Litter Mass Loss Research Articles

Teatime in the Serengeti: macrodetritivores sustain recalcitrant plant litter decomposition across human-modified tropical savannahs

Background and aimsIntensification of savannah land-use is predicted to negatively influence soil biodiversity and functioning such as litter decomposition by detritivores. Loss of macrodetritivores, particularly termites, may be problematic in drier savannahs due to the capacity of macrodetritivores to sustain litter decomposition. Here we investigate how human land-use and spatiotemporal rainfall influence the contribution of macrodetritivores to plant litter decomposition.MethodsWe measured decomposition using globally standardized litter: labile green and recalcitrant rooibos tea litter. The contribution of macrodetritivores to litter decomposition was determined through exclusion using meshed litterbags. Litter decomposition was determined in agricultural land, pastureland and wildlife protected areas during both wet and dry seasons and in mesic and wet rainfall regions across the borders of the Serengeti National Park, Tanzania.ResultsMacrodetritivores consumed recalcitrant rooibos and mainly avoided labile green tea litter. On average macrodetritivores enhanced recalcitrant litter decomposition by 22%, but litter mass loss varied across land-uses, typically being higher on agricultural and pastureland compared to wildlife protected areas, and was sustained during periods of water scarcity. However, we observed instances of higher decomposition of recalcitrant litter by macrodetritivores in wildlife protected areas. In contrast, litter decomposition by microbes and microdetritivores was more constrained by seasonal and regional water availability with a minor influence of land-use.ConclusionWe found that moderate human-modification of savannahs is compatible with macrodetritivore litter decomposition. As savannahs become more intensely used by humans, raising ecological awareness among agropastoralist is required to ensure continued contribution of macrodetritivores to litter decomposition.

Five-year study on the effects of warming and plant litter quality on litter decomposition rate in a Tibetan alpine grassland

The decomposition of plant litter is a key link in global C budgets and provides strong feedback to changes in climate and biogeochemical cycles. However, the combined effects of global warming and plant litter quality on the rate of plant litter decomposition and nutrient dynamics in alpine ecosystems are still poorly understood. We conducted a warming experiment to investigate the effects of litter quality and temperature on decomposition rates and variations in nutrients of four common herbaceous plants (low-quality litter species Stipa purpurea and Carex moorcroftii and high-quality litter species Astragalus confertus and Leontopodium nanum) during 2011–2016. During the initial stages of decomposition, warming had no significant effect on the mass loss of plant litter for low-quality litter species, but in the later stages of decomposition, it had a negative effect on the mass loss across all species (P < 0.05). Litter quality was the best predictor of N and P release/immobilisation during the decomposition of aboveground plant litter. Low-quality litter had the highest immobilisation of N at about 80% of the initial remaining mass; nutrients were then released in the following stages of decomposition. However, the fraction of initial P decreased with the mass remaining during the initial and later phases of decomposition, but a short period of P immobilisation occurred in the middle phase of decomposition. For high-quality litter, the fraction of initial N and P decreased with the mass remaining during the whole decomposition process. Warming had a marginal influence on the N and P dynamics throughout the decomposition process. Our study showed that the decay of plant litter was strongly suppressed by warming climate and that the N and P dynamics on the investigated Tibetan grassland were mainly regulated by litter quality, providing valuable insights into the biogeochemical cycles of nutrients in alpine ecosystems.

