Showing papers by "Richard D. Bardgett published in 2011"
TL;DR: There was a positive relationship between species richness and C cycling in 77-100% of low-diversity experiments, even when the richness of just one biotic group was manipulated, whereas positive relationships occurred less frequently in studies with greater richness, which indicated functional redundancy at low extents of diversity.
Abstract: Biodiversity and carbon (C) cycling have been the focus of much research in recent decades, partly because both change as a result of anthropogenic activities that are likely to continue. Soils are extremely species-rich and store approximately 80% of global terrestrial C. Soil organisms play a key role in C dynamics and a loss of species through global changes could influence global C dynamics. Here, we synthesize findings from published studies that have manipulated soil species richness and measured the response in terms of ecosystem functions related to C cycling (such as decomposition, respiration and the abundance or biomass of decomposer biota) to evaluate the impact of biodiversity loss on C dynamics. We grouped studies where one or more biotic groups had been manipulated to include a richness of 10 species in order to reflect 'low' and 'high' extents of diversity manipulations. There was a positive relationship between species richness and C cycling in 77-100% of low-diversity experiments, even when the richness of just one biotic group was manipulated, whereas positive relationships occurred less frequently in studies with greater richness (35-64%). Moreover, when positive relationships were observed, these often indicated functional redundancy at low extents of diversity or that community composition had a stronger influence on C cycling than did species richness. Initial reductions in soil species richness resulting from global changes are unlikely to alter C dynamics significantly unless particularly influential species are lost. However, changes in community composition, and the loss of species with an ability to facilitate specialized soil processes related to C cycling, as a result of global changes, may have larger impacts on C dynamics.
471 citations
TL;DR: In this article, the effects of species gain and loss have been investigated. But the authors focus on traits associated with species loss, and much remains unknown about how traits that predispose species to extinction affect ecological processes.
Abstract: Ecosystems worldwide are losing some species and gaining others, resulting in an interchange of species that is having profound impacts on how these ecosystems function. However, research on the effects of species gains and losses has developed largely independently of one another. Recent conceptual advances regarding effects of species gain have arisen from studies that have unraveled the mechanistic basis of how invading species with novel traits alter biotic interactions and ecosystem processes. In contrast, studies on traits associated with species loss are fewer, and much remains unknown about how traits that predispose species to extinction affect ecological processes. Species gains and losses are both consequences and drivers of global change; thus, explicit integration of research on how both processes simultaneously affect ecosystem functioning is key to determining the response of the Earth system to current and future human activities.
408 citations
TL;DR: In this paper, the authors identify in three European mountain regions the ecosystem services of grassland that different stakeholders identify (which ecosystem services for whom), the relative rankings of these ecosystem services, and how stakeholders perceive the provision of ecosystem services to be related to agricultural activities.
Abstract: The concept of ecosystem services is increasingly being used by scientists and policy makers However, most studies in this area have focussed on factors that regulate ecosystem functions (ie the potential to deliver ecosystem services) or the supply of ecosystem services In contrast, demand for ecosystem services (ie the needs of beneficiaries) or understanding of the concept and the relative ranking of different ecosystem services by beneficiaries has received limited attention The aim of this study was to identify in three European mountain regions the ecosystem services of grassland that different stakeholders identify (which ecosystem services for whom), the relative rankings of these ecosystem services, and how stakeholders perceive the provision of these ecosystem services to be related to agricultural activities We found differences: (1) between farmers’ perceptions of ecosystem services across regions and (2) within regions, between knowledge of ecosystem services gained by regional experts through education and farmers’ local field-based knowledge Nevertheless, we identified a common set of ecosystem services that were considered important by stakeholders across the three regions, including soil stability, water quantity and quality, forage quality, conservation of botanical diversity, aesthetics and recreation (for regional experts), and forage quantity and aesthetic (for local farmers) We observed two contrasting stakeholder representations of the effects of agricultural management on ecosystem services delivery, one negative and the other positive (considering low to medium management intensity) These representations were determined by stakeholders’ perceptions of the relationships between soil fertility and biodiversity Overall, differences in perceptions highlighted in this study show that practitioners, policy makers and researchers should be more explicit in their uses of the ecosystem services concept in order to be correctly understood and to foster improved communication among stakeholders
261 citations
TL;DR: In this paper, the authors investigated C and nitrogen (N) accumulation rates in soil and C and N pools in vegetation in a long-term field experiment (16 years) in which fertilizer application and plant seeding were manipulated and the abundance of the legume Trifolium pratense was manipulated for the last 2 years.
