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Forest water use is increasingly decoupled from water availability even during severe drought



Key to understanding forest water balances is the role of tree species regulating evapotranspiration (ET), but the synergistic impact of forest species composition, topography, and water availability on ET and how this shapes drought sensitivity across the landscape remains unclear.


Our aims were to quantify (1) the effect of forest composition and topography including elevation and hillslope gradients on the relationship between ET and water availability, and (2) whether the relationship has changed over time.


We used remotely sensed Landsat and MODIS ET to quantify forest ET across the Blue Ridge ecoregion of the southeastern USA. Then quantified metrics describing ET responses to water availability and trends in responses over time and assessed how these metrics varied across elevation, hillslope, and forest composition gradients.


We demonstrated forest ET is becoming less constrained by water availability at the expense of lateral flow. Drought impacts on ET diverged along elevation and hillslope gradients, and that divergence was more pronounced with increasingly severe drought, indicating high elevation and drier, upslope regions tend to maintain ET rates even during extreme drought. We identified a decoupling of ET from water availability over time, and found this process was accelerated at higher elevations and in areas with more diffuse-porous trees.


Given the large proportion of forests on the landscape distributed across high elevation and upslope positions, reductions in downslope water availability could be widespread, amplifying vulnerability of runoff, the health of downslope vegetation, and aquatic biodiversity.

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Data availability

All data used in this study was publicly available online. Eddy covariance data was downloaded from Ameriflux ( GRIDMET SPI data, land cover data, and USGS NED data was downloaded from Google Earth Engine ( MODIS ET data was downloaded from USGS ( Landsat ET data was downloaded from USGS ( The Riley et al. (2021) forest composition map was downloaded from the USDA Forest Service ( The Wilson et al. (2013) forest composition maps were downloaded from the USDA forest service (

Code availability

R scripts used for analysis and visualization are available on request.


  • Abatzoglou JT (2013) Development of gridded surface meteorological data for ecological applications and modelling. Int J Climatol 33(1):121–131

    Article  Google Scholar 

  • Bales RC, Goulden ML, Hunsaker CT, Conklin MH, Hartsough PC, O’Geen AT, Safeeq M (2018) Mechanisms controlling the impact of multi-year drought on mountain hydrology. Sci Rep.

    Article  PubMed  PubMed Central  Google Scholar 

  • Beven KJ, Kirkby MJ (1979) A physically based, variable contributing area model of basin hydrology/un modèle à base physique de zone d’appel variable de l’hydrologie du bassin versant. Null 24(1):43–69

    Google Scholar 

  • Caldwell PV, Miniat CF, Elliott KJ, Swank WT, Brantley ST, Laseter SH (2016) Declining water yield from forested mountain watersheds in response to climate change and forest mesophication. Glob Change Biol 22(9):2997–3012

    Article  Google Scholar 

  • Christopher Oishi A (2020), AmeriFlux BASE US-Cwt Coweeta, Ver. 1–5, AmeriFlux AMP

  • Elliott KJ, Swank WT (2008) Long-term changes in forest composition and diversity following early logging (1919–1923) and the decline of American chestnut (Castanea dentata). Plant Ecol 197(2):155–172

    Article  Google Scholar 

  • Elliott KJ, Miniat CF, Pederson N, Laseter SH (2015) Forest tree growth response to hydroclimate variability in the southern Appalachians. Glob Change Biol 21(12):4627–4641

    Article  Google Scholar 

  • Falkenmark M, Rockström J (2006) The new blue and green water paradigm: breaking new ground for water resources planning and management. J Water Resour Plan Manag 132(3):129–132

    Article  Google Scholar 

  • Fan Y, Clark M, Lawrence DM, Swenson S, Band LE, Brantley SL, Yamazaki D (2019) Hillslope hydrology in global change research and earth system modeling. Water Resour Res 55(2):1737–1772

    Article  Google Scholar 

  • Fisher JB, Melton F, Middleton E, Hain C, Anderson M, Allen R, Wood EF (2017) The future of evapotranspiration: Global requirements for ecosystem functioning, carbon and climate feedbacks, agricultural management, and water resources. Water Resour Res 53(4):2618–2626

