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Ecosystem feedbacks and cascade processes: understanding their role in the responses of arctic and alpine ecosystems to environmental change

Citation
Wookey P, Aerts R, Bardgett RD, Baptist F, Brathen KA, Cornelissen JHC, Gough L, Hartley I, Hopkins D, Lavorel S & Shaver GR (2009) Ecosystem feedbacks and cascade processes: understanding their role in the responses of arctic and alpine ecosystems to environmental change, Global Change Biology, 15 (5), pp. 1153-1172.

Abstract
Global environmental change, related to climate change and the deposition of airborne N-containing contaminants, has already resulted in shifts in plant community composition among plant functional types in arctic and temperate alpine regions. In this paper, we review how key ecosystem processes will be altered by these transformations, the complex biological cascades and feedbacks that may result, and some of the potential broader consequences for the earth system. Firstly, we consider how patterns of growth and allocation, and nutrient uptake, will be altered by the shifts in plant dominance. The ways in which these changes may disproportionately affect the consumer communities, and rates of decomposition, are then discussed. We show that the occurrence of a broad spectrum of plant growth forms in these regions (from cryptogams to deciduous and evergreen dwarf shrubs, graminoids and forbs), together with hypothesized low functional redundancy, will mean that shifts in plant dominance result in a complex series of biotic cascades, couplings and feedbacks which are supplemental to the direct responses of ecosystem components to the primary global change drivers. The nature of these complex interactions is highlighted using the example of the climate-driven increase in shrub cover in low arctic tundra, and the contrasting transformations in plant functional composition in mid-latitude alpine systems. Finally, the potential effects of the transformations on ecosystem properties and processes which link with the earth system are reviewed. We conclude that the effects of global change on these ecosystems, and potential climate-change feedbacks, can not be predicted from simple empirical relationships between processes and driving variables. Rather, the effects of changes in species distributions and dominances on key ecosystem processes and properties must also be considered, based upon best estimates of the trajectories of key transformations, their magnitude and rates of change.

Keywords
Arctic; Alpine; Carbon; Ecosystem; Energy; Global change; Feedback; Nitrogen; Herbivory; Plant functional type

Subject headings
Plants, Effect of global warming on Arctic regions; Plants, Effect of global warming on Alpine regions; Plant ecophysiology Arctic regions; Plant ecophysiology Alpine regions; Climatic changes Environmental aspects; Global environmental change

StatusPublished
AuthorsWookey Philip, Aerts Rien, Bardgett Richard D, Baptist Florence, Brathen Kari Anne, Cornelissen J Hans C, Gough Laura, Hartley Iain, Hopkins David, Lavorel Sandra, Shaver Gaius R
Publication date05/2009
Date accepted by journal08/09/2008
PublisherBlackwell Publishing
ISSN 1354-1013
LanguageEnglish

Journal
Global Change Biology: Volume 15, Issue 5 (2009-05)

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