RESUMO
Through field survey and laboratory analysis, we examined the composition and fractal features of soil micro-aggregates in different types of treefall gaps and microsites (pit bottom and mound top) in broad-leaved Korean pine forest and spruce-fir-Korean pine forest. Results showed that the contents of soil microaggregates under the classes of 0.25-2 mm and 0.05-0.25 mm were higher in both forest types, ranging from 25.7% to 50.7% and from 27.0% to 42.8%, respectively, and that of <0.002 mm was the lowest, ranging from 4.4% to 8.9%. In the pit bottom and mound top of gaps, soil bulk density was higher in both forest types. Soil nutrient content in mound top was higher than that in pit bottom and was higher in broad-leaved Korean pine forest than spruce-fir-Korean pine forest. Soil microaggregates of <0.002 mm had no correlation with soil physical and chemical properties, whereas that of 0.25-2 mm and 0.002-0.02 mm had significantly positive and negative correlation with soil non-capillary porosity, total porosity, aeration porosity, organic matter, total phosphorus, total nitrogen and organic carbon, respectively. On the whole, soil fractal dimension (D) and the proportion of characteristic soil micro-aggregates (PCM) in broad-leaved Korean pine forest were larger than those in spruce-fir-Korean pine forest, and the ratio of soil microaggregates diameter (RMD) in mound top and pit bottom was increased in two forest types. Soil D and PCM had no significant correlation with soil physical and chemical properties, while RMD was negatively correlated with capillary porosity, total porosity, soil bulk density and aeration porosity. In two forest types, the formation of mound and pit microsites could decrease the larger size micro-aggregates and the stability of soil micro-aggregate, increase soil D and PCM, and signifi-cantly increase RMD. RMD could be used as a quantitative index of soil physical and chemical properties in pit and mound microsites of forest.
Assuntos
Picea , Pinus , Carbono , China , Florestas , Fractais , SoloRESUMO
To reveal the effects of decay level of fallen trees and their formed microsite types on soil physicochemical properties, the differences in soil physicochemical properties (bulk density, capillary porosity, total porosity, capillary water holding capacity, saturated moisture capacity, soil organic carbon, total nitrogen, total phosphorous, available phosphorous, available potassium, and pH) and stoichiometry (C/N, N/P, and C/P) among different decay levels of treefalls and between different microsite types in the formed gaps by fallen trees were analyzed in a spruce-fir fore-st in a valley of Liangshui National Nature Reserve in Xiaoxing' an Mountains. The results showed that the effects of the decay levels of fallen trees on soil physical properties was not significant. In contrast, we found significant effects of the formed microsite types in soil physical properties. Except for saturated soil water holding capacity, the other soil physical properties were the best under the fallen trees and the worst in the pit bottom. Except of available phosphorus, the contents of the other soil nutrients exhibited a significant increase trend with the increasing decay levels of fallen trees. Among three microsites, the contents of soil nutrients were the lowest and pH were highest in the pit. As for the shallow soil layer, C/N, N/P and C/P of three microsites decreased with the increasing decay levels of fallen trees, while C/N in mound top and in pit bottom increased, N/P and C/P decreased, and the variation of C/P was consistent with that of available phosphorus. In conclusion, with the increasing decay levels of fallen trees, the contents of soil nutrients were signifi-cantly increased. There are significant differences of soil nutrients among different microsites, with the lowest values in the pit.
