Quantitative Ecology And Management Policy Of Weeds Communities In Shanxi Orchard

In this paper, the summer and autumn weeds communities were taken as research object. On the basis of field investigation, applied quantitative vegetation ecology method, system researched community summer and autumn weeds, including the classification and sort of summer and autumn weeds,species diversity analysis,advantage species of niche and interspecific association analysis. The object of this study was to provide some theoretical basis so as to management orchard and grass-weed control.Meanwhile, TWINSPAN and DCA were conducted to the summer and autumn weeds to classification and ordination. TWINSPAN hierarchical classification divided the 66 quadrats into 11 groups of summer weeds communities, and divided the 69 quadrats into 12 groups of autumn weeds communities. The classification results better reflected the relationships between weeds communities and environmental gradients, and had been tested by DCA dimensional ordination. DCA first axis mainly reflected the changes in soil moisture, from left to right, soil moisture gradually increased. The second axis mainly reflected the trend of soil nutrients, from the bottom to the top, the soil nutrient gradually reduced. DCA illustrated the close relationship among the distribution patterns weeds communities, soil moisture and soil nutrient. The results showed that the dominant species of summer and autumn weeds in the orchard could objectively reflect the communities'habitat characteristics.The community diversity was studied by using the richness indices, diversity indices and evenness indices. The results showed that:richness indices Ro and diversity indices H showed basic consistent change trend and evenness index and before two kinds a basic opposite changes index trend. In summer weeds community, Associations of VIII has higher richness indices Ro and diversity indices H; but the two indices were small in Associations ofⅪ; In autumn weeds community, Associations ofⅤandⅥhave higher richness indices R0 and diversity indices H,but the two indices were small in AssociationⅣ.The result showed that the species richness, richness indices and diversity indices also increased accordingly, evenness indices generally smaller instead.The niche breadth and niche overlapping of dominant species of the communities were researched by using Levins,Shannon-Wiener and Pianka index. The results showed that:In s summer weeds community, the Setaria viridis and Chenopodium glaucum were the largest niche breadth, the most widely for ecological range of species, and Phragmites australis was the least niche breadth, the small competitiveness in community environment; In autumn weeds community, the Leonurus artemisia was the largest niche breadth and adaptable, and Carex lanceolata was the least niche breadth. To overlap, autumn of species overlap values outweigh the summer of species. It's because that the autumn species were more adapted to the environment, more great competitiveness.The interspecific association and correlation of 20 dominant species of summer and autumn weeds communities were analyzed by usingχ2-test, Pearson's related coefficient and Spearman's related coefficient. The consequences showed that:In summer weeds community,84 species were positive correlation,106 species were negative correlation,23 species were significant correlation; in autumn weeds community,77 species were positive correlation,113 species were negative correlation,52 species were significant correlation. It could be seen that the species-pairs in summer were poorer relevance, looser associativity, and stronger independence. This maybe relates to the whole community development stage and species characteristics of itself involved.