Ecological Stoichiometry And Nutrient Resorption Of Castanopsis Hystrix Plantations In Lower Subtropics

The industrialization process had accelerated and the urbanization process had intensified since the first industrial revolution began in Britain in the 1860s.The combustion of a large amount of petroleum and fossil energy had caused serious air pollution.In recent years,N deposition phenomenon under the background of global climate change,not only cause heavily influence for air quality degradation,soil acidification,vegetation primary productivity and carbon sinks,but also impact nutrients utilization and resorption of vegetation,plant-soil carbon（C）,nitrogen（N）,and phosphorus（P）stoichiometry.In order to clarify the relationship between the uptake and utilization of plant nutrients and the environment,three influencing factors were selected in this study.One of a kind is climate factors including average annual temperature（MAT）,average annual rainfall（MAP）and sunshine duration（SH）.One of a kind is air environment change factors including sulfur dioxide（SO₂）,nitrogen dioxide（NO₂）,and inhalable particulate matter(PM₁₀,PM_2.5)carbon monoxide（CO）,ozone（O₃）.Another kind is urban population including the number of resident population（RP）.This study took climate change,air quality changes and population changes in plant-soil of Castanopsis hystrix plantation in different regions of Guangdong province as research objects.The research content mainly includes the following three parts:exploring its impact on plant-soil nutrient status,and analyzing the main air environmental quality factors and climate factors and the relationship between the resident population;the main factors and degree of influence on plant-soil nutrients were explored.clarifing the relationship between the main influence factors and influence objects.In order to deep our understanding of the nutrient status of terrestrial ecosystems,especially forest ecosystems.And provided scientific basis for future forest ecosystem forest management and nutrient utilization,in the context of global climate change.The main results of the study were as follows:（1）There was a correlation between air environmental quality factors,climate factors,and the number of residents.O₃ and CO were not significantly different in Lechang,Guangzhou and Zhongshan,while nitrogen dioxide content was significantly different among the three cities and Guangzhou was the highest.There was a correlation between the NO₂ content and climatic factors（annual average rainfall,the annual average temperature,the sunshine duration,and the number of permanent residents）,and there was a significant linearly positive correlation between NO₂ and RP,MAP.There was a significant linearly negative correlation between SO₂ and MAT,SH.O₃ content had significant linearly positive correlation with MAT and SH.（2）The p H,cation exchange capacity（CEC）,C,N,and P stoichiometry of soil in 0-20 cm and 20-40 cm of Castanopsis hystrix plantation in different cities and forest types were significantly different（P<0.05）.With the increase of soil depth,C,N,P,C:N,C:P,N:P of soil all showed a downward trend,while soil p H increased with the depth of 0～20 cm to 20～40cm.（3）The C,N,P ecological stoichiometry of branches-leaves-litter were significantly different,and the N content of leaf-branch-litter in Guangzhou were higher than that in Lechang and Zhongshan.Among them,annual rainfall,resident population,nitrogen dioxide（NO₂）and PM₁₀ were the main factors affected the ecological stoichiometry of C,N,and P in Castanopsis hystrix plantation.P and N:P difference of branch-leaf were greater impacted by NO₂（50.0%,55.0%,and 58.6%,and 58.1%）than soil nutrients（8.5%,7.1%and 2.7%,1.5%）and DBH（41.5%,37.8%and 38.7%,40.4%）.There was a significant linearly negative correlation between NO₂ content and P content of branches and leaves in Castanopsis hystrix plantation,while there was a significant linearly positive correlation between NO₂ content and branch N:P.（4）The nutrient N resorption efficiency was higher than the P resorption efficiency,and the N and P nutrient resorption efficiency had significant linearly positive correlations with leaf N content（P=0.042）and DBH（P=0.039）;respectively.Litter N,C:N and leaves N,C:N had a significant linearly negative correlation,respectively（P=0.027;P=0.006）;litter C,P contents had a significant linearly negative correlation with DBH（P=0.015;P=0.042）.