Decomposition Of Plant Material Research Articles

Differential response of bacteria and fungi to drought on the decomposition of Sarcocornia fruticosa woody stems in a saline stream

AbstractInland saline ecosystems suffer multiple stresses (e.g., high radiation, salinity, water scarcity) that may compromise essential ecosystem functions such as organic matter decomposition. Here, we investigated the effects of drought on microbial colonization and decomposition of Sarcocornia fruticosa woody stems across different habitats in a saline watershed: on the dry floodplain, submerged in the stream channel and at the shoreline (first submerged, then emerged). Unexpectedly, weight loss was not enhanced in the submerged stems, while decomposition process differed between habitats. On the floodplain, it was dominated by fungi and high cellulolytic activity; in submerged conditions, a diverse community of bacteria and high ligninolytic activity dominated; and, on the shoreline, enzyme activities were like submerged conditions, but with a fungal community similar to the dry conditions. Results indicate distinct degradation paths being driven by different stress factors: strong water scarcity and photodegradation in dry conditions, and high salinity and reduced oxygen in wet conditions. This suggests that fungi are more resistant to drought, and bacteria to salinity. Overall, in saline watersheds, variations in multiple stress factors exert distinct environmental filters on bacteria and fungi and their role in the decomposition of plant material, affecting carbon cycling and microbial interactions.

Degradation of lignocellulose by fungi based on differential equation

In this paper, we studied the decomposition of plant materials and lignocellulosic fibers by fungi, and the relationship between some characteristics of fungi. And established several mathematical models to solve the problems raised in the problem. Firstly, in the case of the coexistence of different fungi, ignoring the interaction between them, we use differential equation and Monod equation to establish the model. In the model, the decomposition rate of each fungus to plant materials and lignocellulosic fibers at a different time and the mycelial elongation rate of the fungus itself can be obtained. In the model solving, the ode instruction is used to solve the differential equations, and the variable step Runge Kutta Feldberg method is used to improve the accuracy. Then we considered the interactions between different fungi: mutual promotion and mutual inhibition. Different fungi have different moisture tolerance, so they have different decomposition rates of plant materials and wood fibers. By using logistic law, our model can describe the decomposition ability of different interactions between fungi to decompose lignocellulosic fibers. After solving the model, it is found that the fungi that promote each other are the fastest, the fungi that do not affect each other are the second, and the fungi that inhibit each other are the slowest, that is, the decomposition rate is the smallest.

Agricultural farming intensification significantly reduced earthworm abundance and diversity in Usangu agro-ecosystems, Tanzania

Earthworms an ecologically important group of invertebrates that are crucial to delivery of many ecosystem services, but also considered ecosystem engineers playing an important role in soil fertility and land productivity. Earthworms facilitate breakdown and decomposition of plant and animal materials releasing plant nutrients. Earthworm burrows allow air and water movement in the soil but also improve soil fertility and drainages. Earthworm population in agricultural soils is influenced by different factors i.e., tillage, farming activities, soil chemistry as well as chemical contaminants. Agricultural (paddy farming) intensification with increased and excessive use of agrochemicals (fertilizers, pesticides, and herbicides) may affect earthworm population in agricultural soils. Recently, there scant studies conducted to characterize earthworm abundance and diversity in Tanzania's agro-ecosystem. Therefore, the present study characterized earthworm population in agricultural soils of contrasting intensification in Usangu agro-ecosystem (UA) to understand influence of current land use on earthworm abundance and their diversity as they have a vital role in agro-ecosystem productivity and sustainability. This study found that current paddy farming and associated activities in UA negatively affect earthworm occurrence, distribution, and diversity. Where only four dominant earthworm species were determined (Apporectodea caliginosa (endogeic), Lumbricus terrestris (Anecic), Pontoscolex corentrurus (endogeic), Fimoscolex sporadochactus (Anecic)) compared to other tropical areas. But also, highly intensified paddy farming areas (i.e., Chimala, Igalako, Ihahi, Kapunga, Mahongole, and Uturo) were observed to have earthworm abundance <25 individuals/m2 an FAO recommended earthworm count/m2 in healthy soils compared to less intensified schemes (25-40 earthworm/m2). The earthworm abundance and biomass determined in UA was below global average of 78 individuals per m2 and 150 g/m2, indicating that UA is in deteriorating quality. Thus, current farming practices creates unfavourable environmental conditions which likely leads to migration of earthworm to other land use or death due to harsh environment created. High earthworm abundance and biomass improve land productivity via nutrient recycling, thus low earthworm counts and diversity in UA likely to threaten agro-ecosystem sustainability. The present study provides baseline information on earthworm abundance and their diversity in UA and Tanzania.

