Leaf Litter Decomposition Process Research Articles

Dieback and Replacement of Riparian Trees May Impact Stream Ecosystem Functioning

Alders are nitrogen (N)-fixing riparian trees that promote leaf litter decomposition in streams through their high-nutrient leaf litter inputs. While alders are widespread across Europe, their populations are at risk due to infection by the oomycete Phytophthora ×alni, which causes alder dieback. Moreover, alder death opens a space for the establishment of an aggressive N-fixing invasive species, the black locust (Robinia pseudoacacia). Shifts from riparian vegetation containing healthy to infected alder and, eventually, alder loss and replacement with black locust may alter the key process of leaf litter decomposition and associated microbial decomposer assemblages. We examined this question in a microcosm experiment comparing three types of leaf litter mixtures: one representing an original riparian forest composed of healthy alder (Alnus lusitanica), ash (Fraxinus angustifolia), and poplar (Populus nigra); one with the same species composition where alder had been infected by P. ×alni; and one where alder had been replaced with black locust. The experiment lasted six weeks, and every two weeks, microbially driven decomposition, fungal biomass, reproduction, and assemblage structure were measured. Decomposition was highest in mixtures with infected alder and lowest in mixtures with black locust, reflecting differences in leaf nutrient concentrations. Mixtures with alder showed distinct fungal assemblages and higher sporulation rates than mixtures with black locust. Our results indicate that alder loss and its replacement with black locust may alter key stream ecosystem processes and assemblages, with important changes already occurring during alder infection. This highlights the importance of maintaining heathy riparian forests to preserve proper stream ecosystem functioning.

Factors affecting the decomposition of leaf litters in a mini-forest

The fallen leaves, small twigs, seeds, and other woody debris that accumulate on the ground are a natural part of the forests and make up the leaf litter. Leaf litter is an important factor in healthy soil. As it decomposes, it replenishes soil with nutrients such as nitrogen, phosphorus, and other inorganic compounds. This study aimed to identify the factors affecting the rate of the leaf litter decomposition process. The study was conducted in the mini forest and observation was conducted from August to October 2017. Data was collected weekly by observing and counting insects, and invertebrates in the leaf litter set-up which was composed of varying decaying leaf colors placed inside a mesh; the setup was separated into three colors: green, orange, and brown color and initially weighed 200 grams for each mesh bag and placed on the forest floor. The weight changes were noted every week during the visit to the field setup. This leaf litter observation concludes that various factors are affecting the process of decomposition of the leaf litter. This includes the presence of invertebrates and decomposers, the age of the leaves used in the setup, temperature, and the disturbances.

Do magnesium and chloride ameliorate high sodium bicarbonate concentrations? A comparison between laboratory and mesocosm toxicity experiments

Increasing salinity is a concern for biodiversity in many freshwater ecosystems globally. Single species laboratory toxicity tests show major differences in freshwater organism survival depending on the specific ions that comprise salinity types and/or their ion ratios. Toxicity has been shown to be reduced by altering ionic composition, despite increasing (total) salinity. For insistence, single species tests show the toxicity of sodium bicarbonate (NaHCO3, which commonly is a large proportion of the salts from coalbeds) to freshwater invertebrates is reduced by adding magnesium (Mg2+) or chloride (Cl−). However, it is uncertain whether reductions in mortality observed in single-species laboratory tests predict effects within populations, communities and to ecosystem processes in more complex multi-species systems both natural and semi-natural. Here we report the results of an outdoor multi-species mesocosm experiment to determine if the effects of NaHCO3 are reduced by increasing the concentrations of Mg2+ or Cl− on: a) stream macroinvertebrate populations and communities; b) benthic chlorophyll-a and; c) the ecosystem process of leaf litter decomposition. We found a large effect of a high NaHCO3 concentration (≈4.45 mS/cm) with reduced abundances of multiple taxa, reduced emergence of adult insects and reduced species richness, altered community structure and increased leaf litter breakdown rates but no effect on benthic chlorophyll-a. However, despite predictions based on laboratory findings, we found no evidence that the addition of either Mg2+ or Cl− altered the effect of NaHCO3. In semi-natural environments such as mesocosms, and natural environments, organisms are subject to varying temperature and habitat factors, while also interacting with other species and trophic levels (e.g. predation, competition, facilitation), which are absent in single species laboratory tests. Thus, it should not be assumed single-species tests are good predictors of the effects of changing ionic compositions on stream biota in more natural environments.

