关键词: 落叶松, 人工林, 皆伐迹地, 农田, 土壤碳, 土壤肥力

Abstract:

Soils from variable depths in larch (Larix gmelinii) forestlands, the adjacent clear-cut sites and farmlands were sampled and analyzed to determine the changes in soil C, fertility-related properties from deforestation-farming processes and their profiles in this paper. The results showed. 1) Average soil organic carbon (SOC) storage in the 0-20 cm soil layers of forestland from 4 sites was 93.0 t·hm^-2, and 57% and 24% higher than farmland and clear-cut site, respectively. However, the 20-80 cm soil layers in farmland usually had higher carbon storage than forestland and clear-cut sites (P <0.05), without significant difference in the latter two sites. The soil inorganic carbon (SIC) was three orders lower than the SOC storage, thus it imposed negligible influences on the total soil carbon budget although its variation was generally contrary to SOC; 2) Storages of N and alkaline-N in 0-20 cm soil layers in farmland were 52% and 65% lower than those of forestlands (P <0.05), and 30% and 86% lower than those of clear-cut sites (P <0.05), respectively. The deeper soils in farmland had higher storages than did those in forestland and clear-cut sites. The K storage in the 0-20 cm layers in farmland was 39% higher than that in the forest (P <0.05), but the differences became much smaller in the deeper soil layers. There were no remarkable influences in P storage in different soil layers over the different land utilizations (P >0.05). 3) There were no significant differences in soil pH and EC in different soil layers between forestlands, clear-cut sites and farmlands (P >0.05), but significant differences were observed in the bulk density (P <0.05). Soil bulk density of farmland in the 0-20 cm layers was 27% and 15% higher than that of forestland and clear-cuts sites, respectively, while the differences in deeper soil became not significant (P >0.05).4) Overall, land use changes could give greater influences on the surface soil than the deeper soil. For most of the tested parameters, variations between forestlands, clear-cut sites and farmlands in the surface soil layers differed from or even opposed to those in the deeper soil layers.

Key words: Larix gmelinii, forest plantation, clear-cut site, farmland, soil carbon, soil fertility