Spatial Heterogeneity Of Soil Moisture, Temperature And Nutrients Following Harvesting In Secondary Forests

Disturbance is one of the most important sources resulting in the spatial heterogeneity. Spatial pattern is the substantial expression of spatial heterogeneity. It is important to discover the dynamics for soil resources spatial heterogeneity (pattern) after vegetation being disturbed in forest, as it is meaningful theoretically for recognizing the relationship between disturbance and spatial heterogeneity (pattern), and also is helpful for uncovering the feedback between the botany and soil resources in ecosystems. Therefore, our research was conducted in the secondary forests at the Maoershan Region in the northeastern China during 2001 and 2003. Randomly harvesting 50% of basal area, clear cutting and undisturbed were carried out in three plots, geostatistics theory and methodology were applied to determining the sample regime, data analysis was based on the semivariogram method and Kriging algorithm. Topsoil samples were taken for gravimetric water content (3⁵cm), nutrients (0-10cm, nitrate, ammonium, total nitrogen) determination, and soil temperature (3⁵cm) was also measured at the same time. Spatial heterogeneity (pattern) for different soil factors were quantified and compared; spatial correlation between soil nutrients was determined meanwhile.The results demonstrated that, harvesting resulted in topsoil mean moisture decreased, temperature increased yet, both total nitrogen and total available nitrogen increased in the first year following harvesting, and decreased in the second year. Ammonium and nitrate changed complexed. Spatial heterogeneity for topsoil moisture decreased after harvesting, however, which was largely affected by the vegetation growth seasonally. Which for soil temperature increased with harvesting intensity enhanced. Soil nutrients heterotgeneity mainly increased in the first year following harvesting and then decreased. Spatial correlation distances for topsoil resources were mainly less than 20m; soil moisture mean ranges in disturbed plots were more than the control in the first year only. Range for soil temperature increased with harvesting intensity increasing. Soil nutrients ranges represented different trends in different plots. Topsoil moisture mean structural variation ratio [C/(C+C₀)] decreased with harvesting intensity, while there was no rule for soil temperature, and the ratio for nutrients in clear-cutting plot increased firstly while decreased subsequently, however, there is also no rule for cut 50% basal area plot.Kriging maps comparing suggested harvesting had an obvious influence on spatial pattern for soil moisture and temperature in the spring. Harvesting leaded to a decrease in soil moisture spatial pattern, which was more fragmented in spring than summer. Harvesting strengthened the intensity of spatial pattern for soil temperature, which was stonger in the spring. Spearman rank correlation test implied that, harvesting propelled the spatial correlation to create for soil nutrients, however, which were related substantial nutrients considered.