典型小流域喀斯特石漠化演变特征及其关键表征因子与驱动因素

中国西南喀斯特区域土地石漠化生态灾难已经严重制约了经济和社会的发展,而对石漠化进行治理,其空间分布信息的准确提取是必不可少的。针对现有石漠化信息提取技术存在不可能发生喀斯特石漠化(Impossible to develop karst rocky desertification,IKRD)范围提取不准确,关于石漠化的时空演变分析较少及其驱动因子、表征因子繁杂等问题,本文以典型喀斯特流域后寨河流域为研究对象,基于高精度影像识别提取IKRD范围,利用植被覆盖度、岩石裸露率对研究区域准确提取石漠化信息,揭示该区域不同石漠化等级的时空演变规律,同时探明石漠化分布与地表反照率、坡度的相关性。研究结果表明:(1)2005年至2010年后寨河流域石漠化程度整体在恶化,在后寨河流域西南部分和中部极少区域石漠化程度有所减轻,其余区域基本未发生变化,而在2010年至2015年后寨河流域石漠化程度大部分区域都呈减轻状态,而且石漠化程度减轻强度较大,在南侧大部分区域石漠化程度都呈减轻状态,且强度较大。(2)2005年至2010年后寨河流域石漠化程度减轻、未发生变化以及加重的面积分别为4.23 km~2、25.736 km~2、20.81 km~2,各部分面积占比分别为8.3%、 50.7%、41%。(3)2010年至2015年后寨河流域石漠化程度减轻、未发生变化以及加重的面积分别为31.87 km~2、16.57 km~2、6.85 km~2,各部分面积占比分别为57.6%、30%、 12.4%。(4)石漠化区域的坡度、地表反照率主要集中在2°—22°、0.12—0.21之间,而且随着坡度值的增加,潜在石漠化、重度石漠化面积占比增高,轻度石漠化和中度石漠化面积占比降低,随着地表反照率增加潜在石漠化、轻度石漠化面积占比增高,重度石漠化面积占比降低。综上所述,在2005年至2015年间,后寨河流域石漠化演变因贵州省2008年至2010年开始实施退耕还林还草等石漠化综合治理工程而呈现先恶化,后减轻的状态,同时通过对该区域石漠化分布与地表反照率、坡度的相关分析发现,地表反照率和坡度可以作为石漠化研究的辅助表征因子和驱动因子。

Evolution characteristics of karst rocky desertification in typical small watershed and the key characterization factor and driving factor

The ecological disaster of karst rocky desertification in the karst area of southwestern China has severely restricted the economic and social development. To control karst rocky desertification, accurate extraction of its spatial distribution information is indispensable. We consider the problems of inaccurate extraction of impossible to develop karst rocky desertification (IKRD) range, less analysis of the temporal and spatial evolution of karst rocky desertification, complicated driving factors and characterization factors, which exist in the existing technology of karst rocky desertification information extraction. This paper takes the typical karst basin-Houzhai River Basin as the research area. We extracted IKRD range based on high resolution image and using fractional vegetation coverage and rock exposure rate to accurately extract karst rocky desertification information from the study area. We want to reveal the evolution law of different karst rocky desertification levels in this area, and prove the correlation between the distribution of karst rocky desertification and the distribution of surface albedo and slope. The results showed that:(1) from 2005 to 2010, the karst rocky desertification of Houzhai River Basin as a whole has deteriorated. Few central parts of the southwestern has been alleviated, while the rest of the area has not changed. However, most areas of karst rocky desertification in the Houzhai River Basin have been alleviated from 2010 to 2015, and the degree of karst rocky desertification has been reduced significantly, which was more evident in most areas of the southern part in the Houzhai River, and the intensity was relatively high. (2) From 2005 to 2010, the area of karst rocky desertification with alleviated, unchanged, and aggravated were 4.23 km², 25.74 km² and 20.81 km², accounting for about 8.3%, 50.7%, and 41.0%, respectively. (3) From 2010 to 2015, the area of karst rocky desertification with alleviated, unchanged, and aggravated were 31.87 km², 16.57 km² and 6.85 km², accounting for about 57.6%, 30.0% and 12.4%, respectively. (4) The slope and surface albedo of karst rocky desertification area were mainly concentrated between 2°-22° and 0.12-0.21. With the increase of slope, the proportion of potential karst rocky desertification, and severe karst rocky desertification increases, the proportion of light karst rocky desertification and moderate karst rocky desertification decreased. With the increase of surface albedo, the proportion of potential karst rocky desertification and light karst rocky desertification increased, and the proportion of severe karst rocky desertification decreased. In summary, from 2005 to 2015, the evolution of karst rocky desertification in Houzhai River Basin was firstly deteriorated and then alleviated due to the implementation of comprehensive karst rocky desertification control projects such as returning farmland to forests and grasslands in Guizhou Province from 2008 to 2010. At the same time, the correlation analysis between the distribution of karst rocky desertification and the distribution of the surface albedo slope showed that the surface albedo and slope could be used as auxiliary characterization factors and driving factors to karst rocky desertification research.