Abstract: 1. In Europe, grassland agriculture is one of the dominant land uses. A major aim of European agri-environment policy is the management of grassland for botanical diversity conservation and restoration, together with the delivery of ecosystem services including soil carbon (C) sequestration. 2. To test whether management for biodiversity restoration has additional benefits for soil C sequestration, we investigated C and nitrogen (N) accumulation rates in soil and C and N pools in vegetation in a long-term field experiment (16 years) in which fertilizer application and plant seeding were manipulated. In addition, the abundance of the legume Trifolium pratense was manipulated for the last 2 years. To unravel the mechanisms underlying changes in soil C and N pools, we also tested for effects of diversity restoration management on soil structure, ecosystem respiration and soil enzyme activities. 3. We show that the long-term biodiversity restoration practices increased soil C and N storage especially when these treatments were combined with the recent promotion of the legume Trifolium pratense, sequestering 317 g C and 35 g N m−2 year−1 in the most successful management treatment. These high rates of C and N accumulation were associated with reduced ecosystem respiration, increased soil organic matter content and improved soil structure. Cessation of fertilizer use, however, reduced the amount of C and N contained in vegetation. 4. Synthesis and applications. Our findings show that long-term diversity restoration practices can yield significant benefits for soil C storage when they are combined with increased abundance of a single, sub-ordinate legume species. Moreover, we show that these management practices deliver additional ecosystem benefits such as N storage in soil and improved soil structure.
172 citations
TL;DR: The data indicate that small soil animals have distinct biogeographical distributions and provide unique evidence of the link between above-ground and below-ground biodiversity at a global scale.
Abstract: The global distribution of soil animals and the relationship of below-ground biodiversity to above-ground biodiversity are not well understood. We examined 17,516 environmental 18S rRNA gene sequences representing 20 phyla of soil animals sampled from 11 locations covering a range of biomes and latitudes around the world. No globally cosmopolitan taxa were found and only 14 of 2,259 operational taxonomic units (OTUs) found were common to four or more locations. Half of those were circumpolar and may reflect higher connectivity among circumpolar locations compared with other locations in the study. Even when OTU assembly criteria were relaxed to approximate the family taxonomic level, only 34 OTUs were common to four or more locations. A comparison of our diversity and community structure data to environmental factors suggests that below-ground animal diversity may be inversely related to above-ground biodiversity. Our data suggest that greater soil inorganic N and lower pH could explain the low below-ground biodiversity found at locations of high above-ground biodiversity. Our locations could also be characterized as being dominated by microarthropods or dominated by nematodes. Locations dominated by arthropods were primarily forests with lower soil pH, root biomass, mean annual temperature, low soil inorganic N and higher C:N, litter and moisture compared with nematode-dominated locations, which were mostly grasslands. Overall, our data indicate that small soil animals have distinct biogeographical distributions and provide unique evidence of the link between above-ground and below-ground biodiversity at a global scale.
167 citations
TL;DR: Research demonstrates that via a short circuit in the terrestrial nitrogen cycle, Antarctic hair grass acquires soil nitrogen more efficiently than competing mosses, which may explain its success in a warming maritime Antarctic.
Abstract: Nitrogen availability is frequently a key factor limiting plant growth, even when other conditions are favourable. Research demonstrates that via a short circuit in the terrestrial nitrogen cycle, Antarctic hair grass acquires soil nitrogen more efficiently than competing mosses, which may explain its success in a warming maritime Antarctic.
161 citations
TL;DR: The results suggest that AMF abundance in soil is more sensitive to changes in plant species diversity per se and plant species composition than are abundances of saprophytic microbes.
