灰质白云岩土壤有机碳的团聚体保护

采集喀斯特地区灰质白云岩发育的乔木林下土壤,全部湿筛分为>5mm,5～2mm,2～1mm,1～0.5mm,0.5～0.25mm共5个粒级团聚体,再将5个粒级团聚体进行碳水化合物提取后后再次分别湿筛,收集>5mm,5～2mm,2～1mm,1～0.5mm,0.5～0.25mm共5个粒级的团聚体样品.对两次湿筛中5个粒级的土壤分别进行团聚体含量、土壤有机碳、土壤可氧化态有机碳测定,分析土壤团聚体稳定性与土壤有机碳、土壤可氧化态有机碳的关系.结果表明:灰质白云岩乔木林下土壤在经过提取碳水化合物的第二次湿筛后,大粒级团聚体(>5mm,5～2mm)向小粒级(2～1mm,1～0.5mm,0.5～0.25mm)转移;有机碳主要存在于较大粒级团聚体中,但各粒级团聚体有机碳并不随之转移;各粒径团聚体可氧化态碳含量均减少,但较大粒级(>5mm,5～2mm)可氧化态有机碳含量多,较小粒级(2～1mm,1～0.5mm,0.5～0.25mm)可氧化态有机碳含量少,故推测较大粒级团聚体(>2mm)保护土壤活性有机碳能力比较小粒级团聚体(<2mm)强.

Protection of Soil Organic Carbon in the Calcite Dolomite Aggregate

In order to study organic carbon protected in aggregates of soil developed from calcite dolomite under forest in karst area, soil samples were collected and wet sieved into five aggregate fractions: >5mm, 5～2mm, 2～1mm, 1～0.5mm, 0.5～0.25mm. After extracted carbohydrate, each fraction aggregate was wet-sieved into 5 fractions again. The contents of soil aggregate, oxidisable soil organic carbon, and soil organic carbon were measured, and the relationship between soil aggregate stability with soil organic carbon and soil oxidisable organic carbon was analyzed. The results showed that aggregates broke down from the large size(>5mm, 5～2mm) to small (2～1mm, 1～0.5mm, 0.5～0.25mm) but soil organic carbon was contained mostly in larger aggregate after the second wet sieving, however, soil organic carbon did not transfer while aggregate was broken. Soil oxidisable organic carbon content decreased in all fractions after the final seiving, but most oxidisable organic carbon was contained in the larger particle (>5mm, 5～2mm), and less in smaller (2～1mm, 1～0.5mm, 0.5～0.25mm). According to the results, it was assumed that soil oxidisable organic carbon was protected by the larger aggregate (>2mm).