Microbial Decomposition Of Leaf Litter Research Articles

Leaf Species-Dependent Fungicide Effects on the Function and Abundance of Associated Microbial Communities

Microbially-mediated leaf litter decomposition is a critical ecosystem function in running waters within forested areas, which can be affected by fungicides. However, fungicide effects on leaf litter decomposition have been investigated almost exclusively with black alder leaves, a leaf species with traits favourable to consumers (i.e., low recalcitrance and high nutrient content). At the same time, little is known about fungicide effects on microbial colonisation and decomposition of other leaf species with less favourable traits. In this 21 day lasting study, we explore the effects of increasing fungicide sum concentrations (0–3000 µg/L) on microbial colonisation and decomposition of three leaf species (black alder, Norway maple and European beech) differing in terms of recalcitrance and nutrient content. Leaf litter decomposition rate, leaf-associated fungal biomass and bacterial density were quantified to observe potential effects at the functional level. Beech, as the species with the least favourable leaf traits, showed a substantially lower decomposition rate (50%) in absence of fungicides than alder and maple. In the presence of high fungicide concentrations (300–3000 µg/L), beech showed a concentration-related decrease not only in microbial leaf litter decomposition but also fungal biomass. This suggests that favourable traits of leaf litter (as for alder and maple) enable leaf-associated microorganisms to acquire leaf-bound energy more easily to withstand potential effects induced by fungicide exposure. Our results indicate the need to deepen our understanding on how leaf species’ traits interact with the impact of chemical stressors on the leaf decomposition activity of microbial communities.

Tracer or toxicant: Does stable isotope labeling affect central processes in aquatic food webs?

Stable isotope analysis (SIA) is an elementary technique in food web ecology, but its insights become increasingly ambiguous in complex systems. One approach to elevate the utility of SIA in such systems is the use of heavy isotope tracers (i.e., labeling). However, the fundamental assumption that the addition of such tracers does not affect in situ conditions has been challenged. This study tests if labeling is suitable for autotrophy-based and detritus-based aquatic food webs. For the former, the survival and reproduction of Daphnia magna fed with phytoplankton cultured at different levels of 15N addition were assessed. For the latter, the microbial decomposition of leaf litter was assessed at the same tracer levels. While no significant differences were observed, effect patterns were comparable to a previous study, supporting the isotopic redundancy hypothesis that postulates discrete quantum mechanical states at which the reaction speeds of metabolic processes are altered. Although physiology (reproduction) and activity (microbial decomposition) might not be altered to an ecologically significant level, labeling with heavy stable isotopes could potentially affect isotopic fractionation in biochemical processes and bias conclusions drawn from resulting SI ratios.

Contrasting the effects of microplastic types, concentrations and nutrient enrichment on freshwater communities and ecosystem functioning

Microplastics are now ubiquitous in freshwater environments. As most previous research has focused on species-specific effects of microplastics under controlled laboratory conditions, little is known about the impact of microplastics at higher levels of ecological organisation, such as freshwater communities and their associated ecosystem functions. To fill this knowledge gap, an outdoor experiment using 40 freshwater mesocosms, each 1.57 m3, was used to determine the effects of (i) microplastic type: traditional oil-based high-density polyethylene versus bio-based biodegradable polylactic acid, (ii) concentration of microplastic particles and (iii) nutrient enrichment. The two concentrations of microplastics used were equivalent to measured environmentally occurring concentrations and concentrations known to cause toxicological effects under laboratory conditions. Freshwater communities are also at increasing risk from nutrient enrichment, which can alter community composition in favour of competitively dominant taxa. The independent and interactive effects of these treatments on pelagic community structure (phytoplankton standing stock, taxonomic richness, and composition) and ecosystem functioning (periphyton productivity and leaf litter decomposition) were assessed. Taxonomic richness and community composition were not affected by exposure to the experimental treatments and there were no significant treatment effects on phytoplankton standing stock, periphyton productivity, total or microbial leaf litter decomposition. Overall, multiple microplastic exposures, crossed with nutrient addition had little impact on the structure and functioning of semi-natural freshwater ecosystems. These findings indicate that the negative impacts of microplastics predicted from species-specific studies may not be readily realised at the ecosystem scale.

