青海省大通县退耕还林区主要植物群落物种组成与多样性

2008年3 - 8月，对青海省大通县退耕还林区不同样地类型下不同植物群落进行全面考察，综合分析了主要植物群落物种组成与多样性。结果表明：①在不同生活型中，物种多样性表现为草本层＞灌木层＞乔木层，这与群落中各层次的物种组成情况相同。②不同群落间物种多样性也有较大的差异，混交林相对纯林具有更高的物种多样性。③对不同起源地的群落多样性，天然次生林＞退耕地人工林＞农耕地，且退耕多年地段的群落物种多样性接近于天然次生林。④在不同的退耕时间序列上，随着时间的推移，群落逐渐趋于稳定，群落物种多样性和丰富度呈“小—大—小”的变化过程，而均匀度和优势度指数呈“大—小—大”的变化过程。退耕还林在保护生物多样性、恢复植被和改善生态环境等方面发挥着重要作用。在退耕还林还草过程中，应注意合理的林草布局，促进群落的稳定和更新。图2表4参15

Species composition and diversity for plant communities in conversion of farmland back to forest areas of Qinghai Province

Research on different plant communities of different plot types （conversion of farmland back to forests,natural secondary forest and farmland） was conducted in a project area that returned farmland to forests in Datong County,Qinghai Province from March to August in 2008. After analyzing species composition of the main plant communities （including 15 types,such as Picea crassifolia forests,Picea crassifolia-Betula platyphylla forests,Picea crassifolia-Hippohae rhamnoides ssp. sinensis forest,Larix principis-rupprechtii forests,Populus davidiana forests,and Sabina przewalskii forests）,species richness index （R0）,Gleason species richness index （I）,Simpson ecological dominance index （D）,Shannon-Weiner species diversity index （H） ,and Hill evenness index （E5） of the community were calculated. Results showed that （1） the level of the species diversity in the community was herb〉 shrub 〉tree. Also,（2） the level of the species diversity in mixed forests was higher than pure forests. （3） According to land use,species diversity was：natural secondary forest 〉artificial forest on converted farmland〉 cropland. However,after 27 years diversity of the converted farmland was close to that of the natural secondary forest. （4） As conversion time increased,the community became more and more steady-state. The H and I were ＂small-big-small＂ and the D and E5 were ＂big-small-big＂. To promote stability and rejuvenation of plant communities when returning farmland to forests,logical distribution of species should be realized.