黄土丘陵区坡面尺度不同整地方式的生态水文效应

Severe drought and water erosion induce poor habitat condition and great difficulty of vegetation restoration in the semiarid loess hilly area. A series of slope land-preparation measures were conducted extensively during vegetation restoration, targeting for improving the survivial rate and availability of plants. By this means, many typical land preparation types and micro-catchments were created, and the heterogeneities of landscape and microhabitats at slopes were increased. So far however, systematic research on the role of sloping land reshaping and preapration in ecohydrological processes are still lacking, and many key consequences and deep mechanisms remain unclear. In this study, therefore, a small typical loess hilly catchment in Dingxi, Gansu province is selected as the key study region. Based on field observation in situ, watershed investigation, sampling analysis, rainfall simulation experiment and mutilple statistical analysis, four typical land-preparation measures including reversed terrace, level trench, fish-scale pit and level bench will be used for further analysis. several key tasks are expected to be achieved. (1)To quantify and analyze the effect of land reshaping and preparation measures on soil properties and micro-habitats from stand and hillslope scales. (2)To detect the responses of rainfall infiltration, soil water content and water erosion processes to different land-preparation measures affected by various rainfall events and vegetation types. (3)To determine the role of different land-reshaping types and their distribution pattern at slopes in vegetation restoration and hydrological effects, and try to quantify the relationship between land-preparation measures, soil property and hydrological consequences of vegetation restoration. This results are expected to provide scientific references for sloping habitat improvement, erosion control and vegetation restoration in the semiarid Loess Plateau region.

干旱缺水和水土流失导致黄土丘陵区生境不良、植被恢复极为困难。为了改善这一状况，实践中广泛采用了多种坡面整地方式来提高植被恢复的成功率和有效性，从而塑造了许多坡面微型集水单元，增加了坡面景观和微生境的异质性。但有关坡面尺度不同整地方式影响生态水文和植被恢复效果的基础研究尚显不足，许多关键效应和影响机制不明。本项目以此为背景，选择甘肃定西黄土小流域，以定位观测为核心手段,辅以降雨模拟、采样分析、样地调查和资料搜集等方法，从立地和坡面尺度研究反坡台、鱼鳞坑、水平沟和水平阶等整地方式对土壤理化属性和微生境的影响；揭示不同降雨事件和植被类型影响下，降雨入渗、土壤水分和水土流失过程对不同整地方式的响应规律；阐明不同整地方式及其坡面分布特征对植被恢复及其水文效应的影响程度与作用机制；建立整地方式--土壤属性--植被恢复水文效应之间的定量表达。研究结果能为黄土高原坡地改良、水蚀防治和植被恢复提供科学依据。

干旱与侵蚀导致黄土高原生境脆弱、植被恢复困难，而不同整地方式有助于改善立地条件、提高植被成活率，但其深层次机理尚不清楚。本研究以此为背景，选择定西黄土小流域，基于定位监测、水文模拟和野外调查等各种手段，系统研究了反坡台、鱼鳞坑、水平沟和水平阶等整地方式对土壤、植被和生态水文过程的综合影响；并基于文献数据和集成分析，将相关研究拓展至全国和全球梯田分布格局及其综合效益评价。重要结果如下：.1．坡面尺度机理监测与模拟分析：⑴坡改梯和整地可显著增加土壤水，促进植被蒸腾耗水。梯田样地平均相对可提取水分别比坡面增加了325%、58.3%和37.5%；日蒸腾固碳量分别比坡面高9.26%、4.76%和20.4%。⑵整地对土壤环境和水文性质有积极改善作用。整地后，土壤养分如C、N分别提高8.78%和16.69%；土壤水分和水力学特性分别提升约13.4-14.6%和6-26.7%，；径流系数和侵蚀模数分别下降31.9%~60.5%和53.9%-84.7%。⑶ WEPP模型评价显示，二阶和三阶水平阶的减流率分别从6.5%增加到61.2%，从10.1%增加到69.7%；减沙率分别从1.1%增加到68.8%，从1.4%增加到82.3%。建议合理调控台宽和阶数比，促进减沙效益最大化。2．宏观尺度综合效益集成与评价：⑴ 中国国家尺度上，全国30个省级地区均发现梯田分布。基于随机效应模型和加权meta分析等方法，发现全国梯田平均减流和减沙率分别为48.9% 和53%，且区域之间差异不显著；5°以下的缓坡应以水平梯田和坡式梯田为主；25°以上陡坡地则应以水平沟和鱼鳞坑为主，中等坡度则适宜于当地的台阶式梯地。⑵ 全球尺度上，发现梯田广布亚、非、欧、北美、南美等各大洲74个国家，部分坡改梯工程已有数千年历史。发现全球梯田侵蚀防控效益最显著(11.46±2.34)，其次是消减洪峰径流(2.60±1.79)、生物量积累和生物多样性保护(1.94±0.59)、提高土壤水分蓄积量 (1.21±0.23)、提升土壤养分和土地生产力(1.20±0.48)。基于全球60例坡改梯负效应报告，发现弃耕（49%）、不合理土地管理（20%），低质量设计（18%），知识技能不足（10%）、等是突出制约因子。研究结果能为脆弱区水蚀防治和生态系统管理提供科学依据。