Leaf Litter Decomposition Rates Research Articles

Functional Traits and Species Identity Drive Decomposition Along a Successional Gradient in Upper Andean Tropical Forests

ABSTRACTLeaf litter decomposition constitutes one of the most vital processes for maintaining productivity and carbon release in ecosystems. However, this remains one of the least understood processes in upper Andean tropical forests (UATF), a highly diverse ecoregion that has undergone extensive transformation over the centuries. In this study, we aimed to determine the relationships between decomposition rates of leaf litter, leaf functional traits, and microclimatic conditions along a successional gradient of UATF. We also tested the “after‐life effect” by analyzing changes between green and senescent leaves. We performed a fully reciprocal translocation experiment with 15 representative species of UATF in a set of 14 permanent plots by using 2520 litterbags distributed across 42 experimental units (three litterbeds per plot), over 1.5 years, with four harvesting times (3, 6, 12, and 18 months). Chemical and physical traits were measured in green and senescent leaves to identify the best predictors of decomposition and to analyze the “after‐life effect.” We found that functional traits and species identity drive litter decomposition in UATF, rather than succession and microclimatic conditions of soil moisture and temperature. The relative importance of traits was prevalent in all stages of decay, despite being stronger in the early phases. Although we found an “after‐life effect” of green leaves in decomposition, changes in chemical composition from green to senescent leaves indicated substantial nitrogen resorption, which is a limiting resource in tropical montane forests. With the increasing landscape transformation in UATF, changes in plant species composition could have profound impacts by altering decomposition rates, nutrient cycling, and global carbon storage.

Roles of Chromolaena odorata, macrofauna, and forest edge on the decomposition rate of tree leaf litter in two types of seasonally dry tropical forest

Roles of <i>Chromolaena odorata</i>, macrofauna, and forest edge on the decomposition rate of tree leaf litter in two types of seasonally dry tropical forest

Non-native palm affects arthropod communities and litter decomposition in an ongoing biome shift

The emergence of novel ecosystems, characterized by shifts in species composition and interactions, abiotic conditions and altered ecosystem functioning, is a major and inevitable challenge to contemporary ecosystem management. This study examines the ecological implications of Trachycarpus fortunei, a non-native evergreen palm, currently involved in a biome shift from deciduous temperate forest to evergreen laurophyllous forest in the Southern European Alps. Specifically, we investigated the effects of T. fortunei encroachment in peri-urban forests on flying and ground-dwelling arthropod communities as well as on leaf-litter decomposition. We found that the presence of T. fortunei altered arthropod community composition, mostly by reducing the number of herbivore species. This effect was likely driven by the lower quality of palm leaves as a food source compared to deciduous, dicotyledonous tree leaves and by a lower plant richness in the herb and shrub layer. Furthermore, we observed higher rates of leaf-litter decomposition associated with increasing abundance of young palm trees, which was not explained by predictors commonly associated with litter decomposition (i.e., detritivore abundance, litter depth and air temperature). Hence, the slow decay of palm leaves appears to be counterbalanced by the favourable conditions for litter decomposition within dense palm stands. Overall, our findings indicate that high densities of the non-native palm species (T. fortunei) impacts herbivore arthropod communities in the Southern European Alps, providing first evidence of possible effects on ecosystem functioning of this ongoing biome shift. These outcomes are integral components of the broader process of laurophyllisation in the study region, a phenomenon linked to climate warming and land use change, encompassing both native and non-native species.

