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The degradation of vegetation in the watershed and associated release of dissolved organic matter (DOM) and particulate organic matter (POM) can influence the water quality of new reservoirs. This study aimed to evaluate whether water velocity influences the degradation of twigs of different diameters that remain in the watershed of new reservoirs. The results of twigs degradation under flowing and stagnant water over time were fitted to a double exponential decay kinetic model, which presents the detritus as labile/soluble and refractory compounds. The model parameterization showed that labile fractions presented higher decomposition rates (KT) in flowing than, but there was not a clear trend in the comparison between the diameters in each water condition. On the contrary, the refractory fraction decomposition rates (kR) showed a clear pattern in all comparisons, showing higher values in flowing water and for thin twigs. These results showed that thinner twigs decompose more rapidly, due to the greater A:V ratio, and that the abrasive effect of water velocity promotes faster decomposition. In general, we observed that there was a pattern of increasing decomposition rates as the twigs decrease in diameter (9–10 mm < 5–6 mm < 2–3 mm) and from stagnant water to flowing water. [ABSTRACT FROM AUTHOR]

From soil to freshwater ecosystems, decomposition can be conceived as the result of interactions between organic matter and a diversity of organisms. This function is driven in part by detritivores, invertebrates that feed on detritus or graze on its associated microbes and that have a significant but extremely variable contribution to decomposition.In order to better understand and predict detritivore–detritus pairwise interactions, we propose a conceptual framework, called Detri2match, to study the consumption of detritus by detritivores, using a trait‐matching approach at the individual detritivore level. Here, we focus on the interaction between saprophagous detritivores that fragment plant detritus.We propose a novel definition of a saprophagous detritivore as an animal that consumes plant detritus when its traits match sufficiently the traits of its resource, passing through five interaction facets of consumption. These include (1) a spatial match rule regarding the encounter, (2) a biomechanical match rule regarding ingestion, (3) a digestive match rule regarding assimilation, (4) an energetic match rule regarding the fulfilment of metabolic needs and (5) a nutritional match rule regarding the fulfilment of chemical element needs in adapted proportions.The main goal of this framework is to guide future research to establish generic rules of misunderstood detritus–detritivore pairwise interactions by identifying relevant interaction facets and their key associated traits for both detritivores and detritus. This investigation should be conducted over the temporal variability of trait‐matching constraints throughout the whole decomposition process. Coupled with adequate accumulation of trait information, the Detri2match framework could also facilitate predictions by inference of non‐tested pairwise detritivore–litter interactions.We also outline conceptual, methodological and analytical challenges of this framework. The main challenge would be to scale up these pairwise rules at the detrital network level and to test their genericity, which would contribute to a better understanding of the functioning of the detrital network and its contribution to decomposition. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Riparian forests provide abundant plant litter – mostly in the form of dead leaves (hereafter litter) – for both forest soils and adjacent stream ecosystems, supporting terrestrial and aquatic detritus‐based food webs. Although the fate of litter is predominantly dependent on its chemical and physical traits, there is limited availability of data on those traits over large spatial scales or empirical comparisons of traits across tropical biomes. We filled this gap by exploring the differences and similarities of nine litter traits and their dependence on phylogenetics for 68 plant species from riparian forests across three continental‐scale, South American biomes: Amazon, Atlantic Forest and Cerrado. All three biomes produced litter with similar percentages of carbon (C) and phosphorus (P), C:P mass ratios, specific leaf area and toughness. However, litter from the driest biome (Cerrado) was better defended chemically (higher phenolic content) and had lower nutritional quality (higher C:nitrogen [N] mass ratio) but showed lower nutritional limitation (lower N:P mass ratio) than litter from more humid biomes. We found no phylogenetic signal for traits after constructing a phylogenetic tree across all biomes, suggesting that trait differences across biomes were environmentally determined. However, a strong phylogenetic signal was observed for P in the Atlantic Forest, which indicates that closely related species have similar %P in that biome. Our findings suggest that litter from more humid biomes was higher in nitrogen, although more phosphorus‐limited, than litter produced in drier climates such as that of the Cerrado biome. [ABSTRACT FROM AUTHOR]