Plant material decomposition and bacterial and fungal communities in serpentine and karst soils of Japanese cool-temperate forests

ABSTRACT We aimed to reveal the plant material decomposition rate and abundance of bacteria and fungi in serpentine and karst sites of cool-temperate forests. Given the relatively higher soil pH, we hypothesized a higher decomposition rate of cellulose, lower decomposition rate of lignin-containing plant materials, and lower fungi-to-bacteria ratio in serpentine and karst sites than in neighboring non-serpentine/non-karst sites. This study was conducted on serpentine and mudstone sites in deciduous oak forests on Mount Oe and karst and sandstone sites on Mount Ibuki, Japan. We performed a decomposition experiment over 5 months using three chemically distinct materials: cellulose filter, lignin-containing coffee filter, and green tea leaves. These common materials enabled us to compare the in-situ utilization of different carbon substrates by microbial communities between sites. The abundance of bacteria and fungi and their ratio in topsoils and materials that decomposed for 1 month were assessed using quantitative PCR. In contrast to our hypothesis, the decomposition rate was higher in the mudstone site for cellulose and did not differ for the coffee filter compared to the serpentine site. Green teas with higher lignin content than coffee filters decomposed slower at the serpentine site only during the early period of decomposition. The serpentine site showed higher fungi-to-bacteria ratios in the decomposed materials and soil. The karst site also showed different decomposition patterns than our prediction, presenting no clear difference in the cellulose filter compared to the sandstone site. In the karst site, coffee filters decomposed faster at the early period; however, green teas decomposed slower as we expected, especially at the later period of decomposition. The karst site had a lower fungi-to-bacteria ratio in the topsoil, but similar fungi-to-bacteria ratios in the decomposed materials compared with the sandstone site. Our results suggest that the decomposition patterns in the serpentine and karst soils are not simply predicted based on soil pH and other distinct characteristics (e.g., soil moisture content and heavy metal concentration) would more strongly contribute to decomposition and microbial community composition in the study mountains.

Soil carbon storage is related to tree functional composition in naturally regenerating tropical forests.

Regenerating tropical forests are increasingly important for their role in the global carbon cycle. Carbon stocks in above-ground biomass can recover to old-growth forest levels within 60-100 years. However, more than half of all carbon in tropical forests is stored below-ground, and our understanding of carbon storage in soils during tropical forest recovery is limited.Importantly, soil carbon accumulation does not necessarily reflect patterns in above-ground biomass carbon accrual during secondary forest succession, and factors related to past land use, species composition and soil characteristics may influence soil carbon storage during forest regrowth.Using tree census data and a measure of tree community shade tolerance (species-specific light response values), we assessed the relationship between soil organic carbon stocks and tree functional groups during secondary succession along a chronosequence of 40- to 120-year-old naturally regenerating secondary forest and old-growth tropical forest stands in Panama.While previous studies found no evidence for increasing soil C storage with secondary forest age, we found a strong relationship between tree functional composition and soil carbon stocks at 0-10cm depth, whereby carbon stocks increased with the relative influence of light-demanding tree species. Light demanding trees had higher leaf nitrogen but lower leaf density than shade-tolerant trees, suggesting that rapid decomposition of nutrient-rich plant material in forests with a higher proportion of light-demanding species results in greater accumulation of carbon in the surface layer of soils. Synthesis. We propose that soil carbon storage in secondary tropical forests is more strongly linked to tree functional composition than forest age, and that the persistence of long-lived pioneer trees could enhance soil carbon storage as forests age. Considering shifts in tree functional groups could improve estimates of carbon sequestration potential for climate change mitigation by tropical forest regrowth. Read the free Plain Language Summary for this article on the Journal blog.

