Decomposition Of Debris Research Articles

Assessment of soil fertility in jute (Corchorus olitorius L.) cultivated land and nutritive value of its plant parts

The samples of soil, leaves, and shoots of jute were collected from twenty spots of jute (variety BJRI-Tossa-8) fields from different locations in the Narail district of Bangladesh under AEZ-12 during the year 2022. The study intended to evaluate the soil’s physicochemical properties and nutrient concentrations in jute leaves and shoots of 120 days old plants (at the harvesting time of the plant). The soil pH was neutral to slightly alkaline (6.6 to 7.4), with organic matter content from 1.03 to 1.71%. Electrical conductivity was found non-saline which was 40 to 150 μS/cm at 0 to 15 cm depth. The dominant soil textural class was clay. The total N, P, and S in soils were found to be 0.21 to 0.31%, 0.027 to 0.0283% and 0.0002 to 0.0023%, respectively and available N, P, and S were found to be 0.0058 to 0.0087%, 0.0007 to 0.0018%, and 0.0001 to 0.0006%. The nutritional values of N, P, and S in leaves ranged from 3.00 to 11.75%, 0.2281 to 0.5627%, and 0.0056 to 0.0197%, respectively. The total N, P, and S concentrations in the shoots were 0.17 to 5.07%, 0.0012 to 0.2935%, and 0.0002 to 0.0011%, respectively. The study indicated that jute leaves are enriched in nutrition and may be a good source of nourishment for human health. This research also illustrated that the jute field had low to medium fertility soil status. It is suggested that the farmers of AEZ-12 should follow the fertilizer recommendation doses in jute cultivation for higher fiber yield and allow sufficient decomposition of jute roots and debris to sustain succeeding crop production and soil fertility. The study has given new information and guidelines for the researcher for future investigation. Biodivers. Conserv. Bioresour. Manag. 2024, 10(1): 35-44

Soil phosphorus continues to re‐equilibrate over 60 years of forest development in the Calhoun Critical Zone Observatory in the southeastern US Piedmont

AbstractLand use changes and reforestation impact soil phosphorus (P) distribution over extended periods. This study examines P distribution in forest development from 1957 to 2017 at the Calhoun Critical Zone Observatory in South Carolina. Tracking changes in 0–60 cm mineral soil P fractions through six samplings in eight continuously uncut plots and eight plots cut in 2007 (replanted in 2009), we hypothesized an increase in soil organic P (Po) over time in uncut plots, at the expense of HCl‐extractable P (i.e., Ca‐P). This hypothesis is based on the expectation of a transfer of P from easily accessible forms, possibly from historic fertilization to organic reservoirs within the soil. Meanwhile, we expect to lose Po in cut plots due to disturbance and residue decomposition, and increase bioavailable Mehlich‐III extractable P (Mehlich‐III P), resin inorganic phosphorus (Pi), and HCO3 Pi. Results revealed a continued decrease in Mehlich‐III P in uncut (38.7–15.7 µg g−1) and cut plots (25.2–17.7 µg g−1) within the 0–7.5 cm range. NaOH‐Po in uncut plots remained stable, while in cut plots, it increased by ∼4 µg g−1 in the 0–7.5 cm soil layer. Slowly cycling Po (NaOH‐Po) increased during forest regrowth in the cut plots, aligning with rising soil organic carbon and decreasing soil pH. Soil P changes indicate minor declines in available fractions during the initial three decades, with the HCl extractable (Ca‐P) fraction experiencing the highest depletion. In the later three decades, P associated with NaOH extraction (i.e., iron [Fe] and aluminum [Al] bound P) declined, although estimated mineral soil P removals during this period were less than accumulated P in tree biomass and forest floor. The total soil P decline from 1990 to 2017 was 34 kg ha−1, suggesting a growing role of P recycling from debris decomposition in supplying soil P to plants.