Fate of leaf litter in restored Kandelia obovata (S. L.) mangrove forests with different ages in Jiulong River Estuary, China

Ecological processing of leaf litter plays important roles in carbon dynamics of mangrove forests. Fate of leaf litter, that is, removal by crabs, microbial decomposition, and tidal export was quantified in two restored Kandelia obovata forests with ages of 24 years and 48 years, respectively, from December 2009 to November 2010. Crab abundance was also investigated to test the role of crabs in leaf litter processing. Daily leaf litter production was 1.064 ± 0.108 g C m−2 day−1 at the 24‐year forest and was 0.689 ± 0.040 g C m−2 day−1 at the 48‐year forest. Annual mean removal of leaf litter by crabs was lower at the 24‐year forest than at the 48‐year forest (0.177 ± 0.046 g C m−2 day−1 vs. 0.220 ± 0.050 g C m−2 day−1), due to a higher crab abundance at the older forest. Microbial decomposition and change in standing stock of leaf litter on the forest floor made a negligible contribution to the annual leaf litter production. Tidal exports of leaf litter were estimated as 0.875 ± 0.090 g C m−2 day−1 and 0.458 ± 0.086 g C m−2 day−1 at the 24‐year and 48‐year forests, respectively, accounting for 82.2% and 66.5% of their daily leaf litter production. Turnover rate of leaf litter was higher at the younger forest (1.7 ± 0.4 day−1) than the older forest (1.2 ± 0.3 day−1). Removal of leaf litter by crabs was higher in warm months while tidal export of leaf litter showed a much less apparent seasonal pattern. Spatial variations of crab removal and tidal export of leaf litter with forest zones were observed within each forest, while microbial decomposition of leaf litter was comparable among the different zones. These indicated that the ecosystem functions of restored mangrove forest could not reach a level equivalent to those of a mature forest even 24 years after restoration.

Responses of microbially driven leaf litter decomposition to stream nutrients depend on litter quality

The present study aims to understand how microbial decomposition of leaf litter from two riparian tree species differing in their quality varies among streams covering a gradient of nutrient concentrations. We incubated leaf litter from alder (Alnus glutinosa) and sycamore (Platanus × hispanica) in 3 streams with low human pressure and 2 streams influenced by wastewater treatment plant effluents. We quantified leaf litter decomposition rates (k) and examined the temporal changes in the leaf litter concentrations of carbon (C) and nitrogen (N) throughout the incubation period. We measured the extracellular enzyme activities involved in degradation of C (i.e., cellobiohydrolase) and organic phosphorus (i.e., phosphatase). Results showed that alder k decreased with increasing nutrient concentrations, while sycamore decomposed similarly among streams. For both species, leaf litter N concentrations were positively related to in-stream dissolved N concentrations. However, we found different temporal patterns of leaf litter N concentrations between species. Finally, we found relevant differences in the enzymatic activities associated to each leaf litter species across the nutrient gradient. These results suggest that the intrinsic characteristics of the leaf litter resources may play a relevant role on the microbially driven leaf litter decomposition and mediate its response to dissolved nutrient concentrations across streams.

Contrasting habitats but comparable microbial decomposition in the benthic and hyporheic zone

Input of allochthonous leaf litter is the main carbon source for heterotrophic metabolism in low-order forested streams. A major part of this leaf litter is accumulated at benthic retention structures or buried in the hyporheic zone. As a result of hyporheic sediment characteristics, hyporheic physicochemistry differs from that of the benthic zone selecting the microbial community. The present study aimed at understanding the influence of the hydrological and physiochemical differences between the benthic and hyporheic zone on microbial leaf litter decomposition and on the structure and function of the associated microbial community. Leached leaves of Alnus glutinosa were exposed for 62days in 250-μm mesh bags in the benthic zone and buried in the hyporheic zone at a depth of 2–3cm. Decomposition rates were comparable for both zones. In contrast, respiration, bacterial abundance, ergosterol content, fungal spore production and richness of fungal morphotypes were lower associated with hyporheic than with benthic leaves. Microbial community structure displayed zone-dependent temporal dynamics. Thus, the microbial community carried out leaf litter decomposition independently of its structure. These results suggest that carbon processing is not necessarily impaired by environmental constraints because the community structure may compensate those constraints (i.e. functional redundancy).