Warming overrides eutrophication effects on leaf litter decomposition in stream microcosms

Several human activities often result in increased nitrogen (N) and phosphorus (P) inputs to running waters through runoff. Although headwater streams are less frequently affected by these inputs than downstream reaches, the joint effects of moderate eutrophication and global warming can affect the functioning of these ecosystems, which represent two thirds of total river length and thus are of major global relevance. In a microcosm study representing streams from a temperate area (northern Spain), we assessed the combined effects of increased water temperature (10.0, 12.5, and 15.0 °C) and nutrient enrichment (control, high N, high P, and high N + P concentrations) on the key process of leaf litter decomposition (mediated by microorganisms and detritivores) and associated changes in different biological compartments (leaf litter, aquatic hyphomycetes and detritivores). While warming consistently enhanced decomposition rates and associated variables (leaf litter microbial conditioning, aquatic hyphomycete sporulation rate and taxon richness, and detritivore growth and nutrient contents), effects of eutrophication were weaker and more variable: P addition inhibited decomposition, addition of N + P promoted leaf litter conditioning, and detritivore stoichiometry was affected by the addition of both nutrients separately or together. In only a few cases (variables related to detritivore performance, but not microbial performance or leaf litter decomposition) we found interactions between warming and eutrophication, which contrasts with other experiments reporting synergistic effects. Our results suggest that both stressors can importantly alter the functioning of stream ecosystems even when occurring in isolation, although non-additive effects should not be neglected and might require exploring an array of ecosystem processes (not just leaf litter decomposition) in order to be detected.

Nanoplastic pollution inhibits stream leaf decomposition through modulating microbial metabolic activity and fungal community structure

Many studies have proved the impacts of nanoplastic pollution in freshwaters on aquatic organisms and ecosystems. To explore toxic mechanisms of nanoplastics on stream functioning, we conducted a microcosm experiment to investigate the effects of polystyrene nanoparticles (PS NPs, 1–100 μg L−1) on the process of leaf litter decomposition mediated by the microbial community. The chronic exposure to PS NPs at 1 and 100 μg L−1 caused significant decreases in leaf litter decomposition and nutrient (carbon and nitrogen) releases. During the ecological process, some extracellular enzymes (i.e., β-glucosidase, glycine-aminopeptidase, and phenol oxidase) rather than fungal biomass were suppressed. Besides, decreases in the relative abundance of Anguillospora and Setophaeosphaeria weakened their functions in leaf litter decomposition. Thus, the microcosm experiment showed that PS NPs inhibited stream leaf decomposition by modulating the microbial metabolic activity and fungal community structure. Overall, the results of this study provide evidence for the consequences of nanoplastic pollution on freshwater microbial community and stream ecosystem functioning, which is conducive to evaluate the potential risks of nanoplastics in aquatic environments.

Effects of tree species diversity on leaf litter decomposition process in semi-arid Mediterranean oak forests

Effects of tree species diversity on leaf litter decomposition process in semi-arid Mediterranean oak forests

Measuring of leaf litter decomposition rate and flux of carbon dioxide in various land cover in Gunung Bromo Education Forest, Karanganyar

The process of leaf litter decomposition on the soil surface as a source of nutrition and food for soil fauna. Leaf litter decomposition rate is influenced by the activity of soil fauna, which is thought to increase the emission of carbondioxide from the soil. The aim of this research was to investigate the leaf decomposition rate and flux of carbon dioxide in various land cover. The research was conducted from July to November 2020 in Gunung Bromo Education Forest, Karanganyar, Central Java. This research used purposive sampling with nine land covers and three replications. The leaf decomposition rate was measured using the litterbag method, and flux of carbon dioxide was measured using the closed chamber method. The results suggested that the leaf decomposition rate was the fastest in Pine 2016 at 6.17 g/week, and the highest flux of carbon dioxide in Indonesian rosewood (Dalbergia sissoo) rejuvenation was 9,860 mg/CO2/day. The leaf decomposition rate was influenced by air temperature (p = 0.535) compared to humidity (p = - 0.257). Flux carbondioxide is influenced by air temperature (p = 0.854) compared to humidity (p = - 0.677), and the leaf decomposition rate affects the level of flux of carbon dioxide (p = 0.631).

