Climate and vegetation water use efficiency at catchment scales

Abstract

4 SAHRA (Sustainability of semi-arid hydrology and riparian areas), Global change is affecting the hydrologic response of landscapes in various ways. Understanding and predicting these effects on the water cycle are becoming increasingly critical (Jackson et al., 2001), but to date, there has been little progress in generating mechanistic relationships between climate, land use and hydrologic partitioning that can be broadly applied. Projected changes in surface temperature and precipitation dynamics will undoubtedly alter the runoff regime (Barnett et al., 2005) as well as runoff extremes (Milly et al., 2002; Dai et al., 2004). The sensitivity of annual stream flow (runoff) to changes in temperature and precipitation has been investigated empirically as well as theoretically (Arnell, 1996). Runoff sensitivity to climate change derived from the observational record has limited predictive capacity in light of non-stationarity of interdependent hydroclimatic variables and landscape features in a changing environment (Milly et al., 2008). Water balance models (Schaake, 1990; Dooge, 1992) usually consider the landscape to be invariant and their application to specific river basins relies on observations to calibrate the model parameters (Wagener, 2007). Both climate and land use are altering the landscape with concomitant changes in ecosystem structure and function (Walther et al., 2002) and regional hydrological cycles (Breshears et al., 2005). Although the hydrologic impacts of land use change imposed by humans have received considerable attention by hydrologists (e.g. Hurkmans et al., 2009), the impacts of natural large-scale vegetation shifts as a consequence of climate change are unclear (Allen and Breshears, 1998). Vegetation shifts are an important climate-ecosystem-hydrology feedback through their alteration of carbon, water and energy exchanges at the land surface (Adams et al., 2009). Although recent ecohydrological studies have focussed on understanding interactions between hydroclimatic variables and ecosystems response (e.g. Rodriguez-Iturbe and Porporato, 2004), as well as the effects of ecosystem structure on local-to-regional hydroclimate (e.g. Rinehart et al., 2008; Veatch et al., 2009), we lack a comprehensive theory of how vegetation will respond to changes in the water and energy balance of a region.Over short timescales, vegetation can respond adaptively to variations in climatic factors. Vegetation productivity, measured as net carbon uptake by the landscape or estimated from patterns of aboveground net primary production (ANPP), and growing-season actual evapotranspiration are strongly related (Webb et al., 1986). Since actual evapotranspiration typically is the largest component of many ecosystem water balances (Zhang et al., 2001), the inter-annual variability of catchment hydrologic response should be strongly related to ecosystem function and productivity. Thus, understanding vegetation response to inter-annual variability of climate and water availability should be central in any attempt t...

Climate-driven disturbances in the San Juan River sub-basin of the Colorado River

“…For example, Pribulick et al (2016) show non-linear declines in streamflow in response to vegetation and temperature changes, with enhanced responses in snowmelt-driven transects and where percent vegetation change was largest. Other research suggests that when water availability declines, plants adapt and become more efficient at using water (Troch et al, 2009), which is not incorporated in the approaches undertaken in this study or Pribulick et al (2016). Additionally, VIC model parameters that impact changes in water balances have inherent uncertainty under climate change (Bennett et al, , 2012, and some of these parameters, such as canopy overstory, are represented in a binary fashion, which is not necessarily indicative of the forest and shrubland mixtures observed during forest recovery.…”

Technical Note: A comparison of model and empirical measures of catchment-scale effective energy and mass transfer

“…Building on the analyses of Troch et al (2009 and Rasmussen (2012), we use the Model Parameterization Experiment (MOPEX) catchment data and remotely sensed net primary productivity (NPP) data to quantify climate, vegetation and catchment water balance interactions empirically across a broad spatial and climate space.…”

“…The EEMT framework was developed based on a rich history in the soil science literature from the initial conceptualization and semi-quantitative approaches used to describe and define soil forming factors (Dokuchaev, 1967;Jenny, 1941;Runge, 1973;Smeck et al, 1983) to later work that formalized these factors into quantitative energy terms (Volobuyev, 1964), and revisited in more recent work (Minasny et al, 2008;Phillips, 2009;Rasmussen, 2012;Rasmussen et al, 2005Rasmussen et al, , 2011Rasmussen and Tabor, 2007). This framework quantifies the drivers of critical zone evolution as the summation of energy and mass fluxes associated with soil and critical zone development, wherein development refers to chemical alteration, structure formation, and the layering, zonation, and organization of the weathered regolith.…”

“…This framework quantifies the drivers of critical zone evolution as the summation of energy and mass fluxes associated with soil and critical zone development, wherein development refers to chemical alteration, structure formation, and the layering, zonation, and organization of the weathered regolith. The summation of these fluxes as stated by Volobuyev (1964) and revisited by Minasny et al (2008) …”

“…nws.noaa.gov/oh/mopex) spanning the time period from 2000 to 2009 following the analyses of Troch et al (2009) and Brooks et al (2011) to estimate E PPT (E PPT-MOPEX ) and used MODIS data for the same 86 catchments to estimate E BIO (E BIO-MODIS ). The selected catchments span a broad climate space with substantial variation in water availability and vegetation cover (Duan et al, 2006).…”