云冷杉林林隙内倒木腐烂等级及其形成的微立地类型对土壤理化性质的影响

为揭示倒木腐烂等级及其形成的微立地类型对土壤理化性质的影响,分析了小兴安岭凉水国家级自然保护区谷地云冷杉林由倒木形成的林隙内不同腐烂等级倒木形成的3种微立地(丘顶、坑底和倒木下)的土壤理化性质(容重、毛管孔隙度、总孔隙度、毛管持水量、饱和持水量、土壤有机碳、全氮、全磷、有效磷、速效钾和pH值)和化学计量特征(C/N、N/P和C/P)的差异.结果表明: 倒木腐烂等级对土壤物理性质的影响不显著,而倒木形成的微立地类型对其影响显著.除土壤饱和持水量外,倒木下的其他土壤物理性质均最好,坑底最差;随着倒木腐烂等级的上升,除有效磷外的其他土壤养分含量呈显著上升趋势;3种微立地中,坑底土壤养分含量最低,pH最高;随倒木腐烂等级的上升,3种微立地浅层土壤C/N、N/P和C/P下降,而丘顶和坑底深层土壤C/N上升,N/P和C/P下降,C/P的变化趋势与土壤有效磷的一致.综上,随倒木腐烂等级的提高,土壤养分含量显著增加,且不同类型微立地之间差异明显,其中坑底始终最低.

Effects of decay level of fallen trees and their formed microsite types on soil physicochemical properties in a spruce-fir forest

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.