Abstract: The abundance of microbes in soil is thought to be strongly influenced by plant productivity rather than by plant species richness per se. However, whether this holds true for different microbial groups and under different soil conditions is unresolved. We tested how plant species richness, identity and biomass influence the abundances of arbuscular mycorrhizal fungi (AMF), saprophytic bacteria and fungi, and actinomycetes, in model plant communities in soil of low and high fertility using phospholipid fatty acid analysis. Abundances of saprophytic fungi and bacteria were driven by larger plant biomass in high diversity treatments. In contrast, increased AMF abundance with larger plant species richness was not explained by plant biomass, but responded to plant species identity and was stimulated by Anthoxantum odoratum. Our results indicate that the abundance of saprophytic soil microbes is influenced more by resource quantity, as driven by plant production, while AMF respond more strongly to resource composition, driven by variation in plant species richness and identity. This suggests that AMF abundance in soil is more sensitive to changes in plant species diversity per se and plant species composition than are abundances of saprophytic microbes.
139 citations
TL;DR: In this paper, the Park Grass Experiment at Rothamsted (UK) was used to investigate the long-term effects of liming on soil organic carbon (Corg) sequestration.
Abstract: The application of calcium- and magnesium-rich materials to soil, known as liming, has long been a foundation of many agro-ecosystems worldwide because of its role in counteracting soil acidity. Although liming contributes to increased rates of respiration from soil thereby potentially reducing soils ability to act as a CO2 sink, the long-term effects of liming on soil organic carbon (Corg) sequestration are largely unknown. Here, using data spanning 129 years of the Park Grass Experiment at Rothamsted (UK), we show net Corg sequestration measured in the 0–23cm layer at different time intervals since 1876 was 2–20 times greater in limed than in unlimed soils. The main cause of this large Corg accrual was greater biological activity in limed soils, which despite increasing soil respiration rates, led to plant C inputs being processed and incorporated into resistant soil organo-mineral pools. Limed organo-mineral soils showed: (1) greater Corg content for similar plant productivity levels (i.e. hay yields); (2) higher 14C incorporation after 1950s atomic bomb testing and (3) lower C:N ratios than unlimed organo-mineral soils, which also indicate higher microbial processing of plant C. Our results show that greater Corg sequestration in limed soils strongly reduced the global warming potential of long-term liming to permanent grassland suggesting the net contribution of agricultural liming to global warming could be lower than previously estimated. Our study demonstrates that liming might prove to be an effective mitigation strategy, especially because liming applications can be associated with a reduced use of nitrogen fertilizer which is a key cause for increased greenhouse gas emissions from agro-ecosystems.
130 citations
TL;DR: It is concluded that wheat is able to utilise L-peptide and D-amino acid N at rates comparable to those of N forms of acknowledged importance, namely L-aminos acids and inorganic N.
Abstract: Nitrogen is a key regulator of primary productivity in many terrestrial ecosystems. Historically, only inorganic N (NH4+ and NO3-) and L-amino acids have been considered to be important to the N nutrition of terrestrial plants. However, amino acids are also present in soil as small peptides and in D-enantiomeric form. We compared the uptake and assimilation of N as free amino acid and short homopeptide in both L- and D-enantiomeric forms. Sterile roots of wheat (Triticum aestivum L.) plants were exposed to solutions containing either 14C-labelled L-alanine, D-alanine, L-trialanine or D-trialanine at a concentration likely to be found in soil solution (10 µM). Over 5 h, plants took up L-alanine, D-alanine and L-trialanine at rates of 0.9±0.3, 0.3±0.06 and 0.3±0.04 µmol g−1 root DW h−1, respectively. The rate of N uptake as L-trialanine was the same as that as L-alanine. Plants lost ca.60% of amino acid C taken up in respiration, regardless of the enantiomeric form, but more (ca.80%) of the L-trialanine C than amino acid C was respired. When supplied in solutions of mixed N form, N uptake as D-alanine was ca.5-fold faster than as NO3-, but slower than as L-alanine, L-trialanine and NH4+. Plants showed a limited capacity to take up D-trialanine (0.04±0.03 µmol g−1 root DW h−1), but did not appear to be able to metabolise it. We conclude that wheat is able to utilise L-peptide and D-amino acid N at rates comparable to those of N forms of acknowledged importance, namely L-amino acids and inorganic N. This is true even when solutes are supplied at realistic soil concentrations and when other forms of N are available. We suggest that it may be necessary to reconsider which forms of soil N are important in the terrestrial N cycle.