Bacterial species metabolic interaction network for deciphering the lignocellulolytic system in fungal cultivating termite gut microbiota

Fungus-cultivating termite Odontotermes badius developed a mutualistic association with Termitomyces fungi for the plant material decomposition and providing a food source for the host survival. The mutualistic relationship sifted the microbiome composition of the termite gut and Termitomyces fungal comb. Symbiotic bacterial communities in the O. badius gut and fungal comb have been studied extensively to identify abundant bacteria and their lignocellulose degradation capabilities. Despite several metagenomic studies, the species-wide metabolic interaction patterns of bacterial communities in termite gut and fungal comb remains unclear. The bacterial species metabolic interaction network (BSMIN) has been constructed with 230 bacteria identified from the O. badius gut and fungal comb microbiota. The network portrayed the metabolic map of the entire microbiota and highlighted several inter-species biochemical interactions like cross-feeding, metabolic interdependency, and competition. Further, the reconstruction and analysis of the bacterial influence network (BIN) quantified the positive and negative pairwise influences in the termite gut and fungal comb microbial communities. Several key macromolecule degraders and fermentative microbial entities have been identified by analyzing the BIN. The mechanistic interplay between these influential microbial groups and the crucial glycoside hydrolases (GH) enzymes produced by the macromolecule degraders execute the community-wide functionality of lignocellulose degradation and subsequent fermentation. The metabolic interaction pattern between the nine influential microbial species has been determined by considering them growing in a synthetic microbial community. Competition (30%), parasitism (47%), and mutualism (17%) were predicted to be the major mode of metabolic interaction in this synthetic microbial community. Further, the antagonistic metabolic effect was found to be very high in the metabolic-deprived condition, which may disrupt the community functionality. Thus, metabolic interactions of the crucial bacterial species and their GH enzyme cocktail identified from the O. badius gut and fungal comb microbiota may provide essential knowledge for developing a synthetic microcosm with efficient lignocellulolytic machinery.

Conservation management and termites: a case study from central Côte d’Ivoire (West Africa)

AbstractTermites are essential components of tropical ecosystems, in which they provide fundamental ecosystem services, such as decomposition of dead plant material, fostering of soil mineralization and provisioning of new microhabitats. We investigated the termite communities of four habitats in two protected areas in West Africa, which differ in management effectiveness: the strictly protected Lamto Reserve (LR) and the Marahoué National Park (MNP), which suffers from anthropogenic disturbance despite its protection status. We tested the effect of disturbance on species composition, richness and abundance as well as on functional (feeding type) composition. The effect of disturbance was clearly visible in the termite communities. Compared to the LR, the MNP had less termite species overall and in all habitats except the shrub savannah. Also the abundance of termites was generally reduced and a decrease of soil feeders recorded. The latter is well-known to be sensitive to anthropogenic disturbance in forests. Comparing our results with other studies, we were able to identify suitable bioindicators of ecosystem health for West-African savannahs. Furthermore, we discuss the potential consequences of anthropogenic disturbance on ecosystem services provided by termites.

Ecuadorian Coptoborus beetles harbor Fusarium and Graphium fungi previously associated with Euwallacea ambrosia beetles

