Litter Decay Research Articles

Bacterial population-level trade-offs between drought tolerance and resource acquisition traits impact decomposition.

Microbes drive fundamental ecosystem processes such as decomposition. Environmental stressors are known to affect microbes, their fitness, and the ecosystem functions that they perform, yet understanding the causal mechanisms behind this influence has been difficult. We used leaf litter on soil surface as a model in situ system to assess changes in bacterial genomic traits and decomposition rates over 18months with drought as a stressor. We hypothesized that genome-scale trade-offs due to investment in stress tolerance traits under drought reduce the capacity for bacterial populations to carry out decomposition, and that these population-level trade-offs scale up to impact emergent community traits thereby reducing decomposition rates. We observed drought tolerance mechanisms that were heightened in bacterial populations under drought, identified as higher gene copy numbers in metagenome-assembled genomes. A subset of populations under drought had reduced carbohydrate-active enzyme genes which suggested - as a trade-off - a decline in decomposition capabilities. These trade-offs were driven by community succession and taxonomic shifts as distinct patterns appeared in populations. We show that trait-tradeoffs in bacterial populations under drought could scale up to reduce overall decomposition capabilities and litter decay rates. Using a trait-based approach to assess the population ecology of soil bacteria, we demonstrate genome-level trade-offs in response to drought with consequences for decomposition rates.

Variations in litterfall dynamics, root biomass, and sediment accretion in restored and recolonized mangroves in Leyte, Philippines

Litterfall production and decay, root biomass, and sediment accretion dynamics were investigated from restored ‘planted’ (R5, R8, R15, and R30 stands) and recolonized stands (C5, C12, and C20 stands) to investigate patterns in primary productivity, belowground biomass, and sediment accretion dynamics. Litterfall data was collected using litter traps over 12 months, while decay kinetics was investigated using a litterbag experiment. Root biomass and sediment accretion data were collected using makeshift acrylic corers. Litterfall production increased as stands aged, and tended to stabilize as it matured in restored (R8: 10.05 Mg/ha/yr; R30: 6.1 Mg/ha/yr) and recolonized stands (C5: 18.75 Mg/ha/yr; C20: 9.05 Mg/ha/yr). Leaf litter decay rates (K/d) showed no pattern with stand age, although the recolonized stands (range: 0.059–0.113 K/d) had lower decay rates compared to the restored (range: 0.073–0.123 K/d) and natural stands (range: 0.064–0.123 K/d). Root biomass declined with age in restored stands (R5: 67.16 Mg/ha, R30: 49.67 Mg/ha), but increased in recolonized stands (C5: 5.41 Mg/ha, C20: 19.50 Mg/ha). Very high rates of sediment accretion were found in younger restored (R5: 10.1 cm/yr) and recolonized stands (C5: 8.1 cm/yr) than mature stands (R30: 6.3 cm/yr; C20: 4.3 cm/yr). Our results showed disparities of patterns in mangrove vegetation growth in recolonized stands and huge potential contribution on mangrove productivity when these areas are effectively restored.

Multi-kingdom characterization of living organisms by 13C CPMAS NMR spectroscopy reveals unique traits in bacteria, fungi, algae, and higher plants

Determining the chemical quality of soil organic matter and decomposing organisms is critical for predicting carbon fluxes in ecosystems. However, the classical C/N and lignin/N ratios have been criticized for their capability in predicting ecosystem function including litter decay rate, nitrogen mineralization and soil aggregation. Therefore, with our work we aim to complement information on the chemical properties of primary producers and decomposers based on 13C NMR. Overall, 108 unique 13C NMR spectra were collected from higher plant tissues including leaf litter, fine roots, woody debris, as well as a range of microbes i.e. bacteria, fungi, and marine algae. Results showed clear discrimination between organisms belonging to different kingdoms, but with limited variability within bacteria, fungi, and microalgae. In detail, bacteria were found to be distinct not only from plant tissues but also from fungi, characterized by a high proportion of alkyl and carbonyl C types and a rather low relative abundance of O Alkyl C and di-O Alkyl C types. Among the fungi, we found clear separation between yeasts, which are more similar to bacteria, and filamentous species, which are rich in O Alkyl and di-O Alkyl C types. Microalgae are characterized by a high content of aliphatic, carboxylic and methoxyl C fractions. In the spectra of terrestrial plants, the O Alkyl C region, associated with sugars and cellulose, is more abundant compared to algae and bacteria. In addition, the aromatic carbon signal, which is mainly associated with lignin, is much higher for higher plants than in microorganisms. As for plant tissues, woody tissues are clearly different from leaves and fine roots, with grasses, sedges, and ferns being well distinguished from forbs, coniferous and deciduous trees. In summary, our study contains the largest freely available 13C NMR spectral library of bacteria, fungi, algae, and higher plant tissues. However, the data from higher plants are sufficient to cover different functional types, which is not yet possible for bacteria and fungi.

