Decaying Plant Material Research Articles

Denitrification in a natural wetland receiving secondary treated effluent

The potential of a natural wetland as a site for nitrogen removal from secondary treated effluent was examined by investigating the distribution of denitrification rates and activity in soils and decaying plant material. Field measurements of soil Eh, pH and temperature showed that the effluent inflow favours denitrification by lowering Eh, maintaining pH 6.4–6.7, and raising soil temperature. Analysis of soil concentrations of nitrate plus nitrite and ammonium ions shows that the effluent inflow increased the concentrations of inorganic nitrogen in the soil, and encouraged higher rates of denitrification. Denitrification rates measured by an acetylene blockage technique were highest in soil samples from downstream of the effluent inflow, with the maximum rates being recorded in soils from 0 to 60 cm and in decaying plant material lying on the soil surface. Both nitrate plus nitrite concentration and denitrification activity declined rapidly below 6 cm in upstream and downstream soil samples. Denitrification rates in the natural wetland are increased by the addition of secondary treated effluent, and make a year-round contribution to the removal of nitrogen from the wastewater. Rates of nitrogen removal in the wetland could be increased by encouraging greater spatial and temporal interaction of the effluent amended water with the sites of highest denitrification activity.

The fate of nitrogen (15N) released from different plant materials during decomposition under field conditions

Release of N, retention in soil, availability to a subsequent crop and total recovery of N derived from different15N-labelled plant materials decomposing in soil was investigated in two field experiments. In the first experiment five different plant species (white clover, red clover, subterranean clover, field bean and timothy) and in the second subterranean clover of different maturity (2,3 and 4 months old) were buried in mesh bags in the soil and allowed to decompose for 10 and 4 months, respectively. Most of the N released from the decaying plant materials was retained in the soil (27–46% of input). The subsequent crop (barley) took up 6–25% of input. The uptake correlated with the amount of N released from the decomposing material (r=0.936*, I experiment). Similar amounts of subterranean clover N were taken up by barley regardless to whether the material was buried in soil in the previous autumn or just before sowing of the crop. At the end of the experiments, the total recovery of the introduced plant-derived N varied between 89 and 102%. The results present evidence that the ability of the soil to retain plant-derived N is strong in comparison with the ability of the subsequent crop and different loss mechanisms to remove it.

Modelling of leachates from dolomitic mine tailings

The REDEQL.EPAK computer model was used to study speciation of Pb, Cd, Zn, and Ca in leachates from dolomitic Pb mine tailings. By allowing or disallowing precipitation of solids and equilibration of the modelled leachate with atmospheric C02, comparison of fresh and aged leachates was made. The effects of treatment of the tailings with phosphate containing fertilizer were studied through addition of P04 (3-) to the modelled solution. Equilibrium constants pertaining to metal ion-humic acid complexation were added to the thermodynamic data base of the model in order to study the effects of decaying plant material on tailings leachate.Initial leachate of the tailings is found to be supersaturated with Cd and Zn. Non-complexed ("free") Cd(2+) and Zn(2+) is predicted to comprise most of the soluble form of these metals in the leachate; Pb is predicted to be present largely as PbCO3 ion pair. Equilibration of the leachate with the atmosphere is predicted to lead to extensive precipitation of CdCO3 and ZnSiO3. Precipitation of Pb5(PO4)3Cl is predicted at high PO4 (3-) concentration and at low pH. Complexation by the humic acid is predicted to compete effectively with other ligands in the leachate for the metal ions. The results are compared with experimental findings.

Isolation and identification of myxobacteria from soils and plant materials, with special reference to DNA base composition, quinone system, and cellular fatty acid composition, and with a description of a new species, Myxococcus flavescens.

Myxobacteria were isolated in Japan from soils, decaying plant materials, and tree bark. The isolation methods we have used are the rabbit dung method, placing soil on bacterial smears, the filter paper method, and the agar medium method. Placing soil on bacterial smears was easy to manage. Addition of dealkaline lignin stimulated formation of well- differentiated fruiting bodies on agar medium. This made it possible to investigate the morphology of fruiting bodies of myxobacteria on the agar medium in the laboratory. The myxobacteria isolated and purified were found to be strains of the genera Myxococcus and Archangium. Isolates were identified as Myxococcus stipitatus, Myxococcus fulvus, Myxococcus coralloides, and Archangium gephyra. A new species Myxococcus flavescens is proposed on the basis of morphological characteristics and production of diffusible light yellow pigment. All the tested strains gave positive reactions in catalase and urease. The DNA base composition of the myxobacteria examined ranged from 65 to 67mol% of guanine plus cytosine. The major quinone was menaquinone with 8 isoprenoid units (MK-8). The major cellular fatty acids were iso 15:0, iso 17:0, and 16:1.

