断陷盆地石漠化区植被恢复过程土壤供氮能力与策略

Due to special geology, climate and human activities, rocky desertification seriously happens in karst faulted basins. Vegetation restoration is considered to be the key measure of comprehensive administration of rocky desertification, but vegetation recovery is extremely slow, which may be attributed to low soil nitrogen (N) supply capacity and availability (the important limiting factor for vegetation growth). In the present project, a series of techniques including 15N tracing method and nuclear magnetic resonance will be conducted to determine the contents and rates of N transformation process of different soil N pools and the changes in soil properties following vegetation restoration in the rocky desertification region. Soil organic matter characteristics (i.e., quantity and quality) will be emphasized at different stages of vegetation restoration. The main objectives of this project are to: 1) study the characteristics, supply capacities and traits of different soil N pools and the affecting mechanisms; 2) evaluate the important role of organic matter in enhancing soil N supply capacity during the vegetation succession. Results of this investigate will be useful to improve our understanding of soil N cycling and the correlation between soil N availability and eco-environment change following vegetation restoration, which can supply the theoretical basis of ecological recovery, renovation and reconstruction of rocky desertification in karst faulted basins.

受特殊地质、气候和人类活动等影响，断陷盆地石漠化发生严重，植被恢复是石漠化综合治理的核心环节。值得注意的是，石漠化区植被恢复缓慢，其中土壤氮素供应是主要的限制因子。本项目采用15N标记和核磁共振等方法，测定断陷盆地石漠化区植被恢复过程中不同演替阶段土壤不同形态氮库含量、转化过程速率以及土壤理化性质变化，重点关注演替过程中土壤有机物特性(数量和质量)，以明确石漠化区植被恢复过程中土壤氮素形态特征、供氮能力和策略及其影响机制，评估石漠化区植被恢复过程中土壤有机物特性在供氮能力的重要作用。通过本项目研究结果，认识断陷盆地石漠化植被恢复过程中土壤氮素循环规律与生态环境变化之间的关系，为断陷盆地石漠化区生态恢复、整治和重建提供理论依据。

本项目针对喀斯特断陷盆地植被恢复缓慢，土壤氮素供应可能是重要的限制因子这一问题，通过调查不同植被恢复阶段土壤氮转化过程速率及其与地形和土壤发育强度的关系，评估了土壤无机氮供应能力与制约因子。结果发现，随着植被恢复进行，土壤矿化和硝化等过程速率显著提高，无机氮供应能力增加且以硝态氮为主，在此过程中钙元素是最重要的影响因子。值得注意的是，土壤无机氮供应能力受地形和土壤发育强度的显著影响。随着坡度和土壤发育强度的增加，土壤氮有效性下降，这主要归于土壤粘粒和铁铝氧化物等增加，抑制了矿化和硝化等速率。土壤氮有效性的下降，导致石漠化区植被恢复进程具有较大差异。本项目研究结果，阐明了断陷盆地石漠化植被恢复过程中土壤氮素循环规律与生态环境变化之间的关系，为断陷盆地石漠化区生态恢复、整治和重建提供理论依据。