110 citations
TL;DR: The findings suggest that plant diversity restoration management may not directly affect the C assimilation or retention by individual plant taxa or groups of soil microbes, but it can impact on the fate of recent C by changing their relative abundances in the plant-soil system.
Abstract: . Plant-soil interactions are central to short-term carbon (C) cycling through the rapid transfer of recently assimilated C from plant roots to soil biota. In grassland ecosystems, changes in C cycling are likely to be influenced by land use and management that changes vegetation and the associated soil microbial communities. Here we tested whether changes in grassland vegetation composition resulting from management for plant diversity influences short-term rates of C assimilation and transfer from plants to soil microbes. To do this, we used an in situ 13C-CO2 pulse-labelling approach to measure differential C uptake among different plant species and the transfer of the plant-derived 13C to key groups of soil microbiota across selected treatments of a long-term plant diversity grassland restoration experiment. Results showed that plant taxa differed markedly in the rate of 13C assimilation and concentration: uptake was greatest and 13C concentration declined fastest in Ranunculus repens, and assimilation was least and 13C signature remained longest in mosses. Incorporation of recent plant-derived 13C was maximal in all microbial phosopholipid fatty acid (PLFA) markers at 24 h after labelling. The greatest incorporation of 13C was in the PLFA 16:1ω5, a marker for arbuscular mycorrhizal fungi (AMF), while after 1 week most 13C was retained in the PLFA18:2ω6,9 which is indicative of assimilation of plant-derived 13C by saprophytic fungi. Our results of 13C assimilation and transfer within plant species and soil microbes were consistent across management treatments. Overall, our findings suggest that plant diversity restoration management may not directly affect the C assimilation or retention of C by individual plant taxa or groups of soil microbes, it can impact on the fate of recent C by changing their relative abundances in the plant-soil system. Moreover, across all treatments we found that plant-derived C is rapidly transferred specifically to AMF and decomposer fungi, indicating their consistent key role in the cycling of recent plant derived C.
96 citations
TL;DR: In this paper, seasonal changes of dissolved organic carbon (DOC) and nitrogen (DON) concentrations within four molecular weight (MW) size fractions across an altitudinal gradient (from lowland to montane systems), and quantified individual amino acids and amino acid constituents of oligopeptidic-N, as well as nitrate and ammonium.
Abstract: Understanding the fate and turnover of the pools that comprise dissolved organic nitrogen (DON) in soil is key to determining its role in ecosystem functioning. We investigated seasonal changes of dissolved organic carbon (DOC) and nitrogen (DON) concentrations within four molecular weight (MW) size fractions across an altitudinal gradient (from lowland to montane systems), and quantified individual amino acids and amino acid constituents of oligopeptidic-N, as well as nitrate and ammonium. We tested two ideas: first, that DON is more abundant than DIN in low-productivity relative to high-productivity grassland ecosystems; and second, that the abundance of peptides and amino acids is likewise greater in low- than high-productivity grassland. The most productive site had a history of inorganic fertiliser application, and hence in this site alone DIN was more abundant than DON. Plant productivity varied 3-fold between the other sites, and DON was generally at higher concentrations in the sites of lower productivity both in absolute terms as well as relative to DIN, with a large increase observed in spring. The fraction containing the highest concentration of the DON had a MW of >100 kDa, and in summer and autumn this fraction was more abundant at the lowest productivity site. We conclude that relationships between the abundance of DON relative to DIN and ecosystem productivity is dependent on season, and hence more complex than previously suggested, and that peptides are a dynamic and potentially nutritionally significant component of DON.
TL;DR: In this article, the authors used 14C-labeled L-alanine, L-dialanine, and L-trialanine in a series of incubation experiments to investigate peptide utilization rates by soil microbes.
