Litter Bags Research Articles

Nutrient cycling and soil quality in threatened veredas in two Protected Areas of the Brazilian cerrado

Veredas are humid environments of significant importance for the Brazilian Cerrado. Understanding soil quality and ecological processes between the soil and vegetation in veredas can provide insights into ecosystem dynamics. This study was aimed to assess litter deposition and decomposition, as well as soil quality, including chemical, physical, and microbiological attributes, in two threatened veredas at various stages of conservation in Brazil. The research was conducted in Almescla (a preserved vereda) within the Environmental Protection Area of the River Pandeiros, and Peruaçu (a degraded vereda) located at the Veredas do Peruaçu State Park. Litter deposition was measured using collectors, and decomposition was assessed with litter bags. Soil granulometry, carbon and nutrient contents, and soil microbial biomass were also evaluated to a depth of 20 cm. The litter production was higher in Peruaçu, with the leaf fraction accounting for more than 70% of the total in both studied areas. The decomposition constant (kc) was higher in Almescla vereda. Nutrient concentrations followed a decreasing order of Ca > N > K > Mg > S > P in both areas. Peruaçu vereda exhibited higher levels of clay, available P, and Ca. Microbial carbon, total organic carbon, microbial quotient, and carbon stock were higher in Almescla, whereas the metabolic quotient was higher in Peruaçu. Our results suggest that the degradation of vereda ecosystems may lead to changes in nutrient cycling, with reduced litter deposition and decreased carbon storage.

Degradation of peat-forming plants at the first stages of decomposition in natural and post-pyrogenic peatlands of West Siberia

The aim of the study. Assessment of the phytomass stocks and decomposition rate of peat-forming plants’ residues in peat deposits of natural and post-pyrogenic peatlands at the initial stages of decomposition. Location and time of the study. The study was carried out in 2022 (May-September) at two oligotrophic bog sites: “Bakcharskoye” (field station “Vasyuganye”, IMCES SB RAS) and “Iksinskoye”, which are located in the north eastern spurs of the Great Vasyugan mire in the Bakcharsky and Shegarsky districts of the Tomsk region, Russia. Methods. The phytomass stocks were determined by the cutting method. The following fractions were separated: living phytomass (annual and perennial photosynthetic phytomass, i.e. green parts of grasses, shrubs leaves, mosses); perennial non-photosynthetic phytomass, i.e. shrubs stems, roots of grasses and shrubs; and dead phytomass (mortmass), i.e. litter, moss litter, standing dead phytomass. The decomposition rate of plant residues was determined by the method of litter bags placement in peat (Chamaedaphne calyculata, Sphagnum fuscum, Mixed sample consisting of 60% S. fuscum and 40% Ch. calyculata). In the initial and decomposed samples, the ash content was determined by the dry combustion method. The total carbon and nitrogen content, as well as the carbon and nitrogen isotopic composition, were determined using a DELTA V Advantage isotope ratio mass spectrometer. Results. This short-term study conducted during the growing season in conditions of undisturbed (Natural Ryam) and post-pyrogenic (Gar) phytocenoses showed that due to a significant amount of mortmass (2402 g/m2) Natural Ryam had organic matter stock exceeding that in the Gar by 1.7 times. On average, 59% of organic matter loss from the total losses during the growing season occurred in the first month. In both Gar and Natural Ryam conditions, minimal losses of organic matter were characteristic for Sphagnum fuscum (3.1 and 3.5% respectively). For the remaining samples the Gar conditions were more favorable for the degradation at the initial stages of decomposition. The Mixed sample occupied an intermediate position between its individual components in terms of mass losses. Carbon losses correlated well with mass losses both over 1 month of degradation (r=0.87) and over 4 months (r=0.96). In contrast to carbon, nitrogen accumulated in the Mixed sample at the initial stages of degradation, both after 1 month and 4 months. Conclusions. With smaller phytomass stocks in areas of post-pyrogenic succession, more active decay at the initial stages of organic matter decomposition occurs exactly under these conditions. The impact of post-pyrogenic succession on the rate of organic matter decomposition of Chamaedaphne calyculata plant residues and the Mixed sample was demonstrated. The most intensive decomposition of litter occured during the first month of degradation. Additionally, in the conditions of a burnt bog, a more intense release of nitrogen from all plant residues and accumulation of ash elements in Sphagnum fuscum samples were observed. The mixing of litter components influenced both the rate and dynamics of decomposition. The carbon and nitrogen isotopic composition began to change during the initial stages of decomposition, leading to enrichment with heavier isotopes 15N and 13C. This research emphasizes the importance of studying the processes of plant litter decomposition at the initial stages and considering the plant residue composition when studying the processes of organic matter transformation.

