红壤丘陵区果园水蚀过程随种植年限演变规律

Orchard is widely distributed in the red soil hilly region. Serious soil erosion occurs in the initial development phase of orchard, but decreases and tends to be stable with the increasing cultivation years. Therefore, it is of great importance to study the evolution rule of water erosion process for orchard. Based on the long-term runoff observation experiment in the field plots and combined with the artificial rainfall simulation experiment, we will select the typical orchard (citrus orchard) in the red soil hilly region as the research object and investigate the changes of its rainfall, seasonal and interannual water and sediment with the increasing planting years using statistics and hydrology method. Several orchards with different planting years and similar underlying surface conditions will be selected to study the changes of land cover and soil anti-erodibility of these orchards with the increase of planting years through the method of spatial sequence instead of time successional sequence. The response mechanism of orchard erosion process to the planting years will be uncovered through the creation of the relationship model among the land cover, soil anti-erodibility and runoff and sediment yield, combined with the comprehensive analysis of simulated rainfall test data. The research results contribute to deepen the scientific understanding of the evolution law of water erosion process of orchards in the red soil hilly region, and provide theoretical basis for the prevention and control of orchard soil erosion.

红壤丘陵区果园分布广泛，种植初期水土流失严重，但随种植年限增加而减少并趋于稳定，研究其水蚀过程的演变规律具有重要价值。本项目以红壤丘陵区典型果园（柑橘园）为研究对象，以野外径流小区长期定位观测试验为基础，结合人工模拟降雨试验，采用统计学和水文学方法，分析次降雨、季节及年际水沙随果园种植年限的演变规律；选择下垫面条件相近、种植年限不同的果园，采用不同空间位置种植年限不同的果园代替同一地块不同种植年限果园的方法（空间代替时间方法），分析其地表覆被及土壤抗蚀性能随果园种植年限的演变过程；构建不同种植年限果园下地表覆被、土壤抗蚀性能与径流泥沙的关系模型，结合模拟降雨试验数据综合分析，揭示果园水蚀过程对种植年限的响应机制。该研究有助于深化对红壤丘陵区果园水蚀过程演变的科学认识，为红壤丘陵区果园水土流失防治提供理论依据。

果园开发建设过程尤其是规模化开发初期，剧烈的人为扰动导致园区植被、土壤结构破坏严重，加上植被结构单一、生态组分简单、区域内降雨量大且相对集中，导致红壤丘陵区坡地果园水土流失严重。本研究依托江西水土保持生态科技园生态果园试验区2001~2020年长期定位观测试验，研究了降雨波动与果园水土流失的关系，探讨不同降雨条件下地表覆被分布格局对果园水土流失的影响及其差异，分析果园水土流失在不同地表覆被条件下对降雨波动的响应规律，及其随果园种植年限的演变。结果表明，随着种植年限的增加，常规降雨指数对产流系数及土壤流失率的相对贡献率由63.9%下降至20.4%和79.8%下降至32.1%。而降雨波动特征参数对产流系数及土壤流失率的相对贡献率由36.1%提升至79.6%和20.2%提升至67.9%。林下生草措施对产流、产沙的削减效果最好，相比于果园清耕措施分别降低86.2%和98.4%；其次是林下套种经济作物，相比于果园清耕措施分别降低49.0%和38.6%。相比坡面产流，产沙对地表覆被分布格局的响应更为敏感。随降雨量的增加，地表覆被分布格局与产流产沙之间关系得到加强，尤其在大雨量事件下，地表覆被对产流产沙的调节作用更明显。降雨波动特征对坡面产流的相对贡献率与地表覆被分布格局指数（DLI和FDLI）呈现正相关关系；降雨波动特征对产沙的相对贡献率，与DLI和FDLI呈现负相关关系。对次降雨过程进行细化解析，强调降雨波动特征与果园水土流失之间的重要关联，有助于提高果园水土流失防治和预测预报。