Litter Decay Rates Research Articles

Bacterial population-level trade-offs between drought tolerance and resource acquisition traits impact decomposition.

Microbes drive fundamental ecosystem processes such as decomposition. Environmental stressors are known to affect microbes, their fitness, and the ecosystem functions that they perform, yet understanding the causal mechanisms behind this influence has been difficult. We used leaf litter on soil surface as a model in situ system to assess changes in bacterial genomic traits and decomposition rates over 18months with drought as a stressor. We hypothesized that genome-scale trade-offs due to investment in stress tolerance traits under drought reduce the capacity for bacterial populations to carry out decomposition, and that these population-level trade-offs scale up to impact emergent community traits thereby reducing decomposition rates. We observed drought tolerance mechanisms that were heightened in bacterial populations under drought, identified as higher gene copy numbers in metagenome-assembled genomes. A subset of populations under drought had reduced carbohydrate-active enzyme genes which suggested - as a trade-off - a decline in decomposition capabilities. These trade-offs were driven by community succession and taxonomic shifts as distinct patterns appeared in populations. We show that trait-tradeoffs in bacterial populations under drought could scale up to reduce overall decomposition capabilities and litter decay rates. Using a trait-based approach to assess the population ecology of soil bacteria, we demonstrate genome-level trade-offs in response to drought with consequences for decomposition rates.

Variations in litterfall dynamics, root biomass, and sediment accretion in restored and recolonized mangroves in Leyte, Philippines

Litterfall production and decay, root biomass, and sediment accretion dynamics were investigated from restored ‘planted’ (R5, R8, R15, and R30 stands) and recolonized stands (C5, C12, and C20 stands) to investigate patterns in primary productivity, belowground biomass, and sediment accretion dynamics. Litterfall data was collected using litter traps over 12 months, while decay kinetics was investigated using a litterbag experiment. Root biomass and sediment accretion data were collected using makeshift acrylic corers. Litterfall production increased as stands aged, and tended to stabilize as it matured in restored (R8: 10.05 Mg/ha/yr; R30: 6.1 Mg/ha/yr) and recolonized stands (C5: 18.75 Mg/ha/yr; C20: 9.05 Mg/ha/yr). Leaf litter decay rates (K/d) showed no pattern with stand age, although the recolonized stands (range: 0.059–0.113 K/d) had lower decay rates compared to the restored (range: 0.073–0.123 K/d) and natural stands (range: 0.064–0.123 K/d). Root biomass declined with age in restored stands (R5: 67.16 Mg/ha, R30: 49.67 Mg/ha), but increased in recolonized stands (C5: 5.41 Mg/ha, C20: 19.50 Mg/ha). Very high rates of sediment accretion were found in younger restored (R5: 10.1 cm/yr) and recolonized stands (C5: 8.1 cm/yr) than mature stands (R30: 6.3 cm/yr; C20: 4.3 cm/yr). Our results showed disparities of patterns in mangrove vegetation growth in recolonized stands and huge potential contribution on mangrove productivity when these areas are effectively restored.

Multi-kingdom characterization of living organisms by 13C CPMAS NMR spectroscopy reveals unique traits in bacteria, fungi, algae, and higher plants

Determining the chemical quality of soil organic matter and decomposing organisms is critical for predicting carbon fluxes in ecosystems. However, the classical C/N and lignin/N ratios have been criticized for their capability in predicting ecosystem function including litter decay rate, nitrogen mineralization and soil aggregation. Therefore, with our work we aim to complement information on the chemical properties of primary producers and decomposers based on 13C NMR. Overall, 108 unique 13C NMR spectra were collected from higher plant tissues including leaf litter, fine roots, woody debris, as well as a range of microbes i.e. bacteria, fungi, and marine algae. Results showed clear discrimination between organisms belonging to different kingdoms, but with limited variability within bacteria, fungi, and microalgae. In detail, bacteria were found to be distinct not only from plant tissues but also from fungi, characterized by a high proportion of alkyl and carbonyl C types and a rather low relative abundance of O Alkyl C and di-O Alkyl C types. Among the fungi, we found clear separation between yeasts, which are more similar to bacteria, and filamentous species, which are rich in O Alkyl and di-O Alkyl C types. Microalgae are characterized by a high content of aliphatic, carboxylic and methoxyl C fractions. In the spectra of terrestrial plants, the O Alkyl C region, associated with sugars and cellulose, is more abundant compared to algae and bacteria. In addition, the aromatic carbon signal, which is mainly associated with lignin, is much higher for higher plants than in microorganisms. As for plant tissues, woody tissues are clearly different from leaves and fine roots, with grasses, sedges, and ferns being well distinguished from forbs, coniferous and deciduous trees. In summary, our study contains the largest freely available 13C NMR spectral library of bacteria, fungi, algae, and higher plant tissues. However, the data from higher plants are sufficient to cover different functional types, which is not yet possible for bacteria and fungi.

