Leaf Litter Decomposition Rates Research Articles

Functional traits, growth patterns, and litter dynamics of invasive alien and co-occurring native shrub species of chir pine forest in the central Himalaya, India

Across the continents, plant invasion is identified as one of the main threats to ecosystem functioning and stability. The main objective of this research was to evaluate the differences in the functional traits between invasive alien (Ageratina adenophora (Spreng.) and Lantana camara L.) and native (Berberis asiatica Roxb. Ex DC., Pyracantha crenulata (D. Don.) M. Roemer and Rubus ellipticus Sm.) shrub species of chir pine (Pinus roxburghii Sarg.) forest in the central Himalaya. Three 0.5 hectare chir pine forest stands were selected and individuals of similar diameter were tagged for comparative studies of leaf traits, growth pattern, and biomass accumulation in structural organs of each invasive alien and native species. Our one-way ANOVA and Tukey’s post hoc test results showed that both the invasive alien species have significantly (p < 0.05) higher SLA, LWC, total chlorophyll content, foliar nutrient (N and P), RGR, LMR, SMR, nutrient uptake, and nutrient use efficiencies than native species. Leaf litter decomposition rate and nutrient release were also significantly (p < 0.05) higher in both the invasive alien species. Native species, R. ellipticus, shared some of the traits, such as leaf area, chlorophyll content, RGR, LAR, LMR, and nutrient uptake efficiency with invasive alien species. The majority of traits differed among invasive alien and native species, implying that the success of invasive alien species is best described by being functionally distinct from native species. These findings indicate that invasive alien species had advanced functional traits which may be playing an important role in a rapid spread in the central Himalaya.

Leaf litter dynamics in Western Black Sea mountainous forest ecosystems

This study aimed to estimate leaf litter decomposition rates in eastern beech (Fagus orientalis Lipsky) and sweet chestnut (Castanea sativa Mill.) mixed stands in Akçakoca in the province of Düzce, located in the Western Black Sea region of Turkey. The sampling areas represent four different elevations and two aspects at each elevation. Amounts of annual beech and chestnut litterfall were estimated at 5.19 and 4.61 Mg·ha−1, respectively. Litter decomposition was examined over five time periods (0.25, 0.50, 1.25, 2.25, and 4.25 years) by using the litterbag method. The mass of remaining beech leaf litter was found to be 1.1, 1.2, 1.2, 1.4, and 1.3 times greater than the mass of chestnut leaf litter, respectively. However, estimated values for the decomposition rate constant (k) of chestnut for all time periods were found to be approximately 1.5 times greater than those of beech leaf litter. Litter in beech stands decomposed more rapidly at higher elevations during the first year but at lower elevations during the second year, likely due to increased temperature and precipitation for the corresponding years. Leaf litter in chestnut stands decomposed more rapidly at lower elevations in the second and fourth years, reflecting higher precipitation for those years.

A Comparative Study of Manipulative and Natural Temperature Increases in Controlling Wetland Plant Litter Decomposition

Manipulative experiments and space-for-time substitutions are two main approaches used to infer the impacts of future climate change on ecological processes, such as litter decomposition. The potential limitations of these approaches are well-recognized. Here, we address the congruence between these two approaches by comparing decomposition rates of leaf litter from four wetland plant species in response to (i) in-situ experimental warming (manipulative warming), and (ii) broad-scale spatial gradients (natural warming) over one-year observation of 2019. Manipulative warming was achieved by using open-top chambers (OTCs), and natural warming was followed along an altitudinal gradient from a high altitude site to a low site. Litter decomposition rates increased with temperature increasing in both OTC- and gradient-based approaches. However, litter decomposed faster along with the decreasing altitude than predicted by the manipulated rise in temperature, especially for those plants being resistant to decompose. For the gradient-based approach, the interaction effects between temperature and precipitation explained up to 44.1% of litter decomposition dynamics and served as a key to differentiate these two approaches. These results support the view that space-for-time substitution over broad-scale spatial gradients may magnify the responses of certain ecological processes to further climate warming. Our work is the first study to compare the characteristics of decomposition of wetland plant litter types in OTC- and natural gradient-based warming experiments.

