Decomposition Of Cotton Strips Research Articles

Multiple stressors unpredictably affect primary producers and decomposition in a model freshwater ecosystem

Freshwater ecosystems are affected by various stressors, such as contamination and exotic species, making them amongst the most imperilled biological systems on the planet. In Australia and elsewhere, copper is one of the most common metal contaminants in freshwater systems and the European carp (Cyprinus carpio L.) is one of the most pervasive and widespread invasive fish species. Copper (Cu) and carp can both directly affect primary production and decomposition, which are critical and interrelated nutrient cycling processes and ecosystem services. The aim of this study was to explore the direct and indirect effects of Cu and carp individually, and together on periphyton cover, chlorophyll a concentration, growth of the macrophyte Vallisneria spiralis L., and the decomposition of leaf litter and cotton strips in a controlled, factorial experiment in outdoor experimental ponds. In isolation, Cu reduced macrophyte growth and organic matter decomposition, while chlorophyll a concentrations and periphyton cover remained unchanged, possibly due to the Low-Cu concentrations in the overlying water. Carp addition alone had a direct negative effect on the biomass of aquatic plants outside protective cages, but also increased plant biomass inside the cages, periphyton cover and chlorophyll a concentrations. Leaf litter was more decomposed in the carp only ponds compared to controls, while there was no significant effect on cotton strip decomposition. Aquatic plants were absent in the Cu + carp ponds caused by the combined effects of Cu toxicity, carp disturbance and the increase in turbidity due to carp bioturbation. Increases in periphyton cover in Low-Cu + carp, while absence in the High-Cu + carp ponds, and differences in the decomposition of surface and buried cotton strips were not as predicted, which highlights the need for such studies to understand the complex interactions among stressors for environmental risk assessment.

Anthropogenic land uses influence stream dissolved organic matter quality more than decomposition rates and macroinvertebrate diversity

In the era of the Anthropocene, streams and rivers are among the most heavily impacted ecosystems due to the influence of catchment land use on stream water quality and ecological condition. In practice, structural and functional indicators collected by biomonitoring programs are underused and thus limited in their ability to offer practical insight into functional-based restoration approaches. Here we applied a novel combination of indicators—cotton strip decomposition, benthic invertebrate sampling together with dissolved organic matter (DOM) composition — to determine if streams highly impacted by urbanized and agricultural land use across Windsor-Essex (southwestern Ontario, Canada) were consistent across season, anthropogenic land use or some combination of both. Overall, our results suggest that urbanized and agricultural streams are indeed degraded at a similar level, with high decomposition rates and low levels of macroinvertebrate diversity. Moreover, DOM quality proved to be the most predictable indicator spatially and seasonally, integrating insights from both decomposition and macroinvertebrate indices. Microbial humic-like DOM correlated positively with decomposition rates, and negatively with invertebrate species richness. Our findings show that functional changes in stream ecological condition can be effectively tracked by structural indicators, namely DOM composition. DOM offers a cost-effective approach to assessing ecosystem health and should be explored as a reliable indicator in monitoring programs and to inform functional-based indicators in ecosystem restoration.

Microplastics are transferred by soil fauna and regulate soil function as material carriers

The ecotoxicological effects of microplastics, a new and widespread ecosystem pollutant, have been extensively reported. However, it remains unclear whether soil fauna transfer microplastics and whether migration behaviours influence subsequent ecological functions in terrestrial ecosystems. We investigated the transfer patterns of microplastics and their adsorbed substances by soil animals (the springtail, Folsomia candida) and the effect of the transfer on the decomposition of soil organic matter through a standardized cotton strip assay. The results showed that springtails had a strong ability to transfer microplastics into the soil. The adsorbed nutrient (nitrogen; N), pollutant (cadmium; Cd), and green fluorescent Escherichia coli (GFP-E. coli) were also transferred with the microplastics. In addition, cotton strip decomposition was accelerated when the microplastics adsorbed N, but the adsorption of Cd decreased decomposition. These ecological effects were particularly strong for small microplastics. Microplastic transfer regulated soil bacterial communities, promoting the growth of Ascomycota fungi and inhibiting that of Basidiomycota, leading to cotton strip decomposition. Thus, microplastic pollution may occur at one site, but microplastics can be transferred anywhere in terrestrial ecosystems by soil animals and adsorb other substances, including nutrients and pollutants, that affect ecosystem function. Therefore, more studies on the migration behaviour of microplastics are necessary.

Organic Matter Decomposition in River Ecosystems: Microbial Interactions Influenced by Total Nitrogen and Temperature in River Water.

