Latitudinal Patterns And Influence Mechanism Of Ecological Stoichiometry And Nutrient Cycling In Quercus Acutissima Forests

Plant ecological stoichiometry and nutrient cycling characteristics are the result of plant adaptation to external environmental conditions during long-term evolution.At present,studies on plant ecological stoichiometry are mostly found in large-scale multi-species,but there are relatively few studies on single species at regional scale.Quercus acutissima is one of the important broad-leaved tree species and widely distributed in China.It is one of the ideal species to study the latitude pattern of ecological stoichiometry and nutrient cycling characteristics.The pattern of latitude variation of ecological stoichiometry and nutrient cycling characteristics of Q.acutissima forest on latitude gradient and its influencing mechanism were studied in order to understand the nutrient cycling process of various components(organs,litter,soil)in Q.acutissima forest and strengthen the conservation and sustainable development of Q.acutissima species resources.In this study,seven samples of Q.acutissima forest were selected from natural reserves or state-owned forest farms in the core area of the North-South Transect in eastern China(NSTEC),and the geographical and meteorological factors were collected.Each tree was measured,and three standard trees were selected to collect fresh leaves,branches,absorptive fine-roots,transport fine-roots,litters and soils.The stoichiometry characteristics,morphological characters of leaves and roots were analyzed,and nutrient cycling characteristics were calculated.And the latitudinal variation of stoichiometry and nutrient cycling characteristics was explored,and the effects of environmental and biological factors on stoichiometry and nutrient cycling characteristics of Q.acutissima forest were investigated.The results show that:First,on the latitudinal gradient,the nitrogen content of leaves,branches,fine roots and litter decreased first and then increased with the increase of latitude.The phosphorus content of leaves,transport fine-roots and litters increased with latitude.N:P of leaves and fine roots decreased first and then increased,while litter N:P showed a decreasing trend with latitude.Second,the N-resorption efficiency,N-enrichment factor,N-transfer factor(I),and N-transfer factor(II)ranged from 0.50 to 0.65,19.86-61.03,0.76-1.25,and 2.59-4.76,respectively.The P-resorption efficiency,P-enrichment factor,P-transfer factor(I),and P-transfer factor(II)ranged from 0.47-0.70,24.80-246.57,0.53-1.19,and 3.12-4.04,respectively.N-resorption efficiency increased with increasing latitude.N-transfer factor(II),P-resorption efficiency,and P-enrichment factor all increased first and then decreased with increasing latitude.P-transfer factor(I)decreased first and then increased with increasing latitude.Thirdly,structural equation modeling(SEM)analysis showed that N and P stoichiometry of organs and litters of Q.acutissima could be explained by 74.2%-91.3% of environmental factors such as annual mean temperature and mean annual precipitation,and biological factors such as tree height and diameter at breast height,which were mainly affected by environmental factors and less affected by biological factors.Among them,the N stoichiometry of organs and litters were mainly affected by water.The P stoichiometry of organs were mainly controlled by temperature and precipitation,while P stoichiometry of litters were mainly controlled by precipitation.Fourth,SEM analysis showed that the N and P nutrient cycling characteristics of Q.acutissima could be explained by 91.3%-99.4% of the environmental factors such as annual mean temperature and mean annual precipitation,and biological factors such as plant stoichiometry,tree height and diameter at breast height,which were mainly affected by biological factors such as organs and litters stoichiometry,and were also affected by environmental factors to some extent.