Improved Characterization of Soil Organic Matter by Integrating FT-ICR MS, Liquid Chromatography Tandem Mass Spectrometry, and Molecular Networking: A Case Study of Root Litter Decay under Drought Conditions.

Understanding of how soil organic matter (SOM) chemistry is altered in a changing climate has advanced considerably; however, most SOM components remain unidentified, impeding the ability to characterize a major fraction of organic matter and predict what types of molecules, and from which sources, will persist in soil. We present a novel approach to better characterize SOM extracts by integrating information from three types of analyses, and we deploy this method to characterize decaying root-detritus soil microcosms subjected to either drought or normal conditions. To observe broad differences in composition, we employed direct infusion Fourier-transform ion cyclotron resonance mass spectrometry (DI-FT-ICR MS). We complemented this with liquid chromatography tandem mass spectrometry (LC-MS/MS) to identify components by library matching. Since libraries contain only a small fraction of SOM components, we also used fragment spectral cosine similarity scores to relate unknowns and library matches through molecular networks. This integrated approach allowed us to corroborate DI-FT-ICR MS molecular formulas using library matches, which included fungal metabolites and related polyphenolic compounds. We also inferred structures of unknowns from molecular networks and improved LC-MS/MS annotation rates from ∼5 to 35% by considering DI-FT-ICR MS molecular formula assignments. Under drought conditions, we found greater relative amounts of lignin-like vs condensed aromatic polyphenol formulas and lower average nominal oxidation state of carbon, suggesting reduced decomposition of SOM and/or microbes under stress. Our integrated approach provides a framework for enhanced annotation of SOM components that is more comprehensive than performing individual data analyses in parallel.

The roles of seagrass litter decomposition in determining blue carbon sink capacity

AbstractSeagrass litter is a crucial autochthonous source of sediment organic carbon (Corg) that contributes to Corg storage in coastal ecosystems. However, our understanding of seagrass litter decomposition effects on sediment Corg sequestration and the factors influencing the capacity for autochthonous carbon sequestration remains limited. We investigated Zostera marina litter decomposition dynamics in eelgrass meadows along the Korean coast by monitoring changes in the remaining litter mass and autochthonous Corg during the decomposition process. We used a double‐component exponential decay models to characterize the decomposition dynamics and estimate the autochthonous Corg remaining. We also identified potential factors affecting litter decay and Corg accumulation in sediments by examining site‐specific physicochemical properties. Our findings revealed that double‐component models effectively characterized litter decomposition dynamics and indicated greater preservation of litter‐derived slowly degrading Corg in sediments. The reduced decomposition of litter materials owing to low oxygen availability in the muddy sediments led to greater retention of litter mass and litter‐derived Corg in sediments. The anoxic conditions of below‐ground litterbags, compared with above‐ground litterbags, could be alleviated by the oxygen transport through fresh Z. marina roots, thereby potentially stimulating the microbial decomposition of Z. marina below‐ground litter materials at these sites. Our findings highlight the importance of understanding litter decomposition dynamics to accurately assess the carbon sink capacity of seagrass meadows, and demonstrate that physicochemical properties can influence seagrass litter decomposition.

