Increasing plant water stress and decreasing summer streamflow in response to a warmer and wetter climate in seasonally snow‐covered forests

Journal Article · Tue Oct 20 04:00:00 EDT 2020 · Ecohydrology

DOI:https://doi.org/10.1002/eco.2256· OSTI ID:1786429

Christensen, Lindsey ^[1]; Adams, Hallie R. ^[2]; Tai, Xiaonan ^[3]; Barnard, Holly R. ^[2]; Brooks, Paul D. ^[1]

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1. Department of Geology and Geophysics University of Utah Salt Lake City UT 84112‐0102 USA
2. Institute of Arctic and Alpine Research University of Colorado, Boulder Boulder CO 80309‐0260 USA
3. Department of Geology and Geophysics University of Utah Salt Lake City UT 84112‐0102 USA, Department of Biological Sciences New Jersey Institute of Technology Newark NJ 07102 USA

Abstract

Warming temperatures and precipitation changes are expected to alter water availability and increase drought stress in western North America, yet uncertainties remain in how concurrent changes in the amount and seasonality of precipitation interact with warming to affect hydrologic partitioning. We combined over a century of streamflow (Q) and climate observations with two decades of tree growth data and remotely sensed vegetation activity to quantify how temperature and precipitation interact to control hydrologic partitioning in the Front Range of Colorado, Boulder Creek Watershed. Temperature and precipitation significantly increased over the last five decades, with precipitation increasing primarily in winter (11.2 mm decade ⁻¹ ) and temperature increasing primarily during the growing season (0.12°C decade ⁻¹ ). In response to wetter winters and warmer summers, streamflow decreased −9.8 mm decade ⁻¹ , with largest declines occurring during summer and autumn baseflow (−8.4 mm decade ⁻¹ ). Spring warming was associated with increases in episodic, short spring melt events, earlier and slower snowmelt and an increase in fraction of precipitation available to plants (catchment wetting or W). Warming during the growing season resulted in an increase in the fraction of W lost as evapotranspiration (ET), earlier and lower peaks in remotely sensed normalized difference vegetation index (NDVI) and lower tree ring width index (RWI). These analyses highlight that vegetation is becoming increasingly water limited even as increases in precipitation and slower melt increase plant water availability. Further, catchment‐derived metrics like the Horton Index (ET/W) provide insight in to how simultaneous changes in temperature, precipitation and melt impact vegetation across complex watersheds.

• Sponsoring Organization: USDOE
• Grant/Contract Number: SC0006968
• OSTI ID: 1786429
• Alternate ID(s): OSTI ID: 1850973
• Journal Information: Ecohydrology, Journal Name: Ecohydrology Journal Issue: 1 Vol. 14; ISSN 1936-0584
• Publisher: Wiley Blackwell (John Wiley & Sons)
• Country of Publication: United Kingdom
• Language: English