scholarly journals Fungi exposed to chronic nitrogen enrichment are less able to decay leaf litter

2016 ◽  
Author(s):  
Linda T.A. van Diepen ◽  
Serita D. Frey ◽  
Elizabeth A. Landis ◽  
Eric W. Morrison ◽  
Anne Pringle
Keyword(s):  
Growth Rates ◽  
Common Garden ◽  
N Deposition ◽  
Plant Litter ◽  
Atmospheric N Deposition ◽  
Saprotrophic Fungi ◽  
Soil C ◽  
Litter Decay ◽  
N Enrichment

AbstractSaprotrophic fungi are the primary decomposers of plant litter in temperate forests, and their activity is critical for carbon (C) and nitrogen (N) cycling. Simulated atmospheric N deposition is associated with reduced fungal biomass, shifts in fungal community structure, slowed litter decay, and soil C accumulation. Although rarely studied, N deposition may also result in novel selective pressures on fungi, affecting evolutionary trajectories. To directly test if long-term N enrichment reshapes fungal behaviors, we isolated decomposer fungi from a longterm (28 year) N addition experiment and used a common garden approach to compare growth rates and decay abilities of isolates from control and N amended plots. Both growth and decay were significantly altered by long-term exposure to N enrichment. Changes in growth rates were idiosyncratic, but litter decay by N isolates was generally lower compared to control isolates of the same species, a response not readily reversed when N isolates were grown in control (low N) environments. Changes in fungal behaviors accompany and perhaps drive previously observed N-induced shifts in fungal diversity, community composition, and litter decay dynamics.

scholarly journals Soil Nitrate Mediates the Responses of Plant Community Production to the Frequency of N Addition in a Temperate Grassland: A Decadal Field Experiment

2021 ◽  
Author(s):  
Changchun Song ◽  
Yuqiu Zhang ◽  
Zhengru Ren ◽  
Haining Lu ◽  
Xu Chen ◽  
...  
Keyword(s):  
Plant Community ◽  
Net Primary Productivity ◽  
Northern China ◽  
N Deposition ◽  
Temperate Grassland ◽  
N Addition ◽  
Aboveground Net Primary Productivity ◽  
Atmospheric N Deposition ◽  
N Enrichment

Abstract PurposeNitrogen (N) enrichment through either artificial N application or atmospheric N deposition often increases ecosystem aboveground net primary productivity (ANPP). Therefore, results from N addition experiments have been used to assess the effects of atmospheric N deposition on ecosystems. However, the frequency of atmospheric N deposition is higher than that of artificial N addition. Whether the frequency of N addition alters the long-term response of ecosystem ANPP remains unclear. MethodsWe conducted a N addition frequency experiment from 2010 in a temperate grassland, northern China. Plant community ANPP was collected in 2019 and 2020, and soil physicochemical properties were measured in 2020. ResultsPlant community ANPP was significantly enhanced by N addition, whereas these increments declined with the frequency of N addition. The responses of the grasses ANPP to the frequency of N addition were similar to those of the plant community ANPP. Forbs ANPP was not significantly altered by the frequency of N addition. Meanwhile, soil ammonium and nitrate (NO3−–N) concentrations decreased with increasing N addition frequency, while the soil water content (SWC) and pH were similar among the frequencies of N addition. Moreover, SWC and soil NO3−–N jointly promoted grasses ANPP, ultimately increasing the plant community ANPP. ConclusionOur findings extend the water and N co-limitation hypothesis by specifying the preference for NO3−–N in arid/semi-arid regions. This study also illustrates that a higher frequency of N addition is more suitable for assessing the long-term impacts of atmospheric N deposition on ecosystems.

scholarly journals Microbial Mechanisms Mediating Increased Soil C Storage under Elevated Atmospheric N Deposition

2012 ◽  
Vol 79 (4) ◽  
pp. 1191-1199 ◽  
Author(s):  
Sarah D. Eisenlord ◽  
Zachary Freedman ◽  
Donald R. Zak ◽  
Kai Xue ◽  
Zhili He ◽  
...  
Keyword(s):  
Forest Floor ◽  
Forest Ecosystems ◽  
N Deposition ◽  
Fungal Communities ◽  
Functional Genes ◽  
Atmospheric N Deposition ◽  
Soil C ◽  
C Storage ◽  
Genes Encoding ◽  
Soil C Storage

