Modelling the potential role of forest thinning in maintaining water supplies under a changing climate across the conterminous United States

Abstract

Abstract:The goal of this study was to test the sensitivity of water yield to forest thinning and other forest management/disturbances and climate across the conterminous United States (CONUS). Leaf area index (LAI) was selected as a key parameter linking changes in forest ecosystem structure and functions. We used the Water Supply Stress Index model to examine water yield response under 18 scenarios that combine hypothetical LAI changes (+10%, ±20%, À50%, and À80%), uniform increases in temperature (+1°C and +2°C) and precipitation change (±10%), and four climate change scenarios projected by general circulation models (GCMs) for the year 2050. Approximately 2100 large basins produced approximately 2003 billion cubic metres of water annually from 2002 to 2007. Forest lands covered 23% of the land surface area, but contributed 43% of the total water yield for the CONUS. As a whole, water yield increased by 3%, 8%, and 13% when LAI was reduced 20%, 50%, and 80%, respectively, while water yield decreased by 3% when LAI increased by 20%. Temperature increases of 2°C alone could decrease water yield by 11%. A reduction of precipitation by 10% and 20% could result in a decrease of water yield by 20% and 39%, respectively. The direction and magnitude of water yield response to the combinations of LAI (+10%), climate warming (+1°C), and precipitation change (±10%) were dominated by the change in precipitation. Climate change projected by the four GCMs (CSIROMK2 B2, CSIROMK3.5 A1B, HADCM3 B2, and MIROC32 A1B) resulted in a large change in water yield (+18% to À64%) by 2045-2055 when compared with the baseline. A 50% reduction in forest LAI under the four GCMs scenarios could greatly mitigate or exacerbate future climate change impacts on water yield in forest-dominated watersheds with high precipitation. This study provides the first quantitative estimate of the effects of forest thinning options on water yield under future climate across the CONUS. Effective forest water management for climate mitigation should focus on those watersheds identified. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.

Ecohydrological processes and ecosystem services in the Anthropocene: a review

“…Ecohydrological processes are closely connected to many water-related ecosystem services including climate moderation, water supply and quality, and flood mitigation (Ellison et al 2012;Jackson et al 2008;Sun et al 2015a) at multiple scales from species to the globe (Fig. 2).…”

Forest Management Challenges for Sustaining Water Resources in the Anthropocene

“…Modeling tools must be able to account for complexity at the correct spatial and temporal scales [73] and they must include variables required to evaluate management options such as fertilization [74], prescribed burning, and thinning [75]. We should also expect that watershed ecosystems will continue to respond to global change in complex ways characterized as nonlinear and threshold response, some of which may be novel and unprecedented.…”

“…However, as with other natural disturbances, droughts are difficult to prepare for because they are unpredictable. Management actions such as thinning [75] and prescribed burning [94] are typically not implemented at a scale or intensity to offset climatic driving forces. Similarly, the growing conflict between managing for carbon vs. managing for water [95] will only increase as efforts to mitigate CO 2 emissions using bioenergy promote management of fast growing species [96,97].…”

Future Water Budgets and Water Supply Stress under Climate Change and Urbanization in the Upper Neuse River Basin, North Carolina, USA

“…2). WaSSI was designed and applied to the southeastern US at the 8-digit HUC watershed scale to estimate watershed water balances, carbon balances and water supply and demand on a monthly time step (Sun et al, 2011a;Caldwell et al, 2012;Sun et al, 2015). A user friendly version of model is available online athttp://www.forestthreats.org/research/tools/WaSSI.Users have the option to run multiple future scenarios to represent land use change (e.g., reforestation, urbanization) under historic climate or 13 historic and future climate scenarios .…”

“…The WaSSI model is an integrated, process-based simulator that describes key ecohydrological processes at a broad scale (Sun et al, 2011b;Caldwell et al, 2012;Sun et al, 2015). It simulates water and carbon balances, including Evapotranspiraton (ET), soil water storage, runoff or water yield (Q) and ecosystem productivity (GPP) for each of eight land cover types within a given watershed and then aggregates these fluxes to the basin scale.…”