不同起始状态对草原群落恢复演替的影响

内蒙古典型草原,由于过度放牧利用,绝大部分草原处于退化状态.为了使退化草原得到较好的恢复,以锡林郭勒盟白音锡勒牧场典型草原为研究对象,比较分析了在不同起始状态下的草原群落,经过6a的自然恢复,其各自的群落组成,地上生物量及共有种的植株高度、节间长、叶长、叶宽,土壤紧实度和容重.结果表明:1)不同放牧率的植物群落,经过6a的禁牧恢复,群落类型发生了变化且群落趋于一致.2)当放牧率SR≤5.33羊/hm2(SR4)时,演替起始状态对草原群落地上生物量的恢复没有影响；当放牧率SR＞5.33羊/hm2时,演替起始状态对草原群落地上生物量的恢复产生影响,其结果是导致当前生物量降低,不利于草原的恢复.3)不同放牧率植物群落的植物个体特征趋于一致,“个体小型化”现象消失.同时,也说明群落恢复演替的起点不同,正常化的时间没有太大的变化.4)不同放牧率植物群落的土壤紧实度和容重经过6a的禁牧恢复,没有得到完全恢复,但均达到一致的水平.

The effects of different original state on grassland community restoration succession

The Xilinggol steppe is one of the four biggest grasslands in China, and is representative of the semi-arid grasslands in Asia. To discover whether the initial state (6 years previously) of various degraded grassland communities has had an effect on recovery of these communities and in what way this effect is evidenced, research was undertaken on vegetation that has undergone 6 years of recovery through non-grazing, after varying degrees of degradation under different grazing rates. The experimental study site is in the middle reaches of the Xilin River, 500 meters west of the Inner Mongolia Grassland Ecosystem Research Station of the Chinese Academy of Sciences, from 43°26'-44°08'N and 116°04'-117°05'E. The following is the general situation of the surveyed land. The grazing experiment at the study site began in summer 1989. The sample plot is degraded grassland, in which Artemisia frigida and small grasses dominate, and the experimental grazing animal was sheep. There are 6 conditions, including five different stocking rates (1.33, 2.67, 4.00, 5.33 and 6.67 sheep/hm²) and a non-grazing control. Having been grazed at various rates for 16 years through 2005, the structure and function of the ecological system (plant community, soil physical and chemical properties) have experienced significant changes. Grassland ecological systems are in different degrees of degradation. To examine the recovery process of such grassland ecological systems after suspension of grazing, the grazing experiment was stopped in 2005. By 2011, the grassland ecosystems had recovered to their natural state. Investigation and sampling were conducted in August 2011. In recent years, under the influence of high use and adverse natural factors, the majority of the Inner Mongolian steppe has been in a state of degradation. In order to facilitate recovery of the degraded grasslands, the present research was conducted on a typical steppe at Baiyinxile Ranch in Xilinggol. The author analyzed a series of indicators of the state of various grassland communities (each after 6 years of natural recovery), which include plant community composition, aboveground biomass, plant height, internode length, main species leaf length, leaf width, soil compactness, and soil bulk density. The findings suggest that: 1) After 6 years of non-grazed recovery, communities of different stocking rates have changed their community type, and the communities tend to be consistent. 2) Initial successional stages have no significant effect on aboveground biomass recovery when the stocking rate is less than 5.33 sheep/hm²; however, if the stocking rate is more than 5.33 sheep/hm², the initial successional stages lead to a decrease in current biomass. In other words, a higher stocking rate is unfavorable to the recovery of grassland. 3) Individual plant characteristics of communities at different grazing rates tend to be consistent, and the individual miniaturization phenomenon disappear. At the same time, this shows that even though the starting point of community recovery and succession is variable, the normalization time is nearly constant. 4) After 6 years of recovery, the soil compactness and bulk density of communities with different grazing rates did not fully recover, but tended to be consistent.