Plants of riparian forests provide abundant dead leaves for freshwater stream ecosystems which support detritus-based food webs. The increased replacement from natural riparian forests to Eucalyptus plantations, an exotic species distributed throughout the neotropic landscapes, alters leaf breakdown as a key ecosystem process. We evaluate the breakdown of native and exotic leaf species with distinct physical and chemical characteristics (traits) in two different tropical reference condition streams located in Cerrado and Atlantic Forest biomes. We tested the hypothesis that regardless of the leaves' origin (native or non-native species), leaf litter with higher nutrients and less recalcitrant compounds has higher decay rates. Eucalyptus camaldulensis leaf breakdown was faster than the native species Miconia chartacea in both streams. Leaf breakdown was driven by local characteristics (context dependent) and the macrodecomposer community, with more intensity to the litter's intrinsic physical and chemical quality. The higher leaf breakdown of E. camaldulensis was evidenced in the Atlantic Forest stream, that with the most increased water flow, further accelerating the leaf breakdown. Our findings indicate that due to the innate physical and chemical characteristics of E. camaldulensis , its decomposition occurs at a faster rate compared to native tropical species, as evidenced by the stream flows. [ABSTRACT FROM AUTHOR]

Global changes can alter plant inputs from both above‐ and belowground, which, thus, may differently affect soil carbon and microbial communities. However, the general patterns of how plant input changes affect them in forests remain unclear. By conducting a meta‐analysis of 3193 observations from 166 experiments worldwide, we found that alterations in aboveground litter and/or root inputs had profound effects on soil carbon and microbial communities in forest ecosystems. Litter addition stimulated soil organic carbon (SOC) pools and microbial biomass, whereas removal of litter, roots or both (no inputs) decreased them. The increased SOC under litter addition suggested that aboveground litter inputs benefit SOC sequestration despite accelerated decomposition. Unlike root removal, litter alterations and no inputs altered particulate organic carbon, whereas all detrital treatments did not significantly change mineral‐associated organic carbon. In addition, detrital treatments contrastingly altered soil microbial community, with litter addition or removal shifting it toward fungi, whereas root removal shifting it toward bacteria. Furthermore, the responses of soil carbon and microbial biomass to litter alterations positively correlated with litter input rate and total litter input, suggesting that litter input quantity is a critical controller of belowground processes. Taken together, these findings provide critical insights into understanding how altered plant productivity and allocation affects soil carbon cycling, microbial communities and functioning of forest ecosystems under global changes. Future studies can take full advantage of the existing plant detritus experiments and should focus on the relative roles of litter and roots in forming SOC and its fractions. [ABSTRACT FROM AUTHOR]

Background and aims: Understanding the effects of livestock grazing on the ecosystem biomass and soil nitrogen processes of grassland ecosystems is critical to improving knowledge on the mechanisms underlying grassland degradation and accurately assessing the influence of grazing management on grassland functions. Methods: We examined the interannual patterns of ecosystem biomass and soil nitrogen mineralization in response to cattle grazing in a Chinese meadow steppe. The soil core incubation method was employed for soil N transfer estimation, whilst the fumigation extraction method, a modified Baermann funnel method and harvest method were used for various measurements of ecosystem biomass parameters. Results: We found that cattle grazing caused consistent significant increases in soil temperature, irrespective of the stocking rate and year, whereas significant effects on soil moisture and edaphic properties were observed only in individual years and/or at specific stocking rates. Consistent positive effects at moderate stocking rates were observed for aboveground net primary production and soil nematode biomass in all study years. The across stocking rate pattern of N mineralization in response to cattle stocking appeared to be year-specific, although negative effects were found in most cases. In contrast, the interannual pattern of N mineralization was determined principally by the interannual patterns in precipitation and soil moisture and was much less affected by cattle grazing. Conclusions: Soil N mineralization in this meadow steppe was affected by cattle grazing via two major mechanisms, i.e., its effects on the aboveground net primary production (ANPP) and thus the quantity of plant litter input into the soil and its effects on soil temperature and moisture. Overall, our study spanned the longest consecutive years with the broadest range of stocking rates thus far of its kind, which revealed for the first time that the soil nitrogen mineralization pattern with respect to stocking rate was year-specific. Our findings have important implications for adaptive management and sustainable utilization of Chinese grasslands. [ABSTRACT FROM AUTHOR]