Microorganisms on Water Hyacinth in Eastern Australia: A Survey in Relation to Biological Control by Insects

Fungi were isolated from diseased and decaying water hyacinth, Eichhornia crassipes (Mart.) Solms-Laub. from twenty three sites in eastern Australia. Some of the fungi had not previously been recorded on this host, but the majority were species known on water hyacinth in America and Asia, including pathogens Acremonium zona tum (Sawada) Gams and Cercospora piaropi Tharp. Bacteria isolated were Pseudomonas fluorescens and a non-fluorescent pseudomonad unlike any published species description. A greater variety of fungi occurred on plants damaged by the insect biological control agents, Ncochetina eichhorniae Warner and Sameodes a/bigullalis (Warren) than on plants not attacked by these insects. Many of the species are ubiquitous on decaying plant material. No particular fungus could be recognised as the main cause of necrosis which is associated with damage by insect larvae to the petiole and rhizome, but microorganisms are considered to be important in achieving the overall biological control. In contrast to other infections of the lamina, the lethal effect of a leaf blight was linked to severe infection of the lamina of the younger leaves. In glasshouse pathogenicity tests, Fusarium spp., A. zona tum and C. piaropi caused more disease than any other microorganism tested. A. zona tum and C. piaropi are considered to have the greatest potential for development as mycoherbicides.

Regulation of Tin and Methyltin Compounds by the Green Alga Enteromorpha under Simulated Estuarine Conditions

The cycling of inorganic tin and methyltin compounds was examined in the presence of the green alga Enteromorpha at different salinities. We monitored flasks containing live and dead Enteromorpha under oxic experimental conditions for 17 d and determined inorganic tin and methyltin compounds by chromatography – atomic absorption spectrometry. Addition of acidic inorganic tin to some flasks resulted in plant decay. Processes associated with healthy and decaying plant material included release of inorganic tin and methyltin compounds, their interconversions in solution, and uptake of inorganic tin. Enteromorpha releases inorganic tin as well as mono-, di-, and trimethyltin. Added inorganic tin was mostly removed from solution after its addition, and all three methyltin compounds were produced. The methyltin compounds cycle such that high concentrations of trimethyltin were concomitant with low mono- and dimethyltin concentrations and vice versa. We describe possible biological and chemical processes responsible for interconversions of inorganic tin and methyltin compounds in solution and the environmental significance of seaweed in the biogeochemical cycling of tin.

Biogeochemical cycling of lignocellulosic carbon in marine and freshwater ecosystems: Relative contributions of procaryotes and eucaryotes1

The relative contributions of procaryotes and eucaryotes to the degradation of the lignin and polysaccharide components of lignocellulosic detritus in two marine and two freshwater wetland ecosystems were determined. Two independent methods—physical separation of bacteria from fungi and other eucaryotes by size fractionation, and antibiotic treatments— were used to estimate procaryotic and eucaryotic contributions to the degradation of [14C‐lignin]lignocelluloses and [14C‐polysaccharide]lignocelluloses in samples of water and decaying plant material from each environment. Both methods yielded similar results; bacteria were the predominant degraders of lignocellulose in each of the aquatic ecosystems. Fungi and other eucaryotes contributed only minimally to the overall degradation of lignocellulose in both marine ecosystems and in the Okefenokee Swamp but did contribute significantly to the degradation of lignocellulose in the Big Cypress Swamp. These results indicate a basic difference between the microbial degradation of lignocellulosic material in terrestrial and aquatic environments. Fungi have long been considered the predominant degraders of lignocellulose in terrestrial systems; our results indicate that in aquatic systems bacteria are the predominant degraders of lignocellulose.

