Faster Decomposition Rates Research Articles

Geomorphically mediated carbon dynamics of floodplain soils and implications for net effect of carbon erosion

AbstractThe fate of organic carbon deposited in floodplain sediments is an important control on the magnitude and direction of the carbon flux from anthropogenically accelerated erosion and channelization of the riverine network. Globally, carbon deposition rates and mean residence time (MRT) within different geomorphic settings remains poorly constrained. We sampled soil profiles to 0.8 m depth from two geomorphic zones: active channel belt (ACB) and lowland floodplain, under long‐term pasture adjacent to the river Culm in SW England, UK. We evaluated sedimentation rates and carbon storage using fallout radionuclide 137Cs, particle size and total carbon analyses. Variation in decomposition was assessed via empirical (soil aggregate size, density fractionation combined with natural abundance 13C analysis) and modelling simulation (using the RothC model and catchment implications explored using a floodplain evolution model). Sedimentation and carbon accumulation rates were 5–6 times greater in the ACB than the floodplain. Carbon decomposition rates also varied with geomorphic setting. In floodplain cores, faster decomposition rates were indicated by greater 13C‐enrichment and subsoils dominated by mineral‐associated soil organic carbon. Whereas, in the ACB, carbon was less processed and 13C‐depleted, with light fraction and macroaggregate‐carbon throughout the cores, and RothC modelled decomposition rates were 4‐fold less than lowland floodplain cores. Including the ACB in floodplain carbon MRT calculations increased overall MRT by 10%. The major differences in the balance of sedimentation and decomposition rates between active and inactive floodplains suggests the relative extent of these contrasting zones is critical to the overall carbon balance. Restoration projects could enhance soil carbon storage by maximizing active floodplain areas by increasing river channel complexity.

Carbon sequestration potential in croplands in Lesotho

Soil organic carbon (SOC) plays a crucial role in physical, chemical and biological soil properties and maintains the sustainability of cropping systems. However, SOC stocks in croplands decline due to lower carbon inputs and faster decomposition rates. Therefore, sustainable soil management (SSM) practices are crucial to replenish the carbon inputs. Mapping carbon (C) stocks and sequestration potential allows determination of SOC stock level and identifies potential areas for improvement in Lesotho. The quantile random forest model determined SOC stock spatial distribution for top 0 to 30 cm. Soil data from 161 profiles and environmental covariates were used to predict SOC concentration, bulk density, and coarse fragments, which together with soil depth, helped determine SOC stock density averaging 64.76±25.59 Mg C ha−1. The SOC stock was used as an input in SOC potential determination. Then, SOC sequestration potential was determined using soil, management and climate layers as inputs in the Rothamsted Carbon model (RothC) for three SSM practices and business-as-usual (BAU). For BAU, SSM1, SSM2 and SSM3, 0, 5, 10 and 20% carbon inputs were added respectively. The attainable SOC stocks after 20 years were 67.02, 67.76, 68.49 and 69.65 Mg C ha−1, with uncertainty of 22.69 and 26.13% for BAU and respective SSM scenarios. Despite the projections showing annual mean gain of SOC stocks for BAU of 0.11 Mg C ha−1 per year, there are losses in other regions. Thus, as shown that in SSM the losses are reduced while the gains increase, their use is advised. The establishment of research areas which can be used for monitoring SOC stock levels and research on SSM are a major priority.

The Role of Shade Trees in Coffee Production Systems: The Case of Yayo District, Ilubabora Zone, Oromiya Region, Southwest Ethiopia