Feedback of litter decay to temporal stability of biomass under N‐inputs

AbstractNitrogen (N) input affects litter decay and ecosystem functioning. However, the mechanism of litter decay under temporal N‐inputs has rarely been observed. Here we show that three‐year experimental N‐inputs significantly stimulated the rate of litter decay to some extent and then inhibited it with increasing N‐inputs. The N‐inputs affected the litter's mass loss by directly influencing the temporal stability of aboveground biomass (BS) and diversity while indirectly changing soil pH, C: N ratio, and synergistic interactions of soil, vegetation, and microbial traits. The BS has emerged as a significant regulatory factor for the litter decay of tropical grassland. The outcome of the present study will be helpful in predicting the global feedback of litter decay on the N inputs and the amount of N required for the sustainable functioning of the degraded tropical or similar grasslands.

Warming drives feedback between plant phenotypes and ecosystem functioning in sub-Antarctic ponds

Ample evidence indicates that warming affects individuals in plant communities, ultimately threatening biodiversity. Individual plants in communities are also exposed to plant–plant interaction that may affect their performance. However, trait responses to these two constraints have usually been studied separately, while they may influence processes at the ecosystem level. In turn, these ecological modifications may impact the phenotypes of plants through nutrient availability and uptake. We developed an experimental approach based on the macrophyte communities in the ponds of the sub-Antarctic Iles Kerguelen. Individuals of the species Limosella australis were grown under different temperature × plant–plant interaction treatments to assess their trait responses and create litters with different characteristics. The litters were then decomposed in the presence of individual plants at different temperatures to examine effects on ecosystem functioning and potential feedback affecting plant trait values. Leaf resource-acquisition– and -conservation–related traits were altered in the context of temperature × plant–plant interaction. At 13 °C, SLA and leaf C:N were higher under interspecific and intraspecific interactions than without interaction, whereas at 23 °C, these traits increased under intraspecific interaction only. These effects only slightly improved the individual performance, suggesting that plant–plant interaction is an additional selective pressure on individuals in the context of climate warming. The decay rate of litter increased with the Leaf Carbon Content at 13 °C and 18 °C, but decreased at 23 °C. The highest decay rate was recorded at 18 °C. Besides, we observed evidence of positive feedback of the decay rate alone, and in interaction with the temperature, respectively on the leaf C:N and Leaf Dry Matter Content, suggesting that variations in ecological processes affect plant phenotypes. Our findings demonstrate that warming can directly and indirectly affect the evolutionary and ecological processes occurring in aquatic ecosystems through plants.

Legume versus non-legume foliar litter decomposition in regularly burned loblolly pine forests