Microbes contribute to the organic matter decomposition (OMD) in river ecosystems. This study considers two aspects of OMD in river ecosystems which have not been examined in scientific studies previously, and these are the microbial interactions in OMD and the influence of environmental factors on microbial interactions. Cotton strip (CS), as a substitute for organic matter, was introduced to Luanhe River Basin in China. The results of CS assay, microbial sequencing, and redundancy analysis (RDA) showed that CS selectively enriched bacterial and fungal groups related to cellulose decomposition, achieving cotton strip decomposition (CSD). Bacterial phylum Proteobacteria and fungal phyla Rozellomycota and Ascomycota were the dominant groups associated with CSD. Network analysis and Mantel test results indicated that bacteria and fungi on CS cooperatively formed an interaction network to achieve the CSD. In the network, modules 2 and 4 were significantly positively associated with CSD, which were considered as the key modules in this study. The key modules were mainly composed of phyla Proteobacteria and Ascomycota, indicating that microbes in key modules were the effective decomposers of CS. Although keystone taxa were not directly associated with CSD, they may regulate the genera in key modules to achieve the CSD, since some keystone taxa were linked with the microbial genera associated with CSD in the key modules. Total nitrogen (TN) and temperature in water were the dominant environmental factors positively influenced CSD. The key modules 2 and 4 were positively influenced by water temperature and TN in water, respectively, and two keystone taxa were positively associated with TN. This profoundly revealed that water temperature and TN influenced the OMD through acting on the keystone taxa and key modules in microbial interactions. The research findings help us to understand the microbial interactions influenced by environmental factors in OMD in river ecosystems.

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

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

Exploring temporal and spatial variation in cotton tensile-strength loss to assess the ecosystem health of non-wadeable rivers

Abstract Cotton strip assays are becoming a widely utilised functional indicator to assess and interpret ecosystem health of non-wadeable rivers. Cotton decomposition may be sensitive to seasonal variation in key drivers, the aim of this study therefore, was to elucidate the temporal variation in cotton strip decomposition across a land-use gradient to underpin the utility of this technique as an indicator. Twelve sites, spanning a range of water quality, related to upstream land-use intensity were sampled monthly for 16 months. Mean cotton tensile-strength loss per day ranged from 0.8% to 13.2% per day across the study sites. Cotton tensile-strength loss was significantly related to mean water temperature, the concentration of dissolved nutrients, water clarity, and dissolved ions, in linear mixed models (all p

Cotton-strip decomposition rate as a river condition indicator – Diel temperature range and deployment season and length also matter

Decomposition of organic matter, a fundamental ecological process, has been proposed to be used as a functional indicator of stream condition. A recently published protocol for the use of the cotton-strip assay as a standardized measure of decomposition rates provided a basis for the use of decomposition as an indicator. However, some factors that may influence the application of the cotton-strip assay, such as the deployment season, remain largely unexplored. To further establish the technique, we studied temporal and spatial variability in cotton-strip decomposition rates along small upland rivers in SE Australia. We found a consistent longitudinal pattern in decomposition rates throughout the year, in spite of large within-site and site-specific temporal variability. Results from the models of temporal variability in decomposition rates indicate that differences in the duration of incubation might have been a confounding variable. Models of spatial variability in decomposition rates explained 45% and 52% of the variability in decomposition rates across five rivers, with diel temperature range being the most important predictor, accounting for ca. 20% of the variability in decomposition rates. We have shown that additional considerations are needed, if decomposition rates are to be compared across spatial and temporal scales. First, large within-site variability in decomposition rates, found in our and other studies, might prevent comparisons with reference conditions. Second, the length (and therefore the season) of cotton-strip deployment needs to be specified, since the exponential decomposition coefficient appears not to be a constant throughout time. Third, diel temperature range needs to be considered when establishing sampling protocols, since the exponential decay coefficient appears to change non-linearly with changing temperature, and therefore, using only daily mean temperatures does not realistically reflect the effect of temperature. The importance of temperature range also has implications for stream rehabilitation, showing that restoring the temperature regime contributes to the restoration of a fundamental ecosystem process.