ABSTRACT Ambrosia beetles from the scolytine tribe Xyleborini (Curculionidae) are important to the decomposition of woody plant material on every continent except Antarctica. These insects farm fungi on the walls of tunnels they build inside recently dead trees and rely on the fungi for nutrition during all stages of their lives. Such ambrosia fungi rely on the beetles to provide appropriate substrates and environmental conditions for growth. A small minority of xyleborine ambrosia beetle–fungal partnerships cause significant damage to healthy trees. The xyleborine beetle Coptoborus ochromactonus vectors a Fusarium (Hypocreales) fungus that is lethal to balsa (Ochroma pyramidale (Malvaceae)) trees in Ecuador. Although this pathogenic fungus and its associated beetle are not known to be established in the United States, several other non-native ambrosia beetle species are vectors of destructive plant diseases in this country. This fact and the acceleration of trade between South America and the United States demonstrate the importance of understanding fungal plant pathogens before they escape their native ranges. Here we identify the fungi accompanying Coptoborus ambrosia beetles collected in Ecuador. Classification based ribosomal internal transcribed spacer 1 (ITS) sequences revealed the most prevalent fungi associated with Coptoborus are Fusarium sp. and Graphium sp. (Microascales: Microascaceae), which have been confirmed as ambrosia fungi for xyleborine ambrosia beetles, and Clonostsachys sp. (Hypocreales), which is a diverse genus found abundantly in soils and associated with plants. Phylogenetic analyses of the Fusarium strains based on ITS, translation elongation factor (EF1-α), and two subunits of the DNA-directed RNA polymerase II (RPB1 and RPB2) identified them as Fusarium sp. AF-9 in the Ambrosia Fusarium Clade (AFC). This Fusarium species was previously associated with a few xyleborine ambrosia beetles, most notably the species complex Euwallacea fornicatus (Eichhoff 1868) (Curculionidae: Scolytinae: Xyleborini). Examination of ITS and EF1-α sequences showed a close affinity between the Graphium isolated from Coptoborus spp. and other xyleborine-associated Graphium as well as the soil fungus Graphium basitruncatum. This characterization of ambrosia fungi through DNA sequencing confirms the identity of a putative plant pathogen spread by Coptoborus beetles and expands the documented range of Fusarium and Graphium ambrosia fungi.

Использование активности ферментов для диагностики последствий фумигации дымом почв

Abstract As a result of fires, in addition to the fire itself and high temperatures, smoke from combustion products has a significant effect on the biota. The aim of the work was to assess the effect of fumigation with combustion products of plant origin on the biology activity of ordinary chernozem. In a series of model experiments, the reaction of soil enzymes (catalase, peroxidase, polyphenol oxidase, invertase, urease, phosphatase) to the smoke of the studied soil with products of thermal decomposition of plant materials (foliage, needles, straw, wood chips) is shown. A significant decrease in the enzyme activity of the studied enzymes was revealed in the range from 7% to 33%, depending on the time spent under the smoke of chernozem (15–120 minutes). The highest sensitivity to fumigation was noted for enzymes of the class of oxidoreductases: catalase, polyphenoloxidase, and peroxidase. Thus, a significant sensitivity and information content of the indicators of the enzyme activity of soils on the effect of smoke has been established, which can be used in monitoring the consequences of fires. Keywords: PYROGENIC EFFECTS, WILDFIRE, COMBUSTION PRODUCTS, CHERNOZEM, BIOLOGY ACTIVITY

Soil organic matter turnover rates increase to match increased inputs in grazed grasslands

Managed grasslands have the potential to store carbon (C) and partially mitigate climate change. However, it remains difficult to predict potential C storage under a given soil or management practice. To study C storage dynamics due to long-term (1952–2009) phosphorus (P) fertilizer and irrigation treatments in New Zealand grasslands, we measured radiocarbon (14C) in archived soil along with observed changes in C stocks to constrain a compartmental soil model. Productivity increases from P application and irrigation in these trials resulted in very similar C accumulation rates between 1959 and 2009. The ∆14C changes over the same time period were similar in plots that were both irrigated and fertilized, and only differed in a non-irrigated fertilized plot. Model results indicated that decomposition rates of fast cycling C (0.1 to 0.2 year−1) increased to nearly offset increases in inputs. With increasing P fertilization, decomposition rates also increased in the slow pool (0.005 to 0.008 year−1). Our findings show sustained, significant (i.e. greater than 4 per mille) increases in C stocks regardless of treatment or inputs. As the majority of fresh inputs remain in the soil for less than 10 years, these long term increases reflect dynamics of the slow pool. Additionally, frequent irrigation was associated with reduced stocks and increased decomposition of fresh plant material. Rates of C gain and decay highlight trade-offs between productivity, nutrient availability, and soil C sequestration as a climate change mitigation strategy.

Biochemistry of methanol-dependent acetogenesis in Eubacterium callanderi KIST612.