While understory prescribed burning is central to the ecological and economic management of many pine forests, there is concern that burning may cause excessive losses of N, thereby decreasing soil fertility and forest productivity. Symbiotic N2-fixation by fire-adapted native and naturalized herbaceous legumes may mitigate N losses due to burning. However, the N gain via legumes depends not only on the rates of N2-fixation, but also on the rates of litter decay between burn events. At present, the rates and controls of relatively N-rich legume litter decay in forests are poorly understood. In this study, foliar litter decomposition was assessed for 6 legume species (average [N] = 1.83 ± 0.52 %) and 4 non-legume species (average [N] = 0.80 ± 0.27 %) in “early” and “late” stage loblolly pine (Pinus taeda) forests for 3 years. We hypothesized that the N-rich legumes would exhibit greater mass loss, particularly in the early sites, and would thus release a greater percentage of their original N compared to the non-legumes. In contrast to our hypothesis, average mass loss rates were comparable for the legumes and non-legumes resulting in similar residual mass estimates (mean [95 % CI]) respectively in the early (11.9 % [9.8 %, 14.4 %] versus 15.5 % [12.2 %, 19.7 %]) and late (12.5 % [10.3 %, 15.1 %] versus 9.0 % [7.1 %, 11.3 %]) sites by the end of the study. Likewise, the average decay rate (k) for the legumes and non-legumes did not differ significantly in the early sites (0.73 ± 0.25 year−1 versus 0.69 ± 0.15 year−1, respectively), and the average legume decay rate was lower (P = 0.0080) than the average non-legume decay rate in the late sites (0.58 ± 0.18 year−1 versus 0.63 ± 0.13 year−1, respectively). Mass loss was typically greater in the early sites, but the differences were significant for less than 22 % of the comparisons. As hypothesized, legumes did release a greater percentage of their original N compared to non-legumes resulting in lower average N remaining estimates respectively in the early (34.2 % [29.4 %, 39.8 %] versus 51.3 % [40.2 %, 65.5 %]) and late (28.9 % [24.2 %, 34.5 %] versus 42.5 % [29.6 %, 61.1 %]) sites after 3 years. The results suggest that N, P, and S were co-regulators of litter decay, and that pine litter may be an important sink for these limiting macronutrients. The strong interplay among N, P, and S should be considered in the use of prescribed burning to reduce nutrient limitations in fire-maintained pine forests.

Do global change variables alter mangrove decomposition? A systematic review

AbstractAimGlobal change is expected to modify the magnitude and trajectory of organic matter decomposition in mangrove ecosystems. Yet, the degree and direction of that change is unknown, especially considering the large C storage potential that mangroves provide. We performed a systematic review of primary literature to examine the relationships between genus‐specific litter quality, latitude or other global change proxies and decomposition of mangrove litter fractions.LocationGlobal.Time Period1976–2021.TaxonMangroves.MethodsWe compiled a dataset of 480 decomposition rates, including species, litter fraction, latitude, and relevant biophysical data. We investigated the influence of genera, tissue type, latitude, and global change proxies on decomposition rates using linear models and qualitative approaches. We also performed calculations to determine the potential importance of the decomposition process on the root litter biomass C pool in the context of blue C significance.ResultsCollectively, latitudinal relationships suggest that factors other than temperature, such as tissue type and genus, may regulate decay rates within mangroves' distributional range. Decay rates of leaf litter, roots, and wood converged on a value of 0.009 ± 0.0005, 0.002 ± 0.0001, and 0.001 ± 0.0003, respectively, across continents and geomorphological settings. Our calculations suggest that small changes in decomposition rate will not elicit large changes in blue C storage potential.ConclusionsThe main drivers behind variability in mangrove biomass decay rates detected across the distributional range remain uncertain. However, the small latitudinal range that mangroves inhabit and the submerged environment within which litter decomposes suggest that decay depends on species‐specific responses or biotic interactions among species to global change drivers. Few studies have examined global change impacts directly, and variability in decay and lack of representation of some mangrove groups in the literature suggest that implications for blue C are important to consider.

Soil carbon dynamics are linked to tree species growth strategy in a naturally regenerating tropical forest