Vegetation and Soil Dynamics of a Louisiana Estuary Receiving Pulsed Mississippi River Water Following Hurricane Katrina

We monitored wetland biomass, decomposition, hydrology, and soil porewater chemistry at the Breton Sound estuary, which receives Mississippi River water from the Caernarvon river diversion structure. The estuary was in the direct path of hurricane Katrina in 2005, which caused a dramatic loss of wetlands in the upper basin. From March 2006 to October 2007, we made duplicate measurements at three distance classes from the diversion structure along the estuarine gradient as well as at a reference area, designated Near (N1&2), Mid (M1&2), Far (F1&2), and Ref (R1&2). Above- and belowground live biomass, porewater nutrients (NOx, NH4, and PO4), salinity, sulfide, and soil Eh were measured every 2 months. Water level was monitored with gauges. Above- and belowground decomposition was measured using the litterbag (both) and cotton strip (belowground only) methods. Analysis of porewater parameters showed that stress factors affecting biomass production (porewater salinity, sulfide, flooding, and redox potential) were generally low to moderate, while measurable porewater nutrient concentrations occurred at all sites. Aboveground end of season live (EOSL) standing crop in October ranged from 423 g/m2 at site M2 to 1,515 at site F1, and was significantly greater at site N1 than at sites N2, M1, or M2. Aboveground EOSL biomass during this study was significantly lower than previously measured in 1999, 2000, and 2001. Peak belowground biomass ranged from 8,315 g/m2 at site R2 to 17,890 g/m2 at site N1, which is among the highest reported in the literature, and there were significant increases throughout the study, suggesting recovery from hurricane Katrina. The decomposition bag data did not indicate any significant differences; however, the cotton strip decomposition rate was significantly lower at the lowest depth. Wetland surface vertical accretion ranged from 0.49 cm/year at N2 to 1.24 cm/year at N1, with site N1 significantly greater than N2, M1, F2, and R1, and site N2 significantly less than all other sites except site R1. These findings show that marsh productivity and stability is related to a number of factors and no one factor can explain the impacts of the hurricanes.

Effects of nitrogen and phosphorus on vegetation dynamics of a degraded native grassland in semi-arid south-eastern Australia

The roles of nitrogen (N) and phosphorus (P) in controlling vegetation transitions in a degraded semi-arid grassland were investigated in a factorial experiment that combined two initial levels of perennial plant density (low and high), three levels of N (N+, N0 and N–) and two levels of P (P+ and P0). Increased levels of both N and P were achieved by fertiliser addition while sucrose was used to reduce the level of N. Vegetation dynamics were driven primarily by soil N rather than P. Addition of sucrose, which was inferred to result in the immobilisation of mineral N, reduced the growth of annual species and facilitated the establishment and growth of native perennial grasses. Addition of P generally had no significant effect on dry matter production, either in total or for species grouped as forbs, annual grasses and perennial grasses, or on recruitment and mortality of perennial grasses. However, at some times of observation addition of P increased ground cover and/or the basal circumference of some perennial grass species. Basal circumference for Enteropogon acicularis was also increased by addition of N. Soil biological activity, measured by decomposition of cotton strips, was increased by addition of N, which maintained vegetation in an annual-dominated condition, and was not affected by addition of P. Carbon addition has the potential to assist restoration of this grassland. However, the capacity of some native grass species to respond to increased fertility suggests that once restoration is achieved some increase in fertility may be beneficial for pastoral production.

Soil microbial and faunal responses to herbicide tolerant maize and herbicide in two soils

A glasshouse experiment was set up to compare processes and organisms in two soils planted with genetically modified (GM) herbicide tolerant (HT) maize treated with appropriate herbicides. This was part of a wider project (ECOGEN) looking at the consequences of GM cropping systems on soil biology using a tiered approach at laboratory, glasshouse and field scales. Soil for the experiment was taken from field sites where the same maize cultivars were grown to allow comparison between results under glasshouse and field conditions. The maize cultivars T25 (GM HT glufosinate-ammonium tolerant), Orient (non HT near isogenic control for T25) and Monumental (a conventional, non HT variety) were grown in contrasting sandy loam and clay loam soils, half were sprayed with the appropriate herbicide as used in the field and soil samples were taken at the five-leaf and flowering plant growth stage. The main effects on all measured parameters were those of soil type and plant growth stage, with four categories of subsequent interaction: (1) there were no effects of herbicide on plant growth or soil microarthropods: (2) the maize cultivar (but not the GM HT trait) had effects on the decomposition of cotton strips and the nematode community; (3) herbicide application in general altered the community level physiological profile of the microbial community and reduced both soil basal respiration and the abundance of protozoa; and (4) the specific application of glufosinate-ammonium to T25 maize altered soil microbial community structure measured by ester linked fatty acids. The results from this glasshouse experiment support the findings from the field that there are effects of herbicide application on the soil microbial and meso-faunal community but that, compared to other standard agricultural practices, the differences are relatively small.