Feedback of litter decay to temporal stability of biomass under N‐inputs

AbstractNitrogen (N) input affects litter decay and ecosystem functioning. However, the mechanism of litter decay under temporal N‐inputs has rarely been observed. Here we show that three‐year experimental N‐inputs significantly stimulated the rate of litter decay to some extent and then inhibited it with increasing N‐inputs. The N‐inputs affected the litter's mass loss by directly influencing the temporal stability of aboveground biomass (BS) and diversity while indirectly changing soil pH, C: N ratio, and synergistic interactions of soil, vegetation, and microbial traits. The BS has emerged as a significant regulatory factor for the litter decay of tropical grassland. The outcome of the present study will be helpful in predicting the global feedback of litter decay on the N inputs and the amount of N required for the sustainable functioning of the degraded tropical or similar grasslands.

Negative plant-soil feedback in Arabidopsis thaliana: Disentangling the effects of soil chemistry, microbiome, and extracellular self-DNA

Nutrient deficiency, natural enemies and litter autotoxicity have been proposed as possible mechanisms to explain species-specific negative plant-soil feedback (PSF). Another potential contributor to negative PSF is the plant released extracellular self-DNA during litter decay. In this study, we sought to comprehensively investigate these hypotheses by using Arabidopsis thaliana (L.) Heynh as a model plant in a feedback experiment. The experiment comprised a conditioning phase and a response phase in which the conditioned soils underwent four treatments: (i) addition of activated carbon, (ii) washing with tap water, (iii) sterilization by autoclaving, and (iv) control without any treatment. We evaluated soil chemical properties, microbiota by shotgun sequencing and the amount of A. thaliana extracellular DNA in the differently treated soils. Our results showed that washing and sterilization treatments mitigated the negative PSF effect. While shifts in soil chemical properties were not pronounced, significant changes in soil microbiota were observed, especially after sterilization. Notably, plant biomass was inversely associated with the content of plant self-DNA in the soil. Our results suggest that the negative PSF observed in the conditioned soil was associated to increased amounts of soilborne pathogens and plant self-DNA. However, fungal pathogens were not limited to negative conditions, butalso found in soils enhancing A.thaliana growth. In-depth multivariate analysis highlights that the hypothesis of negative PSF driven solely by pathogens lacks consistency. Instead, we propose a multifactorial explanation for the negative PSF buildup, in which the accumulation of self-DNA weakens the plant’s root system, making it more susceptible to pathogens.

Meta-analysis reveals that vertebrates enhance plant litter decomposition at the global scale.

Evidence is mounting that vertebrate defaunation greatly impacts global biogeochemical cycling. Yet, there is no comprehensive assessment of the potential vertebrate influence over plant decomposition, despite litter decay being one of the largest global carbon fluxes. We therefore conducted a global meta-analysis to evaluate vertebrate effects on litter mass loss and associated element release across terrestrial and aquatic ecosystems. Here we show that vertebrates affected litter decomposition by various direct and indirect pathways, increasing litter mass loss by 6.7% on average, and up to 34.4% via physical breakdown. This positive vertebrate impact on litter mass loss was consistent across contrasting litter types (woody and non-woody), climatic regions (boreal, temperate and tropical), ecosystem types (aquatic and terrestrial) and vertebrate taxa, but disappeared when evaluating litter nitrogen and phosphorus release. Moreover, we found evidence of interactive effects between vertebrates and non-vertebrate decomposers on litter mass loss, and a larger influence of vertebrates at mid-to-late decomposition stages, contrasting with the invertebrate effect known to be strongest at early decomposition stage. Our synthesis demonstrates a global vertebrate control over litter mass loss, and further stresses the need to account for vertebrates when assessing the impacts of biodiversity loss on biogeochemical cycles.

Temporal changes in mixing effects on litter decay and nitrogen release in a boreal riparian forest in northeastern China

In riparian forests, litter decay provides essential energy and nutrients for both terrestrial and fluvial ecosystems. Litter mixing effects (LMEs) are crucial in regulating litter decay and nutrient dynamics, yet how LMEs change over time is unclear in riparian forests. In this study, leaf litter of three common species (Alnus sibirica Fisch. ex Turcz, Betula platyphylla Sukaczev, and Betula fruticosa Pall.) were mixed in an equal mass ratio and LMEs were measured for mass and nitrogen (N) remaining in whole litter mixtures over a 3-year period in a boreal riparian forest, northeastern China. LMEs were also assessed for component litter mass and N remaining by separating litter mixtures by species. During the decay of litter mixtures, antagonistic effects on mass and N remaining were dominant after one and two years of decay, whereas only additive effects were observed after three years. LMEs correlated negatively with functional diversity after the first and two years of decay but disappeared after three years. When sorting litter mixtures by species, non-additive LMEs on mass and N remaining decreased over incubation time. Moreover, non-additive LMEs were more frequent for litter of both B. platyphylla and B. fruticosa with lower N concentration than for A. sibirica litter with higher N concentration. These results indicate that incubation time is a key determinant of litter mixing effects during decay and highlight that late-stage litter mixture decay may be predicted from single litter decay dynamics in boreal riparian forests.