Phosphorus accumulation during the ice-on season in macrophyte-dominated eutrophic lakes and its implications

Macrophyte overgrowth in eutrophic lakes can hasten the decline of shallow water bodies, yet the impact of macrophyte deposition on sediment phosphorus (P) accumulation in the ice-on season remains unclear. Comparative analyses of P variations among 13 semi-connected sub-lakes in Wuliangsu Lake in China, a typical MDE lake, considered external flow and macrophyte decomposition as driving forces. Sediment P fractions and water total phosphorus (TP) were analyzed at 35 sampling points across three ice-on season stages, along with macrophyte TP content to assess debris contributions.Our findings reveal that phosphorus accumulation occurs during the ice-on season in the MDE lake, with an average TP content increase of 16 mg/kg. However, we observed a surprisingly small sediment nutrient accumulation ratio (ΔTP/ΔTN=0.006) compared to macrophyte nutrient levels before decomposition. Further analysis of the dominant species, Potamogeton pectinatus, indicates that a significant portion (55%) of macrophyte phosphorus is released before the ice-on season. This highlights the critical importance of timing macrophyte harvesting to precede the phosphorus leaching process, which has implications for lake management and ecosystem restoration efforts.Additionally, our research demonstrates similar transformations among different sediment fractions as previously reported. Macrophyte debris decomposition likely serves as the primary source of Residual P (Res-P) or TP accumulation. In addition, Ca-bound P (Ca–P) generally showed a decrease, which mainly caused by its transformation to Fe/Al-bound P (Fe/Al–P), Exchange-P (Ex-P), and sometimes to Res-P. However, we emphasize the significant impacts of flow dynamics on Ca–P transport and transformations. Its hydrodynamic action increases water dissolved oxygen, which accelerates the transformation of Ca–P to more easily released Fe/Al–P and Ex-P. Furthermore, hydrodynamic transport also leads to upstream Ca–P transport to downstream. This underscores the necessity of considering flow dynamics when estimating phosphorus variations and formulating phosphorus restoration strategies.

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

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

Biodegradable plastics fragments induce positive effects on the decomposition of soil organic matter

The escalating accumulation of plastic waste in ecosystems poses a significant health concern to soil environment, yet the environmental effects of plastics remains largely unexplored. Biodegradable plastics could offer a viable alternative to conventional persistent plastics, but our understanding of their potential benefits or detrimental effects on the decomposition of plant debris by soil biomass is limited. In this study, we conducted a year-long field experiment to examine the environmental response and impact on plant debris decomposition in the presence of varying quantities of persistent versus biodegradable plastics. Our findings indicate that the decomposition rate decreased by 2.8–4.9% for persistent plastics, while it increased by 1.3–4.2% for biodegradable plastics. Persistent plastics primarily induced adverse effects, including a reduction in soil nutrients, microbial diversity, bioturbation, enzyme activity, easily decomposable carbon, and microbial biomass carbon in plant debris. In contrast, biodegradable plastics resulted in beneficial effects such as an increase in enzyme activity, microbial biomass carbon, and easily decomposable carbon. We also observed that the decomposition rate of plant residues and nutrient release are closely associated with changes in the organic carbon chemical structure induced by different plastic film fragments. A significant shift in alkoxy carbon content facilitated the release of nutrients and soluble carbon, while modifications in carboxyl and aromatic carbon content hindered their release. Overall, our study reveals over one year that biodegradable plastics primarily induce positive effects on the decomposition of soil organic matter.

Short-Term Impact of Decomposing Crown-of-Thorn Starfish Blooms on Reef-Building Corals and Benthic Algae: A Laboratory Study

Outbreaks of crown-of-thorn starfish (COTS) have caused dramatic declines in reefs through predation on corals, but the post-bloom effects of COTS may still potentially threaten the environment and living organisms due to massive organic decomposition. This stimulation experiment showed that the decomposition of COTS debris triggered an extra mineralization process and resulted in acidifying, hypoxic, and eutrophic seawater. Consequently, the photosynthetic efficiency of coral symbionts decreased by 83%, and coral bleached after removing the stress within two days, then the coral skeleton dissolved at rates of 0.02–0.05 mg cm−2 day−1. Within two weeks, the photosynthesis and growth of benthic algae were suppressed by 27–86% and 1.5–16%, respectively. The mortality of turf algae and coralline algae indicated compromised primary productivity and limited coral recruitment, respectively. However, macroalgae, as coral competitors, became the only survivors, with increasing chlorophyll content. This study suggests a continuing decline of reefs during the collapse phase of COTS outbreaks and highlights the need for improving control strategies for the COTS population.

