受地质条件制约的中国西南岩溶生态系统

KARST ECOSYSTEM CONSTRAINED BY GEOLOGICAL CONDITIONS IN SOUTHWEST CHINA

岩溶生态系统是受岩溶环境制约的生态系统。中国西南岩溶石山区岩溶发育的地质历史背景,决定其碳酸盐岩主要分布于NE向的构造隆起带上。碳酸盐岩出露面积占土地面积比例≥30%的岩溶县有292个。岩溶生态环境的特殊性和脆弱性主要表现在:(1)西南岩溶生态系统中水、土资源的短缺且不协调。水资源以地下水资源为主,且难开发;土壤资源零星分散,土层薄,易流失;(2)现存广西区植被覆盖特征显示,岩溶石山区森林覆盖率明显低于非岩溶区,同时也暗示着岩溶石山区植被的恢复、演化慢于非岩溶区植被;(3)贵州石漠化分布特征表明岩性对岩溶生态环境的制约;(4)脆弱的岩溶生态环境制约着生态系统的人口承载力。贵州省是西南碳酸盐岩集中分布区的中心,其人均国民生产总值则远比邻省的低。广西、湖南、湖北、重庆碳酸盐岩的分布具有明显的地块性,其岩溶县的人口密度仅分别为非岩溶县的85.05%、83.03%、46.78%、54.43%,岩溶县的人均国民生产总值、农民人均纯收入也不及非岩溶县。根据岩溶生态系统结构特征,在西南岩溶生态重建过程中应关注地表植被覆盖率对表层岩溶带水循环的影响、关注土地利用对地下水的影响、关注岩溶地球化学对特色经济植物可持续发展的影响。

Karst ecosystem is an ecosystem controlled by karst environment. In Southwest China, carbonate rocks are mainly distributed along the NE-extending tectonically upheavedzone, deeply impacted by geological background. Based on the statistics data, 292 karst counties whose carbonate rocks are 30% higher than the lands, with respect to their distribution area. And particularity and fragibility of the karst ecosystem can be summed up as follows: (1) Soil and water resources are of shortage and out of coordination. In other words, underground water is an essential water resource, accounting for 41%-83% of the total. Meanwhile, the formation of limestone soil is slower. (2) Guangxi is a typical karst region. A large difference is noticed in vegetation coverage between karst regions and non-karst regions. The average coverage of bush and forest communities is 14.81% and 12.13% in the karst regions, 1.92% and 31.3% in the non-karst regions. (3) The wide distribution of rocky desertification in Guizhou Province indicates the karst environment is strongly affected by carbonate rocks' properties. (4) The fragibility of the karst ecosystem results in its lower population-carrying capacity. We can find the population density of karst counties in Guangxi, Hunan, Hubei and Chongqing is only 85.05%, 83.03%, 46.78%, and 54.43% in non-karst counties and average GDP per person and average income per peasant are also low in these karst counties. On the other hand, Guizhou Province is a center where carbonate rocks are most distributed in Southwest China, and its average gross domestic product (GDP) is obviously lower than that of the surrounding provinces. Great attention should be paid to the relationship between vegetation coverage and water cycle in epikarst zones, the relationship between land-use and underground water protection and the relationship between karst geochemistry and sustainable development in Southwest China.