The Research On Distribution Pattern Of Vitex Negundo Shrub In The Watershed Of Miyun Reservoir

Vitex negundo Shrub is one of the most extensive Shrub Community in MiYun Reservoir, which is necessary to preserve soil and water and conserve water in MiYun Reservoir in Beijing. Based on the investigation data of eighteen plots in ChaoGuanxigou of MiYun reservoir, and using the methods of Diversity indexes and Spatial distribution pattern, this thesis studied the structure of shrub and the spatial pattern at different development stages and the population relationships, which can supply basically theory on supervising and Sustainable managing to headwater protection forest in MiYun Reservoir in Beijing.Results showed that:①the distribution trend of Evenness indexes and Simpson indexes in Shrubs is the similar each other, and unobvious changing; but the changing rates of Riches indexes and Shannon are obvious and have maximum and minimum. The shrub has twenty-one kinds, Vitex negundo are 29 percents, which is most and has important effect in Shrub Community. The important value of different Shrubs in different plots is different. The average of the important value of Vitex negundo is 0.218, which is in NO.1, is diamantes in Shrub Community.②The Height-class structure of the Vitex negundo is a half of "Z" shape, most of individual frequency appears in gradeⅣand gradeⅦ, the height of Vitex negundo is from 0.8m to 1.7m.The Diameter -class structure of the Vitex negundo looks like growing style. The gradeⅡand gradeⅢhave greatest numbers, the percents are 43.8 and 34.7.It showed the Vitex negundo in all plots are in exuberant growth period.③All the Shrubs are Random distribution in all studied scales. Shrubs have few differences pattern in different elevations. When the elevation is increasing, the spatial distribution pattern is also changing from Random distribution to Random distribution and obvious Cluster distribution coexistence. Small Diameter-class'Vitex negundo are in Cluster distribution, and when it is growing bigger, the pattern will become to Random distribution. The population relationships in different Diameter-classes are changed from Positive association to Negative association, but unobvious. The correlations of adjacent bigger Diameter-classes are weaker.④The research has studied the inter-specific Relationship of five kinds of Shrubs. The Population relationship is different as long as the space scale is different. The relationship between Vitex negundo and Rhamnus parvifolia Bunge is unobvious Negative association in all scale(r< 10m),they are competition. The relationship between Vitex negundo and Philadelphus pekinensis Rupr is unobvious Positive association in all scale(r<10m),they can survive in the same space. The relationship between Vitex negundo and Ziziphus jujuba var.spinosa(Bunge)Hu is unobvious Negative association in scale (r > 1.5m),but in the scale (0～1.5m) is Positive association. The relationship between Vitex negundo and Folium Rhododendei micranthi is unobvious Negative association in (r<3.8m) scale, the other scales is unobvious Positive association. The relationship between Vitex negundo and Securinega suffruticosa(Pall.)Rehd in the scale (1.5m～4.5m) is Positive association, the other scale is unobvious Negative association.