Temporal And Spatial Evolution Characteristics Of Plant Functional Traits And Environmental Factors In Masson Pine Forests In Central Guizho

As a bridge between plants and the environment,plant functional traits(PFTs)reflect their response to the environment.Therefore,studying the relationship between PFTs and environmental factors can help us understand the coordinated development of plants and the environment during their growth and development.In this study,we selected the Pinus massoniana(PM)forest in the subtropical karst mountains at different temporal(stand age)and spatial(altitudinal gradient)scales as the research object.The theory and methods of functional ecology,ecological stoichiometry,soil science and community ecology were applied to analyze the relationship between the leaf and root traits of plants and environmental factors.The spatial and temporal distribution characteristics of the functional traits of PM forest plants and their influencing factors were revealed.This study provides a scientific theoretical basis and practical guidance for the protection and rational management of subtropical mountain forest ecosystems.The main research results are as follows:(1)The Simpson index,Shannon-wiener index,Margalef index and Pielou index of herbaceous layer of PM forest at different altitudinal gradient showed a significant decrease,while only the Pielou index of shrub layer was significantly different among different altitude sample sites,and in general,each diversity index of shrub layer was higher than that of herbaceous layer,but the difference was not significant.The soil properties of the PM forest at different elevations were significantly different,and showed that the soil properties of the topsoil(0-20 cm)were significantly higher than those of the subsoil(20-40 cm),indicating that the soil of the PM forest has an obvious "phenology effect";at the same time,the soil properties of the topsoil and the subsoil showed the same trend with elevation;among them,along the altitudinal gradient,the soil moisture content(SMC),soil sand content(Sand)and soil carbon to nitrogen ratio(SCNr)showed a significant increasing trend,while soil bulk density(SBD),soil clay content(Clay)and soil silt content(Silt)showed a significant decreasing trend,and soil nitrogen to phosphorus ratio(SNPr)and soil effective phosphorus content(AP)showed an increasing and then decreasing trend,while p H,soil organic carbon content(SOC),soil total nitrogen content(TN)and soil total phosphorus content(TP),soil effective nitrogen(AN),soil effective potassium(AK),soil exchangeable calcium(e Ca)and soil exchangeable magnesium(e Mg)showed a decreasing trend followed by an increasing trend.(2)In the PM forests with different altitude gradients,the PFTs are significantly different at different altitudes,and the change trends of each trait index along the altitude are not consistent,which indicates that the plants in the PM forest form a synergy and trade-off of multiple traits in response to environmental variability across the altitude gradient;among them,the leaf traits of PM and shrub layer at high altitude tended to have a low investment-high return strategy(acquisition strategy),and the root traits of PM tended to have a high investment-low return strategy(conservative strategy),while the leaf and root traits of low altitude tended to have a conservative and acquisition strategy,respectively.At the same time,there are significant differences among the PFTs indicators of different growth types and their trends with altitude,indicating that there is a trade-off between the PFTs of different growth types in resource extraction strategies in the PM forest,with herbaceous and shrub layer plants preferring acquisition strategies and tree layer(PM)preferring acquisition strategies.(3)In addition to the leaf traits of shrub,the PFTs of other plants in the PM forest were significantly different among different stand ages,and the change trends of the functional traits of each plant were significantly different with the stand age;the leaf traits of herbaceous plants,the root traits of PM and non-PM(the shrubs and herbaceous root)were different in resource utilization strategies in different stand age plots;PFTs were significantly different among plants of different growth types,and there were significant differences between shrub layer and herbaceous layer plants.There were different resource utilization strategies,among which,herbaceous leaves and underground non-PM roots tended to acquire strategies,while shrub leaves and PM roots tended to conserve strategies.(4)Soil chemical properties(SOC,TN,TP,SCNr,SNPr,AN,AP,AK,e Ca,and e Mg)are important environmental factors that affect the functional traits of plants in subtropical PM forests at different temporal and spatial scales;among them,PM and shrubs and the leaf traits of herbs are mainly affected by nutrients such as C,N,and P,while the root traits of PM and non-PM are affected by a variety of soil chemical properties.