1982—2016年广西NDVI时空变化及其影响因素

Spatial-Temporal Changes of NDVI and Its Influence Factors in Guangxi,China During 1982—2016

植被变化及其与驱动因素的关系研究是开展大规模植被恢复效益评估以及进一步生态建设的重要基础,而目前对喀斯特地区植被时空变化及其影响因素的认识仍不明晰。以广西为例,基于NDVI、气温、降雨和DEM数据,利用最大值合成、线性趋势分析、统计降尺度和偏相关分析法,对1982—2016年广西NDVI时空变化及其影响因素进行分析。结果表明:(1)1982—2016年广西多年平均NDVI为0.53,年NDVI呈波动增长趋势,变化率为0.013/10a。广西植被覆盖呈南部、东部向中部、西部和西北部递减的空间分异特征,非喀斯特区的植被覆盖高于峰丛洼地和峰林平原区,高海拔地区的植被覆盖低于低海拔地区,高植被覆盖主要分布在坡度为0°~10°、>40°的南坡和东南坡;(2)非喀斯特区的NDVI增加趋势明显,峰林平原的NDVI出现下降趋势。随着坡度的增加,植被改善越明显。不同坡度和坡向的植被覆盖变化存在差异,但植被改善区所占面积比例均大于退化区;(3)广西多年平均气温为20℃,变化率为0.255℃/10a,呈南向北递减的空间分布特征。多年平均降雨量为1508 mm,变化率为22.43 mm/10a,呈南部、东部向西北部递减的空间分布特征。NDVI、降雨量和气温在不同季节均表现为:夏季>春季>秋季>冬季;(4)NDVI受气温的影响程度强于降雨,尤其与冬季气温具有较强的正相关关系,与夏季降雨具有不显著的负相关关系。峰丛洼地的NDVI与降雨呈明显的负相关,峰林平原的NDVI与气温呈明显的正相关。研究结果为喀斯特地区生态环境建设和植被恢复提供理论基础和科学依据。

Research on the relationship of vegetation changes and its driving factors is vital for evaluating the effects of large scale vegetation restoration and ecological construction.However,this relationship is still unclear in the karst region.Based on long time series of NDVI data,temperature,precipitation and DEM data,the methods of maximum synthesis,linear regression analysis,statistical down-scaling and partial correlation analysis method were used to analyze the spatial-temporal changes of NDVI and its influence factors in Guangxi during 1982—2016.The results indicat that:(1)The annual NDVI was 0.53,with an increasing rate of 0.013/10a.The vegetation cover showed a high spatial variation in the study area,decreasing from the south and the east areas to the middle,the west and the northwest areas.In addition,the vegetation cover was slightly higher in the non-karst region than that in the peak cluster depression and peak forest plain,and it decreased from high elevation area to low elevation area.High vegetation cover area was mainly distributed in the south slope and southeast slope of 0°~10°and>40°.(2)The NDVI increased obviously in non-karst,while it decreased in the peak-forest plain.With the increase of slope gradient,the increasing trend of vegetation cover became more obvious.There were differences in vegetation cover with different slope and aspect,but overall the vegetation improvement areas were larger than the degradation ones.(3)The annual average temperature was 20℃,with a variation rate of 0.255℃/10a during 1982—2016.The annual temperature showed a high spatial variation,generally decreasing from the south area to the north area.The annual average precipitation was 1508 mm,with a variation rate of 22.43 mm/10a during 1982—2016.The annual average precipitation generally decreased from the south and east area to the north and west area.For different seasons,the NDVI,temperature and precipitation generally followed an order as:summer>spring>autumn>winter;(4)NDVI was more affected by temperature than precipitation,especially strong positive correlation with temperature in winter and no significant negative correlation with precipitation in summer.The NDVI was negatively correlated with precipitation in the peak cluster depression,and was positively correlated with temperature in the peak forest plain.The results of this study can provide theoretical and scientific basis for ecological environmental construction and vegetation restoration in karst areas.