围封6年对温带典型草原坡地物种多样性及其与地上生物量的关系的影响

以内蒙古太仆寺旗地区典型克氏针茅-羊草草原为研究对象，通过调查围封6年后围栏内外典型草原群落特征，分析围封、放牧处理下典型草原植物群落结构及地上生物量的动态变化，揭示围封放牧对植被群落结构、物种丰富度和地上生物量的影响。结果发现，在围封6年后，各功能群物种丰富度与盖度围栏内外的空间变化趋势基本一致。群落物种丰富度和地上生物量均随坡位下降而显著增加，初步显示了物种多样性与生态系统功能的空间变化的一致性。围栏内物种丰富度显著低于围栏外，而地上生物量却显著大于围栏外。围栏内多年生禾草、一年生植物物种丰富度显著低于围栏外，而半灌木盖度、生物量显著高于围栏外。围栏内外在禁牧和放牧不同处理下，表现出不同的草原退化方式：在禁牧条件下，尽管生物量有所恢复，但灌木和半灌木的增加却代表了草原的退化；放牧、刈割等人类活动增加了耐牧物种和不适口植物生长的可能，表现为草原退化指示物种增加，同样是草原退化的表现。围栏外一年生植物盖度和生物量显著高于围栏内，而一年生植物的频数也远远大于围栏内（围栏内外频数比13：71），且独行菜、猪毛菜等仅出现于围栏外。同时，地上生物量随着物种丰富度的增加而增加，但只有围栏外的关系达到统计显著程度，说明围封调制了生物多样性与生态系统功能的关系。本研究表明，对于干旱半干旱典型草原的恢复，不能简单地采用长期完全禁牧措施，应当根据区域环境、植被以及社会经济情况，制定季节性放牧或者间歇性禁牧的恢复措施，从而保证草场的可持续性恢复利用。

Species richness within a six-year slope exclosure in a temperate grassland and its relationship with aboveground biomass

Our experiment was conducted within a six-year slope exclosure in a typical Stipa krylovii grassland of Taips County, Inner Mongolia. By sampling the species abundance and aboveground biomass both inside and outside （normal grazed, or control）the exclosure, we analyzed the patterns of community structure and aboveground biomass, and explored the effects of exclosure on community structure, species richness, and aboveground biomass. The results showed that the spatial pattern of the species diversity and cover of the functional groups are similar. The species richness and aboveground biomass increased significantly with decreasing slope position, showing that the spatial variation of species richness and ecosystem function had the same trend. Species richness was significantly lower in the exclosure than the control because of reduced annuals and grass species. However, the aboveground biomass of the grazed control is significantly lower than the exclosure treatment due to the development of subshrubs and shrubs inside the exclosure. The experiment results strongly implied that overgrazing or over protection can lead grassland degradation. However, the degradation directions of the two management are distinctly different： Overgrazing suppressed the grass and shrub biomass, leaving opportunities for annuals. On the other hand, over protection give the changes for shrubs and subshrubs to proliferation. The human activities including grazing and cutting increased the growth of grazing-tolerant and unpalatable plants, to some extent. The coverage and biomass of annual were higher outside the fence, so as to the frequency. For example, the frequency ratio of inside to outside was as low as 13：71, and Lepidium sativum and Salsola collina only existed outside. The regression of aboveground biomass on species richness showed that the biomass increased with species richness both inside and outside of the exclosure, but the inside exclosure seems has much larger slope coefficient than the outside. This study demonstrated that long term grazing prohibition may not be the right way to restore the arid and sub-arid grassland, in order to maintain sustainable usage of grassland, appropriate moderate grazing should be carefully planned according the local climate and soil conditions.