Impacts of land use history on leaf litter input, chemical composition, decomposition and related nutrient cycling in young and old secondary tropical lowland rainforests (Sumatra, Indonesia)

BackgroundNutrient cycle in tropical forests is mainly driven by litter fall amounts and by litter decay due to litter physical and chemical properties. Apart from differences in site conditions, different successional stages of tropical rainforests may influence nutrient inputs to the soil via differences in litter fall and decay.MethodsWe studied leaf litter fall, decomposition and related nutrient input to the soil in two secondary tropical rainforest types differing in land-use intensity and history in the lowlands of Sumatra (Indonesia).ResultsMean annual litter fall was by 29.5% higher in the old than in the young secondary forests. In contrast, annual litter decomposition differed only marginally (54.9% vs. 52.1%) in young vs. old secondary forests. Litter chemical composition (C, N, P, K contents) did not differ between the forest types. Litter decomposition was also not different between the forest types (4.6% vs. 4.3% loss of initial weight per month). Consequently, annual nutrient input to the soil was primarily affected by differences in leaf litter production, thus, old secondary forests exceeded that of young secondary forests by 30% and 24% for C and N, but was not different regaring P and K among the two forest types.ConclusionsThe results indicate that litter nutrient inputs to the soil in the two types of secondary tropical lowland forests are most strongly influenced by aboveground litter production rather than litter chemical quality or litter decay. We conclude that the restoration status of secondary tropical lowland forests is crucial for the nutrient status of these forest ecosystems.

Legume versus non-legume foliar litter decomposition in regularly burned loblolly pine forests

While understory prescribed burning is central to the ecological and economic management of many pine forests, there is concern that burning may cause excessive losses of N, thereby decreasing soil fertility and forest productivity. Symbiotic N2-fixation by fire-adapted native and naturalized herbaceous legumes may mitigate N losses due to burning. However, the N gain via legumes depends not only on the rates of N2-fixation, but also on the rates of litter decay between burn events. At present, the rates and controls of relatively N-rich legume litter decay in forests are poorly understood. In this study, foliar litter decomposition was assessed for 6 legume species (average [N] = 1.83 ± 0.52 %) and 4 non-legume species (average [N] = 0.80 ± 0.27 %) in “early” and “late” stage loblolly pine (Pinus taeda) forests for 3 years. We hypothesized that the N-rich legumes would exhibit greater mass loss, particularly in the early sites, and would thus release a greater percentage of their original N compared to the non-legumes. In contrast to our hypothesis, average mass loss rates were comparable for the legumes and non-legumes resulting in similar residual mass estimates (mean [95 % CI]) respectively in the early (11.9 % [9.8 %, 14.4 %] versus 15.5 % [12.2 %, 19.7 %]) and late (12.5 % [10.3 %, 15.1 %] versus 9.0 % [7.1 %, 11.3 %]) sites by the end of the study. Likewise, the average decay rate (k) for the legumes and non-legumes did not differ significantly in the early sites (0.73 ± 0.25 year−1 versus 0.69 ± 0.15 year−1, respectively), and the average legume decay rate was lower (P = 0.0080) than the average non-legume decay rate in the late sites (0.58 ± 0.18 year−1 versus 0.63 ± 0.13 year−1, respectively). Mass loss was typically greater in the early sites, but the differences were significant for less than 22 % of the comparisons. As hypothesized, legumes did release a greater percentage of their original N compared to non-legumes resulting in lower average N remaining estimates respectively in the early (34.2 % [29.4 %, 39.8 %] versus 51.3 % [40.2 %, 65.5 %]) and late (28.9 % [24.2 %, 34.5 %] versus 42.5 % [29.6 %, 61.1 %]) sites after 3 years. The results suggest that N, P, and S were co-regulators of litter decay, and that pine litter may be an important sink for these limiting macronutrients. The strong interplay among N, P, and S should be considered in the use of prescribed burning to reduce nutrient limitations in fire-maintained pine forests.