Abiotic factors affect leaf litter mass loss more strongly than initial litter traits under sand burial conditions

Litter decomposition is an important ecosystem process and a key determinant of nutrient turnover and carbon cycling in arid and semiarid regions. Sand burial is common in arid and semiarid regions and may strongly influence litter decomposition. However, the main factors influencing litter decomposition under sand burial conditions are uncertain. We performed a litter bag experiment over 3 years to understand the effects of sand burial on litter mass loss and measured abiotic factors (light intensity, soil temperature and humidity) and initial litter traits to determine which factors most influenced litter mass losses. The leaf litters of three dominant shrubs (Artemisia halodendron, Caragana microphylla, and Salix gordejevii) in the Horqin Sandy Land of northern China were selected, and four burial depths (surface, 5 cm, 10 cm, and 20 cm) were used. The results showed that the litter from the three shrubs under the surface treatment (no burial) and at the 5 cm burial depth decomposed more rapidly than the litter that was buried at depths of 10 cm and 20 cm. This is explained because the abiotic factors on the surface and at 5 cm burial depth were conducive for the mass loss of litter. The differences in litter mass losses among the three shrubs were not significant under other burial treatments, except that A. halodendron’s litter decomposed significantly faster than litter from the other two shrubs at depths of 10 cm. Species differences in litter traits were weaker than the effects of burial depths and retrieval times on litter mass loss. The stepwise regression analysis showed that light intensity and soil temperature were the most important factors influencing the mean litter mass loss of 3 years. Therefore, we concluded that relative to the initial litter traits, abiotic factors are more able to indicate the leaf litter mass loss under sand burial conditions, and abiotic factors limiting litter mass loss switch with burial depths.

Litter chemical traits strongly drove the carbon fractions loss during decomposition across an alpine treeline ecotone

The decomposition of litter carbon (C) fraction is a major determinant of soil organic matter pool and nutrient cycling. However, knowledge of litter chemical traits regulate C fractions release is still relatively limited. A litterbag experiment was conducted using six plant functional litter types at two vegetation type (coniferous forest and alpine shrubland) in a treeline ecotone. We evaluated the relative importance of litter chemistry (i.e. Nutrient, C quality, and stoichiometry) on the loss of litter mass, non-polar extractables (NPE), water-soluble extractables (WSE), acid-hydrolyzable carbohydrates (ACID), and acid-unhydrolyzable residue (AUR) during decomposition. Litter nutrients contain nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), sodium (Na), magnesium (Mg), aluminium (Al), manganese (Mn), zinc (Zn), iron (Fe) and copper (Cu), litter C quality contains C, WSE, NPE, ACID, and AUR, and stoichiometry was defined by C:N, C:P; N:P, ACID:N, and AUR:N. The results showed single exponential model fitted decomposition rates of litter mass and C fractions better than double exponential or asymptotic decomposition, and the decomposition rates of C fractions were strongly correlated with initial litter nutrients, especially K, Na, Ca. Furthermore, the temporal dynamics of litter nutrients (Ca, Mg, Na, K, Zn, and Fe) strongly regulated C fractions loss during the decomposition process. Changes in litter C quality had an evident effect on the degradation of ACID and AUR, supporting the concept of “priming effect” of soluble carbon fraction. The significant differences were found in the release of NPE, WSE, and ACID rather than AUR among coniferous forest and alpine shrubland, and the vegetation type effects largely depend on the changes in litter stoichiometry, which is an important implication for the change in plant community abundance regulate decay. Collectively, elucidating the hierarchical drivers of litter chemistry on decomposition is critical to soil C sequestration in alpine ecosystems.

Urbanisation affects ecosystem functioning more than structure in tropical streams

Urbanisation poses a clear threat to tropical freshwater streams, yet fundamental knowledge gaps hinder our ability to effectively conserve stream biodiversity and preserve ecosystem functioning. Here, we studied the impact of urbanisation on structural and functional ecosystem responses in low-order streams in Singapore, a tropical city with a mosaic landscape of protected natural forests, managed buffer zones (between forest and open-country habitats), and built-up urban areas. We quantified an urbanisation gradient based on landscape, in-stream, and riparian conditions, and found an association between urbanisation and pollution-tolerant macroinvertebrates (e.g. freshwater snail and worm species) in litter bags. We also found greater macroinvertebrate abundance (mean individuals bag−1; forest: 30.3, buffer: 70.1, urban: 109.0) and richness (mean taxa bag−1; forest: 4.53, buffer: 4.75, urban: 7.50) in urban streams, but similar diversity across habitats. Higher levels of primary productivity (measured from algal accrual on ceramic tiles) and microbial decomposition (measured from litter-mass loss in mesh bags) at urban sites indicate rapid microbial activity at higher light, temperature, and nutrient levels. We found that urbanisation affected function 32% more than structure in the studied tropical streams, likely driven by greater algal growth in urban streams. These changes in ecological processes (i.e. ecosystem functioning) possibly lead to a loss of ecosystem services, which would negatively affect ecology, society, and economy. Our results point to possible management strategies (e.g. increasing vegetation density through buffer park creation) to reduce the impacts of urbanisation, restore vital ecosystem functions in tropical streams, and create habitat niches for native species.