Secondary tropical forests are increasingly important for their role in the global carbon (C) balance as they can rapidly accumulate aboveground biomass C during regrowth. Substantial amounts of plant-derived carbon are also incorporated into the soil through decomposition processes, but our understanding of soil C dynamics during forest regrowth is limited. Secondary succession is characterised by a shift in tree functional groups from light-demanding to shade-tolerant species over time, which can influence rates of C turnover via differences in litter quality and by modifying the decomposition environment. Changes in decomposition processes in turn affect the amount of organic C stored in the soil or released to the atmosphere as CO2. Consequently, understanding how tree functional composition influences C turnover during decomposition could help us predict soil C storage during tropical forest regrowth. We experimentally explored the relationship between tree functional groups and soil C dynamics (decomposition and respiration) by conducting a litter decomposition experiment across a successional gradient of naturally regenerating tropical forest. We created litter mixtures representing tree communities differing in their shade tolerance, as well as a functionally diverse litter mixture, and observed litter mass loss and soil respiration as measures of C turnover over a 6 month period. Litter from light-demanding species decomposed faster than litter from shade-tolerant species, which was reflected in the pattern of soil respiration. There were no clear patterns of increasing or decreasing rates of litter decay or soil respiration with increasing forest age, but there was an interaction between stand age and litter type which influenced both decomposition and soil respiration rates. Interestingly, soil respiration from the functionally diverse litter mixture was significantly higher in the younger than older forest stands, and the functionally diverse litter mixture decayed more rapidly than expected in one of the younger stands. Our findings highlight the potential importance of functionally diverse plant inputs, as well as the interaction between local environmental attributes and litter type, for soil C dynamics in tropical forests.

Temperature sensitivity and decomposition rate of 101 leaf litter types from Mediterranean ecosystems

Litter decomposition is a fundamental process, and the number of published studies has steadily increased in recent decades. However, few experiments have systematically compared a large number of litter types and evaluated their temperature sensitivity. We conducted a two-year experiment on the decomposition of litter bags containing 101 leaf litter sampled in Mediterranean ecosystems and incubated under laboratory conditions at 4 °C, 14 °C, and 24 °C. Litter was chemically characterized and analysed for carbon (C), nitrogen (N), cellulose and lignin concentration, C/N, and lignin/N ratios, which serve as predictors of decomposition rate. The sensitivity of litter decay rate to temperature was evaluated using Q10. Leaf litter chemistry varied widely in nitrogen content (range 0.52–6.80 %), lignin content (range 1.53–49.31 %), C/N ratio (range 5.21–77.78), and lignin/N ratio (range 0.34–34.90). Litter decomposition rate was negatively related to initial lignin concentration, lignin/N ratio, and C/N ratio, but only in the early stage. In the late stages of decomposition, litter decay rate was negatively correlated with initial N concentration but positively correlated with C/N and lignin/N ratios. Temperature sensitivity was negatively correlated with N concentration and positively correlated with lignin and lignin/N ratio. It is noteworthy that, contrary to expectations, temperature sensitivity exhibited a hump-shaped relationship with decay rate. N, C/N, and lignin/N ratios should be used with caution because their predictive power is reversed with respect to decomposition rate during the decomposition process. In addition, the new finding that temperature sensitivity has a hump-shaped relationship with decomposition rate deserves further confirmation and could be considered in ecosystem-level organic C modeling.

Decomposition of green tea and rooibos tea across three monospecific temperate forests: Effect of litter type and tree species

We studied the effect of different forest covers on carbon (C) and nitrogen (N) dynamics of two standardised litters during decomposition in soil. For this purpose, commercially available bags containing green tea or rooibos tea were incubated in close monospecific stands of Fagus sylvatica, Pseudotsuga menziesii, and Quercus cerris, in the Apennines range, Italy, and then analysed at different intervals for up to two years. We also investigated the fate of various C functional groups in both types of litter under beech by nuclear magnetic resonance spectroscopy. After two years of incubation, green tea had not changed its original C/N ratio of 10, while rooibos tea had nearly halved its original value of 45, because of different C and N dynamics. Both litters progressively lost C, about fifty per cent of the initial content in the case of rooibos tea, and a little more for green tea, most of the loss occurring in the first three months. In terms of N, green tea behaved as for C, while rooibos tea in the early stage lost part of its N stock, fully recovering it by the end of the first year. Under beech, both litters showed a preferential loss in carbohydrates during the first trimester of incubation and, consequently, an indirect enrichment in lipids. Later on, the relative contribution of the various C forms remained practically constant.Our results overall support that the decay rate and compositional changes of litter depend strongly on the litter type and little on the tree cover of the soil in which the litter is incubated.

