不同经营类型毛竹林土壤活性有机碳的差异

以起始于1984年的长期不同经营类型毛竹林为研究对象,探讨了秋季毛竹林集约经营后土壤有机碳库的变化。结果表明:(1)集约经营后0—10 cm土层毛竹林土壤总有机碳、易氧化碳、水溶性有机碳和轻组有机质含量分别下降了8.64%,14.11%,8.29%,29.70%(0—20 cm),差异均达到显著水平。(2)两种毛竹林土壤各种碳的剖面特征均随土层深度的增加而呈下降趋势,但下降幅度不同。集约经营在一定程度上影响了毛竹土壤易氧化碳、水溶性有机碳的剖面特征。(3)土壤各活性有机碳之间,土壤总有机碳、易氧化碳、水溶性有机碳与土壤全氮、水解氮、速效K、Ca、Mg之间相关性均达到显著或极显著水平(水溶性有机碳与速效磷相关性不显著),轻组有机质含量除与速效钙极显著相关外,与其它土壤养分之间相关性均不显著。(4)集约经营降低了土壤易氧化碳碳素有效率、水溶性有机碳碳素有效率及土壤碳库活度,并在土壤剖面部分土层达到显著水平。因此,集约经营的毛竹林,通过配施恰当比例的有机无机肥,结合土壤垦复、除草、合理的竹株留养和采伐等综合竹林经营技术,以达到改善土壤质量和实现毛竹林可持续经营的目的。

Changes in soil active organic carbon under different management types of bamboo stands

Under the situation of increasing problems concerning with the environmental quality in forest land and the long-term productivity of forest, it was significant to develop and improve management strategies that maintain the function and protect the resources of soils. Changes of forest management strategies may lead to change in SOC quantity and quality. It was necessary to maintain a high SOC status for long-term land use due to the multiple beneficial effects of SOC on the soil nutrient states, structure and water holding capacity etc. The effects of different silvicultural practices on soil organic carbon were still poorly approached. Thus we performed the study on changes of soil organic carbon (SOC) in the Moso (Phyllostachys pubescens) stands among the long-term conversion of extensively managed and intensively managed in Fuyang County, Zhejiang province, where Moso were widely distributed. Bamboo stands of different management types, which were established in 1984, were designed to investigate the effects of intensive management on SOC. The results showed: total organic carbon (TOC), readily oxidation carbon (ROC), water soluble organic carbon (WSOC) and light fraction organic matter (LFOM) in 0-10cm soil layer were significantly decreased by 8.64%, 14.11%, 8.29% and 29.70%(0-20cm) respectively after intensive management. The vertical features of different soil organic carbon under two management types of bamboo stands were observed in decline trends with increasing of soil depths, while both of the decline scopes were different. The profile distribution of soil ROC and WSOC varied to some extent since intensive practice. These different fractions of labile organic carbon mentioned above were all interrelated, significantly or extremely significantly, and they also were well correlated with total N, hydrolysis N, available K, Ca, Mg (WSOC wasn't significantly correlated with available P), while LFOM wasn't significantly related to other soil nutrients except available Ca. Moreover after intensive management, availability of ROC, availability of WSOC and activity of carbon pool were decreased with significant level in part of soil layers. Therefore, to improve soil quality and achieve the goal of sustainable management of bamboo stands, a mixture of organic and inorganic manures with the proper ratio in bamboo stands should be applied under the conditions of intensive management, combined with ploughing, weeding, reasonable bamboo leaving and bamboo cutting, which could fulfill a high yield of bamboo shoot and bamboo culm, and maintain the ecological function of bamboo stands. The variation of results observed in soil C pool responded to different silvicultural methods in different studies may be due to variation in site types, original soil condition, timing and realization of forest managements, climatic factors, and/or interaction of some or all of these. However, this study along with the meta-analysis suggested that a categorical assumption of soil C loss under different forest management was unwarranted. Certainly, it was still needed to identify management methods that were most likely to cause or prevent SOC loss by further study. On the other hand, hydric soils may be much more sensitive to changes in temperature and moisture regimes as a result of silvicultural practices. Because the amount of the organic matter pool in mineral soils represents the potential to supply nitrogen, it is desirable to maintain organic matter in bamboo stands.