High Arctic ecosystem states: Conceptual models of vegetation change to guide long-term monitoring and research

Virve Ravolainen,René Van Der Wal,Ingibjörg Svala Jónsdóttir,Åshild Ø Pedersen,Eeva M Soininen,Mads Forchhammer,Isabell Eischeid

doi:10.1007/s13280-019-01310-x

Abstract

Vegetation change has consequences for terrestrial ecosystem structure and functioning and may involve climate feedbacks. Hence, when monitoring ecosystem states and changes thereof, the vegetation is often a primary monitoring target. Here, we summarize current understanding of vegetation change in the High Arctic—the World’s most rapidly warming region—in the context of ecosystem monitoring. To foster development of deployable monitoring strategies, we categorize different kinds of drivers (disturbances or stresses) of vegetation change either as pulse (i.e. drivers that occur as sudden and short events, though their effects may be long lasting) or press (i.e. drivers where change in conditions remains in place for a prolonged period, or slowly increases in pressure). To account for the great heterogeneity in vegetation responses to climate change and other drivers, we stress the need for increased use of ecosystem-specific conceptual models to guide monitoring and ecological studies in the Arctic. We discuss a conceptual model with three hypothesized alternative vegetation states characterized by mosses, herbaceous plants, and bare ground patches, respectively. We use moss-graminoid tundra of Svalbard as a case study to discuss the documented and potential impacts of different drivers on the possible transitions between those states. Our current understanding points to likely additive effects of herbivores and a warming climate, driving this ecosystem from a moss-dominated state with cool soils, shallow active layer and slow nutrient cycling to an ecosystem with warmer soil, deeper permafrost thaw, and faster nutrient cycling. Herbaceous-dominated vegetation and (patchy) bare ground would present two states in response to those drivers. Conceptual models are an operational tool to focus monitoring efforts towards management needs and identify the most pressing scientific questions. We promote greater use of conceptual models in conjunction with a state-and-transition framework in monitoring to ensure fit for purpose approaches. Defined expectations of the focal systems’ responses to different drivers also facilitate linking local and regional monitoring efforts to international initiatives, such as the Circumpolar Biodiversity Monitoring Program.

Highlights

Vegetation plays a key role in terrestrial ecosystem functioning, with its attributes such as species composition, structure, and productivity influencing soil carbon and nitrogen cycling and supporting associated biodiversity (Wookey et al 2009)
A difference between the concept models of the international plan and the models we outline here and in the Climate-ecological Observatory for Arctic Tundra—COAT (Ims et al 2013) is that we explicitly describe expected directional impacts of individual drivers on tundra vegetation states and other ecosystem components such as the respective herbivores
Based on known and expected vegetation state changes in High Arctic Svalbard, we propose the use of conceptual models as basis for monitoring tundra vegetation

Summary

Introduction

Vegetation plays a key role in terrestrial ecosystem functioning, with its attributes such as species composition, structure, and productivity influencing soil carbon and nitrogen cycling and supporting associated biodiversity (Wookey et al 2009). Current understanding of what shapes Arctic vegetation acknowledges the influence of what can be termed press and pulse drivers (Walker et al 2005; Zimov 2005; Van der Wal 2006; Wookey et al 2009; Myers-Smith et al 2011; Brathen et al 2017), but the last decades of rapid changes in climate warrant discussion of new conceptual models that express their distinction more clearly.

Results

Conclusion