Coffee is one of the world’s most important crops given the highest number of people living directly or indirectly from it. Farmers have an excellent local knowledge about different tree species which are either retained or planted on their farms. The main purpose of this study was to investigate coffee growers’ local knowledge on the roles of shade trees in coffee production systems at Yayo District in Ilubabor Zone Southwest part of Ethiopia. A total of 120 (20 key informants and 100 households) participated in interview. Data were collected by using semi structured interview and field observation. The data were analyzed by preference ranking, direct matrix and using descriptive statistics. A total of 20 most commonly used coffee shade tree species belonging to 16 genera and 7 families were identified in the study area. Fabaceae was the most species rich plant family followed by Euphorbiaceae and Moraceae .The coffee farmers in the study area are mentioned benefits of the shade trees such as for improvement of soil fertility and moisture, to protect from unsuitable environmental stress, for longer life span of coffee plants, reducing erosion, increase coffee yields and quality, and reduce weed and grasses. Among shade tree species best compatible with coffee plant such as Albizia gummifera, Acacia abyssinica, Albizia schimmperia, Millitia ferruginea, Albizia grandibracteata ,Cordian africana and least were Corton macrostachyus were highly favored in that order. However, farmers considered as preferred coffee shade trees species by characteristics were mainly based on tree height, fast decomposition rate, small deciduous compound leaves, and umbrella crown shape and root depth. Coffee farmers of the study area managed their owned shade tree species through pruning, mulching and composting, thinning, weeding and hoeing and debarking and intercropping operations. To agreement endorsement of the extension of coffee shade agroforestry knowledge, the rural households must participate in pieces of training to improve their productivity and maximize the benefits of coffee shade in coffee production system.

Comparison of Callery pear (Pyrus calleryana, Rosaceae) leaf decomposition rates with those of the invasive shrub Amur honeysuckle (Lonicera maackii, Caprifoliaceae) and two native trees, red maple (Acer rubrum, Sapindaceae) and American sycamore (Platanus occidentalis, Platanaceae)1

Invasive plants can alter nutrient cycling rates, because the leaves of many invasive species decay more quickly than those of native plants. Pyrus calleryana (Callery pear) is a relatively new woody invader in the eastern USA that rapidly colonizes open and disturbed areas. Invasive woody plants can alter forest nutrient cycling, yet the leaf decomposition rates of P. calleryana have not been previously determined. In this study, Pyrus calleryana leaf decomposition rates were compared against two widely distributed native trees, Acer rubrum (red maple) and Platanus occidentalis (American sycamore), with different levels of nitrogen (N), carbon (C):N, lignin, and lignin:N. It was also compared to that of the invasive shrub Amur honeysuckle (Lonicera maackii), which is known to have very fast decomposition rates. Litter bags were placed in four locations in a Callery pear-dominated stand in northern Kentucky in November 2014 and sampled at 3, 90, 12, and 18 mo. Dry weight and %N measurements were fit to a single exponential decay equation. Mass and N loss of P. calleryana leaf litter were both similar to those of A. rubrum, and they were lower than those of L. maackii; however, lignin and lignin:N levels were most similar to L. maackii. Platanus occidentalis decayed very slowly and immobilized rather than mineralized N. Pyrus calleryana is thus not predicted to greatly alter leaf litter decomposition in invaded forests, although litter decomposition dynamics might be different in mixtures with native species and in other locations.

No Difference in Instream Decomposition Among Upland Agricultural and Forested Streams in Kenya

Expansion of agriculture is particularly worrying in tropical regions of the world, where native forests have been replaced by croplands and grasslands, with severe consequences for biodiversity conservation and ecosystem functioning. However, limited data exist on the effects of agriculture on the functioning of tropical streams. We conducted a leaf litter decomposition experiment in coarse- and fine-mesh litterbags using the three species of leaves (Eucalyptus globulus [non-native], Vernonia myriantha, and Syzygium cordatum [indigenous]) in three forested and agricultural streams to determine the effect of agriculture on instream leaf litter decomposition in headwater stream sites. We also examined the functional composition of macroinvertebrates in the streams through the contents of benthic kick samples. Agricultural streams had a less dense riparian canopy and smaller abundance of coarse organic particulate matter, and higher electric conductivity and suspended solids than forested streams. In terms of the effects of litter quality on decomposition rates, Vernonia had the fastest decomposition rates while Eucalyptus had the slowest in both forested and agricultural sites. Shredder invertebrates were less abundant in agricultural streams, and in both stream types, they were less diverse and abundant than other functional groups. Overall, leaf litter decomposition rates did not respond to agricultural land-use. The hypothesized negative effects of agriculture on organic matter processing were minimal and likely modulated by intact riparian zones along agricultural streams.

