Feedbacks between vegetation pattern and resource loss dramatically decrease ecosystem resilience and restoration potential in a simple dryland model
- 1.2k Downloads
Conceptual frameworks of dryland degradation commonly include ecohydrological feedbacks between landscape spatial organization and resource loss, so that decreasing cover and size of vegetation patches result in higher water and soil losses, which lead to further vegetation loss. However, the impacts of these feedbacks on dryland dynamics in response to external stress have barely been tested. Using a spatially-explicit model, we represented feedbacks between vegetation pattern and landscape resource loss by establishing a negative dependence of plant establishment on the connectivity of runoff-source areas (e.g., bare soils). We assessed the impact of various feedback strengths on the response of dryland ecosystems to changing external conditions. In general, for a given external pressure, these connectivity-mediated feedbacks decrease vegetation cover at equilibrium, which indicates a decrease in ecosystem resistance. Along a gradient of gradual increase of environmental pressure (e.g., aridity), the connectivity-mediated feedbacks decrease the amount of pressure required to cause a critical shift to a degraded state (ecosystem resilience). If environmental conditions improve, these feedbacks increase the pressure release needed to achieve the ecosystem recovery (restoration potential). The impact of these feedbacks on dryland response to external stress is markedly non-linear, which relies on the non-linear negative relationship between bare-soil connectivity and vegetation cover. Modelling studies on dryland vegetation dynamics not accounting for the connectivity-mediated feedbacks studied here may overestimate the resistance, resilience and restoration potential of drylands in response to environmental and human pressures. Our results also suggest that changes in vegetation pattern and associated hydrological connectivity may be more informative early-warning indicators of dryland degradation than changes in vegetation cover.
KeywordsResource-leakiness feedbacks Vegetation spatial pattern Hydrological connectivity Desertification Resilience Restoration potential Dryland ecosystems
This work was supported by the research projects PATTERN (AGCL2008/-05532-C02-01/FOR) and FEEDBACK (CGL2011-30515-C02-01) funded by the Spanish Ministry of Innovation and Science, the EC-funded projects PRACTICE (GA226818) and CASCADE (GA283068), and the project RESINEE funded by the ERA-Net on Complexity. AGM was supported by a postdoctoral contract (APOSTD/2011/005) from the Valencia Regional Government (Generalitat Valenciana), Spain.
- Brandt CJ, Thornes JB (1996) Mediterranean desertification and land use. Wiley, ChichesterGoogle Scholar
- Breshears DD, Cobb NS, Rich PM, Price KP, Allen CD, Balice RG, Romme WH, Kastens JH, Floyd ML, Belnap J, Anderson JJ, Myers OB, Meyer CW (2005) Regional vegetation die- off in response to global-change- type drought. Proc Natl Acad Sci 102(42):15144–15148Google Scholar
- Foley JA, Coe MT, Scheffer M, Wang G (2003) Regime shifts in the Sahara and Sahel: interactions between ecological and climatic systems in Northern AfricaGoogle Scholar
- Francis CF, Thornes JB (1990) Runoff hydrographs from three Mediterranean vegetations cover types. In: Thornes JB (ed) Vegetation and erosion, processes and environments. Wiley, Chichester, pp 363–384Google Scholar
- Ludwig JA, Tongway D, Freudenberger D, Noble J, Hodgkinson K (eds) (1997) Landscape ecology function and management: principles from Australia’s rangelands. Melbourne (Australia), CSIROGoogle Scholar
- Moreno-de las Heras M, Saco PM, Willgoose GR, Tongway DJ (2011). Assessing landscape structure and pattern fragmentation in semiarid ecosystems using patch-size distributions. Ecol Appl 21(7):2793–2805Google Scholar
- Ravi S, Breshears DD, Huxman TE, D’Odorico P (2010) Land degradation in drylands: Interactions among hydrologic–aeolian erosion and vegetation dynamics 116(3–4):236–245Google Scholar
- Moreno-de las Heras M, Saco PM, Willgoose GR, Tongway DJ (2012). Variations in hydrological connectivity of Australian semiarid landscapes indicate abrupt changes in rainfall-use efficiency of vegetation. J Geophys Res Biogeosci 117. doi: 10.1029/2011JG001839
- Schröter D, Cramer W, Leemans R, Prentice IC, Araújo MB, Arnell NW, Bondeau A, Bugmann H, Carter TR, Gracia CA, de la Vega-Leinert AC, Erhard M, Ewert F, Glendining M, House JI, Kankaanpää S, Klein RJT, Lavorel S, Lindner M, Metzger MJ, Meyer J, Mitchell TD, Reginster I, Rounsevell M, Sabaté S, Sitch S, Smith B, Smith J, Smith P, Sykes MT, Thonicke K, Thuiller W, Tuck G, Zaehle S, Zierl B (2005) Ecosystem service supply and vulnerability to global change in Europe. Science 310:1333–1337PubMedCrossRefGoogle Scholar
- Turnbull L, Wainwright J, Brazier RE (2010) Changes in hydrology and erosion over a transition from grassland to shrubland. Hydrol Process 24(4):393–414Google Scholar