Cotton strips as a leaf surrogate to measure decomposition in river floodplain habitats

AbstractLeaf-litter assays have advanced understanding of decomposition processes in both terrestrial and aquatic ecosystems. Some shortcomings inherent in the technique may be overcome through use of a cotton-strip assay. Key assumptions for using cotton strips as proxies for natural leaves are: 1) decomposition rates of the 2 materials are related, and 2) the materials decay in a similar way when exposed to the same environmental conditions. These assumptions were tested by comparing cotton-strip decomposition (loss of tensile strength and mass) and leaf decomposition (mass loss) across different floodplain habitats of the Tagliamento River (northeastern Italy). Patterns of loss of cotton-strip tensile strength and leaf mass were broadly comparable across river channels, ponds, and terrestrial sites. Differences between river channels and ponds were greater for loss of cotton-strip tensile strength than leaf mass, indicating that, in some situations, loss of cotton-strip tensile strength may be more sen...

Suitability of wheat straw decomposition, cotton strip degradation and bait-lamina feeding tests to determine soil invertebrate activity

The activities of earthworms, springtails and mites in the decomposition of different substrates were examined by applying three different test methods: wheat straw degradation, the cotton-strip assay and the bait-lamina test. The main aim was to determine the potential of these three methods to describe the (direct and indirect) contribution of soil invertebrates to decomposition processes in soil. Animals were introduced at different densities to mesocosms consisting of intact soil cores taken from grassland. Wheat straw mass loss, determined after 27 days, and cotton tensile strength loss, measured after 14 days, did not significantly differ for the different densities of earthworms, springtails and mites. These findings indicate that cellulose degradation and wheat straw decomposition are more dependent on microbial activity, rather than on the abundance and activity of soil invertebrates. Soil microbial activity, measured as dehydrogenase activity at the end of the 75-day incubation period, did not show any correlation with animal density. Bait-lamina consumption rate was highest for the mesocosms containing earthworms, and increased with increasing earthworm density. Bait-lamina consumption in the mesocosms inoculated with springtails or mites only was not significantly different from that in the controls without animals. In the case of the mites this might at least partly be explained by the low densities used in this experiment. It may be concluded that whilst the bait-lamina test gives the best reflection of the biological activity of soil animals, in particular earthworms, wheat straw and cotton strip decomposition rates are more indicative of microbial activity in the soil.

Field and Microcosm Studies of Decomposition and Soil Biota in a Cold Desert Soil

In the extreme cold desert soil of the McMurdo Dry Valleys of Antarctica, we studied the effects of changing moisture and temperature on rates of decomposition and the activity and abundance of soil organisms. Our objective was to understand how moisture and temperature structure invertebrate communities and control important ecosystem processes and soil biotic activity in this extreme environment. First, in a field experiment, we manipulated soil moisture and temperature and compared cotton strip decomposition rates at two dry valley sites with different moisture regimes. At both sites, live nematode abundance and activity were unchanged by soil treatments over the 2-year study. In the same plots, the cotton strips did not decompose, despite soil warming and the addition of moisture. The results suggest that biological activity in the McMurdo Dry Valleys is severely limited and that soil organisms are not responsive to improving environmental conditions. Second, in microcosms, we manipulated dry valley soil moisture at a constant temperature of 10°C and measured the rates of key soil processes. Soil respiration, nitrification, and the decomposition of cotton strips were all greater in dry valley soils that were wetted to 10% moisture content, as compared to soils at 0.6%. These results indicate that the decomposition potential for dry valley soils is high when moisture and temperature limitations are removed. In the field, however, this process was extremely slow, and biota did not respond to improving environmental conditions. Soil processes appear to be limited primarily by the extreme desiccation of the dry valleys. Ecosystems processes are likely restricted to the brief periods following infrequent snowfall, melt, and soil wetting that permit the activity of soil microbes and biota.

