Modeling the eco-hydrologic response of a Mediterranean type ecosystem to the combined impacts of projected climate change and altered fire frequencies

Abstract

Global Climate Models (GCMs) project moderate warming along with increases in atmospheric CO 2 for California Mediterranean type ecosystems (MTEs). In water-limited ecosystems, vegetation acts as an important control on streamflow and responds to soil moisture availability. Fires are also key disturbances in semiarid environments, and few studies have explored the potential interactions among changes in climate, vegetation dynamics, hydrology, elevated atmospheric CO2 concentrations and fire. We model ecosystem productivity, evapotranspiration, and summer streamflow under a range of temperature and precipitation scenarios using RHESSys, a spatially distributed model of carbon-water interactions. We examine the direct impacts of temperature and precipitation on vegetation productivity and impacts associated with higher water-use efficiency under elevated atmospheric CO2. Results suggest that for most climate scenarios, biomass in chaparral-dominated systems is likely to increase, leading to reductions in summer streamflow. However, within the range of GCM predictions, there are some scenarios in which vegetation may decrease, leading to higher summer streamflows. Changes due to increases in fire frequency will also impact summer streamflow but these will be small relative to changes due to vegetation productivity. Results suggest that monitoring vegetation

Temporal and spatial variation in how vegetation alters the soil moisture response to climate manipulation

“…Given the temporal variation we uncovered, particularly in relation to OTC effects on volumetric soil moisture content (θ), species that inherently differ in phenology could respond very differently to changing climate Sherry et al 2007). Along these lines, recent eco-hydrological models better account for seasonal changes in vegetation cover or vegetation activity (e.g., Kondoh and Higuchi 2001;Tague et al 2009;Choler et al 2010).…”

Nitrogen critical loads and management alternatives for N-impacted ecosystems in California

“…A larger proportion of the streamflow volume will occur earlier in the year, and in snowmelt driven basins late winter snowpack accumulation is projected to decrease by 50% toward the end of this century (Miller et al, 2003). Low elevation catchments that are not dominated by snowmelt runoff but where runoff is largely controlled by vegetation water demand (e.g., chaparral), will likely experience decreased runoff as evapotranspiration rates increase (Tague et al, 2009).…”

“…In a warmer climate, the N CL for NO 3 À leaching in chaparral catchments may increase as runoff declines, resulting in a lower tendency to leach NO 3 À . However, in some scenarios, vegetation may decrease resulting in lower evapotranspiration and greater runoff (Tague et al, 2009) and presumably lower CLs for NO 3 À leaching.…”

Vulnerability of stream biota to climate change in mediterranean climate regions: a synthesis of ecological responses and conservation challenges

“…Consequently, a higher streamflow reduction might occur than that expected if only precipitation is considered (Tague et al, 2009). In the Murray-Darling basin of Australia, for example, a 1ºC air temperature increase results in about a 15% of basin inflow decrease (Cai & Cowan, 2008).…”