Variations in leaf litter decomposition explain invasion success of Broussonetia papyrifera over confamilial non-invasive Morus alba in urban habitats

In urban environments, anthropogenic influences play an important role in determining the distribution of woody flora and consequently, the propagation of woody invaders. Land-use changes and disturbances associated with urbanization may intensify different invasive aspects of a species. Studying the extent by which invasive species vary from non-invasive species can strengthen our understanding of urban invasions. In this study, we compared leaf litter decomposition between two confamilial exotics, an invasive Broussonetia papyrifera, and a non-invasive Morus alba (both belonging to family Moraceae), growing in urban habitats. Senescent leaves of both the species and soil were collected from five study sites in Chandigarh, India. Litterbags filled with 10 g leaves each were placed in pots containing the soil collected from respective study sites. Mass remaining, decomposition constant, and soil elemental composition were determined after periodic harvesting of the pots. Decomposition was completed within 180 days in B. papyrifera and 330 days in M. alba. Initially, the decomposition rate was low in B. papyrifera; however, a rapid degradation occurred after 90 days. Species, time, and their interaction significantly affected most of the elements in soil, whereas the effect of habitat was not significant. The faster decomposition rate in B. papyrifera may result in greater turnover of nutrients over a shorter time span, thereby, favoring its colonization in the invaded regions. The difference in litter decomposition process explains the invasion success of B. papyrifera over its confamilial species, M. alba, in urban habitats.

Preliminary Study on Water Bodies’ Effects on the Decomposition Rate of Goldenrod Litter

Leaf-litter input constitutes a major load in natural waters; therefore, to achieve and maintain high water quality, it is important to thoroughly examine and understand the litter decomposition process. The widespread Solidago canadensis exerts a negative effect on the composition of the ecosystem, causes extinction of species, and modifies the function of the system. In Hungary, goldenrod constantly spreads to newer areas, which can also be observed around Lake Balaton and at the bank of the Hévíz canal. In our investigation, we examined the decomposition rate of the leaves and stems of the goldenrod with the commonly applied method of leaf litter bags. As water temperature, ranging from 24.0 °C to 13.7 °C, decreases in Hévíz canal away from Lake Hévíz (−0.32 °C/100 m), we chose three different sampling sites with different water temperatures along the canal to determine how water temperature influences the rate of decomposition. For both leaves and stems, the fastest decomposition rate was observed at the first site, closest to the lake. At further sites with lower water temperatures, leaf litter decomposition rates decreased. Results observed through Hévíz canal demonstrated that higher water temperature accelerated the goldenrod decomposition dynamics, while the drift also impacted its efficiency.

Sustainable management of food wastes using effective microorganisms compost

Food waste has become a serious issue in recent years. Due toincrease in over population, solid waste also more generated and affect public health and environment. Food wastes produce methane gas that results greater impact on global warming than carbon dioxide. The composting technology is one of the alternatives, as it is the highest form of recycling of biodegradable solid waste. The study was undertaken to utilize food waste generated, into organic manure using effective micro-organism. A total of 100 kg of food wastes were collected from 100 households in Allahabad over 15 days. The pit was dug for composting using Effective Microorganisms (EM) and natural composting for remediation of organic contaminants. The compost was analyzed and the effectiveness of compost was studied through cultivation of vegetables at households. Results revealed that EM compost had fast decomposition rate, rich in nutrients, more microbial activities, good germination and more yields compared with natural compost. Thus, the study paves way for effective management of food waste in order to minimize potential human and environment risks and composting using effective microorganisms as an option of waste management operation that is cheap, Eco- friendly and sustainable.

