气候影响下东北地区季节性森林融雪径流水文过程研究

Snow cover and snow melt affect the local climate environment, and has obvious feedback response for climate warming. At the same time, the hydrological effects under the interaction between snow and forest can effectively regulate the runoff, and prevent floods disaster in the spring. As the global climate warming, the study going into the hydrological process of snow cover and snow melt and its hydrological mechanism in the forest is the important scientific problems for ecological hydrology research in cold region. Northeast China is an important area where seasonal snow melt of forest takes place. It is obvious complexity that forest vegetation characteristics, topography, soil, etc. influence snow cover and snow melt process and runoff. Under the background of climate change it is an urgent need to understand snow melt mechanism and the function of runoff generation in forest on the process level. Through the sample plot scale experimental observation, the project will analyze various factors influencing snow cover and snow melt process and snowmelt runoff function, and then considering all the factors it will build slope snowmelt runoff model based on observation results of snowmelt hydrological process, and probe into the snow melt mechanism. By plan simulation, it will evaluate the effect of climate change and different forest management patterns on slope forest snowmelt runoff. The result will promote the development of ecological hydrology process mechanism research in cold temperate zone, and it will have the important practical significance and scientific value for water resources management, Hydropower engineering construction and forest management pattern in the basin or areas.

积融雪影响当地气候环境变化，并对气候变暖具有明显的反馈响应；同时，其与森林植被相互作用产生的水文效应可有效调节河流流量，防止春季洪涝灾害。随着全球气候变暖，深入研究森林中积融雪水文过程及其发生机制是寒区生态水文研究的重要科学问题。东北地区是发生季节性森林积融雪过程的重要区域，森林植被特征、地形、土壤等对积融雪过程及融雪产流的影响具有明显的复杂性，在气候变化背景下迫切需要从过程水平上理解森林积融雪机制及其融雪产流功能。本项目通过样地尺度的实验观测，分析影响积融雪过程及产流功能的各种因素，综合各影响因素并基于融雪径流水文过程的观测结果构建坡面融雪径流模型，探讨森林融雪径流发生机制，通过预案模拟、预测气候环境变化及不同森林经营模式对坡面融雪径流的影响，促进生态水文学过程机理研究在寒温带地区的发展，对流域或区域水资源管理、水电站等工程建设及森林经营模式具有重要的现实意义和科学价值。

积雪对气候变化的响应将会引起径流量和径流时空分配的较大变化。东北地区具有较大面积的森林植被，森林积雪、融雪过程对流域或区域生态环境建设和水文水资源管理具有重要的影响。项目依托小兴安岭生态站从样地尺度出发对森林积雪和融雪径流过程进行了调查、监测，深入分析了森林植被、地形、土壤、气候等对积雪和融雪径流的影响以及融雪径流产生过程中土壤温度和水分变化，构建了坡面融雪产流模型，对不同植被覆盖对融雪径流的影响进行了分析预测。结果表明：（1）森林对积雪、融雪过程具有明显的影响。云冷杉林的截雪量最大，积雪保存率最高；云冷杉红松林次之，白桦林最小；林内外积雪融化时间均在2月初，但林内融雪持续时间可达60 d；林内的降雪和积雪密度大多均小于林外，其差异不显著（P>0.05）。（2）森林积融雪过程受到叶面积指数、气象因素、地形等的影响。叶面积指数对一次降雪量、积雪厚度、雪水当量和积雪保存率均具有显著的影响，其与冠层截雪率和积雪保存率之间存在明显的对数函数关系。气象因素主要表现为气温、辐射、风速等对融雪和产流过程的影响。（3）积融雪过程中土壤温度和水分随着环境发生变化。5cm深处土壤温度与环境温度具有线性关系，且各土层温度在2月份均达到最低值，3月末至4月初基本恢复0℃。随土温升高土壤含水率增加，白桦林的土壤含水率回升较红松林早，其产流也较早。（4）不同森林类型下坡面融雪产流过程有差异。降雨前产流时间基本在3月下旬至4月上旬，流量大小依次为白桦林Ⅱ＞白桦林Ⅰ＞红松林Ⅱ＞红松林Ⅰ；冻融期间每次降雨均有径流峰值的产生，但产流量不随降雨量的增大而增大，而是在冻融初期具有产流最大峰值。（5）利用Brook90模型能够较好地模拟森林冻融期间的水文过程，且发现白桦林对融雪产流和冻融过程的影响较红松林显著。研究为东北地区发展可持续林水资源提供科学指导，并促进森林水文学及相关学科的发展。