The Experts below are selected from a list of 1698 Experts worldwide ranked by ideXlab platform
Chao Liang - One of the best experts on this subject based on the ideXlab platform.
-
the accumulation of microbial Necromass carbon from litter to mineral soil and its contribution to soil organic carbon sequestration
Catena, 2021Co-Authors: Baorong Wang, Chao Liang, Hongjia Yao, Env YangAbstract:Abstract Microbial Necromass plays an essential role in soil organic carbon (SOC) accumulation. Nevertheless, how microbial Necromass carbon (C) concentrations and their contributions to SOC sequestration change from litter to mineral soil and what factors influence its accumulation remain poorly understood. To address this knowledge gap, we performed a field experiment to investigate the compositional distribution characteristics of microbial Necromass C and its contributions to SOC sequestration in an oak forest (Quercus wutaishanica) litter-mineral soil profile of the Chinese Loess Plateau. The present study estimated the microbial Necromass C concentrations based on the microbial cell wall's biomarker amino sugars. Our results demonstrated that microbial Necromass C increased from the Oi1 to Oa layers but decreased from the Ah1 to AB horizons. The highest accumulation of microbial Necromass C was found at the litter-mineral soil interface (i.e., total microbial Necromass in the Oa layer was 39.5 Mg ha−1, and Ah1 was 22.8 Mg ha−1). The contribution of total microbial Necromass C to SOC increased from Oi1 to Ah2. Specifically, the total microbial Necromass C accounted for 40.7%, 47.7%, and 37.0% of the average bulk SOC in the Ah1, Ah2, and AB horizons of the oak forest mineral soil, respectively. The ratio of fungal to bacterial Necromass C decreased from litter to mineral soil, indicating that the relatively higher bacterial Necromass C increasingly accumulated in the deeper litter layers and upper mineral soil horizons. Fungal and bacterial Necromass C increased with increasing labile organic C, nitrogen (N), and labile inorganic phosphorus (P), suggesting that higher easily accessible soluble nutrients lead to higher microbial biomass levels, which in turn lead to higher microbial Necromass accumulation. Overall, our findings suggested that microbial demand for C or N influences the quantity of soluble nutrients and further lead to changes in microbial Necromass C decomposition/accumulation.
-
depth dependent drivers of soil microbial Necromass carbon across tibetan alpine grasslands
Global Change Biology, 2021Co-Authors: Kai Fang, Chao Liang, Leiyi Chen, Xuehui Feng, Shuqi Qin, Dan Kou, Yuanhe YangAbstract:Microbial Necromass carbon (C) has been considered an important contributor to persistent soil C pool. However, there still lacks large-scale systematic observations on microbial Necromass C in different soil layers, particularly for alpine ecosystems. Besides, it is still unclear whether the relative importance of biotic and abiotic variables such as plant C input and mineral properties in regulating microbial Necromass C would change with soil depth. Based on the combination of large-scale sampling along a ~2200 km transect across Tibetan alpine grasslands and biomarker analysis, together with a global data synthesis across grassland ecosystems, we observed a relatively low proportion of microbial-derived C in Tibetan alpine grasslands compared to global grasslands (topsoil: 45.4% vs. 58.1%; subsoil: 41.7% vs. 53.7%). We also found that major determinants of microbial Necromass C depended on soil depth. In topsoil, both plant C input and mineral protection exerted dominant effects on microbial Necromass C. However, in subsoil, the physico-chemical protection provided by soil clay particles, iron-aluminum oxides, and exchangeable calcium dominantly facilitated the preservation of microbial Necromass C. The differential drivers over microbial Necromass C between soil depths should be considered in Earth system models for accurately forecasting soil C dynamics and its potential feedback to global warming.
-
revisiting the quantitative contribution of microbial Necromass to soil carbon pool stoichiometric control by microbes and soil
Soil Biology & Biochemistry, 2021Co-Authors: Fangbo Deng, Chao LiangAbstract:Abstract Quantitative assessments of soil microbial Necromass improve our knowledge of soil carbon (C) sequestration, which is vital for addressing climate change and food security. Here, we revisit the quantitative contribution of microbial Necromass to soil organic C (SOC) pool by using an optimized strategy that considers the stoichiometric differences of microbes and the full range of the microbial Necromass proportion in soil nitrogen pool. We derive a more applicable estimate of the microbial Necromass contribution to SOC pool, reporting a narrower range (24%–60%) compared with those in recent publications. We further find that the potential contribution of microbial Necromass to SOC pool is controlled by the stoichiometry (C/N ratio) of microbes and soil. We suggest soil C sequestration strategy by increasing microbial Necromass should well be exploited to improve soil N availability and use microbial species associated with high biomass C/N ratio to boost C accrual.
