, Volume 21, Issue 4, pp 723–739 | Cite as

Overstorey–Understorey Interactions Intensify After Drought-Induced Forest Die-Off: Long-Term Effects for Forest Structure and Composition

  • Timothy ThrippletonEmail author
  • Harald Bugmann
  • Marc Folini
  • Rebecca S. Snell


Severe drought events increasingly affect forests worldwide, but little is known about their long-term effects at the ecosystem level. Competition between trees and herbs (‘overstorey–understorey competition’) for soil water can reduce tree growth and regeneration success and may thereby alter forest structure and composition. However, these effects are typically ignored in modelling studies. To test the long-term impact of water competition by the herbaceous understorey on forest dynamics, we incorporated this process in the dynamic forest landscape model LandClim. Simulations were performed both with and without understorey under current and future climate scenarios (RCP4.5 and RCP8.5) in a drought-prone inner-Alpine valley in Switzerland. Under current climate, herbaceous understorey reduced tree regeneration biomass by up to 51%, particularly in drought-prone landscape positions (i.e., south-facing, low-elevation slopes), where it also caused a shift in forest composition towards drought-tolerant tree species (for example, Quercus pubescens). For adult trees, the understorey had a minor effect on growth. Under future climate change scenarios, increasing drought frequency and intensity resulted in large-scale mortality of canopy trees, which intensified the competitive interaction between the understorey and tree regeneration. At the driest landscape positions, a complete exclusion of tree regeneration and a shift towards an open, savannah-like vegetation occurred. Overall, our results demonstrate that water competition by the herbaceous understorey can cause long-lasting legacy effects on forest structure and composition across drought-prone landscapes, by affecting the vulnerable recruitment phase. Ignoring herbaceous vegetation may thus lead to a strong underestimation of future drought impacts on forests.


dynamic vegetation model understorey layer soil water competition vegetation shift Valais Central Alps 



We are grateful for the support by Dominic Michel in all IT-related questions. Denis Loustau kindly provided biological data from the study site Le Bray. We furthermore thank Maxime Cailleret, Sebastian Wolf, Arnaud Giuggiola, Nica Huber and Laura Schuler for their helpful input. Funding for Rebecca S. Snell was provided by the EU FP7 Project ‘IMPRESSIONS’, Grant No. 603416.

