The Effects Of Soil Nutrients Distribution On The Construction And Biomass Of Community

The space distribution status of soil nutrients, especially the restricted resources, determine the structure and biomass of community to some extent. Because of the differences in individual morphology, eco-physiology and viability between component species, the difference in selectivity and utility to richness plot under heterogeneity condition, the structure and biomass of community will different, even though the amount of nutrients is the same, when the heterogeneity of soil nutrients exists. So the study of the effects on community structure and biomass of the soil nutrients, different distribution pattern is very important to the revelation of the law of vegetation succession.In order to investigate the characteristics of the communities and the environment, eight communities were selected in this experiment, which were abandonment succession pioneer communities and had no or had a little disturbance. The community investigation included records of the species name, height, coverage, abundance and biomass. The environment determination included location, slope direction, slope degree, altitude, soil moisture, soil nutrients. Spatial heterogeneity and their standing condition differentia of the eight communities was analyzed using canonical correlation analyzing method. Meanwhile the Artemisia scoparia community in which plants dispersed homogeneously on the loess hill and the Medicago sativa plot in which soil nutrients was homogeneous were chose,then divided them into plots and applied compound fertilizer and organic fertilizer to the Artemisia scoparia community, compound fertilizer and urea to the Medicago sativa plots. The fertilizer applied into plots as two kinds of manner, one of which made the soil nutrients homogeneous, the other made soil nutrients heterogeneous. The effects of different fertilizer distribution format on the structure and biomass of community were studied. The results showed that:1 Spatial heterogeneities between communities are greater than that of within communities, and spatial heterogeneities between communities and most of standing conditions differentia are positive relationship, both of which imply environments can act on communities composition and structure of early succession stage, and further canonical correlation show that about environment differentia account for 49.6% of heterogeneities between communities. Whether in person or canonical correlation analysis, heterogeneities between communities and its nitrogen differentia show strong positive relationship, which implies that nitrogen is the main factor acting on heterogeneities between communities, besides nitrogen, soil phosphorus and potassium show significant positive relationship, thereby fertilizer, especially nitrogen should be fertilized in re-vegetation of abandoned land.2 As to compound fertilizer, the average height of the communities was higher when the fertilizer was distributed homogeneously at small scale and when the fertilizer was distributed heterogeneously at middle and big scale. At the same scale and under the same fertilization intensity, the density of the communities decreased when the nutrients was distributed homogeneously. At small and middle scale under low and middle fertilization intensity, the biomass of the communities was higher when the fertilizer was distributed homogeneously. At small and middle scale under high fertilization intensity, at big scale under all fertilization intensity, the biomass of the communities was higher when the fertilizer was distributed heterogeneously. The higher the fertilization intensity was, the lower the diversity and uniformity of the communities when the nutrients was distributed homogeneously at all scales. The higher the fertilization intensity was, the higher the diversity and uniformity of the communities when the nutrients was distributed heterogeneously at small and middle scale and was highest at big scale under middle fertilization intensity.3 According to the study of the effects of different fertilizer and different distribution patter, we can see that the compound fertilizer is better for the Medicago sativa plot, and the yield is highest at big scale under high fertilization intensity using heterogeneous fertilization.