Nitrogen Deposition Reduces the Rate of Leaf Litter Decomposition: A Global Study

The litter decomposition of plant leaves is a vital process in carbon (C) and nitrogen (N) cycling in global terrestrial ecosystems. However, previous assessments of the key determinants of the N deposition effects of litter decomposition have been more controversial. In this meta-analysis, we compared the overall effects of N addition on the litter decomposition rates, litter nutrient content (C and N), and litter constituent (lignin and cellulose) residual rates using a log response ratio approach. Our results showed that exogenous N addition increased the N content and inhibited lignin degradation in litter. N deposition decreased the leaf litter decomposition rate by increasing the lignin and N residues and decreasing the litter C content and soil pH. The analysis also concluded that the initial litter C/N ratio, lignin content, and soil pH were main factors in mediating the effect of N deposition on litter decomposition rate. Overall, the results of this study indicate that N deposition can slow decomposition rates by inhibiting N release and lignin degradation of litter. Notably, these results emphasize that the effect of N deposition on litter decomposition mainly depends on the endogenous quality of the litter and soil pH in the decomposition environment.

Variability in the home-field advantage of litter decomposition mediates alterations in soil CO2 and CH4 fluxes: A transplantation experiment study

The decomposition of litter is susceptible to the influence of climate change and soil conditions, which can subsequently impact the release of carbon dioxide (CO2) from forest soils and the absorption of methane (CH4). Ecological theory proposes the existence of a home-field advantage (HFA) in litter decomposition, suggesting that the decomposition rate of litter (such as fallen leaves, twigs, and roots) may be faster in their native habitat than in foreign environments. Therefore, we selected litter from Pinus tabuliformis (PT) and Quercus acutissima Carruth (QC) in the field and conducted a 439-day litter transplant experiment to test the magnitude and direction of the HFA of these two litter types in three forest stands. During this experiment, we monitored the changes in soil CO2 and CH4 fluxes associated with the decomposition of PT and QC leaf litter in their native and foreign sites. Furthermore, we measured various soil physical, chemical, and biological indicators. The results indicated that the decomposition rate of QC leaf litter was faster in its native habitat, demonstrating a clear HFA effect. Conversely, the decomposition of PT leaf litter was observed to be more rapid in away soil, suggesting a pronounced home-field disadvantage (HFD). The study found that PT leaf litter exhibited greater CO2 release when decomposing in away soil, demonstrating 43 % and 32 % increases compared to bare soil, respectively. Conversely, QC leaf litter was observed to release more CO2 in its home soil. Additionally, the bare soils of the PT and QC home sites were found to absorb more CH4 compared to leaf litter coverage, with increases of 37.8 % and 31.2 %, respectively. The partial least squares model indicated that the litter attributes had a significant direct effect on soil temperature and enzyme activity. Soil temperature and enzyme activity further directly influenced the soil CO2 and CH4 fluxes. The results of our study indicate that the HFA of litter is dependent on litter type, and that litter transplantation can impact soil greenhouse gas exchange. This research provides a theoretical foundation for forest management and conservation strategies, as well as valuable data for global carbon neutrality efforts.

Response of stream habitat and microbiomes to spruce budworm defoliation: New considerations for outbreak management.

Defoliation by eastern spruce budworm is one of the most important natural disturbances in Canadian boreal and hemi-boreal forests with annual area affected surpassing that of fire and harvest combined, and its impacts are projected to increase in frequency, severity, and range under future climate scenarios. Deciding on an active management strategy to control outbreaks and minimize broader economic, ecological, and social impacts is becoming increasingly important. These strategies differ in the degree to which defoliation is suppressed, but little is known about the downstream consequences of defoliation and, thus, the implications of management. Given the disproportionate role of headwater streams and their microbiomes on net riverine productivity across forested landscapes, we investigated the effects of defoliation by spruce budworm on headwater stream habitat and microbiome structure and function to inform management decisions. We experimentally manipulated a gradient of defoliation among 12 watersheds during a spruce budworm outbreak in the Gaspésie Peninsula, Québec, Canada. From May through October of 2019-2021, stream habitat (flow rates, dissolved organic matter [DOM], water chemistry, and nutrients), algal biomass, and water temperatures were assessed. Bacterial and fungal biofilm communities were examined by incubating six leaf packs for five weeks (mid-August to late September) in one stream reach per watershed. Microbiome community structure was determined using metabarcoding of 16S and ITS rRNA genes, and community functions were examined using extracellular enzyme assays, leaf litter decomposition rates, and taxonomic functional assignments. We found that cumulative defoliation was correlated with increased streamflow rates and temperatures, and more aromatic DOM (measured as specific ultraviolet absorbance at 254 nm), but was not correlated to nutrient concentrations. Cumulative defoliation was also associated with altered microbial community composition, an increase in carbohydrate biosynthesis, and a reduction in aromatic compound degradation, suggesting that microbes are shifting to the preferential use of simple carbohydrates rather than more complex aromatic compounds. These results demonstrate that high levels of defoliation can affect headwater stream microbiomes to the point of altering stream ecosystem productivity and carbon cycling potential, highlighting the importance of incorporating broader ecological processes into spruce budworm management decisions.

