Linking habitat modification to catastrophic shifts and vegetation patterns in bogs

Abstract

Paleoecological studies indicate that peatland ecosystems may exhibit bistability. This would mean that these systems are resilient to gradual changes in climate, until environmental thresholds are passed. Then, ecosystem stability is lost and rapid shifts in surface and vegetation structure at landscape scale occur. Another remarkable feature is the commonly observed self-organized spatial vegetation patterning, such as string-flark and maze patterns. Bistability and spatial selforganization may be mechanistically linked, the crucial mechanism being scale-dependent (locally positive and longer-range negative) feedback between vegetation and the peatland environment. Focusing on bogs, a previous model study shows that nutrient accumulation by vascular plants can induce such scale-dependent feedback driving pattern formation. However, stability of bog microforms such as hummocks and hollows has been attributed to different local interactions between Sphagnum, vascular plants, and the bog environment. Here we analyze both local and longer-range interactions in bogs to investigate the possible contribution of these different interactions to vegetation patterning and stability. This is done by a literature review, and subsequently these findings are incorporated in the original model. When Sphagnum and encompassing local interactions are included in this model, the boundaries between vegetation types become sharper and also the parameter region of bistability drastically increases. These results imply that vegetation patterning and stability of bogs could be synergistically governed by local and longerrange interactions. Studying the relative effect of these interactions is therefore suggested to be an important component of future predictions on the response of peatland ecosystems to climatic changes.

Nutrients and Hydrology Indicate the Driving Mechanisms of Peatland Surface Patterning

“…In turn, evapotranspiration and hydraulic conductivity influence the water balance and, hence, regulate acrotelm thickness (Hilbert et al 2000;Belyea and Malmer 2004;Belyea and Baird 2006). The possibility of a combination of mechanisms together driving peatland surface patterning has also been suggested in previous theoretical (Larsen et al 2007;Eppinga et al 2009) and empirical (Eppinga et al 2008) studies. Therefore, there is a need to investigate the interaction between these mechanisms with respect to peatland pattern formation, rather than studying the mechanisms in isolation using separate models.…”

“…It should be noted that many other mechanisms have been proposed as explanations for pattern formation (see Eppinga et al 2008Eppinga et al , 2009 for reviews), but in this study we focused on the three mechanisms that have been most prominently examined in recent model studies. We combined elements of the models of Hilbert et al (2000), Belyea and Clymo (2001), Pastor et al (2002), Rietkerk et al (2004a), and Couwenberg (2005).…”

“…Nutrients become available again through mineralization of vascular plant litter, but this only increases nutrient availability on the local scale at which the litter is deposited (within the ridge). Models predict that this local recycling effect outweighs the effect of nutrient uptake, meaning that nutrient concentrations in the mire water under ridges also increase (Rietkerk et al 2004a;Eppinga et al 2008Eppinga et al , 2009. Because higher nutrient availability will lead to an increase in vascular plant biomass, this is a self-reinforcing process, which will be referred to as the nutrient accumulation mechanism (cf.…”

“…Rietkerk et al 2004a). Models show that the nutrient accumulation mechanism could indeed explain the formation of maze patterns on flat ground (Rietkerk et al 2004a;Eppinga et al 2009). Moreover, model simulations show that the nutrient accumulation mechanism may also drive the formation of individual hummocks on flat ground and linear ridge-hollow patterning on peatland slopes (Rietkerk et al 2004a;Eppinga et al 2009).…”

Understanding the Long Term Ecosystem Stability of a Fen Mire by Analyzing Subsurface Geology, Eco-Hydrology and Nutrient Stoichiometry – Case Study of the Rospuda Valley (NE Poland)

“…Belyea and Baird 2006, Eppinga et al 2009, Morris et al 2011, whereas such analyses are scarce in groundwater-fed fens (but see e.g., Michaelis 2002), which belong to the most threatened mire types worldwide, having vanished from agricultural drainage, landscape transformation and eutrophication (Van Diggelen et al 2006). Relating long-term ecosystem dynamics of fens to their local geological settings and internal ecological processes should help to improve predictions about their future stability and propose more effective strategies of their long-term conservation.…”