Species-specific effects of earthworms on microbial communities and the fate of litter-derived carbon

Soil respiration is frequently measured as a surrogate for biological activities and is important in soil carbon cycling. The heterotrophic component of soil respiration is primarily driven by microbial decomposition of leaf litter and soil organic matter, and is partially controlled by resource availability. In North American temperate deciduous forests, invasive European and Asian earthworms are known to variously affect soil properties and resource availability through their feeding, burrowing, and casting behaviors, and may affect different components of soil respiration through modulating the microbial communities. By tracing litter-derived C from 13C and 15N double-enriched leaf litter into soil and CO2 efflux in a mesocosm experiment, we tested the hypothesis that earthworms inhibit litter C-derived soil respiration by reducing resource availability and microbial biomass, and further examined how species-specific effects of earthworms on soil respiration are mediated by soil microbial community. We showed that while earthworms generally had no effect on total soil respiration, the interaction between Octolasion lacteum and Lumbricus rubellus had a significant negative non-additive effect, presumably through affecting anaerobic microsites in the soil. Moreover, litter C-derived soil respiration was reduced by the Asian Amynthas hilgendorfi, the European L. rubellus, and the North American native species Eisenoides lonnbergi, but not by the European species O. lacteum. Phospholipid fatty acid (PLFA) analysis and structural equation modeling indicated that while soil bacteria and fungi abundances were affected by earthworm species identities, the observed reduction of litter C-derived soil respiration could not be fully explained by changes in microbial biomass. We attributed these effects to earthworm-induced aggregate formation, reduction of microbial transformation of labile carbon, and antimicrobial peptide activities, and concluded that the mechanisms through which the four earthworm species affect the fate of litter-derived C and its mineralization are species-specific.

Inorganic fungicides as routinely applied in organic and conventional agriculture can increase palatability but reduce microbial decomposition of leaf litter

Summary The application of fungicides is considered an indispensable measure to secure crop production. These substances, however, may unintentionally enter surface waters via run‐off, potentially affecting the microbial community. To assess such risks adequately, authorities recently called for suitable test designs involving relevant aquatic micro‐organisms. We assessed the structural and functional responses of leaf‐associated microbial communities, which play a key role in the breakdown of allochthonous leaf material in streams, towards the inorganic fungicides copper (Cu) and elemental sulphur (S). These substances are of particular interest as they are authorized for both conventional and organic farming in many countries of the world. We used the food choice of the amphipod shredder Gammarus fossarum (indicative for micro‐organism‐mediated leaf palatability) as well as microbial leaf decomposition as functional endpoints. Moreover, the leaf‐associated microbial communities were characterized by means of bacterial density, fungal biomass and community composition facilitating mechanistic understanding of the observed functional effects. While Gammarus preferred Cu‐exposed leaves over unexposed ones, microbial leaf decomposition was reduced by both Cu and S (up to 30%). Furthermore, Cu exposure decreased bacterial densities (up to 60%), stimulated the growth of leaf‐associated fungi (up to 100%) and altered fungal community composition, while S did not affect any of the assessed structural endpoints. Synthesis and applications. We observed both structural and functional changes in leaf‐associated microbial communities at inorganic fungicide concentrations realistic for surface water bodies influenced by conventional and organic farming. Our data hence justify a careful re‐evaluation of the environmental safety of the agricultural use of these compounds. Moreover, inclusion of an experimental design similar to the one used in this study in lower tier environmental risk assessments of antimicrobial compounds may aid to safeguard the integrity of aquatic microbial communities and the functions they provide.

Nutrient Dynamics Associated with Leaching and Microbial Decomposition of Four Abundant Mangrove Species Leaf Litter of the Sundarbans, Bangladesh

Release of nutrients and organic matter from mangrove litter during the leaching and decomposition processes play an important role in the biogeochemical cycling in mangrove ecosystems. Mass loss and nutrient dynamics associated with leaching and microbial decomposition of leaf litter of Heritiera fomes, Excoecaria agallocha, Ceriops decandra and Xylocarpus mekongensis were studied in the Sundarbans. The initial mass of H. fomes, E. agallocha, C. decandra and X. mekongensis leaf litter was significantly decreased to 11 %, 18 %, 21 % and 19 % respectively after 168 h of leaching process. Irrespectively, mass loss due to the microbial decomposition was higher for E. agallocha (97 %) followed by X. mekongensis (74 %), C. decandra (44 %) and H. fomes (42 %) after 7 months. Highest amount of N (3.29 mg/g) was released from leaf litter of C. decandra and the highest amount of P (1.69 mg/g) and K (16.36 mg/g) was released from E. agallocha. Comparatively higher amount of N (6.36 mg/g), P (2.68 mg/g) and K (16.41 mg/g) was released from the leaf litter of E. agallocha than others. Our results are useful for estimating the total flux of nutrients of mangrove forest ecosystem, especially where the studied mangrove species occur abundantly.