Soil carbon dynamics are linked to tree species growth strategy in a naturally regenerating tropical forest

Secondary tropical forests are increasingly important for their role in the global carbon (C) balance as they can rapidly accumulate aboveground biomass C during regrowth. Substantial amounts of plant-derived carbon are also incorporated into the soil through decomposition processes, but our understanding of soil C dynamics during forest regrowth is limited. Secondary succession is characterised by a shift in tree functional groups from light-demanding to shade-tolerant species over time, which can influence rates of C turnover via differences in litter quality and by modifying the decomposition environment. Changes in decomposition processes in turn affect the amount of organic C stored in the soil or released to the atmosphere as CO2. Consequently, understanding how tree functional composition influences C turnover during decomposition could help us predict soil C storage during tropical forest regrowth. We experimentally explored the relationship between tree functional groups and soil C dynamics (decomposition and respiration) by conducting a litter decomposition experiment across a successional gradient of naturally regenerating tropical forest. We created litter mixtures representing tree communities differing in their shade tolerance, as well as a functionally diverse litter mixture, and observed litter mass loss and soil respiration as measures of C turnover over a 6 month period. Litter from light-demanding species decomposed faster than litter from shade-tolerant species, which was reflected in the pattern of soil respiration. There were no clear patterns of increasing or decreasing rates of litter decay or soil respiration with increasing forest age, but there was an interaction between stand age and litter type which influenced both decomposition and soil respiration rates. Interestingly, soil respiration from the functionally diverse litter mixture was significantly higher in the younger than older forest stands, and the functionally diverse litter mixture decayed more rapidly than expected in one of the younger stands. Our findings highlight the potential importance of functionally diverse plant inputs, as well as the interaction between local environmental attributes and litter type, for soil C dynamics in tropical forests.

Chemical differences in cover crop residue quality are maintained through litter decay.

As plant litter decomposes, its mass exponentially decreases until it reaches a non-zero asymptote. However, decomposition rates vary considerably among litter types as a function of their overall quality (i.e., carbon:nitrogen (C:N) ratio and litter chemistry). We investigated the effects of hairy vetch (HV: Vicia villosa Roth):cereal rye (RYE: Secale cereale L.) biomass proportions with or without broadcasted poultry manure on overall litter quality before and during decomposition. As HV biomass proportions increased from 0 to 100%, the relative susceptibility of HV:RYE mixtures to microbial decomposition increased due to: (i) decrease in the initial C:N ratio (87:1 to 10:1 in 2012 and 67:1 to 9:1 in 2013), (ii) increase in the non-structural labile carbohydrates (33 to 61% across years), and (iii) decrease in the structural holo-cellulose (59 to 33% across years) and lignin (8 to 6% across years) fractions. Broadcasted poultry manure decreased the overall initial quality of HV-dominated litters and increased the overall initial quality of RYE-dominated litters. Across all HV:RYE biomass proportions with or without poultry manure, chemical changes during litter decay were related to proportional mass loss. Therefore, the relative decrease in carbohydrates and the concomitant increase in holo-cellulose and lignin fractions were more pronounced for fast decomposing litter types, i.e., litters dominated by HV rather than RYE. While our results suggest possible convergence of litter C:N ratios, initial differences in litter chemistry neither converged nor diverged. Therefore, we conclude that the initial chemistry of litter before decomposition exerts a strong control on its chemical composition throughout the decay continuum.