Ectomycorrhizal (EcM) and saprotrophic fungi interact in the breakdown of organic matter, but the mechanisms underlying the EcM role on organic matter decomposition are not totally clear. We hypothesized that the ecological relations between EcM and saprotroph fungi are modulated by resources availability and accessibility, determining decomposition rates. We manipulated the amount of leaf litter inputs (No-Litter, Control Litter, Doubled Litter) on Trenched (root exclusion) and Non-Trenched plots (with roots) in a temperate deciduous forest of EcM-associated trees. Resultant shifts in soil fungal communities were determined by phospholipid fatty acids and DNA sequencing after 3 years, and CO2 fluxes were measured throughout this period. Different levels of leaf litter inputs generated a gradient of organic substrate availability and accessibility, altering the composition and ecological relations between EcM and saprotroph fungal communities. EcM fungi dominated at low levels of fresh organic substrates and lower organic matter quality, where short-distances exploration types seem to be better competitors, whereas saprotrophs and longer exploration types of EcM fungi tended to dominate at high levels of leaf litter inputs, where labile organic substrates were easily accessible. We were, however, not able to detect unequivocal signs of competition between these fungal groups for common resources. These results point to the relevance of substrate quality and availability as key factors determining the role of EcM and saprotroph fungi on litter and soil organic matter decay and represent a path forward on the capacity of organic matter decomposition of different exploration types of EcM fungi.

Ectomycorrhizal (EcM) and saprotrophic fungi interact in the breakdown of organic matter, but the mechanisms underlying the EcM role on organic matter decomposition are not totally clear. We hypothesized that the ecological relations between EcM and saprotroph fungi are modulated by resources availability and accessibility, determining decomposition rates. We manipulated the amount of leaf litter inputs (No-Litter, Control Litter, Doubled Litter) on Trenched (root exclusion) and Non-Trenched plots (with roots) in a temperate deciduous forest of EcM-associated trees. Resultant shifts in soil fungal communities were determined by phospholipid fatty acids and DNA sequencing after 3 years, and CO2 fluxes were measured throughout this period. Different levels of leaf litter inputs generated a gradient of organic substrate availability and accessibility, altering the composition and ecological relations between EcM and saprotroph fungal communities. EcM fungi dominated at low levels of fresh organic substrates and lower organic matter quality, where short-distances exploration types seem to be better competitors, whereas saprotrophs and longer exploration types of EcM fungi tended to dominate at high levels of leaf litter inputs, where labile organic substrates were easily accessible. We were, however, not able to detect unequivocal signs of competition between these fungal groups for common resources. These results point to the relevance of substrate quality and availability as key factors determining the role of EcM and saprotroph fungi on litter and soil organic matter decay and represent a path forward on the capacity of organic matter decomposition of different exploration types of EcM fungi. [ABSTRACT FROM AUTHOR]

Nitrogen (N) removal efficiency through denitrification is usually not ideal and stable in biofilter systems due to the deficiency of organic carbon supply and difficulty of formation of anaerobic status, which could be enhanced by regulating the inflow carbon/nitrogen ratio (C/N), outflow water level, retention time, and addition of plant detritus through the pilot-scale stormwater biofilter study. Removal efficiency of ammonium (NH4+-N), soluble reactive phosphorus (SRP), and total phosphorus (34–90%) was significantly higher than that of nitrate (NO3−-N), dissolved total nitrogen (DTN), and total nitrogen (TN) (9–25%) in the biofilter systems. The addition of plant detritus (especially herbaceous plant) in biofilter systems can enhance the nitrogen (N) and phosphorus (P) removal efficiency by >24%. Through further regulation of inflow C/N, retention time, and outflow water level to promote denitrification, removal efficiency of NO3−-N, DTN, and TN was significantly enhanced and reached up to 83%, 68%, and 73% on average, respectively. However, P leaching increased due to SRP release from iron-bound P caused by anoxia. In the overall consideration of N and P removal, optimized inflow C/N, retention time, and outflow water level are estimated as 10–30, 1–2 h, and 20–40 cm, respectively, which makes a crucial contribution to simultaneous N and P removal. [ABSTRACT FROM AUTHOR]