Responses of litter decomposition in two subalpine plantations to simulated nitrogen deposition in central Yunnan, China

From February 2018 to January 2019, a field experiment of simulated nitrogen (N) depo-sition was conducted in Pinus armandii and Pinus yunnanensis plantations in the subalpine region of central Yunnan, China. The litterbag method was used for in situ litter (leaf and twig) decomposition experiment in both plantations. Four levels of N addition were applied, i.e., control (CK, 0 g N·m-2·a-1), low nitrogen (LN, 5 g N·m-2·a-1), medium nitrogen (MN, 15 g N·m-2·a-1), and high nitrogen (HN, 30 g N·m-2·a-1). The results showed that the annual decomposition rates of leaf and twig in P. armandii were 34.8% and 18.0%, which were higher than the 32.2% (leaf) and 16.1% (twig) in P. yunnanensis. Under N deposition, the LN treatment reduced the time of 95% mass loss of leaf and twig litter in P. armandii by 0.202 and 1.624 years, the MN treatment reduced by 0.045 and 1.437 years, and the HN treatment increased by 0.840 and 2.112 years, respectively. In the P. yunnanensis plantation, the LN treatment reduced the time of 95% mass loss of leaf and twig litter by 0.766 and 4.053 years, while the MN treatment increased by 0.366 and 0.455 years, and the HN treatment increased by 0.826 and 0.906 years, respectively. Litter (leaf and twig) decomposition of both P. armandii and P. yunnanensis were promoted by low N treatment and inhibited by high N treatment. The effects of N deposition on litter decomposition of two plantations were significantly correlated with the contents of cellulose and lignin in litter. In conclusion, the responses of litter decomposition to N deposition mainly depended on the litter substrate, especially cellulose and lignin contents.

Decomposition of leaf litter mixtures across biomes: The role of litter identity, diversity and soil fauna

Abstract At broad spatial scales, the factors regulating litter decomposition remain ambiguous, with the understanding of these factors largely based on studies investigating site‐specific single litter species, whereas studies using multi litter species mixtures across sites are rare. We exposed in microcosms containing single species and all possible mixtures of four leaf litter species differing widely in initial chemical and physical characteristics from a temperate forest to the climatic conditions of four different forests across the Northern Hemisphere for 1 year. Calcium, magnesium and condensed tannins predicted litter mass loss of single litter species and mixtures across forest types and biomes, regardless of species richness and microarthropod presence. However, relative mixture effects differed among forest types and varied with the access to the litter by microarthropods. Access to the microcosms by microarthropods modified the decomposition of individual litter species within mixtures, which differed among forest types independent of litter species richness and composition of litter mixtures. However, soil microarthropods generally only little affected litter decomposition. Synthesis. We conclude that litter identity is the dominant driver of decomposition across different forest types and the non‐additive litter mixture effects vary among biomes despite identical leaf litter chemistry. These results suggest that across large spatial scales the environmental context of decomposing litter mixtures, including microarthropod communities, determine the decomposition of litter mixtures besides strong litter trait‐based effects.

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.

Drought conditions alter litter decomposition and nutrient release of litter types in an agroforestry system of China.