Long-term retention of carbon from litter decay in diverse agricultural soils in Canada and New Zealand

Identifying the primary regulators of plant litter decay in agricultural soils is important for understanding ecosystem function now and for managing post-harvest litter in a warmer world. We conducted a litter decay study at 11 sites in Canada and New Zealand with diverse soils and climates. We incorporated 13C-labelled barley litter into the surface 10 cm of soil and monitored amount remaining over 8–10 years; at five sites litter was also applied to the soil surface to simulate no-tillage. Our objectives were to evaluate litter decay as influenced by soil type, tillage practice, and environmental conditions, and quantify the most important factors controlling C retention in soil. Loss of C via decomposition occurred quickly – more than half was lost within 1 year and only about 5–12% remained at the end of the experiment. A double exponential decay model, based on temperature and developed from the first 5 years of the study, accurately described litter decay, but only after re-tuning using measurements from the full experimental period. Including precipitation in the model further improved its fit. Soil properties exerted minimal discernible influence on the amount of litter C remaining, implying that properties such as the amount and surface area of clay minerals, were less important than climate in limiting litter decay or enhancing retention of C in soil. Comparison of litter application treatments showed that no-till slowed decay of plant litter, but only for a short time (∼1 yr) and only in environments with a mean annual precipitation of <1000 mm. These findings have implications for the role of soils in climate mitigation. If only 10% of added plant litter C remains in soil beyond a few years, regardless of climate, residue placement, or soil type, then rates of soil gain are limited without substantive increases in residue inputs.

Warmer temperature promotes the contribution of invertebrate fauna to litter components release in an alpine meadow on the Qinghai-Tibetan Plateau

How warming and invertebrate fauna concurrently influence litter carbon and nutrient turnover in alpine meadow is still poorly known. Using a litterbag technique, we evaluated the effects of temperature (ambient temperature vs. warming temperature) × mesh (fine mesh without invertebrate fauna access vs. coarse mesh with invertebrate fauna access) on litter decay (i.e., carbon and nitrogen release, lignin and cellulose degradation) across two typical seasons (cold season vs. warm season) in an alpine meadow ecosystem on the Qinghai-Tibetan Plateau. Our results showed that the whole-soil-profile warming significantly increased litter cellulose degradation (+47%), but less affected the decay of other litter components (i.e., carbon, nitrogen, and lignin: + 7–18% increase). The loss of nitrogen and lignin from litter significantly increased by ca. 2 times in the presence of invertebrate fauna. Moreover, the release of all litter chemical components was significantly faster (by 1.5–5.2 times) in warm season than in cold season. Further, litter carbon release and lignin degradation rates were markedly influenced by the interacting effects of mesh × season, and mesh × temperature, respectively. Overall, these findings highlight the importance of invertebrate fauna as a commonly overlooked co-determinant of the warming effect on litter decay patterns in cold biomes; the changed release rates of litter components in the context of on-going warming may have far-reaching effects on carbon and nutrient cycling in alpine ecosystems.

Temperature sensitivity and decomposition rate of 101 leaf litter types from Mediterranean ecosystems

Litter decomposition is a fundamental process, and the number of published studies has steadily increased in recent decades. However, few experiments have systematically compared a large number of litter types and evaluated their temperature sensitivity. We conducted a two-year experiment on the decomposition of litter bags containing 101 leaf litter sampled in Mediterranean ecosystems and incubated under laboratory conditions at 4 °C, 14 °C, and 24 °C. Litter was chemically characterized and analysed for carbon (C), nitrogen (N), cellulose and lignin concentration, C/N, and lignin/N ratios, which serve as predictors of decomposition rate. The sensitivity of litter decay rate to temperature was evaluated using Q10. Leaf litter chemistry varied widely in nitrogen content (range 0.52–6.80 %), lignin content (range 1.53–49.31 %), C/N ratio (range 5.21–77.78), and lignin/N ratio (range 0.34–34.90). Litter decomposition rate was negatively related to initial lignin concentration, lignin/N ratio, and C/N ratio, but only in the early stage. In the late stages of decomposition, litter decay rate was negatively correlated with initial N concentration but positively correlated with C/N and lignin/N ratios. Temperature sensitivity was negatively correlated with N concentration and positively correlated with lignin and lignin/N ratio. It is noteworthy that, contrary to expectations, temperature sensitivity exhibited a hump-shaped relationship with decay rate. N, C/N, and lignin/N ratios should be used with caution because their predictive power is reversed with respect to decomposition rate during the decomposition process. In addition, the new finding that temperature sensitivity has a hump-shaped relationship with decomposition rate deserves further confirmation and could be considered in ecosystem-level organic C modeling.