Litter Deposition and Nutrient Cycling of Invaded Environments by Cryptostegia madagascariensis at Tropical Cambisols from Northeastern Brazil

Cryptostegia madagascariensis is an invasive plant species that covers 11% of the Brazilian northeastern territory, but its role on the litter trait in tropical ecosystems remains unclear. Here, we analyzed and compared the litter deposition, litter nutrient content, soil organic matter, and the litter decay rate from invaded and non-invaded environments by C. madagascariensis at a tropical Cambisol. The PCA analysis revealed that litter deposition, litter quality, and soil organic matter were correlated with the invaded environment. We grew plant species in greenhouse conditions to obtain a standard litter material to use in our litter bags in field conditions. We found that litter decay rate was higher in the invaded environment than in the non-invaded one. Our results suggest that C. madagascariensis changes litter traits in tropical ecosystems that in turn create negative plant–soil feedback to the native species by creating a physical barrier on soil surface and to promote its own rhizosphere.

Soil biota community structure and litter traits of grape vine plantation and natural ecosystem from Southern Brazil

Vitis vinifera is a common plant species cultivated in Southern Brazil for vine production. Although this plant species is commonly found near the Mixed Ombrophilous Forest, the V. vinifera plantation is cultivated in areas for a long-term thus changing the soil ecosystem and functional diversity. We aimed to compare the soil chemical properties, soil biota assemblage, litter traits, decay rate and priming effect in the two adjacent environments (e.g., grape vine plantation vs. natural ecosystem). Soil chemical properties, soil biota community composition, and litter traits of V. vinifera plantation were compared with an adjacent natural ecosystem (e.g., Mixed Ombrophilous Forest) from September 2019 to June 2021. Litter decay rate and priming effect was estimated by using native tree residues on litter bags in both studied environments. We also assessed the influence of soil biota on decay rate through a litterbag assay. Our results showed that both studied environments differed in soil chemical properties and soil biota community composition. However, in the V. vinifera plantation litter decay rate, and priming effect were higher, due to the presence and activities of soil organisms from Collembola - Paronellidae. Thermal amplitude, litter quality, and soil organisms’ activity were the main factors contributing to the data variance. Both native tree residues, A. angustifolia and D. sellowiana, showed the highest decay rate and priming effect in the V. vinifera plantation. Our work increases the understanding of the soil food web and ecological processes (litter deposition and nutrient cycling) into subtropical ecosystems. The V. vinifera plantation following a monocropping system does not provide resources to create a well-developed soil food web, which overtime creates negative plant-soil feedback when compared to the natural ecosystem. However, our study opens a new perspective for a future agroforestry system using two endangered species from the Brazilian Mixed Ombrophilous Forest seeking for vine production, soil sustainability, and biodiversity conservation.

Litter quality and decomposition responses to drought in a northeastern US deciduous forest

Even though drought impacts on tree physiology have been identified, whether drought affects leaf litter chemistry that, in turn, influences litter decay rates is still poorly understood. We compared litter quality and decomposition for two cohorts of leaves from five co-occurring seasonally deciduous tree species: Acer saccharum, Tilia americana, Quercus rubra, Quercus alba, and Ostrya virginiana. One cohort experienced a growing-season drought, and the other cohortcame from the same trees in the ensuing, post-drought growing season. Leaf litter production was greater for drought litter than post-drought litter for all five species. Specific leaf area and nitrogen concentrations were 20% greater for the drought cohort than the post-drought cohort. Concentrations of non-structural carbohydrates were about 14% greater for the drought cohort, except for greater values for post-drought A. saccharum litter. Pectin in the middle lamella of leaf litter was 31% lower for the drought cohort compared to post-drought cohort. We found few differences in litter decay rates between drought and post-drought cohorts, although Q. rubra litter had more decomposition for the post-drought cohort than the drought cohort, whereas A. saccharum litter had more decomposition for the drought cohort than the post-drought cohort. Leaf litter decay rates for the drought cohort were related to litter nitrogen and lignin concentrations, whereas decay rates for the post-drought cohort were related to litter carbohydrate concentrations. Our findings suggest that the role of drought events on seasonally deciduous forest ecosystems must recognize species-specific, idiosyncratic responses in leaf litter quality and decomposition.

