Above- and belowground responses of Arctic tundra ecosystems to altered soil nutrients and mammalian herbivory

Theory and observation indicate that changes in the rate of primary production can alter the balance between the bottom-up influences of plants and resources and the top-down regulation of herbivores and predators on ecosystem structure and function. The exploitation ecosystem hypothesis (EEH) posited that as aboveground net primary productivity (ANPP) increases, the additional biomass should support higher trophic levels. We developed an extension of EEH to include the impacts of increases in ANPP on belowground consumers in a similar manner as aboveground, but indirectly through changes in the allocation of photosynthate to roots. We tested our predictions for plants aboveground and for phytophagous nematodes and their predators belowground in two common arctic tundra plant communities subjected to 11 years of increased soil nutrient availability and/or exclusion of mammalian herbivores. The less productive dry heath (DH) community met the predictions of EEH aboveground, with the greatest ANPP and plant biomass in the fertilized plots protected from herbivory. A palatable grass increased in fertilized plots while dwarf evergreen shrubs and lichens declined. Belowground, phytophagous nematodes also responded as predicted, achieving greater biomass in the higher ANPP plots, whereas predator biomass tended to be lower in those same plots (although not significantly). In the higher productivity moist acidic tussock (MAT) community, aboveground responses were quite different. Herbivores stimulated ANPP and biomass in both ambient and enriched soil nutrient plots; maximum ANPP occurred in fertilized plots exposed to herbivory. Fertilized plots became dominated by dwarf birch (a deciduous shrub) and cloudberry (a perennial forb); under ambient conditions these two species coexist with sedges, evergreen dwarf shrubs, and Sphagnum mosses. Phytophagous nematodes did not respond significantly to changes in ANPP, although predator biomass was greatest in control plots. The contrasting results of these two arctic tundra plant communities suggest that the predictions of EEH may hold for very low ANPP communities, but that other factors, including competition and shifts in vegetation composition toward less palatable species, may confound predicted responses to changes in productivity in higher ANPP communities such as the MAT studied here.     

The age of island-like habitats impacts habitat specialist species richness

While the effects of contemporaneous local environment on species richness have been repeatedly documented, much less is known about historical effects, especially over large temporal scales. Using fen sites in the Western Carpathian Mountains with known radiocarbon-dated ages spanning Late Glacial to modern times (16 975-270 cal years before 2008), we have compiled richness data from the same plots for three groups of taxa with contrasting dispersal modes: (1) vascular plants, which have macroscopic propagules possessing variable, but rather low, dispersal abilities; (2) bryophytes, which have microscopic propagules that are readily transported long distances by air; and (3) terrestrial and freshwater mollusks, which have macroscopic individuals with slow active migration rates, but which also often possess high passive dispersal abilities. Using path analysis we tested the relationships between species richness and habitat age, area, isolation, and altitude for these groups. When only matrix-derived taxa were considered, no significant positive relation was noted between species richness and habitat size or age. When only calcareous-fen specialists were considered, however, habitat age was found to significantly affect vascular plant richness and, marginally, also bryophyte richness, whereas mollusk richness was significantly affected by habitat area. These results suggest that in inland insular systems only habitat specialist (i.e., interpatch disperser and/or relict species) richness is influenced by habitat age and/or area, with habitat age becoming more important as species dispersal ability decreases.     

Landscape-level influences of terrestrial snake occupancy within the southeastern United States

