Ecological Environment Change in North Slope of Qilianshan Mountains

Based on meteorological,hydrological, forest,and grassland data collected by location observation,remote sensing,field surveys and relevant literature during 1956 to 2009,the ecological environment change in northern slope of the Qilianshan Mountains was analyzed synthetically using regression and correlation analyses.The results showed that the temperature had an annual variation rate of 0.033 4℃·a-1 in northern slope of the Qilianshan Mountains since 1960,and exhibited a raising trend,especially since 1987.The annual variation rate of annual precipitation was 0.570 2 mm·a-1,indicating that the precipitation tended to increase.The climate had changed from arid to humid in this region since 1976.From 1956 to 2006,the glacier area of six inland river basin（Shiyanghe river,Heihe river, Beidahe river,Shulehe river,Danghe river and Halternhe river） and Datonghe river basin in northern slope of Qilianshan mountains decreased by 17.7%. Thickness of the glacier reduced about 5-20 m,and the snow line rose about 100-140 m.The Glacier ice reserves in inland river basin of Hexi decreased by 11.4%.From 1972 to 2007,27 glaciers in the eastern section of the Qilianshan Mountains disappeared.From 1956 to 2009,the runoff change in the northern slope of the Qilianshan Mountains was different in different regions.The runoff was reduced significantly in Shiyanghe river basin, increased slightly in Heihe river basin,and increased obviously in Shulehe river basin.From 1958 to 1988, the area of deforestation and farming was more than 10.0 million ha,and the forest area was reduced 0.6 million ha.Since the Qilianshan Mountain Nature Reserve was established in 1989, the forest was restoring gradually because of continual protection and cultivating,and the forest area was increased 9.4 million ha from 1989 to 2008. Due to human interference,especially over-grazing impact,the quality of the wood-land,shrub-land and grass-land in northern slope of the Qilianshan Mountains were in a degraded condition,which resulted in serious harm of forest pests,decrease of shrubbery snow and water-retention capacity and exacerbation of soil erosion.The ecological environment in northern slope of the Qilianshan Mountains was improved in certain regions,but deteriorated in overall region,and the protection and management are needed to be strengthened.

近30年祁连山南坡降水量变化特征分析

祁连山南坡地区作为西北干旱区重要的水源涵养区,其生态地位十分重要,而降水的变化直接关系到祁连山南坡水源涵养量的变化,甚至可以改变祁连山南坡的生态环境。因此,研究祁连山南坡降水量变化特征具有重要的社会和科学意义。利用1986—2015年祁连山南坡祁连、野牛沟、托勒和门源4个气象台站逐月降水量数据,通过降水年内分配特征、年际变化特征、汛期降水量特征和降水量季节变化特征4个方面,对祁连山南坡降水量变化特征进行了综合分析。结果表明:研究区各站近30年平均降水量分别为422.7 mm,434.3 mm,312.7 mm和524.1 mm,祁连气象站、野牛沟气象站和托勒气象站均在1998年出现降水量极大值,与全国降水时间分布规律一致,各站降水量年际变化不大,变差系数为0.14～0.18;研究区降水年内分配极不均匀,10月至次年4月降水量偏少,5—9月降水量较多;汛期降水量与全年降水量具有较大的一致性和良好的线性相关关系,相关系数均大于0.9;研究区内各站降水量主要集中在夏季,但变化趋势不同,其中祁连、野牛沟和托勒气象站降水量为增加趋势,门源气象站降水量为减少趋势。

祁连山北坡的生态环境变化

利用1956—2009年祁连山北坡定位观测、遥感监测和实地调查的气象、水文、森林、草原资料及相关文献,采用回归与对比分析相结合的方法,综合分析祁连山北坡生态环境变化。结果表明:1960年以来,祁连山北坡年气温的年际变化率为0.0334℃·a-1,气温呈上升趋势,特别是1987年以后气候明显变暖;年降水量的年际变化率为0.5702mm·a-1,降水量呈增加趋势,但增加趋势不太明显,在1976年气候由干旱向湿润转变;1956—2006年,祁连山北坡石羊河、黑河、北大河、疏勒河、党河和哈尔腾6个内流区河流域及大通河流域冰川面积减少17.7%,冰川厚度减薄5～20m,雪线上升100～140m,河西内流区冰川冰储量减少11.4%;东段冷龙岭有27条冰川在1972—2007年的35年间消失;1956—2009年,祁连山北坡出山径流变化存在一定的区域差异,石羊河流域出山径流呈明显减少趋势,黑河流域略有增加,疏勒河流域增加趋势明显;1958—1988年间,祁连山北坡毁林草开荒面积达10.0万多hm2;1958—1980年,森林面积减少0.6万hm2;1989年祁连山自然保护区建立以来,不断加强保护培育,森林逐步恢复,至2008年有林地面积较1989年增加9.4万hm2;因受人为干扰特别是超载放牧影响,1958年以来,祁连山北坡有林地、灌木林及草原的质量一直处于退化状态,致使森林病虫危害严重,灌木林积雪和保水能力下降,草地产草量降低,水土流失加剧。祁连山北坡生态环境仍处于局部改善、总体恶化状况,亟待加强保护与治理。

1980-2018年祁连山南坡土地利用地形梯度变化及其地形因子地理探测

为了研究不同地形梯度上土地利用时空变化规律,基于1980—2018年5期遥感影像数据,利用ArcGIS 10.2分析祁连山南坡不同海拔、坡度和坡向土地利用时空格局变化规律。结果表明:祁连山南坡土地利用主体类型为草地。耕地和建设用地主要分布在2700~3200 m、<5°、阳坡和半阳坡的门源盆地;林地、草地和海拔、坡度、坡向关系密切;建设用地受海拔和坡度影响大;未利用土地受海拔影响明显。在海拔2700~3200 m、坡度<5°、西南坡、南坡区域耕地、建设用地增加最多,未利用土地在海拔4200~4700 m、坡度30°~35°、西南坡、南坡和东北坡区域增加最多;林地、草地、水域分别在3700~4200 m,2700~3200 m,4200~4700 m区域减少最多,坡度<5°的区域草地减少最多,林地、草地、水域分别在北坡、西南坡和东北坡减少最多。地形因子对土地利用程度的影响由大到小依次为海拔、坡度和坡向,海拔和坡度、海拔和坡向对土地利用程度影响大。不同地形梯度下土地利用变化表现出明显的时空差异规律。