区域森林水源涵养功能评价模型的开发与应用

Development and application of a regional forest water conservation function assessment tool

区域尺度上毁林、虫害、火灾以及造林等多种类型森林变化伴随森林植被恢复生长,使森林及其水源涵养功能恢复具有时空累积性。而传统森林水源涵养功能评价方法难以直接刻画森林时空累积变化及其对水源涵养功能的影响,且存在模型计算量大、效率低等问题。针对上述难题,集成自主开发的森林恢复评价模型(ERA模型)与经典的综合蓄水法能力,结合GIS二次开发平台,设计与实现区域森林水源涵养功能评价模型(RFWCFAM)用于不同森林恢复情境下森林景观和森林水源涵养功能的时空动态评价和预测。该模型通过输入降水、植被类型、土壤、森林恢复措施等数据,生成森林变化、水源涵养量变化、恢复措施布局等空间分布图以及相应的统计数据,可以快速、准确定量评估区域尺度森林变化及其恢复过程中水源涵养功能的时空累积变化,辨识影响森林恢复的关键因子。区域森林水源涵养功能评价模型应用于杂谷脑流域,结果表明:1)2010年流域森林总水源涵养量为679.37 t/hm^(2);2)2010—2030年间在自然恢复和人工恢复情景下流域森林土壤层、枯枝落叶层、林冠层及总水源涵养量均呈增加趋势;3)人工恢复效果较自然恢复更明显,预计到2030年人工恢复措施下森林水源涵养总量较自然恢复措施下约高5.19%。本模型的开发及成功应用能够为林业部门和水资源管理部门快速准确评估森林恢复工程对水源涵养功能的提升效果提供高效的评价工具,同时为我国森林资源适应性管理提供科学依据,为水土保持工程的评价和管理提供科学支撑。

[Background]Multiple types of forest changes including deforestation,insect infestation,fire,and afforestation coupled with forest growth and restoration occur at a regional scale,which lead to the restoration effects of forest and associated water conservation capacity accumulate over space and time.The Zagunao watershed has suffered from deforestation in the past decades,which has severely reduced its water conservation capacity.This paper focuses on the forest change dynamics and the corresponding restoration of the water conservation capacity in this watershed under a series of ecological protection projects.However,traditional assessment tools of forest water conservation function lack the description of the spatial-temporal cumulation of forest growth and associated water conservation capacity,and are featured with complex computation,which impedes the evaluation on the effects of forest restoration on water conservation in a rapid and accurate way.[Methods]To address this issue,we innovatively developed the Equivalent Recovery Area(ERA)model for describing the hydrological function recovery with forest changes after forest deforestation and assessing the spatial-temporal dynamics of cumulative forest recovery after forest logging.Then,through combining the forest restoration evaluation model(ERA)and classic forest water storage function evaluation method(comprehensive water storage capacity method),this study took advantage of ENVI/IDL,ArcGIS Engine/C#.Net GIS to develop a GIS-based tool for assessing regional forest changes and associated forest water conservation function dynamics.The tool named Regional Forest Water Conservation Function Assessment Model(RFWCFAM)supports to evaluate the spatial-temporal changes of forest landscapes and forest water conservation functions under natural and artificial recovery scenarios.Charts and spatial distribution maps of forest changes,water conservation capacity dynamics,and restoration measures layout generated,after inputting precipitation,vegetation/forest,soil,and forest restoration measures data in RFWCFAM.[Results]This tool was successfully applied in the Zagunao watershed.According to the assessment,the EHFR(equivalent hydrological function recovery)coefficient increased in study area with the implementation of natural and artificial restoration measures from 2010 to 2030.The canopy,litter,soil and total forest water conservation capacity of the Zagunao watershed were about 129.8,25.96,523.62,and 697.37 t/hm^(2),respectively,in 2010,and all layers showed consistent upward tendencies from 2010 to 2030 under both natural restoration and artificial restoration scenarios.The artificial restoration measures yielded better effect on forest water conservation function than natural restoration.By 2030,the forest water conservation capacity of artificial restoration scenario is expected to be about 5.19%higher than that of natural restoration scenario.[Conclusions]The RFWCFAM has addressed the limitations of the traditional water resource assessment method and has been successfully applied and validated in the Zagunao watershed.Additionally,the RFWCFAM can provide an effective assessment tool to forest and water managers for evaluating the potential effects of forest restoration on water conservation function,along with scientific supports for adaptive forest management and soil and water conservation project evaluation and management in restorations of forest ecosystem functions in China.