玉龙雪山及周边地区植被水分利用效率时空动态及其对scPDSI的响应

Spatiotemporal variation of water use efficiency in response to self⁃calibrating Palmer drought severity in⁃dex in Yulong Snow Mountain and surrounding areas,China

玉龙雪山及周边地区是典型的季风海洋性冰川区,是研究冰川变化、地-气能量交换、植被群落演替以及生态系统碳水耦合的最重要的区域。水分利用效率(water use efficiency,WUE)是联系生态系统水-碳循环及其与气候因子之间响应关系的重要参数。本研究利用MODIS卫星遥感总初级生产力(gross primary productivity,GPP)、蒸散发(evapotranspiration,ET)产品和自适应帕尔默干旱指数(self-calibrating Palmer drought severity index,scPDSI)分析了2000—2020年玉龙雪山及周边地区植被WUE空间变化特征,研究了该区GPP、ET、WUE与scPDSI的相关性,探讨了该区不同地貌植被对水分利用及胁迫的适应策略。结果表明:2000—2020年,研究区植被WUE平均值为2.44 g C·m^(-2)·mm^(-1),GPP平均值为1365.0 g C·m^(-2),ET平均值为559.6 mm;WUE平均值最高区域分布在大起伏中山,为2.88 g C·m^(-2)·mm^(-1);最低区域为大起伏极高山,为1.23 g C·m^(-2)·mm^(-1)。玉龙雪山地势起伏大,植被空间分布具有显著垂直地带性特征,植被WUE在3500 m以下区域随海拔上升而增加,3500 m以上则随海拔上升而减少。2000—2020年,研究区逐月WUE呈现增加—减少—增加趋势,不同地貌类型造就了植被WUE变化速率具有显著的差异性特征。玉龙雪山以及周边大起伏高山的植被WUE呈增长趋势,而中海拔平原呈减少趋势。研究区内植被WUE对干旱胁迫响应具有明显的季节性特征,WUE与scPDSI的多年逐月相关性呈现负相关—正相关—负相关—正相关的变化趋势。7月玉龙雪山WUE与scPDSI呈显著正相关,而5月则表现为显著负相关;玉龙雪山周边地区植被WUE与scPDSI在12月—次年6月呈负相关,在7—8月呈正相关。

Yulong Snow Mountain and its surrounding area a typical monsoon marine⁃like glacier region,which is the most suitable area for studying glacier change,geo⁃air energy exchange,vegetation community succession,and ecosystem carbon⁃water coupling.Water use efficiency(WUE)is an important parameter linking ecosystem water⁃carbon cycle and its response to climate factors.In this study,MODIS satellite remote sensing products[gross pri⁃mary productivity(GPP)and evapotranspiration(ET)]and self⁃calibrating Palmer drought severity index(scPD⁃SI)were used to analyze the spatial variation of WUE in Yulong Snow Mountain and its surrounding area from 2000 to 2020.The relationships between GPP,ET,WUE,and scPDSI were investigated,and the adaptation strategies of vegetations in different landforms to water use and stress were discussed.The results showed that during 2000-2020,the average WUE,GPP,and ET was 2.44 g C·m^(-2)·mm^(-1),1365.0 g C·m^(-2),and 559.6 mm in the study area,respectively.The highest average WUE(2.88 g C·m^(-2)·mm^(-1))was mainly distributed in intermediate relief and sub⁃high altitude mountains,and the lowest average WUE(1.23 g C·m^(-2)·mm^(-1))was distributed in the high relief and extremely high altitude mountains.Due to the undulating terrain of Yulong Snow Mountain and the significant vertical zonal characteristics of vegetation,WUE increased with altitude below 3500 m,while de⁃creased with altitude above 3500 m.During 2000-2020,the monthly WUE presented a trend of increase⁃decrease⁃increase.The change rate of WUE was significantly different due to different geomorphological types.The WUE in large undulating mountains of Yulongxue Mountain and its surrounding area showed an increasing trend,while that of the middle elevation plain showed a decreasing trend.In the whole study area,there were seasonal variations for the response of WUE to drought stress.The monthly correlation between WUE and scPDSI showed a trend of nega⁃tive correlation⁃positive correlation⁃negative correlation⁃positive correlation,respectively.In the Yulong Snow Moun⁃tain area,WUE and scPDSI showed a significant positive correlation in July,but a negative correlation in May.There was a negative correlation between WUE and scPDSI from December to June of the following year,and a pos⁃itive correlation between July and August in the area around Yulong Snow Mountain.