Litter decomposition can be reduced by pesticide effects on detritivores and decomposers: Implications for tropical stream functioning

Understanding which factors affect the process of leaf litter decomposition is crucial if we are to predict changes in the functioning of stream ecosystems as a result of human activities. One major activity with known consequences on streams is agriculture, which is of particular concern in tropical regions, where forests are being rapidly replaced by crops. While pesticides are potential drivers of reduced decomposition rates observed in agricultural tropical streams, their specific effects on the performance of decomposers and detritivores are mostly unknown. We used a microcosm experiment to examine the individual and joint effects of an insecticide (chlorpyrifos) and a fungicide (chlorothalonil) on survival and growth of detritivores (Anchytarsus, Hyalella and Lepidostoma), aquatic hyphomycetes (AH) sporulation rate, taxon richness, assemblage structure, and leaf litter decomposition rates. Our results revealed detrimental effects on detritivore survival (which were mostly due to the insecticide and strongest for Hyalella), changes in AH assemblage structure, and reduced sporulation rate, taxon richness and microbial decomposition (mostly in response to the fungicide). Total decomposition was reduced especially when the pesticides were combined, suggesting that they operated differently and their effects were additive. Importantly, effects on decomposition were greater for single-species detritivore treatments than for the 3-species mixture, indicating that detritivore species loss may exacerbate the consequences of pesticides of stream ecosystem functioning.

Effects of sulfonamide antibiotics on aquatic microbial community composition and functions

Knowledge on interactions among microbial communities colonizing various streambed substrata (e.g. cobbles, sediment, leaf-litter etc.) is essential when investigating the functioning of stream ecosystems. However, these interactions are often forgotten when assessing the responses of aquatic microbial communities to chemical contamination. Using a stream microcosm approach, the respective impact of two sulfonamide antibiotics (sulfamethoxazole and sulfamethazine) on the ability of microbial heterotrophs to decompose alder leaves was investigated in the presence or absence of periphyton. Our hypothesis suggested that sulfonamides would negatively impair microbial litter decomposition and that periphyton could possibly alleviate this effect by stimulating microbial decomposer activity through a priming effect. Results showed that the presence of periphyton enriched water with oxygen and labile dissolved organic carbon forms. However, these labile organic carbon sources did not stimulate leaf-litter decomposition but mostly decoupled microbial decomposer activity from particulate organic matter to dissolved organic matter through negative priming. Also, the two sulfonamide molecules did not affect the leaf-litter decomposition process but significantly decreased bacterial biomass accrual on leaves. The reduction of bacteria was concomitant with an increase in biomass-specific β-glucosidase activity and this was attributed to a stress response from bacteria to sulfonamides. Further research looking at microbial interactions would provide for better assessment of chemical contamination effects in communities and processes in stream ecosystems.

Combined effects of freshwater salinization and leaf traits on litter decomposition

Freshwater salinization is a matter of major global concern due to its consequences on the aquatic biota and ecosystems functioning. Salt contamination negatively affects the leaf litter decomposition process, a key ecosystem-level process in forested streams that contributes to the recycling of nutrients and carbon storage. However, information on how additional factors may influence the magnitude of the response to salinization is scarce. In this microcosm study we assessed the importance of leaf (Castanea sativa; Quercus robur) traits, on aquatic hyphomycetes-mediated leaf litter decomposition and associated variables, in salt-contaminated (0, 1, 3 and 6 g/l NaCl) environments. The leaves were incubated individually, and in a mixture, for 28 days, under each tested salt concentration. Salinity depressed leaf mass loss, fungal biomass, respiration and sporulation rates, particularly at the highest salt concentration. Differences across leaf categories were observed in all parameters but fungal biomass, although the effects were not consistent across descriptors. All leaf categories responded with a similar intensity to salt contamination for all measured variables but sporulation rate. These results suggest that the deleterious influence of salt on litter decomposition occurs independently of the traits of the stream riparian subsidies.