Evaluating how decomposition rates and litter nutrient release of different litter types respond to changes in water conditions is crucial for understanding global carbon and nutrient cycling. However, it is unclear how decreasing water affects litter mixture interactions for the maize–poplar system in arid regions. Here, the responses of the litter decomposition process and litter mixture interactions in the agroforestry system to changes in water conditions (control, light drought, and moderate drought) were tested. Moderate drought significantly decreased the decomposition rate for poplar leaf and mixed litters, and decomposition rate was significantly reduced for maize straw litter in light and moderate drought stress. The mass loss rates of maize straw and mixed litters were significantly higher than that of the poplar leaf litter under drought conditions, but there was no significant difference among the three litter types in the control. There was no interaction between mass loss of the mixed litter in the control and light drought conditions, and the litter mixture interaction showed nonadditive synergistic interactions under moderate drought. In terms of nutrient release, there was also no interaction between litter mixture with nitrogen and carbon, but there was antagonistic interaction with potassium release under the light drought condition. Our results demonstrate that drought conditions can lead to decreasing decomposition rate and strong changes in the litter mixture interactions from additive effects to nonadditive synergistic effects in moderate drought. Moreover, light drought changed the mixture interaction from an additive effect to an antagonistic interaction for potassium release.

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.

Increasing Precipitation Interval Has More Impacts on Litter Mass Loss Than Decreasing Precipitation Amount in Desert Steppe

Litter mass loss and nutrient release are key links in the material cycling and energy flowing in ecosystems and of special ecological significance in maintaining ecosystem stability, improving soil structure and promoting vegetation restoration in the arid and semi-arid regions. Furthermore, litter mass loss could be affected by the change in precipitation patterns. However, currently, most studies on the response of litter mass loss to precipitation pattern change focus on the precipitation amount much more than the precipitation frequency. Therefore, we conducted a three-year manipulative research in a desert steppe to assess the effects of decreasing precipitation amount and increasing precipitation interval on the litter mass loss of Stipa klemenzii, and their relationships with litter chemical traits (contents of carbon (C), nitrogen (N), phosphorus (P), potassium (K), lignin and ash, C/N ratio and lignin/N ratio) and abiotic factors (light intensity and temperature and humidity of soil and air). The results showed that (1) both the treatments have negative effects on litter mass loss; (2) for abiotic factors, both the treatments only affected soil moisture; for biotic factors, both the treatments decreased the litter lignin contents, the increased precipitation interval treatment decreased the litter N and K contents while increased the litter C/N ratio and lignin/N ratio; (3) the main control of litter mass loss was due to our manipulation of drought regime and its effects on the soil decomposition environment, rather to other factors such as litter quality or light intensity; (4) compare to decreased precipitation amount, increased precipitation interval has more impact on litter mass loss, and this was caused by the increased litter C/N ratio in increased precipitation interval treatment. We speculated that increased precipitation interval was a harsher abiotic factor for the decomposer, and more research on this should be conducted in the future.

Effects of terrestrial isopods on soil nutrients during litter decomposition

Soil fauna are important biological factors that affect litter decomposition and play an important role in the release of nutrients, such as carbon and nitrogen. This study focused on the role of soil fauna in litter decomposition. Field microcosm experiments were conducted to assess the influence of isopods (Porcellionidae and Armadillidiidae) on soil nutrients during the litter decomposition of Catalpa bungei (CL), Platanus acerifolia (PL), and Aesculus chinensis (AL). The litter mass loss and nutrients in different soil layers treated with various isopods were determined in three-month microcosm incubations. Results showed that the presence of isopods significantly increased (P < 0.05) the litter decomposition rates compared with the control treatment (CK). The average weight (2.56 g) and total weight ratio (85.47%) of the isopod-decomposed litter were much larger than those of the CK treatment (0.43 g and 14.31%, respectively). In the different litter types collected, CL showed the highest decomposition rate among the different isopod treatments. Isopods increased the contents of organic carbon (OC), total nitrogen (TN), total potassium (TP), Olsen phosphorus (OP), available potassium (AK), ammonia nitrogen (NH4+–N), and nitrate nitrogen (NO3––N) in the surface soil by 59.19%, 27.36%, 2.72%, 29.30%, 5.85%, 13.10%, and 14.60%, respectively, relative to CK. The profile distribution of soil nutrients and the soil quality index under different isopod treatments were significantly (P < 0.05) greater in the 0–1 cm soil layer than in the 1–2, 2–4, and 4–6 cm soil layers. Further analysis showed that this significance was affected by decomposition time, isopod species, soil depth, and the interactions of these factors. The findings demonstrate that the isopods could accelerate litter decomposition and improve soil nutrients. This work provides evidence demonstrating that soil fauna can improve surface soil quality by promoting litter decomposition.