Impact of Weirs on Decomposition Rates of Dombeya goetzenii (K. Schum) Leaf Litter in the River Njoro, Kenya

Water storage impoundments have deleterious effects on the structure and functioning of running water ecosystems. Many studies have been undertaken on the impacts of large impoundments on river ecosystems. However, comparatively few researches have determined the impact of small weirs on the functioning and structure of running water ecosystems. The main objective of the current study was to determine the impact of weirs on the decomposition rates of Dombeya goetzenii leaf litter in the Njoro River. The study was undertaken at five study sites located along the middle reaches of the Njoro River, near Egerton University, between November 2021 and January 2022. Four study sites were situated at upstream and downstream areas (i.e., approximately 10 m) of two weirs (i.e., Treetops and Canning weirs). A reference site was situated approximately 100 m upstream from the impoundment of the first weir. Physicochemical factors such as temperature, conductivity and nutrients (e.g., nitrates, ammonium) were determined at each study site. Additionally, decomposition rates of one of the most common tree species (i.e., Dombeya goetzenii) found growing along the Njoro River were determined. Leaf litter decomposition was determined using fine (100 µm) and coarse (500 µm) mesh litter bags and the negative exponential decay model was used to estimate decomposition rates (-k per day). The mean leaf litter decomposition rate was highest at the reference site (-k/day = 0.04) and lowest (-k/day = 0.02) at the upstream side of the first weir (i.e., Treetops weir).Leaf litter decomposition rates differed significantly (p = 0.002) between the aforementioned sites. Weirs had a significant local effect on the decomposition rates of Dombeya goetzenii leaf litter. The study provides crucial information to managers of riverine ecosystems about the impact of water storage weirs on an ecosystem function. The concerned government agencies should take action to prevent negative effects of weirs on riverine ecosystems.

Species of Fungi Involved in the Decomposition of Rhizophora apiculata Leaf Litter on Pulau Sembilan

Rhizophora apiculata is one of the mangrove species that grows in coastal areas influenced by seawater. Decomposing leaf litter from R. apiculata is an organic material needed by microorganisms and organisms to grow and develop in the environment where they live. Microorganisms involved in accelerating the decomposition process are fungi. This research activity was carried out for six months, from June to December 2022. This research method uses litter bags to store leaf litter, which will be isolated and the rate of decomposition calculated. The results showed that there were 3 genera of fungi, namely Aspergillus sp., Trichoderma sp., and Penicillium sp. The decomposition rate of R. apiculata leaf litter was 0.13/day. The average carbohydrate content was 8,78%, and the average protein content was 5,45%.
 Keywords: Decomposition, Fungus, Litter, Rhizophora apiculata

Production and Decomposition of Mangrove Species Rhizophora apiculata Blume in Surabaya East Coast Indonesia

The mangrove ecosystem is supported by the production and decomposition of leaf litter, as well as the release of nutrients into the environment and the neighbouring coastal seas. The release of phosphorus and nitrogen contributes significantly to the improvement of the nutritional values, which benefits marine species and the neighbourhood. In the current study, nutrient release, leaf decomposition rate, litter generation, and mangrove habitat at Surabaya East Coast, Java, Indonesia were all examined. Three transects and three plots in each transect were established. The percentage of initial dry mass remaining in the litter bags were determined by using two sample t-test in Statistica 6.0 software. The decomposition of Rhizophora apiculata leaves was studied by using litter bag technique. They were made of synthetic nylon with the dimension of 15×15×25 cm and mesh size of 1×1.25 mm2. Senescent leaves were used because they present major leaves on the forest floor. According to the findings, daily mangrove litter production (dry weight) varied between 2.15 and 3.28 g/m2. Branch litter (9.43 – 13.27%), reproductive parts (8.20 – 14, 31%), and leaf litter (76.26 – 78.53%) were the other major contributors. The 345.6 ha of mangrove forests along the east coast of Surabaya are the results of reforestation, which has the potential to produce nitrogen and phosphorus at the rates of 109.43 to 173.549 kg/ha/year and 5.467 to 8.12 kg/h/year, respectively. These results imply that decomposition breakdown rates differ across the research area due to the variation in the nutrients availability. Changes in the breakdown of detritus point to variations in nutrient intake, which is crucial for mangrove ecosystems.

