herb soil and TP content under tree and herb soil under different fire intensities.There was a significant correlation between soil nutrients and stoichiometric characteristics of plant twigs and leaves,but the correlation was different under different fire intensities.Compared with non-fire plots,the correlation between soil nutrients and stoichiometric characteristics of plant twigs and leaves was lower under lightly fired and severely fired plots,this may be due to the change of environmental nutrients after fire,and the emergence of a large number of regenerative species after fire,which enhanced nutrient competition among plants,leading to changes in nutrient utilization strategies of plants.