Biodeodorization of Barrels Containing Natural Gas Odorants by Bacillus cereus

Introduction: All sulfur organic odorants used in the Iranian gas industry enter the country in 200-liter barrels. There are ways to clean up the empty barrels contaminated with these materials. In the Gas Company, the currently used method is chemical oxidation (using sodium hypochlorite and caustic). In this study, the biological desulfurization and degradation method of mercaptan was studied.Materials and Methods: Desulfurizing bacteria in the university microbial collection, together with bacteria isolated from gas odorant barrels, were examined, among which one of the species had the highest and fastest decomposition rate. This bacterium belongs to the Bacillus cereus family. The most important factors affecting biological desulfurization including initial bacterial concentration, the concentration of odorant, and the Oil Fraction Phase (OFP) were optimized.Results: These three factors were studied using an experimental design. Initial bacterial concentrations were evaluated at five levels from 10 to 50 ml with an optimum concentration of 30 ml. The OFP was also evaluated at five levels from 10 to 90%, with 50% being optimized. Concentrations of odorant were also evaluated from 2500 to12500 ppm, with an optimum concentration of 7500 ppm.Conclusions: Operational testing was carried out in one of the barrels in the optimized conditions for 48 h. The results showed 79.8% efficiency in removing odorant.

In Situ Monitoring of a Eutrophicated Pond Revealed Complex Dynamics of Nitrogen and Phosphorus Triggered by Decomposition of Floating-Leaved Macrophytes

To explore the influence of the decomposition of aquatic macrophytes on water quality in eutrophicated aquatic ecosystems and the interacting environmental factors that trigger nitrogen (N) and phosphorus (P) dynamics, a suburban pond with floating-leaved macrophytes (Pond A) as well as another nearby newly dug pond without any obvious aquatic macrophytes (Pond B) were studied. N and P levels together with a series of parameters relating to biomass, water and sediments were monitored during a period of 84 d that covered the entire decomposition process of plants. The results show that the decomposition of aquatic macrophytes can be divided into two phases, with the first phase having a faster decomposition rate and the second phase, a slower one. With the decomposition of biomass, the dissolved oxygen (DO), oxidation-reduction potential (ORP), and pondus hydrogenii (pH) of the water body increased, whereas the permanganate index (CODMn) decreased. Significantly higher levels of total phosphorus in both water and sediment (TPW and TPS) were detected in Pond A with macrophytes; TPW increased quickly during the first phase of biomass decomposition but decreased in the second phase, and TPS remained relatively stable during the first phase but increased slowly in the second phase. Total nitrogen in both water and sediment (TNW and TNS) was also significantly higher in Pond A but remained relatively stable. A structural equation model revealed that the decomposition of aquatic macrophytes, could, directly and indirectly, influence N and P cycles in an aquatic ecosystem through the regulation of pH and DO. Our study indicate that the decomposition of biomass exerted a greater influence on P than on N. Besides the direct release of P from decaying biomass, which caused a significant increase of P in water body, changes of DO and ORP and the subsequent redox state of the whole system during the process also indirectly affected the deposition and dissolution of P between sediment and water. P was the decisive factor that caused endogenous eutrophication in ponds containing aquatic macrophytes.

Effect of precipitation frequency on litter decomposition of three annual species (Setaria viridis, Artemisia sacrorum, and Chenopodium acuminatum) in a semi-arid sandy grassland of northeastern China

Annual total precipitation typically fails to predict litter decomposition rates, especially in semi-arid regions, where precipitation frequency (PF) significantly affects decomposition. We hypothesized that low PF would decrease decomposition rates. We performed a litterbag decomposition experiment with litter of three annual species at three depths (aboveground litter, litter at 0–10 and 10–20 cm below the surface). We used the same total amount (280 mm), but three precipitation frequencies (PF1, 10 mm every 5 days; PF2, 20 mm every 10 days; PF3, 40 mm every 20 days) during the growing season. We measured the remaining mass, carbon (C) content, nitrogen (N) content, C:N ratio, and C and N losses of each species at the three positions. Litter decomposition and the C and N dynamics were influenced by species, depth, and PF. Low PF significantly decreased litter decomposition (mass loss rates of 49.7, 49.1, and 41.2% for PF1, PF2, and PF3, respectively). This effect interacted with placement-depth but not with species. This interaction also existed for C and N dynamics except for the N loss rate. The influence of PF on C loss mainly resulted from its effect on mass loss, whereas N loss was not affected by PF. Our results highlight the importance of PF for litter decomposition in a semi-arid region. The relationship between PF and litter decomposition provides a theoretical basis for regional carbon-cycle models and carbon budget predictions. Our results also suggest that non-graminaceous species showed higher potential than grasses for improving soil carbon in semi-arid sandy grasslands due to faster decomposition rates, especially below ground.

