糙隐子草在不同刈牧条件下繁殖对策的研究

Cleistogenes squarrosa ((Trin.) Keng) is a C4 plant and a short, perennial grass with drought tolerance, and tends to occupy medium degradation grassland in Inner Mongolia steppe. It is idealy suited for studies on compensation or over-compensation because its important of population is the maximum in the medium disturbance in Inner Mongolia steppe..The results showed that grazing sheep preferred to ingest Cleistogenes squarrosa and its corprotion in dietary was 27% when herbage resource was abundance, but the corprotion decreased with stocking rate increasee from 60% to 25%. .The over-compensation existed for net primary productivity (NPP) of Cleistogenes squarrosa population because the plant morphotypes remaining in the population were characteried by a higher density with small individual plant in moderate stocking rate (1.33 sheep hm-2 during 138 days of growth seasons). From the viewpoint of a individual plant, grazing reduced the height and biomass per plant, but the aboveground net photosysthesis efficiency or aboveground net primary productivity (ANPP) increased and it almost no effected for belowground net primary productivity (BNPP) in the moderate stocking rate. However, the lower compensation of ANPP was an greater cost with BNPP in heavy stocking rate (>4.00 sheep hm-2 during 138 days of growth season). From this study, it appears that the plant-herbivore association might be regarded as mutualistic in moderate grazing because not only the ANPP of the population increased, but also the efficiency of herbage utilization increased. However, the compensation of ANPP was attained at cost of BNPP, therefore, the association between plant and herbivore might be trade-off in heavy grazing because the temporary higher efficiency of herbage utilization can not keep the population sustainable development. The results support the grazing optimization hypothesis. The results also showed that aboveground biomass of Cleistogenes squarrosa and its proportion in the community increased with annual mean temperature increase, and the regression equation between its aboveground biomass and mean temperature (t) and total rainfall (r) from April to August was: y=-12.4511+0.0187r+0.0601t2 (r2=0.533，p=0.003). Generally, grazing significant reduced plant height and aboveground biomass per bunchgrass, whereas its coverage, density and total aboveground per square meter increased under grazing. Its nutrients efficiency ratio, such as N and S, were higher compared with other dominant species, such as Leymus chinense. 100 g C produced required 3.17 g N and 0.31 g S for Cleiostogenes squarrosa population, however, 4.24 g N and 0.41 g S for Leymus chinense population under grazing. The high nutrients efficiency ratio maybe benefit for Cleiostogenes squarrosa population under competition with other species in the infertility soil. The net primary productiveity of Cleistogenes squarrosa could increased more than 10 times when nutrients and water was supplied compared to natureal conditions and it was sensitive to sulfur deficiency.

本项目以从糙隐子草为研究对象，采用盆栽和野外定量观测相结合，从个体、种群和群落的水平，探讨不同刈牧强度对其个体形态发育、种群光合、资源利用和生殖投资策略的影响，用生殖生态学、生态等级和冗余理论解释该草的放牧抗性和超补偿生长的机制，阐明其在不同刈牧强度下的生态繁殖对策，为动-植物协同进化和生态适合度及最优放牧假设提供依据