Supplementary material

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Supplementary material 1 (DOCX 84 kb)
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  1. Adams HR, Barnard HR, Loomis AK. 2014. Topography alters tree growth-climate relationships in a semi-arid forested catchment. Ecosphere 5:1–16.CrossRefGoogle Scholar
  2. Allen CD, Macalady AK, Chenchouni H, Bachelet D, McDowell N, Vennetier M, Kitzberger T, Rigling A, Breshears DD, Hogg EH, Gonzalez P, Fensham R, Zhang Z, Castro J, Demidova N, Lim JH, Allard G, Running SW, Semerci A, Cobb N. 2010. A global overview of drought and heat-induced tree mortality reveals emerging climate change risks for forests. For Ecol Manage 259:660–84.CrossRefGoogle Scholar
  3. Anderegg WRL, Anderegg LDL, Sherman C, Karp DS. 2012. Effects of widespread drought-induced aspen mortality on understory plants. Conserv Biol 26:1082–90.CrossRefPubMedGoogle Scholar
  4. Anderegg WRL, Kane JM, Anderegg LDL. 2013. Consequences of widespread tree mortality triggered by drought and temperature stress. Nat Clim Change 3:30–6.CrossRefGoogle Scholar
  5. Anderegg WRL, Schwalm C, Biondi F, Camarero JJ, Koch G, Litvak M, Ogle K, Shaw JD, Shevliakova E, Williams AP, Wolf A, Ziaco E, Pacala S. 2015. Pervasive drought legacies in forest ecosystems and their implications for carbon cycle models. Science 349:528–32.CrossRefPubMedGoogle Scholar
  6. Balandier P, Collet C, Miller JH, Reynolds PE, Zedaker SM. 2006. Designing forest vegetation management strategies based on the mechanisms and dynamics of crop tree competition by neighbouring vegetation. Forestry 79:3–27.CrossRefGoogle Scholar
  7. Baldocchi DD, Law BE, Anthoni PM. 2000. On measuring and modeling energy fluxes above the floor of a homogeneous and heterogeneous conifer forest. Agric For Meteorol 102:187–206.CrossRefGoogle Scholar
  8. Baldocchi DD, Xu LK, Kiang N. 2004. How plant functional-type, weather, seasonal drought, and soil physical properties alter water and energy fluxes of an oak-grass savanna and an annual grassland. Agric For Meteorol 123:13–39.CrossRefGoogle Scholar
  9. Bigler C, Braker OU, Bugmann H, Dobbertin M, Rigling A. 2006. Drought as an inciting mortality factor in Scots pine stands of the Valais, Switzerland. Ecosystems 9:330–43.CrossRefGoogle Scholar
  10. Black TA, Kelliher FM. 1989. Processes controlling understorey evapotranspiration. Philos Trans R Soc Lond Ser B Biol Sci 324:207–31.CrossRefGoogle Scholar
  11. Bugmann H. 2001. A review of forest gap models. Clim Change 51:259–305.CrossRefGoogle Scholar
  12. Bugmann H, Cramer W. 1998. Improving the behaviour of forest gap models along drought gradients. For Ecol Manage 103:247–63.CrossRefGoogle Scholar
  13. Cáceres MD, Martínez-Vilalta J, Coll L, Llorens P, Casals P, Poyatos R, Pausas JG, Brotons L. 2015. Coupling a water balance model with forest inventory data to predict drought stress: the role of forest structural changes vs. climate changes. Agric For Meteorol 213:77–90.CrossRefGoogle Scholar
  14. Clark JS, Iverson L, Woodall CW, Allen CD, Bell DM, Bragg DC, D’Amato AW, Davis FW, Hersh MH, Ibanez I, Jackson ST, Matthews S, Pederson N, Peters M, Schwartz MW, Waring KM, Zimmermann NE. 2016. The impacts of increasing drought on forest dynamics, structure, and biodiversity in the United States. Glob Change Biol 22:2329–52.CrossRefGoogle Scholar
  15. Constantin J, Grelle A, Ibrom A, Morgenstern K. 1999. Flux partitioning between understorey and overstorey in a boreal spruce/pine forest determined by the eddy covariance method. Agric For Meteorol 98–9:629–43.CrossRefGoogle Scholar
  16. Dai AG. 2013. Increasing drought under global warming in observations and models. Nat Clim Change 3:52–8.CrossRefGoogle Scholar