-
microbial Necromass as the source of soil organic carbon in global ecosystems
Soil Biology & Biochemistry, 2021Co-Authors: Baorong Wang, Chao Liang, Yang Liu, Yakov KuzyakovAbstract:Abstract Despite the recognized importance of the contribution of microbial Necromass to soil organic carbon (SOC) sequestration, at a global scale, there has been no quantification for cropland, grassland, and forest ecosystems. To address this knowledge gap, the contents of fungal and bacterial Necromass were estimated based on glucosamine and muramic acid contents in cropland (986 samples), grassland (278 samples), and forest (452 samples) soils. On an average, microbial Necromass C contributed 51%, 47%, and 35% to the SOC in cropland, grassland, and forest soils, respectively, in the first 20 cm of topsoil. The contribution of microbial Necromass to SOC increased with soil depth in grasslands (from 47% to 54%) and forests (from 34% to 44%), while it decreased in croplands (from 51% to 24%). The microbial Necromass accumulation coefficient (the ratio between Necromass and living microbial biomass C) was higher in soil from croplands (41) and grasslands (33) than in forest (20) soils. These results suggest that the turnover of living microbial biomass is faster in grassland and cropland soils than in forest soils, where the latter contains more partially decomposed plant residues. Fungal Necromass C (>65% of total Necromass) had consistently higher contributions to SOC than bacterial Necromass C (32–36%) in all soils due to i) a larger living fungal biomass than bacterial biomass, and ii) fungal cell compounds being decomposed slowly and, thus able to persist longer in soil. The ratio of fungal:bacterial Necromass C increased from 2.4 to 2.9 in the order of croplands
-
rice rhizodeposition promotes the build up of organic carbon in soil via fungal Necromass
Soil Biology & Biochemistry, 2021Co-Authors: Yu Luo, Chao Liang, Yakov Kuzyakov, Mouliang Xiao, Hongzhao Yuan, Zhenke Zhu, Caixian TangAbstract:Abstract Rice rhizodeposition plays an important role in carbon sequestration in paddy soils. However, the pathways through which rice rhizodeposits contribute to soil organic C (SOC) formation are poorly understood because of specific paddy soil conditions. Furthermore, microbial Necromass has been largely ignored in studies examining the contribution of rhizodeposits to C sequestration during plant growth. To evaluate the contribution of microbial Necromass to SOC formation via rhizodeposition, rice (Oryza sativa L.) plants were continuously labeled with 13CO2 for 38 days under ambient (aCO2, 400 μL L−1) or elevated CO2 (eCO2, 800 μL L−1) in a paddy field at two levels of N fertilization. The distributions of photosynthetic-13C in the shoots and roots, microbial communities, and SOC fractions were quantified. eCO2 increased plant growth and, consequently, the total 13C incorporated into the shoots, roots, and SOC compared to aCO2, while N fertilization (100 kg N ha−1) decreased root biomass and rhizodeposits in the soil and microbial pools, including living biomass (phospholipid fatty acids, PLFA) and microbial Necromass (amino sugars). Rhizodeposits were initially immobilized mainly by bacteria and preferentially recovered in fungal Necromass (glucosamine). While 13C incorporation into PLFAs was slightly increased during plant growth, 13C in microbial Necromass increased greatly between the tillering and booting stages. Fungal Necromass, which is less decomposable compared to bacterial residues, was the largest contributor to C sequestration with rhizodeposits via the mineral-associated SOC fraction, particularly under elevated CO2 without N fertilization. This study reveals the significance of the C pathways from rhizodeposits through fungal Necromass and organo-mineral associations for the build up of SOC in paddy fields.
Peter G Kennedy - One of the best experts on this subject based on the ideXlab platform.
-
warming drives a hummockification of microbial communities associated with decomposing mycorrhizal fungal Necromass in peatlands
New Phytologist, 2021Co-Authors: Francois Maillard, Christopher W Fernandez, Katherine Heckman, Sunil Mundra, Randall K Kolka, Havard Kauserud, Peter G KennedyAbstract:Dead fungal mycelium (Necromass) represents a critical component of soil carbon (C) and nutrient cycles. Assessing how the microbial communities associated with decomposing fungal Necromass change as global temperatures rise will help in determining how these belowground organic matter inputs contribute to ecosystem responses. In this study, we characterized the structure of bacterial and fungal communities associated with multiple types of decaying mycorrhizal fungal Necromass incubated within mesh bags across a 9°C whole ecosystem temperature enhancement in a boreal peatland. We found major taxonomic and functional shifts in the microbial communities present on decaying mycorrhizal fungal Necromass in response to warming. These changes were most pronounced in hollow microsites, which showed convergence towards the Necromass-associated microbial communities present in unwarmed hummocks. We also observed a high colonization of ericoid mycorrhizal fungal Necromass by fungi from the same genera as the Necromass. These results indicate that microbial communities associated with mycorrhizal fungal Necromass decomposition are likely to change significantly with future climate warming, which may have strong impacts on soil biogeochemical cycles in peatlands. Additionally, the high enrichment of congeneric fungal decomposers on ericoid mycorrhizal Necromass may help to explain the increase in ericoid shrub dominance in warming peatlands.