Field decomposition of Bt-506 maize leaves and its effect on collembola in the black soil region of Northeast China

The litters from Bt maize are always plowed into the soil after harvest. To clarify whether the decomposition rate of Bt litters and the nontarget soil fauna in the litters are influenced by Bt protein or the other organic matter, the leaf pieces of Bt-506, its near isoline Zheng 58 and a local type Zhengdan 958 were put into litterbags and buried into the field in Northeast China. Then, the Bt protein content of Bt-506 litters, the nonstructural carbohydrate and total nitrogen contents, and decomposition rates of all leaf litters and the collembolan communities in these litters were investigated after a period of buried time. There was 43.5 ng/g Bt protein remained in Bt-506 litters at the end of the experiment, when the Bt-506 litters had been kept in field for decomposition for 7 months. Except for Bt protein, none of the other investigated indexes were significantly different between Bt-506 and Zheng 58 at any sampling time. However, when compared with Zhengdan 958, the leaf litters of Bt-506 and Zheng 58 contained less nonstructural carbohydrate but more total nitrogen, and had lower decomposition rate, lower collembolan abundance and Shannon-Wiener index at some sampling times. Correlation analysis showed that the leaf litter decomposition rate and the collembolan abundance in litters were significantly correlated with the nonstructural carbohydrate content and the total nitrogen content of maize litters on May 20 (after buried in field for 6 months), and neither collembolan abundance nor leaf litter decomposition rate was correlated with maize type at any sampling time. In sum, Bt protein did not affect the decomposition rate of leaf litters and the collembolan community in litters; the differences of leaf litter decomposition rate and the collembolan community in litters between Bt-506, Zheng 58 and Zhengdan 958 were probably resulted from the different contents of nonstructural carbohydrate and total nitrogen in the leaf litters.

The decomposition rates of leaf litter and fine root and their temperature sensitivities are influenced differently by biotic factors

Determining the temperature sensitivities of the decomposition rates of leaf litter and fine root is important for predicting the impact of climate warming on above- and belowground carbon (C) cycles in forest ecosystems. However, the responses of leaf and root decomposition rates to temperature have rarely been examined together. Here, we present the results of paired leaf litter and fine root decomposition experiments at four forest sites spanning 32° latitude in eastern China. The mean annual soil temperature explained the variances of the decomposition rates of the leaf litter (kLeaf, R2 = 0.95) and fine root (kFine root, R2 = 0.86) across the different biomes well and exerted a positive effect on the kLeaf: kFine root ratio. As a result, the sensitivity of the decomposition rate to temperature was significantly higher in the leaf litter (Q10 = 2.17 ± 0.07) than in the fine root (Q10 = 1.40 ± 0.06). The results of structural equation models indicated that the initial C:nitrogen (C:N) ratio exhibited negative effects, and phosphorus (P) cycling related enzymes activity exhibited positive effects on the kFine root when the effects of temperature were controlled. Even when the variables of these biotic factors were added, the soil temperature still exerted a dominant effect on the kLeaf. Our results suggest that temperature directly influences the kLeaf but indirectly affects the kFine root through litter quality and soil decomposers.

Leaf litter decomposition in tropical freshwater swamp forests is slower in swamp than non‐swamp conditions

AbstractDecomposition is a key ecosystem function, and the rate of decomposition in forests affects their carbon storage potentials. Processes and factors determining leaf litter decomposition rates in dry‐land and temperate forests are well understood, but these are generally poorly studied in tropical wetland forests, especially freshwater swamp forests (FSF). The home‐field advantage (HFA) hypothesis predicts that soil microbes specialize in decomposing leaf litter produced by the tree species in their immediate vicinity. However, empirical support for the HFA is equivocal, and the HFA has never been tested in the highly heterogeneous and biodiverse ecosystems of tropical FSFs. We collected leaf litter from swamp and non‐swamp tree species in a tropical FSF in Singapore and monitored the decomposition rates of these in swamp and non‐swamp plots for a period of eight months. Leaf litter decomposed 3.7 times more slowly in swamp plots. Leaf litter from swamp tree species were significantly poorer in quality (higher C:N ratio) than those of non‐swamp FSF tree species, but this had only a weak effect on decomposition rates. There was also only weak evidence for the HFA and only in non‐swamp conditions. Our results show that while the leaf litter of tropical FSF swamp and non‐swamp tree species differ significantly in chemical traits, litter decomposition rate is ultimately determined by local abiotic conditions, such as hydrology. Additionally, the high FSF tree diversity may prevent decomposer communities from specializing on any group of leaf litter types and thus limit the extent of HFA observed in such heterogeneous forests.