  17. Davis MA, Wrage KJ, Reich PB. 1998. Competition between tree seedlings and herbaceous vegetation: support for a theory of resource supply and demand. J Ecol 86:652–61.CrossRefGoogle Scholar
  18. Elkin C, Giuggiola A, Rigling A, Bugmann H. 2015. Short- and long-term efficacy of forest thinning to mitigate drought impacts in mountain forests in the European Alps. Ecol Appl 25:1083–98.CrossRefPubMedGoogle Scholar
  19. Elkin C, Gutierrez AG, Leuzinger S, Manusch C, Temperli C, Rasche L, Bugmann H. 2013. A 2 degrees C warmer world is not safe for ecosystem services in the European Alps. Glob Change Biol 19:1827–40.CrossRefGoogle Scholar
  20. Federer CA. 1982. Transpirational supply and demand: plant, soil, and atmospheric effects evaluated by simulation. Water Resour Res 18:355–62.CrossRefGoogle Scholar
  21. Galiano L, Martinez-Vilalta J, Eugenio M, Granzow-de la Cerda I, Lloret F. 2013. Seedling emergence and growth of Quercus spp. following severe drought effects on a Pinus sylvestris canopy. J Veg Sci 24:580–8.CrossRefGoogle Scholar
  22. George LO, Bazzaz FA. 1999. The fern understory as an ecological filter: emergence and establishment of canopy-tree seedlings. Ecology 80:833–45.CrossRefGoogle Scholar
  23. Gerten D, Schaphoff S, Haberlandt U, Lucht W, Sitch S. 2004. Terrestrial vegetation and water balance—hydrological evaluation of a dynamic global vegetation model. J Hydrol 286:249–70.CrossRefGoogle Scholar
  24. Gilliam FS. 2007. The ecological significance of the herbaceous layer in temperate forest ecosystems. Bioscience 57:845–58.CrossRefGoogle Scholar
  25. Giuggiola A. 2016. Impact of forest management on the drought resistance of dry pine forests. Ph.D. Thesis No. 22802. ETH-Zurich. Zurich, p 214.Google Scholar
  26. Giuggiola A, Bugmann H, Zingg A, Dobbertin M, Rigling A. 2013. Reduction of stand density increases drought resistance in xeric Scots pine forests. For Ecol Manage 310:827–35.CrossRefGoogle Scholar
  27. Gobin R, Korboulewsky N, Dumas Y, Balandier P. 2015. Transpiration of four common understorey plant species according to drought intensity in temperate forests. Ann For Sci 72:1053–64.CrossRefGoogle Scholar
  28. Halpern CB, Lutz JA. 2013. Canopy closure exerts weak controls on understory dynamics: a 30-year study of overstory-understory interactions. Ecol Monogr 83:221–37.CrossRefGoogle Scholar
  29. Hanewinkel M, Cullmann DA, Schelhaas MJ, Nabuurs GJ, Zimmermann NE. 2013. Climate change may cause severe loss in the economic value of European forest land. Nat Clim Change 3:203–7.CrossRefGoogle Scholar
  30. Henne PD, Elkin C, Franke J, Colombaroli D, Calò C, La Mantia T, Pasta S, Conedera M, Dermody O, Tinner W. 2015. Reviving extinct Mediterranean forest communities may improve ecosystem potential in a warmer future. Front Ecol Environ 13:356–62.CrossRefGoogle Scholar
  31. Henne PD, Elkin CM, Reineking B, Bugmann H. 2011. Did soil development limit spruce (Picea abies) expansion in the Central Alps during the Holocene? Testing a palaeobotanical hypothesis with a dynamic landscape model. J Biogeogr 38:933–49.CrossRefGoogle Scholar
  32. Iida S, Ohta T, Matsumoto K, Nakai T, Kuwada T, Kononov AV, Maximov TC, van der Molen MK, Dolman H, Tanaka H, Yabuki H. 2009. Evapotranspiration from understory vegetation in an eastern Siberian boreal larch forest. Agric For Meteorol 149:1129–39.CrossRefGoogle Scholar
  33. Jackson RB, Canadell J, Ehleringer JR, Mooney HA, Sala OE, Schulze ED. 1996. A global analysis of root distributions for terrestrial biomes. Oecologia 108:389–411.CrossRefPubMedGoogle Scholar
  34. Jarosz N, Brunet Y, Lamaud E, Irvine M, Bonnefond JM, Loustau D. 2008. Carbon dioxide and energy flux partitioning between the understorey and the overstorey of a maritime pine forest during a year with reduced soil water availability. Agric For Meteorol 148:1508–23.CrossRefGoogle Scholar