The feeding strategies of juvenile and adult Biomphalaria glabrata (Say) under simulated natural conditions and their relevance to ecological theory and snail control

Aspects of the feeding biology of the freshwater pulmonate snail Biomphalaria glabrata were studied under simulated natural conditions in the laboratory by examining crop and rectal contents, the mouth parts of the snail and its method of feeding when presented with a variety of potential food items. The results confirm the generalization that freshwater pulmonate snails, such as B . glabrata , subsist mainly by selecting decaying macrophyte tissue, colonial diatoms and smaller green algae in preference to living macrophyte tissue, filamentous green algae, or small adpressed forms of epiphytic diatoms and epiphytic bacteria. The generalist feeding strategy adopted by B . glabrata can be related to the morphology of the mouth parts and to its feeding behaviour. The adult snail has a total of about 4425 radula teeth (in 75 transverse rows each with 59 teeth) whose dimensions are of the same order of magnitude as diatoms, with narrow gaps in between, thus making the radula an ideal system for scraping the larger, colonial diatoms from the surface of freshwater macrophytes, but not the smaller adpressed diatoms or bacteria. The snails show considerable flexibility in the use of the mouth parts. Thus, the extent of the area grazed by the radula can be regulated by changes in the direction or velocity of the head movements. The latter may be either straight or pendular while the number of bites per sweep can be varied from two to nine. The dorsal mandible may also be used independently for scraping epiphytic algae. Living macrophyte tissue is cut by the backwardly directed power stroke of the radula, sometimes acting in opposition to the dorsal mandible, whereas the flaccid decaying macrophyte tissue can be ingested by a pumping action with minimal use of the radula. The costs and benefits of the various strategies are discussed. There are marked differences between the feeding niches of juvenile and adult B . glabrata as the former eat less living macrophyte tissue and fewer species of large diatoms but much larger quantities of decaying plant material than their adult conspecifics. These ontogenetic changes can be related to variations in the relative growth rate of the odontophore and their chemoreception niches. The ratio of the abundance of food items in the crop to the rectum indicate that macrophyte tissue is probably used almost completely but that the green algae Scenedesmus and Rhizoclonium may pass through the gut undigested. Many of the diatom species are also resistant to digestion. The sizes of particles ingested vary from 0.026 to 0.78 mm 2 the latter being the largest the snails are capable of swallowing. As the snails prefer flaccid material it is suggested that controlled release formulations, designed to kill target snails selectively, should be of this consistency and the above size range. The results are discussed within the context of the hypothesis that the snails, the macrophytes, their epiphytic algae and the bacteria involved in decomposition are components of a module with six subsets (Paine 1980). Evidence is given that the linkage between each of the subsets are strongly mutualistic, and that they involve the release and use of dissolved organic matter. It is argued that these positive interactions must be taken into account when constructing models to explain stability and complexity of communities.

Slime Molds in the Laboratory II: Moist Chamber Cultures

In a previous article (see ABT, February 1982), I described the techniques involved in making field collections of the fruiting bodies of plasmodial slime molds, or Myxomycetes. Slime molds are common inhabitants of decaying plant material throughout the world. However, despite their abundance and widespread occurrence, relatively little use has been made of these fascinating and biologically enigmatic organisms in laboratory studies. There are a number of reasons why this is the case. First of all, because of their small size and the types of situations in which they occur, slime molds are easily overlooked in the field and thus are not familiar organisms to many biology instructors. Moreover, until the appearance of Farr's How to Know the True Slime Molds (1981), a fairly comprehensive and relatively nontechnical guide for the identification of slime molds simply did not exist. Also, the very fact that these organisms do not possess a particularly attractive common name probably hasn't helped matters! Although slime molds have considerable potential value in laboratory studies, as was pointed out in the previous article, some major constraints do exist in regards to making field collections of these organisms. First of all, since slime mold fruiting bodies tend to be most abundant during summer and early autumn for much of the United States, their period of max-. imum availability largely falls outside the academic year. Furthermore, many instructors who might otherwise make use of these organisms do not have access to the moist, forested areas where slime mold fruiting bodies are particularly abundant and thus most easily collected. However, laboratory studies of slime molds do not have to be restricted to material collected in the field (or purchased from a biological supply house). The purpose of this article is to describe a technique for obtaining slime molds (plasmodia as well as fruiting bodies) in the laboratory, using pieces of tree bark placed in moist chamber cultures. This technique is relatively easy to carry out and requires no special equipment. Moreover, it can be used at any time of the year and in any part of the country.