Review on the study of forest coarse woody debris decomposition

Review on the study of forest coarse woody debris decomposition

Fine root presence and increased phosphorus availability stimulate wood decay in a central Amazonian rainforest

In the Amazon basin, approximately 60% of rainforest thrives on geologically old and highly weathered soils, thus decomposition represents an important mechanism for recycling nutrients from organic matter. Although dead logs and branches constitute up to 14% of the carbon stored in terrestrial ecosystems, woody debris decomposition and mainly the effect of direct nutrient cycling by plant root interaction is poorly studied and often overlooked in ecosystem carbon and nutrient budgets. Here we monitored the decomposition of five different local woody species covering a range of wood density by conducting a long‐term wood decomposition experiment over two years with factorial root presence and phosphorous (P) addition treatments in a central Amazonian rainforest. We hypothesized that woody debris decomposition is accelerated by colonizing fine roots mining for nutrients, possibly strongly affecting wood debris with lower density and higher nutrient concentration (P). We found that root colonization and P addition separately increased wood decay rates, and although fine root colonization increased when P was added, this did not result in a change in wood decay. Nutrient loss from wood was accelerated by P addition, whereas a root presence effect on nutrient mobilization was only detectable at the end of the experiment. Our results highlight the role of fine roots in priming wood decay, although direct nutrient acquisition by plants seems to only occur in more advanced stages of decomposition. On the other hand, the positive effect of P addition may indicate that microbial nutrient mobilization in woody material is driven mainly by wood stoichiometry rather than priming by root activity.

Characterization of thermal decomposition mechanism and combustion performance of 4,4’‐azobis(1,2,4‐triazole)**

Abstract4,4’‐azobis(1,2,4‐triazole) (ATRZ), as a representative of high‐nitrogen compound, has attracted extensive interests. This work explores the thermal decomposition mechanism and combustion performance of ATRZ. The thermogravimetry‐differential scanning calorimetry‐fourier transform infrared spectroscopy (TG‐DSC‐FTIR) of ATRZ was carried out at heating rate of 10 °C/min in an argon atmosphere. ATRZ has two peak exothermic temperatures, 110.24 °C and 306.85 °C respectively. The exothermic peak at 110.24 °C is the decomposition of ATRZ tiny debris, and the exothermic peak at 306.85 °C is the decomposition of the main part of ATRZ. The pyrolysis‐gas chromatography mass spectrometry (PY‐GC/MS) of ATRZ was carried out at 350 °C in an argon atmosphere. By combining TG‐DSC‐FTIR and PY‐GC/MS, the thermal decomposition mechanism of ATRZ was speculated. The main reaction in the ATRZ pyrolysis process is the cleavage of two N−N single bonds in the nitrogen bridge, forming a nitrogen molecule and two triazole rings, which is the majority of the first step decomposition reaction. At the same time, a small number of triazole rings break off to form other intermediates. A small amount of nitrogen gas is generated and a large number of CN clusters are formed. Under the same testing conditions, ATRZ has a higher combustion heat (19318 J/g) than other traditional CHNO energetic materials. By comparing the laser ignition combustion of ATRZ and ATRZ+RDX, the combustion temperature of ATRZ+RDX is higher and the combustion duration is longer. The introduction of CHNO type ammonium nitrate explosives promotes the energy release of ATRZ.

Determination of no observable effect level of nanoplastics on intestinal flora

The risk of human exposure to nanoplastics (NPs) is increasing due to the incomplete decomposition and accumulation of plastic debris in the environment. Dietary intake is the most common way for human body to ingest NPs. NPs cannot degrade in vivo and will accumulate in multiple tissues, which result in various tissue damages. Although numerous studies have focused on evaluating the influences of exposure to NPs, the exposure amounts investigated were much higher than the actual exposure level in human daily life. Therefore, it is necessary to evaluate the hazards of exposure to low-dose NPs. Intestinal flora is a generally recognized sensitive indicator for NPs exposure, so determining a safe threshold to intestinal flora can represent the maximal no-effective dose for the human body of NPs exposure. Based on these information, mice were exposed to NPs at concentrations of 0, 0.001, 0.005, 0.01 and 0.1 mg kg−1·BW, respectively. The composition changes of the intestinal flora were investigated after exposing 28 days. The obtained consequences indicated that 0.01 mg kg−1·BW was the maximal no-effective dose to intestinal flora. This study provided a clear safe threshold for investigating the potential adverse effects of low-dose NPs exposures on human health.

Hydrophyte Debris Induced Sedimentary Phosphorus Release in Tuojiang Rivers, China.