Filter-feeders have differential bottom-up impacts on green and brown food webs.

Nutrient recycling by consumers can strongly impact nutrient availability for autotrophic and heterotrophic microbes, thus impacting functions such as primary production and decomposition. Filter-feeding freshwater mussels form dense, multispecies assemblages in aquatic ecosystems and have been shown to play a critical role in nutrient cycling. Mussel excretion can enhance benthic primary production and influence algal species composition. However, the role of mussels in brown or detritus-based food webs and species-specific differences has received considerably less attention. Here, using mesocosm experiments, we assessed how three species of freshwater mussels that occupy three different phylogenetic tribes influenced benthic algal accrual, ecosystem metabolism, cotton strip decomposition, leaf litter (Acer saccharum) decomposition, and litter-associated fungal biomass measured as ergosterol. Additionally, we measured mussel excretion and biodeposition rates and assessed the stoichiometry (C:N, C:P, and N:P) of the benthic algae, cotton strips, and leaf litter. In comparison to controls without mussels, generally, mussel treatments had higher benthic algal biomass composed of more diatoms, higher gross primary productivity and net ecosystem production rates, and higher cotton strip tensile strength loss, but there was not a difference in ecosystem respiration rates, leaf litter decomposition rates, or fungal biomass. Benthic algae had lower C:N and higher N:P in mussel treatment tanks and cotton strip C:N was lower in mesocosms with mussels. Our results suggest that nutrient regeneration by mussels most strongly regulates green food webs, with some impacts to brown food webs, suggesting that consumers have interactive effects on microbial functioning in freshwaters.

氮磷添加对杉木根叶分解残余物微生物群落结构及酶活性的影响

为揭示根、叶分解残余物对生态系统养分循环相关过程的影响，研究了分解第3年杉木根残余物（凋_R）和叶残余物（凋_L）中的微生物群落结构（环丙基脂肪酸/前体结构，Cy/pre；单不饱和脂肪酸/饱和脂肪酸，Mono/sat；真菌/细菌，F/B；革兰氏阳性菌/革兰氏阴性菌，G⁺/G^-）、酶活性（β-葡萄糖苷酶，βG；β-N-乙酰氨基葡糖苷酶，NAG；酸性磷酸酶，AP）、化学元素含量及计量比对氮磷添加的响应。结果表明：（1）与凋_R相比，凋_L中的Cy/pre、F/B、G⁺/G^-低，Mono/sat高。氮磷添加对分解残余物微生物群落结构影响不显著。（2）与凋_R相比，凋_L中的βG和NAG活性高、βG/AP大。氮磷添加抑制了AP活性，提高了βG/NAG及βG/AP。且氮磷添加对凋_R的AP活性抑制作用更强，对凋_L的βG/NAG提升幅度更大。（3）分解残余物中的Mono/sat、G+/G、F/B分别与锰含量、磷/钙、氮含量正相关；AP、βG/NAG分别与氮/磷、磷/铁正相关；βG/AP、NAG、βG分别与氮/锰、磷/镁、氮/钙负相关。表明根、叶分解残余物仍可对生态系统养分循环相关过程产生不同影响，考虑分解残余物类型可提高全球变化背景下生态系统养分循环过程预报精度。;Root and leaf litters are two important litter sources in ecosystems, providing carbon sources and nutrients for microorganisms. The decompositions of root and leaf litters are highly sensitive to the environmental availability of nutrients. The simultaneous deposition of nitrogen and phosphorus is one of the most critical challenges in ecosystems worldwide. Changes of nitrogen and phosphorus inputs can affect both the decomposition rates of root and leaf litter and other responses of the ecosystem. The long-term patterns of mass loss during leaf and root litter decomposition are well documented, but the responses of microbial community structure and enzyme activity in root and leaf debris to the simultaneous deposition of exogenous nitrogen and phosphorus are not known. Understanding the influence of simultaneous inputs of exogenous nitrogen and phosphorus on the microbial community structure and enzyme activity in root and leaf debris can help us to precisely predict shifts in ecosystem processes in nitrogen and phosphorus deposition enriched regions. We investigated the responses of microbial community structure (cyclopropyl fatty acids/precursor structure, Cy/pre; monounsaturated fatty acids/saturated fatty acid, Mono/sat; fungus/bacteria, F/B; Gram-positive bacteria/Gram-negative bacteria, G⁺/G^-), enzyme activity (glucosidase, βG; β-N-Acetylglucosaminidase, NAG; acid phosphatase, AP), chemical element content and stoichiometry in root and leaf debris (3 years after decomposition) of Cunninghamia lanceolata to nitrogen and phosphorus additions. Results showed that Cy/pre, F/B, G⁺/G^- were lower and Mono/sat was higher in the leaf debris than those in the root debris. However, nitrogen and phosphorus additions had no significant effect on the microbial community structure of the debris. The leaf debris had higher βG and NAG activity and βG/AP compared with the root debris. Nitrogen and phosphorus additions decreased the AP activity and increased βG/NAG and βG/AP. Moreover, nitrogen and phosphorus additions resulted in a greater decrease in root debris' AP activity but a more significant increase in βG/NAG of leaf debris. Multiple stepwise regression showed that Mono/sat, G⁺/G^- and F/B positively correlated with manganese content, phosphorus/calcium, and nitrogen content, respectively. AP and βG/NAG were positively correlated with nitrogen/phosphorus and phosphorus/iron, respectively; and βG/AP, NAG, and βG were negatively correlated with nitrogen/manganese, phosphorus/magnesium, and nitrogen/calcium, respectively. Our results found that the effects of nitrogen and phosphorus additions on microbial community structure and enzyme activity were generally inconsistent between root and leaf debris, thereby underlining that leaf and root litters need to be considered separately when evaluating the response of decomposers to their substrates in the context of global change to improve the prediction accuracy of ecosystem nutrient cycling processes.