  35. Joffre R, Rambal S. 1993. How tree cover influences the water-balance of Mediterranean rangelands. Ecology 74:570–82.CrossRefGoogle Scholar
  36. Johnstone JF, McIntire EJB, Pedersen EJ, King G, Pisaric MJF. 2010. A sensitive slope: estimating landscape patterns of forest resilience in a changing climate. Ecosphere 1:1–21.CrossRefGoogle Scholar
  37. Knoop W, Walker B. 1985. Interactions of woody and herbaceous vegetation in a southern African savanna. J Ecol 73:235–53.CrossRefGoogle Scholar
  38. McCarthy BC. 2003. The herbaceous layer of eastern old-growth deciduous forests. In: Gilliam FS, Roberts MR, Eds. The herbaceous layer in forests of eastern North America. New York: Oxford University Press. p 163–76.Google Scholar
  39. McCarthy BC, Small CJ, Rubino DL. 2001. Composition, structure and dynamics of Dysart Woods, an old-growth mixed mesophytic forest of southeastern Ohio. For Ecol Manage 140:193–213.CrossRefGoogle Scholar
  40. Moreno G, Obrador JJ, Cubera E, Dupraz C. 2005. Fine root distribution in dehesas of central-western Spain. Plant Soil 277:153–62.CrossRefGoogle Scholar
  41. Morris LA, Moss SA, Garbett WS. 1993. Competitive interference between selected herbaceous and woody plants and Pinus taeda L. during two growing seasons following planting. For Sci 39:166–87.Google Scholar
  42. Moser B, Temperli C, Schneiter G, Wohlgemuth T. 2010. Potential shift in tree species composition after interaction of fire and drought in the Central Alps. Eur J Forest Res 129:625–33.CrossRefGoogle Scholar
  43. Nambiar EKS, Sands R. 1993. Competition for water and nutrients in forests. Can J For Res 23:1955–68.CrossRefGoogle Scholar
  44. Nelson AS, Weiskittel AR, Wagner RG, Saunders MR. 2014. Development and evaluation of aboveground small tree biomass models for naturally regenerated and planted species in eastern Maine, U.S.A. Biomass Bioenerg 68:215–27.CrossRefGoogle Scholar
  45. Niinemets U. 2010. A review of light interception in plant stands from leaf to canopy in different plant functional types and in species with varying shade tolerance. Ecol Res 25:693–714.CrossRefGoogle Scholar
  46. Patsias K, Bruelheide H. 2013. Climate change—bad news for montane forest herb layer species? Acta Oecol 50:10–19.CrossRefGoogle Scholar
  47. Picon-Cochard C, Coll L, Balandier P. 2006. The role of below-ground competition during early stages of secondary succession: the case of 3-year-old Scots pine (Pinus sylvestris L.) seedlings in an abandoned grassland. Oecologia 148:373–83.CrossRefPubMedGoogle Scholar
  48. Provendier D, Balandier P. 2008. Compared effects of competition by grasses (Graminoids) and broom (Cytisus scoparius) on growth and functional traits of beech saplings (Fagus sylvatica). Ann For Sci 65:510.CrossRefGoogle Scholar
  49. R Development Core Team. 2016. R: a language and environment for statistical computing. Vienna: R Foundation for Statistical Computing.Google Scholar
  50. Rajczak J, Kotlarski S, Salzmann N, Schar C. 2016. Robust climate scenarios for sites with sparse observations: a two-step bias correction approach. Int J Climatol 36:1226–43.CrossRefGoogle Scholar
  51. Richardson B. 1993. Vegetation management-practices in plantation forests of Australia and New-Zealand. Can J For Res 23:1989–2005.CrossRefGoogle Scholar
  52. Rigling A, Bigler C, Eilmann B, Feldmeyer-Christe E, Gimmi U, Ginzler C, Graf U, Mayer P, Vacchiano G, Weber P, Wohlgemuth T, Zweifel R, Dobbertin M. 2013. Driving factors of a vegetation shift from Scots pine to pubescent oak in dry Alpine forests. Glob Change Biol 19:229–40.CrossRefGoogle Scholar
  53. Rigling A, Braker O, Schneiter G, Schweingruber F. 2002. Intra-annual tree-ring parameters indicating differences in drought stress of Pinus sylvestris forests within the Erico-Pinion in the Valais (Switzerland). Plant Ecol 163:105–21.CrossRefGoogle Scholar