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Stromwater biofilter technology was greatly improved through adding iron-rich soil, plant detritus and eutrophic lake sediment. Significant ammonium and phosphate removal efficiencies (over 95%) in treatments with iron-rich soil were attributed to strong adsorption capability resulting in high available phosphorus (P) in media, supporting the abundance and activity of nitrifiers and denitrifiers as well as shaping compositions, which facilitated nitrogen (N) removal. Aquatic and terrestrial plant detritus was more beneficial to nitrification and denitrification by stimulating the abundance and activity of nitrifiers and denitrifiers respectively, which increased total nitrogen (TN) removal efficiencies by 17.6% and 22.5%. In addition, bioaugmentation of nitrifiers and denitrifiers from eutrophic sediment was helpful to nutrient removal. Above all, combined application of these materials could reach simultaneously maximum effects (removal efficiencies of P, ammonium and TN were 97–99%, 95–97% and 60–63% respectively), suggesting reasonable selection of materials has important contribution and application prospect in stormwater biofilters. [ABSTRACT FROM AUTHOR]

The formation of man-made reservoirs generates several impacts on water quality. In order to minimize some of these impacts mathematical models are currently used. This paper aims to discuss the issue associated with the degradation of plant resources (leaves, branches, barks and litter) that remain within the watershed of the new man-made lakes and parameterize a kinetic model related to decay of plant detritus. In these environments, the short-term variation of limnological parameters is mainly connected with biomass decay drowned during the filling operation. The kinetics of the degradation processes in reservoirs are discussed on the basis of information with related to detritus sources and the chemical properties of different types of compounds (i.e. labile and refractory fractions). Overall, the parameterization of the (first order) kinetic model showed that refractory fractions (ca. 86%) are predominant and the mineralization is a slow process, constituting the main route for decomposition and being affected by changes of environmental variables. The mineralization of labile and hydrosoluble compounds (ca. 14%) is responsible for the short-term water quality variation owing to decomposition; basically, the intensities of these changes depend on the labile/soluble compounds content of detritus and its chemical composition. [Copyright &y& Elsevier]

Seasonal changes in the concentration of nutrients and various organic compounds were studied in the waters surrounding mangroves and in the marshy areas of mangroves. Higher amounts of nutrients and organic compounds were observed during low tide. This is due to the remineralisation of plant detritus in this area. High concentration of carbohydrates, proteins, chlorophyll and phosphate were observed during monsoon, which can be attributed to the leaching of plant detritus as well as the land run-off. During pre-monsoon and post-monsoon high tannin and lignin concentration was noted. A 24-hour sampling was also done to study the tidal impact on the concentrations of various organic compounds and nutrients in this ecosystem. Even though a tidal impact was observed, a clear picture was not reported in this study. [ABSTRACT FROM AUTHOR]

Salt marshes are well-known sinks of carbon and nitrogen, incorporating them both into sediment and in the halophyte biomass, being key players in the estuarine biogeochemical cycles. Due to aboveground senescence there will inevitably occur losses of C and N rich detritus, becoming prone to the tidal flooding and hydrodynamic regime. On the other hand, the ongoing climate change effects, such as sea level rise (SLR) are known to have influence in the estuarine circulation. The Ria de Aveiro is a mesotidal lagoon located in the Northwestern Portuguese coast, presenting a very complex geometry and characterized by large areas of salt marshes and tidal flats distributed along a web of narrow channels. Residual circulation, tidal asymmetry, tidal dissipation and detritus Lagrangian trajectories were determined from numerical modelling results of the MOHID 2D model that was applied to each coastal system, considering the actual sea level and a sea level rise (SLR) scenario. The results here discussed show that in the case of Ria de Aveiro, the examined salt marsh exports about 15 kg C m-2 y-1 and 2 kg N m-2 y-1. Nowadays, Barra salt marsh presents the highest values of residual circulation, but predictions point out to its reduction due to SLR scenario. Barra salt marsh shows highly dynamic conditions by being exposed to higher current velocities, increased erosion rates and longer and more frequent inundation periods. This way, model results of Lagrangian particles indicate that the detrital particles are highly dispersed, with large amounts approaching the outer area of the lagoon, a feature that is highly enhanced in the SLR scenario. These features may have two major implications: (1) enhance the fuelling of secondary production in the coastal shelf and (2) excessive N exports and possible eutrophication of the coastal area. These two consequences (positive and negative) acquire even more importance if all the marsh extension along all the Ria de Aveiro is considered along with its elevated amount of plant-generated detritus. Regarding the present predictions and concerns on estuarine ecology in a global change framework, it becomes important to consider these estuarine salt marshes not only as possible nutrient sinks, but also as a potential N source enhanced by the ongoing climate changes. [ABSTRACT FROM AUTHOR]