An Overview of Leaf Litter Decomposition and Nutrient Dynamics of Multipurpose Tree Species

The multipurpose tree species is a plant species that is purposefully grown so as to provide two or more than two products and their leaf litter decomposition in our ecosystems has a play major role in nutrient dynamics in the atmosphere. From this review paper examined different leaf litter decomposition assessing methods in which litter bag method is most suitable methods to determination of decomposition rate. Abiotic factors such as temperature, rainfall, humidity, moisture, evaporation rate and soil physical factors such as soil pH, texture directly correlated to soil microbial such as algae, actinomycetes, bacteria and fungi communities to stimulating action for the breakdown of leaf litter composition (like- cellulose, hemicelluloses, tannin, lignin) and transfer of organic matter to nutrients, release of CO2 to the environment etc.

Effects of flow reduction and artificial light at night (ALAN) on litter decomposition and invertebrate communities in streams: A flume experiment

River ecosystems are heavily impacted by multiple stressors, where effects can cascade downstream of point sources. However, a spatial approach to assess the effects of multiple stressors is missing. We assessed the local and downstream effects on litter decomposition, and associated invertebrate communities of two stressors: flow reduction and artificial light at night (ALAN). We used an 18-flow-through mesocosm system consisting of two tributaries, where we applied the stressors, merging in a downstream section. We assessed the changes in decomposition rate and invertebrate community structure in leaf bags. We found no effect of ALAN or its interaction with flow reduction on the litter decomposition or the invertebrate community in the tributaries. Flow reduction alone led to a 14.8 % reduction in decomposition rate in the tributaries. We recorded no effect of flow reduction on the macroinvertebrates community composition in the litter bags. We also observed no effects of the spatial arrangement of the stressors on the litter decomposition and macroinvertebrate community structure downstream. Overall, our results suggest the impact of stressors on litter decomposition and macroinvertebrate communities remained local in our experiment. Our work thus calls for further studies to identify the mechanisms and the conditions under which spatial effects dominate over local processes.

Seasonality and hyphomycetes’ conidia conditioning affect the diversity of Chironomidae larvae associated with leaf litter in a tropical stream

This study aimed to evaluate the structure, taxonomic, and trophic composition of an assemblage of chironomid larvae associated with leaf litter in a tropical stream (Brazilian Cerrado biome) during different seasonal periods. Additionally, the study aimed to examine the relationship between the activity of decomposing microorganisms and the abundance and total richness of chironomids. To conduct the study, leaves were collected in buckets from the Boiadeiro stream at five sampling points over 30 consecutive days, resulting in a total collection of 12 months. Then, they were placed in litter bags (n = 3 per point) and incubated in the stream for 30 days to evaluate chironomid colonization and microbial activity. A total of 3,892 chironomid larvae were identified. Among the functional feeding groups (FFGs) of chironomid larvae, the food collector-gatherer group displayed higher diversity than other FFGs. The richness of chironomids was positively associated with the number of conidia produced by aquatic hyphomycetes' during leaf decomposition. We found that during the dry season (April–August), the highest values of abundance and total richness of chironomids were recorded, accompanied by the lowest taxonomic variability of chironomid larvae. Conversely, environmental variations in the rainy season contributed to greater taxonomic variability but lower abundance and total richness of chironomids associated with leaf detritus.