Habitat loss and degradation are thought to be the primary drivers of species extirpations, but for many species we have little information regarding specific habitats that influence occupancy. Snakes are of conservation concern throughout North America, but effective management and conservation are hindered by a lack of basic natural history information and the small number of large-scale studies designed to assess general population trends. To address this information gap, we compiled detection/nondetection data for 13 large terrestrial species from 449 traps located across the southeastern United States, and we characterized the land cover surrounding each trap at multiple spatial scales (250-, 500-, and 1000-m buffers). We used occupancy modeling, while accounting for heterogeneity in detection probability, to identify habitat variables that were influential in determining the presence of a particular species. We evaluated 12 competing models for each species, representing various hypotheses pertaining to important habitat features for terrestrial snakes. Overall, considerable interspecific variation existed in important habitat variables and relevant spatial scales. For example, kingsnakes (Lampropeltis getula) were negatively associated with evergreen forests, whereas Louisiana pinesnake (Pituophis ruthveni) occupancy increased with increasing coverage of this forest type. Some species were positively associated with grassland and scrub/shrub (e.g., Slowinski's cornsnake, Elaphe slowinskii) whereas others, (e.g., copperhead, Agkistrodon contortrix, and eastern diamond-backed rattlesnake, Crotalus adamanteus) were positively associated with forested habitats. Although the species that we studied may persist in varied landscapes other than those we identified as important, our data were collected in relatively undeveloped areas. Thus, our findings may be relevant when generating conservation plans or restoration goals. Maintaining or restoring landscapes that are most consistent with the ancestral habitat preferences of terrestrial snake assemblages will require a diverse habitat matrix over large spatial scales.     

Traits, not origin, explain impacts of plants on larval amphibians

Managing habitats for the benefit of native fauna is a priority for many government and private agencies. Often, these agencies view nonnative plants as a threat to wildlife habitat, and they seek to control or eradicate nonnative plant populations. However, little is known about how nonnative plant invasions impact native fauna, and it is unclear whether managing these plants actually improves habitat quality for resident animals. Here, we compared the impacts of native and nonnative wetland plants on three species of native larval amphibians; we also examined whether plant traits explain the observed impacts. Specifically, we measured plant litter quality (carbon : nitrogen : phosphorus ratios, and percentages of lignin and soluble phenolics) and biomass, along with a suite of environmental conditions known to affect larval amphibians (hydroperiod, temperature, dissolved oxygen, and pH). Hydroperiod and plant traits, notably soluble phenolics, litter C:N ratio, and litter N:P ratio, impacted the likelihood that animals metamorphosed, the number of animals that metamorphosed, and the length of larval period. As hydroperiod decreased, the likelihood that amphibians achieved metamorphosis and the percentage of tadpoles that successfully metamorphosed also decreased. Increases in soluble phenolics, litter N:P ratio, and litter C:N ratio decreased the likelihood that tadpoles achieved metamorphosis, decreased the percentage of tadpoles metamorphosing, decreased metamorph production (total metamorph biomass), and increased the length of larval period. Interestingly, we found no difference in metamorphosis rates and length of larval period between habitats dominated by native and nonnative plants. Our findings have important implications for habitat management. We suggest that to improve habitats for native fauna, managers should focus on assembling a plant community with desirable traits rather than focusing only on plant origin.     

Characterization and modelling of the heat transfers in a pilot-scale reactor during composting under forced aeration

The paper focused on the modelling of the heat transfers during composting in a pilot-scale reactor under forced aeration. The model took into account the heat production and the transfers by evaporation, convection between material and gas crossing the material, conduction and surface convection between gas and material in bottom and upper parts of the reactor. The model was adjusted thanks to the measurements practised during fifteen composting experiments in which five organic wastes were, each, composted under three constant aeration rates. Heat production was considered proportional to oxygen consumption rate and the enthalpy per mole oxygen consumed was assumed constant. The convective heat transfer coefficients were determined on basis of the continuous measurements of the temperatures of both the lid and the bottom part of the reactor. The model allowed a satisfying prediction of the temperature of the composting material. In most cases, the mean absolute discard between the experimental and the simulated temperatures was inferior to 2.5°C and the peaks of temperature occurred with less than 8h delay. For the half of the experiments the temperature discard between the simulated peak and the experimental one was inferior to 5°C. On basis of the calculation of a stoichiometric production of water through oxidation of the biodegradable organic matter, the simulation of water going out from material as vapour also allowed a rather satisfying prediction of the mass of water in final mixture. The influence of the aeration rate on every type of heat loss was characterized. Finally, the model was used to evaluate the impacts on material temperature caused by the change of the insulation thickness, the ambient temperature, take the lid away, the increase or the decrease of the mass of waste to compost.     