-
distinct carbon fractions drive a generalisable two pool model of fungal Necromass decomposition
Functional Ecology, 2021Co-Authors: Craig R See, Peter G Kennedy, Christopher W Fernandez, Katherine Heckman, Anna M Conley, Lang C Delancey, Sarah E HobbieAbstract:Fungi represent a rapidly cycling pool of carbon (C) and nitrogen (N) in soils. Understanding of how this pool impacts soil nutrient availability and organic matter fluxes is hindered by uncertainty regarding the dynamics and drivers of fungal Necromass decomposition. Here we assessed the generality of common models for predicting mass loss during fungal Necromass decomposition and linked the resulting parameters to Necromass substrate chemistry. We decomposed 28 different types of fungal Necromass in laboratory microcosms over a 90-day period, measuring mass loss on all types, and N release on a subset of types. We characterised the initial chemistry of each Necromass type using: (a) fibre analysis methods commonly used for plant tissues, (b) initial melanin and nitrogen (N) concentrations and (c) Fourier transform infrared (FTIR) spectroscopy to assess the presence of bonds associated with common biomolecules. We found universal support for an asymptotic model of decomposition, which assumes that fungal Necromass consists of an exponentially decomposing 'fast' pool, and a 'slow' pool that decomposes at a rate approaching zero. The strongest predictor of the fast pool decay rate (k) was the proportion of cell soluble components, though initial N concentration also predicted k, albeit more weakly. The size of the slow pool was best predicted by the acid non-hydrolysable fraction, which was positively correlated with melanin-associated aromatics. Nitrogen dynamics varied by Necromass type, ranging from net N release to net immobilisation. The maximum quantity of N immobilised was inversely related to cell soluble contents and k, as positively related to FTIR spectra associated with cell wall polysaccharides. Collectively, our results indicate that the decomposition of fungal Necromass in soils can be described as having two distinct stages that are driven by different components of substrate C chemistry, with implications for rates of N availability and organic matter accumulation in soils.
-
root presence modifies the long term decomposition dynamics of fungal Necromass and the associated microbial communities in a boreal forest
Molecular Ecology, 2021Co-Authors: Francois Maillard, Peter G Kennedy, Bartosz Adamczyk, Jussi Heinonsalo, Marc BueeAbstract:Recent studies have highlighted that dead fungal mycelium represents an important fraction of soil carbon (C) and nitrogen (N) inputs and stocks. Consequently, identifying the microbial communities and the ecological factors that govern the decomposition of fungal Necromass will provide critical insight into how fungal organic matter (OM) affects forest soil C and nutrient cycles. Here, we examined the microbial communities colonising fungal Necromass during a multiyear decomposition experiment in a boreal forest, which included incubation bags with different mesh sizes to manipulate both plant root and microbial decomposer group access. Necromass-associated bacterial and fungal communities were taxonomically and functionally rich throughout the 30 months of incubation, with increasing abundances of oligotrophic bacteria and root-associated fungi (i.e., ectomycorrhizal, ericoid mycorrhizal and endophytic fungi) in the late stages of decomposition in the mesh bags to which they had access. Necromass-associated β-glucosidase activity was highest at 6 months, while leucine aminopeptidase peptidase was highest at 18 months. Based on an asymptotic decomposition model, root presence was associated with an initial faster rate of fungal Necromass decomposition, but resulted in higher amounts of fungal Necromass retained at later sampling times. Collectively, these results indicate that microbial community composition and enzyme activities on decomposing fungal Necromass remain dynamic years after initial input, and that roots and their associated fungal symbionts result in the slowing of microbial Necromass turnover with time.
-
substrate quality drives fungal Necromass decay and decomposer community structure under contrasting vegetation types
Journal of Ecology, 2020Co-Authors: Katilyn V Beidler, Francois Maillard, Richard P Phillips, Erin Andrews, Ryan M Mushinski, Peter G KennedyAbstract:1.Fungal mycelium is increasingly recognized as a central component of soil biogeochemical cycling, yet our current understanding of the ecological controls on fungal Necromass decomposition is limited to single sites and vegetation types. 2.By deploying common fungal Necromass substrates in a temperate oak savanna and hardwood forest in the midwestern USA, we assessed the generality of the rate at which high‐ and low‐quality fungal Necromass decomposes; further, we investigated how the decomposer ‘necrobiome’ varies both across and within sites under vegetation types dominated by either arbuscular or ectomycorrhizal plants. 3.The effects of Necromass quality on decay rate were robust to site and vegetation type differences, with high‐quality fungal Necromass decomposing, on average, 2.5 times faster during the initial stages of decay. Across vegetation types, bacterial and fungal communities present on decaying Necromass differed from bulk soil microbial communities and were influenced by Necromass quality. Moulds, yeasts and copiotrophic bacteria consistently dominated the necrobiome of high‐quality fungal substrates. 4.Synthesis. We show that regardless of differences in decay environments, high‐quality fungal substrates decompose faster and support different types of decomposer micro‐organisms when compared with low‐quality fungal tissues. These findings help to refine our theoretical understanding of the dominant factors affecting fast cycling components of soil organic matter and the microbial communities associated with rapid decay.
-
rapid changes in the chemical composition of degrading ectomycorrhizal fungal Necromass
Fungal Ecology, 2020Co-Authors: Maeve E Ryan, Kathryn M Schreiner, Jenna T Swenson, Joseph Gagne, Peter G KennedyAbstract:Abstract Characterizing the chemical changes in fungal Necromass as it degrades, particularly over short time intervals (days to weeks), is critical to clearly understanding how this organic matter source contributes to various belowground carbon and nutrient pools. Using a range of chemical analyses, we assessed the degradation of four types of ectomycorrhizal fungal Necromass from three species differing in biochemical composition. Samples were buried in a forest in Minnesota, USA and harvested at eight time points over a 90-day incubation period (1, 2, 4, 7, 14, 28, 60, 90 days). Three of the Necromass types lost greater than 50% of their initial mass in the first seven days, but mass loss plateaued for all four types at later harvests, and after 90 days, none of the samples were completely degraded. Relative to undegraded Necromass, degraded Necromass consistently contained a lower relative abundance of aliphatic compounds and a higher relative abundance of carbohydrates, sterols, and aromatic compounds. For three of the four Necromass types, nitrogen content was lower after 90 days of degradation and FTIR spectra revealed distinct peaks broadening from day 0 to day 90. While melanin content significantly slowed degradation within species, differences in degradation rates across species were more closely aligned with initial nitrogen content. Collectively, our results indicate that the rapid mass loss of dead fungal mycelium is accompanied by a wide range of changes in Necromass chemistry, likely contributing to both short-term soil nutrient and longer-term carbon pools.