Linking plant and animal functional diversity with an experimental community restoration in a Hawaiian lowland wet forest

Testing how plant restoration influences animal taxonomic and functional diversity can shift restoration projects beyond mainly plant community considerations. We incorporated multi-trophic interactions into restoration by describing an ongoing functional trait-based restoration experiment in Hawaiian lowland tropical wet forest (Liko Nā Pilina Experiment), where litter arthropods are examined from a functional perspective thereby linking plants and higher trophic levels. We hypothesized that (1) communities with greater plant functional trait diversity would have cascading effects through food webs, increasing animal diversity and network complexity, and (2) increases in animal species and network complexity would be stronger for restoration efforts in plant communities with more complementary functional traits than those with more redundant traits. We examined experimental treatments of planted communities with the same species richness but with different plant functional trait profiles based on (1) rates of expected carbon turnover (slow or moderate), and (2) the similarity of their functional trait measurements (redundant or complementary), as determined by functional dispersion calculations. Initial data on arthropod communities and leaf litter decomposition rates revealed linkages between plant functional traits and arthropod community diversity. Overall, we argue that a more comprehensive evaluation of restoration accounts for both functional diversity and the multi-trophic nature of animal and plant communities. Developing restoration projects based on plant functional traits that influence both plant and invertebrate species provides a new paradigm, and the incorporation of both native and non-native (but non-invasive) plants shows promise in restoring ecosystem function in disturbed lowland tropical forests.

Estimation of Biomass, Carbon Stocks and Leaf Litter Decomposition Rate in Teak Tectona grandis Linn Plantations in City Forest of Hasanuddin University, Makassar

Teak Tectona grandis Linn is still used as the main product in the form of wood, while other products, especially environmental services have not received much attention. This study analyzed biomass, carbon stocks and decomposition rate of leaf litter in teak plantations in city forest of Hasanuddin University, Makassar. The individual biomass of teak plants is calculated using the allometric equation Y = 0.11 × ρ × D2.62. Carbon stocks were analyzed using a formulation C = 0.47 × B. The leaf litter decomposition rate is expressed as the ratio of the remaining litter dry weight, with the formulation X = (A − B)/A. The number of teak plants in 5 sample plots were 239 trees with an average stem diameter of 20.6 cm and an average height of 9.02 m. Total biomass in 5 sample plots was 51,712.61 g. Carbon stocks in 5 sample plots was 24,304.92 g. Decomposition rate average of leaf litter of 24.4 g during 60 days incubation. The existence of teak plantations is able to reduce CO2 in the atmosphere by as much as 89,199.06 g CO2 and resulting in a decomposition rate of teak leaf litter 0.4 g per day.