Methanol is the simplest of all alcohols, is universally distributed in anoxic sediments as a result of plant material decomposition and is constantly attracting attention as an interesting substrate for anaerobes like acetogens that can convert bio-renewable methanol into value-added chemicals. A major drawback in the development of environmentally friendly but economically attractive biotechnological processes is the present lack of information on biochemistry and bioenergetics during methanol conversion in these bacteria. The mesophilic acetogen Eubacterium callanderi KIST612 is naturally able to consume methanol and produce acetate as well as butyrate. To grasp the full potential of methanol-based production of chemicals, we analysed the genes and enzymes involved in methanol conversion to acetate and identified the redox carriers involved. We will display a complete model for methanol-derived acetogenesis and butyrogenesis in Eubacterium callanderi KIST612, tracing the electron transfer routes and shed light on the bioenergetics during the process.

Hydrodynamics affect plant traits in estuarine ecotones with impact on carbon sequestration potentials

Estuaries are highly productive ecosystems that play an important role in carbon fixing. The amount of carbon fixed by temperate brackish marshes depends, among others, on the biomass produced, its decomposition and the organic carbon stored in the soil. Here, we assumed that the functional trait composition of the vegetation both responded to environmental drivers and affected production, decomposition rate of native biomass and soil organic carbon, in addition to direct links between environmental drivers and these ecosystem properties. We tested a set of detailed hypotheses with a partial least squares structural equation model and quantified wave height, inundation period, salinity, soil nutrients, species abundances and as traits the leaf area, specific leaf area, stem bending properties and investment per plant organ, as well as above-ground standing biomass, decomposition rates of native and control biomass (hay) and soil organic carbon (SOC).There was no direct relationship between environmental drivers and ecosystem properties, except with the decomposition of control hay. All other linkages involved the functional composition of the vegetation. Increasing inundation period simultaneously decreased plants traits like stem stiffness, leaf area, specific leaf area and mass fraction of stems and leaves, which were aggregated in a new trait ‘aboveground module’. Total plant biomass decreased in communities on higher elevations with reduced wave height. Here, increased investment in the aboveground trait module resulted in higher aboveground community biomass and SOC but decreased the decomposition of native plant material, which in turn was higher in the low lying vegetation zones. Increasing total plant biomass also increased SOC, but not aboveground community biomass. Both the aboveground trait module and total plant biomass were response and effect traits, by responding to the environmental drivers and affecting carbon related ecosystem properties.At lower elevation with higher inundation and higher wave height, SOC was lower than the product of standing biomass and decomposition rate, which could be a proxy of the expected SOC. This may indicate an export of dead plant material to higher elevations or further downstream.Due to sea level rise, the area of estuarine vegetation may decrease because a fixed dike line along the river prevents landward migration, which can reduce the amount of biomass produced and with it the potential to store SOC. Restoration of the tidal marshes or realignment of the dikes may be necessary to protect the ecosystem properties and services of estuarine vegetation.

Potentially peat‐forming biomass of fen sedges increases with increasing nutrient levels

Abstract Peat formation is a key carbon sequestration process in the terrestrial biosphere. In temperate fens, peat is mainly formed by below‐ground biomass of vascular plants. Nutrient availability in temperate fens is naturally variable, and nowadays increasing due to atmospheric deposition, runoff from agriculture and mineralization of peat caused by drainage. To maintain or restore peat formation, it is important to understand how increased nutrient availability influences the main controls of peat formation, that is, below‐ground biomass production and decomposition. We investigated above‐ and below‐ground biomass production and decomposition of five fen sedges (Carex spp.) grown under 12 different nutrient levels (realized with nitrogen amounts increasing exponentially across levels, with addition of phosphorous and potassium to ensure nitrogen limitation in each nutrient level) in a mesocosm experiment, designed to resemble a gradient of very low to very high nutrient availabilities in temperate fens. In addition, we measured nutrient stoichiometry in the biomass and related this to possible growth limitations and to root decomposition. Our results indicate that higher biomass production at higher nutrient levels was not offset by an increase in decomposition. Increase of above‐ and below‐ground biomass with higher nutrient levels was species‐specific. Decomposition of standardized plant material in mesocosms was not dependent on the species growing in the mesocosms and showed only slight, if any, variation with differing nutrient levels. Decomposition of roots grown under different nutrient levels was mainly correlated with species identity and root lignin:cellulose ratio. Our study suggests that the Carex spp. potentially peat‐forming root biomass, here defined as the root biomass which is not decomposed during one growing season, increases with increasing nutrient levels: higher root biomass production is not counteracted by increasing decomposition during the growing season. Based on this pattern of positive mass balance in five common sedge species with differing growth characteristics, we propose that sedge communities establishing after rewetting have the potential for renewed peat formation regardless of the prevailing trophic level. A free Plain Language Summary can be found within the Supporting Information of this article.