Accounting for non-rainfall moisture and temperature improves litter decay model performance in a fog-dominated dryland system

Abstract. Historically, ecosystem models have treated rainfall as the primary moisture source driving litter decomposition. In many arid and semi-arid lands, however, non-rainfall moisture (fog, dew, and water vapor) plays a more important role in supporting microbial activity and carbon turnover. To date though, we lack a robust approach for modeling the role of non-rainfall moisture in litter decomposition. We developed a series of simple litter decay models with different moisture sensitivity and temperature sensitivity functions to explicitly represent the role of non-rainfall moisture in the litter decay process. To evaluate model performance, we conducted a 30-month litter decomposition study at 6 sites along a fog and dew gradient in the Namib desert, spanning almost an eightfold difference in non-rainfall moisture frequency. Litter decay rates in the field correlated with fog and dew frequencies but not with rainfall. Including either temperature or non-rainfall moisture sensitivity functions improved model performance, but the combination of temperature and moisture sensitivity together provided more realistic estimates of litter decomposition than relying on either alone. Model performance was similar regardless of whether we used continuous moisture sensitivity functions based on relative humidity or a simple binary function based on the presence of moisture, although a Gaussian temperature sensitivity outperformed a monotonically increasing Q10 temperature function. We demonstrate that explicitly modeling non-rainfall moisture and temperature together is necessary to accurately capture litter decay dynamics in a fog-affected dryland system and provide suggestions for how to incorporate non-rainfall moisture into existing Earth system models.

Leaf Litter Decomposition of Melocanna baccifera (Roxb.) Kurz under Field and Laboratory Microcosm in Northeast India

Melocanna baccifera (Roxb.) Kurz is one of the most abundant bamboo species of Mizoram, Northeast India contributing about Melocanna baccifera 95% of the total bamboo resources. This study was aimed to assess the rate of leaf litter decomposition of leaves in natural forest M. baccifera(FS) and laboratory microcosm (MC). A total of 36 litter bags measuring (15 x 15 cm, 2 mm mesh) containing 10g of air-dried litter material were placed in FS, and 36 litter bags of 10 x 10 cm filled with ~5 g of litter material were placed in the MC. MC was made from bottom sealed PVC pipe of 12 cm diameter and 16 cm height and filled with layers of 2/3 mineral soil and 1/3 with organic soil from the forest. A total of 6 litter bags were retrieved from FS and MC at monthly intervals for 6 months. Litter decay rate was higher in FS as compared to MC and litter mass remaining at the end of the study was 7 % and 13 % in FS and MC, respectively. Consequently, carbon (C) and nitrogen (N) mass remaining were 11.2% and 11.8% in MC and 7.3% and 5.6% in FS. Annual decay constant (k) was 2.2 and 1.4, respectively in FS and MC. Overall, mass loss rate and C and N release from litter was significantly higher in FS compared to MC indicating more complex synergistic effects of abiotic and M. baccifera biotic factors in decomposition at the FS site compared to MC site.

Net soil carbon balance in afforested peatlands and separating autotrophic and heterotrophic soil CO<sub>2</sub> effluxes

Abstract. Peatlands are a significant global carbon (C) store, which can be compromised by drainage and afforestation. Quantifying the rate of C loss from peat soils under forestry is challenging, as soil CO2 efflux includes both CO2 produced from heterotrophic peat decomposition and CO2 produced by tree roots and associated fungal networks (autotrophic respiration). We experimentally terminated autotrophic below-ground respiration in replicated forest plots by cutting through all living tree roots (trenching) and measured soil surface CO2 flux, litter input, litter decay rate, and soil temperature and moisture over 2 years. Decomposition of cut roots was measured and CO2 fluxes were corrected for this, which resulted in a large change in the fraction heterotrophic : autotrophic flux, suggesting that even 2 years after trenching decaying root biomass makes significant contributions to the CO2 flux. Annual peat decomposition (heterotrophic CO2 flux) was 115 ± 16 g C m−2 yr−1, representing ca. 40 % of total soil respiration. Decomposition of needle litter is accelerated in the presence of an active rhizosphere, indicating a priming effect by labile C inputs from roots. This suggests that our estimates of peat mineralization in our trenched plots are conservative and underestimate overall rates of peat C loss. Considering also input of litter from trees, our results indicate that the soils in these 30-year-old drained and afforested peatlands are a net sink for C, since substantially more C enters the soil organic matter than is decomposed heterotrophically. This study does not account for fluvial C fluxes, which represent a small flux compared to the CO2 soil efflux; further, root litter and exudate deposition could be a significant C source that is only partially sampled by our approach, adding to these plantations being a potential carbon sink. However, the C balance for these soils should be taken over the lifespan of the trees, in order to determine if the soils under these drained and afforested peatlands are a sustained sink of C or become a net source over longer periods of forestry.