Yakov Kuzyakov - One of the best experts on this subject based on the ideXlab platform.
-
microbial Necromass as the source of soil organic carbon in global ecosystems
Soil Biology & Biochemistry, 2021Co-Authors: Baorong Wang, Chao Liang, Yang Liu, Yakov KuzyakovAbstract:Abstract Despite the recognized importance of the contribution of microbial Necromass to soil organic carbon (SOC) sequestration, at a global scale, there has been no quantification for cropland, grassland, and forest ecosystems. To address this knowledge gap, the contents of fungal and bacterial Necromass were estimated based on glucosamine and muramic acid contents in cropland (986 samples), grassland (278 samples), and forest (452 samples) soils. On an average, microbial Necromass C contributed 51%, 47%, and 35% to the SOC in cropland, grassland, and forest soils, respectively, in the first 20 cm of topsoil. The contribution of microbial Necromass to SOC increased with soil depth in grasslands (from 47% to 54%) and forests (from 34% to 44%), while it decreased in croplands (from 51% to 24%). The microbial Necromass accumulation coefficient (the ratio between Necromass and living microbial biomass C) was higher in soil from croplands (41) and grasslands (33) than in forest (20) soils. These results suggest that the turnover of living microbial biomass is faster in grassland and cropland soils than in forest soils, where the latter contains more partially decomposed plant residues. Fungal Necromass C (>65% of total Necromass) had consistently higher contributions to SOC than bacterial Necromass C (32–36%) in all soils due to i) a larger living fungal biomass than bacterial biomass, and ii) fungal cell compounds being decomposed slowly and, thus able to persist longer in soil. The ratio of fungal:bacterial Necromass C increased from 2.4 to 2.9 in the order of croplands
-
rice rhizodeposition promotes the build up of organic carbon in soil via fungal Necromass
Soil Biology & Biochemistry, 2021Co-Authors: Yu Luo, Chao Liang, Yakov Kuzyakov, Mouliang Xiao, Hongzhao Yuan, Zhenke Zhu, Caixian TangAbstract:Abstract Rice rhizodeposition plays an important role in carbon sequestration in paddy soils. However, the pathways through which rice rhizodeposits contribute to soil organic C (SOC) formation are poorly understood because of specific paddy soil conditions. Furthermore, microbial Necromass has been largely ignored in studies examining the contribution of rhizodeposits to C sequestration during plant growth. To evaluate the contribution of microbial Necromass to SOC formation via rhizodeposition, rice (Oryza sativa L.) plants were continuously labeled with 13CO2 for 38 days under ambient (aCO2, 400 μL L−1) or elevated CO2 (eCO2, 800 μL L−1) in a paddy field at two levels of N fertilization. The distributions of photosynthetic-13C in the shoots and roots, microbial communities, and SOC fractions were quantified. eCO2 increased plant growth and, consequently, the total 13C incorporated into the shoots, roots, and SOC compared to aCO2, while N fertilization (100 kg N ha−1) decreased root biomass and rhizodeposits in the soil and microbial pools, including living biomass (phospholipid fatty acids, PLFA) and microbial Necromass (amino sugars). Rhizodeposits were initially immobilized mainly by bacteria and preferentially recovered in fungal Necromass (glucosamine). While 13C incorporation into PLFAs was slightly increased during plant growth, 13C in microbial Necromass increased greatly between the tillering and booting stages. Fungal Necromass, which is less decomposable compared to bacterial residues, was the largest contributor to C sequestration with rhizodeposits via the mineral-associated SOC fraction, particularly under elevated CO2 without N fertilization. This study reveals the significance of the C pathways from rhizodeposits through fungal Necromass and organo-mineral associations for the build up of SOC in paddy fields.
-
microbial carbon use efficiency biomass turnover and Necromass accumulation in paddy soil depending on fertilization
Agriculture Ecosystems & Environment, 2020Co-Authors: Xiangbi Chen, Yakov Kuzyakov, Yinhang Xia, Zhao Ning, Haiming Tang, Yichao RuiAbstract:Abstract Microbial anabolism relative to catabolism, reflected by the C use efficiency (CUE), determines the fate of C transformation in soil. Understanding how the microbial CUE and microbial Necromass respond to fertilization is crucial for the evaluation of the C sequestration potential in intensively managed paddy soils. We examined the microbial CUE, microbial biomass turnover, and Necromass accumulation in rice rhizosphere and bulk soils subjected to long-term (31 years) fertilizations: no fertilizers (control), mineral fertilizers alone (NPK), mineral fertilizers plus rice straw incorporation (NPK-Straw), and mineral fertilizers combined with a low or a high amount of organic manure (NPK-lowM or NPK-highM). The microbial CUE was determined by 18O incorporation into DNA. Microbial Necromass accumulation was quantified by the biomarker analysis of amino sugars. Rice straw and manure incorporation reduced the microbial CUE in the rhizosphere soil, whereas the CUE remained constant in the bulk soil. CUE was lower in the rhizosphere soil than in the bulk soil due to nutrients uptake and root exudate release by rice plants, leading to a higher C/nutrient ratio in the rhizosphere. Organic inputs strengthened these rhizosphere processes and could thus weaken the relative potential of C sequestration. The microbial CUE decreased with the increase of the available C/N ratio in the rhizosphere but not in the bulk soil. The microbial CUE mainly depended on the respiration in the bulk soil and on the microbial growth in the rhizosphere soil, indicating the divergent microbial utilization of organic substrates between rhizosphere and bulk soils. In both rhizosphere and bulk soils, organic inputs promoted the microbial biomass growth rate and further increased the amount of microbial Necromass by 27–52 % compared with NPK alone, which was highly correlated with the soil organic C pools. Despite enhancing rhizosphere respiration, our findings highlight that rice straw and manure applications increase C sequestration in paddy soils by enhancing the net flux of microbial biomass formation, and consequently promoting Necromass accumulation.
