•Carbon (C) stocks in three upland heath vegetation types were compared across seven UK sites.•Graminoid-dominated (degraded), Calluna vulgaris-dominated (target) and actively restored heath were ...compared.•Degraded heath had lower total C stock (vegetation and soil to 15cm depth) than target heath.•Restoration provided a C benefit of 0.60±0.70t Cha−1yr−1 (since restoration).•Potential for C accumulation within upland heath is an additional justification for vegetation restoration.
Restoration of degraded upland habitats has the potential to improve carbon (C) sequestration, thus helping offset national greenhouse gas emissions. Here we test the hypotheses (1) that degraded upland heath, dominated by graminoids, will have higher rates of soil respiration and smaller C pools than long established, Calluna vulgaris (Calluna) dominated upland heath, and (2) that restoration of degraded heath will increase carbon pools and decrease soil respiration towards that of “target” Calluna heath.
Soil respiration and total and recalcitrant C stocks in above- and below-ground vegetation and in the topsoil (to a depth of 15cm) were estimated at seven upland sites in Northern England and Scotland. Three vegetation types were present at each site; graminoid-dominated upland heath that had formerly been Calluna-dominated upland heath (“degraded”); restored upland heath, converted from graminoid to dwarf shrub dominance (“restored”) and long-established, Calluna-dominated (“target”) upland heath.
Soil respiration did not differ between the three vegetation types. Degraded areas contained a larger C pool in the vegetation but a lower soil C pool and total C stock than target areas. Restored areas held similar vegetation, soil and total C stocks to those of target areas. All areas had similar pools of recalcitrant C in their vegetation, but both target and restored areas contained more recalcitrant C in the soil, and in total, than degraded areas.
The C benefit of restoration varied between sites, partly due to the abundance of Molinia caerulea in degraded vegetation at some sites, but the overall C benefit of restoring Calluna-dominated upland heath was 0.60±0.70t Cha−1yr−1 since restoration. Restoration also increased the size of the recalcitrant C pool, which will increase C residence time and hence soil C accumulation in the longer term. Thus restoration of degraded areas is a valid option for promoting C sequestration within upland heath.
A multiple substrate induced respiration (SIR) assay, using
14C-labelled carbon sources, was used to evaluate community level physiological profiles (CLPP) of the microbial community in peat horizons ...of differing degrees of humification. The separation and grouping of the peat horizons by CLPP was similar to the pattern produced by analysis of the organic carbon chemistry of the peat horizons by Fourier Transform Infrared (FTIR) spectroscopy and therefore reflected the level of decomposition. Partial redundancy analysis showed that a large proportion (68.7%) of the variability in the CLPP data could be attributed to the ratio of polysaccharide to ‘carboxylate’ FTIR bands alone. The multiple substrate SIR technique may, therefore, be a powerful technique to further elucidate the influence of the microbial constituent of peat on the potential activity and patterns of cycling of labile carbon in peatlands.
Root exudates and litter are the main sources of inputs of labile carbon into the microbial pool in successional ecosystems. Here we studied whether typical pioneer species (
Eriophorum vaginatum,
...Eriophorum angustifolium and
Calluna vulgaris) alter the functional response of the microbial community of a previously cutover peatland. Peat was sampled at three depths (0–5, 20–25 and 40–45
cm) from beneath these species and from bare soil areas. MicroResp analysis using ecologically relevant, radiolabelled, carbon sources showed significant separation in community level physiological profiles (CLPP) of soil microorganisms according to peat depth. This effect was also reflected in microbial biomass carbon, which also decreased with increasing depth. Furthermore, distinct differences in CLPP were observed between the three plant species and the bare soil in the absence of an effect on microbial biomass carbon or total soil carbon. The plant species effects were driven by differential utilisation of xylose, glutamic acid, lysine and phenylethylamine. The data suggest that ‘new’ carbon inputs from plants colonising abandoned cutover peatland may support communities of microorganisms that have functionally distinct roles in carbon turnover.
1. While establishment of vegetation is the most visual indicator of regeneration on cutover peatland, the reinstatement of belowground functions is less well understood. Vegetation succession ...results in differences in peat quality in terms of C availability. The respiratory response of the soil microbial community to ecologically relevant substrates (community-level physiological profile, CLPP) such as those found in rhizosphere exudates and litter hydrolysates, is thought to reflect the activity and functional diversity of the soil microbial community, especially those involved in turnover of soluble photosynthate-derived C. 2. The relationship between CLPP and typical regeneration stages was investigated at five European peatlands, each with up to five sites representing a gradient of natural regeneration stages. We aimed to determine whether unaided revegetation consistently affected soil microbial CLPP, which environmental factors explained variation in CLPP on the scale of individual peatlands, and if these factors were consistent across different peatlands. 3. Within each peatland, a decomposition index based on diagnostic bands in Fourier transform-infrared spectra indicated that regeneration had generally started from a common base and that the influence of vegetation on the decomposition index declined with depth. In parallel, differences in vegetation cover between regeneration stages resulted in significantly different CLPP, but this effect decreased rapidly with soil depth. The magnitudes of the effect of vegetation succession versus soil depth appeared to be linked with the age range of the regeneration gradients. Hence, the effect of vegetation on CLPP is effectively diluted due to the remaining organic matter. Specific plant species described significant proportions of CLPP variability but these species were not consistent across peatland types. The effects of soil depth appeared to be peatland-specific. 4. Synthesis and applications. Together, the results indicate significant responses of the microbial community to vegetation succession, with the strength of the effect probably dependent on quantities of labile C allocation to the soil microbial community. Therefore, particularly in the early stages of regeneration of cutover peatlands, CLPP could provide vital information about the relative importance of different plant functional types on potential rates of labile C turnover.