Influence of moisture, nutrients, and distance from stream on early-stage mass loss of western red cedar leaf litter in headwater riparian forests

Western red cedar (Thuja plicata Donn ex D.Don) is a dominant species in forests of the Pacific Northwest in North America, but little is known about its decomposition in riparian habitat. We experimentally tested how early-stage mass loss of cedar leaf litter varied with distance from the stream (five distances from 1 to 40 m away) and responded to nutrient and water additions near four headwater streams in southwestern British Columbia. We ran three coarse-mesh litterbag trials in durations between five months to one year from January 2013 and January 2014. Litterbags were either untreated or given the following treatments: water additions during dry summer months, nitrogen and phosphorus additions, or additions of both. Control litterbags lost 21% initial mass over 12 months (January 2013 – January 2014), 20% over five months (January 2013 – June 2013), and 15% over eight months (June 2013 – January 2014). Rates of mass loss did not increase with water in any trial but did increase with nutrients in the 12-month trial. Litter located 40 m from the stream lost 7% more mass than that located 1 m away in this same trial. Our study indicates that cedar leaf litter mass loss responded primarily to nutrient additions.

Tree litter functional diversity and nitrogen concentration enhance litter decomposition via changes in earthworm communities.

Biodiversity is a major driver of numerous ecosystem functions. However, consequences of changes in forest biodiversity remain difficult to predict because of limited knowledge about how tree diversity influences ecosystem functions. Litter decomposition is a key process affecting nutrient cycling, productivity, and carbon storage and can be influenced by plant biodiversity. Leaf litter species composition, environmental conditions, and the detritivore community are main components of the decomposition process, but their complex interactions are poorly understood. In this study, we tested the effect of tree functional diversity (FD) on litter decomposition in a field experiment manipulating tree diversity and partitioned the effects of litter physiochemical diversity and the detritivore community. We used litterbags with different mesh sizes to separate the effects of microorganisms and microfauna, mesofauna, and macrofauna and monitored soil fauna using pitfall traps and earthworm extractions. We hypothesized that higher tree litter FD accelerates litter decomposition due to the availability of complementary food components and higher activity of detritivores. Although we did not find direct effects of tree FD on litter decomposition, we identified key litter traits and macrodetritivores that explained part of the process. Litter mass loss was found to decrease with an increase in leaf litter carbon:nitrogen ratio. Moreover, litter mass loss increased with an increasing density of epigeic earthworms, with most pronounced effects in litterbags with a smaller mesh size, indicating indirect effects. Higher litter FD and litter nutrient content were found to increase the density of surface‐dwelling macrofauna and epigeic earthworm biomass. Based on structural equation modeling, we conclude that tree FD has a weak positive effect on soil surface litter decomposition by increasing the density of epigeic earthworms and that litter nitrogen‐related traits play a central role in tree composition effects on soil fauna and decomposition.