Laju Dekomposisi Serasah Daun Mangrove Bruguiera gymnorrhiza dan Sonneratia alba di Kawasan Hutan Mangrove Pulau Penyu, Tanjung Benoa, Bali

Mangroves are plants that play an important role in maintaining the fertility of mangrove ecosystems by contributing organic material derived from leaf litter. The rate decomposition of leaf litter is a destruction process by dead organisms into smaller particles. The decomposition process of mangrove leaf is affected by lignin and wax in nitrogen supply, environmental conditions, abundance of organisms, and air temperature. This research aims to determine the decomposition rate of leaf litter and percentage decomposition of Bruguiera gymnorrhiza and Sonneratia alba in mangrove forest area in Penyu Island, Tanjung Benoa, Bali. This research was conducted from February to April 2017. The method in this research used litter trap method. The location of the stations was based on the distance of the mangrove trees to the sea. Litter traps were placed on the six (6) stations. During the 60 days of decomposition process, Sonneratia alba leaf was decomposed faster than Bruguiera gymnorrhiza. The highest decomposition rate of Sonneratia alba leaf litter found at station 1 (1.7 g/day) with 99.9% decomposed, and the lowest at station 2 (1.38 g/day) with 99.64% decomposed. The highest decomposition rate of Bruguiera gymnorrhiza leaf litter found at station 1 (1.52 g/day) with 98.88% decomposed, and the lowest at station 2 (0.99 g/day) with 84.66% decomposed.

Effects of canopy nitrogen addition on soil fauna and litter decomposition rate in a temperate forest and a subtropical forest

Traditionally, experiments testing the impacts of nitrogen (N) deposition on ecosystem processes have been conducted by adding N directly to forest floors, yet, in reality, atmospheric N passes through the canopy layer before it reaches the forest floor. Furthermore, we know little about how N-deposition mediated changes in soil fauna communities affect litter decomposition. Here, we use a novel experiment to contrast canopy addition of N (CAN) to understory addition of N (UAN) in a subtropical forest and a temperate forest to investigate the impact of N-deposition approaches and N-concentrations on soil fauna and leaf litter decomposition rate. We found that CAN increased the soil fauna diversity and accelerated litter decomposition whereas UAN did not significantly affect soil fauna or litter decomposition. In addition, N-deposition concentration significantly influenced soil fauna density, H′ diversity, and species richness at the subtropical forest, but only affected H′ diversity of soil fauna at the temperate forest. The high N-deposition concentration treatment in the subtropical forest and low N-deposition concentration treatment in our temperate forest had significantly higher decomposition rates compared with the control (no N) treatment. We assert that addition of N through the canopy is a more realistic approach for simulating the actual processes of atmospheric N-deposition in forests. Future experiments using CAN methods will provide an improved understanding of the effect of N-deposition on soil fauna-decomposition interactions and inform reliable predictions of the consequences of global change on soil ecosystems.

Nutrient Release Dynamics Associated with Native and Invasive Leaf Litter Decomposition: A Mesocosm Experiment

Leaf litter contributes to the functioning of aquatic ecosystems through allochthonous inputs of carbon, nitrogen, and other elements. Here, we examine leaf litter nutrient inputs and decomposition associated with four plant species using a mesocosm approach. Native sycamore fig Ficus sycomorus L., and silver cluster–leaf Terminalia sericea Burch. ex DC. decomposition dynamics were compared to invasive tickberry Lantana camara L. and guava Psidium guajava L., whereby phosphate, nitrate, nitrite, silicate, and ammonium releases were quantified over time. Leaf inputs significantly reduced pH, with reductions most marked by invasive L. camara. Conductivity was heightened by all leaf input treatments, except native T. sericea. Leaf inputs significantly affected all nutrient levels monitored in the water over time, except for silicate. In particular, leaf litter from invasive L. camara drove significantly increased nutrient concentrations compared to other native plant species, whilst effects of invasive P. guajava were less statistically clear. The end weights of the leaf litter demonstrated decomposition differences among the species types, following a decreasing order of P. guajava &gt; T. sericea &gt; F. sycomorus &gt; L. camara, further suggesting high organic inputs from invasive L. camara. The study results highlight that differential leaf litter decomposition rates of four plant species can play a significant role in nutrient release, in turn altering aquatic ecosystem productivity. However, these effects likely depend on species-specific differences, rather than between invasive–native species generally. Shifting terrestrial plant communities may alter aquatic community composition, but specific effects are likely associated with leaf traits.

