石漠化区植被恢复过程凋落叶分解特征及其对土壤有机碳/氮的影响——以重庆中梁山为例

运用凋落物分解袋及样品室内分析的方法，研究了石漠化脆弱生态区植被恢复不同阶段主要建群种凋落叶分解及有机碳、氮释放动态及其与土壤团聚体有机碳、氮之间的关系。结果表明:(1)各植被恢复阶段凋落叶分解系数介于0.73～1.33之间，不同阶段之间表现为，草地<灌丛<乔木林<灌乔林，人工樟树林介于乔木林与灌乔林之间。(2)各植被恢复阶段凋落叶有机碳、氮净释放率介于58.5%～72.9%与21.2%～63.9%之间，有机碳在分解期间表现为净释放，有机碳、氮释放率随植被恢复年限的延长呈增加的趋势。(3)凋落叶分解与养分释放对土壤有机碳、氮含量的提高有促进作用。其中，凋落叶分解系数与0.25～1 mm、<0.25 mm粒径团聚体轻组有机碳、氮之间关系密切。在植被恢复过程中，凋落叶分解速率及有机碳、氮释放率随恢复年限延长而呈增加趋势，凋落叶分解对土壤有机碳、氮有重要影响，轻组有机碳、氮优先向小粒径团聚体输入，小粒径团聚体在土壤有机碳、氮积累中有重要作用。凋落叶分解一方面能为植物生长提供养分，同时也促进土壤有机质的形成与积累，植被恢复过程中应加强水土保持、提高土壤层的养分保蓄与抗水土流失能力。 

Leaf litter decomposition characters and impact on soil organic carbon/nitrogen in different vegetation restorations of karst rocky desertification: An example of the Zhongliang mountain in Chongqing

Restoring vegetation and improving soil quality is key to the control of rocky desertification. Soil organic carbon/nitrogen is not only the key component of soil quality, but also the basic role in the soil fertility system. In this study the Shiqing village in Nanchuan, a typical man-made vegetation restoration base, and the Zhongliang mountain in Beibei, a typical natural vegetation restoration pattern, were chosen as the study sites. In these areas, some typical sample plots were selected based on the field investigation and leaf litter of dominant plant species was collected. Then the treated leaf litter was filled into litter bags and was buried in the respective sample plots. At the same time, some 0-10 cm layered soil samples were collected in the vicinity of buried litter bag site in every experimental plot. In order to probe into leaf litter decomposition characters in the process of vegetation recovery, and the impact of leaf litter decay on soil organic carbon/nitrogen accumulation and nitrogen supply in karst rocky desertification areas, leaf litter decomposition rate of dominant plant species and organic carbon/nitrogen release rate were examined using the litter bag burying method, and the correlation between leaf litter decomposition and soil organic/nitrogen was analyzed in this study. On the basis of this analysis, this work discussed the key aggregate-size in the process of organic/nitrogen accumulation. The main results are as follows, the coefficient k of leaf litter decomposition varies from 0.73 to 1.33. On different sampling lands, the k value shows a tendency of grass land < brush land < arbor land < brush-arbor land .The k value of Cinnamomum camphora tree land is greater than arbor land and less than shrub-arbor land. With the extension of vegetation recovery, leaf litter decomposition rate increases. At the same time, organic carbon of leaf litter shows a releasing status during the decomposition period; and the release rate of organic carbon varies in 58.5%-72.9%, while the release rate of organic nitrogen varies in 21.2%-63.9%. The study results also show that the leaf litter decomposition rate and organic carbon/nitrogen release rates are controlled mainly by the initial nitrogen content and C/N ratio of leaf litter. Furthermore, there is a significantly positive relationship between the leaf litter decomposition rate and the light fraction organic carbon/nitrogen contents of the soil aggregate of 0.25-1 mm and <0.25 mm classes. Accordingly, the light fraction organic carbon/nitrogen is preference of the process to smaller aggregate-sizes in the leaf litter decomposition period. So in the process of accumulation, active organic carbon and nitrogen are in superior to the smaller sizes of aggregate, and the smaller size aggregates play an important role in this process. Therefore, the leaf litter decomposition is an important role in the vegetation recovery process. On one hand, the litter decomposition could provide nutrients for plant growth; on the other hand, it could promote the formation and accumulation of soil organic matters. In the process of vegetation succession, the work of soil and water conservation should be strengthened, so as to improve the capacity of absorption and storage of soil nutrients.