Effects of burial on leaf litter quality, microbial conditioning and palatability to three shredder taxa

Summary 1. Heterotrophic microorganisms are crucial for mineralising leaf litter and rendering it more palatable to leaf‐shredding invertebrates. A substantial part of leaf litter entering running waters may be buried in the streambed and thus be exposed to the constraining conditions prevailing in the hyporheic zone. The fate of this buried organic matter and particularly the role of microbial conditioning in this habitat remain largely unexplored.2. The aim of this study was to determine how the location of leaf litter within the streambed (i.e. at the surface or buried), as well as the leaf litter burial history, may affect the leaf‐associated aquatic hyphomycete communities and therefore leaf consumption by invertebrate detritivores. We tested the hypotheses that (i) burial of leaf litter would result in lower decomposition rates associated with changes in microbial assemblages compared with leaf litter at the surface and (ii) altered microbial conditioning of buried leaf litter would lead to decreased quality and palatability to their consumers, translating into lower growth rates of detritivores.3. These hypotheses were tested experimentally in a second‐order stream where leaf‐associated microbial communities, as well as leaf litter decomposition rates, elemental composition and toughness, were compared across controlled treatments differing by their location within the streambed. We examined the effects of the diverse conditioning treatments on decaying leaf palatability to consumers through feeding trials on three shredder taxa including a freshwater amphipod, of which we also determined the growth rate.4. Microbial leaf litter decomposition, fungal biomass and sporulation rates were reduced when leaf litter was buried in the hyporheic zone. While the total species richness of fungal assemblages was similar among treatments, the composition of fungal assemblages was affected by leaf litter burial in sediment.5. Leaf litter burial markedly affected the food quality (especially P content) of leaf material, probably due to the changes in microbial conditioning. Leaf litter palatability to shredders was highest for leaves exposed at the sediment surface and tended to be negatively related to leaf litter toughness and C/P ratio. In addition, burial of leaf litter led to lower amphipod growth rates, which were positively correlated with leaf litter P content.6. These results emphasise the importance of leaf colonisation by aquatic fungi in the hyporheic zone of headwater streams, where fungal conditioning of leaf litter appears particularly critical for nutrient and energy transfer to higher trophic levels.

Mixtures of zinc and phosphate affect leaf litter decomposition by aquatic fungi in streams

To better understand the impacts of multiple stressors in freshwaters, we investigated the effects of mixtures of zinc and inorganic phosphorus on microbial decomposition of leaf litter. Alder leaves were colonized in a stream and placed in microcosms with stream water supplemented or not with 3 concentrations of zinc (Zn up to 9.8 mg/l) or phosphate (P–PO 4 3− up to 0.5 mg/l), alone and in all possible combinations. We measured leaf mass loss, and fungal biomass, reproduction and diversity. In control microcosms, 23 species of aquatic hyphomycetes were identified on leaves, and the exposure to the highest zinc concentration reduced diversity to 14 species. Articulospora tetracladia was the dominant species followed by Flagellospora sp. and Alatospora acuminata. The exposure to phosphate increased the contribution of A. acuminata, but this species was negatively affected by zinc. Under high zinc stress, Varicosporium elodeae increased its contribution to the total conidial production. The exposure to high zinc concentration, alone or in mixtures with phosphate, led to shifts in fungal community structure, as indicated by cluster analysis based on sporulation data and denaturing gradient gel electrophoresis (DGGE) fingerprints of fungal DNA. These changes were accompanied by a reduction in leaf decomposition, particularly in mixtures with high Zn concentration, in which leaf mass loss was 30% lower than in the control. This suggests that the co-occurrence of zinc and phosphate may have negative effects on stream ecosystem functioning. However, we did not detect decreased leaf-associated fungal biomass and sporulation, probably because a delay in fungal colonization occurred due to the presence of stressors.

