民勤绿洲边缘积沙带植物群落健康分析

甘肃河西走廊经过60多年的防沙治沙,在绿洲边缘形成了一条积沙带。其中,民勤绿洲边缘积沙带相对最典型、最完整。积沙带上的植被不仅是积沙带的形成因素,更是维持积沙带稳定的重要因素。从一定意义上说,积沙带上植被的健康状况,决定着积沙带的稳定性。为了分析积沙带上的植被状况,在民勤绿洲边缘积沙带上等间距设定了11条样线,通过60多个样方的植被调查,对民勤绿洲边缘积沙带上植物群落进行了健康序列分析。结果表明:民勤绿洲边缘积沙带上的植被普遍是不健康的,民勤绿洲边缘人工固沙林积沙带上的植被健康状况相对好于天然灌丛积沙带上的植被健康状况,乔灌混交林积沙带上的植被健康状况最差。民勤绿洲下游积沙带上的优势种植物柽柳严重枯死,健康状况最差,积沙带潜在风蚀活化的危险。农田弃耕后,沙区农田边缘防护林及其积沙带的保护是一个新的值得考虑的问题。

Health sequence analysis of a plant community in the sand-accumulation belt along the oasis fringe in Minqin, China

With desert control effort in more than 60 years in Hexi Corridor of Gansu Province, sand-accumulation belts have taken into form along the oasis fringe. Among which, the sand-accumulation belt at the fringe of Minqin oasis is relatively typical and complete. The vegetation on the sand-accumulation belts is the important factor not only for the formation, but also for the stability maintaining of the belts. To some sense, the healthy vegetation on the belts is decisive to the stability of the belts. To analyze the healthy status of the vegetation on the sand-accumulation belt, we designed 11 equal-interval sample lines on the belt along the fringe of Minqin oasis. Vegetation on more than 60 plots was investigated and the healthy sequence of plant communities was analyzed. The result showed that the vegetation on the sand-accumulation belt at the fringe of Minqin Oasis was generally unhealthy. However, the vegetation on the belt with artificial sand-fixation was healthier than that on the belt with natural shrub nebkhas, and the vegetation on the belt with mixed arbor and shrub is the least healthy. The dominant species on the sand-accumulation belt downstream Minqin Oasis, Tamarix laxa, was dead or seriously unhealthy. This means that the sand-accumulation belt is under potential risk of wind erosion and activation. As farmland has been abandoned, efforts should be made to protect the farmland windbreak and the sand-accumulation belts.