Response of Annual Herbaceous Plant Leaching and Decomposition to Periodic Submergence in Mega-Reservoirs: Changes in Litter Nutrients and Soil Properties for Restoration.

Simple SummaryThis research focuses on the leaching and decomposition of riparian zone plants, which lose mass and release nutrients due to changing water levels during their vigorous growth period. While different factors greatly influence litter decomposition, the change in soil characteristics over various depths and their relationship to litter are largely unknown in mega-reservoir settings. Current research explores how annual plants decompose and release nutrients while they are submerged in soggy circumstances. Flooding circumstances can hasten plant mass loss and nutrient release, as well as change soil and water characteristics. This research found that sediment hindered the loss of mass and C, N, and P elements while stimulating the release of the K element. The litter decomposition of annual herbaceous plants has minimal impact on the overall amount of carbon and nutrients in the soil when the soil is saturated with water. This is linked to water leaching and soil element transformation. However, this does not imply that the significance of litter for soil nutrition is minor. It is essential to investigate the continuing production of residual soil litter nutrients after the water level has receded.Litter decomposition is an important soil nutrient source that promotes vegetation in deteriorated riparian zones worldwide. The periodic submergence and sediment burial effects on two prominent annual herbaceous plants (Echinochloa crusgali and Bidens tripartite) are little known in mega-reservoir settings. Our study focuses on the mass and carbon loss and nutrient release from E. crusgali and B. tripartitle litter and changes in soil properties, which are important for riparian zone rehabilitation in the Three Gorges Dam Reservoir, China. This study adopted the litter bag method to explore the nutrient change characteristics and changes in soil properties at different sediment burial depths under flooding scenarios. Three burial depths (0 cm, 5 cm, and 10 cm) were used for these two plants, and the experiment lasted for 180 days. The results revealed that the litter decay rate was high at first in the incubation experiment, and the nutrient loss rate followed the pattern of K > P > N > C. The relationship between % C remaining and % mass remaining was nearly 1:1, and the total amount of P exhibited a leaching–enrichment–release state in the decomposition process. Nutrients were changed significantly in the soil and overlying water at the first decomposition stage. Still, the total soil nutrient change was insignificant at the end, except for the 10 cm burial of B. tripartitle. Moreover, oxidation–reduction potential was the main factor in the litter decomposition process at different burial depths. This study indicated that sediment deposition reduced litter mass loss, slowed down the release of N and P, and retained more C, but promoted the release of K. Conclusively, in litter decomposition under waterlogging, the total soil nutrient content changed little. However, litter does more to the soil than that. Therefore, it is necessary to study the residual soil litter’s continuous output after the water level declines for restoration purposes.