Terrestrial Isopods Porcellio scaber and Oniscus asellus (Crustacea: Isopoda) Increase Bacterial Abundance and Modify Microbial Community Structure in Leaf Litter Microcosms: a Short-Term Decomposition Study.

Invasive terrestrial isopods are likely to have altered leaf litter decomposition processes in North American forests, but the mechanisms underlying these alterations and the degree to which they differ among isopod species are poorly characterized. Using mixed-deciduous leaf litter microcosms, we quantified the effects of two common, invasive isopods (Oniscus asellus and Porcellio scaber) on short-term leaf litter decomposition and microbial community structure and function. Microcosms containing ground litter and a microbial inoculant were exposed to one of the two isopod species or no isopods for 21 days. Mass loss was then quantified as the change in litter dry mass after leaching, and microbial respiration was quantified as the mass of CO2 absorbed by soda lime. Litter leachates were plated on agar to quantify culturable bacterial and fungal abundance, and denaturing gradient gel electrophoresis of amplified leachate microbial DNA was used to characterize shifts in microbial community structure. Isopod presence increased litter mass loss by a modest ~ 6%, but did not affect litter microbial respiration. Bacterial abundance increased significantly in the presence of isopods, while fungal abundance was either unchanged or reduced. Overall litter microbial species richness was reduced by isopods, with O. asellus specifically reducing fungal abundance and diversity. Isopods modified the microbial community structure by suppressing four bacterial and one fungal species, while promoting growth of four other bacterial species (two unique to each isopod species) and two fungal species (one which was unique to O. asellus).

Isolation and identification of decomposer fungi from Macaranga indica and Hibiscus macrophyllus leaf litter from restoration area of Gunung Leuser National Park

Leaves mostly litter on the forest floor. The process of leaf litter decomposition involves the role of microorganisms such as fungi. The study aimed to isolating and identifying the fungi of Macaranga indica and Hibiscus macrophyllus leaf litter. The leaf litter was taken under the stand of Macaranga indica and Hibiscus macrophyllus in the restoration area of Gunung Leuser National Park Sei Betung Resort North Sumatra. Fungi were isolated using the direct plating methods with Potato Dextrose Agar medium. The purified fungi were then identified morphologically to the genus level. Morphological identification carried out by looking at the macroscopic and microscopic features of fungi. There were six isolates from Macaranga indica leaf litter and eight isolates from Hibiscus macrophyllus leaf litter. The result shows that there are five genera of fungi consisting of Aspergillus, Penicillium, Mucor, Trichoderma, and Cladosporium.

Presumption of allelopathic compound(s) released in the leaf litter decomposition process of invasive plants: Calliandra calothyrsus and Cinchona pubescens

Mutaqien Z. 2017. Presumption of allelopathic compound(s) released in the leaf litter decomposition process of invasive plants: Calliandra calothyrsus and Cinchona pubescens. Pros Sem Nas Masy Biodiv Indon 3: 334-338. Invasive alien species is one of the main cause of ecological systems dramatically changes and also native species extinction worldwide. However, more studies are needed to discover its mechanism, including role of allelopathy compound in invasive plants competition. Cinchona pubescens Vahl. and Calliandra calothyrsus Meissn. are recorded as invasive species in some regions. Moreover, C. pubescens is stated as one of 100 of the world’s worst invasive alien species by IUCN. This study aimed to confirm indication of the existence of allelopathic mechanism in invasion process of these two invasive alien species by releasing allelopathic compound(s) from its leaves fall over decomposition process. To clarify this hypothesis, a preliminary study had been conducted by testing the effect of the compounds released from decomposition process over the times (7-180 days) to germination of Vigna radiata (L.) R. Wilczek in the laboratory. Completly Randomize Design was used by applying liquid produced by decomposition process of these two invasive species and control (three repetitions) to test its effects. Radicles and hypocotyls length were measured, compared and Anova analyzed by using R-statistic 3.1.3. Germination of V. radiata only significantly inhibited by compound(s) released by decomposition processes of C. callisaya’s leaves. Its inhibition effect was reduced over the times

Does the loss of climate sensitive detritivore species alter leaf decomposition?