Cover crop residue quality regulates litter decomposition dynamics and soil carbon mineralization kinetics in semi-arid cropping systems

Cover crop residue addition provides several soil health benefits and serves as a precursor for storing soil organic carbon (SOC). However, information on residue decomposition dynamics and its contribution to soil carbon (C) and nitrogen (N) cycling in arid and semi-arid environments is limited. This study evaluated cover crop residue decomposition in field conditions and C mineralization kinetics in laboratory conditions. For the field experiment, approximately 20 g of Austrian winter pea (Pisum sativum subsp. arvense L.), turnip (Brassica rapa subsp. rapa L.), and triticale (×Triticosecale Wittmack) cover crop residues were kept in litter bags and placed on the soil surface before subsequent forage sorghum (Sorghum bicolor L. Moench) planting in ongoing cover crops study plots. Litter bags were collected every other week (12 destructive samplings) to evaluate the remaining dry matter and C and N contents. The decomposition data were plotted with first order kinetics and exponential models to describe the model fit. To study C mineralization kinetics, a 10-week incubation was set up in a laboratory with Austrian winter pea, turnip, and triticale cover crops and native grass, wheat, and sorghum residues. Carbon mineralization rates were evaluated with three statistical models (first order kinetics and single and double exponential). The exponential model best described the cover crop residue decomposition kinetics in the field. After 98 days, the residue decomposition was higher with Austrian winter pea (47 %), followed by turnip and triticale with ∼40 % biomass decomposition. Residue types and quality both affected the decomposition rates. The C mineralization rate correlated with initial N content (r = 0.87, P < 0.05), C: N ratio (r = −0.88, P < 0.05), and lignin: N (r = −0.87, P < 0.05). While the single exponential model explained field decomposition dynamics, the double exponential decay model best fitted the observed C mineralization trend among the three models. The decay models from our study can be applied to estimate the decomposition dynamics of other winter cover crop residues in similar agroecosystems. This study demonstrated that selecting suitable cover crops and mixtures is critical for maximizing soil C sequestration and N availability in subsequent crops in cover crop-integrated semi-arid cropping systems.

Fine root decomposition and macronutrient release in temperate forests: Examining the litter bag and intact soil core approaches and their relationship with fungal community composition

Accurate measurement of decomposition of fine roots in forests is important for understanding nutrient cycling, carbon dynamics and biotic responses; however, various sources of error or bias interfere with commonly used approaches. Most studies of fine root decomposition have used the buried root litter bag method, but this method may underestimate decay rates based on comparisons with the less disruptive, intact soil core approach. We compared these two methods for one year for seven temperate forest trees growing in twelve monospecific plantations in central New York. The experimental design included four species that form arbuscular mycorrhizae (sugar maple, red maple, cherry, tulip poplar) and three with ectomycorrhizae (pine, spruce, oak). We also examined macronutrients (N, P) release and fungal community composition of decaying fine roots using Illumina sequencing. Across the seven species and 12 plots, fine root decay rate was significantly higher for intact cores than litter bags, with the difference being approximately 12 %, a smaller disparity than that observed in previous comparisons. However, one species (Norway spruce) showed the opposite trend. Similarly, N and P release from decaying roots was significantly greater for the intact core method, but again with an exception (red oak). No consistent effects of mycorrhizal type on the method effect or decay rate and nutrient release were detected. Fungal communities in decaying roots differed between the two methods; nevertheless, Mycena spp. dominated most plots for both methods. These results further emphasize the notion that decay rates and nutrient mobilization of fine roots in forests are usually underestimated by the litter bag approach.

The Fungal Development During The Leaf Litter Process Decomposition of Avicennia marina

The existence of mangrove ecosystems decreases from land conversion into residential areas, industries, plantations, road facilities and the construction of ponds. This research was conducted in the mangrove forest area of Secanang Belawan Village, Medan, at the Biotechnology Laboratory of the Department of Forestry, Faculty of Agriculture, USU and at the Microbiology Laboratory, Department of Biology, Faculty of Mathematics and Natural Sciences, USU Medan. The study's objective was to identify the different fungal species that were present at 10 ppt salinity levels, 10–20 ppt, and 20–30 ppt as well as the pace at which Avicennia marina leaf litter. The research method used litter bags filled with leaf litter of Avicennia marina (50 g) with 7 treatments, 3 replications and 3 levels of salinity. The A. marina leaf litter that had a salt level of 10 ppt had the highest level of decomposition. The dry weight of leaf litter left in the litter bag, which is 4.92 g on average. The largest dry weight of the remaining litter was found in an environment with a salinity of 20 – 30 ppt, which is an average of 10.42 g. The rate of decomposition of A. marina leaf litter in an environment with a salt level greater than 30 ppt is 6.53/yr (or almost equal to residence period of = 0.15 yr). The number of fungal species discovered in the leaf litter of A. marina, which goes through a breakdown process at salinity levels between 0 and 10 ppt and contains 9 species, is another way to observe the impact of salt level. In comparison to the large at salinity levels of 10 to 20 ppt and 20 to 30 ppt, respectively, there were populations of fungus that underwent the process of decomposition in A. marina leaf litter, with an average of 5.99 x 102 cfu/ml and 5.5 x 102 cfu/ml, the fungal population that was the highest concentration was 10.72 x 102 cfu/ml

Top-Down Effect of Arthropod Predator Chinese Mitten Crab on Freshwater Nutrient Cycling.

