封育措施对半干旱沙地草场植被群落特征及地上生物量的影响

随着干早区草场非平衡态理论的提出和发展，退化草场封育的时间、方式与草场恢复间的关系已成为目前研究的主要课题之一：作者选择完全封育、季节封育和未封育3种措施进行对半干早沙地草场的植被特征及其生物量进行比较研究，结果表明，在封育处理的年份中，不同封育措施（放牧压力）是决定植被差异的主要因子。完全封育区和季节封育区植物以一年生草本为主，在植物种数量、生物多样性上差异并不显著，未封育区植被则以多年生草本为主，且Simpson和Shannon多样性指数与前两者差异均显著；完全封育并未导致一些牲畜喜食植物种的完全消失，但一些饲用价值差的植物如平卧碱蓬等大量出现在完全封育的群落中，同时旱生和强旱生植物的比例明显增加。尽管3种措施地上部分总生物量差异并不显著，但各群落中主要植物种的地上部分生物量则存在这一定的差异，从3种措施植被的饲用价值来看，季节封育区植被的饲用价值较高，表明季节封育可以促进并提高草场的放牧利用价值。

Impacts of exclusion on vegetative features and aboveground biomass in semi-arid degraded rangeland

Following the development of non-equilibrium theory for arid rangeland, the relationship between enclosure and range- land restoration has garnered much attention over past few decades. In this paper, we selected three treatments for sandy rangeland in semiarid area, i.e. year-round exclusion, seasonal exclusion and non-exclusion, and conducted comparative studies on vegetation features and aboveground biomass, in addition, change on annual precipitation was analyzed as a supplemental factor for non-equilibrium theory. The results show that exclusion measures (grazing pressure) are determining factors for community change. Communities for year-round exclusion and seasonal exclusion are dominated by annuals, and have no significant difference in spe- cies number and biodiversity, whereas community in non- exclusion was dominated by perennials and have significant difference in Simpson and Shannon biodiversity indices with former two treatments. Year-round exclusion does not result in disappearance of some palatable plant species, but appearance of some unpalatable species such as Salsola prostrata, and proportion of xeric and strongly xeric plant increases. There is no significant difference in aboveground biomass among three measures, but significant dif- ference exists among the main plant species of three measures, in the view of palatability of floristic composition, community for seasonal exclusion has higher palatability, which proves partly that seasonal exclusion can increase grazing values for arid rangeland. The above-mentioned results are helpful for us to better understand non-equilibrium theory in arid rangeland and give a reference to formulate scientific and sound rangeland management system.