摘要：林地水土保持效应的定量研究有助于深入了解植被水土保持机理并提升水蚀区植被重建水平。传统的研究多基于植被类型，或者植被的水平和垂直分布密度，综合考虑三维空间分布的指标应用鲜有报道。本研究使用林地植被覆盖度和叶面积指数的乘积作为绿量(LVV)表征植被三维空间分布，计算林和草的绿量和（LVV和）和结构化绿量S3作为小区绿量指标（统称LVV），结合中国南方典型水土流失区福建省长汀县河田镇林草试验小区2007-2010年144场侵蚀性降雨和水土流失观测数据，以林草小区径流深度和土壤流失量与对照小区的比值分别作为保水效应RE和保土效应SE，分析了单场降雨下5个林草小区LVV与 RE和SE的关系，建立了次降雨下绿量与保水、保土效应值的二次多项式关系模型，率定了模型曲线转折点的LVV值，并比较了不同关系类型的转折LVV值和降雨特征。结果表明，次降雨下绿量与保水、保土效应值的关系曲线呈下降、先降后升、先升后降和上升这四种类型，我们称为林草小区的四种水土保持效应。LVV-RE和LVV-SE各效应类型对应的降雨场次并不等同。总体上试验小区植被的保土效应较之保水效应显著，其中大部分呈现保持水土正效应。当雨强较高时（如降雨侵蚀力R = 163 MJ mm/ha h，最大30分钟雨强I30 = 14 mm/h），植被主要发挥保持水土正效应，反之主要显示负效应（如R = 85 MJ mm/ha h，I30 = 12mm/h），当雨强低于正、负效应的一定阈值时（如R = 48MJ mm/ha h，I30  = 10 mm/h），出现明显的效应逆转。次降雨尺度试验小区林草的保水和保土效应的平均转折LVV在S3模型中为0.8;在S和模型中为1.8。这些研究结果可为水土保持问题的深入理解和管理决策提供重要参考。

关键词：径流; 泥沙; 森林; 效应; 转折绿量

Abstract: The quantitative study of plot forest and grass on soil and water conservation  helps to deepen the understanding of Vegetation mechanism on soil and water conservation and to improve the level of water erosion area vegetation reconstruction. The traditional study based on vegetation types, or vegetation to the horizontal and vertical distribution density, comprehensive consideration of the three dimensional space distribution of index application few reports. This research use forest land vegetation coverage and leaf area index as the product of live vegetation volumn(LVV). Characterization of three-dimensional spatial distribution of LVV.Sum the LVV of forest and grass(LVVSM) and Structured live vegetation volumn S3 as live vegetation volumn index of experiment plots (Referred to asLVV),with China’s Southern Typical Soil Erosion Area 144 times aggressive rainfall and water and soil loss observation data in 12 experimental plots built in early 2007-2010 in Hetian town,Changting county,Fujian province,using the ratio of runoff depth and soil loss on forest and gress plots and controlled area as water retention effect of RE and SE soil conservation effect, analysis of individual rainfall under 5 forest area LVV and RE and SE, Establishment of a rainfall amount of LVV and Water conservation, soil conservation effect value of two degree polynomial model, Identification of the model curve of turning point LVV value and to compare the different relation types of turning LVV value and rainfall characteristics. The results show that,The relation curve about time rainfall amount of LVV and Water conservation, soil conservation effect value Declining, decreased at first and then increased, rising and descending and ascending the four types, We called four kinds of soil and water conservation effect of the forest area of four kinds of soil and water conservation effect. The effect of LVV-RE and LVV-SE types corresponding to rainfall events is not the same. The overall experimental plot of vegetation soil conservation effect than water effects, most of which is water and soil conservation effect. When the rain intensity is high (such as R = 163 MJ mm / ha h, I30 = 14 mm / h), play a major role in soil and water conservation vegetation effect, and the main show negative effects (such as R = 85 MJ mm / ha h, I30 = 12mm / h), when the rain intensity are below certain threshold, negative effects (such as R = 48MJ mm / ha h, I30 = 10 mm / h), apparent effect reversal. Time scale the experimental plot of grass rain water and soil effect of the turning point in an average LVV S3 model is 0.8; In S and model for 1.8. These research results provide a better understanding of the problems of soil and water conservation and management decision provides important reference.

Keywords:Runoff; Sediment; The forest; Effect; Turning live vegetation volumn