In situ litter decomposition and nutrient release from forest trees along an elevation gradient in Central Himalaya

Litter plays a central role in the nutrient budgets of forests by supplying inflow to nutrient turnover through decomposition. However, studies of litter decomposition and nutrient dynamics in forest ecosystems are limited, particularly for the central Himalaya forest ecosystems with wide importance for stability and nutrient dynamics under global change. A one-year-long in-situ litter decomposition experiment was conducted with multiple tree species, dominating forests along an elevation gradient from 1300 to 2500 meters above sea level (m.a.s.l.) in central Nepal. The main aim was to examine the litter mass loss, factors affecting the decomposition process and the nutrient dynamics of the studied tree species, based on the litter bag method and physico-chemical analyses of the litter and the soil over time. The results showed that litter mass loss decreased with elevation, being the highest at low elevation (63.65%), followed by middle (46.59%) and high elevation (44.48%). The litter from deciduous tree species decomposed more rapidly than that from evergreen species, with Alnus litter decomposing the fastest (1.42 yr−1) and Pinus litter decomposing the slowest (0.53 yr−1), whereas the other species were in the order of Engelhardia > Castanopsis > Eurya > Lyonia > Quercus > Rhododendron > Schima. The contents of carbon (C), nitrogen (N), phosphorus (P) and potassium (K) in the initial litter (i.e., freshly fallen leaves), as well as weather factors (precipitation and temperature) were the best predictors of litter mass loss. The nutrient release from the litter was not discerned throughout the annual decomposition process, however, the release rate at the end of the study period followed the order of P > K > C > N, indicating that litter is a potential sink of N due to its slow release rate. This study may serve as a baseline for long-term research on nutrient dynamics in forest ecosystems of central and eastern Himalaya, which is imperative for preserving biodiversity and ecosystem stability and for mitigating climate change impacts.

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

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

Interspecific difference in N:P stoichiometric homeostasis drives nutrient release and soil microbial community composition during decomposition

Tree species can produce litter with large variation in nitrogen to phosphorus (N:P) ratios. Here we examined how litter N:P ratios affected decomposer community composition and nutrient release for two contrasting tree species in the Qinling Mountains, China. Two-year-old Quercus aliena var. acuteserrata and Pinus tabulaeformis seedlings were fertilized using nutrient solutions with varying N:P ratios for four months. The obtained litters with contrasting N:P stoichiometry were left to decompose on nutrient-free quartz sand for 12 weeks with microbial inoculum. Then, the post-decomposition microbial community composition was determined using a phospholipid fatty acid (PLFA) analysis. The Q. aliena litter stoichiometry was more homeostatic than P. tabulaeformis litter. Litter N:P ratio was significantly related to litter nutrient loss and mass loss for P. tabulaeformis but not always for Q. aliena. The soil microbial community compositions showed larger fungal to bacterial (F:B) ratios with increasing litter N:P ratios for Q. aliena but not P. tabulaeformis. Litter N:P ratio, as determined by species-specific homeostasis, showed an interspecific difference to affect the patterns of litter decomposition dynamics, as well as related soil microbial community composition. The less variation in the soil microbial community composition than plant litter stoichiometric characteristics during decomposition is likely an important mechanism that regulates the balance of biogeochemical cycles in the Qinling Mountains.

Termite Control of Leaf Litter Decomposition of Eight Selected Plant Species of Sudano-guinea Savannahs of Ngaoundere, Cameroon

