赣南红壤丘陵区137Cs示踪土壤侵蚀对土壤养分元素的影响

赣南红壤丘陵区是我国土壤侵蚀与土地退化比较严重的地区,以南丰县为例,应用137 Cs示踪技术探讨不同土地利用方式下土壤侵蚀与养分元素的关系。结果表明:(1)湿地松林、桔园、水田3种土地利用方式作用下土壤中137 Cs与养分元素分布差异显著,在垂直剖面上,湿地松林137 Cs含量呈指数递减分布,水田与桔园137 Cs含量因人为干扰在耕层内均匀分布;有机质与137 Cs有相似的分布特征;全氮、碱解氮、速效磷、速效钾含量均呈现一定表聚性。(2)位于坡地的2种土地利用方式中,湿地松林137 Cs、全氮、碱解氮、速效磷、速效钾、有机质含量均表现为下坡>上坡>中坡;桔园137 Cs活度表现为中坡>下坡>上坡,全氮、碱解氮、速效磷表现为下坡>中坡>上坡,而速效钾、有机质最大值均出现在上坡。(3)相关性分析表明,土壤137 Cs与有机质、全氮、碱解氮显著正相关,表明小流域有机质、氮元素可能与137 Cs有相同的物理运移方式,pH与137 Cs显著负相关,速效磷、速效钾则与137 Cs不相关。(4)3种土地利用方式中位于小流域谷地的水田137 Cs、有机质、全氮、碱解氮含量最高,坡地上桔园坡面137 Cs与土壤养分元素含量均高于湿地松林地,表明一定程度的坡改梯桔园种植模式能有效缓解土壤侵蚀与养分流失,改善区域生态环境。

Effects of Soil Erosion on Soil Nutrient Elements Based on 137Cs Tracer in the Red Soil Hilly Region of Southern Jiangxi Province

The hilly region of red soil in southern Jiangxi is being faced with serious soil erosion and land degradation. In this study, we took the Nanfeng County as a case study to explore the relationships between soil erosion and nutrient elements under wetland pine forest, orange orchard and paddy field using the ¹³⁷Cs tracer approach. The results showed that:(1) There were significant differences in the distributions of ¹³⁷Cs and nutrient elements in soil with the three land use types. The contents of ¹³⁷Cs in soil of wetland pine forest decreased exponentially along with the vertical profile. While in the soils of orange orchard and paddy fields, the ¹³⁷Cs was evenly distributed in the plough layer due to human disturbance. The distribution of organic matter was similar with ¹³⁷Cs. The contents of total nitrogen, alkali nitrogen, available phosphorus and available potassium in the three land use types showed obvious accumulation in surface layer. (2) In the soil of hillside wetland pine forest, the contents of ¹³⁷Cs, total nitrogen, alkali nitrogen, available phosphorus, available potassium and organic matter were characterized by:downhill > uphill > mid-slope. While in the orange orchard soil, the activities of ¹³⁷Cs were mid-slope > downhill > uphill. The contents of total nitrogen, alkali nitrogen and available phosphorus showed downhill > mid-slope > uphill. And the maximum contents of available potassium and organic matter were found on the uphill. (3) Correlation analysis showed that ¹³⁷Cs was positively correlated with organic matter, total nitrogen and alkali nitrogen, indicating that organic matter and nitrogen in small watershed might have the same physical migration mode as ¹³⁷Cs. The pH value was significantly negatively correlated with ¹³⁷Cs. While there were no significant correlations between the contents of available phosphorus and available potassium and ¹³⁷Cs. (4) Among the three land use types, the ¹³⁷Cs, organic matter, total nitrogen and alkali nitrogen contents in the paddy field of the small watershed valley were the highest. On the hillside, the contents of ¹³⁷Cs and soil nutrient elements in the orange orchard were higher than those in the wetland pine forest, indicating that the changing slopping-to-terraced orange planting patterns could effectively alleviate soil erosion and nutrient loss, and improve the regional ecological environment.