Aquatic litter decomposition is highly dependent on contributions and interactions at different trophic levels. The invasion of alien aquatic organisms like the channeled apple snail (Pomacea canaliculata) might lead to changes in the decomposition process through new species interactions in the invaded wetland. However, it is not clear how aquatic macroinvertebrate predators like the Chinese mitten crab (Eriocheir sinensis) will affect the nutrient cycle in freshwater ecosystems in the face of new benthic invasion. We used the litter bag method to explore the top-down effect of crabs on the freshwater nutrient cycle with the help of soil zymography (a technology previously used in terrestrial ecosystems). The results showed significant feeding effects of crabs and snails on lotus leaf litter and cotton strips. Crabs significantly inhibited the intake of lotus litter and cotton strips and the ability to transform the environment of snails by predation. Crabs promoted the decomposition of various litter substrates by affecting the microbial community structure in the sediment. These results suggest that arthropod predators increase the complexity of detrital food webs through direct and indirect interactions, and consequently have an important impact on the material cycle and stability of freshwater ecosystems. This top-down effect makes macrobenthos play a key role in the biological control and engineering construction of freshwater ecosystems.

Dynamics of trace and rare earth elements during long-term (over 4 years) decomposition in Scots pine and Norway spruce forest stands, Southern Sweden

The temporal dynamics of 33 major, trace, and rare earth elements (REEs) were studied in the litter samples containing Swedish Norway spruce (Picea abies) (NSL) and Scots pine (Pinus sylvestris) (SPL), with the aim to assess their release and accumulation dynamics. Litter bags (8 × 8 cm) were incubated in paired monoculture stands with both the species for up to 5 years from 1979 to 1984 according to a randomized block design comprising 25 blocks (1 × 1 m) within an area of 625 m2. The decomposition rate was slightly higher for Scots pine litter (k = 0.315) than for Norway spruce litter (k = 0.217). During litter decomposition, at ∼70% accumulated mass loss (AML), the concentration of trace elements increased by &amp;gt;50% in both litter types compared to initial concentrations. The concentration change took place in a non-linear pattern, and polynomial quadratic regression between concentration change and accumulated mass loss resulted in significant relationships (adj R2 = 0.20–0.97; p = 0.15–&amp;lt;0.0001). The changes in concentration and amount of trace elements resulted in two main types of dynamics: 1) both concentration and amount increased for Fe, Al, Ti, Cu, Mo, V, Zr, Sb, As, Cs, Pb, Th, and U; 2) concentration increased but amount decreased for Ni, Zn, Li, and Sr. The amount of REEs increased from ∼3-fold to 99-fold from the beginning to the end of incubation, suggesting accumulation during litter decomposition. The dynamics of different REEs were similar in their change patterns in the two litters. Different REEs had generally identical change patterns during incubation, which is reflected in the high correlations among them (r2 = &amp;gt;0.95). A general upward convexity in the dynamics suggests that if further incubated in the field, decomposing litter could have accumulated more REEs in the organic matter. The results of this study can be useful for future studies in other ecosystems including metal-contaminated sites or element-depleted sites. Plant litter accumulation, its decomposition, and build-up of humic substances in the decomposing organic matter can act as a sink for elements and can be used as a management tool for ecological amelioration of metal-contaminated sites as well as natural systems that are impoverished, especially recuperating sites. The study’s findings have implications beyond such sites and can be useful in any research that seeks to understand the patterns of accumulation and release related to decomposition in different ecosystems.