Decomposition of Foliar Litter from Dominant Plants of Desert Riparian Forests in Extremely Arid Regions

Litter decomposition is important for understanding the effects of habitat on nutrient cycling. In this study, we investigated the decomposition characteristics, decomposition variability, and regulatory factors restricting the decomposition rates of leaf litter in three different habitats: a flood disturbance habitat, an arid habitat, and a high-salinity habitat. The litter decomposition rates of the habitats decreased in the following order: flood disturbance habit &gt; arid habitat &gt; high-salinity habitat. The organic carbon, total nitrogen, and lignin residues of the litter during the decomposition period were highest in the high-salinity habitat. The litter quality was the main regulator of the release of phosphorus and cellulose residues, which exhibited different release processes and patterns in these three habitats. The litter decomposition coefficient was negatively correlated with litter carbon residue in the flood disturbance habitats, the lignocellulose index in the arid habitats, and soil urease in the high-salinity habitats. It was positively correlated with the lignocellulose index in flood disturbance habitats and litter carbon residue in high-salinity habitats. The litter quality in the flood disturbance area played a significant role in litter decomposition, while environmental quality and litter quality were the dominant factors under arid and high-salt conditions. Litter quality in the flood disturbance area played a significant role in litter decomposition, while both environmental quality and litter quality were the dominant factors under arid and salt conditions.

Impact of Fertilizers Application on Leaf Litter Decomposition and Nutrient Cycling in White Poplar (Populus alba L.) Forest Ecosystem

Fertilizer application plays a crucial role in the decomposition of white poplar leaf litter and cycling of nutrients within forest ecosystems. The impact of various fertilizer additions on white poplar leaf litter and nutrient cycling is poorly understood. In this study, seven treatments were conducted at the following levels: Control (CK), no adding mineral fertilizers, N fertilization (+N), N and P fertilization (+NP), N, P, K fertilization (+NPK), P, K (+PK), manure fertilizer (+MF), and bird fertilizers (+BF) in a white poplar plantation in Qadis district, and used the litterbag techniques to measure litter mass remaining. The main objectives of our study were: (1) to explore the response of white poplar leaf litter decomposition to various fertilizers and accelerate the decomposition process; (2) to examine the relationship between C, N, and P concentration and their stoichiometric characteristic in leaf litter and soil. In this investigation, our results showed that white poplar leaf litter was significantly affected by fertilizers, and the decomposition process was greatly accelerated with + MF, +NPK, and + BF. The decay rate constant k (year −1) shows the decomposition rate of white poplar leaf litter as follows: +MF > +NPK > +BF > +PK > +NP > +N > CK (0.56, 0.53, 0.52, 0.51,0.51,0.5, and 0.46). Soil nutrients N, P and K increased significantly during the decomposition time with + MF, +NPK, and + BF, respectively, while C:N, C:P, and N:P ratios were highest in the white poplar leaf litter, and lowest in soil, we observed significant association between nutrients concentrations in soil and white poplar leaf and their stoichiometric. This current study concluded that adding + MF, +NPK and + BF fertilizers might be the preferred management option as they provided potentially beneficial changes in leaf litter decomposition and increased nutrient concentration. The data obtained will be a valuable reference for fertilization management strategies in forest ecosystems.