Active management to encourage the expansion of native pine woodland onto neighbouring moorland has been suggested as a tool to promote increases in forest area to combat climate change. Low ...intensity burning has previously been shown to increase pine seedling establishment, however the effect of this on below-ground diversity and functioning in these important terrestrial carbon stores is equivocal. Here, we assessed the effect of a single burn and grazing exclosures after a 6 year period on soil microbial respiratory activity and fungal community structure using terminal restriction fragment polymorphism (T-RFLP) analysis. The combined data suggest that the strategy of a single prescribed burn to facilitate Scots pine establishment had no lasting effect on either fungal taxonomic richness, fungal community composition or microbial activity. Thus, our findings support the proposed use of single, low intensity, prescribed burns in regenerating Scots pine forests as a low impact management tool.
To understand the implications of atmospheric nitrogen deposition on carbon turnover in peatlands, we conducted a 13C pulse labeling experiment on Calluna vulgaris and Eriophorum vaginatum already ...receiving long-term (5 years) amendments of 56 kg N ha−1 y−1 as ammonium or nitrate. We examined shoot tissue retention, net ecosystem respiration returns of the 13C pulse, and soil porewater DOC content under the two species. 13C fixation in Eriophorum leaves was enhanced with nitrogen addition and doubled with nitrate supply. This newly fixed C appeared to be relocated below-ground faster with nitrogen fertilization as respiration returns were unaffected by N inputs. By contrast, increases in 13C fixation were not observed in Calluna. Instead, net ecosystem respiration rates over Calluna increased with N fertilization. There was no significant label incorporation into DOC, suggesting a conservative strategy of peatland vegetation regarding allocation of C through root exudation. Greater concentrations of total DOC were identified with nitrate addition in Calluna. Given the long-term nature of the experiment and the high N inputs, the overall impacts of nitrogen amendments on the fate of recently synthesized C in Eriophorum and Calluna in this ombrotrophic peatland were surprisingly more moderate than originally hypothesized. This may be due to N being effectively retained within the bryophyte layer, thus limiting, and delaying the onset of, below-ground effects.
► We investigated the effect of long term N deposition on carbon turnover in peatlands. ► Carbon fixation was enhanced in Eriophorum vaginatum under N deposition. ► Ecosystem respiration of the fixed C was enhanced over Calluna vulgaris stands. ► Below-ground effects were moderate. ► This may be due to effective N retention in the bryophyte layer.
Cutover peatlands are often rapidly colonised by pioneer plant species, which have the potential to affect key ecosystem processes such as carbon (C) turnover. The aim of this study was to ...investigate how plant cover and litter type affect fungal community structure and litter decomposition in a cutover peatland. Intact cores containing
Eriophorum vaginatum,
Eriophorum angustifolium,
Calluna vulgaris and bare soil were removed and a mesh bag with litter from only one of each of these species or fragments of the moss
Sphagnum auriculatum was added to each core in a factorial design. The presence or absence of live plants, regardless of the species, had no effect on mass loss, C, nitrogen (N) or phosphorus (P) concentrations of the litter following 12 months of incubation. However, there was a very strong effect of litter type on mass loss and concentrations of C, N and P between most combinations of litter. Similarly, plant species did not affect fungal community structure but litter type had a strong effect, with significant differences between most pairs of litter types. The data suggest that labile C inputs via rhizodeposition from a range of plant functional types that have colonised cutover bogs for 10–15 years have little direct effect on nutrient turnover from plant litter and in shaping litter fungal community structure. In contrast, the chemistry of the litter they produce has much stronger and varied effects on decomposition and fungal community composition. Thus it appears that there is distinct niche differentiation between the fungal communities involved in turnover of litter versus rhizodeposits in the early phases of plant succession on regenerating cutover peatlands.
Assessing CLPPs using MicroResp Chapman, Stephen J.; Campbell, Colin D.; Artz, Rebekka R. E.