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

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

Cadmium pollution alters earthworm activity and thus leaf-litter decomposition and soil properties

It has been reported that heavy metal contamination can affect litter decomposition and soil properties through its impact on microbial communities. However, it is still unclear whether the expected changes in earthworm activities in responses to heavy metal contamination could affect these properties. Therefore, we quantified earthworm (Eisenia fetida) responses in survival rate to lethal cadmium (Cd) concentrations (0, 50, 100, 150, 200, 250, and 300 mg L−1), and in burrowing ability, physiological characteristics, and feeding rate (on poplar leaf litter) to sub-lethal Cd concentrations (0, 15, 30, and 45 mg kg−1). Finally, sub-lethal influences of Cd on the decomposition rate of poplar leaf litter and on soil properties were investigated in the present of E. fetida. The 12-, 24-, 36-, and 48-h LC50 of Cd for E. fetida were 276.0, 208.6, 192.6, 179.8 mg L−1, respectively. With increasing Cd concentration, malondialdehyde was stimulated, superoxide dismutase first increased and then decreased, while feeding rate, total borrowing length, and maximum burrowing depth consistently decreased. Consequently, leaf-litter decomposition rate and soil nutrient concentrations generally decreased with increasing Cd concentration. Our results indicate that, by affecting earthworm activities, Cd inhibited leaf-litter decomposition and led to the degradation of soil fertility. This study highlights the importance of earthworms in mediating soil functions under heavy metal stress.

Effect of nitrogen and phosphorus addition on litter decomposition and nutrients release in a tropical forest

Through the nutrient fertilization experiment, we aimed to understand how litter decomposition and nutrient release response to the elevated soil N and P availability. A factorial fertilization experiment was conducted in a tropical forest in South China. Leaf litters of five species (Acacia auriculaeformis, Syzygium levinei, Carallia brachiate, Schefflera octophylla, Aphanamixis polystachya) and their mixed sample were put into litter bags in plots fertilized with N, P, or N and P together and collected every three months during the 18-months decomposition. Mass loss of leaf litters and nutrients content were measured. N addition decreased decomposition rates by 15–40%, and the magnitude was species-specific, while P addition had no significant influence on the litter decomposition of all species. Decomposition rate of leaf litter were lower in species with higher C/P ratios and cellulose content. All types of litters served as a net N source during the decomposition. The amounts of mineral elements released during the decomposition followed the order: K > Mg > Ca, and N addition accelerated the Ca and Mg release from litters. The result suggests that future high N deposition can reduce the tropical forest litter decomposition rate but enhance the mineral nutrients release, which may contribute to higher soil C sequestration, while soil P availability does not influence the litter decomposition.

Evaluating community effects of a Keystone Ant, Azteca sericeasur, on Inga micheliana leaf litter decomposition in a shaded coffee agro‐ecosystem

AbstractOur research examined the effect of Azteca sericeasur, a keystone arboreal ant, on the decomposition of leaf litter of the shade tree, Inga micheliana, in coffee agro‐ecosystems. This interaction is important in understanding spatial heterogeneity in decomposition. We hypothesized that A. sericeasur could affect leaf litter decomposition by excluding other ants, which could release decomposers, like collembolans, from predation pressure. Determining the relative strengths of these interactions can illuminate the importance of A. sericeasur in decomposition and nutrient cycling processes. We assessed the ant and arthropod communities surrounding 10 pairs of trees, where each pair included one shade tree with an established A. sericeasur nest. Tuna baits were used in conjunction with pitfall traps to assess the ant and arthropod community, and litterbags with I. micheliana leaf litter were used to assess rates of decomposition. The species richness of ants did not change in proximity to A. sericeasur nests, though the ant communities were distinct. Abundance of Collembola and community composition of other invertebrates did not change in the presence of A. sericeasur nests, and there were no differences in leaf litter decomposition rates. This contradicts past studies that suggest A. sericeasur reduces ant species richness in its territory. We suggest that other ants may avoid A. sericeasur by moving within and beneath the leaf litter. Our results indicate that there is no net effect of A. sericeasur on leaf litter decomposition.