-
carbon and nitrogen recycling from microbial Necromass to cope with c n stoichiometric imbalance by priming
Soil Biology & Biochemistry, 2020Co-Authors: Jun Cui, Yakov Kuzyakov, Zhenke Zhu, Shoulong Liu, Davey L Jones, Olga ShibistovaAbstract:Abstract The impact of increasing amounts of labile C input on priming effects (PE) on soil organic matter (SOM) mineralization remains unclear, particularly under anoxic conditions and under high C input common in microbial hotspots. PE and their mechanisms were investigated by a 60-day incubation of three flooded paddy soils amended with13C-labeled glucose equivalent to 50–500% of microbial biomass C (MBC). PE (14–55% of unamended soil) peaked at moderate glucose addition rates (i.e., 50–300% of MBC). Glucose addition above 300% of MBC suppressed SOM mineralization but intensified microbial N acquisition, which contradicted the common PE mechanism of accelerating SOM decomposition for N-supply (frequently termed as “N mining”). Particularly at glucose input rate higher than 3 g kg−1 (i.e., 300–500% of MBC), mineral N content dropped on day 2 close to zero (1.1–2.5 mg N kg−1) because of microbial N immobilization. To cope with the N limitation, microorganisms greatly increased N-acetyl glucosaminidase and leucine aminopeptidase activities, while SOM decomposition decreased. Several discrete peaks of glucose-derived CO2 (contributing >80% to total CO2) were observed between days 13–30 under high glucose input (300–500% of MBC), concurrently with CH4 peaks. Such CO2 dynamics was distinct from the common exponential decay pattern, implicating the recycling and mineralization of 13C-enriched microbial Necromass driven by glucose addition. Therefore, N recycling from Necromass was hypothesized as a major mechanism to alleviate microbial N deficiency without SOM priming under excess labile C input. Compound-specific 13C-PLFA confirmed the redistribution of glucose-derived C among microbial groups, i.e., Necromass recycling. Following glucose input, more than 4/5 of total 13C-PLFA was in the gram-negative and some non-specific bacteria, suggesting these microorganisms as r-strategists capable of rapidly utilizing the most labile C. However, their 13C-PLFA content decreased by 70% after 60 days, probably as a result of death of these r-strategists. On the contrary, the 13C-PLFA in gram-positive bacteria, actinomycetes and fungi (K-strategists) was initially minimal but increased by 0.5–5 folds between days 2 and 60. Consequently, the Necromass of dead r-strategists provided a high-quality C–N source to the K-strategists. We conclude that under severe C excess, N recycling from Necromass is a much more efficient microbial strategy to cover the acute N demand than N acquisition from the recalcitrant SOM.
-
manure over crop residues increases soil organic matter but decreases microbial Necromass relative contribution in upland ultisols results of a 27 year field experiment
Soil Biology & Biochemistry, 2019Co-Authors: Yongxin Lin, Yakov Kuzyakov, Deyan Liu, Jiafa Luo, Stuart Lindsey, Weijin Wang, Jianbo Fan, Weixin DingAbstract:Abstract Organic fertilizers increase soil organic matter (SOM) stocks, but the underlying processes depend on the fertilizer type and remain largely unknown. To evaluate the predominant C stabilization mechanisms, upland Ultisols subjected to 27 years of mineral and organic fertilization were analyzed for SOM content, aggregate size classes, and amino sugar composition. The long-term field experiment had seven treatments: no fertilization (Control), mineral NPK fertilizers (NPK), NPK plus lime (NPK + Lime), NPK plus peanut straw (NPK + PeanutStraw), NPK plus rice straw (NPK + RiceStraw), NPK plus radish residue (NPK + RadishResidue), and NPK plus pig manure (NPK + PigManure). The 27-year application of mineral fertilizers (NPK and NPK + Lime), NPK + crop residues, and NPK + PigManure increased SOM content by 11.0–13.2%, 16.3–25.3%, and 44.3%, respectively, compared with the Control. The aliphaticity and recalcitrance indices based on 13C nuclear magnetic resonance spectra of organic fertilizers were higher for pig manure than for crop residues. Both indices were closely correlated with SOM content after 27 years, so higher proportions of recalcitrant C in manure facilitated SOM accumulation. NPK + PigManure increased the mass proportion of large macroaggregates 2.9-fold compared with the Control, and reduced the effective diffusion coefficient of oxygen in the soil. Consequently, NPK + PigManure limited the activity and abundance of aerobes and the accessibility of SOM to microorganisms, in turn facilitating SOM accumulation. The application of mineral fertilizers, NPK + crop residues, and NPK + PigManure increased microbial Necromass to 2.85–3.03, 3.21–3.45, and 3.62 g C kg−1, respectively, from 2.63 g C kg−1 in the Control. Compared with crop residues, pig manure did not affect bacterial Necromass but increased fungal Necromass from 2.19 to 2.39 g C kg−1 to 2.58 g C kg−1, which might associate with increased SOM stability. However, the relative contribution of microbial Necromass to SOM was lower under NPK + PigManure than under NPK + crop residues, since more added C was protected in the NPK + PigManure soil. Our results suggest that manure may contribute to SOM accumulation and stabilization in three ways: directly through the input of recalcitrant organic C, indirectly through the stabilization of aggregates and physical protection of C, and to a lesser extent through increasing fungal Necromass.
