黄土丘陵区典型小流域草地群落数量分类与结构特征及其影响因素

黄土丘陵区退耕还林(草)工程已实施20年，了解草地现状对该区草地生态系统保护与恢复调控措施选择具有重要意义。以安塞纸坊沟小流域内22个草地群落为研究对象，基于Ward聚类和非度量多维度排序(NMDS)方法，对草地类型、结构及其影响因素进行了分析。结果表明：(1)流域内草地共出现23科83种植物，其中禾本科、豆科和菊科物种重要值占比达75%—85%。草地可划分为狗尾草群丛、茵陈蒿群丛、甘草群丛、铁杆蒿群丛和白羊草群丛5类群丛。群丛间结构存在显著差异，狗尾草群丛盖度、地上生物量(AGB)、地下生物量(BGB)和根冠比均显著最低，但Shannon-Wiener指数和Pielou优势度指数均显著高于白羊草和铁杆蒿群丛。茵陈蒿、甘草与铁杆蒿群丛间AGB、BGB及多样性指数无显著差异。(2)功能群对群落结构产生显著影响，豆科矮草对AGB和BGB产生显著正效应，禾本科高草对BGB产生显著正效应，而菊科矮草对群落盖度与BGB产生显著负效应。(3)土壤有机碳(SOC)、全氮(TN)和全磷(TP)含量偏低(分别为6.21,0.82、0.53 g/kg),其中SOC和TN含量显著影响群丛物种组成、功能群和结...

Quantitative and structure characteristics and the influencing factors of grassland communities in a typical watershed at loess hilly-gully region

The Grain for Green Project (GGP) has been implemented for 20 years in loess hilly-gully region on the Loess Plateau. To know the current situation of grasslands in the region is of great importance to select protecting approaches and choose regulatory restoration measures. 22 grassland communities in the Zhifanggou watershed in Ansai District were selected, and their classification, structure and the influencing factors were analyzed using Ward clustering and non-metric multi-dimensional sequencing (NMDS) methods. Results showed that:(1) 23 families and 83 species of plants appeared in the basin, among which the importance values of Gramineae, Leguminosae and Compositae accounted for 75%-85%. Grasslands can be divided into five associations:Setaria viridis association, Artemisia capillaris association, Glycyrrhiza uralensis association, Artemisia sacrorum association, and Bothriochloa ischaemum association. The vegetation coverage, above-ground biomass (AGB), below-ground biomass (BGB) and root:shoot ratio of S. viridis ass were significantly lower than those of the other four communities, but the Shannon-Wiener index and Pielou dominance index were significantly higher than those of B. ischaemum ass and A. sacrorum ass. There were no significant differences in AGB, BGB, and diversity index between A. capillaris ass, G. uralensis ass, and A. sacrorum ass.(2) Functional groups had significant effect on community structure, and short Leguminosae had significantly positive effect on the AGB and BGB, while tall Gramineae had a significantly positive effect on BGB, and short Asteraceae had significantly negative effects on both coverage and BGB.(3) Soil organic carbon (SOC), total nitrogen (TN) and total phosphorus (TP) content were all relatively low (6.21, 0.82, and 0.53 g/kg, respectively). The SOC and TN significantly affected species composition, functional groups and structural characteristics. In general, the grassland in the Zhifanggou watershed recovered well, and subsequent regulation measure selection should consider the types of grassland community and the differences in soil carbon and nitrogen contents.