内蒙古草原退化群落恢复演替的研究II. 恢复演替时间进程的分析

 根据内蒙古典型草原地带的羊草+大针茅草原退化变型一冷蒿群落封育12年(1983—1994)的动态监测数据进行分析，对群落恢复演替轨迹取得以下认识： 1．依据群落优势种的更替及主分量分析结果可将恢复演替过程划分为冷蒿优势阶段、冷蒿+冰草阶段、冰草优势阶段、羊草优势阶段。 2；退化草原群落在恢复演替过程中，群落生产力的变化表现出阶梯式跃变和亚稳态阶面相间的特点。第一次跃变发生在1984年，上升到第二个阶面，第二次跃变发生在1990年，进入了第三个阶面，已接近于原生群落的生产力。 3．群落生产力与水资源量的关系因恢复演替阶段不同而异。第一亚稳态时期，群落地上现存生物量大体处于166g·m-2的水平上，生长季降水量达176mm以上时，增加降水对群落生产力的提高不发生显著影响。第二亚稳态时期，群落生物量与降水量之间的相关性显著。可推算出群落于物质生产用水量介于1.1～1.6mm·g-1之间。此值在1.1mm·g-1时，群落对水资源的利用效率最高，而在1.6mm·g-1时群落生物量达到最大值。 4．在恢复演替进程中，群落密度的位点常数约为271.5株·m-2，循此常数上下波动，表现出拥挤与稀疏交替发生的过程，构成了恢复演替的节奏性变化。群落生物量的跃变与亚稳态的形成，以及群落密度的拥挤与稀疏交替作用是群落恢复演替的内在机制。恢复演替的速度，到第10年发生了1.78个半变的生态距离。5．草原退化群落恢复演替过程中，按照其节奏性及生产力跃变与亚稳态的规律，调控放牧利用强度或采取技术措施，调节群落拥挤和稀疏的交替过程可加速恢复演替进程。

Research on the Restoring Succession of the Degenerated Grassland in Inner Mongolia II. Analysis of the Restoring Processes

The restoration dynamics of the Artemisia frigida community, one of the grazing-induced degenerated community of the zonal vegetation dominated by Leymus chinensis+Stipa grandis, was monitored after the fence during 1983 to 1995. The temporal data set were analysed. The results were as follows:1. Based on the replacement of dominant species and the result of principle component analysis, the process of restoring succession can be relatively divided into 4 stages, that is, the stage of degenerated community, the initial stage of restoration, the Agropyronmichnoi dominating stage, and the Leymus chinensis dominating stage.2. A feature of staircase transitions alternating with sub-atable treads is shown by change of community productivity during the restoring succession. The first transition started as soon as the grassland was fenced (in 1984), and the productivity level climbed to the first tread; the second transition was taken place in 1990, the productivity jumped second tread that approached the productivity of primary community.3. The relationship between community productivity and water resource were dependent on the stage of restoring succession. The standing crops of the community maintained the a standing crop of 166g·m-2 A precipitation favorable year with a rainfall of 176 mm during plant growth season had no significant effect to the raise of community productivity in the first sub-stable state stage. While the relationship between community biomass and precipitation was significant in the second sub-stable state stage. The water requirement for producing dry material were between 1.1～1.6mm·g-1,that is, the maximum water resource utilization ratio of community was 1.1mm·g-1,and the maximum production can be reached when the ratio was 1.6mm·g-14. The dots number of the studied community density is around 271.5 plants·m-2. The density became high and low alternatively and rhythmically, being the instinct mechanism of community restoration. The restoring succession speed could be measured by the half-change of communities. A 1.78 half-change. happened during the 10 years restoration.5. The restoration could be accelerated by adjusting grazing intensities and other techniques in accordance with the rhythmic regularity of the restoring succession.