Christopher W Fernandez - One of the best experts on this subject based on the ideXlab platform.
-
warming drives a hummockification of microbial communities associated with decomposing mycorrhizal fungal Necromass in peatlands
New Phytologist, 2021Co-Authors: Francois Maillard, Christopher W Fernandez, Katherine Heckman, Sunil Mundra, Randall K Kolka, Havard Kauserud, Peter G KennedyAbstract:Dead fungal mycelium (Necromass) represents a critical component of soil carbon (C) and nutrient cycles. Assessing how the microbial communities associated with decomposing fungal Necromass change as global temperatures rise will help in determining how these belowground organic matter inputs contribute to ecosystem responses. In this study, we characterized the structure of bacterial and fungal communities associated with multiple types of decaying mycorrhizal fungal Necromass incubated within mesh bags across a 9°C whole ecosystem temperature enhancement in a boreal peatland. We found major taxonomic and functional shifts in the microbial communities present on decaying mycorrhizal fungal Necromass in response to warming. These changes were most pronounced in hollow microsites, which showed convergence towards the Necromass-associated microbial communities present in unwarmed hummocks. We also observed a high colonization of ericoid mycorrhizal fungal Necromass by fungi from the same genera as the Necromass. These results indicate that microbial communities associated with mycorrhizal fungal Necromass decomposition are likely to change significantly with future climate warming, which may have strong impacts on soil biogeochemical cycles in peatlands. Additionally, the high enrichment of congeneric fungal decomposers on ericoid mycorrhizal Necromass may help to explain the increase in ericoid shrub dominance in warming peatlands.
-
distinct carbon fractions drive a generalisable two pool model of fungal Necromass decomposition
Functional Ecology, 2021Co-Authors: Craig R See, Peter G Kennedy, Christopher W Fernandez, Katherine Heckman, Anna M Conley, Lang C Delancey, Sarah E HobbieAbstract:Fungi represent a rapidly cycling pool of carbon (C) and nitrogen (N) in soils. Understanding of how this pool impacts soil nutrient availability and organic matter fluxes is hindered by uncertainty regarding the dynamics and drivers of fungal Necromass decomposition. Here we assessed the generality of common models for predicting mass loss during fungal Necromass decomposition and linked the resulting parameters to Necromass substrate chemistry. We decomposed 28 different types of fungal Necromass in laboratory microcosms over a 90-day period, measuring mass loss on all types, and N release on a subset of types. We characterised the initial chemistry of each Necromass type using: (a) fibre analysis methods commonly used for plant tissues, (b) initial melanin and nitrogen (N) concentrations and (c) Fourier transform infrared (FTIR) spectroscopy to assess the presence of bonds associated with common biomolecules. We found universal support for an asymptotic model of decomposition, which assumes that fungal Necromass consists of an exponentially decomposing 'fast' pool, and a 'slow' pool that decomposes at a rate approaching zero. The strongest predictor of the fast pool decay rate (k) was the proportion of cell soluble components, though initial N concentration also predicted k, albeit more weakly. The size of the slow pool was best predicted by the acid non-hydrolysable fraction, which was positively correlated with melanin-associated aromatics. Nitrogen dynamics varied by Necromass type, ranging from net N release to net immobilisation. The maximum quantity of N immobilised was inversely related to cell soluble contents and k, as positively related to FTIR spectra associated with cell wall polysaccharides. Collectively, our results indicate that the decomposition of fungal Necromass in soils can be described as having two distinct stages that are driven by different components of substrate C chemistry, with implications for rates of N availability and organic matter accumulation in soils.
-
melanin mitigates the accelerated decay of mycorrhizal Necromass with peatland warming
Ecology Letters, 2019Co-Authors: Christopher W Fernandez, Katherine Heckman, Randall K Kolka, Peter G KennedyAbstract:Despite being a significant input into soil carbon pools of many high-latitude ecosystems, little is known about the effects of climate change on the turnover of mycorrhizal fungal Necromass. Here, we present results from the first experiment examining the effects of climate change on the long-term decomposition of mycorrhizal Necromass, utilising the Spruce and Peatland Response Under Changing Environments (SPRUCE) experiment. Warming significantly increased Necromass decomposition rates but was strongest in normally submerged microsites where warming caused water table drawdown. Necromass chemistry exerted the strongest control on the decomposition, with initial nitrogen content strongly predicting early decay rates (3 months) and initial melanin content determining mass remaining after 2 years. Collectively, our results suggest that as global temperatures rise, variation in species biochemical traits as well as microsites where mycorrhizal Necromass is deposited will determine how these important inputs contribute to the belowground storage of carbon in boreal peatlands.
