Determinants Of Nutrients And Stoichiometric Characteristics Of Soil In Daxing'an Forest

The forest ecosystem is one of the important and major components in terrestrial ecosystems,which accounts for about half of the total land area and ecosystem of arbor-based biomes(including plants,animals,and microorganisms)and their abiotic environments(light,heat,water,gas,soil,etc.).The composition of forest ecosystems is extremely complex,ranging from simple individuals to different time and spatial scales throughout the region,running through complex ecological processes.The patterns and processes at different time and spatial scales in forest ecosystems are different as well.Observations on a single scale only reflect the patterns and processes at that scale.Defining a specific ecosystem should depend on the spatial-temporal scale and the corresponding process rate.Results obtained on one scale are not suitable for others.Soil is necessary for the growing of plants.Soil nutrients including soil organic carbon(SOC),total nitrogen(TN),total phosphorus(TP),and total potassium(TK)are determinants for the growing status of plants;while ecological stoichiometry directly reflects the specific growing of plants.The spatial heterogeneity of forest soil nutrients directly affects the forest production capacity,the ecological restoration direction and pathways;it also affects the spatial pattern of plant communities and the entire process of ecosystem succession.Under the change of global climate and environment,studying the response of forest soil chemical properties to the environment has become the main content and hot issue on the forest ecology.In this paper,we investigated the contents of organic carbon(SOC),total nitrogen(N),total phosphorus(P),total potassium(TK)and ecological stoichiometry of 0-20cm soil layer,and explored which factors were vital for soil nutrients including climatic factors,topographic factors and community factors in the natural forest of Daxing'an forest area;and to find the main differences of soil nutrients between different forest community types.The results show that the annual average rainfall(MAP)and seasonal accumulated temperature(TS)are the main climatic factors affecting soil nutrients significantly;while other factors are also significantly correlated,but the correlation is weaker.The MAP is positively correlated with SOC,TN,AP and AK,and negatively correlated with TK and TP.TS is positively correlated with SOC,TN,TK,AP and AK,and negatively correlated with TP.The main effects on the stoichiometric characteristics are PS and TS,which show significantly positive correlation and significantly negative correlation respectively,although other factors also present significant correlation,the correlation is weaker.The main influence factors of topographic factors is altitude,which is positively correlated with soil nutrients and negatively correlated with Ecostoichiometric characteristics significantly.Altitude is negatively correlated with soil nutrients and positively correlated with C:N and C:P significantly.Other topographic conditions(slope,aspect,slope position)are weakly correlated.Among the different forest community types,the soil nutrients of Quercus mongolica Fisch.ex Ledeb.forest are the lowest,and the contents in Pinus sylvestris L.var.mongolica Litv forest are the highest.The arragement of contents is:Pinus sylvestris L.var.mongolica Litv forest>Larix gmelinii(Rupr.)Kuzen forest>Larix gmelinii(Rupr.)Kuzen and Betula platyphylla Suk.mixed forest>Betula platyphylla Suk.Forest>Quercus mongolica Fisch.ex Ledeb.forest.The stoichiometric characteristics are the highest in Mongolian oak forest and the lowest in Pinus sylvestris var.mongolica,which is opposite to the order of soil nutrients.Among the forest community factors,the number of trees(QA)has the strongest impact on soil nutrients followed by the area of the diameter at breast(AreaDBH)which shows a significantly positive correlation,and the average height(HM)is negatively correlated;QA has the greatest impact on the ecological stoichiometry followed by the diameter of the DBD(AreaDBH)which shows a significantly negative correlation,and HM has a positive correlation.