Decomposition rate of Rhizophora mucronata leaf litter and identification of fungi in mangrove ecosystems in Pulau Sembilan, Pangkalan Susu District, Langkat Regency

Mangrove leaves that fall to the ground play an important role in transferring organic matter from plants into the soil. Organic matter from leaf decomposition is important for mangrove growth and as a food source for ecosystems in the surrounding waters. This study aims to determine the rate of decompositionof Rhizophora mucronate leaves, thelevels of carbohydrates and proteins contained in the decomposed leaves, and the species of fungi present in the leaves. Research samples were taken from mangrove forest areas in Pulau Sembilan, Pangkalan Susu District, Langkat Regency, decomposition rate testing and fungi identification were carried out at the forest cultivation laboratory, Faculty of forestry, University of North Sumatra. The research was conducted from June to December 2022. The results showed that the decomposition rate was 5.9 and there were 5 species of fungi found in the leaves that had undergone decomposition, namely Aspergillus niger, Aspergillus oryzae, Aspergillus fumigatus, Aspergillus glaucus, Aspergillus clatavus. The carbohydratecontent decreased during decomposition, with the highest content in the control on day 30 at10.7% and at the end of the 90th day observation only 1.89%. The remaining leaf litter of R.mucronata was 9.16 g with a weight loss of 30.84 g and a decomposition rate percentage of 22.89% on day 15 had the lowest weight loss of leaf litter, the remaining leaf litter was 22.86g with a weightloss of 17.14 gand a decomposition ratepercentage of 57.15%.

Limited recovery of soil organic carbon and soil biophysical functions after old field restoration in an agricultural landscape

AbstractThe conversion of woodland ecosystems to agricultural landscapes has led to unprecedented losses of biodiversity and ecosystem functioning globally. Unsustainable agricultural practices have contributed to the degradation of soil's physical and biogeochemical properties. Ecological restoration of unproductive agricultural land is imperative for reversing land degradation and ameliorating the degrading effects of agriculture on biodiversity and ecosystem functions. However, it is unclear to what extent common restoration activities, such as tree planting, can facilitate the recovery of ecosystem condition and in particular, improve soil physical, biogeochemical and biotic components. Here, we investigated how the cessation of cropping, followed by tree planting, affected soil carbon concentrations and key biophysical soil functions. Data were collected across 10 sites a decade after the replanting of woody species on old fields in semi‐arid Western Australia. We applied a chronosequence approach and measured soil functions in fallow cropland (restoration starting point), 10‐year‐old planted old fields and intact woodland reference sites (restoration target point). We stratified sampling between open areas and patches under trees in planted old fields and reference woodlands to account for inherent biophysical differences. Soils under planted trees recovered to some extent, having reduced soil compaction and higher soil penetration depth in comparison with the fallow cropland. However, soils under trees in planted old fields did not reach woodland reference conditions for these properties. Moreover, recovery was not evident for other soil physical, biogeochemical and biotic components such as soil organic carbon, soil moisture, leaf litter and woody debris decomposition rates. Limited recovery of soil functions may be at least partly explained by time lags associated with slow growth rates of planted trees in dry ecosystems. Our study shows that the legacy of cropping can persist over long timeframes in semi‐arid regions, with modest signs of woodland recovery beginning to emerge 10 years after tree planting.