-
the afterlife effects of fungal morphology contrasting decomposition rates between diffuse and rhizomorphic Necromass
Soil Biology & Biochemistry, 2018Co-Authors: Amanda K Certano, Christopher W Fernandez, Katherine Heckman, Peter G KennedyAbstract:Microbial Necromass is now recognized as an important input into stable soil organic matter pools in terrestrial ecosystems. While melanin and nitrogen content have been identified as factors that influence the decomposition rate of fungal Necromass, the effects of mycelial morphology on Necromass decomposition remain largely unknown. Using the fungus Armillaria mellea, which produces both diffuse and rhizomorphic biomass in pure culture, we assessed the effects of Necromass morphology on decomposition in a 12 week field experiment in Pinus and Quercus dominated forests in Minnesota, USA. Diffuse and rhizomorphic Necromass was incubated for 2, 4, 6, and 12 weeks to assess differences in decay rates and changes in residual Necromass chemistry. Rhizomorphic Necromass decomposed significantly slower than diffuse Necromass in both forest types. This difference was correlated with initial Necromass chemistry, particularly nitrogen content, but not with hydrophobicity. Over the course of the incubation, there was a greater change in the chemistry of diffuse versus rhizomorphic Necromass, with both becoming more enriched in recalcitrant compounds. Given that many fungi with both saprotrophic and mycorrhizal ecologies produce rhizomorphs, these results suggest that mycelial morphology should be explicitly considered as an important functional trait influencing the rate of fungal Necromass decomposition.
-
the decomposition of ectomycorrhizal fungal Necromass
Soil Biology & Biochemistry, 2016Co-Authors: Christopher W Fernandez, Adam J Langley, Samantha K Chapman, Luke M Mccormack, Roger T KoideAbstract:The turnover of ectomycorrhizal (EM) fungal biomass represents a significant input into forest carbon (C) and nutrient cycles. Given the size of these fluxes, understanding the factors that control the decomposition of this Necromass will greatly improve understanding of C and nutrient cycling in ecosystems. Recent research has highlighted the considerable variation in the decomposition rates of EM fungal Necromass, and patterns from this research are beginning to emerge. In this article we review the research that has examined both intrinsic and extrinsic factors that control the decomposition of EM fungal Necromass and propose additional factors that may strongly influence EM fungal Necromass decomposition and ecosystem properties. We argue that, as with most plant litters, the stoichiometry (C:N) of EM Necromass is an important factor governing decomposition, but its role is modulated by the nature of the C and N in the tissue. In particular, melanin concentration appears to negatively influence the quality of EM fungal Necromass much as lignin does in plant litters. Other intrinsic factors such as the morphology of the mycelium may also play a large role and suggest this as a focus for future research. Extrinsic factors, such as decomposer community activity and physical protection by soil, are also likely to be important in governing the decomposition of ectomycorrhizal Necromass in situ. Finally, we highlight the potential importance of EM fungal Necromass diversity and abundance in influencing terrestrial biogeochemical cycles. Understanding the factors that control the decomposition of EM Necromass will then improve the predictive power of next-generation terrestrial biosphere models.
Francois Maillard - One of the best experts on this subject based on the ideXlab platform.
-
warming drives a hummockification of microbial communities associated with decomposing mycorrhizal fungal Necromass in peatlands
New Phytologist, 2021Co-Authors: Francois Maillard, Christopher W Fernandez, Katherine Heckman, Sunil Mundra, Randall K Kolka, Havard Kauserud, Peter G KennedyAbstract:Dead fungal mycelium (Necromass) represents a critical component of soil carbon (C) and nutrient cycles. Assessing how the microbial communities associated with decomposing fungal Necromass change as global temperatures rise will help in determining how these belowground organic matter inputs contribute to ecosystem responses. In this study, we characterized the structure of bacterial and fungal communities associated with multiple types of decaying mycorrhizal fungal Necromass incubated within mesh bags across a 9°C whole ecosystem temperature enhancement in a boreal peatland. We found major taxonomic and functional shifts in the microbial communities present on decaying mycorrhizal fungal Necromass in response to warming. These changes were most pronounced in hollow microsites, which showed convergence towards the Necromass-associated microbial communities present in unwarmed hummocks. We also observed a high colonization of ericoid mycorrhizal fungal Necromass by fungi from the same genera as the Necromass. These results indicate that microbial communities associated with mycorrhizal fungal Necromass decomposition are likely to change significantly with future climate warming, which may have strong impacts on soil biogeochemical cycles in peatlands. Additionally, the high enrichment of congeneric fungal decomposers on ericoid mycorrhizal Necromass may help to explain the increase in ericoid shrub dominance in warming peatlands.
