不同石漠化程度岩溶峰丛洼地系统景观格局的比较

利用花江岩溶峡谷区南坡不同石漠化程度的5个独立的岩溶峰丛洼地系统景观要素的实测数据,分析了多样性、优势度、破碎度、分离度等景观格局指标的变化规律及其所指示的生态学意义。结果表明,这些指标在不同峰丛洼地系统都能较好地评价石漠化过程中景观格局的动态变化规律,对分析石漠化土地的发展趋势具有较好的指示意义。但多样性指数、优势度指数、均匀度指数也与各峰丛洼地系统的景观基质有关,在不同石漠化程度的峰丛洼地系统中,反映的景观生态意义是不一样的。景观格局分析不仅强调面积,而且还考虑所研究石漠化土地的空间分布特征(格局)、景观组成特点与石漠化过程的关系和对石漠化的影响,在石漠化程度判定和石漠化指标的研究中景观格局是一个不可忽视的问题。

A comparative researches on landscape pattern changesin different rock desertification peak cluster-depressions

Karst rocky desertification is a kind of land degradation which has happened in fragile karst mountain ecosystem in Southwest China. The unsuited matching at vertical direction and unreasonable special distribution at horizontal direction of landscape use make the landscape degradation a major problem in karst mountain areas. But little is being understood about the interrelation between the spatial distribution of rocky desertified land and the rocky desertification processes. This paper analyzes the ecological conditions of 5 special peak cluster-depressions which are at different desertification degrees on the southern slope of Huajiang karst gorge based on field investigation, the change of landscape pattern indexes and their ecological significance, in order to understand the ecological spatial character and evolving procedure of karst mountains from landscape ecological viewpoint. Results indicate that the diversity index, dominance index and evenness index relate closely to the landscape matrix of peak cluster-depressions, and show different ecological significance in different rocky desertified peak cluster-depressions. With the increase of rocky desertification intensity, the diversity index is in a decreasing trend while dominance index in an increasing trend significantly, the evenness index decreases firstly and then increases when rocky desertification develops further, the isolation and patch area of naked rock increase gradually but isolation of grasslands, shrub and woodlands increases while their patches area in a reduction. The landscape of potential rocky desertified peak cluster-depressions is even more seriously fragmentized than light and moderate rocky desertified peak cluster-depressions, and fragmentation is most in all peak cluster-depressions. The landscape patterns and development modes of potential rocky desertified and strong rocky desertified peak cluster-depressions represent two typical types of rocky desertification in southwest karst mountain areas. This paper shows that the processes of karst ecosystem rocky desertification depends on the distribution, fragmentation and conjunction, not merely the absolute quantity scale of naked rocks and vegetation. The analysis of landscape pattern emphasizes not only area, but also the relations and influence among rocky desertification processes, the spacial pattern of rocky desertification and landscape element character, therefore, landscape should not be neglected in the studies of rocky desertification degree and indexes, landscape patterns, landscape diversity and patches closely correlating with rocky desertification process must be taken into account in the assessment of the karst rock desertification degrees.