Analysis of Mangrove Leaf Litter Decomposition Rate in Mangrove Ecosystem of Muara Pagatan, South Kalimantan

Mangroves are the dominant ecosystem in coastal areas and estuaries and one of the most productive ecosystems in the world. Mangroves are an essential component in a complex food chain and have the potential for the life of various marine and terrestrial biotas, microorganisms, and macroorganisms. The decomposition of mangrove leaf litter by fungal bacteria produces nutrient source that is beneficial for fish, shrimps, and crabs. This study discusses the production and decomposition rate of mangrove leaf litter in the mangrove ecosystem of Muara Pagatan, South Kalimantan. With transect and litter trap methods, litter production during the observation ranged from 218.51 - 858.28 g/m2/45day. Of the four types of mangroves found, the highest litter production was found in Rhizophora mucronata mangrove species at 858.28 g/m2/45day, followed by Bruguiera gymnorrhiza species at 268.52 g/m2/45day, and the lowest litter production was Avicennia marina mangrove species at 222.9 g/m2/45day and Sonneratia alba at 218.51 g/m2/45day. The remaining dry weight during observation ranged from 1.06 g - 2.46 g. In sum, the highest litter productivition and decomposition rate was found in Rhizophora species and litter was not completely decomposed after 45 days.

Effects of Acacia invasion on water quality, litterfall, aquatic decomposers, and leaf litter decomposition in streams

Abstract Small streams and their riparian vegetation are closely linked ecosystems. Thus, the invasion of native riparian forests with non‐native species can impact stream ecosystems. We assessed the effects of the invasion of broadleaf deciduous forests by evergreen, nitrogen‐fixing Acacia species on seasonal variation of relevant instream environmental variables, litterfall in the riparian area, aquatic decomposers, and leaf litter decomposition, by comparing three streams flowing through native forests (native streams) and three streams flowing through invaded forests (invaded streams) in central Portugal. Invaded streams flow through forests composed (almost) of monospecific stands of Acacia trees. Litterfall in the riparian area was sampled with fabric traps and sorted into five categories: leaf (including phyllodes), flower, fruit and seed, wood litter, and other materials. Aquatic hyphomycete conidia suspended in water were sampled to assess conidia concentration and community composition. Leaf litter of Quercus robur was enclosed in coarse‐mesh bags and incubated in streams to assess decomposition rates and associated macroinvertebrate density and community composition. Samples from each variable were collected monthly from streams over 1 year. Aquatic hyphomycete conidia concentration was higher in invaded streams in spring/summer when litter inputs, water temperature, and aquatic nutrient concentrations were higher. In contrast, conidia concentration was lower in invaded streams in autumn/winter as they received less native deciduous leaf litter in autumn than native streams. Aquatic hyphomycete community structure changed, and species richness was lower in invaded streams because aquatic nutrient concentrations were higher and leaf litter species richness was lower. Macroinvertebrate and shredder density in decomposing leaf litter did not differ between native and invaded streams, but litter bags may have artificially increased densities by providing high quality food and/or refuges in streams with poor‐quality resources. Nevertheless, macroinvertebrate community structure changed, and family richness was lower in invaded streams. Finally, decomposition rates of Q. robur leaf litter in coarse‐mesh bags were similar between stream types, despite differences in aquatic decomposer communities. Overall, Acacia invasion changed water quality, litterfall seasonality and composition, and aquatic decomposer communities (especially aquatic hyphomycetes). However, Acacia effects on macroinvertebrate density and leaf litter decomposition rates were less pronounced, suggesting that higher trophic levels may be more resilient to invasion than basal levels, or the invasion time/extent in our invaded streams was not strong enough to affect macroinvertebrates and associated processes. Instream invasion effects on aquatic hyphomycete communities were more strongly mediated by changes in litter inputs rather than increases in aquatic nutrient concentrations because they remained oligotrophic in invaded streams. Simplification of riparian and aquatic communities may render them less efficient in coping with additional environmental changes. Acacia effects might be mitigated by the maintenance of a riparian corridor composed of native vegetation. The protection of non‐invaded riparian galleries and restoration of invaded ones could protect and restore stream ecosystems.