ABSTRACTFuture rates of anthropogenic N deposition can slow the cycling and enhance the storage of C in forest ecosystems. In a northern hardwood forest ecosystem, experimental N deposition has decreased the extent of forest floor decay, leading to increased soil C storage. To better understand the microbial mechanisms mediating this response, we examined the functional genes derived from communities of actinobacteria and fungi present in the forest floor using GeoChip 4.0, a high-throughput functional-gene microarray. The compositions of functional genes derived from actinobacterial and fungal communities was significantly altered by experimental nitrogen deposition, with more heterogeneity detected in both groups. Experimental N deposition significantly decreased the richness and diversity of genes involved in the depolymerization of starch (∼12%), hemicellulose (∼16%), cellulose (∼16%), chitin (∼15%), and lignin (∼16%). The decrease in richness occurred across all taxonomic groupings detected by the microarray. The compositions of genes encoding oxidoreductases, which plausibly mediate lignin decay, were responsible for much of the observed dissimilarity between actinobacterial communities under ambient and experimental N deposition. This shift in composition and decrease in richness and diversity of genes encoding enzymes that mediate the decay process has occurred in parallel with a reduction in the extent of decay and accumulation of soil organic matter. Our observations indicate that compositional changes in actinobacterial and fungal communities elicited by experimental N deposition have functional implications for the cycling and storage of carbon in forest ecosystems.

Carbon storage in phosphorus limited grasslands may decline in response to elevated nitrogen deposition: a long term field manipulation and modelling study 

2021 ◽  
Author(s):  
Christopher Taylor ◽  
Victoria Janes-Bassett ◽  
Gareth Phoenix ◽  
Ben Keane ◽  
Iain Hartley ◽  
...  
Keyword(s):  
N Deposition ◽  
Calcareous Grassland ◽  
Organic P ◽  
N Addition ◽  
Soil C ◽  
P Limitation ◽  
P Cycling ◽  
Nutrient Manipulation ◽  
N And P Cycling

<p>In ecosystems where nitrogen (N) limits plant productivity, N deposition can stimulate plant growth, and consequently, promote carbon (C) sequestration by increasing input of detrital C and other forms of plant C to the soil. However, other forms of nutrient limitation such as phosphorus (P) limitation and N-P co-limitation are widespread and may increase in prevalence with N deposition. Our understanding of how terrestrial ecosystem C, N and P cycling may be affected by N deposition when N is not the sole limiting resource is fairly limited. In this work, we investigate the consequences of enhanced N addition on C, N and P cycling in grasslands that exhibit contrasting forms of nutrient limitation.</p><p>We do so by collecting data from a long-term nutrient manipulation experiment on two N-P co-limited grasslands; an acidic grassland of stronger N-limitation and a calcareous grassland of stronger P limitation, and integrating this into a mechanistic C, N and P cycling model (N14CP). To simulate the experimental grasslands and explore the role of P access mechanisms in determining ecosystem state, we allowed P access to vary, and compared the outputs to plant-soil C, N and P data. Combinations of organic P access and inorganic P availability most closely representing data were used to simulate the grasslands and quantify their temporal response to nutrient manipulation.</p><p>The modelled grasslands showed contrasting responses to simulated N deposition. In the acidic grassland, N addition greatly increased C stocks by stimulating biomass productivity, but the same N treatments reduced the organic C pool in the calcareous grassland. Nitrogen deposition exacerbated P limitation in the calcareous grassland by reducing the size of the bioavailable P pool to plants, reducing biomass input to the soil C pool. Plant acquisition of organic P played an important role in determining the nutrient conditions of the grasslands, as both simulated grasslands increased organic P uptake to meet enhanced P demand driven by N deposition. Greater access to organic P in the acidic grassland prevented a shift to P limitation under elevated levels of N deposition, but organic P access was too low in the calcareous grassland to prevent worsening P limitation.</p><p>We conclude that grasslands of differing limiting nutrients may respond to N deposition in contrasting ways, and stress that as N deposition shifts ecosystems toward P limitation, a globally important carbon sink risks degradation.</p>

scholarly journals 15N natural abundances in two podsol soils of two spruce forests differing in their atmospheric N deposition conditions

2011 ◽  
Vol 51 (No. 9) ◽  
pp. 416-422 ◽  
Author(s):  
S.P. Sah
Keyword(s):  
Mineral Soil ◽  
Vertical Gradient ◽  
N Deposition ◽  
Climatic Conditions ◽  
Organic Layer ◽  
Atmospheric N Deposition ◽  
Spruce Forests ◽  
Humus Layer ◽  
N Enrichment ◽  
Deposition Conditions

