| In the Stipa baicalensis steppe of the eastern zone of XilingaolePlateau, Inner Mongolia, two zonal habitats and one intrazonal habitat (broadplain, hill slopes and lowland meadow) were chosen to set up research sites(labeled as site A, site B and site C, respectively). On the base of wholesteppe community, the phenomena and process of plant reproductive ecologywere systematically researched, and the characteristics of steppe plantreproductive ecology on the level of community was analyzed. The studycontents and research methods were as follows:1. In site A, the method of harvesting all mature plant seeds (or fruits) on unitarea was used to mature community's yearly seed production in fenced plotand freely grazed area out fenced plot. The variations in seed number and seedquality between two survey years were evaluated.2. The time and spatial dynamics of soil seed banks were surveyed in site A (2sample points), site B (9 sample points), and site C (8 sample points) by usinga method of taking samples with an earth core of known volume, spreading thesoil out on trays in conditions suitable for' germination and counting theseedlings which appear.3. Inside and outside of fenced plot, site A, the dynamics of emergence,mortality and survival of seedling cohorts were investigated. The method usedhere was to label the emerged or died seedlings at set intervals in fixedquadrates. In the fixed observation points of site B and site C, the dynamics ofstanding seedlings was monitored by using random quadrates. At the sametime, some artificial bare grounds (50~*20~*20cm, no seed in soil ) were madeto simulate natural openings to observe seedlings originated from new seedsor from redistributed seeds. In an accessory sample site, an experiment wascarried out to monitor the effects of simu1ating heavy harrowing on seedlingemergence.4. Under the conditions of freely grazing and fenced plots in site A, eightblocks of paired quadrates (treatment and check ) were arranged inrandomized blocks. Plants in the quadrates were cut with different stubbleheights at designed times and the community feature after cutting wasobserved at set intervals to investigate the changes of plant vegetative growthand reproductive growth and to assess the effects of cutting intensities andcutting times on community plant reproduction.Principal research results were as fol1ows:l. Tha numbers of plant species recorded in fenced plot and outside fencedplot of site A, site B and site C were 57, 48, 80 and 39. The annualprecipitation fiuctuated between years, it was \486.9mm in l998, l41mm aboveaverage, l89.9mm in l999, l56.2mm less than average. The rainfall patternexerts great effects. on the research results.2. The seed production of site A was 6785.6 seeds.m-2 in fenced plot andl379.9 seeds.m-2 out fenced plot in l998. It was 26l3.4 seeds.m-2 and 2539.4seeds.m-2 in the same places in 1999 (the research area outside fenced plotwas grazed befOre l,July and grazing was stopped after then ). Most seedsmatured in autumn, only a very few in spring. Continuously grazing washarmfuI to seed production. Among the total seed production, the biggestproportion was dicotyledons. There was about one quarter of the plant speciesthat the germination rate of new produced seeds was more than 90%, andanother one quarter the new seed germination rate was less than 12%. Thequantity and quality of seed production were controlled by yearly rainfallpattern, and were also affected by the reproductive allocation characteristicsof the species.3. During the period of research, the time dynamics of soil seed bank was239-8l2 seeds.m-2 in fenced plot and l65-6l8 seeds.m-' outside fenced plot.The fluctuation was influenced by the proportion of input and output. Theseed contents of monocotyledons in soi1 seed bank reserye were relatively low,27-37% in fenced plot, 22-44.5% out fenced plot. Continuous grazing couldcause th...
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