Seasonal and long-term changes in litterfall production and litter decomposition in the dominant forest communities of Western Himalaya

Understanding changes in litter fall is paramount for effective management, as it directly impacts ecosystem health, nutrient cycling, and overall biodiversity. It informs strategies for conservation, land use planning, and mitigating ecological disruptions. Therefore, present study investigates the seasonal and long-term changes in litterfall dynamics within the dominant forest communities of Western Himalaya. A total four distinct forest ecosystems, including Sal, (Shorea. robusta) Chir-pine (Pinus roxburghii), Banj-oak (Quercus leucotrichophora), and Mixed-oak (Q. leucotrichophora, Q. floribunda and Q. lanuginosa) forests were selected for the study. The total annual litter production across the forest stands varied from 741.59 to 841.22 g−2, with the highest recorded in the Banj-oak stand (841.22 g−2) and the lowest in the Sal stand (741.59 g−2). Leaf fall reported for the highest proportion of total litterfall (64.88% to 71%) across the forest stands, and peak litterfall was observed during the summer months in all forest sites. The leaf litter decomposition rate of selected species shows significant variation (F5, 10 = 3.41, p < 0.05) between species. Interestingly, litterfall production increased in all forest sites from 1980 to 82 to 2017–19. However, no significant changes were observed in the decomposition rate. The findings reveal significant variations in litterfall dynamics across different forest ecosystems, with leaf fall contributing substantially to total litter production. The observed increase in litterfall production over the studied period highlights the need for continued monitoring and adaptive management strategies to address potential ecological implications. These insights are invaluable for informing conservation efforts, land use planning, and mitigation strategies aimed at preserving ecosystem health, sustaining biodiversity, and ensuring the long-term resilience of Western Himalayan forests in the face of environmental change.

Ecology and methodology of comparing traits and decomposition rates of green leaves versus senesced litter across plant species and types

Abstract Variation in leaf traits is critical for carbon gains and losses during leaf life and drives litter carbon and nutrient losses via decomposition. Accurately quantifying litter decomposition parameters is essential for assessing ecosystem carbon and nutrient dynamics. Leaf litterbags have commonly been employed to measure effects of environmental drivers, decomposers, and plant traits on decomposition rates. There has been much debate regarding the suitability of substituting senesced dead leaves with fresh (green) leaves in litterbags, which has been common practice for mimicking green leaf fall or for practical reasons. Therefore, we tested the null hypothesis that replacement of dead leaves with fresh leaves in litterbag experiments is justified, based on similarities in structural and chemical traits between fresh and dead leaves across plant species and growth forms. We conducted a paired litterbag decomposition experiment with both fresh and dead leaves of 26 common species in subtropical China, in each of five contrasting ecosystems. While fresh leaves generally decomposed faster than dead leaves, this deviation varied among species and growth forms, based on their traits. Overall, there was significant but rather weak correlation between dead leaf decomposition rate k and fresh leaf k, across species and ecosystem types; the deviation between fresh and dead leaf k was larger for fast‐decomposing, mostly herbaceous species. The different decomposition patterns for fresh versus dead leaves were underpinned by key underlying traits integrated in leaf resource economics spectra (LES) for fresh and dead leaves. The dead leaf LES exhibited a greater predictive capability for dead leaf k while the fresh leaf LES had higher explanatory value for the fresh leaf k values. Our findings partly reject the null hypothesis and ask for caution in inferring leaf litter decomposition rates based on green leaf litterbags or traits data. We suggest follow‐up research on substituting senesced roots and stems with fresh ones in decomposition experiments. Synthesis. Human activities and extreme weather events are leading to increasing pulse inputs of fresh plant parts and our study contributes to knowledge on how they contribute to overall decomposition rates besides senesced litter inputs.