Hydrophyte debris decomposition may contribute to phosphorus (P) release from the sediments in riverine systems, but the transport and transformation of organic phosphorus during this process has not been studied well. Here, a ubiquitous hydrophyte in southern China (Alternanthera philoxeroides, A. philoxeroides) was selected to identify the processes and mechanisms of sedimentary P release in late autumn or early spring by laboratory incubation. The results showed that the physio-chemical interactions changed quickly during the beginning of the incubation, where the redox potential and dissolved oxygen at the water-sediment interface decreased rapidly, reaching reducing (299 mV) and anoxic (0.23mg∙L-1) conditions, respectively. Soluble reactive P, dissolved total P and total P concentrations in overlying water all increased with time from 0.011, 0.025 and 0.169mg∙L-1 to 0.100, 0.100 and 0.342mg∙L-1 on average, respectively. Furthermore, the decomposition of A. philoxeroides induced sedimentary organic P release to overlying water, including phosphate monoester (Mono-P), and orthophosphate diesters (Diesters-P). The proportions of Mono-P and Diesters-P were higher at 3 to 9 days than at 11 to 34 days, being 29.4% and 23.3 for Mono-P, 6.3% and 5.7% for Diesters-P, respectively. Orthophosphate (Ortho-P) increased from 63.6 to 69.7% during these timeframes, which indicated the transformations of both Mono-P and Diester-P to bio-available orthophosphate (Ortho-P), causing the rising P concentration in the overlying water. Our results revealed that hydrophyte debris decomposition in river systems might lead to autochthonous P contribution even without external P import from the watershed, accelerating the trophic state of receiving waterbodies.

Metabolic insights into the interaction between nitrogen removal and 4–chlorophenol reduction of anammox consortia

The response characteristic and performance stabilization of anammox process under the stress of the potential organic pollutants support the application of ammonia–nitrogen wastewater treatment. In the present study, nitrogen removal performance was significantly suppressed with the addition of 4–chlorophenol. The activity of anammox process was inhibited by 14.23% (0.1 mg/L), 20.54% (1 mg/L) and 78.15% (10 mg/L), respectively. Metagenomic analysis revealed a significant decrease in the abundance of KEGG pathways associated with carbohydrate and amino acid metabolism with increasing 4–chlorophenol concentration. Metabolic pathway profiles suggest that putrescine is down–regulated at high 4–chlorophenol stress due to inhibition of nitrogen metabolism processes, while it is up–regulated to reduce oxidative damage. In addition, the presence of 4–chlorophenol induced an enhancement of EPS and bacterial debris decomposition, and a partial conversion of 4–chlorophenol to p–nitrophenol. This study unravels the mechanism of effect on anammox consortia in response to 4–CP, which could provide supplementary to facilitate its full-scale application.

Effect of plant-self debris on nitrogen removal, transformation and microbial community in mesocosm constructed wetlands planted with Myriophyllum aquaticum

Aquatic macrophytes debris decomposition could release pollutants and nutrients into the water of constructed wetlands (CWs), but their role in nitrogen removal and transformation remains poorly understood. The present study investigated the effects of plant-self debris on nitrogen removal and microbial communities in mesocosm CWs planted with Myriophyllum aquaticum. During the 68-day operation, the plant debris addition did not change the mean removal efficiency of ammonium (NH4+-N) and total nitrogen (TN) of CWs but showed significant differences over the operation time. The NH4+-N and organic nitrogen released from the plant debris decomposition affected the nitrogen removal. The plant debris decreased the effluent nitrate concentration and N2O emission fluxes of the CWs with the increased abundance of denitrifying bacterial genera, indicating that plant debris decomposition increased the denitrification activities via dissolved organic carbon release. High-throughput sequencing indicated that the plant debris altered the distribution and composition of the microbial community in the sediments. Proteobacteria was the dominant phylum (28–52%), and the relative abundance of denitrifying bacteria genera was significantly higher in the sediments with debris addition (37–40%) than in the non-addition (6.6–7.7%). The present study provided new insights into the role of macrophytes in pollutant removal and the plant management strategy of CWs.

Towards More Efficient EfficientDets and Real-Time Marine Debris Detection

Marine debris is a problem both for the health of marine environments and for the human health since tiny pieces of plastic called "microplastics" resulting from the debris decomposition over the time are entering the food chain at any levels. For marine debris detection and removal, autonomous underwater vehicles (AUVs) are a potential solution. In this letter, we focus on the efficiency of AUV vision for real-time and low-light object detection. First, we improved the efficiency of a class of state-of-the-art object detectors, namely EfficientDets, by 1.5% AP on D0, 2.6% AP on D1, 1.2% AP on D2 and 1.3% AP on D3 without increasing the GPU latency. Subsequently, we created and made publicly available a dataset for the detection of in-water plastic bags and bottles and trained our improved EfficientDets on this and another dataset for marine debris detection. Finally, we investigated how the detector performance is affected by low-light conditions and compared two low-light underwater image enhancement strategies both in terms of accuracy and latency. Source code and dataset are publicly available.

