近20年甘肃省临夏州植被覆盖度的时空变化及其影响因素

Spatio-temporal changes and influence factors of fractional vegetation coverage during the past 20 years in Linxia Prefecture of Gansu Province

植被是连接土壤、大气和水等生态要素的纽带,探索植被覆盖度(fractional vegetation cover,FVC)动态是了解植被现状和预测未来变化的重要过程。寒旱山区由于生长的树种相对单一,群落结构简单,导致森林生态服务功能极不稳定,往往面临着植被退化的问题。因此,本文以甘肃省临夏回族自治州(临夏州)为例,基于2000—2019年的Landsat-5/8影像,结合像元二分模型、普通最小二乘法、Pearson相关回归等多种方法,深入探讨了寒旱山区FVC的时空变化特征及其相关影响因素。结果表明:①从2000年到2019年,研究区FVC呈波动增长趋势,线性增长率为0.0311/a,R^(2)为0.88。FVC主要从低、中低覆盖度向中、中高和高覆盖度转变,空间上呈现出由西南向东北递减的变化趋势。②植被改善地区主要集中在中部偏南区域且由东向西逐渐递减,植被退化的区域零星分布在各个地区。③不同海拔、坡度和坡向条件下的FVC变化存在明显差异,海拔2200~2400 m、坡度10°~15°及阴坡地区的FVC面积显著改善。④研究区60.24%区域FVC变化为非气候因子驱动,39.76%区域由气候因子驱动,其中气温是影响FVC变化的主要驱动因子。FVC变化受气温、降水作用以及气温和降水共同作用(p<0.05)的面积比例分别为38.62%、26.65%、39.76%。

Vegetation is the link that connects soil,atmosphere,water and other ecological elements.Exploring the changes of fractional vegetation coverage(FVC)is an important process for understanding the current status and predicting future changes of vegetation.Due to the relatively distinct tree species and simple community structure in the cold and arid mountainous areas,the forest ecological service function is extremely unstable,which often faces the challenges of severe vegetation degradation.Therefore,taking Linxia Hui Autonomous Prefecture(Linxia)in Gansu Province as an example,based on Landsat-5/8 images from 2000 to 2019,combined with the pixel binary model,ordinary least squares method,Pearson correlation regression,etc.,we thoroughly discussed the FVC spatio-temporal pattern and related influencing factors in cold and arid mountainous areas.Results show that:①From 2000 to 2019,FVC showed a trend of fluctuating growth,with a linear growth rate of 0.0311/a and an R^(2) of 0.88.FVC mainly changed from low,medium-low level to medium,medium-high,and high coverage level,showing a decreasing trend from southwest to northeast.②The improved vegetation areas in Linxia are mainly concentrated in the south-central part and gradually decrease from east to west,and the areas of degraded vegetation are sporadically distributed in the study area.③There were significant differences in FVC changes under different altitudes,slopes and aspect conditions.The FVC area in areas with altitudes of 2200~2400 m,slopes of 10°~15°and shady slopes had been significantly improved.④FVC changes in 60.24%of the study srea were driven by non-climate factors,while 39.76%were driven by climatic factors,of which temperature was the main driving factor affecting FVC changes.And the area ratios of FVC changes affected by temperature,precipitation,and the combined affects of the two(p<0.05)were 38.62%,26.65%,and 39.76%,respectively.