Climate change is predicted to increase average temperatures and the frequency of extreme weather events, and thus might alter the composition of freshwater communities through effects on climate-sensitive taxa, with uncertain outcomes for the ecosystem processes they regulate. Here we investigated how loses of more environmentally sensitive detritivores alter the key ecosystem process of leaf litter decomposition in a field experiment in two pristine streams with different local shredder assemblages in the Palatinate forest, south-western Germany. We compared bulk leaf decomposition rate and the leaf processing efficiency of shredders in enclosures containing three shredder diversity treatments, where species loss was simulated based on their climate sensitivity. Litter decomposition rates contrasted markedly between survey sites, with a 33% increase and 41% decrease in decomposition following species loss at the first and second site, respectively. Results for the first site suggest that the least sensitive taxa, which were also larger in biomass, contributed most to leaf mass loss, and these were able to compensate for losses of sensitive species, ultimately increasing bulk leaf processing. By contrast, at the second site sensitive species played a more important role in litter decomposition and their loss was not compensated when accounting for detritivore biomass. Our findings demonstrate the importance of the species trait composition of local species pools in regulating the potential effects of changes in assemblage composition caused by climate change.

Evidence for negative effects of ZnO nanoparticles on leaf litter decomposition in freshwater ecosystems

We investigated the negative effects of ZnO nanoparticles (NPs) on ecosystem function by focusing on the process of leaf litter decomposition in an aquatic ecosystem.

Decoupling shredder activity and physical abrasion in leaf litter decomposition process: experiments in the Torna-stream (Hungary) affected by red sludge spill

Leaf litter represents a significant energy source for headwater ecosystems. Its breakdown includes dissolution, microbial activity, fragmentation by shredders, and physical abrasion. As a consequence of red sludge spill that took place in October 2010 in Hungary, the fauna of Torna-stream was killed, offering a “natural laboratory” to measure mass loss without shredder activity. Decomposition of nine leaf litter types was investigated with litter-bag method in 2011 (no macroinvertebrates; post-disaster experiment, POST), 2012 (after macroinvertebrate recolonization, at two sites: POSTRE: impacted site and POSTREF: reference site) in the Torna-stream. In the POST it was possible to measure leaf mass loss without shredder activity and to separate the leaf decomposition rates for each contributor of decomposition with a newly developed model. The model simulates the mass loss through three processes: physical abrasion and drifting, leaching and microbial mineralization, and macroinvertebrate consumption. In 2011, physical abrasion, microbial decomposition, and leaching accounted for 10–50% of initial mass loss, while in the POSTRE and in POSTREF for only 5–47%. The rate of litter decomposition driven by shredders in POST was between 5 and 44%, and in the POSTRE and POSTREF it accounted for 24–90%. The most apparent result of the experiments described in this paper is that the presence or absence of macroinvertebrates determines the decay characteristics and underlines the key role of macroinvertebrates in leaf litter decomposition.

Mesh size and site effects on leaf litter decomposition in a side arm of the River Danube on the Gemenc floodplain (Danube-Dráva National Park, Hungary)