Abstract: [1] Proteinaceous and peptidic nitrogen is a potential direct nutrient source for both plants and microbes in the soil, without prior degradation to amino acids and mineralization. We used a series of five sites along an elevation gradient from 15 m a.s.l. to 710 m a.s.l. along which primary productivity decreases to investigate peptide utilization rates by soil microbes. Using 14C-labeled L-alanine, L-dialanine, and L-trialanine in a series of incubation experiments, we show that peptides are directly and rapidly assimilated by soil microbes, and that they are utilized for both biomass production and respiration. Alanine, dialanine, and trialanine were mineralized rapidly by soil microbes from the five sites along the gradient. Across all five sites, dialanine and trialanine were mineralized faster than alanine. In competition experiments, a 100-fold excess of alanine had no effect on the rate of trialanine mineralization in four of the five sites, and the same excess of trialanine had no effect on alanine mineralization. This is indicative of uptake of the intact peptide by the soil microbial community. Our findings have implications for understanding terrestrial nitrogen cycling because they point to a short-circuit whereby large peptides and proteins need only be extracellularly cleaved to short chain length peptides before direct assimilation by microbes.
TL;DR: Exclusion of ants had multitrophic effects on a microbe-nematode soil food web with three consumer trophic levels and after six years promoted the bacterial-based relative to the fungal-based energy channel in this food web.
Abstract: Despite their ubiquity, the role of ants in driving ecosystem processes both aboveground and belowground has been seldom explored, except within the nest. During 1995 we established 16 ant exclusion plots of approximately 1.1 x 1.1 m, together with paired control plots, in the understory layer of a boreal forest ecosystem in northern Sweden that supports high densities of the mound-forming ant Formica aquilonia, a red wood ant species of the Formica rufa group. Aboveground and belowground measurements were then made on destructively sampled subplots in 2001 and 2008, i.e., 6 and 13 years after set-up. While ant exclusion had no effect on total understory plant biomass, it did greatly increase the relative contribution of herbaceous species, most likely through preventing ants from removing their seeds. This in turn led to higher quality resources entering the belowground subsystem, which in turn stimulated soil microbial biomass and activity and the rates of loss of mass and carbon (C) and nitrogen (N) from litter in litterbags placed in the plots. This was accompanied by losses of approximately 15% of N and C stored in the humus on a per area basis. Ant exclusion also had some effects on foliar stable isotope ratios for both C and N, most probably as a consequence of greater soil fertility. Further, exclusion of ants had multitrophic effects on a microbe-nematode soil food web with three consumer trophic levels and after six years promoted the bacterial-based relative to the fungal-based energy channel in this food web. Our results point to a major role of red wood ants in determining forest floor vegetation and thereby exerting wide-ranging effects on belowground properties and processes. Given that the boreal forest occupies 11% of the Earth's terrestrial surface and stores more C than any other forest biome, our results suggest that this role of ants could potentially be of widespread significance for biogeochemical nutrient cycling, soil nutrient capital, and sequestration of belowground carbon.
TL;DR: Understanding of the mechanisms involved in the transfer of carbon through roots of plants to the soil and its consequences for ecosystem carbon cycling and the potential to exploit plant root traits and soil microbial processes that favor soil carbon sequestration are improved.
Abstract: Evidence is mounting to suggest that the transfer of carbon through roots of plants to the soil plays a primary role in regulating ecosystem responses to climate change and its mitigation. Future research is needed to improve understanding of the mechanisms involved in this phenomenon, its consequences for ecosystem carbon cycling, and the potential to exploit plant root traits and soil microbial processes that favor soil carbon sequestration.
TL;DR: In three contrasting tundra soils formed under the grass, moss or lichen-dominated primary producer communities of Signy Island in the South Orkney Islands, intense competition exists in soil microbial communities for the capture of both peptides and amino acids produced from protein breakdown.