This study aims to investigate the changes in isotope ratios in foliage and soils of the two spruce forests [Picea abies (L.) Karst.] differing greatly in their atmospheric N deposition and climatic conditions. As expected, both N concentrations and <sup>15</sup>N values in both needles and litter were found to be significantly higher in the Solling stand (N-saturated) compared to the Hyytial&auml; stand (N-poor). For the N-limited site (Hyytial&auml; plot), a typical vertical gradient of the soil <sup>15</sup>N-enrichment (both in organic and mineral soil) was observed. The N-saturated site (Solling) differs from the N-limited site (Hyytial&auml;) with respect to the <sup>15</sup>N abundance trend in organic layer. In the upper organic layer up to O-f horizon, i.e. mor layer (0&ndash;3.5 cm depth) of Solling plot, there is almost a trend of slight soil <sup>15</sup>N-depletion with increasing depth, and then there is a <sup>15</sup>N-enrichment from O-h horizon (humus layer) of organic layer to mineral soil horizons. This is explained by the presence of prominent NO<sub>3</sub><sup>&ndash;</sup> leaching at this plot

scholarly journals Microbial Mechanisms Mediating Increased Soil C Storage under Elevated Atmospheric N Deposition

2013 ◽  
Vol 79 (8) ◽  
pp. 2847-2847 ◽  
Author(s):  
Sarah D. Eisenlord ◽  
Zachary Freedman ◽  
Donald R. Zak ◽  
Kai Xue ◽  
Zhili He ◽  
...  
Keyword(s):  
N Deposition ◽  
Atmospheric N Deposition ◽  
Soil C ◽  
C Storage ◽  
Soil C Storage

Analysis of litter decomposition in an alpine tundra

1998 ◽  
Vol 76 (7) ◽  
pp. 1295-1304 ◽  
Author(s):  
David M Bryant ◽  
Elisabeth A Holland ◽  
Timothy R Seastedt ◽  
Marilyn D Walker
Keyword(s):  
Mass Loss ◽  
Litter Decomposition ◽  
Growing Season ◽  
Plant Litter ◽  
Decay Rates ◽  
Alpine Tundra ◽  
Litter Decay ◽  
Root Litter ◽  
Nitrogen Additions

Decomposition of plant litter regulates nutrient cycling and transfers of fixed carbon to soil organic matter pools in terrestrial ecosystems. Climate, as well as factors of intrinsic litter chemistry, often govern the rate of decomposition and thus the dynamics of these processes. Initial concentrations of nitrogen and recalcitrant carbon compounds in plant litter are good predictors of litter decomposition rates in many systems. The effect of exogenous nitrogen availability on decay rates, however, is not well defined. Microclimate factors vary widely within alpine tundra sites, potentially affecting litter decay rates at the local scale. A controlled factorial experiment was performed to assess the influence of landscape position and exogenous nitrogen additions on decomposition of surface foliage and buried root litter in an alpine tundra in the Front Range of the Rocky Mountains in Colorado, U.S.A. Litter bags were placed in three communities representing a gradient of soil moisture and temperature. Ammonium nitrate was applied once every 30 days at a rate of 20 g N·m-2 during the 3-month growing season. Data, as part of the Long-Term Inter-site Decomposition Experiment Team project, were analyzed to ascertain the effects of intrinsic nitrogen and carbon fraction chemistry on litter decay in alpine systems. Soil moisture was found to be the primary controlling factor in surface litter mass loss. Root litter did not show significant mass loss following first growing season. Nitrogen additions had no effect on nitrogen retention, or decomposition, of surface or buried root litter compared with controls. The acid-insoluble carbon fraction was a good predictor of mass loss in surface litters, showing a strong negative correlation. Curiously, N concentration appeared to retard root decomposition, although degrees of freedom limit the confidence of this observation. Given the slow rate of decay and N loss from root litter, root biomass appears to be a long-term reservoir for C and N in the alpine tundra.Key words: litter decomposition, alpine tundra, nitrogen deposition, LIDET, Niwot Ridge.