Optimization of Bokashi-Composting Process Using Effective Microorganisms-1 in Smart Composting Bin.

Malaysians generate 15,000 tons of food waste per day and dispose of it in the landfill, contributing to greenhouse gas emissions. As a solution for the stated problem, this research aims to produce an excellent quality bokashi compost from household organic waste using a smart composting bin. The bokashi composting method is conducted, whereby banana peels are composted with three types of bokashi brans prepared using 12, 22, and 32 mL of EM-1 mother cultured. During the 14 days composting process, the smart composting bin collected the temperature, air humidity, and moisture content produced by the bokashi-composting process. With the ATmega328 microcontroller, these data were uploaded and synchronized to Google Sheet via WIFI. After the bokashi-composting process was completed, three of each bokashi compost and a control sample were buried in separate black soil for three weeks to determine each compost’s effectiveness. NPK values and the C/N ratio were analyzed on the soil compost. From the research, 12 mL of EM-1 shows the most effective ratio to the bokashi composting, as it resulted in a faster decomposition rate and has an optimum C/N ratio. Bokashi composting can help to reduce household food wastes. An optimum amount of the EM-1 used during the bokashi-composting process will produce good quality soil without contributing to environmental issues.

Foliage Litter Decomposition of Agroforestry Shrub Species in Dello-Menna District of Bale Zone, Southeast Ethiopia

In agroforestry land use system soil productivity is maintained via the decomposition of tree/shrub species biomass input mainly foliage’s litter material. The quality of foliage litter material could be considerably varied among species. Hence, better soil management decision in agroforestry land use system remains on identification and use of the desirable species biomass input based on their decomposition characters. A study was conducted to evaluate the decomposition pattern of foliage litter materials of three agroforestry shrub species grown in Dello-menna district of Bale zone, Southeast Ethiopia. In the study single exponential model was employed to determine the decay rate of decomposing litter materials as the dependency of degradation rate on some litter chemical quality indices examined by using Pearson’s correlation coefficient. Results showed that the fastest decomposition rate was 0.037 day-1 for S. sesban followed by 0.017 day-1 for C. cajan and the least 0.014 day-1 for F. macrophylla. The explained variation in rate of decomposition among the tested species was found to be due to the effects of some litter chemical quality parameters. Accordingly lignin, cellulose, lignocelluloses index and C/N ratio were reported as impeding parameters whereas phosphorus and nitrogen identified as facilitators. Indeed, among the species S.sesban was recommended as the most suitable species for short term soil fertility management purpose. However, the accelerated decomposing character of S.sesban foliage litter may limits its potential for long-term build-up of soil fertility. Alternatively F.macrophylla majorly and C.cajan in some case can be considered for long-term build-up of soil organic matter. Keywords: Cajanus cajan, Flemingia macrophylla, Incubation period, Sesbania sesban DOI: 10.7176/JEES/11-3-02 Publication date: March 31 st 2021

Towards sustainable agroforestry management: Harnessing the nutritional soil value through cocoa mix waste

Climate change and environmental degradation have contributed in compromising the soil nutrient integrity of cocoa farmlands, yet sustainable nutrient recycling innovation in cocoa waste management has received less research attention. Utilizing experimentation methodology in an agroforestry system composed of cocoa (Theobroma cacao L.) and a Nitrogen-fixing Gliricidia sepium (Jacq. Kunth ex Walp.), the study examines how the soil nutritional level of farmland can be enhanced. The study confirms the proposition that the rate of decomposition and nutrients release from an innovative mixed waste sample (60% cocoa waste and 40% gliricidia waste in this case) is significantly higher in comparison with the traditional cocoa waste only sample. The results further established that innovative mixed waste sample had a faster decomposition rate (no biomass left at 216 days after laying) as compared to traditional cocoa waste which fully decomposed at 277 days after laying. A difference of 51 days after laying justifies the waste mixture decomposition as a sustainable nutrient recycling innovation within cocoa agroforestry waste management context. These results have implications for agroforestry waste management, soil nutrient recycling and cocoa industry performance.