Salinity exerted little effect on decomposition of emergent macrophytes in coastal peatlands

Climate-warming-driven sea level rise may change the vegetation composition of coastal wetlands, influencing ecosystem functions including photosynthetic activity, biomass production, litter decomposability and nutrient cycling. Litter decomposition rates of the most dominant macrophytes, Phragmites australis, Carex sp. and Schoenoplectus tabernaemontani, in two nearby freshwater and oligohaline peatlands were compared to determine the impact of salinity on litter decomposition. Electrical conductivity difference of 1.2–8.0 mS cm-1 (mean difference = 4.8 mS cm-1) between freshwater and oligohaline peatlands did not significantly affect the decomposition of macrophyte litter. Between species, S. tabernaemontani lost a significantly higher mass (29%) in the first month of decomposition compared to P. australis and Carex sp. Overall, litter decay rates for S. tabernaemontani was k = 0.0064–0.0078 d-1 while P. australis and Carex sp. both had k = 0.0017–0.0028 d-1. After one year, S. tabernaemontani litter was totally decomposed while the other species had 40–60% mass remaining relative to their initial dry mass confirming that P. australis and Carex sp. contribute to peat formation while S. tabernaemontani does not. Apparent differences in decomposition kinetics between S. tabernaemontani and the other species tested indicated that litter quality, especially C:P, C:N, N:P and C:Ca, is of great importance for both microbial colonization (initial phase) as well as for sustaining decomposition after colonization. This study shows that litter quality controls litter decomposition more than narrow salinity ranges. Hence, we suggest that sea level rise, combined with increased precipitation, may not have significant impact on the decomposition of these macrophytes in the future. However, sea level rise may lead to changes in vegetation composition replacing the peat-forming species by S. tabernaemontani which favors relatively deep, oligohaline wetlands. This would eventually affect carbon sequestration rates.

Decomposition of Leaf Litter from Native and Nonnative Woody Plants in Terrestrial and Aquatic Systems in the Eastern and Upper Midwestern U.S.A.

Leaf litter decomposition plays an important role in nutrient cycling in both terrestrial and aquatic systems. Decay rates vary based on species, habitat, climate, and local environmental conditions. Invasive plants alter decomposition processes; however, there is a lack of research exploring patterns at regional and continental scales. In this study we examined the decomposition of both native and nonnative, invasive woody plant leaf litter and mixtures of the two, in both terrestrial and aquatic habitats at nine locations in the eastern and midwestern U.S.A. There was significant variation among locations, which was not clearly related to either average air temperature or precipitation. Unexpectedly, in locations with multiple years of data, there were higher rates of decomposition in years with lower temperatures and precipitation in both terrestrial and aquatic habitats. We found decay rates were generally higher in aquatic than terrestrial habitats and leaf litter from nonnative invasive species generally decayed faster than that of native species in both terrestrial and aquatic systems. Differences in litter decay rates among invasive species were significant in both terrestrial and aquatic habitats; whereas no differences were found among native species in either habitat. In mixed litter bags, decay rates were lower than what was predicted based on the relative amounts of native and invasive litter in each bag, possibly indicating the presence of native leaf litter slows the decomposition of invasive leaf litter. Additionally, there may have been threshold effects in the mixed litter bags, especially in aquatic systems. While this study supported several generalizations about leaf decomposition rates (invasive > native, aquatic > terrestrial), the variability in the decay rates from different locations and habitats indicates combinations of different species and local conditions may overshadow other general trends related to litter decomposition.

Decomposition and temperature sensitivity of fine root and leaf litter of 43 mediterranean species

AimsData on the decomposition of fine roots are scarce for the Mediterranean basin. This work aims to compare chemical traits, decomposition rate, and temperature sensitivity (Q10) for root and leaf litter of 43 Mediterranean species.MethodsWe carried out a two-years litterbag decomposition experiment using 43 fine roots litter and leaf litter types incubated in laboratory conditions at three different temperatures, i.e. 4 °C, 14 °C, and 24 °C. Litter was characterized for carbon (C), nitrogen (N), lignin and cellulose concentration, C/N, and lignin/N ratios.ResultsFine root litter had lower N content but higher lignin concentration, lignin/N, and C/N ratios compared to leaf litter. The decay rate of fine root litter was slower than leaf litter. For both tissues, the decay rate was negatively associated with lignin concentration, lignin/N, and C/N ratios but positively with N concentration. Q10 was higher for fine root than leaf litter, with a positive correlation with lignin while negative with N concentration.ConclusionsOur findings demonstrate a higher Q10 accompanied by a slower decomposition rate of fine root litter compared to leaf litter in Mediterranean ecosystems. These results must be considered in modeling organic C at the ecosystem scale.