摘要
探讨了在云南东北部干热河谷区域的严重砂石化土地上利用两种典型固氮树种进行植被恢复后对当地原有植被系统的影响。研究表明 ,不同植被恢复方式对地表植被和土壤种子库的影响是巨大的 ,物种的组成与密度都发生变化。高密度合欢 ( Leucaena glauca)恢复方式下 ,大量当地物种 ,尤其是一些阳性物种从地表植被中消失或生长受到抑制 ,生物多样性降低。参照稀灌草丛设计的马桑 ( Coriaria sinica)恢复方式对原有草坡地物种的数量和多样性影响不大。各种植被恢复方式的土壤种子库的萌发试验表明 ,合欢恢复方式 ( L.glauca)使土壤种子库的种子密度增大 ,同时种子组成也由原来的喜光耐旱为主变为耐荫型为主 ;马桑 ( C.sinica)恢复降低了种子密度并减少了种子种类 ,但主成分的性质未发生改变。一些当地物种仍存在于受影响后的地表植被和种子库中 ,使改变后的系统与当地草坡间存在着一定程度的相似性 ,但这种相似性随植被恢复的变化在地表植被与土壤种子库间表现不一致 ,显现出随干扰与植被恢复变化的非同步性。
The phenomenon known as “valley bottom dryness” is common along rivers and their tributaries in southwest China, where potential annual evaporation is up to 5 times as high as the annual precipitation. Agricultural activities and fuel harvesting have led to severe degradation in those valleys. To encourage vegetation recovery, various native and exotic tree and shrub species were introduced to these areas. This study aims to investigate the impact of the introduced species on composition of the vegetation and soil seed banks. The study was carried out at a highly stony land surface of the dry valley of Xiaojiang River, Dongchuan District in Northern Yunnan. We studied species composition and soil seed bank of three communities. Three rehabilitation methods were used: (1) planting with tree species (Leucaena glauca) at higher density; (2) planting with shrub species (Coriaria sinica) at low density in a savanna liked (grass dotted with scattered shrub or tree) way; and (3) natural regeneration. Results showed that changes in standing vegetation and soil seed banks were related to the rehabilitation method used. Many native species, especially the non-shade tolerant species, were excluded or restrained at the standing vegetation after rehabilitation with L. glauca. Rehabilitation with L. glauca also reduced the biodiversity index of the community. In comparison, rehabilitation with C.sinica increased the biodiversity index and many of the native grass species were able to persist. Soil seed density increased after rehabilitated with L. glauca and species composition of the seeds shifted from a light-drought tolerant species domination to a shade-tolerant domination. Rehabilitation with C. sinica reduced seed density in the soil seed bank but had no effect on species composition comparing to that of the natural regeneration method. The rehabilitated ecosystem and natural regenerated vegetation showed similarity in that some of the native species are present in both ecosystems. However, the degree of similarity differed between standing vegetation change and soil seed bank change.
出处
《生态学报》
CAS
CSCD
北大核心
2003年第7期1454-1460,共7页
Acta Ecologica Sinica
基金
中国科学院"百人计划"资助项目
中国科学院山地灾害与滑坡泥石流研究资助项目 ( 2 0 0 0~ 2 0 0 2 )~~
关键词
退化山地
干热河谷
植被恢复
恢复方式
当地物种
东川
degraded mountain area
dry-hot valley
rehabilitation method
mative species
dongchuan District