Large invertebrate decomposers contribute to faster leaf litter decomposition in Fraxinus excelsior-dominated habitats: Implications of ash dieback

Leaf litter decomposition is a major component of nutrient cycling which depends on the quality and quantity of the leaf material. Ash trees (Fraxinus excelsior, decay time ∼ 0.4 years) are declining throughout Europe due to a fungal pathogen (Hymenoscyphus fraxineus), which is likely to alter biochemical cycling across the continent. The ecological impact of losing species with fast decomposing leaves is not well quantified. In this study we examine how decomposition of three leaf species with varying decomposition rates including ash, sycamore (Acer pseudoplatanus, decay time ∼ 1.4 years), and beech (Fagus sylvatica, decay time ∼ 6.8 years) differ in habitats with and without ash as the dominant overstorey species. Ten plots (40 m × 40 m) were set up in five locations representing ash dominated and non-ash dominated habitats. In each plot mesh bags (30 cm × 30 cm, 0.5 mm aperture) with a single leaf species (5 g) were used to include (large holes added) and exclude macrofauna invertebrates (with a focus on decomposer organisms such as earthworms, millipedes, and woodlice). The mesh bags were installed in October 2020 and retrieved without replacement at exponential intervals after 6, 12, 24 and 48 weeks. Total leaf mass loss was highest in the ash dominated habitat (ash dominated: 88.5%, non-ash dominated: 66.5%) where macrofauna were the main contributor (macrofauna: 96%, microorganisms/mesofauna: 4%). The difference between macrofauna vs microorganisms and mesofauna was less pronounced in the non-ash dominated habitat (macrofauna: 68%, microorganisms/mesofauna: 31%). Our results suggest that if ash dominated habitats are replaced by species such as sycamore, beech, and oak, the role of macrofauna decomposers will be reduced and leaf litter decomposition rates will decrease by 25%. These results provide important insights for future ash dieback management decisions.

Long-Term Nitrogen Addition Accelerates Litter Decomposition in a Larix gmelinii Forest

Elevated atmospheric N deposition has the potential to alter litter decomposition patterns, influencing nutrient cycling and soil fertility in boreal forest ecosystems. In order to study the response mechanism of litter decomposition in Larix gmelinii forest to N deposition, we established four N addition treatments (0, 25, 50, 75 kg N ha−1 yr−1) in the Greater Khingan Mountains region. The results showed that (1) both needle and mixed leaf litter (Betula platyphylla and Larix gmelinii) exhibited distinct decomposition stages, with N addition accelerating decomposition for both litter types. The decomposition of high-quality (low C/N ratio) mixed leaf litter was faster than that of low-quality needle litter. (2) Mixed leaf litter increased the decomposition coefficients of litter with lower nutrients. (3) All N addition treatments promoted the decomposition of needle litter, while the decomposition rate of mixed leaf litter decreased under high-N treatment. (4) N addition inhibited the release of N and P in needle litter and promoted the release of N in mixed leaf litter, while high-N treatment had no positive effect on the release of C and P in mixed leaf litter. Our research findings suggest that limited nutrients in litter may be a key driving factor in regulating litter decomposition and emphasize the promoting effect of litter mixing and nitrogen addition on litter decomposition.

Multi-dimensional temperature sensitivity of protected tropical mountain rain forests

