中亚热带植被恢复过程中崩岗土壤性质分异特征

崩岗是我国南方红壤丘陵山区坡面沟道侵蚀后期发育而成的侵蚀地貌,探讨崩岗系统植被恢复过程中不同部位土壤性质分异特征,对揭示强度侵蚀环境下土壤环境效应以及指导崩岗区生态恢复具有重要借鉴意义。以闽西南长汀县濯田镇黄泥坑崩岗群内植被盖度分别为2%、20%和95%的3处毗邻崩岗为研究对象,研究各崩岗集水坡面、崩壁(顶部、中部及底部)、崩积体(上部和下部)和沟道出口等部位0—20 cm土壤理化性质的分异特征。结果表明:土壤容重、粉粒、pH、速效养分含量均表现为崩岗Ⅲ崩岗Ⅱ≈崩岗Ⅰ,土壤有机碳、全氮、全磷和全钾含量表现为崩岗Ⅲ崩岗Ⅱ≈崩岗Ⅰ。从集水坡面至沟道出口,土壤容重和砂粒含量呈增加→减少→增加趋势,粉粒和黏粒含量呈降低变化趋势,集水坡面和崩积体有机碳、全氮、全磷和全钾含量明显高于其他部位,在崩壁顶部及沟道出口最低。从集水坡面至沟道出口,铵态氮和硝态氮含量呈先增加后减少的态势,速效钾含量呈"V"型变化态势,最低值出现在崩壁底部,速效磷和pH呈增加态势。本研究表明,崩岗系统内土壤结构和土壤养分含量总体水平较差,不同侵蚀部位土壤性质存在明显空间差异,自然植被恢复过程对土壤特性有一定的改良效应。

Variation in soil property and its response to vegetation restoration in areas of collapse mounds in mid-subtropical China

The term of collapse mound, is called Benggang by local residents, represents the most severe eroded ecosystem in the red soil region of southern China. We studied the response of vegetation restoration on the characteristics of soil properties in different parts of the collapse mound system,which is an important reference to reveal the soil environmental effects under the intensity erosion environment and to guided the ecological restoration in the collapse mound area. Therefore, we selected three adjacent collapse mounds with different vegetation coverage (2%, 20%, and 95%) as the study object. The physicochemical properties of 63 soil sample plots were investigated in 7 sites, including upper catchment, collapsing wall (top, middle, and bottom section), colluvial deposit (upper and lower section), and channel outlet. The variation and correlation of soil properties were also analyzed. The results showed that the soil bulk density, slit content pH, ammonium nitrogen (NH₄⁺-N), nitrate nitrogen (NO₃^--N), available phosphorus (AP), and available potassium (AK) content decreased significantly, while the organic carbon (SOC), total nitrogen (TN), total phosphorus (TP) and total potassium (TK) content increased considerably with process of the vegetation restoration. From the upper catchment to channel outlet (via collapsing wall and colluvial deposit), the soil bulk density and sand content showed up-down-up trend, whereas the content of silt and clay showed decreasing trend. The content of SOC, TN, TP and TK in the upper catchment and the colluvial deposit were significantly higher than that other sites, whereas their contents were lowest in the top collapsing wall and channel outlet, respectively. The spatial distributions of NH₄⁺-N and NO₃^--N content showed downward and upward fluctuating trend, respectively, and the spatial variation of AK content showed a "V" tendency and its lowest content appeared in the bottom of the collapse wall, whereas AP and pH showed a significant increasing trend along with the runoff erosion direction. In summary, the soil structure and nutrient content were poor in the collapse mound ecosystem. and the soil physicochemical properties present obvious spatial differences in different erosion sites, they were improved by natural vegetation restoration.