Fungal growth model based on logistic regression

The decomposition of plant materials and wood fibers is an important part of the carbon cycle, and some of the key components of this decomposition are fungi. Our aim was to explore the relationship between the rate of decomposition and the growth rate and moisture tolerance of a variety of fungi. The logistic growth model of a single fungus was established to explore its growth mechanism, and the influencing factors of humidity and temperature were introduced to modify it.

Study on fungal life activities of decomposing wood fibers

The decomposition of plant material and woody fibers is a key component in the carbon cycle. In the whole process, fungi are the key factor to decompose wood fiber. A recent research indicates that there is a certain relationship between fungi traits that determine the decomposition rate. Based on the results of the research, our team construct a mathematical model to simulate the decomposition of ground litter and woody fibers in the presence of a variety of fungi and explore the decomposition under the condition of interaction, different environment, change of environment and biodiversity.In this paper, we start by analyzing the experimental data in the reference of the MCM problem A and we use the cluster analysis method to divide the fungi in the data into two groups according to the growth rate, competitiveness and environmental tolerance. Then on the basis of topic requirements, we construct our decomposition model that the decomposition rate of fungi per millimeter is only related to the growth rate of fungi population and the moisture tolerance of fungi and this relationship is linear. We use our decomposition model to add up the decomposition effects of the two types of fungi. Our conclusion is that the decomposition rate of fungal community was the sum of the decomposition rates of each fungal population.

Electrostatic spraying of imazamox to control the floating aquatic plant Salvinia molesta and its effects on environmental indicators of water quality

This study aimed to assess, in a microcosm condition, the efficacy of electrostatic spraying of herbicide imazamox in the control of Salvinia molesta and the effects of decomposition of plant material on water quality. The herbicide rates used were 600, 700, 800, and 900 g ai ha−1 and spray volume of 50 L ha−1 in electrostatic application. Control effectiveness was assessed at 7, 15, 30, 45, and 60 days after application (DAA), expressed in percentage (0–100%) of visible injury symptoms in the plants, biochemical oxygen demand (BOD5), chemical oxygen demand (COD), chlorophyll a and pheophytin a contents at 0, 7, 15, 30, 45, and 60 DAA, and fresh and dry biomass at 60 DAA. Imazamox was effective in controlling 63% of S. molesta with 900 g ai ha−1 in 45 DAA and 30% with 800 g ai ha−1 in 30 DAA, and reduced 82.3% and 17.5% of fresh weight and 62.6% and 9.3% of dry weight of plant at 60 DAA, respectively. The imazamox spray reduced chlorophyll a with all doses applied and increased BOD5 in 45 DAA with 900 g ai ha−1 and COD in all assessment periods, but for temperature, dissolved oxygen, electrical conductivity, and pH, there was no significant effect after spraying. The herbicide imazamox reduced S. molesta plants with 900 g ai ha−1, without causing significant effects on environmental indicators of water quality. Electrostatic spraying of herbicide can be used in management strategies of aquatic plants to reduce plant density in water bodies and maintain the colonization of plants at a level not harmful to the aquatic biota.

Multipartite symbioses in fungus-growing termites (Blattodea: Termitidae, Macrotermitinae) for the degradation of lignocellulose.

