马尾松人工林林窗对土壤团聚体及有机碳分布的影响

以四川宜宾39年生马尾松人工林人工采伐形成的不同大小林窗为对象，研究林窗对土壤团聚体的组成、有机碳及活性有机碳含量和储量的影响.结果表明： 土壤团聚体组成以>2 mm团聚体为主，其含量占团聚体总量的51.7%～78.7%.>5 mm土壤团聚体有机碳和活性有机碳含量与土壤总有机碳和总活性有机碳含量相关性最高，且有机碳及活性有机碳含量和储量均较高，是该地区土壤有机碳固定的特征团聚体.马尾松林窗形成后，土壤总有机碳及各团聚体有机碳含量普遍降低，但1225 m²林窗有机碳储量略高于林下；总活性有机碳含量仅225和400 m²林窗较马尾松林下高，总活性有机碳储量225、400、900和1225 m²林窗较马尾松林下高，其余面积林窗低于林下.这表明合适的林窗面积可以增加土壤有机碳及活性有机碳积累.林窗大小显著影响到团聚体的组成、有机碳及活性有机碳含量和储量.其中，1225 m²林窗土壤有机碳含量和储量均最高，活性有机碳储量也较高，且团聚体组成较好，是比较适宜的林窗面积.

Effects of gaps on distribution of soil aggregates and organic carbon in Pinus massoniana plantation.

The effects of forest gap size on the distribution of soil aggregates, organic carbon and labile organic carbon were investigated in a 39-year-old Pinus massoniana plantation in Yibin, Sichuan Province. The results showed that the composition of soil aggregates was dominated by particles >2 mm, which accounted for 51.7%-78.7% of the whole soil samples under different sized forest gaps and beneath P. massoniana plantation. Soil organic carbon content and labile organic carbon content in >5 mm aggregates were significantly positively correlated with the soil organic carbon and labile organic carbon contents. Furthermore, the amounts of organic carbon and labile organic carbon storage >5 mm particles were higher than those in other size particles. Therefore, particles >5 mm of aggregates dominated the soil carbon pool. Compared with those P. massoniana plantations, the contents of organic carbon in aggregates and total topsoil decreased during the formation of forest gaps, whereas the soil organic carbon storage under 1225 m² gap was higher. In addition, the soil labile organic carbon content under 225 and 400 m² gaps and the labile organic carbon storage under 225, 400, 900 and 1225 m² gaps were higher than those the plantations, but were lower than under the other gaps. It was suggested that an appropriate size of forest gap would increase the accumulation of soil organic carbon and labile organic carbon content. The size of forest gap had significant effects on the distribution of soil aggregates, organic carbon and labile organic carbon. The soil sample under 1225 m² gap had the highest organic carbon content and storage and a better aggregate proportion, and the higher labile organic carbon storage. Therefore, it was suggested that 1225 m² gap might be an optimal logging gap size.