Fine-Grained Sediments of an Interdistributary Basin, Mississippi Delta: ABSTRACT

A considerable portion of fine-grained sediments of the Mississippi Delta can be found in large-scale interdistributary basins that are located between distributary channels of different delta lobes of the same delta system. Because of their size, these basins are prone to filling with fine-grained material. Thus, the central basin is devoid of coarser influxes from the surrounding levees. Barataria basin (about 150 × 50 km in size) is such a basin bordered by the modern Mississippi River and the abandoned Bayou Lafourche. Ninety-five vibracores, 3-10 m deep, form the basis for this study. Correlation between cores along cross sections is based on lithology and organic matter content. X-ray radiographs show common occurrences of massive homogeneous and fine parallel- aminated sequences. Small-scale cross-lamination, lenticular bedding, and faunal bioturbation are rare, the latter most likely because of oxygen-starved conditions. Subtle facies differences can be detected between levees, basin drainage channels, lacustrine areas, submerged marsh bottoms, and various peats. Early diagenesis occurred throughout the basin in the form of heavy pyritized and/or calcite-rich zones. From examination of thin sections, both by light microscopy and SEM, it appears pyrite is most abundant in marsh sediments with intermediate (about 30-70%) organic matter content. These marshes contain sufficient iron (from clays) and sulfur (associated with decaying plant matter) to give rise to pyrite formation. Detailed analyses of a basin of this kind are important in predicting and understanding geometry, continuity, and diagenetic features of deltaic shales. In addition, when reworked, these materials form possible source beds for hydrocarbons found in continental shelf and slope settings. End_of_Article - Last_Page 275------------

Application of14C-Labeled Herbicides in Lysimeter Studies

Most herbicides are applied preemergence onto bare soil or during the early stage of plant development. Therefore, the major part of the active ingredient either reaches the soil surface immediately or later with decaying plant material. The further fate of the herbicide depends largely on the physicochemical behavior of the respective compound, the amount and method of application, and a number of soil, plant, and climatic factors influencing the persistence and bio availability of organic compounds in a given soil (5, 7). Especially in the upper 2-cm soil layer, drastic changes in temperature and moisture content during a growing season have a great influence on the degradation and adsorption of herbicides in soil (10, 31).

Cellulase activity in natural and temperature acclimated populations of Fundulus heteroclitus

Cellulase activity in natural and temperature acclimated populations of Fundulus heteroclitus

Current status, habitat requirements and management of the Larch Mountain salamander Plethodon larselli burns

The Larch Mountain salamander Plethodon larselli is endemic to a narrow corridor along the Columbia River gorge where it occurs within talus slopes in the states of Washington and Oregon. While very little new information has been published on this species since its first description by Burns (1954), its limited range and data indicating that most populations are small and isolated suggest that it is a relict species on the decline. Space analysis of the microhabitat requirements indicates that this plethodon is restricted to steep, wooded talus slopes where the rocks are of small size (1 to 6 cm in length) and there are relatively large amounts of decaying plant material and small quantities of soil. Recently identified additional populations are being or have been severely impacted by a variety of human activities, including extensive removal of gravel from the slopes for road building and maintenance and clear cutting of the overstorey. These environmental alterations appear to damage significantly the salamander's habitat. Therefore, if this species is to survive, appropriate action must be undertaken immediately to protect the remaining habitat.

The influence of conditioning on olfactory microhabitat and host location in Asobara tabida (Nees) and A. rufescens (Foerster) (Braconidae: Alysiinae) larval parasitoids of Drosophilidae.

Olfactory responses of parasitoids can be variable. This was shown by olfactometer experiments with females of two sibling Asobara species, larval endoparasitoids of Drosophilidae. Oviposition experiences of adult female parasitoids significantly altered their behavioural responses in microhabitat and host location. Females needed prior exposure to a host before they were capable of using volatile compounds related to the presence of their host. Asobara tabida (Nees) attacks Drosophila in fermenting fruits and A. rufescens (Foerster) attacks Drosophilidae in decaying plant materials. Naïve females show a strong preference for the odour of their own microhabitat. After experience with their own host and microhabitat, females were repelled by odours of the other microhabitat. 'Enforced' experience with this repellent microhabitat in the laboratory modified the olfactory response from repellency to attraction. It was shown that even the microhabitat odour preference pattern could be changed through experience. This kind of behavioural flexibility may be the rule rather than the exception in many other Hymenopterous parasitoids.

The Influence of Arthropods on Ecosystems

Arthropod interactions with plants and microbes influence the amounts of living and dead organic matter and transfers of nutrients in terrestrial ecosystems. Arthropods in the canopy have their greatest effect on mobile elements such as potassium, whereas soil detritivores influence mineralization rates of less mobile elements such as nitrogen, phosphorus, and calcium. Nominal (baseline) herbivory and detritivory combine to speed nutrient cycling and reduce standing crops of decaying plant materials. 49 references, 1 figure, 3 tables.