Effect of Crop Residue Decomposition on Soil Aggregate Stability

The decomposition of fresh crop residues added to soil for agricultural purposes is complex. This is due to different factors that influence the decomposition process. In field conditions, the incorporation of crop residues into soil does not always have a positive effect on aggregate stability. The aim of this study was to investigate the decomposition effects of residues from two different cover crops (Brassica napus var. oleifera and Secale cereale) and one main crop (wheat straw) on soil aggregate stability. A 105-day incubation experiment was conducted in which crop residues were mixed with sandy loam soil at a rate of 6 g C kg−1 of soil. During the incubation, there were five water additions. The decomposition effects of organic matter on soil conditions during incubation were evaluated by determining the soil functional groups; carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4) emissions; soil microbial biomass carbon (MBC); and water-stable aggregates (WSA). The functional groups of the plant residues and the soil were analyzed using Fourier transform infrared spectroscopy (FTIR) and a double exponential model was used to estimate the decomposition rates. The results show that the decomposition rate of fresh organic materials was correlated with the soil functional groups and the C/N ratio. Oilseed rape and rye, with lower C/N ratios than wheat straw residues, had faster decomposition rates and higher CO2 and N2O emissions than wheat straw. The CO2 and N2O flush at the start of the experiment corresponded to a decrease of soil aggregate stability (from Day 3 to Day 10 for CO2 and from Day 19 to Day 28 for N2O emissions), which was linked to higher decomposition rates of the labile fraction. The lower decomposition rates contributed to higher remaining C (carbon) and higher soil aggregate stability. The results also show that changes in the soil functional groups due to crop residue incorporation did not significantly influence aggregate stability. Soil moisture (SM) negatively influenced the aggregate stability and greenhouse gas emissions (GHG) in all treatments (oilseed rape, rye, wheat straw, and control). Irrespective of the water addition procedure, rye and wheat straw residues had a positive effect on water-stable aggregates more frequently than oilseed rape during the incubation period. The results presented here may contribute to a better understanding of decomposition processes after the incorporation of fresh crop residues from cover crops. A future field study investigating the influence of incorporation rates of different crop residues on soil aggregate stability would be of great interest.

Nutrient addition increases rotifer abundance and diversity in a temperate bog

Rotifers are among the smallest metazoan animals living in lakes, ponds, rivers and in interstitial water within Sphagnum mats. When in sufficient numbers they are capable of regenerating large amounts of nitrogen (N) as NO3 and NH4 and phosphorus (P) as PO4; all of these nutrients are immediately available to bog plants. The ecological role of rotifers in bog ecosystems has been recognized at both local and global scales, but the effect of N and P addition on rotifers in bogs remains unknown. Here we present data on the influence of N and P addition on rotifers at a temperate Canadian bog dominated by Sphagnum mosses. We found that rotifer species abundance and diversity were significantly higher in surficial pore water after long-term exposure to increased N and P addition than in the control. A change in plant species distribution and increased rotifer abundance may partly explain the faster decomposition rates, jeopardizing the carbon sink capacity of bogs.

Understanding the Role of Litter Decomposition in Restoration of Fly Ash Ecosystem.

Plant species possess a huge potential in restoration of fly ash ecosystem. Litter deposition and its decomposition in the ash deposited sites are two important processes of the fly ash ecosystem. In order to identify the biological potential of a plant species to aid restoration of fly ash deposited sites, it is needed to assess leaf litter decomposition as well as nutrient release pattern. In the present investigation, we studied the leaf litter decomposition of the plant species (Leucaena leucocephala, Pithecellobium dolce and Prosopis juliflora) and mix plantation in the fly ash ecosystem. The litter bag experiment was conducted in the area of plantation on the fly ash deposited site during a period of 365days. Percentage of C and N was higher in L. leucocephala > P. dolce >Mix Plantation > P. juliflora while C/N ratio was higher in P. juliflora >Mix Plantation > L. leucocephala > P. dolce. L. leucocephala and P. dolce showed relatively fast decomposition rates (k = 1.27, 1.17), respectively while mix plantation (k = 0.82) and P. juliflora (k = 0.73) exhibited relatively slower decomposition rates. Thus, we noted that the decomposition rate of L. leucocephala was greater than the other selected species. This shows that the species having faster decomposition rate and nutrient release could be a factual choice for rehabilitation of fly ash deposited sites.

