Trade‐offs in resource allocation among moss species control decomposition in boreal peatlands

Abstract

Summary 1.We separated the effects of plant species controls on decomposition rates from environmental controls in northern peatlands using a full factorial, reciprocal transplant experiment of eight dominant bryophytes in four distinct peatland types in boreal Alberta, Canada. Standard fractionation techniques as well as compound-specific pyrolysis molecular beam mass spectrometry were used to identify a biochemical mechanism underlying any interspecific differences in decomposition rates. 2. We found that over a 3-year field incubation, individual moss species and not micro-environmental conditions controlled early stages of decomposition. Across species, Sphagnum mosses exhibited a trade-off in resource partitioning into metabolic and structural carbohydrates, a pattern that served as a strong predictor of litter decomposition. 3. Decomposition rates showed a negative co-variation between species and their microtopographic position, as species that live in hummocks decomposed slowly but hummock microhabitats themselves corresponded to rapid decomposition rates. By forming litter that degrades slowly, hummock mosses appear to promote the maintenance of macropore structure in surface peat hummocks that aid in water retention. 4. Synthesis . Many northern regions are experiencing rapid climate warming that is expected to accelerate the decomposition of large soil carbon pools stored within peatlands. However, our results suggest that some common peatland moss species form tissue that resists decomposition across a range of peatland environments, suggesting that moss resource allocation could stabilize peatland carbon losses under a changing climate.

Plant Litter Decomposition and Nutrient Release in Peatlands

“…The role of the phenolics/N quotient in affecting Sphagnum litter decomposition is confirmed by higher decomposability of litter deposited by minerotrophic Sphagnum species compared to ombrotrophic Sphagnum litter , the latter being characterized by a higher phenolic content [Rudolph and Samland, 1985]. It has also been suggested that a better predictor of moss decomposition rate in peatlands is represented by the quotient between fructose/pentose carbohydrates in initial litter [Turetsky et al, 2008], so that moss species investing relatively more in structural carbohydrates (i.e., pentosans) such as hummock-forming Sphagna are more resistant than moss species investing relatively more in metabolic carbohydrates (i.e., fructosans), such as hollow inhabiting Sphagna. In this review, the limited data did not reveal a significant role for C/nutrient quotients on Sphagnum litter decomposition, although the C/P and C/N quotient have been reported to significantly explain mass loss of Sphagnum litter after 1 year of field burial [Hogg et al, 1994;Aerts et al, 2001;Limpens and Berendse, 2003;.…”

“…This can be explained taking into account the role of litter chemistry, in particular the relatively higher content of structural carbohydrates in Sphagnum species forming high hummocks [Turetsky et al, 2008]. Thus, the complex interactions between physical conditions at habitat scale and Sphagnum litter chemistry play an important role in controlling the topographical variability of peatland surface and associated rates on peat accumulation [Ohlson and Dahlberg, 1991;Belyea and Malmer, 2004].…”

“…AUR is acid unhydrolyzable residue. Sources are Aerts and De Caluwe [1997], Scheffer et al [2001], Thormann et al [2001], Bridgham and Richardson [2003], Aerts et al [2006], Bubier et al [2007], Breeuwer et al [2008], Turetsky et al [2008], Bragazza, unpublished data [2008]. so that below a certain level of litter moisture, decomposition initially slows down and then stops completely [Crow and Wieder, 2005;Aerts, 2006;Gerdol et al, 2007].…”

Biochemical determinants of litter quality in 15 species of Sphagnum

“…Anoxia is particularly linked to the lower peat layers (the permanently water-logged catotelm), while the acrotelm is intermittently oxic (Morris et al 2011;Rydin and Jeglum 2013). Decay resistance of dead plants differ for different growth forms (Dorrepaal 2005), but also between different species of Sphagnum (Turetsky et al 2008;Hájek 2009;Bengtsson et al 2016a). Consequently, knowledge about the litter quality of ecosystem engineers, such as Sphagnum spp., is crucial to the understanding of ecosystem functions in northern peatlands.…”

The Impact of Experimental Temperature and Water Level Manipulation on Carbon Dioxide Release in a Poor Fen in Northern Poland

“…However, the relative importance of temperature and hydrological conditions for R ECO is unclear and seems to depend on their relative effect on autotrophic and heterotrophic pathways, which might be decoupled (Lafleur et al 2005). Remarkably, the effect of vegetation on heterotrophic respiration seems to be larger than the effect of temperature (Ward et al 2015) or water table (Turetsky et al 2008), highlighting the importance of these biotic controls on peatland carbon fluxes.…”