泥石流多发干旱河谷区植被恢复研究

云南东北部东川小江流域的干旱河谷土地退化十分严重，土地表层的砾石含量已超过60％，有机质含量、全氮、有效氮、有效磷、有效钾的含量相对于残存燥红土明显下降。草坡是当地的主要植被类型，并未起到防治土地退化的应有作用。以合欢（Leucaena glauca)、马桑（Coriaria sinica)种植为主的恢复方式对土地的恢复有明显的改善作用。高密度的乔木树种合欢的种植使林下的草本物种的数量和组成发生了极大变化，较耐荫的植物占据了林分下层，且物种数量较草坡减少，群落多样性指数降低。三种马桑种植方式下，不但原有的草坡群落的物种仍有大量的生存空间，而且为一些新物种创造了生存环境，从而使物种的种类较原有草坡地增加，提高了群落的多样性指数。合欢种植的生物量最高，对解决当地薪柴严重短缺意义重大，马桑种植在增加灌木层生物量的同时，并未改变草坡的物种组成，还可兼顾解决当地的饲草和放牧，应大力推广。

Plant Rehabilitation on Degraded Land at Debris-prone Dry Valley

Land degradation was serious along Xiaojiang river at Dongchuan of the Northeast of Yunnan.The portion of gravel(>2mm)had exceeded 60% at the land surface and its organic matter,toal N,available N,P,K had dropped sharply compared with those of red soil,The grass which was the major vegetation cover at the research area,did not play the role on preventing soil from degradation.Plantations of Leucaena glauca and Coriaria sinica had effect on land festoration.Dense tree(L.glauca)plantations(2 types)had resulted in significant changes of grass species composition and related quantity. Shade-tolerant species dominated the grass layer, species types and respective diversity indexes decreased in the L. glauca communities compared with grass-land. Under the three C. sinica plantations, grown environment still remained for grass species as that of grass land, but also new environment was created by C. sinica. As a result, the species types and diversity indexes increased at those plantations compared with grassland. The highest biomass of L. glauca had significant meanings for the fuel-shorting villagers. Biomass of C. sinica plantations were not as higher as that of L. glauca, since they still could provide grass for animal fodder to the local villagers as grass land did, they were a substitute way to grass land.