Abstract: Most nitrogen (N) enters many Arctic and Antarctic soil ecosystems as protein. Soils in these polar environments frequently contain large stocks of proteinaceous organic matter, which has decomposed slowly due to low temperatures. In addition to proteins, considerable quantities of D-amino acids and their peptides enter soil from bacteria and lengthy residence times can lead to racemisation of L-amino acids in stored proteins. It has been predicted that climate warming in polar environments will lead to increased rates of soil organic N turnover (i.e. amino acids and peptides of both enantiomers). However, our understanding of organic N breakdown in these soils is very limited. To address this, we tested the influence of chain length and enantiomeric composition on the rate of breakdown of amino acids and peptides in three contrasting tundra soils formed under the grass, moss or lichen-dominated primary producer communities of Signy Island in the South Orkney Islands. Both D- and L-enantiomers of the amino acid monomer were rapidly mineralized to CO(2) at rates in line with those found for L-amino acids in many other terrestrial ecosystems. In all three soils, L-peptides were decomposed faster than their amino acid monomer, suggesting a different route of microbial assimilation and catabolism. D-peptides followed the same mineralization pattern as L-peptides in the two contrasting soils under grass and lichens, but underwent relatively slow decomposition in the soil underneath moss, which was similar to the soil under the grass. We conclude that the decomposition of peptides of L-amino acids may be widely conserved amongst soil microorganisms, whereas the decomposition of peptides of D-amino acids may be altered by subtle differences between soils. We further conclude that intense competition exists in soil microbial communities for the capture of both peptides and amino acids produced from protein breakdown. (C) 2011 Elsevier Ltd. All rights reserved.
TL;DR: In this paper, the authors used data from a well-studied N-limited grassland to address the relative effects of six plant and soil variables on net and on gross rates of soil N mineralization.
Abstract: Despite the topic of soil nitrogen (N) mineralization being well-studied, very few studies have addressed the relative contribution of different plant and soil variables in influencing soil N mineralization rates, and thus the supply of inorganic N to plants. Here, we used data from a well-studied N-limited grassland to address the relative effects of six plant and soil variables on net and on gross rates of soil N mineralization. We also addressed whether plant effects on soil N mineralization were mediated by changes in C and N concentrations of multiple soil organic matter (SOM) fractions. Regression analyses show that key plant traits (i.e., plant C:N ratios and total root mass) were more important than total C and N concentrations of bulk soil in influencing N mineralization. This was mainly because plant traits influenced the C and N concentration (and C:N ratios) of different SOM fractions, which in turn were significantly associated with changes in net and gross N mineralization. In particular, C:N ratios of a labile soil fraction were negatively related to net soil N mineralization rates, whereas total soil C and N concentrations of more recalcitrant fractions were positively related to gross N mineralization. Our study suggests that changes in belowground N-cycling can be better predicted by simultaneously addressing how plant C:N ratios and root mass affect the composition and distribution of different SOM pools in N-limited grassland systems.
TL;DR: In this article, a spatial and temporal gradient in nutrient availability and an associated shift in microbial community structure with increasing distance and age of a single tree was found, indicating a strong influence of trees on spatial patterns of microbial biomass and community structure.
Abstract: Linkages between forest dynamics and ecosystem processes are poorly understood and this limits our ability to adequately estimate future changes in forest ecosystems due to human-induced global change. In particular at the single tree level, our understanding of temporal and spatial changes of belowground properties during forest succession is limited. Thus, our aim was to test whether we find a spatial and temporal gradient in nutrient availability and an associated shift in microbial community structure with increasing distance and age of single trees. We found that inorganic nitrogen ( NO 3 − , NH 4 + ) was less available below the crown of single trees, while soluble organic carbon (DOC) was much more abundant, in particular in the inner zone of influence, i.e. close to the stem. The fungal:bacterial PLFA ratio was greater while microbial biomass carbon (MicC) was lower below the tree crown, indicating a strong influence of trees on spatial patterns of microbial biomass and community structure. Moreover, the positive correlation between MicC and total extractable N, and the negative correlation between fungal:bacterial biomass and δ15N, suggested that the microbial biomass was N limited below the tree crown and as a consequence nutrient cycling was presumably decelerated compared to open conditions. We also found a temporal pattern of increasing surface soil C and N content with increasing tree age (up to 250 years), underlining the significant role of single trees in creating spatial and temporal heterogeneity in forests.
TL;DR: The results suggest that plant and soil responses to defoliation are reasonably consistent across a broad range of grass species, with only subtle inter-specific differences among species.