Litter dynamics and nutrient flux in endemic bamboo species Dendrocalamus stocksii plantations in moist semi-arid zones of peninsular India

The study was undertaken to understand litterfall, litter decomposition and nutrient release pattern of popularly grown bamboo species, Dendrocalamus stocksii, in the moist semi-arid agro-climatic zone of Karnataka, India. The litter production and decomposition were studied using the standard litter trap and bag techniques. The total annual litter production in 2017 was 6.03 Mg ha-1 year-1 for Gottipura and 5.81 t ha-1 year-1 for Nallal. Litter production was continuous, but the quantity of litter produced varied with season and month. Nutrient concentrations in monthly litter samples varied. Peak litter fall was concentrated during the hot-dry period (February-May) as 62.8 per cent at Gottipura and 52.2 per cent at Nallal site. The collected litter from the litter traps was dominated by leaf litter. Litter production followed a similar pattern for both locations, with a major peak in March 2017, it was found that both types of litter and filter paper had an initial rapid phase of decomposition followed by a slower phase. The increase in percentage nutrient content in litter samples found in litter bags collected month-wise have been attributed to the high temperature and increased rates of mineralization assisted by soil microbes over the low immobilization rate.

Contribution of roots to soil organic carbon: From growth to decomposition experiment

Carbon (C) derived from roots, rhizodeposition of living roots and dead root decomposition, plays a critical role in soil organic C (SOC) sequestration. Recent studies suggest that root inputs exert a disproportionate influence on SOC formation, and therefore, it is necessary to test separately the effects during root growth (i.e. rhizodeposition) and dead root decomposition (i.e. belowground litter) undernaturalconditions. A field experiment was carried out in grasslands with three typical plants: Stipa bungeana (St.B), Artemisia sacrorum (Ar.S), and Thymus mongolicus (Th.M) to differentiate the effects of root growth vs decomposition on C inputs by using in-growth soil cores and litter bag methods. For root growth experiment, the SOC content increased (2.5–3.8 g·kg−1) with root biomass, especially in soil under Ar.S. C input increased mineral-associated organic C (MAOC%) from 57% to 65%. The SOC δ13C was consistent with roots δ13C, indicating the roots were the primary source of SOC. The root decomposition experiment showed that the increase in SOC (0.74–2.6 g·kg−1) was highest at 90 days. Root decomposition rate was fast before 45 days, and SOC increased with the MAOC% during this period. After 45 days, particulate organic C % (POC%) was raised and was higher than in the control soil. The increase in SOC under root growth (2.5–3.8 g·kg−1) after one year was greater as compared to the rate under root decomposition (-0.4–0 g·kg−1). It suggested that C released during root growth was more effectively retained in the soil than that caused by dead root decomposition. The rise in MAOC during root growth and decomposition mainly explains the increase in SOC. Our results provided direct field based evidence illustrating the specific contribution of root growth and decomposition to SOC.

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.

Cover Crop Residues Decomposition and Nutrient Releases in a Sandy Ultisols of U.S. Coastal Plain: Impacts of Termination Timing

ABSTRACT One benefit of cover cropping is nutrient provision, which can be optimized by management practices to synchronize nutrient releases from residue decomposition with the demands of subsequent cash crops. In the present study, we investigated how termination timing affects the decomposition of cereal rye (Secale cereale L.) residues and the release of associated nutrients. Field experiments were conducted in 2019 and 2020 in typical Ultisols of the Southeastern U.S. with soybean (Glycine max L.) and corn (Zea mays L.) rotation. Cover crops were drill-seeded and terminated 1-, 2-, 3- and 4-week before cash crop planting. Litter bag method and a two-parameter exponential decaying model were applied to estimate residue decomposition and nutrient releases. In 2019, cover crop biomass production ranged from 5757 to 6520 kg ha−1, which was not affected by termination timing. In contrast, cover crop biomass increased when delaying termination by 1 week in 2020. Cover crop provided up to 82 kg nitrogen (N) ha−1, 15 kg phosphorous (P) ha−1, and 89 kg potassium (K) ha−1 in 2019. As expected, terminating cover crops at 1-week intervals resulted in different decomposition rates but imposed inconsistent effects on N, P, and K releases. There was no difference in N, P, and K content in cash crops. However, cover cropping resulted in higher corn yields than control plots when terminated at 4-week before corn planting. The results suggested that cover crops can have significant nutrient benefits in the tested soils and climatic conditions, but optimal management is the key to realizing the potential.