IntroductionTropical mountain rain forests (TMRF, natural forests at &amp;gt; 300 m asl) are globally important for biodiversity and ecosystem services and are believed to be highly vulnerable to climate change. But there are no specific approaches for rigorous assessment of their vulnerability at the landscape and local scales necessary for management for adaptation. We address the challenge of evaluating the ecological sensitivity to temperature of TMRF, applying a multidimensional approach in protected areas over a 440–2,950 m asl altitudinal gradient in Costa Rica, synthesizing results of a long-term research programme (2012-present). We evaluate the sensitivity to the current spatial temperature gradient of eleven ecosystem properties in three categories: forest composition and diversity, thermal characteristics of forest stands and forest structure and dynamics.MethodsData are from 29 to 32 plots of 50 m x 50 m (0.25 ha) distributed over the gradient, in which all trees, palms and tree ferns ≥ 10 dbh are identified to species and measured for recruitment, growth and mortality. An experimental study of leaf litter decomposition rates was carried out in twelve plots. Current and future (SSP 585, 2070) values of mean annual temperatures MAT were obtained from online climate surfaces. Thermal characteristics of forest stands were determined using MATs of species occurrences in GBIF and include a new index, the Community Thermal Capital Index (CTCI), calculated as CTI-MAT.ResultsWe classified degrees of sensitivity to temperature as very weak, weak, moderate or substantial. All eleven ecosystem properties are substantially sensitive, so changes in their values are expected under rising temperatures. Species density, the community temperature index CTI, tree recruitment and mortality rates and leaf litter decomposition rates are positively related to temperature, while the community weighted mean thermal niche breadth, the CTCI, net basal area increments, stand basal area and carbon in aboveground biomass are negatively related. Results point to zones of vulnerability in the protected areas.DiscussionIn montane forests, positive values of the CTCI–climate credit– robust basal area growth and very low mortality and leaf litter decomposition rates suggest healthy ecosystems and no risk of mountaintop extinction. Lowland forests may be vulnerable to degradation and biotic attrition, showing current basal area loss, high mortality and climate debts. National and local actors are participating in a process of adoption of the sensitivity analysis and recommendations regarding zones of vulnerability.

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.

Decomposability of leaf and wood litter are not correlated across species: effects of litter traits on decomposition in field and laboratory conditions

Changes in tree species composition have important effects on the overall rate of litter decomposition at a community level because litter decomposability varies among species and between leaf and wood litter. To understand how changes in tree species composition affect litter dynamics and carbon sequestration at the ecosystem level, it is important to clarify interspecific variations in leaf and wood litter decomposability, and the traits driving the variation. Using field data, field experiments, and laboratory experiments, we explored rates of leaf and wood litter decomposition and their relationships to traits of ten deciduous hardwood species in a temperate forest in Japan. Rates of leaf and wood litter decomposition at the community level were also estimated by considering species‐specific litter inputs and decomposition rates. Rates of leaf and wood litter decomposition were not correlated under either field or controlled laboratory conditions. This is probably because the traits that affect decomposition rate differ between leaf and wood litter. Interspecific variation in litter decomposability of leaves and wood was generally consistent between field conditions and laboratory experiments using a single fungus, suggesting that the decomposing fungi set the species‐specific decomposition rates. Moreover, the leaf and wood traits that affected decomposition by their specific fungi were different. The aboveground input of wood litter was less than half that of leaf litter, but its half‐life was &gt; 3 times longer, suggesting that wood and leaves make similar contributions to litter accumulation. Focusing on either leaf or wood litter alone may produce misleading estimates of how species composition changes affect litter dynamics at the community level. Our results provide insight into predicting the response of carbon dynamics to future climate change.

Effects of copper and cadmium on stream leaf decomposition: evidence from a microcosm study.

We seek to understand how copper and cadmium act on leaf litter decomposition by their effects on microbial conditioning and litter fragmentation by invertebrates. In this study, we evaluated, in an integrated manner, different biological elements responsible for functioning of streams. Thus, we performed a microcosm assay with different concentrations for the two metals and their combination, evaluating their effects on fungi sporulation rate, consumption rate by shredders, and, consequently, the leaf litter decomposition rates. Sporulation rates were affected by all copper concentrations tested 10 × = 16µg L-1 and 25 × = 40µg L-1) but significantly reduced only at the highest concentration of cadmium (25 × = 22.5µg L-1). Increased copper and cadmium concentrations reduced the consumption of leaf litter by Phylloicus at 60%. The concentrations (10 × and 25 ×) of both metals resulted in a reduction in decomposition rates. When combined, copper and cadmium negatively affected microbial conditioning, consumption by shredders, and leaf litter decomposition. Increases in concentrations of copper and cadmium directly affected organic matter decomposition in aquatic environments. Thus, the presence of a high concentration of heavy metals in aquatic environments alters the functioning of ecosystems. As trace-elements occur in a combined manner in environments, our results show that the combined effects of different metals potentiate the negative effects on ecosystem processes.