Additional Hyphomycetes from freshwater swamps and hammocks

Collections of submerged, decayed plant material from freshwater swamps in Illinois and hammocks in Florida have yielded two new species, Intercalarispora nigra gen. et sp. nov. and Monodictys cruciseptata sp. nov. New records for North America include Zanclospora novae-zelandicae Hughes & Kendrick and Pseudopetrakia kambakkamensis (Subram.) M. B. Ellis.

Hyphomycetes from freshwater swamps and hammocks

Some Hyphomycetes collected on decayed plant material from freshwater swamps and hammocks include Parasympodiella minima sp. nov., Paratomenticola georgiana sp. no v., Scolecobasidium cylindrosporum sp. nov., Chaetopsina ludoviciana sp. nov., and Taeniolella americana sp. nov. In addition, Cryptophiale udagawae Pirozynski & Ichinoe, Exserticlava vasiformis (Matsushima) Hughes, Mycoenterolobium platysporum Goos, and Phragmospathula phoenicis Subram. & Nair are reported as new records for North America.

Species diversity of Ichneumonidae and Serphidae (Hymenoptera) in an English suburban garden

In the two-year period, 1972–73, 6445 Ichneumonidae of 455 species were caught in a Malaise trap operated in a suburban garden in Leicester, England. An additional 74 species were trapped in 1974. The collection includes a number of species new to the British list. The flight season of ichneumonids extended from March to November or December, with peak abundance and diversity in August. Size of trap samples fluctuated erratically, depending on air temperature. No species was particularly common and many were rare, 141 being taken once only in the two-year period. The commoner species were present throughout the season, supporting the suggestion that ichneumonids are niche-specific rather than host-specific. Parasites of aphidophagous Neuroptera and Syrphidae, of spiders, of micro-Lepidoptera, and of Diptera found in decaying plant material were especially abundant, as is characteristic of the British fauna as a whole. Adult ichneumonids are mobile, and it is assumed that the Malaise trap was sampling an area far larger than the garden in which it was sited, although suburban gardens are a particularly favourable habitat for ichneumonids. Twenty-two species of Serphidae were captured in the Malaise trap during 1972–74, five of them new to Britain.

Allelopathy of Leafy Spurge (Euphorbia esula)

The allelopathic potential of leafy spurge (Euphorbia esulaL.) was investigated in the field and greenhouse. Reductions in frequency and density of quackgrass [Agropyron repens(L.) Beauv.] and common ragweed (Ambrosia artemisiifoliaL.) were noted where leafy spurge had high densities in the field. Field soil samples taken from areas of moderate and high leafy spurge densities inhibited tomatoes (Lycopersicon esculentumMill.) in the greenhouse. Growth of seedlings was inhibited up to 60% when leafy spurge leaves, roots, or litter were incorporated into soil, but surface applied leafy spurge litter had no effect. Growth inhibition was demonstrated for crabgrass [Digitaria sanguinalis(L.) Scop.] and tomato when 0.1 to 1.0% (w/w) of leafy spurge leaves or roots were added to soil. Based on these studies we postulate that leafy spurge exhibits allelopathic characteristics which may result from the incorporation of dead or decaying plant material in soil.

Rhizopus stolonifer . [Descriptions of Fungi and Bacteria

Abstract A description is provided for Rhizopus stolonifer . Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: On soil, fruit and vegetables and decaying plant material, and associated with disorders of man and animals. DISEASE: Causes a wet, pale brown soft rot of many fruit and vegetables. Particularly severe in storage on sweet potatoes, peaches and strawberries. Known as 'whiskers' because of profuse mycelial growth or 'leek' because of soft watery rot. Mildly parasitic to maturing fruit before they are harvested but primarily a wound invading fungus. It is reported as poisoning man (RMVM 6, 1831) and cattle (RMVM 6, 2161) and, experimentally, rats (RMVM 6, 1831). This species has been reported from various phycomycoses of man (RMVM 7, 1885, 3081, 4440; 11, 406), from bovine mycotic abortion (RMVM 6, 2145) and is reported to be experimentally pathogenic to rabbits (RMVM 7, 4027). However, doubt is cast on the role of R. stolonifer as a pathogenic organism in warm-blooded animals as it does not grow at 37°C. GEOGRAPHICAL DISTRIBUTION: World-wide. TRANSMISSION: By air-borne sporangiospores and also by fruit flies ( Drosophila melanogaster ) associated with decaying fruits (43, 576).