  54. Roberts J, Pymar CF, Wallace JS, Pitman RM. 1980. Seasonal changes in leaf area, stomatal and canopy conductances and transpiration from bracken below a forest canopy. J Appl Ecol 17:409–22.CrossRefGoogle Scholar
  55. Royo AA, Carson WP. 2006. On the formation of dense understory layers in forests worldwide: consequences and implications for forest dynamics, biodiversity, and succession. Can J For Res 36:1345–62.CrossRefGoogle Scholar
  56. Saura-Mas S, Bonas A, Lloret F. 2015. Plant community response to drought-induced canopy defoliation in a Mediterranean Quercus ilex forest. Eur J Forest Res 134:261–72.CrossRefGoogle Scholar
  57. Schaap MG, Bouten W. 1997. Forest floor evaporation in a dense Douglas fir stand. J Hydrol 193:97–113.CrossRefGoogle Scholar
  58. Schuler LJ, Bugmann H, Snell RS. 2016. From monocultures to mixed-species forests: is tree diversity key for providing ecosystem services at the landscape scale? Landscape Ecol 32:1499–516.CrossRefGoogle Scholar
  59. Schulze ED, Beck E, Müller-Hohenstein K. 2005. Plant ecology. Berlin: Springer. p 702p.Google Scholar
  60. Schumacher S. 2004. The role of large-scale disturbances and climate for the dynamics of forested landscapes in the European Alps. Ph.D. Thesis No. 15573. ETH Zurich, p 141.Google Scholar
  61. Schumacher S, Bugmann H. 2006. The relative importance of climatic effects, wildfires and management for future forest landscape dynamics in the Swiss Alps. Glob Change Biol 12:1435–50.CrossRefGoogle Scholar
  62. Schumacher S, Bugmann H, Mladenoff D. 2004. Improving the formulation of tree growth and succession in a spatially explicit landscape model. Ecol Model 180:175–94.CrossRefGoogle Scholar
  63. Schwörer C, Fisher DM, Gavin DG, Temperli C, Bartlein PJ. 2016. Modeling postglacial vegetation dynamics of temperate forests on the Olympic Peninsula (WA, USA) with special regard to snowpack. Clim Change 137:379–94.CrossRefGoogle Scholar
  64. Suarez ML, Kitzberger T. 2008. Recruitment patterns following a severe drought: long-term compositional shifts in Patagonian forests. Can J For Res 38:3002–10.CrossRefGoogle Scholar
  65. Thrippleton T, Bugmann H, Kramer-Priewasser K, Snell RS. 2016. Herbaceous understorey: an overlooked player in forest landscape dynamics? Ecosystems 19:1240–54.CrossRefGoogle Scholar
  66. Thrippleton T, Dolos K, Perry GLW, Groeneveld J, Reineking B. 2014. Simulating long-term vegetation dynamics using a forest landscape model: the post-Taupo succession on Mt Hauhungatahi, North Island, New Zealand. N Z J Ecol 38:26–43.Google Scholar
  67. Wagner RG, Little KM, Richardson B, McNabb K. 2006. The role of vegetation management for enhancing productivity of the world’s forests. Forestry 79:57–79.CrossRefGoogle Scholar
  68. Ward D, Wiegand K, Getzin S. 2013. Walter’s two-layer hypothesis revisited: back to the roots!. Oecologia 172:617–30.CrossRefPubMedGoogle Scholar
  69. Wolf A. 2011. Estimating the potential impact of vegetation on the water cycle requires accurate soil water parameter estimation. Ecol Model 222:2595–605.CrossRefGoogle Scholar
  70. Zou CB, Barron-Gafford GA, Breshears DD. 2007. Effects of topography and woody plant canopy cover on near-ground solar radiation: Relevant energy inputs for ecohydrology and hydropedology. Geophys Res Lett 34:1–6.CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media, LLC 2017

Authors and Affiliations

  • Timothy Thrippleton
    • 1
    Email author
  • Harald Bugmann
    • 1
  • Marc Folini
    • 1
  • Rebecca S. Snell
    • 1
    • 2
  1. 1.Department of Environmental Systems Science, Forest EcologySwiss Federal Institute of Technology, ETH ZurichZurichSwitzerland
  2. 2.Department of Environmental and Plant BiologyOhio UniversityAthensUSA

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