恢复措施对皆伐油松林团聚体活性有机碳含量的影响——以黄土丘陵区松峪沟流域为例

Effects of restoration measure on labile organic carbon in aggregates after clear-cutting Chinese pine forest:A case study of Songyugou Watershed of the Loess Plateau

团聚体中的活性有机碳对土壤质量改善以及碳库动态平衡具有重要意义。为了研究皆伐后土壤团聚体活性有机碳的分布状况,本实验选取黄土高原典型油松林为对象,以未皆伐人工油松林为对照,采用高锰酸钾氧化法研究皆伐后不同恢复植被群落(幼林、撂荒、灌木)地表0~20 cm层土壤团聚体中活性有机碳变化特征。结果表明:1)研究区土壤以大团聚体(>250μm)为主,自然恢复的灌木地以及撂荒地大团聚体质量分数显著增加(P<0.05)。2)有机碳质量分数随团聚体粒径的增大而增加,大团聚体是有机碳积累的主要场所,并且自然恢复的灌木地团聚体有机碳质量分数最高。3)研究区油松林团聚体低活性有机碳质量分数>中活性有机碳质量分数>高活性有机碳质量分数,大团聚体活性有机碳质量分数大于微团聚体。研究表明,皆伐会造成团聚体有机碳趋于活化,其中自然恢复的灌木地活性有机碳质量分数显著增加。本研究还进一步发现大团聚体中的高活性有机碳能更好地预测土壤碳库变化。

[Background] Labile organic carbon（ LOC） is an important factor of soil organic carbon pool,and it can be more sensitive to environment change than any other factor. LOC in aggregate significantly influences soil quality and protection of carbon pool. In order to achieve the scientific management of restoration communities after clear-cutting,it is of great significance to investigate the relationship between soil aggregates and LOC in the area. [Methods] Concentrations of soil aggregates and LOC of restoration communities in Chinese pine plantations of the Loess Plateau after clear-cutting were investigated. There were 3 types of restoration community（ shrub land,abandoned forestland and young plantation land.） and no clear-cutting forest as control（ CK）. Undisturbed soil samples were collected at 0- 20 cm soil layer,the volume fraction of aggregate were tested using wet screening,theconcentrations of soil total organic carbon were determined using H2SO4-K2Cr2O7 oxidation,and the concentrations of soil LOC were measured using KMn O4 oxidation. Analysis of variance and linear regression analyses were done using SPSS（ 12. 0）. [Results] 1） Macro-aggregate（ 250 μm） was dominant in aggregate composition. Compared with CK,the types of restoration community after clearcutting presented significant effects on the distribution of aggregates. The percentage of micro-aggregate significantly decreased（ P〈0. 05） while that of macro-aggregate significantly increased（ P〈0. 05） in shrub land and abandoned forestland. Aggregate composition in young plantation land showed no significant changes. 2） The concentration of aggregate organic carbon increased with aggregate size increasing. There was the highest concentration of organic carbon in shrub land. The concentration of aggregate organic carbon was more sensitive than that of bulk soil organic carbons to different type of restoration community. 3） The concentration of LOC in soil aggregate decreased with the improvement of labile state,and LOC concentration of macro aggregate was greater than micro aggregates. Compared with CK,the organic carbon of soil aggregate became more highly labile under different restoration communities. The concentration of aggregate LOC significantly increased in shrub land, and the concentration of LOC in macro-aggregate was more sensitive to different type of restoration community than that in any other aggregate size. 4） Results of correlation analysis showed that LOC in aggregates presented a significant correlation with organic carbon in bulk soil. The correlation of LOC in macroaggregate with organic carbon in bulk soil was better than micro-aggregate. Highly LOC showed better correlation with organic carbon in bulk soil than lowly LOC. Therefore,highly LOC in macro-aggregate correlated best with organic carbon in bulk soil. [Conclusions] These results proved that different type of restoration community resulted in soil organic carbon unstable,and aggregate LOC in shrub land significantly increased. To some degree,our results uncovered the distribution characteristics of soil aggregate LOC in the Loess Plateau and indicated the effect of clear-cutting on aggregate labile organic carbon. According to these results, shrub land in restoration community can be a considerable management measure after clear-cutting Chinese pine forest in the Loess Plateau. Based on previous researches,our findings indicate that highly LOC in macro-aggregate can be a better index for measuring the dynamic of soil organic carbon than LOC in bulk soil.