南亚热带森林土壤碳库稳定性与碳库管理指数对模拟酸雨的响应

通过对土壤总有机碳(SOC)、易氧化有机碳(ROC_(333)、ROC_(167)、ROC_(33))、颗粒有机碳(POC)、微生物量碳(SMBC)、溶解性有机碳(DOC)的测定,探讨模拟酸雨(pH 3.0、pH 3.5、pH 4.0、对照CK)对鼎湖山三个不同演替阶段森林(季风常绿阔叶林、针阔混交林、马尾松针叶林)土壤碳库稳定性及碳库管理指数的影响。结果表明:模拟酸雨增加了总有机碳的含量和各组分活性有机碳的含量(P0.05),但酸雨在一定程度上抑制了土壤中微生物量与活性。土壤中各组分活性有机碳与总有机碳呈显著相关,其中ROC_(333)和POC的含量与SOC关系最为密切,相关系数分别为0.853、0.846;碳库管理指数(CMI)结果表明,碳库活度(L)及碳库活度指数(LI)随森林的正向演替有下降的趋势,CPI与CMI呈现相反的趋势。在土壤有机碳及部分活性碳组分增加,碳库活性降低的前提下,土壤碳库稳定性增加。从各项指标的变化幅度可以得出:南亚热带森林土壤随森林群落正向演替而对模拟酸雨响应有更加敏感的趋势,各指标间的敏感性表现为CMIR_(333)POCSMBCR_(167)R_(33)LIDOCCPISOC。

Effects of simulated acid rain on soil labile organic carbon and carbon management index in subtropical forests of China

Four gradients of simulated acid rain treatmentpH 3.0, 3.5, 4.0 and CK (lake water)] were designed to determine the effects of simulated rain on soil carbon stabilization and the carbon management index (CMI) in three subtropical forests at different successional stages. The stages are, a young pine forest (PF), a transitional mixed conifer and broadleaf forest (MF), and an old grow-growth broadleaved forest (BF) at the Dinghushan Nature Reserve. The soil organic carbon (SOC), readily oxidation organic carbon (ROC), particulate organic carbon (POC), microbial biomass carbon (MBC), dissolved organic carbon (DOC), and soil properties were analyzed. The results showed that the SOC, ROC, and POC contents increased with acid treatment. However, simulated acid rain restrained the activity of microorganism while the SMBC content showed the opposite trend. The analysis showed that ROC₃₃₃ and POC with SOC had highly significant correlations, with correlation coefficients of 0.853 and 0.846 respectively. Our results also indicated a significant correlation between other labile fractions and the SOC. The value of L and LI decreased with the progressive succession of forests while the rangeability of L and LI showed the same trend. It''s indicated the proportion of labile portion to non-labile portion decreased. The results also showed CPI and CMI increased with the progressive succession of forests and, thus, the BF soil pool was more stable. That''s due to BF soil has higher C sequestration and lower lability than MF and PF forests, so the carbon is easily to sequestrate and more stable if the carbon lability index decreased. Moreover, the LI was more sensitive than the carbon cool index (CPI) was. From the variation of indicators of the three forests, we can conclude that the response sensitivity of acid rain showed an increasing trend with the progressive succession of forests. All the parameters investigated showed the following order of decreasing sensitivity:CMI > R₃₃₃ > POC > SMBC > R₁₆₇ > R₃₃ > LI > DOC > CPI > SOC.