2008-2014年植被覆盖变化对黑河流域净初级生产力的影响研究

土地利用/覆被变化是生态系统能量流动与物质循环的主要驱动力之一,土地利用/覆被变化最直观的表现就是植被覆盖度的变化,研究其对植被净初级生产力的影响,对区域土地利用的管理具有重要意义.研究利用MO-DIS反射率及NPP数据,分析了2008-2014年黑河流域植被覆盖度变化及其对NPP的影响.结果表明:(1) 2008-2014年,黑河流域年均NPP呈现上升的趋势,流域NPP总体呈现南多北少,上游地区的祁连山地带、中游地区的张掖、酒泉、临泽等地NPP值普遍较高,除沿河道外,下游NPP值普遍较低,并且在下游的北部地区NPP值达到了最低.(2)相比2008年、2014年黑河流域Ⅰ级(盖度小于20％)、Ⅳ级(盖度介于40％～60％)和Ⅴ级(盖度大于60％)植被覆盖等级所占比例有所上升,而Ⅱ级(盖度介于20％ ～30％)和Ⅲ级(盖度介于30％～40％)比例下降,影响该流域植被生长的主导性因子不同,上游地区主要受降水影响,下游受气温影响较大.(3)植被覆盖度对NPP的产量具有很好的指示作用,二者的决定系数高达0.90,NPP产量随植被覆盖度的增大而增加.(4) 2008-2014年,黑河流域NPP总量由6 052.82 GgC/a增加为6 624.54 GgC/a,增加幅度为9.45％,其中,面积减少17 086 km2的低植被覆盖区NPP总量减少仅为25.65 GgC/a,而高植被覆盖度区增加最多,从2 861.96 GgC/a增加为3 206.86 GgC/a,增加量为344.90 GgC/a,较高植被覆盖度区的NPP总量增加次多,增加了251.84 GgC/a,增幅为12.57％.

Effects of Vegetation Coverage Change on Net Primary Productivity of Heihe River Basin During 2008-2014

Land use and cover change (LUCC) is one of the main factors that affect material circulations and energy flows in ecosystems.The change of vegetation coverage can reflect the LUCC,studies on how vegetation coverage change influences net primary productivity (NPP) are necessary for science-based planning of regional land use.Based on data of MODIS-Reflectance and MODIS-NPP from 2008 to 2014,the impacts of vegetation coverage change on NPP in Heihe River Basin were assessed.The main findings are:(1) the vegetation coverage in Heihe River Basin got the rise trend in 2008-2014;spatially,NPP on the south side of the river was more than that on the north side,and the NPP on Qilian Mountains and Zhangye City,Jiuquan City,Linze City were higher as compared to downstream area,and the NPP value reached the lowest in the northern downstream area;(2) compared to 2008,vegetation coverage of grade 1(coverage below 20％),grade 4(coverage between 40％ and 60％),and grade 5(coverage above 60％) got the rise,while grade 2 (coverage between 20％ and 30％) and grade 3(coverage between 30％ and 40％) got the reduction in 2014;(3) correlation-analysis showed that the vegetation coverage had the good indication of NPP,i.e.,the correlation coefficient is more than 0.90;(4) during the period from 2008 to 2014,regional annual primary production increased from 6 052.82 GgC/a to 6 624.54 GgC/a,with the increase of 9.45％;the area of vegetation coverage of grade 1 decreased by 17 086 km2,but the total NPP only decreased 25.65 GgC/a;vegetation coverage of grade 5 increased most,and total NPP increased from 2861.96 GgC/a to 3 206.86 GgC/a,with a increase of 344.90 GgC/a(i.e.12.05％),while Vegetation coverage of grade 4 increased 251.84 GgC/a.