Habitat edge effects decrease litter accumulation and increase litter decomposition in coastal salt marshes

Habitat fragmentation is known to be one of the leading causes of species extinctions, however few studies have explored how habitat fragmentation impacts ecosystem functioning and carbon cycling, especially in wetland ecosystems. We aimed to determine how habitat fragmentation, defined by habitat area and distance from habitat edge, impacts the above-ground carbon cycling and nutrient stoichiometry of a foundation species in a coastal salt marsh. We conducted our research in a salt marsh in the Mid-Atlantic United States, where the foundation grass species Spartina patens is being replaced by a more flood-tolerant grass, leading to highly fragmented habitat patches. We quantified decomposition rates, live biomass, and litter accumulation of S. patens at patch edges and interiors. Additionally, we measured relevant characteristics (e.g., habitat area, elevation, microclimate) of S. patens patches. Habitat edge effects, and not habitat area effects, had distinct impacts on ecosystem functioning. Habitat edges had less litter accumulation, faster decomposition rates, a warmer and drier microclimate, and lower elevations than patch interiors. Patches with low elevation edges had the fastest decomposition rates, while interiors of patches at any elevation had the slowest decomposition rates. Notably, these impacts were not driven by changes in primary production. Habitat fragmentation impacts the above-ground carbon cycling of S. patens in coastal wetlands by altering litter decomposition, but not primary production, through habitat edge effects. Future research should investigate whether this pattern scales across broader landscapes and if it is observable in other wetland ecosystems.

An excess of niche differences maximizes ecosystem functioning

Ecologists have long argued that higher functioning in diverse communities arises from the niche differences stabilizing species coexistence and from the fitness differences driving competitive dominance. However, rigorous tests are lacking. We couple field-parameterized models of competition between 10 annual plant species with a biodiversity-functioning experiment under two contrasting environmental conditions, to study how coexistence determinants link to biodiversity effects (selection and complementarity). We find that complementarity effects positively correlate with niche differences and selection effects differences correlate with fitness differences. However, niche differences also contribute to selection effects and fitness differences to complementarity effects. Despite this complexity, communities with an excess of niche differences (where niche differences exceeded those needed for coexistence) produce more biomass and have faster decomposition rates under drought, but do not take up nutrients more rapidly. We provide empirical evidence that the mechanisms determining coexistence correlate with those maximizing ecosystem functioning.

Abundance of saprotrophic fungi determines decomposition rates of leaf litter from arbuscular mycorrhizal and ectomycorrhizal trees in a subtropical forest

Leaf litter decomposition is a fundamental process involved in soil carbon and nitrogen dynamics. Observational and experimental evidence suggests that leaf litter from arbuscular mycorrhizal (AM) tree species has a faster decomposition rate than leaf litter from ectomycorrhizal (ECM) tree species. This could be due to the diversity and activity of decomposer microorganisms, but remains to be confirmed in subtropical forests. In this study, we compared the effects of fungi and bacteria on decomposition rates of litter from AM and ECM subtropical trees. In the field, we conducted a fungal hyphal exclusion experiment beneath AM and ECM trees. We also used fungicides and bactericides to distinguish the contribution of bacteria and fungi to litter decomposition in a shade-house experiment. Fungi were responsible more leaf litter decay in soil around AM trees than in soil around ECM trees. When fungi were excluded, AM and ECM litters with similar chemical properties decomposed at the same rate, but the AM litters decayed more quickly when saprotrophic fungi were present. Soil around AM trees had more abundance of saprotrophic fungi and greater N-acetylglucosaminidase and acid phosphatase activities than soil around ECM trees. We conclude that the higher leaf litter decomposition rates under AM trees were due to the saprotrophic fungi in the soil microbial community.