Abstract: The overall aim of this study was to test for inter-species variation in plant and soil responses to defoliation among a broad range of temperate grass species and life-history strategies. We used a microcosm experiment where a range of grass species differing in life history traits were subjected to different intensities of defoliation, and a range of aboveground and belowground plant and soil responses were measured. All plant attributes, including accumulated shoot biomass, root biomass and root length, showed a strong negative response to defoliation, although plant species exhibited subtle differences in the way that they responded to increased severity of defoliation. Defoliation also exerted a strong influence on soil properties, decreasing soil microbial carbon (C) and the soil microbial C:nitrogen (N) ratio, and increasing inorganic N availability and potential N mineralisation across all species. Despite the wide range in life history strategies, plant species did not differ in their influence on most of the soil variables, except for the rate of nitrate mineralisation, which was lowest under plant species that displayed the least relative detrimental responses to defoliation. Collectively, our results suggest that plant and soil responses to defoliation are reasonably consistent across a broad range of grass species, with only subtle inter-specific differences among species.
TL;DR: In this article, the authors highlight the importance of N in forest ecosystem C-sequestration and identify the mechanisms involved, and propose that a better mechanistic understanding on interactions between plant and microbial communities should be explicitly considered for the development of effective policy strategies for forest ecosystem carbon sequestration.
TL;DR: In this article, a method for determining the natural abundance radiocarbon (14C) content of soil microbial biomass (SMB) based on existing fumigation-extraction procedures was presented.
Abstract: We present a method for determining the natural abundance radiocarbon (14C) content of soil microbial biomass (SMB) based on existing fumigation–extraction procedures. We applied the technique to soils from the foreland of the Odenwinkelkees glacier in the Austrian Alps, which has a well-characterised chronosequence of soils at different stages of development. Across the chronosequence, SMB contained post-bomb levels of 14C, suggesting it was substantially composed of carbon that had been fixed since the 1960s. Comparison of our results with previous findings from the same site showed that at most stages in the sequence the SMB had a similar 14C content to the bulk soil organic matter (SOM). However, soil respired CO2 was 14C-depleted relative to SMB, indicating that at least a component of the microbial community was mineralising some older carbon. In the most recently exposed soils, SMB was 14C-enriched compared to both soil respiration and SOM, suggesting that a small component of the microbial biomass that utilises older carbon contributes disproportionately more to the CO2 efflux. Although other interpretations are possible, this explanation is consistent with the notion that early on in the succession a large proportion of the microbial biomass is dormant.
01 Jan 2011
Abstract: or much of history, few things have mattered more to humans than their relationship with soil. Not only does soil sustain the production of crops for human consumption, but it also plays a primary role in all global biogeochemical cycles and is key to the provision of ecosystem services, such as nutrient cycling and carbon sequestration. Soil is also highly susceptible to degradation, and degraded soils now cover 15-17% of the Earth's surface. As a result, one of the most important challenges facing agriculture is the need to develop sustainable farming systems that restore and enhance the ability of soils to deliver ecosystem services, such as carbon sequestration and efficient nutrient cycling, whilst also maintaining viable food production for the burgeoning world population. Our research in the Lancaster Environment Centre (LEC), Lancaster University, is aimed at this challenge. Not only do we seek to advance understanding of the mechanisms involved in the delivery of ecosystem services from soil, but we also aim to use this knowledge to develop sustainable management options for farming systems. Here we describe three projects at Lancaster that are tackling these goals. The first project focuses on grasslands , which cover a large proportion of the UK and European land surface and form the backbone of the livestock industry. Moreover, grasslands hold 32.4% of the UK soil carbon stock, amounting to 0.55 Pg carbon or 2.2 Pg carbon dioxide equivalents (Countryside Survey 2007). A major goal of this research is to investigate the potential for grasslands to meet multiple objectives of soil carbon sequestration and biodiversity conservation , the latter being a key aim of European agri-environmental policy. We are gaining evidence that high diversity grasslands could have the potential to increase soil carbon sequestration from a number of studies. First, as part of a national survey of 180 grasslands, funded by Defra, we found that the carbon concentration of surface soil was significantly greater in traditionally managed, species-rich grassland than in intensively managed, species-poor counterparts. Second, studies of experimental grasslands, funded by the BBSRC, showed that the uptake (ie. photosynthesis) and allocation of carbon below ground to roots and soil fungi increased with increasing species-richness, which was primarily due to the presence of certain plant species, especially legumes, in high diversity grasslands. Third, in a long-term field experiment in the Yorkshire Dales, we have found that when management treatments that best increased plant species diversity …