Assessing the Impact of Forest Change and Climate Variability on Dry Season Runoff by an Improved Single Watershed Approach: A Comparative Study in Two Large Watersheds, China

Abstract

Abstract:Extensive studies on hydrological responses to forest change have been published for centuries, yet partitioning the hydrological effects of forest change, climate variability and other factors in a large watershed remains a challenge. In this study, we developed a single watershed approach combining the modified double mass curve (MDMC) and the time series multivariate autoregressive integrated moving average model (ARIMAX) to separate the impact of forest change, climate variability and other factors on dry season runoff variation in two large watersheds in China. The Zagunao watershed was examined for the deforestation effect, while the Meijiang watershed was examined to study the hydrological impact of reforestation. The key findings are: (1) both deforestation and reforestation led to significant reductions in dry season runoff, while climate variability yielded positive effects in the studied watersheds; (2) the hydrological response to forest change varied over time due to changes in soil infiltration and evapotranspiration after vegetation regeneration; (3) changes of subalpine natural forests produced greater impact on dry season runoff than alteration of planted forests. These findings are beneficial to water resource and forest management under climate change and highlight a better planning of forest operations and management incorporated trade-off between carbon and water in different forests.

Water budget and run‐off response of a tropical multispecies “reforest” and effects of typhoon disturbance

“…In other cases, baseflow remained the same after reforestation (e.g., Liu et al, ; Tennessee Valley Authority, ), suggesting a neutral trade‐off between the effects of changes in catchment‐wide retention and vegetation water use. The latter may also reflect a limited overall capacity to store moisture in the soil due to soil erosion during the preceding degradation phase, despite the fact that topsoil infiltration capacity improved after reforestation (Bruijnzeel, ; Hou et al, ; Liu et al, ; Scott et al, ).…”

“…Nevertheless, the fact that streamflow at Manobo became perennial in 1998, a very dry El Niño year that was preceded by three wetter years (Figure S6b), suggests that by 1998 the moisture infiltration and storage capacity of the soil may have increased sufficiently (cf. Y. Cheng et al, ; Hou et al, ; Krishnaswamy et al, ; J. Zhang, Bruijnzeel, Quiñones, et al, ).…”

“…The latter may also reflect a limited overall capacity to store moisture in the soil due to soil erosion during the preceding degradation phase, despite the fact that topsoil infiltration capacity improved after reforestation (Bruijnzeel, 1989;Hou et al, 2018;Liu et al, 2015;Scott et al, 2005).…”

“…Y. Cheng et al, 2017;Hou et al, 2018;Krishnaswamy et al, 2018;J. Zhang, Bruijnzeel, Quiñones, et al, 2018).…”

“…This is usually referred to as the “infiltration‐trade‐off” hypothesis (Bruijnzeel, ). Several examples of gradually improved streamflow regimes (reduced peaks, increased or longer dry‐season flows) after reforesting severely degraded land (Choi & Kim, ; Hou et al, ; Krishnaswamy et al, ; Krishnaswamy, Kelkar, & Birkel, ; Zhou et al, ) have suggested the validity of the trade‐off mechanism (cf. Y. Cheng, Ogden, & Zhu, ).…”