山西太岳山不同林龄油松林土壤有机碳稳定性的变化特征

Stability of soil organic carbon changed with forest age in Pinus tabuliformis plantations in Mt.Taiyue,Shanxi

【目的】分析不同林龄油松林土壤有机碳及其组分的变化特征,为揭示维持油松林土壤有机碳稳定性的生物学机理提供理论依据。【方法】以山西太岳山林区40,80和110年生的油松林为研究对象,测定不同林龄油松林土壤有机碳及其组分(高氧化活性有机碳(F1)、中氧化活性有机碳(F2)、低氧化活性有机碳(F3)、稳定有机碳(F4))含量、pH、全氮含量、全磷含量、阳离子交换量、土壤酶活性和土壤粒径分布,分析不同林龄油松林土壤有机碳的稳定性和土壤理化性质的变化特征。【结果】土壤有机碳含量随林龄的增加而增大。难被氧化分解的有机碳组分(F3和F4)占总有机碳的70%以上,且所占比例随林龄的增大而增高;易被氧化分解的有机碳组分(F1和F2)占总有机碳的30%以下,随林龄的增大占比总体降低。40,80和110年生油松林在0~10 cm土层土壤有机碳的稳定系数分别为2.69,5.77和6.60,在10~20 cm土层分别为3.42,5.90和6.36。随着林龄的增加,土壤全氮含量、阳离子交换量、β-1,4-葡萄糖苷酶和纤维二糖水解酶活性呈增大趋势;在0~10 cm土层,土壤黏粒和粉粒含量呈降低趋势,土壤砂粒含量呈增大趋势。地表凋落物现存量与土壤有机碳含量呈显著的正相关关系,与F4呈极显著正相关关系,影响土壤总有机碳的积累与稳定。逐步回归分析结果显示,F1主要受全氮、阳离子交换量、粉粒含量、砂粒含量和β-1,4-葡萄糖苷酶活性的综合影响;F2主要受pH和β-1,4-葡萄糖苷酶活性的综合影响;F3主要受粉粒含量、β-1,4-葡萄糖苷酶活性和纤维二糖水解酶活性的综合影响;F4主要受pH、全氮、黏粒含量、粉粒含量和砂粒含量的综合影响;总有机碳主要受pH、全氮、全磷和阳离子交换量的综合影响。【结论】当油松林林龄为40~110年时,随林龄的增加,土壤理化性状和生物学性状均得到改善,林龄越高,土壤有机碳固持能力越强,土壤有机碳库越稳定。

【Objective】The changing characteristics of soil organic carbon and its components in Pinus tabuliformis forests with different ages were analyzed to provide basis for revealing biological mechanism of maintaining stability of soil organic carbon in Pinus tabuliformis forests.【Method】Pinus tabuliformis forests at the ages of 40,80 and 100 years in Taiyue Mountain,Shanxi were selected.Soil organic carbon and its components(high oxidizing active organic carbon(F1),moderately oxidizing active organic carbon(F2),low oxidizing active organic carbon(F3)and stable organic carbon(F4)),pH,total nitrogen content,total phosphorus content,cation exchange capacity,soil enzyme activity and soil particle size distribution were measured.The stability of soil organic carbon and changing characteristics of soil physical and chemical properties in Pinus tabuliformis forests with different ages were then analyzed.【Result】The content of soil total organic carbon increased with the increase of forest age.More than 70%of total organic carbon was difficult to be oxidized and decomposed(F3 and F4),and the proportion increased with the increase of forest age.Less than 30%of total organic carbon was easy to be oxidized and decomposed(F1 and F2),and the proportion decreased with the increase of forest age.The stability coefficients of soil organic carbon were 2.69,5.77 and 6.60 at soil layer of 0-10 cm in Pinus tabuliformis forests at the ages of 40,80 and 110 years,and corresponding values were 3.42,5.90 and 6.36 at soil layer of 10-20 cm.With the increase of forest age,soil total nitrogen content,cation exchange capacity,β-1,4-glucosidase and cellobiose hydrolase activities showed an increasing trend.At soil layer of 0-10 cm,soil clay and silt content showed a decreasing trend,while soil sand content showed an increasing trend.There were significant positive correlations between surface litter standing crop and soil organic carbon content,and very significant positive correlations with F4,which affected accumulation and stability of soil total organic carbon.Stepwise regression analysis showed that F1 was mainly affected by total nitrogen,cation exchange capacity,silt content,sand content andβ-1,4-glucosidase activity,F2 was mainly affected by pH andβ-1,4-glucosidase activity,F3 was mainly affected by silt content,β-1,4-glucosidase activity,F4 was mainly affected by pH,total nitrogen,clay content,silt content and sand content,and total organic carbon was mainly affected by pH,total nitrogen,total phosphorus and cation exchange capacity.【Conclusion】With the increase of stand ages of 40-100 years,soil physical and chemical properties and biological properties were improved.Higher forest age led to higher organic carbon holding capacity and more stable soil organic carbon pool.