    Article  Google Scholar 

  • Fisher JB, Lee B, Purdy AJ, Halverson GH, Dohlen MB, Cawse-Nicholson K, Hook S (2020) ECOSTRESS: NASA’s next generation mission to measure evapotranspiration from the international space station. Water Resour Res 56(4):e2019WR026058

    Article  Google Scholar 

  • Ford CR, Hubbard RM, Vose JM (2011) Quantifying structural and physiological controls on variation in canopy transpiration among planted pine and hardwood species in the southern appalachians. Ecohydrology 4(2):183–195

    Article  Google Scholar 

  • Friedl M, Sulla-Menashe D (2019). MCD12Q1 MODIS/Terra+Aqua land cover type yearly L3 Global 500m SIN Grid V006 . NASA EOSDIS Land Processes DAAC. Accessed 27 Oct 2021

  • Gesch DB, Evans GA, Oimoen MJ, and Arundel S (2018). The national elevation dataset. (pp. 83–110) American Society for Photogrammetry and Remote Sensing. Accessed 1 Aug 2021

  • Goulden ML, Bales RC (2014) Mountain runoff vulnerability to increased evapotranspiration with vegetation expansion. Proc Natl Acad Sci 111(39):14071–14075

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  • Goulden ML, Bales RC (2019) California forest die-off linked to multi-year deep soil drying in 2012–2015 drought. Nat Geosci 12(8):632–637

    CAS  Article  Google Scholar 

  • Guttman NB (1999) Accepting the standardized precipitation index: a calculation algorithm1. JAWRA J Am Water Resour Assoc 35(2):311–322

    Article  Google Scholar 

  • Hawthorne S, Miniat CF (2018) Topography may mitigate drought effects on vegetation along a hillslope gradient. Ecohydrology 11(1):e1825

    Article  Google Scholar 

  • Hoylman ZH, Jencso KG, Hu J, Martin JT, Holden ZA, Seielstad CA, Rowell EM (2018) Hillslope topography mediates spatial patterns of ecosystem sensitivity to climate. J Geophys Res Biogeosci 123(2):353–371

    Article  Google Scholar 

  • Hwang T, Band LE, Vose JM, Tague C (2012) Ecosystem processes at the watershed scale: hydrologic vegetation gradient as an indicator for lateral hydrologic connectivity of headwater catchments. Water Resour Res.

    Article  Google Scholar 

  • Hwang T, Band LE, Miniat CF, Song C, Bolstad PV, Vose JM, Love JP (2014) Divergent phenological response to hydroclimate variability in forested mountain watersheds. Glob Change Biol 20(8):2580–2595

    Article  Google Scholar 

  • Hwang T, Martin KL, Vose JM, Wear D, Miles B, Kim Y, Band LE (2018) Nonstationary hydrologic behavior in forested watersheds is mediated by climate-induced changes in growing season length and subsequent vegetation growth. Water Resour Res 54(8):5359–5375.

    Article  Google Scholar 

  • Hwang T, Band LE, Miniat CF, Vose JM, Knoepp JD, Song C, Bolstad PV (2020) Climate change may increase the drought stress of mesophytic trees downslope with ongoing forest mesophication under a history of fire suppression. Front For Glob Change.

    Article  Google Scholar 

  • Jiao W, Wang L, Smith WK, Chang Q, Wang H, D’Odorico P (2021) Observed increasing water constraint on vegetation growth over the last three decades. Nat Commun 12(1):1–9

    Article  CAS  Google Scholar 

  • Keenan TF, Hollinger DY, Bohrer G, Dragoni D, Munger JW, Schmid HP, Richardson AD (2013) Increase in forest water-use efficiency as atmospheric carbon dioxide concentrations rise. Nature 499(7458):324–327

    CAS  PubMed  Article  Google Scholar 

  • Kelly AE, Goulden ML (2008) Rapid shifts in plant distribution with recent climate change. Proc Natl Acad Sci USA 105(33):11823

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  • Lin L, Band LE, Vose JM, Hwang T, Miniat CF, Bolstad PV (2019) Ecosystem processes at the watershed scale: influence of flowpath patterns of canopy ecophysiology on emergent catchment water and carbon cycling. Ecohydrology 12(5):e2093