Integrative biological indicators for detecting change in soil quality

AbstractTo promote agricultural sustainability, there is a growing interest in developing soil quality indicators that can be used as early indicators of changes in management practices by growers, agricultural professionals, and researchers. A study was conducted on four commercial growers' fields and two research stations in western Oregon with treatments that had been started from 1 to 7 years prior to initiating the investigation. The primary comparison at each site was a winter cover crop and winter fallow in rotation with summer vegetable crops. The effects of these treatments on microbial biomass carbon (MBC), mineralizable N, soil enzyme activity (arylsulfatase and β-glucosidase), and cotton strip decomposition were analyzed to monitor changes in soil quality over a 2-year period. The cotton strip method was tested because of its simplicity (buried in soil for short periods and then assessed for tensile strength or weight loss) and potential as a soil biological indicator. Results showed that cover cropping significantly affected MBCand soil enzyme activity. Mineralizable N and CO2respiration (laboratory incubation) did not respond to winter cover crop treatment. Cotton strip decomposition was relatively insensitive to field treatments. Because MBCand β-glucosidase activity responded quickly to field management treatment and were less variable than the other measurements, they showed the most potential as soil quality indicators. Total C (organic matter index) and extractable nutrients were not significantly affected by cover cropping (even after 7 years), indicating selected biological properties are superior to these chemical properties for detecting effects of soil management.

EFFECTS OF NUTRIENT ENRICHMENT ON WITHIN-STAND CYCLING IN A MANGROVE FOREST

Within-stand nutrient cycling is dependent on many factors, including primary productivity, nutrient-use efficiency, nutrient resorption, sclerophylly, decomposition, nutritional quality of plant tissue, and allocation to defense. The efficiency of these plant-mediated processes depends on nutrient availability in the environment and inherent functional properties of plants. However, little is known about how nutrient availability will affect these processes in forested wetlands in the tropics. In a factorial experiment we fertilized 48 dwarfed Rhizophora mangle (red mangrove) trees along tidal-elevation and water-depth gradients at Twin Cays, a range of intertidal, peat-based offshore mangrove islands in Belize, Central America. Initial results indicated that phosphorus (P) deficiency is a major factor limiting primary productivity. Phosphorus-fertilized trees had a significant decrease in P-use efficiency and P-resorption efficiency, but a significant increase in nitrogen (N)-use efficiency and N-resorption efficiency in their leaves compared with controls and N-fertilized trees. Sclerophylly decreased dramatically in P-fertilized trees, while the nutritional quality of the plant tissue increased. Phosphorus fertilization did not affect P leaching from green leaves. We found no fertilizer effect on the decomposition rates of leaf tissue, possibly due to higher phenolic concentrations in the P-fertilized trees compared with controls and N-fertilized trees. However, belowground decomposition of cotton strips increased in the substrate associated with P-fertilized trees. Environmental conditions related to position along a tidal gradient may be as important as nutrients in controlling belowground decomposition.

Experimental manipulations of water and nutrient input to a Norway spruce plantation at Klosterhede, Denmark

At Klosterhede, Denmark experimental manipulations of the input of water and nutrients to a Norway spruce forest stand have been performed. The manipulations included fertilizer application, irrigation and creation of artificial dry periods. Further, the acidic input was excluded from the soil by a 1200 m 2 roof. The aim of this study was to quantify the effects of air pollutants on the internal cycling of nutrients in the forest ecosystem and to assess the influence of the manipulations on the canopy interacting processes, the soil water composition and the turnover of organic matter. The improved nutrient availability and the increased soil water content in the fertigation (fertilizer application + irrigation) and the irrigation plots under the roof resulted in an increased decomposition of cotton strips compared to the uncovered control plot. However, the decomposition of needle material (litterbags) in the roof covered plots was reduced probably due to altered humidity conditions in the humic layer as a result of the irrigation system. Significant changes to the manipulations were seen in the soil water concentrations of SO 4 2− in the irrigated and the fertigated plots and of K + in the irrigated plot which show that the internal cycling and dynamics of sulphur and potassium are very sensitive to interference in the input. The effect of reduced acid input on soil water concentrations of Al and H + was not evident before the 5th year of treatment where Al concentration was reduced almost 50% at 55 cm depth on the «clean rain» (irrigated) plot. It was not possible to detect any enlarged throughfall deposition on the fertigated and irrigated plots despite an observed rise in the canopy surface area on these plots or to detect any changes in canopy leaching reflecting changes in nutrient status

Comparison of the Microbiology of Four Soils in Finnish Lapland

A subalpine heath soil, a palsa peat, and two iron podsols in Utsjoki, Finland were investigated. Counts of viable aerobic chemo-organotrophic bacteria and yeasts were made together with determinations of dehydrogenase and invertase enzymes, laboratory respiration, nitrogen fixation by acetylene reduction, chemical analyses and decomposition of cotton strips. Each soil was studied at several depths. Of the surface horizons, the podsol under birch was the most active by all the methods used followed in order by the other podsol, the subalpine heath and the palsa peat. Unlike soils under more extreme climatic conditions subarctic soils contain few yeasts.