Fungus-growing termites are among the most successful herbivorous animals and improve crop productivity and soil fertility. A range of symbiotic organisms can be found inside their nests. However, interactions of termites with these symbionts are poorly understood. This review provides detailed information on the role of multipartite symbioses (between termitophiles, termites, fungi, and bacteria) in fungus-growing termites for lignocellulose degradation. The specific functions of each component in the symbiotic system are also discussed. Based on previous studies, we argue that the enzymatic contribution from the host, fungus, and bacteria greatly facilitates the decomposition of complex polysaccharide plant materials. The host-termitophile interaction protects the termite nest from natural enemies and maintains the stability of the microenvironment inside the colony.

Habitat components and population density drive plant litter consumption by Eudrilus eugeniae (Oligochaeta) under tropical conditions.

The ingestion of organic and mineral materials by earthworms is a prominent functional role that has profound consequences for the decomposition and stabilization of soil organic matter. To investigate the litter consumption of the African nightcrawler earthworm Eudrilus eugeniae under different tropical conditions, we used DNA barcoding to identify specimens of E.eugeniae collected from sites across the Adamawa region in Cameroon, and studied the influence of habitat suitability (soil properties), soil moisture, litter type, and population density on litter consumption. A total of four litter consumption experiments were carried out using soils collected from refuse disposal sites, agricultural lands, and savannahs dominated by the Mexican sunflower Tithonia diversifolia. The results revealed that litter consumption significantly increased in the refuse disposal and agricultural soils as opposed to the Mexican sunflower (T. diversifolia) soil, a cow dung enriched substrate, and a sterile soil horizon from the savannah (P < 0.05). The optimum moistures for litter consumption were between 24% and 50%. Litter type did not affect the consumption rate of the earthworms (P > 0.05). We observed a general positive density-dependent consumption with litter mass loss increasing with increasing density. Our results suggest that E.eugeniae has a strong direct effect on the decomposition of plant materials than expected from previous estimations, and that litter consumption rates are determined by several habitat components and population density.

Microbial processing of plant remains is co-limited by multiple nutrients in global grasslands.

Microbial processing of aggregate-unprotected organic matter inputs is key for soil fertility, long-term ecosystem carbon and nutrient sequestration and sustainable agriculture. We investigated the effects of adding multiple nutrients (nitrogen, phosphorus and potassium plus nine essential macro- and micro-nutrients) on decomposition and biochemical transformation of standard plant materials buried in 21 grasslands from four continents. Addition of multiple nutrients weakly but consistently increased decomposition and biochemical transformation of plant remains during the peak-season, concurrent with changes in microbial exoenzymatic activity. Higher mean annual precipitation and lower mean annual temperature were the main climatic drivers of higher decomposition rates, while biochemical transformation of plant remains was negatively related to temperature of the wettest quarter. Nutrients enhanced decomposition most at cool, high rainfall sites, indicating that in a warmer and drier future fertilized grassland soils will have an even more limited potential for microbial processing of plant remains.

Biotransformation of Monocyclic Phenolic Compounds by Bacillus licheniformis TAB7.

Bacillus licheniformis strain TAB7 is a bacterium used as a commercial deodorizing agent for compost in Japan. In this work, its ability to biotransform the following monocyclic phenolic compounds was assessed: ferulate, vanillate, p-coumarate, caffeate, protocatechuate, syringate, vanillin, and cinnamate (a precursor for some phenolic compounds). These compounds are abundant in composting material and are reported to have allelopathic properties. They come from sources such as plant material decomposition or agro-industrial waste. Biotransformation assays were carried out in LB supplemented with 0.2 mg/mL of an individual phenolic compound and incubated for up to 15 days followed by extraction and HPLC analysis. The results showed that TAB7 could biotransform ferulate, caffeate, p-coumarate, vanillate, protocatechuate, and vanillin. It, however, had a poor ability to transform cinnamate and syringate. LC-MS/MS analysis showed that ferulate was transformed into 4-vinylguaiacol as the final product, while caffeate was transformed into 4-ethylcatechol. TAB7 genome analysis suggested that, while TAB7 may not mineralize phenolic compounds, it harbored genes possibly encoding phenolic acid decarboxylase, vanillate decarboxylase, and some protocatechuate degradation pathway enzymes, which are involved in the catabolism of phenolic compounds known to have negative allelopathy on some plants. The results thus suggested that TAB7 can reduce such phenolic compounds in compost.