Analysis of Organic Matter Decomposition in the Salt Marshes of the Venice Lagoon (Italy) Using Standard Litter Bags

AbstractTidal salt marshes are widespread along the World's coasts, and are ecologically and economically important as they provide several valuable ecosystem services. In particular, their significant primary production, coupled with sustained vertical accretion rates, enables marshes to sequester and store large amounts of organic carbon and makes them one of the most carbon‐rich ecosystems on Earth. Organic carbon accumulation results from the balance between inputs, that is, organic matter produced by local plants or imported, and outputs through decomposition and erosion. Additionally, organic matter deposition actively contributes to marsh vertical accretion, thus critically affecting the resilience of marsh ecosystems to rising relative sea levels. A better understanding of organic‐matter dynamics in salt marshes is key to address salt‐marsh conservation issues and to elucidate marsh importance within the global carbon cycle. Toward this goal, we empirically derived rates of organic matter decomposition by burying 712 commercially available tea bags at different marshes in the microtidal Venice Lagoon (Italy), and by analyzing them following the Tea Bag Index protocol. We find values of the decomposition rate (k) and stabilization factor (S) equal to 0.012 ± 0.003 days−1 and 0.15 ± 0.063, respectively. Water temperature critically affects organic matter decomposition, enhancing decomposition rates by 8% per °C on average. We argue that, at least in the short term, the amount of undecomposed organic matter that actively contributes to carbon sequestration and marsh vertical accretion strongly depends on the initial organic matter quality, which is a function of marsh and vegetation characteristics.

Above and belowground litter decomposition of cover crops grazed at different intensities

AbstractGrazing cover crops may increase land‐use efficiency while promoting sustainability. We investigated how grazing intensity affects cover crop litter quantity, quality, decomposition, and cotton (Gossypium hirsutum L.) N uptake. Cover crops were a mixture of rye (Secale cereale L.) and oat (Avena sativa L.) managed as follows: no grazing +34 kg N ha−1 (NG34), no grazing +90 kg N ha−1 (NG90), heavy grazing (HG), moderate grazing (MG), and light grazing (LG). Grazed treatments received 90 kg N ha−1. After cover crop termination, above‐ and belowground litter was collected and incubated in situ for 0, 4, 8, 16, 32, 64, and 128 days, with cotton plants sampled on the same days to estimate N recovery and synchrony between N release from litter and uptake by cotton. By Day 128, only 13% of initial NG34 aboveground biomass had disappeared, whereas 42% of HG disappeared. Nitrogen retained in aboveground litter of HG was less than NG90 (27 vs. 60 kg N ha−1), and aboveground final N stock (at Day 128) of HG was less than NG90 and LG (16, 47, and 41 kg N ha−1, respectively). Belowground litter contributed 98 kg N ha−1 versus 46 for aboveground. Belowground N disappearance from litter bags was greater from NG90 than NG34 (39 vs. 21 kg N ha−1). Cotton N uptake by Day 128 was similar across treatments (191 kg N ha−1). Grazing cover crops impact aboveground litter quantity, quality, and decomposition rates, and belowground litter plays an important role on the N cycling.

The Invasive Tradescantia zebrina Affects Litter Decomposition, but It Does Not Change the Lignocellulolytic Fungal Community in the Atlantic Forest, Brazil.

Invasive plants affect ecosystems across various scales. In particular, they affect the quality and quantity of litter, which influences the composition of decomposing (lignocellulolytic) fungal communities. However, the relationship among the quality of invasive litter, lignocellulolytic cultivated fungal community composition, and litter decomposition rates under invasive conditions is still unknown. We evaluated whether the invasive herbaceous Tradescantia zebrina affects the litter decomposition in the Atlantic Forest and the lignocellulolytic cultivated fungal community composition. We placed litter bags with litter from the invader and native plants in invaded and non-invaded areas, as well as under controlled conditions. We evaluated the lignocellulolytic fungal communities by culture method and molecular identification. Litter from T. zebrina decomposed faster than litter from native species. However, the invasion of T. zebrina did not alter decomposition rates of either litter type. Although the lignocellulolytic fungal community composition changed over decomposition time, neither the invasion of T. zebrina nor litter type influenced lignocellulolytic fungal communities. We believe that the high plant richness in the Atlantic Forest enables a highly diversified and stable decomposing biota formed in conditions of high plant diversity. This diversified fungal community is capable of interacting with different litter types under different environmental conditions.