In forested floodplain ecosystems, leaf litter represents an important energy source for aquatic organisms, and its decomposition is a key ecosystem process. In this paper, we investigate the decomposition dynamics of Salix alba, Populus hybrids in the depositional zone of a side arm of the River Danube, and of Fraxinus angustifolia, Ulmus laevis, Quercus robur in the erosional zone. To estimate the effect of small-sized invertebrates, we used litter bags with two mesh sizes (0.04 and 1 mm), and to evaluate the site effects the F. angustifolia leaves were exposed in both sites. Willow and poplar leaf litter decomposed at an intermediate rate; ash and elm decomposed quickly, and the oak decomposed slowly. The faunal exclusion experiments revealed the importance of Chironomidae larvae, which formed the dominant macroinvertebrate taxon in the medium-mesh bags. The initial quality of the leaf litter, especially the N:P ratio, affected the activity of microorganisms, the density of chironomids, and was positively correlated with the breakdown rates. The site conditions had a significant effect on the decay rate and nutrient dynamics. We concluded that the leaf litter decomposition processes and the associated nutrient dynamics are affected by nutrient availability, consumer activity and site conditions.

Effects of terrestrial isopods (Crustacea: Oniscidea) on leaf litter decomposition processes

The leaf litter decomposition is carried out by the combined action of microorganisms and decomposer invertebrates such as earthworms, diplopods and isopods. The present work aimed to evaluate the impact of terrestrial isopod on leaf litter decomposition process. In Lab experimental food sources from oak and magnolia leaves litter were prepared. Air dried leaf litter were cut to 9mm discs and sterilized in an autoclave then soaked in distilled water or water percolated through soil and left to decompose for 2, 4 and 6weeks. 12 groups from two isopods species Porcellio scaber and Armadillidium vulgare, were prepared with each one containing 9 isopods. They were fed individually on the prepared food for 2weeks. The prepared food differed in Carbon stable isotope ratio (δ13C), C%, N% and C/N ratios. At the end of the experiment, isopods were dissected and separated into gut, gut content and rest of the body. The δ13C for the prepared food, faecal pellets, remaining food, gut content, gut and rest of isopod were compared. The feeding activities of the two isopods were significantly different among isopods groups. Consumption and egestion ratios of magnolia leaf were higher than oak leaf. P. scaber consumed and egested litter higher than A. vulgare. The present results suggested that the impact of isopods and decomposition processes is species and litter specific.

Photocatalytic properties of titanium dioxide nanoparticles affect habitat selection of and food quality for a key species in the leaf litter decomposition process

Interactions with environmental parameters may alter the ecotoxicity of nanoparticles. The present study therefore assessed the (in)direct effects of nanoparticulate titanium dioxide (nano-TiO2) towards Gammarus fossarum, considering nano-TiO2's photocatalytic properties at ambient UV-intensities. Gammarids' habitat selection was investigated using its feeding preference on leaf discs either exposed to or protected from UV-irradiation in presence of nano-TiO2 as proxy (n = 49). UV-irradiation alone induced a significant preference for UV-protected habitats, which was more pronounced in simultaneous presence of nano-TiO2. This behaviour may be mainly explained by the UV-induced formation of reactive oxygen species (ROS) by nano-TiO2. Besides their direct toxicity, ROS may have lowered the leaf-quality in UV-exposed areas contributing (approximately 30%) to the observed behavioural pattern. Since the predicted no effect concentration of nano-TiO2 in combination with UV-irradiation falls below the predicted environmental concentration this study underpins the importance of considering environmental parameters during the risk assessment of nanoparticles.

Leaf-litter decomposition of the mangrove speciesAvicennia schaueriana,Laguncularia racemosaandRhizophora mangle

This study evaluated the decomposition process of leaf litter from the main Brazilian mangrove speciesAvicennia schaueriana,Laguncularia racemosaandRhizophora mangle. Senescent leaves were collected, dried and placed in nylon bags with different mesh sizes (fine: 2 × 2 mm and coarse: 8 × 8 mm). The bags were distributed over the sediment, and replicates of each species and mesh size were collected periodically over 4 months. In the laboratory, the dry weight of the samples was measured, and the decomposition coefficient (k) for each species and mesh size was obtained over time. All species showed a rapid decomposition rate at the beginning of the experiment, followed by a slower but steady rate of decomposition over time. The rate of leaf litter decomposition was highest inA. schaueriana, intermediate inL. racemosaand lowest inR. mangle. The difference was mainly linked to the activity and abundance of detritivores, together with the different litter quality of the species, which determined their palatability and probably influenced the decomposition process.