-
root presence modifies the long term decomposition dynamics of fungal Necromass and the associated microbial communities in a boreal forest
Molecular Ecology, 2021Co-Authors: Francois Maillard, Peter G Kennedy, Bartosz Adamczyk, Jussi Heinonsalo, Marc BueeAbstract:Recent studies have highlighted that dead fungal mycelium represents an important fraction of soil carbon (C) and nitrogen (N) inputs and stocks. Consequently, identifying the microbial communities and the ecological factors that govern the decomposition of fungal Necromass will provide critical insight into how fungal organic matter (OM) affects forest soil C and nutrient cycles. Here, we examined the microbial communities colonising fungal Necromass during a multiyear decomposition experiment in a boreal forest, which included incubation bags with different mesh sizes to manipulate both plant root and microbial decomposer group access. Necromass-associated bacterial and fungal communities were taxonomically and functionally rich throughout the 30 months of incubation, with increasing abundances of oligotrophic bacteria and root-associated fungi (i.e., ectomycorrhizal, ericoid mycorrhizal and endophytic fungi) in the late stages of decomposition in the mesh bags to which they had access. Necromass-associated β-glucosidase activity was highest at 6 months, while leucine aminopeptidase peptidase was highest at 18 months. Based on an asymptotic decomposition model, root presence was associated with an initial faster rate of fungal Necromass decomposition, but resulted in higher amounts of fungal Necromass retained at later sampling times. Collectively, these results indicate that microbial community composition and enzyme activities on decomposing fungal Necromass remain dynamic years after initial input, and that roots and their associated fungal symbionts result in the slowing of microbial Necromass turnover with time.
-
substrate quality drives fungal Necromass decay and decomposer community structure under contrasting vegetation types
Journal of Ecology, 2020Co-Authors: Katilyn V Beidler, Francois Maillard, Richard P Phillips, Erin Andrews, Ryan M Mushinski, Peter G KennedyAbstract:1.Fungal mycelium is increasingly recognized as a central component of soil biogeochemical cycling, yet our current understanding of the ecological controls on fungal Necromass decomposition is limited to single sites and vegetation types. 2.By deploying common fungal Necromass substrates in a temperate oak savanna and hardwood forest in the midwestern USA, we assessed the generality of the rate at which high‐ and low‐quality fungal Necromass decomposes; further, we investigated how the decomposer ‘necrobiome’ varies both across and within sites under vegetation types dominated by either arbuscular or ectomycorrhizal plants. 3.The effects of Necromass quality on decay rate were robust to site and vegetation type differences, with high‐quality fungal Necromass decomposing, on average, 2.5 times faster during the initial stages of decay. Across vegetation types, bacterial and fungal communities present on decaying Necromass differed from bulk soil microbial communities and were influenced by Necromass quality. Moulds, yeasts and copiotrophic bacteria consistently dominated the necrobiome of high‐quality fungal substrates. 4.Synthesis. We show that regardless of differences in decay environments, high‐quality fungal substrates decompose faster and support different types of decomposer micro‐organisms when compared with low‐quality fungal tissues. These findings help to refine our theoretical understanding of the dominant factors affecting fast cycling components of soil organic matter and the microbial communities associated with rapid decay.
-
functional convergence in the decomposition of fungal Necromass in soil and wood
FEMS Microbiology Ecology, 2020Co-Authors: Francois Maillard, Erin Andrews, Kathryn M Schreiner, Jonathan S Schilling, Peter G KennedyAbstract:Understanding the post-senescent fate of fungal mycelium is critical to accurately quantifying forest carbon and nutrient cycling, but how this organic matter source decomposes in wood remains poorly studied. In this study, we compared the decomposition of dead fungal biomass (a.k.a. Necromass) of two species, Mortierella elongata and Meliniomyces bicolor, in paired wood and soil plots in a boreal forest in northern Minnesota, USA. Mass loss was quantified at four time points over an 8-week incubation and the richness and composition of the fungal communities colonizing fungal Necromass were characterized using high-throughput sequencing. We found that the structure of fungal decomposer communities in wood and soil differed, but, in both habitats, there was relatively rapid decay (∼30% remaining after 56 days). Mass loss was significantly faster in soil and for high-quality (i.e. high nitrogen and low melanin) fungal Necromass. In both habitats, there was a clear trajectory of early colonization by opportunistic fungal taxa followed by colonization of fungi with greater enzymatic capacities to degrade more recalcitrant compounds, including white-rot and ectomycorrhizal fungi. Collectively, our results indicate that patterns emerging regarding substrate quality effects on fungal Necromass decomposition in soil and leaf litter can be largely extended to fungal Necromass decomposition in wood.
-
first evidences that the ectomycorrhizal fungus paxillus involutus mobilizes nitrogen and carbon from saprotrophic fungus Necromass
Environmental Microbiology, 2019Co-Authors: Emila Akroume, Francois Maillard, Cyrille Bach, Christian Hossann, Claude Brechet, Bernhard Zeller, Nicolas Angeli, Laurent SaintandreAbstract:Fungal succession in rotting wood shows a surprising abundance of ectomycorrhizal (EM) fungi during the late decomposition stages. To better understand the links between EM fungi and saprotrophic fungi, we investigated the potential capacities of the EM fungus Paxillus involutus to mobilize nutrients from Necromass of Postia placenta, a wood rot fungus, and to transfer these elements to its host tree. In this aim, we used pure cultures of P. involutus in the presence of labelled Postia Necromass (15N/13C) as nutrient source, and a monoxenic mycorrhized pine experiment composed of labelled Postia Necromass and P. involutus culture in interaction with pine seedlings. The isotopic labelling was measured in both experiments. In pure culture, P. involutus was able to mobilize N, but C as well, from the Postia Necromass. In the symbiotic interaction experiment, we measured high 15N enrichments in all plant and fungal compartments. Interestingly, 13C remains mainly in the mycelium and mycorrhizas, demonstrating that the EM fungus transferred essentially N from the Necromass to the tree. These observations reveal that fungal organic matter could represent a significant N source for EM fungi and trees, but also a C source for mycorrhizal fungi, including in symbiotic lifestyle.