Few studies on effects of termites on litter decomposition have been done in African savannahs, particularly in the Adamawa savannahs of Cameroon. In the framework of management of resource quality to restore or improve soil fertility of farming systems of Sudano-guinea savannahs of Ngaoundere, Cameroon, study on termites’ control of leaf litter decomposition of eight plant species was conducted on the field. The selected plant species are Bixa orellana, Erythrina sigmoïdea, Ficus polita, Maytenus senegalensis, Mucuna stans, Piliostigma thonningii, Vitex madiensis and Vitellaria paradoxa. Leaf litter samples were incubated in situ using litterbags of 2 mm mesh during 24 weeks in two plots out of canopy, corresponding to two treatments, with and without termites. Experimental design was split-plot with three replications. Collected data was carried out on litter dry mass remaining (LMR). Results showed total mass loss at the end of incubation time (24 weeks) and decomposition rate constants (k) differed significantly among plant species for the two treatments. The values ranged respectively from 23.05% and 0.012 week-1 in V. madiensis to 61.93% of initial dry mass and 0.046 week-1 in P. thonningii for treatment without termites and from 43.88% and 0.022 week-1 in B. orellana to 91.51% and 0.095 week-1 in P. thonningii for treatment with termites. These macro organisms fasted litter decomposition in all plant species, with intensity variation according to species. Litter mass loss and decomposition rate constant (k) correlated with litter thickness, density, area and specific area mass, and these relationships were influenced by the presence of termites. Globally litter decomposition was influenced by termite activities and resource quality. These results contributed to understand litter decomposition process in the sudano-guinea savannahs of Ngaoundere in order improve soil fertility, nutrient cycling and some plant species domestication.

Spectral Composition of Sunlight Affects the Microbial Functional Structure of Beech Leaf Litter During the Initial Phase of Decomposition

AimsThis study tests whether different spectral regions of sunlight affect the microbial decomposer assemblage in surface leaf litter in a beech understorey over the first 6 months following leaf senescence.MethodsWe performed a litterbag experiment employing filters attenuating combinations of UV-B, UV-A, blue, and green light as well as the whole spectrum of sunlight. We measured changes in microbial biomass and community structure, litter mass loss and litter chemistry during the first 6 months of decomposition.ResultsFungal and total microbial biomass were highest in the treatment excluding UV radiation, blue and green light. Exclusion of UV-B radiation decreased the fungal:bacterial biomass ratio and litter nitrogen content. Bacterial biomass was lower in the dark treatment compared to treatments receiving at least part of the solar spectrum. Our filter treatments affected microbial functional structure from the beginning of the experiment, whereas mass loss was only significantly affected after 6 months of decomposition and no effect was found on litter carbon content.ConclusionsThis study proves that sunlight, in a spectrally dependent manner, affects both microbial functional structure and biomass in temperate deciduous forests early in the decomposition process, with bacteria tending to dominate in sunlight and fungi in dark conditions. We found sunlight to be important in the decomposition in temperate forest understoreys despite the low irradiance characterizing these environments. However, long-term studies are required to estimate the relative contribution of sunlight among factors affecting the eventual incorporation of decomposing leaf litter into forest soils.

Shifts in Key Leaf Litter Traits Can Predict Effects of Plant Diversity Loss on Decomposition in Streams

Plant biodiversity loss in riparian forests is known to alter key stream ecosystem processes such as leaf litter decomposition. One potential mechanism mediating this biodiversity–decomposition relationship is the increased variability of plant functional traits at higher levels of biodiversity, providing more varied resources for decomposers and thus improving their function. We explored this in a field experiment exposing litter from different assemblages with low or high trait variability (measured through phylogenetic distance, PD) to microbial decomposers and invertebrate detritivores within litterbags in a low-order stream. Litter assemblages generally lost less mass but more phosphorus (P) than expected from monocultures, and nitrogen (N) tended to increase in the absence of detritivores and decrease in their presence, with little effect of PD. In contrast, there were strong influences of mean values and variability of specific traits (mostly N, P and condensed tannins) on decomposition and on net diversity effects. The negative diversity effect on litter mass loss was mainly driven by negative complementarity (that is, physical or chemical interference among species or traits), although there was positive selection (that is, particular species or traits with large effects on decomposition) in high-PD assemblages with detritivores. High-PD assemblages tended to have more invertebrates and attracted more typical litter-consuming detritivores. Our study suggests that decomposition of litter assemblages is mainly driven by concentration and variability of several key litter traits, rather than overall trait heterogeneity (measured through PD). However, differences in invertebrates colonizing high-PD and low-PD assemblages pointed to potential long-term effects of PD on decomposition.