Medical and Economical Significance of Millipedes

Abstract Millipedes as saprophagous epigeic fauna members are involved in the decomposition of organic debris. Diplopod’s activity improve circulation of nutrients, elements and accelerate environmental reclamation. Beyond mentioned above Diplopoda can provoke sanitary and epidemiological threats especially during swarming or seasonal migrations activities. Considering following aspects: contact with defensive secretions, pseudo-parasitic activity that imitates helminthiasis or passive transmission of pathogens, we can discuss direct or distant effects on human health. Education and proper prophylactic remain neglected. Variety of substances from millipedes are checked for their medical action: direct body extracts and active chemical components from defensive secretion. Millipedes may serve as source for zoo-pharmacology and zoo-indication development. This issue review shows that both pros and cons of the Diplopod’s influences should be considered. Literature was carried out from middle of 20th century article till recent papers. The nowadays literature were found in Google Scholar, PubMed, Medline search base.

Санитарное состояние коренных ельников тайги Европейской России

The materials of studies carried out in the primary uneven-aged spruce forests of the taiga within European Russia are presented, in the northern taiga spruce forests are studied in the territories of the Arkhangelsk region and the Paanajarvi National Park in the Karelia Republic; in the middle taiga spruce forests are studied in the reserve «Vepssky forest» in the Leningrad region and Andomsky forestry of the Vologda region; in the southern taiga spruce forests of the Central Forest State Biosphere Reserve in the Tver Region are studied. The age and volume of trees growing on permanent test plots were determined, age series of forest stands were modelled, dynamic characteristics were established, estimates of the sanitary condition of trees and stands were made, the infestation of the biotrophic complex with wood-destroying fungi and calculations of the tree waste volume by stages of decomposition were made. A close relationship between the increase in tree damage values and the increase in the age of generations in the age series was revealed, which is interpreted as a pattern: r = 0,98 with mr = 0,05 and t = 140. The dynamics of the formation of age generations in spruce forest stands proceeds much more slowly from 4 to 6 times than the dynamics of wood debris decomposition. The characteristics of the sanitary state of native spruce stands are in the range between weakened and severely weakened communities, with high rates of rotten faults of trees in age generations and stands and significant amounts of tree waste. High rates of rot damage to trees ensure the balance of reproducible and degradable biomass in the dynamics of spruce forests. This balance is formed by differences in the time periods of biomass accumulation and the rate of decomposition of wood waste.

Vibrational spectroscopy, X-ray diffraction and EDS applied to reveal the fossilization pathways of fossil shells from the Jandaíra Formation, Upper Cretaceous Northeast Brazil

The Jandaíra Formation, Potiguar Basin, is well known for hosting a rich marine fauna from the Late Cretaceous of Brazil. Among the organisms that compose this diverse fossiliferous assemblage, the gastropods stand out for their abundance of individuals. In this study, four samples of Tylostoma sp (LP/UFC CRT 2868, LP/UFC CRT 2869, LP/UFC CRT 2870 and LP/UFC CRT 2871) were analyzed in order to understand the different diagenetic processes involved in their preservation. The fossil specimens were collected near Mossoró, state of Rio Grande do Norte. In this work, we have combined a set of high-resolution techniques such as Raman spectroscopy, X-ray diffraction (XRD), Fourier-transform infrared (FTIR) and Scanning Electron Microscopy (SEM) and energy dispersive spectroscopy (EDS) to characterize the fossil specimens mineralogically. All fossil shells are preserved as internal molds, meaning they have lost their original organic matter. After the decomposition of organic debris, the inner part of the shell is filled with surrounding sediment. Our results revealed dolomite as the dominant phase in host rock. On the contrary, the fossil samples LP/UFC CRT 2868, LP/UFC CRT 2869, LP/UFC CRT 2870 and LP/UFC CRT 2871 showed calcite as the dominant phase. These data indicate that a similar diagenetic process was involved in the preservation of these fossil shells. Here, we document discoveries and new perspectives for looking at the abundance of fossil shells in the Jandaíra Formation.

Do experimental pH increases alter the structure and function of a lowland tropical stream?