Amynthas spp. impacts on seedlings and forest soils are tree species-dependent

Asian jumping worms (Amynthas spp.) are recent invaders of Upper Midwest forests. Research has highlighted the impacts of Amynthas earthworms on soil biogeochemistry and structure, and field observations suggest that Amynthas spp. decrease litter horizon depth and alter plant communities. However, the extent to which Amynthas spp. effects vary among forest types and with worm density and the mechanisms driving these effects are unknown. We conducted a 3-month tree seedling study to evaluate the effects of Amynthas spp. on tree seedling growth and a mesocosm field experiment to evaluate Amynthas spp. effects on soil carbon and nutrient cycling, soil structure, and leaf litter decomposition rates across forest types. In the seedling study, Amynthas spp. enhanced the growth of sugar maple and European buckthorn seedlings and decreased the growth of white oak seedlings. These effects were due to Amynthas spp.-induced changes in soil properties. In the mesocosm study, as Amynthas spp. density increased, carbon mineralization and carbon, nitrogen, and phosphorus availability increased in white oak forest soils and decreased in sugar maple forest soils, while decomposition rates of European buckthorn litter increased as Amynthas spp. density increased. Amynthas spp. altered soil structure similarly across all forest soil types. Taken together, our results suggest that Amynthas spp. have the potential to alter forest ecosystem dynamics via feedbacks among tree species, seedlings, and soil biogeochemistry. However, Amynthas spp. effects on tree seedlings and forest soils are largely context-dependent, and the direction and magnitude of these effects are mediated by tree species.

Soil Microbial Community and Litter Quality Controls on Decomposition Across a Tropical Forest Disturbance Gradient

Industrial logging and agricultural expansion are driving rapid transformations of tropical ecosystems, modifying patterns in above-ground plant and below-ground microbial communities. However, the extent to which these changes in biodiversity drive modifications of ecosystem process rates such as leaf litter decomposition is poorly understood. To determine the relative effects of changes to the chemical quality of litter and shifts in microbial decomposers on leaf litter decomposition rates, we performed a controlled, reciprocal transplant, litter decomposition experiment across a tropical land-use disturbance gradient. Litter mixtures and soils were collected from old growth forest, moderately logged forest, heavily logged forest, and oil palm plantation in Sabah, Malaysia, and combined in a fully crossed, factorial microcosm experiment maintained under controlled environmental conditions. We found that whilst litter quality was the most important predictor of litter mass loss, soil origin was also significant, explaining between 5.17 and 15.43% of total variation. Microbial decomposer communities from old growth forest had greater functional breadth relative to those from logged forests and oil palm plantation as all litter types decomposed faster when combined with old growth soil. The most chemically recalcitrant litter (lowest N, highest lignin, lignin:N, and C:N ratio) from moderate logged forest decomposed faster when combined with its “home” soil (Home-Field Advantage) whilst the most labile litter from oil palm decomposed slowest when combined with its “home” soil. This was correlated with lower total soil microbial biomass. Taken together, these findings demonstrate that whilst litter quality regulated rates of litter decomposition across the disturbance gradient, soil microbial decomposer communities were functionally dissimilar between land uses and explained a significant proportion of variation. The impact of disturbance on soil, including microbial community structure, should be considered alongside changes to plant communities when assessing effects on crucial ecosystem processes such as decomposition.

Who gives a flux? Synchronous flowering ofCoffea arabicaaccelerates leaf litter decomposition

AbstractCoffee (Coffea arabica) flowers synchronously and flowers are only open for a few days before senescing. Flower petals often decompose easily, containing higher concentrations of nutrients relative to other plant tissues. Thus, a pulse of petals into the detrital pool could be beneficial for the decomposer community and accelerate decomposition processes. Our research assessed the magnitude of the pulse of petals within a shaded coffee farm, and the impact of petals on the litter arthropod community and on the rate of leaf litter decomposition. Three plots of 12 coffee plants were monitored throughout the flowering period to estimate the magnitude of the bloom. Pitfall traps were used to assess the litter arthropod community before and after flowering. Finally, litterbags withC. arabicaleaves alone andC. arabicaleaves with flower petals were used to compare the effect of petals on decomposition rates. The average number of flowers open per plant at the peak of the bloom was 792 flowers. When scaling to obtain an estimate per hectare in a year, our results indicate flower petals could contribute 26.27 kg of nitrogen, 2.03 kg of phosphorus, and 26.7 kg of potassium. The leaf litter community did not change during our sampling, suggesting that any community effects may be acting on a longer time scale or smaller spatial scale. Leaf litter decomposed nearly three times as quickly in litterbags that included flower petals, relative to litterbags with onlyC. arabicaleaf litter in the first month and twice as fast in the second month. The rate of decomposition with petals exceeded the rate of decomposition without petals and was highest after one month, though the benefit continued after two months. Our results demonstrate that the presence of flower petals can accelerate short‐term decomposition processes.