采用1982-2015年的GLASS-LAI (Global Land Surface Satellite-Leaf Area Index)遥感数据和CRU(Climatic Research Unit)气象数据,利用Mann-Kendall趋势法分析了过去34 a全球9种植被的叶面积指数(Leaf Area Index,LAI)时空变化特征;使...采用1982-2015年的GLASS-LAI (Global Land Surface Satellite-Leaf Area Index)遥感数据和CRU(Climatic Research Unit)气象数据,利用Mann-Kendall趋势法分析了过去34 a全球9种植被的叶面积指数(Leaf Area Index,LAI)时空变化特征;使用相关分析和逐步线性回归分别探讨了全球9种植被LAI与降水、温度的年际与月关系。结果表明:①全球植被总体呈现绿化趋势,其中变化较大的是草原、稀树草原、常绿阔叶林和多树草原;在植被生长的绿化和褐化趋势中,面积占比最大的植被类型均为草原,说明草原生态系统易受环境因素的影响。②从年际关系看,草原和开放灌丛的LAI与年均降水多呈正相关关系,而温度对不同纬度植被的LAI存在正负2种影响。其原因为温度升高对中低纬度的植被生长有抑制作用,而对高纬度地区植被生长有促进作用。③从年内关系看,南半球降水和温度共同作用于植被的生长;而北半球除常绿阔叶林的生长与温度关系更为紧密外,其它类型植被的生长主要受降水影响。④逐步线性回归结果表明,当月温度的升高对常绿阔叶林、混交林和农作物的生长具有促进作用,而多树草原和草原2种植被的生长受当月降水的影响最为显著。展开更多
This paper is concerned with the multidimensional asymptotic stability of V-shaped traveling fronts in the Allen-Cahn equation under spatial decaying initial values.We frst show that V-shaped traveling fronts are asym...This paper is concerned with the multidimensional asymptotic stability of V-shaped traveling fronts in the Allen-Cahn equation under spatial decaying initial values.We frst show that V-shaped traveling fronts are asymptotically stable under the perturbations that decay at infnity.Then we further show that there exists a solution that oscillates permanently between two V-shaped traveling fronts,which indicates that V-shaped traveling fronts are not always asymptotically stable under general bounded perturbations.Our main technique is the supersolutions and subsolutions method coupled with the comparison principle.展开更多
This paper is concerned with entire solutions ( t ∈ R) for bistable reaction-advection-diffusion equations in heterogeneous media. By using traveling curved fronts connecting a constant unstable stationary state and ...This paper is concerned with entire solutions ( t ∈ R) for bistable reaction-advection-diffusion equations in heterogeneous media. By using traveling curved fronts connecting a constant unstable stationary state and a stable stationary state, we proved that there exist entire solutions behaving as two traveling curved fronts coming from opposite directions, and approaching each other. Furthermore, we prove that such an entire solution is unique and Liapunov stable. The key technique is to characterize the asymptotic behavior of solutions at infinity in term of appropriate subsolutions and supersolutions.展开更多
文摘采用1982-2015年的GLASS-LAI (Global Land Surface Satellite-Leaf Area Index)遥感数据和CRU(Climatic Research Unit)气象数据,利用Mann-Kendall趋势法分析了过去34 a全球9种植被的叶面积指数(Leaf Area Index,LAI)时空变化特征;使用相关分析和逐步线性回归分别探讨了全球9种植被LAI与降水、温度的年际与月关系。结果表明:①全球植被总体呈现绿化趋势,其中变化较大的是草原、稀树草原、常绿阔叶林和多树草原;在植被生长的绿化和褐化趋势中,面积占比最大的植被类型均为草原,说明草原生态系统易受环境因素的影响。②从年际关系看,草原和开放灌丛的LAI与年均降水多呈正相关关系,而温度对不同纬度植被的LAI存在正负2种影响。其原因为温度升高对中低纬度的植被生长有抑制作用,而对高纬度地区植被生长有促进作用。③从年内关系看,南半球降水和温度共同作用于植被的生长;而北半球除常绿阔叶林的生长与温度关系更为紧密外,其它类型植被的生长主要受降水影响。④逐步线性回归结果表明,当月温度的升高对常绿阔叶林、混交林和农作物的生长具有促进作用,而多树草原和草原2种植被的生长受当月降水的影响最为显著。
基金supported by National Natural Science Foundation of China(Grant Nos.11031003,11271172 and 11071105)the Fundamental Research Funds for the Central Universities(Grant No.HIT.NSRIF.2014063)+2 种基金China Postdoctoral Science Foundation Funded Project(Grant No.2012M520716)Heilongjiang Postdoctoral Fund(Grant No.LBH-Z12135)New Century Excellent Talents in University(Grant No.NCET-10-0470)
文摘This paper is concerned with the multidimensional asymptotic stability of V-shaped traveling fronts in the Allen-Cahn equation under spatial decaying initial values.We frst show that V-shaped traveling fronts are asymptotically stable under the perturbations that decay at infnity.Then we further show that there exists a solution that oscillates permanently between two V-shaped traveling fronts,which indicates that V-shaped traveling fronts are not always asymptotically stable under general bounded perturbations.Our main technique is the supersolutions and subsolutions method coupled with the comparison principle.
基金supported by National Natural Science Foundation of China(Grant No. 10871085)
文摘This paper is concerned with entire solutions ( t ∈ R) for bistable reaction-advection-diffusion equations in heterogeneous media. By using traveling curved fronts connecting a constant unstable stationary state and a stable stationary state, we proved that there exist entire solutions behaving as two traveling curved fronts coming from opposite directions, and approaching each other. Furthermore, we prove that such an entire solution is unique and Liapunov stable. The key technique is to characterize the asymptotic behavior of solutions at infinity in term of appropriate subsolutions and supersolutions.
