Above‐ and belowground linkages in Sphagnum peatland: climate warming affects plant‐microbial interactions

Abstract

Peatlands contain approximately one third of all soil organic carbon (SOC). Warming can alter above- and belowground linkages that regulate soil organic carbon dynamics and C-balance in peatlands. Here we examine the multiyear impact of in situ experimental warming on the microbial food web, vegetation, and their feedbacks with soil chemistry. We provide evidence of both positive and negative impacts of warming on specific microbial functional groups, leading to destabilization of the microbial food web. We observed a strong reduction (70%) in the biomass of top-predators (testate amoebae) in warmed plots. Such a loss caused a shortening of microbial food chains, which in turn stimulated microbial activity, leading to slight increases in levels of nutrients and labile C in water. We further show that warming altered the regulatory role of Sphagnum-polyphenols on microbial community structure with a potential inhibition of top predators. In addition, warming caused a decrease in Sphagnum cover and an increase in vascular plant cover. Using structural equation modelling, we show that changes in the microbial food web affected the relationships between plants, soil water chemistry, and microbial communities. These results suggest that warming will destabilize C and nutrient recycling of peatlands via changes in above- and belowground linkages, and therefore, the microbial food web associated with mosses will feedback positively to global warming by destabilizing the carbon cycle. This study confirms that microbial food webs thus constitute a key element in the functioning of peatland ecosystems. Their study can help understand how mosses, as ecosystem engineers, tightly regulate biogeochemical cycling and climate feedback in peatlands.

Experimental warming differentially affects microbial structure and activity in two contrasted moisture sites in a Sphagnum-dominated peatland

“…At the Bog site, the increase in air temperature was also associated with an increase in peat water content (Table 3). This result is surprising since most studies on experimental warming reported a decrease or no effect on peat moisture (Hollister et al, 2006;Dorrepaal et al, 2009;Bokhorst et al, 2011;Delarue et al, 2011a;Jassey et al, 2013). The question is therefore whether this effect was due to an experimental artefact or whether it results from a thermodynamic constraint.…”

“…Such a pattern is known as the enzymatic latch theory (Freeman et al, 2001). Following such cascading effects, various studies suggested that peat OM decomposition will be enhanced by climate warming (Dorrepaal et al, 2009;Fenner and Freeman, 2011;Jassey et al, 2013). However, the studies were mainly conducted during the summer months, when environmental constraints, i.e.…”

Nitrogen and methanogen community composition within and among three Sphagnum dominated peatlands in Scandinavia

“…In addition, these microhabitats are characterized by a different set of peat mosses and accompanying vascular plants (Saarnio et al, 1997;Rydin and Jeglum, 2006;Robroek et al, 2009) which ultimately control the quantity and quality of the organic matter available for microbial decomposition (Kettunen and Kaitala, 1996;Galand et al, 2003;Andersen et al, 2013;Jassey et al, 2013). In short, the composition of the methanogenic archaeal communities in peatlands shows a tight link with the microtopography in the peatland (Galand et al, 2003;Yavitt et al, 2011).…”

“…increased variability in precipitation and increased temperature (IPCC, 2007), together with increasing N deposition loading (Phoenix et al, 2012) are believed to, directly or indirectly, affect the microtopography and the variables controlling the potential methane production. This may affect the methane emissions and the carbon allocation (Limpens et al, 2008;Luo and Weng, 2011;Jassey et al, 2013).…”

Environmental DNA COI barcoding for quantitative analysis of protists communities: A test using the Nebela collaris complex (Amoebozoa; Arcellinida; Hyalospheniidae)

“…Although this may be seen as a bias if the goal is to estimate proportions of individuals it may actually be an advantage for community ecology studies. Community ecology studies of testate amoebae are indeed increasingly based on biovolume-corrected community data obtained by direct microscopy (Jassey et al 2013).…”