Why does sphagnum not fully decompose

The venus flytrap can also be found in the pocosin. Animals in pocosins include lots of species of reptiles, amphibians and rodents as well as black bears, bobcats , bats, white-tailed deer , opossums , raccoons , river otters, mink , muskrats , northern bobwhites, and American woodcocks. Pocosins are very vulnerable to fire when they are dry. Pocosin is an Algonquin word that means " swamp on a hill. Bogs, Fens and Pocosins Bogs Bogs are mossy wetlands. Pocosins Pocosins are evergreen shrub bogs found on the coastal plains of the southeastern United States from Virginia to Florida.

Like bogs, fens formed when glaciers retreated. Grasses and sedges are common plants in fens and fens often look like meadows. They are like bogs because they have peat deposits in them, but unlike bogs some of their water comes from small streams and groundwater. The main difference between a fen and a bog is that fens have greater water exchange and are less acidic, so their soil and water are richer in nutrients. Fens are often found near bogs and over time most fens become bogs.

Insects like mosquitoes and horseflies are common in fens as are amphibians, insect-eating birds and mammals like shrews, voles and muskrats.

Images CC BY 2. Bogs Bogs are mossy wetlands. They also point out that getting an understanding of functional traits has a direct application in Earth system modelling, as mentioned in Wullschleger et al. What Bengtsson et al. Integrating habitat and phylogenetic data are going to be essential to understanding peatlands in the future. During the war, more than a million sphagnum dressings were used per month! I had no idea AOB had such strong and proud roots.

An interesting study too regarding the mosses, thanks Alun. Skip to content Search for: Search Close. Close Menu. Decomposition of sphagnum moss isn't just about phylogenetics. Thus, the compounds providing either structural integrity or other protection against decomposers could plausibly be trade-offs for competitive growth Turetsky et al. Consequently, we expect higher amounts of compounds that slow down decomposition in hummock species. Here, we have the means to test which compounds are important to decay resistance.

We collected litter from 15 Sphagnum species from different habitats along microtopographical hummock—hollow and nutritional bog—fen—forest gradients, and compared the biochemistry of individual species with their decay rate in standard conditions, i.

We aim to analyse:. Relationships between metabolites: are there trade-offs between production of different compounds? Phylogeny versus habitat: are differences in biochemical composition among species explained by relatedness or by habitat affinity of the species? The central area is a raised ombrotrophic bog with well-developed hummock—hollow patterning, bog pools, and wetter poor-fen soaks minerotrophic seepage into the bog; Rydin and Jeglum Parts of the outer edge of the bog are covered by Scots pine Pinus sylvestris and can be described as a relatively shaded wooded marginal slope pine bog.

The bog is surrounded by a lagg fen, which is oligotrophic, but richer in solutes than the ombrotrophic bog because it receives water from the surrounding mineral soil. In addition to the sampled peat mosses, it is characterized by sedges Carex spp.

The mire is surrounded by young Norwegian spruce Picea abies forest on peaty soil. The bottom layer here is dominated by Sphagnum girgensohnii and common feather mosses. The mean temperature is It is relatively open, but reed Phragmites australis is abundant and there are hummocks with Scots pine.

Mean July temperature is Nitrogen deposition is ca. We chose 15 Sphagnum species from habitats typical of the species so as to represent different habitats, both along the microtopographical gradient, the pH gradient, and four different sections subgenera of Sphagnum Table 1 , where rich fen samples are from Glon, the others from Kulflyten.

The species represent open, ombrotrophic bog from hummocks to bog pools, rich fen, lagg fen, pine bog, and spruce forest. Sampling patches were chosen to be as uniform as possible.

We had 5 replicates per species, in total 90 samples; these were roughly half the sampling points used in Bengtsson et al. The same patches were used to sample litter for litter quality analyses and to measure decomposition. Two species S. We sampled five replicate patches from each habitat. At each sampling patch, a perforated pipe was inserted into the peat so that the height above water table HWT could be measured as the distance between the water table and the top of the Sphagnum vegetation.

HWT was measured in June data in Bengtsson et al. In October we collected Sphagnum shoots from the patches for chemical analyses of litter quality. As usual for late autumn the sites were quite wet. One or two cores of 10 cm diameter were sampled at each patch, with the aim to collect 2 g of dry litter. The capitula were removed, and the 3 subsequent cm were kept and defined as litter.

For S. Details about the extraction procedures for holocellulose, sphagnan and soluble phenolics are given in Supplement 1. To obtain the fraction of structural polysaccharides holocellulose, HC; Table 2 dried litter was coarsely homogenised with a food processor and bleached, following Ballance et al. Sphagnan extraction by acid autohydrolysis follows Ballance et al.

Although not all sphagnan was liberated during the extraction, the yield of further extractions is expected to be small and difficult to separate Ballance et al. Around The saturation took place during 10 min under continuous shaking. The acetate solution was exchanged after 4 min and the pH was increased to 7.

Then we thoroughly washed the bags with deionised water six times for 10 min to remove free ammonium ions. A sample of washing collected after the 6th wash confirmed no detectable ammonium. Each bag was then eluted with 50 mL of 20 mM HCl. After 20 min of shaking the eluate was sampled, 10 times diluted, preserved with a drop of chloroform and analysed for ammonium colorimetrically using flow injection analysis FIA; Foss Tecator AB, Sweden.

