塔克拉玛干沙漠南缘自然植被的水分状况及其恢复

Water condition and restoration of natural vegetation in the southern margin of the Taklimakan Desert

塔克拉玛干沙漠南缘 (以下简称塔南 )是我国土地沙漠化最严重的地区之一 ,其主要原因是因为塔南绿洲边缘的自然植被遭到严重破坏。自然植被的恢复有赖于对主要植被类型生物学特性的了解 ,于 1 998～2 0 0 1年在位于塔南策勒绿洲边缘进行的中国 -欧盟合作研究项目 ( ERBIC1 8CT980 2 75 ) ,目的是探索塔南绿洲边缘自然植被可持续管理的生态学基础。通过对几种优势植物叶片 (或同化枝 )水分关系、气体交换、以及群落特性等方面的综合研究 ,得出了以下结论 :( 1 )塔南绿洲边缘的自然植被皆为隐域性植被 ,主要优势种为 :胡杨、柽柳、骆驼刺以及少量的灰杨 ,这种植物是依靠河流的地表水而发生 ,依靠河流地下水补给而生存 ;( 2 )由于缺乏充分的地表水的补给 ,现存的自然植被几乎不能实现自然更新 ;完全破坏后的自然植被已无自然恢复的可能性 ,必须使用人工辅助方法进行恢复 ;( 3)塔南绿洲边缘主要优势植物叶片 (或同化枝 )清晨水势和气体交换研究结果表明 ,依赖地下水生存的几种植物在整个生长季节没有发生严重的水分胁迫 ,保护和恢复绿洲边缘自然植被的必要条件是保持地下水位的相对稳定 ,禁止对地下水的过度开采。

The Southern margin of the Taklimakan Desert is one of the most severe desertification areas in China. The major reason is that the natural vegetation there has been seriously destroyed by human activity. The restoration of natural vegetation depends on the understanding of biological characteristics of the natural vegetation. A China-EU joint project (ERBIC18CT980275, 1998～2001)was carried out to find an ecological basis for sustainable management of natural vegetation in the southern margin of the Taklimakan Desert. The water relations, gas exchange and community features of several dominant plant species were studied. The results indicated: (1) The natural vegetation in the southern margin of the Taklimakan Desert belongs to intrazonal vegetation, which appeared with river flooding, and lives on the groundwater. The dominant species are Populus euphratica, Tamarix spp., Alhagi sparsifolia and Populus pruinosa; (2) It is now impossible for the natural vegetation to be self-regenerated at the fringe of oases in the southern margin of the Taklimakan Desert because most of the water has been used for irrigating crops; (3) The results of water relations and gas exchanges of the researching dominant plants indicated that these plants did not suffer from severe water stress during the whole growing season, which showed it is necessary to maintain the relative stability of the groundwater table for protection and restoration of natural vegetation in the southern margin of the Taklimakan Desert.