中国森林生态系统地表径流调节特征

径流调节是森林生态系统重要生态服务功能之一,包含着大气、水分、植被和土壤等生物物理过程,其变化将直接影响区域气候水文、植被和土壤等状况,是区域生态系统状况的重要指示器。在区域尺度上评估森林生态系统地表径流特征,对于科学认识和合理保护森林生态系统水源涵养功能具有重要意义。以森林生态系统定位监测数据为基础,探讨地表径流与降水,径流系数与植被的关系,建立径流系数与植被的回归方程,分析全国森林生态系统地表径流调节特征。结果表明:(1)各森林类型地表径流与降水相关性显著,其对地表径流的影响为37%—76%。此外,径流系数与植被也显著相关,其对径流系数的解释能力为27%—47%。(2)基于植被覆盖数据,通过植被与径流系数回归方程估算全国森林生态系统的地表径流调节特征。全国各森林生态系统径流调节能力存在差异,强弱顺序为:落叶针叶林落叶阔叶林针阔混交林常绿针叶林常绿阔叶林。

Forest ecosystem surface run-off regulation characteristics in China

Run-off regulation is an important forest ecosystem service. It is involved in natural processes, such as regional climate circulation, the hydrological cycle, vegetation growth, soil conditions, and other natural processes. It is also an important indicator of regional ecosystem status change. Water resources in China are limited, and precipitation is uneven over time and space. Many researchers have attributed the water conservation loss in China to long-term human interference and widespread conversions of land use and land cover. Previous studies have found that climate conditions, such as drought, severe storms, and temperature fluctuations, are the primary cause of water conservation change. Therefore, the current forest run-off regulation characteristics and their relationships with precipitation, surface run-off, and vegetation need to be investigated if water conservation levels are to improve. To date, many reviews of paired catchment studies have only observed the changes in run-off characteristics over a couple of years. A few studies have used paired catchment results to predict the hydrological responses to permanent vegetation change. A comparison of the long term annual results from regrowth, deforestation, and afforestation experiments have shown that it takes more than 5 years for a catchment to reach a new equilibrium after permanent changes in vegetation have taken place. However, deforestation experiments reach a new equilibrium earlier than afforestation experiments. Paired catchment studies have successfully revealed relationships between the percentage vegetation change and associated hydrological characteristics in relatively small catchments. The relationship between run-off and precipitation becomes significant when seasonal storms and/or rain precipitation are included in the analysis. Previous plot scale studies have also shown that vegetation reduced runoff compared to farmland and grassland ecosystems. At the catchment scale, paired catchment studies have also shown that afforestation further reduces run-off, but the hydrological responses associated with rainfall-runoff processes are very complicated. This investigation used a literature review, statistical regression, and geographic information system analyses to study the run-off characteristics of different forest ecosystems and has developed a run-off regulation regression model for ecosystems at the regional scale. We quantified the run-off regulation characteristics of forest ecosystems in China, and compared the regulation characteristics of different types of ecosystems. Our main conclusions are (1) There is a significant correlation between precipitation and surface run-off in different forest ecosystems, and there is a correlation between vegetation cover and the run-off coefficient. The proposed run-off regulation functions were based on the regression analysis of a large amount of measured data obtained from the literature. (2) The run-off regulation characteristics for forest ecosystems were calculated over 11 years (2000-2010) using vegetation data for China and a statistical regression function. The forest ecosystems had different run-off regulation functions. The run-off regulation capability decreased in the following way:deciduous coniferous forest > mixed deciduous broadleaf forest > mixed broadleaf-conifer forest > evergreen coniferous forest > evergreen broadleaf forest.