Understanding the impact of rock bareness on the transpiration in karst plants is essential to karst rocky desertification control and sustainable management of plantation in karst area.This study focused on the variations in sap flow of Zenia insignis caused by different rock bareness rate,and the impact of climate factors,soil water content(SWC)and leaf area index(LAI) on transpiration in karst plants,by continuously measuring sap flux densities (Fcd)of 12 sample trees using thermal dissipation probes and monitoring micrometeorology and SwC on a typical karst hill in north Guangdong of China during the year of 2016.Results show that:(1)the maximum hourly sap flux density occurred at11:00-14:00 and the peak daily sap flux density occurred in September.(2)Sap flow density of Zenia insignis increased with rock bareness rate at all hourly,daily and monthly scales,with the sequence of extremely severe>severe>moderate>mild rock bareness.(3)The transpiration of Zenia insi.gnis is controlled by different factors at different temporalscales.At hourly scale,transpiration was highly(n=144,R^2>0.72)correlated to Solar radiation(Rs),Air temperature(Ta),relative humidity(RH),and water vapor pressure deficit(VPD).At daily scale,transpiration was greatly(n=366,R2>0.31)affected by Solar radiation(Rs),Air temperature(Ta),and water vapor pressure deficit (VPD).While at monthly scale,transpiration was mainly(n=12,R^2=0.85)controlled by LAI.Our study proved that Zenia insi.gnis has a good physiecological adaption to fragile karst environment,and Zenia insignis plantation has long-term sustainability even in extremely rocky landscapes.The results may provide scientific basis for plantation management and ecological restoration in karst area.
LI Hui-xiaZHOU Hong-yiWEI Xing-huLU NanLIANG Zhao-xiong
以MOD17A3数据集为基础数据,结合地理信息系统(geographic information system,GIS)技术与统计方法,采用线性回归方程斜率方法分析广西壮族自治区(简称桂)西北植被生产力的时空变化特征。结果表明:(1)近10多年,研究区植被生产力呈现出稳中略降的趋势,陆地植被净初级生产力(net primary productivity,NPP)最大值出现在2007年,此后出现较明显的下降趋势;(2)在空间上,植被NPP表现出西北高、东南低的分布格局,相反,NPP变化斜率呈现出西北低、东南高的分布特征;(3)NPP变化斜率随高程上升而递减,峰丛洼地NPP负增长趋势最为明显;(4)NPP变化随土地利用类型存在较大分异,林地NPP负增长趋势明显,耕地NPP则呈正增长趋势。