    Article  Google Scholar 

  • Mastrotheodoros T, Pappas C, Molnar P, Burlando P, Manoli G, Parajka J, Fatichi S (2020) More green and less blue water in the alps during warmer summers. Nat Clim Chang 10(2):155–161

    Article  Google Scholar 

  • Meinzer FC, Woodruff DR, Eissenstat DM, Lin HS, Adams TS, McCulloh KA (2013) Above- and belowground controls on water use by trees of different wood types in an eastern US deciduous forest. Tree Physiol 33(4):345–356

    PubMed  Article  Google Scholar 

  • Monteith JL (1965) Evaporation and environment. Symp Soc Exp Biol 19:205–234

    CAS  PubMed  Google Scholar 

  • Mu Q, Heinsch FA, Zhao M, Running SW (2007) Development of a global evapotranspiration algorithm based on MODIS and global meteorology data. Remote Sens Environ 111(4):519–536

    Article  Google Scholar 

  • Nicolai-Shaw N, Zscheischler J, Hirschi M, Gudmundsson L, Seneviratne SI (2017) A drought event composite analysis using satellite remote-sensing based soil moisture. Remote Sens Environ 203:216–225

    Article  Google Scholar 

  • Novick K, Brantley S, Miniat CF, Walker J, Vose JM (2014) Inferring the contribution of advection to total ecosystem scalar fluxes over a tall forest in complex terrain. Agric for Meteorol 185:1–13

    Article  Google Scholar 

  • Novick KA, Ficklin DL, Stoy PC, Williams CA, Bohrer G et al. (2016). The increasing importance of atmospheric demand for ecosystem water and carbon fluxes—ProQuest. Nature Climate Change1 6(11). Accessed 1 Aug 2021

  • Nowacki GJ, Abrams MD (2008) The demise of fire and “Mesophication” of forests in the eastern United States. Bioscience 58(2):123–138

    Article  Google Scholar 

  • Oishi AC, Miniat CF, Novick KA, Brantley ST, Vose JM, Walker JT (2018) Warmer temperatures reduce net carbon uptake, but do not affect water use, in a mature southern Appalachian forest. Agric For Meteorol 252:269–282

    Article  Google Scholar 

  • Orth R, Destouni G (2018) Drought reduces blue-water fluxes more strongly than green-water fluxes in Europe. Nat Commun 9(1):1–8

    CAS  Article  Google Scholar 

  • Pascolini-Campbell M, Reager JT, Chandanpurkar HA, Rodell M (2021) A 10 per cent increase in global land evapotranspiration from 2003 to 2019. Nature 593(7860):543–547

    CAS  PubMed  Article  Google Scholar 

  • Pederson N, D’Amato AW, Dyer JM, Foster DR, Goldblum D, Hart JL, Williams JW (2015) Climate remains an important driver of post-European vegetation change in the eastern United States. Glob Change Biol 21(6):2105–2110

    Article  Google Scholar 

  • Pittillo, J. D., Hatcher, R. D., & Buol, S. W. (1998). Introduction to the environment and vegetation of the southern blue ridge province. Castanea 63(3): 202–216. Accessed 1 Aug 2021

  • Rangwala I, Miller JR (2012) Climate change in mountains: a review of elevation-dependent warming and its possible causes. Clim Change 114(3):527–547

    Article  Google Scholar 

  • Riley KL, Grenfell IC, Finney MA, Wiener JM (2021) TreeMap, a tree-level model of conterminous US forests circa 2014 produced by imputation of FIA plot data. Sci Data 8(1):1–14

    CAS  Article  Google Scholar 

  • Running, S., Mu, Q., Zhao, M., Moreno, A. (2019). MOD16A2GF MODIS/Terra net evapotranspiration gap-filled 8-day L4 global 500 m SIN Grid V006 . NASA EOSDIS Land Processes DAAC. Accessed 7 Aug 2021

  • Sayler, K., Zanter, K. (2020). Landsat provisional actual evapotranspiration (ETa) product guide. U.S. Geological Survey. Accessed 1 Aug 2021

  • Senay GB (2018) Satellite psychrometric formulation of the operational simplified surface energy balance (SSEBop) model for quantifying and mapping evapotranspiration. Appl Eng Agric 34:555–2018

    Article  Google Scholar 

  • Senay GB, Budde M, Verdin JP, Melesse AM (2007) A coupled remote sensing and simplified surface energy balance approach to estimate actual evapotranspiration from irrigated fields. Sensors.