Journal of soils and sediments,
12/2007, Letnik:
7, Številka:
6
Journal Article
Recenzirano
Soil microbial community diversity has been suggested as a way of assessing the 'health' or 'quality' of soils. While molecular (genetic) or biochemical (phenotypic) measurements of microbial ...diversity have their place, functional diversity is popular in that it relates to the activity of the soil microflora, particularly in the carbon cycle. Community Level Physiological Profiles (CLPPs) are usually assessed by carbon substrate utilization. The aim here is to review the various methods available for CLPP assessment. The original method for CLPP determination was based upon the Biolog plate with its range of 95 carbon substrates and many studies have been employing this over the past 15 years. However, a number of criticisms have been leveled at the method, principally that it relies upon the growth of an extracted microbial population, which may not represent the true functioning of the whole soil. A multiple carbon-source, substrate induced respiration method (multi-SIR) was developed that did measure the response of the whole soil community without the need for growth but it did not have the convenience of the microtitre plate format. MicroResp(TM) was designed to overcome the deficiencies in both methods and we have applied it to a range of media including mineral and organic soils, sediments and litter. In addition we have adapted the method to the testing of a wide range of carbon substrates such as hydrocarbons, terpenes and pesticides. The MicroResp(TM) technique covers the middle road of relevance and convenience, being a 'whole soil' method in a flexible microtitre plate format. It also has the advantage that it can be adapted for the use of radiolabelled (^sup 14^C) substrates, which increases the specificity and sensitivity of the assay. A few direct comparisons between MicroResp(TM) have been made. We have found that its discriminatory ability compares favourably with Biolog while other users have reported it to be superior to the multiple SIR approach. A number of laboratories around the world are now utilizing MicroResp(TM) and reporting good sensitivity to changes to the microbial community due to such varied factors as age of forest rehabilitation, heavy metal treatment, hydrocarbon exposure, salinity, peatland vegetation, cropping system and tree clone type. A comparison of the available methods reveals that each has its advantages and drawbacks. The choice of method may depend upon the particular hypotheses or questions. MicroResp(TM) offers a convenient, rapid and sensitive method for the determination of Community Level Physiological Profiles. Its application in a number of case studies has demonstrated its utility and advantages over other methods though its full potential for characterizing soil activity is yet to be realized. Increasing awareness of the environmental pressures on soils and the need to monitor soil health has resulted in a range of potential indicators. Microbial functional diversity is one such indicator that seeks to characterize a core soil attribute. The availability of rapid methods for its assessment will aid our understanding of such pressures on basic soil functioning.PUBLICATION ABSTRACT
Peatlands are wetland ecosystems with great significance as natural habitats and as major global carbon stores. They have been subject to widespread exploitation and degradation with resulting losses ...in characteristic biota and ecosystem functions such as climate regulation. More recently, large-scale programmes have been established to restore peatland ecosystems and the various services they provide to society. Despite significant progress in peatland science and restoration practice, we lack a process-based understanding of how soil microbiota influence peatland functioning and mediate the resilience and recovery of ecosystem services, to perturbations associated with land use and climate change.
We argue that there is a need to: in the short-term, characterise peatland microbial communities across a range of spatial and temporal scales and develop an improved understanding of the links between peatland habitat, ecological functions and microbial processes; in the medium term, define what a successfully restored ‘target’ peatland microbiome looks like for key carbon cycle related ecosystem services and develop microbial-based monitoring tools for assessing restoration needs; and in the longer term, to use this knowledge to influence restoration practices and assess progress on the trajectory towards ‘intact’ peatland status.
Rapid advances in genetic characterisation of the structure and functions of microbial communities offer the potential for transformative progress in these areas, but the scale and speed of methodological and conceptual advances in studying ecosystem functions is a challenge for peatland scientists. Advances in this area require multidisciplinary collaborations between peatland scientists, data scientists and microbiologists and ultimately, collaboration with the modelling community.
Developing a process-based understanding of the resilience and recovery of peatlands to perturbations, such as climate extremes, fires, and drainage, will be key to meeting climate targets and delivering ecosystem services cost effectively.
•Although microbes are key to peatland function the underpinning processes are unclear.•Microbial characterisation is needed across a range of sites, depths and conditions.•Temporal and spatial changes in microbial communities need to be linked to functions.•Potential to use microbiome as a monitoring tool for peatland restoration progress•Enhancing microbial communities could improve peatland resilience.
Abstract
The survival characteristics of Escherichia coli O157:H7 in private drinking water wells were investigated to assess the potential for human exposure. A non-toxigenic, chromosomally ...lux-marked strain of E. coli O157:H7 was inoculated into well water from four different sites in the North East of Scotland. These waters differed significantly in their heavy metal contents as well as nutrient and bacterial grazer concentrations. Grazing and other biological factors were studied using filtered (3 and 0.2 µm) and autoclaved water. The survival of E. coli O157:H7 was primarily decreased by elevated copper concentrations. This hypothesis was supported by acute toxicity assay data. In addition, significant protozoan predation effects were observed in untreated water when compared with survival rates in filtered water. The combination of these two factors in particular determines the survival time of the pathogen in a private water well. It therefore appears that wells with higher water quality as assessed using the European Union Drinking Water Directive standards will also allow survival of E. coli O157:H7 for much longer periods.
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