 Implementation of mycorrhizal mechanism into a soil carbon model improves the prediction of long-term processes of plant litter decomposition

2021 ◽  
Author(s):  
Weilin Huang ◽  
Peter van Bodegom ◽  
Toni Viskari ◽  
Jari Liski ◽  
Nadejda Soudzilovskaia
Keyword(s):  
Soil Carbon ◽  
Litter Decomposition ◽  
Arbuscular Mycorrhizae ◽  
Plant Litter ◽  
Climate Impacts ◽  
Microbial Interactions ◽  
Soil C ◽  
Plant Litter Decomposition ◽  
C Dynamics

&lt;p&gt;Mycorrhizae, a plant-fungal symbiosis, is an important contributor to below ground-microbial interactions, and hypothesized to play a paramount role in soil carbon (C) sequestration. Ectomycorrhizae (EM) and arbuscular mycorrhizae (AM) are the two dominant forms of mycorrhizae featured by nearly all Earth plant species. However, the difference in the nature of their contributions to the processes of plant litter decomposition is still understood poorly. Current soil carbon models treat mycorrhizal impacts on the processes of soil carbon transformation as a black box. This retards scientific progress in mechanistic understanding of soil C dynamics.&lt;/p&gt;&lt;p&gt;We examined four alternative conceptualizations of the mycorrhizal impact on plant litter C transformations, by integrating AM and EM fungal impacts on litter C pools of different recalcitrance into the soil carbon model Yasso15. The best performing concept featured differential impacts of EM and AM on a combined pool of labile C, being quantitatively distinct from impacts of AM and EM on a pool of recalcitrant C.&lt;/p&gt;&lt;p&gt;Analysis of time dynamics of mycorrhizal impacts on soil C transformations demonstrated that these impacts are larger at the long-term (&gt;2.5yrs) litter decomposition processes, compared to the short-term processes. We detected that arbuscular mycorrhizae controls shorter term decomposition of labile carbon compounds, while ectomycorrhizae dominate the long term decomposition processes of highly recalcitrant carbon elements. Overall, adding our mycorrhizal module into the Yasso model greatly improved the accuracy of the temporal dynamics of carbon sequestration.&lt;/p&gt;&lt;p&gt;A sensitivity analysis of litter decomposition to climate and mycorrhizal factors indicated that ignoring the mycorrhizal impact on the decomposition leads to an overestimation of climate impacts. This suggests that being co-linear with climate impacts, mycorrhizal impacts could be partly hidden within climate factors in soil carbon models, reducing the capability of such models to mechanistically predict impacts of climate vs vegetation change on soil carbon dynamics.&lt;/p&gt;&lt;p&gt;Our results provide a benchmark to mechanistic modelling of microbial impacts on soil C dynamics. This work opens new pathways to examining the impacts of land-use change and climate change on plant-microbial interactions and their role in soil C dynamics, allowing the integration of microbial processes into global vegetation models used for policy decisions on terrestrial carbon monitoring.&lt;/p&gt;

scholarly journals Subalpine grassland carbon balance during 7 years of increased atmospheric N deposition

2016 ◽  
Vol 13 (12) ◽  
pp. 3807-3817 ◽  
Author(s):  
Matthias Volk ◽  
Jan Enderle ◽  
Seraina Bassin
Keyword(s):  
Carbon Balance ◽  
N Deposition ◽  
Control Treatment ◽  
Atmospheric N Deposition ◽  
Total N ◽  
Plant Yield ◽  
Soil C ◽  
Grassland Ecosystems ◽  
Unimodal Response ◽  
Microbial N

Abstract. Air pollution agents interact when affecting biological sinks for atmospheric CO2, e.g., the soil organic carbon (SOC) content of grassland ecosystems. Factors favoring plant productivity, like atmospheric N deposition, are usually considered to favor SOC storage. In a 7-year experiment in subalpine grassland under N- and O3-deposition treatment, we examined C fluxes and pools. Total N deposition was 4, 9, 14, 29 and 54 kg N ha−1 yr−1 (N4, N9, etc.); annual mean phytotoxic O3 dose was 49, 65 and 89 mmol m−2 projected leaf area. We hypothesized that between years SOC of this mature ecosystem would not change in control treatments and that effects of air pollutants are similar for plant yield, net ecosystem productivity (NEP) and SOC content, leading to SOC content increasing with N deposition. Cumulative plant yield showed a significant N and N  ×  N effect (+38 % in N54) but no O3 effect. In the control treatment SOC increased significantly by 9 % in 7 years. Cumulative NEP did show a strong, hump-shaped response pattern to N deposition with a +62 % increase in N14 and only +39 % increase in N54 (N effect statistically not significant, N  ×  N interaction not testable). SOC had a similar but not significant response to N, with highest C gains at intermediate N deposition rates, suggesting a unimodal response with a marginal (P = 0.09) N  ×  N interaction. We assume the strong, pollutant-independent soil C sink developed as a consequence of the management change from grazing to cutting. The non-parallel response of SOC and NEP compared to plant yield under N deposition is likely the result of increased respiratory SOC losses, following mitigated microbial N-limitation or priming effects, and a shift in plant C allocation leading to smaller C input from roots.