Copper and zinc mixtures induce shifts in microbial communities and reduce leaf litter decomposition in streams

Summary1. To assess the impact of metal mixtures on microbial decomposition of leaf litter, we exposed leaves previously immersed in a stream to environmentally realistic concentrations of copper (Cu) and zinc (Zn) (three levels), alone and in all possible combinations. The response of the microbial community was monitored after 10, 25 and 40 days of metal exposure by examining leaf mass loss, fungal and bacterial biomass, fungal reproduction and fungal and bacterial diversity.2. Analysis of microbial diversity, assessed by denaturing gradient gel electrophoresis and identification of fungal spores, indicated that metal exposure altered the structure of fungal and bacterial communities on decomposing leaves.3. Exposure to metal mixtures or to the highest Cu concentration significantly reduced leaf decomposition rates and fungal reproduction, but not fungal biomass. Bacterial biomass was strongly inhibited by all metal treatments.4. The effects of Cu and Zn mixtures on microbial decomposition of leaf litter were mostly additive, because observed effects did not differ from those expected as the sum of single metal effects. However, antagonistic effects on bacterial biomass were found in all metal combinations and on fungal reproduction in metal combinations with the highest Cu concentrations, particularly at longer exposure times.

Comparing field and laboratory breakdown rates of coarse particulate organic matter: Sediment dynamics mask the impacts of dissolved nutrients on CPOM mass loss in streams

Microbial decomposition of leaf litter and woody debris is stimulated by an increase in dissolved nutrients. Thus, breakdown rates of coarse particulate organic matter (CPOM) might be useful for assessing the impact of eutrophication on stream ecosystems. The objective of this study was to compare breakdown rates of leaf litter, toothpicks, and twigs in an upland stream (Ilm, Thuringia, Germany) and two of its tributaries to determine the best CPOM type for investigating moderate eutrophication effects on CPOM mass loss. A total of 160 fine-mesh bags (1 mm) that excluded invertebrate shredders were exposed at 4 sampling sites from December 2004 to May 2005. Simultaneously, CPOM was incubated in aquaria filled with ambient stream water from each of the 4 study sites under standardized conditions. In aquaria, toothpicks showed increasing breakdown rates in treatments with increasing dissolved nutrient concentrations, whereas no significant effects on breakdown rates of beech leaves and twigs were detected. In the field, physical fragmentation due to high velocities and sediment transport at 3 sites dominated by gravels accelerated leaf breakdown rates. In the sandy tributary, bags were covered by deposited sand that might have decreased leaf breakdown rates despite high nutrient concentrations. Mass loss of the woody debris (toothpicks and twigs) was affected by abrasion in the gravel streams and by burying in the sand stream, but to a lesser extent than leaf litter. Thus, physical fragmentation by abrasion and grinding of CPOM by moving sediment can mask the effect of nutrients on breakdown rates. Because of a fast breakdown rate and resistance to fragmentation, toothpicks could be used as a tool to assess water quality in streams with low to intermediate flow velocities.

Anthropogenic stress may affect aquatic hyphomycete diversity more than leaf decomposition in a low-order stream

Fungal diversity and microbial decomposition of leaf litter were examined in a low-order stream at a reference and an impacted site. The latter, 10 km downstream of the reference site, has high nutrient loads from domestic sewage and agriculture, and increased heavy metal levels in the stream water and sediments. At the polluted site aquatic hyphomycete diversity and sporulation were reduced, whereas fungal biomass and leaf decomposition rate were not. Articulospora tetracladia and Flagellospora sp. were the dominant species at the reference site, and Dimorphospora foliicola was dominant at the polluted site. Biomass of bacteria was higher at the polluted site, but only approached 10 % of fungal biomass, indicating that fungi remained the main microbial decomposers. In addition, the results suggest that aquatic hyphomycete communities may respond to stress according to the redundancy model, in which overall function remains stable because increased biomasses of tolerant species compensate for the loss of sensitive species.

