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Understanding hydrological responses to reforestation is an important subject in watershed management, particularly in large forested watersheds (>1000 km²). In this study, we selected two large forested watersheds (Pingjiang and Xiangshui) located in the upper reach of the Poyang Lake watershed, Southeastern China (with an area of 3261.4 and 1458 km², respectively) to assess the effects of large-scale reforestation on streamflow. Both watersheds have similar climate and experienced comparable and dramatic forest changes during the past decades, but with contrasted watershed properties (e.g., the topography is much steeper in Xiangshui than in Pingjiang), which provides us with a unique opportunity to compare the differences in hydrological recovery in two contrasted watersheds. Streamflow at different percentiles (e.g., 5%, 10%, 50% and 95%) were compared using a combination of statistical analysis with year-wise method for each watershed. The results showed that forest recovery had no significant effects on median flows (Q50%) in both watersheds. However, reforestation significantly reduced high flows in Pingjiang, but had limited influence in Xiangshui. Similarly, reforestation had significant and positive effects on low flows (Q95%) in Pingjiang, while it did not significantly change low flows in Xiangshui. Thus, hydrological recovery is limited and slower in the steeper Xiangshui watershed, highlighting that watershed property is also important for determining hydrological responses to reforestation. This finding has important implications for designing reforestation and watershed management strategies in the context of hydrological recovery. [ABSTRACT FROM AUTHOR]

Flow regime refers to five elements of streamflow including flow magnitude, frequency, timing, duration and change rate. In spite of wide recognition of its critical significance in aquatic functions and ecosystem integrity, its responses to forest or land use change are rarely and quantitatively assessed. This paper used the Meijiang watershed (6983.2 km2), situated in the upper reach of the Poyang Lake basin, as an example to first demonstrate how flow regimes were altered by deforestation and then show if the altered flow regimes were possibly recovered by consequent reforestation. Two breakpoints (year 1968 and year 1985) with significant annual streamflow changes were detected, and they were then used to define three distinct periods including the reference or control period (1957 to 1967), deforestation (1968 to 1984) and reforestation (1985-2006). The paired year approach was then applied to quantitatively analyse the responses of flow regimes to forest cover changes. Both high flows (daily flows≧Q5%) and low flows (daily flows≦Q95%) were assessed. For high flows, the deforestation significantly increased the averaged magnitudes by 10.4%, increased the return periods (5-10 year) by 23.4%, advanced the averaged timings by 10.7 h and extended the averaged durations over the thresholds by 4 days. In contrast, reforestation delayed the averaged timings by 10.5 h, reduced the averaged duration by 5 days and decreased the averaged magnitude by 17.9%. Regarding low flows, the deforestation decreased the flow magnitudes by 30.1% with 30.5 day advancing in the average timings. To our surprise, however, low flows were not significantly changed by reforestation. All above results clearly demonstrate that flow regimes of both high and low flows were significantly altered by deforestation, and recovery of those alterations through reforestation may take much longer time than expected probably because of severe soil erosion and resultant loss of soil infiltration capacity after deforestation. [ABSTRACT FROM AUTHOR]

In forested watersheds, forest changes and climatic variability have been commonly recognized as two major drivers for streamflow variations. Previous research has separated their relative contributions but mainly focused on either deforestation and climate or reforestation and climate, but rarely with single studies on both. This study used the Meijiang watershed (6983·2 km2), situated in the upper reach of the Poyang Lake basin, as an example to quantify how climate and forest changes (both deforestation and reforestation) consecutively affect streamflow dynamics. Two methods, namely modified double-mass curves and sensitivity-based approach, were used in this study. Two breakpoints (years 1968 and 1985) with significant annual streamflow changes were detected, and together with the control period, they were then used to define three distinct periods: the control (1957-1967), deforestation (1968-1984) and reforestation (1985-2006) periods. Our results show that in the deforestation period, the average annual streamflow increment attributed to deforestation was 112·78 mm year−1, while the annual streamflow variation attributed to climate variability was −111·39 mm year−1. In the reforestation period, the average annual streamflow decrease caused by reforestation was −51·04 mm year−1, while the annual streamflow variation attributed to climate variability was 52·52 mm year−1. The sensitivity-based approach also provided similar results. The positive and negative values in the streamflow changes suggest offsetting effects between forest changes and climate variability in both deforestation and reforestation periods. The similar magnitudes of streamflow changes demonstrate that the hydrological effects of forest changes can be as great as those caused by climate change. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The long-term hydrological response to reforestation is critical to regional water management, especially in areas where large-scale reforestation has been practiced. In this study, we investigated the long-term hydrological response to reforestation in the 579 km2 basin in southeastern China through ground-based monitoring of water yield, sedimentation, vegetation cover and climate in the basin. The vegetation dynamics were also examined by remote sensing data (MSS, Landsat and AVHRR NDVI). We found that forest cover increased 23% or 13 593 ha from 1975 to 2002. Meanwhile, annual water yield decreased 86-88 mm from 1971-1983 (i.e. pre-reforestation) to 1984-2009 (i.e. post-reforestation). These decreases were significant statistically according to both regression and double mass analyses. Time series analysis demonstrated that there was a clear decline in annual sediment yield and an increase in annual evapotranspiration (ET) over the period from 1971 to 2009. We concluded that reforestation could significantly reduce annual water yield and sediment yield in the basin because of the forest cover change and forest growth. This conclusion is consistent with findings from widely paired-watershed studies and literatures published on the impact of reforestation in large watersheds. Our results also have important strategic implications and provide insight into more sustainable forest management practices for the future. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]