布哈河流域土地利用转移矩阵及空间变化研究

布哈河位于青藏高原东北部,是青海湖最大的补给河流。该流域属于典型的生态脆弱区,是气候变化响应最敏感区域之一。为此运用土地利用转移矩阵和土地利用变化信息变量分析方法,研究了该流域土地利用类型转移规律,分析了引起变化的原因,为青海湖流域未来气候变化情景下下垫面变化引起径流变化的研究提供参考。结果表明,1980年代至2014年流域土地利用类型增加量主要发生在高中低三种不同覆盖度草地,减少量主要表现在未利用地。总变化中将近一半发生了数量上绝对值的变化,另一半发生了空间位置转移。低盖度草地和未利用地以净变化量为主,而中盖度草地与高盖度草地均以交变化量为主。空间转移分析表明,流域西北部海拔3 900 m以上源头区属无人区,受温度升高降水增加全球气候变化影响,源头区植被增加响应明显。而在海拔3 900 m以下区域,植被盖度增加类型分布较分散,整体受气候变化自然因素影响,局部在人类集中分布区域受放牧等人为干扰影响大,为植被减少类型。

Study on land-use transition matrix and spatial changes of Buha River Basin

Buha River is located in the northeast part of Qinghai-Tibet Plateau，which is the largest feeding river of Qinghai Lake. The basin of the river not only belongs to a typical eco-fragile region，but also is one of the most sensitive areas responding to the climate change. With the land-use transition matrix and the information variable analysis method for land-use，the law of the land-use transition of the river basin is studied herein along with the analysis made on the causations of the changes，so as to provide references for studying the runoff variation caused by the underlying surface changes under the scenario of the future climate changes within Qinghaihu Lake Basin. The result shows that the increments of the types of the land-use in the river basin from 1980 to 2014 mainly occur at the grasslands with high，medium and low grass-coverages，while the decrements mainly appear at the unused lands. Among the total variation，the absolute value of near half of it is quantitatively changed，and that the spatial location transition occurs for the other half. The net variations mainly occur at the grasslands with low grass-coverage and the unused lands，meanwhile，the alternating variations mainly appear at the gasslands with both the high and the medium grass-coverages. Moreover，the sptial transition analysis shows that the source area above El. 3 900 m at the northwest of the river basin belongs to a depopulated zone and is under the impact from the global climate change of temperature rise and precipitation increase with the obvious responding to the increase of the vegetation of the source area. However，the increasing types of the vegetation coverages are more dispersedly distributed in the area under El. 3 900 m，which is wholly under the impact from the natural factors of the climate changes，while a part of it is the concentrated distribution area of human and is under the larger impact from the human interferences，such as grazing，etc.，which belongs to the vegetation decreasing type.