scholarly journals Atmospheric N Deposition Increases Bacterial Laccase-Like Multicopper Oxidases: Implications for Organic Matter Decay

2014 ◽  
Vol 80 (14) ◽  
pp. 4460-4468 ◽  
Author(s):  
Zachary Freedman ◽  
Donald R. Zak
Keyword(s):  
Organic Matter ◽  
Forest Floor ◽  
N Deposition ◽  
Multicopper Oxidases ◽  
Atmospheric N Deposition ◽  
Content Type ◽  
Soil C ◽  
C Storage ◽  
Soil C Storage ◽  
Compositional Changes

ABSTRACTAnthropogenic release of biologically available nitrogen (N) has increased dramatically over the last 150 years, which can alter the processes controlling carbon (C) storage in terrestrial ecosystems. In a northern hardwood forest ecosystem located in Michigan in the United States, nearly 20 years of experimentally increased atmospheric N deposition has reduced forest floor decay and increased soil C storage. This change occurred concomitantly with compositional changes inBasidiomycetefungi and inActinobacteria, as well as the downregulation of fungal lignocelluloytic genes. Recently, laccase-like multicopper oxidases (LMCOs) have been discovered among bacteria which can oxidize β-O-4 linkages in phenolic compounds (e.g., lignin and humic compounds), resulting in the production of dissolved organic carbon (DOC). Here, we examined how nearly 2 decades of experimental N deposition has affected the abundance and composition of saprotrophic bacteria possessing LMCO genes. In our experiment, LMCO genes were more abundant in the forest floor under experimental N deposition whereas the abundances of bacteria and fungi were unchanged. Experimental N deposition also led to less-diverse, significantly altered bacterial and LMCO gene assemblages, with taxa implicated in organic matter decay (i.e.,Actinobacteria,Proteobacteria) accounting for the majority of compositional changes. These results suggest that experimental N deposition favors bacteria in the forest floor that harbor the LMCO gene and represents a plausible mechanism by which anthropogenic N deposition has reduced decomposition, increased soil C storage, and accelerated phenolic DOC production in our field experiment. Our observations suggest that future rates of atmospheric N deposition could fundamentally alter the physiological potential of soil microbial communities.

scholarly journals Anthropogenic N Deposition Alters the Composition of Expressed Class II Fungal Peroxidases

2018 ◽  
Vol 84 (9) ◽  
Author(s):  
Elizabeth M. Entwistle ◽  
Karl J. Romanowicz ◽  
William A. Argiroff ◽  
Zachary B. Freedman ◽  
J. Jeffrey Morris ◽  
...  
Keyword(s):  
Class Ii ◽  
N Deposition ◽  
Plant Litter ◽  
Soil C ◽  
C Storage ◽  
Plant Litter Decomposition ◽  
Rate Limiting Step ◽  
Soil C Storage ◽  
Induced Changes ◽  
Rate Limiting

ABSTRACTHere, we present evidence that ca. 20 years of experimental N deposition altered the composition of lignin-decaying class II peroxidases expressed by forest floor fungi, a response which has occurred concurrently with reductions in plant litter decomposition and a rapid accumulation of soil organic matter. This finding suggests that anthropogenic N deposition has induced changes in the biological mediation of lignin decay, the rate limiting step in plant litter decomposition. Thus, an altered composition of transcripts for a critical gene that is associated with terrestrial C cycling may explain the increased soil C storage under long-term increases in anthropogenic N deposition.IMPORTANCEFungal class II peroxidases are enzymes that mediate the rate-limiting step in the decomposition of plant material, which involves the oxidation of lignin and other polyphenols. In field experiments, anthropogenic N deposition has increased soil C storage in forests, a result which could potentially arise from anthropogenic N-induced changes in the composition of class II peroxidases expressed by the fungal community. In this study, we have gained unique insight into how anthropogenic N deposition, a widespread agent of global change, affects the expression of a functional gene encoding an enzyme that plays a critical role in a biologically mediated ecosystem process.

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