AbstractDisturbances can alter the structure and function of ecosystems. In stream ecosystems, changes in discharge and physicochemistry at short, intermediate, and long recurrence intervals can affect food webs and ecosystem processes. In this paper, we compare pH regimes in streams at La Selva Biological Station, Costa Rica, where episodic acidification frequency across the stream network varies widely due to buffering from inputs of bicarbonate‐rich interbasin groundwater. To examine the effects of acidification on ecosystem structure and function, we experimentally increased the buffering capacity of a headwater stream reach and compared it to an unbuffered upstream reach. We compared these reaches to a naturally buffered and unbuffered reaches of a second headwater stream. We quantified ecosystem structural (macroinvertebrate assemblages on leaf litter and coarse woody debris) and functional responses (leaf litter and coarse woody debris decomposition rates, and growth rates of a focal insect taxon [Diptera: Chironomidae]). Non‐metric multidimensional scaling and analysis of similarity revealed that macroinvertebrate assemblages were relatively homogenous across the four study reaches, although the naturally buffered reach was the most dissimilar. Ecosystem function, as measured by chironomid growth rates, was greater in the naturally buffered reach, while decomposition rates did not differ across the four reaches. Our results indicate that biological assemblages are adapted to pH regimes of frequently acidified stream reaches. Our experiment informs the effects on structure and function at short time scales in streams that experience moderate acidification, but larger magnitude acidification events in response to hydroclimatic change, as projected under climate change scenarios, may induce stronger responses in streams.

Seasonal and Longitudinal Variations in Suspended Load Connectivity Between River Channels and Their Margins

AbstractInput of organic matter into stream channels is the primary energy source for headwater ecosystems and ultimately carbon to the oceans and hence is an important component of the global carbon cycle. Here, we quantify organic‐rich fine sediment mobilization, transport, and storage in a Strahler fourth‐order stream during individual intermediate‐sized storm events. By combining measurements of fallout radionuclides (FRNs) 7Be and 210Pb and stable water isotopes with a conceptual model of suspended load trapping by channel margins, we find that the channel bed was consistently a source of suspended load to the channel margins. Relative to storage on the channel margins, suspended load export increased through the spring and summer, perhaps related to the in‐channel decomposition of organic debris as indicated by its FRN exposure age and changing bulk δ13C composition. Trapping of suspended load by riparian margins limits sediment transport distances, which, given sufficient discharge to fully suspend the load, is nearly independent of stream discharge for sub‐bankfull discharges. Limited data indicate that the fractional size of the channel margins where trapping occurs decreases with increasing watershed area. Increasing transport length and decreasing fractional margin area with increasing watershed area results in a systematic downstream decoupling of the channel from local terrestrial organic matter exchange. These findings provide a framework for understanding suspended load dynamics in formerly glaciated regions where sediment production and fluxes are generally low and thus the annual input of organic debris is a major component of suspended load budget.

Predominant climate control on green leaf decomposition across subtropical rain and dry forests following hurricane disturbances

Hurricanes defoliate canopy and break tree branches and stems, generating large amount of plant debris in forest ecosystems. Forest recovery after hurricane disturbances relies heavily on the decomposition of these plant debris. Here we addressed the “tropical hierarchy of factors” hypothesis that substrate quality replaces climate as the predominant control on plant litter decomposition in tropical forests. We compared leaf decomposition between subtropical rain and dry forests on the island of Puerto Rico by reciprocally transplanting green-leaf litter between rain (Eugenia borinquensis leaves with higher C/N) and dry (Bucida buceras leaves with lower C/N) forests following hurricanes Irma and Maria. We show that leaf decomposed substantially faster in subtropical rain than dry forests, and for high-than low-quality substrates. Over a period of 536 days of field incubation, loss of leaf ash-free dry mass was 51.8% for B. buceras and 26.6% for E. borinquensis in the rainforest, 15.7% for B. buceras and near zero for E. borinquensis in the dry forest. We also found that soil arthropod density was more than 10-folds greater in the rainforest than in the dry forest and was only more than 2-folds greater in the low C/N litterbags than the high C/N litterbags. Analyses of structural equation model revealed that leaf decomposition rate correlated positively with total arthropod abundance in the rainforest and only with Oribatida abundance in the dry forest. The number of effective linkages among leaf C/N, precipitation and arthropods was greater in the subtropical rainforest (19) than in the dry forest (4), but did not vary between B. buceras (12) and E. borinquensis (11) substrates in the rainforest. We conclude that climate, rather than substrate quality, remains to be the predominant control on leaf decomposition across subtropical rain and dry forests following hurricane disturbances, and the controls of substrate quality on leaf decomposition is inferior and climate dependent.