    Article  PubMed  PubMed Central  Google Scholar 

  • Senay GB, Budde ME, Verdin JP (2011) Enhancing the simplified surface energy balance (SSEB) approach for estimating landscape ET: validation with the METRIC model. Agric Water Manag 98(4):606–618

    Article  Google Scholar 

  • Senay GB, Bohms S, Singh RK, Gowda PH, Velpuri NM, Alemu H, Verdin JP (2013) Operational evapotranspiration mapping using remote sensing and weather datasets: a new parameterization for the SSEB approach. JAWRA J Am Water Resour Assoc 49(3):577–591

    Article  Google Scholar 

  • Senay GB, Schauer M, Friedrichs M, Velpuri NM, Singh RK (2017) Satellite-based water use dynamics using historical landsat data (1984–2014) in the southwestern United States. Remote Sens Environ 202:98–112

    Article  Google Scholar 

  • Tai X, Anderegg WRL, Blanken PD, Burns SP, Christensen L, Brooks PD (2020) Hillslope hydrology influences the spatial and temporal patterns of remotely sensed ecosystem productivity. Water Resour Res 56(11):e2020WR027630

    Article  Google Scholar 

  • Tai X, Venturas MD, Mackay DS, Brooks PD, Flanagan LB (2021) Lateral subsurface flow modulates forest mortality risk to future climate and elevated CO2. Environ Res Lett 16(8):084015

    CAS  Article  Google Scholar 

  • Teuling AJ, Loon AFV, Seneviratne SI, Lehner I, Aubinet M, Heinesch B et al (2013) Evapotranspiration amplifies European summer drought. Geophys Res Lett 40(10):2071–2075

    Article  Google Scholar 

  • Tromp-van Meerveld HJ, McDonnell JJ (2006) On the interrelations between topography, soil depth, soil moisture, transpiration rates and species distribution at the hillslope scale. Adv Water Resour 29(2):293–310

    Article  Google Scholar 

  • Wang H, Rogers JC, Munroe DK (2015) Commonly used drought indices as indicators of soil moisture in China. J Hydrometeorol 16(3):1397–1408

    Article  Google Scholar 

  • Wilson BT, Lister AJ, Riemann RI, Griffith DM (2013) Live tree species basal area of the contiguous United States (2000–2009). USDA Forest Service, Rocky Mountain Research Station, Newtown Square.

    Book  Google Scholar 

  • Yang Y, Anderson MC, Gao F, Hain CR, and Semmens KA (2015). Daily landsat-scale evapotranspiration estimation over a forested landscape in North Carolina, USA, using multi-satellite data fusion. Hydrology and Earth System Sciences 21(2): 1017–1037.

  • Yang L, Jin S, Danielson P, Homer C, Gass L, Bender SM, Xian G (2018) A new generation of the united states national land cover database: requirements, research priorities, design, and implementation strategies. ISPRS J Photogramm Remote Sens 146:108–123

    Article  Google Scholar 

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This research was funded by the Center for Geospatial Analytics at NC State University, a Nature Conservancy NatureNet fellowship, and a U.S. Geological Survey Southeast Climate Adaptation Science Center graduate fellowship awarded to Katie McQuillan.


This research was funded by the Center for Geospatial Analytics at NC State University, a Nature Conservancy NatureNet fellowship, and a U.S. Geological Survey Southeast Climate Adaptation Science Center graduate fellowship awarded to Katie McQuillan.

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KAM: Conceptualization, methodology, formal analysis, writing—original draft. MGT: Methodology, revisions. KLM: Conceptualization, methodology, writing and revisions.

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Correspondence to Katie A. McQuillan.

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McQuillan, K.A., Tulbure, M.G. & Martin, K.L. Forest water use is increasingly decoupled from water availability even during severe drought. Landsc Ecol 37, 1801–1817 (2022).

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  • Evapotranspiration
  • Remote sensing
  • Topography
  • Forest composition
  • Landsat