This standard gave 1. This procedure may overestimate lignin fraction as sulphuric acid digestion leaves cutins and some condensed tannins and proteins Templeton and Ehrman ; Preston et al. We modified the standard method in order to avoid autoclaving to minimize lignin dissolving and to allow batch processing of very small samples. We placed 95— mg of ball-milled litter into 50 mL PP tubes, added 1. The pellets representing Klason lignin were then resuspended with deionized water, centrifuged, dried and weighed.

In the first supernatants, we measured dissolved phenolics, i. A sample of the supernatant was diluted 36 times with 2. We prepared a specific standard solution based on the mean proportion of three prevailing phenolic monomers in degradation products of the cell walls in 13 Sphagnum species Williams et al. The mass attenuation extinction coefficient of the standard was As a proxy of carbohydrate concentration, we also measured the absorbance at nm in the supernatant after hot-acid digestion and calculated the ratio of nm and nm absorbances.

Phenolics absorb at nm due to aromatic rings; however, also heterocyclic aldehydes, particularly furfural and hydroxymethylfurfural, absorb considerably at around nm but only little at nm. These aldehydes are common products of hot acid degradation of pentoses and hexoses Hatfield and Fukushima ; Chi et al.

Hence, greater absorbance at nm relative to nm i. Therefore we introduce the deviation as a parameter dev evaluating the chemical resistance of the litters:.

Such parameter may represent a potential proxy of decay resistance. We are aware that the sum of other non extractables still represents several percent of the litter; therefore we do not interpret the absolute values of dev but use the proxy to compare species and sections and to correlate it with other parameters. To relate the biochemical composition to decomposability of the litter we used data from Bengtsson et al.

The bags in the lab were partly covered with plastic films to allow air to enter, while avoiding evaporation. The data were analysed in R version 3. We used correlation analyses to test relationships among chemical variables and decomposition mass loss , i. These relationships were also illustrated by PCAs, using the Nipals algorithm ade4 package in R; Dray and Dufour that can handle observations with missing data for some variables without removing the whole observation.

To test if metabolite composition can be used as a predictor of decay resistance we used simple and multiple linear regressions with PCA scores, or metabolites, as predictors of decay rates.

To test for differences among sections for specific variables we used ANOVAs residuals were checked for normality and homogeneity of variance and data were log-transformed when needed. Samples of the same species S. Acutifolia and lower in sect. These four variables were positively correlated 0. Different letters above panels show significant differences between the sections based on Tukey tests, which was applied on log transformed values in the case of soluble phenolics.

In a PCA based on concentrations of the six metabolites Fig. PC1 clearly separated the Acutifolia and Cuspidata species. It is notable that samples of S. The compounds with the strongest effects on axis 1 were total Klason lignin, soluble phenolics and sphagnan also when expressed as CEC. The main influence on axis 2 was HC. PCA including only the measured metabolites. Right: The distribution of the species in the trait space with x and y standard error bars , and envelopes around species from the same section.

To illustrate relationships between all variables in the data and how the species relate to each other we performed a second PCA including all variables describing mass loss in lab and field conditions , concentrations of metabolites and nutrients Fig. As with Fig. However, the second axis was determined by mineral nutrients N and P Fig. Acutifolia and one set of S.

PCA including the measured metabolites, nutrients and litter mass loss in field and lab. In support of the PCA, correlation analyses showed that lab mass loss was negatively correlated with sphagnan and thus CEC , soluble phenolics and total KL, roughly at equal strength Table 3.

To test if they jointly could explain more of the variation in decomposition we performed a multiple regression with these three variables as predictors for lab mass loss. Using the sum of centered and scaled concentrations of sphagnan, soluble phenolics and total KL as a predictor for mass loss yielded a similar result to the multiple regression Fig. Adding the nutrients N or P as predictors in the model including all three metabolites as separate predictors, slightly but significantly raised the variation explained Adj.

Other potential models e. Since we had field decomposition data available for our samples, we also analysed the relationships between field mass loss and litter quality. The relationships were overall much weaker compared to the ones between lab mass loss and litter quality parameters. There were positive correlations with most chemical parameters we measured, but no correlations with mineral nutrients. The chemical resistance of fast-decomposing species in sect.

Cuspidata and partly also in sect. Sphagnum was significantly lower compared to sect. This means that the abundant KL of decay-resistant Acutifolia is resistant to chemical acid-degradation.

Since both carbohydrates Turetsky et al. However, we found that there are relatively close positive correlations among all these metabolites as well as between them and litter decay resistance. These parameters were correlated also with several others, including those describing litter chemical resistance.

As a result, we found no signs of trade-offs among species in production of metabolites related to decay resistance, but rather that the combination of high concentrations of these metabolites results in slower decay Fig. This does not contradict the trade-off in resource partitioning between metabolic and structural carbohydrates Turetsky et al.

Linked to this, our results support the suggested trade-off between growth and decay Turetsky et al. In our field decomposition experiment each species was exposed to its own environment, where the microhabitats greatly impact decomposition. Hummocks are well aerated, which means good decomposition potential, but hummock species generally have a high intrinsic decomposition resistance Bengtsson et al.

Hollows, on the other hand, are wet and have a poorer decomposition potential, but hollow species are less resistant to decomposition. This is illustrated in our results by the strong relationships between mass loss in standard conditions, which would represent intrinsic decay resistance, and litter quality, in contrast to the absent relationships between field mass loss and metabolites.

For example, plant soluble phenolics are known to delay litter microbial decomposition and this effect can be magnified in field conditions due to accumulation of phenolics under anoxic conditions in the catotelm Freeman et al.