Correlation of foliage and litter chemistry of sugar maple, Acer saccharum, as affected by elevated CO2 and varying N availability, and effects on decomposition

Rising atmospheric carbon dioxide has the potential to alter leaf litter chemistry, potentially affecting decomposition and rates of carbon and nitrogen cycling in forest ecosystems. This study was conducted to determine whether growth under elevated atmospheric CO2 altered the quality and microbial decomposition of leaf litter of a widely distributed northern hardwood species at sites of low and high soil nitrogen availability. In addition, we assessed whether the carbon–nutrient balance (CNB) and growth differentiation balance (GDB) hypotheses could be extended to predict changes in litter quality in response to resource availability. Sugar maple (Acer saccharum) was grown in the field in open‐top chambers at 36 and 55 Pa partial pressure CO2, and initial soil mineralization rates of 45 and 348 μg N g−1 d−1. Naturally senesced leaf litter was assessed for chemical composition and incubated in the laboratory for 111 d. Microbial respiration and the production of dissolved organic carbon (DOC) were quantified as estimates of decomposition. Elevated CO2 and low soil nitrogen resulted in higher litter concentrations of nonstructural carbohydrates and condensed tannins, higher C/N ratios and lower N concentrations. Soil N availability appears to have had a greater effect on litter quality than did atmospheric CO2, although the treatments were additive, with highest concentrations of nonstructural carbohydrates and condensed tannins occurring under elevated CO2–low soil N. Rates of microbial respiration and the production of DOC were insensitive to differences in litter quality. In general, concentrations of litter constituents, except for starch, were highly correlated to those in live foliage, and the CNB/GDB hypotheses proved useful in predicting changes in litter quality. We conclude the chemical composition of sugar maple litter will change in the future in response to rising atmospheric CO2, and that soil N availability will exert a major control. It appears that microbial metabolism will not be directly affected by changes in litter quality, although conclusions regarding decomposition as a whole must consider the entire soil food web.

X-ray microanalysis and microbial colonization of leaves in Lake Wallenpaupack in eastern Pennsylvania

The microbial decomposition of leaf litter provides a major source of organic carbon and other nutrients and is important in ensuring the stability of lake ecosystems. Lake leaf litter can also act as a sink for immobilization of nutrients and elements. This investigation utilizes the scanning electron microscope and the energy-dispersive x-ray microanalysis technique to study the effects of agricultural or septic tank leakage pollutants on microbial colonization and elemental accumulation in leaves submerged in a lake in eastern Pennsylvania.White oak and red maple leaves were placed in mesh bags in the littoral zone of three cove sites at lake Wallenpaupack, a 13 mile-long, 5,700 acre lake located in the Pocono Mountains in eastern Pennsylvania. Cove 1 was surrounded by a wooded area and received water input from a wetland preserve. Cove 2 was suspected of contamination by septic tank leakage. Cove 3 received water input from a tributary passing through a heavily farmed drainage basin.

Effect of fertilizer on microbial decomposition of leaf litter of a regenerating bush-fallow in sub-humid tropical Nigeria

A 5-month study of the effects of urea and NPK-mixtures on microbial litter decomposition process was carried out on the leaf litter of a regenerating secondary forest at Ile-Ife, Nigeria. The litter was treated with urea and an NPK-mixture separately at three levels of concentrations calculated on the basis of the fertilizers. Addition of urea and an NPK-mixture at 5, 10 and 15 mg g −1 air-dried litter increased microbial population, activity and the rate of decomposition of litter as compared with the control. In the case of the NPK-mixture, the increase was more pronounced as the concentration increased, but in the case of urea, the increasing trend was reversed after two months, even though bacterial population maintained a steady increase. The nutrient element dynamics of decomposing leaf litter in relation to fertilizer treatment was examined. N, P and Mg concentrations in leaf litter declined in the first two months of sampling. However, N and P remained relatively constant despite about 30% loss in weight of leaf litter during subsequent sampling periods. The rate of loss of Mg was somewhat faster than that of the organic matter. K and Ca showed marked contrasts both with N, P and Mg and with one another.

Microbial decomposition of leaf litter as influenced by pesticides

Microbial decomposition of leaf litter as influenced by pesticides

Microbial decomposition of leaf litter as influenced by fertilizers

The application of dithane M-45, 2, 4-D and carbofuran at the rates of 1, 5 and 10 mg (active ingredients) per g air-dry litter caused insignificant variations in the microbial populations in decomposing leaf litter. The qualitative nature of mycoflora, was altered, a little, with regard to the total number of species and relative abundance of a few species. The variations in CO2 evolution was significant only in relation to the fungicidal treatment. Percent weight loss of treated and untreated litter differed insignificantly at the end except in the case of fungicidal treatment. The present study infers that the used concentrations of the test pesticides may be recommended in tropical forestry as their application does not pose any potential threat to the process of natural decomposition of the leaf litter.