Direction of Alliaria petiolata (garlic mustard) leachate's effect on early litter mass loss is dependent upon saprotrophic community composition

Differences between fungal and bacterial decomposition trajectories can be related to differences in sensitivity to nutrient input and to plant secondary metabolites. The invasive plant Alliaria petiolata (Beib. Cavara and Grande; garlic mustard) produces unique secondary metabolites (glucosinolates) capable of altering the functioning of root-associated communities. However, few studies explore whether these compounds can alter litter decomposition— a route for ecosystem-level impacts of garlic mustard invasion. This preliminary study investigated the potential for aqueous garlic mustard leachate to alter mass loss from tea litterbags in artificially fungal-dominant compared to intact soils (fungal and bacterial components) in laboratory microcosm incubations. Garlic mustard and native Acer saccharum (Marsh.; sugar maple) leachates stimulated fungal decomposition indistinguishably. In intact soils, garlic mustard suppressed mass loss relative to a water control and native leachate, though this later effect was only marginally significant. These results suggest the energetic benefit of labile carbon in garlic mustard leachate may exceed any negative effect of glucosinolates for fungal decomposers, but that bacteria were more sensitive to leachate toxicity and the inhibitory effects of high nutrient input. Overall, our results imply the direction of garlic mustard's effect on decomposition may depend on saprotrophic community composition and therefore the consequences for litter decay in garlic mustard invaded soils may be context-dependent.

Divergent Controls on Leaf and Root Litter Decay Linking to Soil C, N, and P Pools Under a Subtropical Land-use Change

Divergent Controls on Leaf and Root Litter Decay Linking to Soil C, N, and P Pools Under a Subtropical Land-use Change

Litter Deposition and Nutrient Cycling of Invaded Environments by Cryptostegia madagascariensis at Tropical Cambisols from Northeastern Brazil

Cryptostegia madagascariensis is an invasive plant species that covers 11% of the Brazilian northeastern territory, but its role on the litter trait in tropical ecosystems remains unclear. Here, we analyzed and compared the litter deposition, litter nutrient content, soil organic matter, and the litter decay rate from invaded and non-invaded environments by C. madagascariensis at a tropical Cambisol. The PCA analysis revealed that litter deposition, litter quality, and soil organic matter were correlated with the invaded environment. We grew plant species in greenhouse conditions to obtain a standard litter material to use in our litter bags in field conditions. We found that litter decay rate was higher in the invaded environment than in the non-invaded one. Our results suggest that C. madagascariensis changes litter traits in tropical ecosystems that in turn create negative plant–soil feedback to the native species by creating a physical barrier on soil surface and to promote its own rhizosphere.

Fungal community composition and genetic potential regulate fine root decay in northern temperate forests.

Understanding how genetic differences among soil microorganisms regulate spatial patterns in litter decay remains a persistent challenge in ecology. Despite fine root litter accounting for ~50% of total litter production in forest ecosystems, far less is known about the microbial decay of fine roots relative to aboveground litter. Here, we evaluated whether fine root decay occurred more rapidly where fungal communities have a greater genetic potential for litter decay. Additionally, we tested if linkages between decay and fungal genes can be adequately captured by delineating saprotrophic and ectomycorrhizal fungal functional groups based on whether they have genes encoding certain ligninolytic class II peroxidase enzymes, which oxidize lignin and polyphenolic compounds. To address these ideas, we used a litterbag study paired with fungal DNA barcoding to characterize fine root decay rates and fungal community composition at the landscape scale in northern temperate forests, and we estimated the genetic potential of fungal communities for litter decay using publicly available genomes. Fine root decay occurred more rapidly where fungal communities had a greater genetic potential for decay, especially of cellulose and hemicellulose. Fine root decay was positively correlated with ligninolytic saprotrophic fungi and negatively correlated with ECM fungi with ligninolytic peroxidases, likely because these saprotrophic and ectomycorrhizal functional groups had the highest and lowest genetic potentials for plant cell wall degradation, respectively. These fungal variables overwhelmed direct environmental controls, suggesting fungal community composition and genetic variation are primary controls over fine root decay in temperate forests at regional scales.