Leaching studies for tin recovery from waste e-scrap

Printed circuit boards (PCBs) are the most essential components of all electrical and electronic equipments, which contain noteworthy quantity of metals, some of which are toxic to life and all of which are valuable resources. Therefore, recycling of PCBs is necessary for the safe disposal/utilization of these metals. Present paper is a part of developing Indo-Korean recycling technique consists of organic swelling pre-treatment technique for the liberation of thin layer of metallic sheet and the treatment of epoxy resin to remove/recover toxic soldering material. To optimize the parameters required for recovery of tin from waste PCBs, initially the bench scale studies were carried out using fresh solder (containing 52.6% Sn and 47.3% Pb) varying the acid concentration, temperature, mixing time and pulp density. The experimental data indicate that 95.79% of tin was leached out from solder material using 5.5M HCl at fixed pulp density 50g/L and temperature 90°C in mixing time 165min. Kinetic studies followed the chemical reaction controlled dense constant size cylindrical particles with activation energy of 117.68kJ/mol. However, 97.79% of tin was found to be leached out from solder materials of liberated swelled epoxy resin using 4.5M HCl at 90°C, mixing time 60min and pulp density 50g/L. From the leach liquor of solder materials of epoxy resin, the precipitate of sodium stannate as value added product was obtained at pH 1.9. The Pb from the leach residue was removed by using 0.1M nitric acid at 90°C in mixing time 45min and pulp density 10g/L. The metal free epoxy resin could be disposed-of safely/used as filling material without affecting the environment.     

Tissue distribution, isozyme abundance and sensitivity to chlorpyrifos-oxon of carboxylesterases in the earthworm Lumbricus terrestris

A laboratory-based study was conducted to determine the basal carboxylesterase (CbE) activity in different tissues of the earthworm Lumbricus terrestris, and its sensitivity to the organophosphate (OP) pesticide chlorpyrifos-oxon (CPx). Carboxylesterase activity was found in the pharynx, crop, gizzard, anterior intestine, wall muscle and reproductive tissues of L. terrestris, and multiple tissue-specific isozymes were observed by native gel electrophoresis. Esterase activity and sensitivity to CPx inhibition varied on a tissue- and substrate-specific basis, suggesting isoforms-specific selectivity to OP-mediated inhibition. Three practical issues are recommended for the use of earthworm CbE activity as a biomarker of pesticide exposure: (i) CbE should be measured using several routine substrates, (ii) it should be determined in selected tissues instead of whole organism homogenate, and (iii) earthworm CbE activity should be used in conjuncture with other common biomarkers (e.g., ChE) within a multibiomarker approach to assess field exposure of OPs, and potentially other agrochemicals.     

An Aquifer Vulnerability Assessment of the Paluxy Aquifer, Central Texas, USA, Using GIS and a Modified DRASTIC Approach

D epth to water, net Recharge, Aquifer media, Soil media, Topography, Impact of the vadose zone, and Conductivity of the aquifer). Using such an approach allows one to investigate the potential for groundwater contamination on a regional, rather than site-specific, scale. Based upon data from variables such as soil permeability, depth to water, aquifer hydraulic conductivity, and topography, subjective numerical weightings have been assigned according to the variable's relative importance in regional groundwater quality. The weights for each variable comprise a GIS map layer. These map layers are combined to formulate the final groundwater pollution potential map. Using this method of investigation, the pollution potential map for the study area classifies 47% of the area as having low pollution potential, 26% as having moderate pollution potential, 22% as having high pollution potential, and 5% as having very high pollution potential.     

Stormwater runoff and export changes with development in a traditional and low impact subdivision

Development continues at a rapid pace throughout the country. Runoff from the impervious surfaces in these watersheds continues to be a major cause of degradation to freshwater bodies and estuaries. Low impact development techniques have been recommended to reduce these impacts. In this study, stormwater runoff and pollutant concentrations were measured as development progressed in both a traditional development, and a development that used low impact development techniques. Increases in total impervious area in each watershed were also measured. Regression relationships were developed between total impervious area and stormwater runoff/pollutant export. Significant, logarithmic increases in stormwater runoff and nitrogen and phosphorus export were found as development occurred in the traditional subdivision. The increases in stormwater runoff and pollutant export were more than two orders of magnitude. TN and TP export after development was 10 and 1 kg ha(-1) yr(-1), respectively, which was consistent with export from other urban/developed areas. In contrast, stormwater runoff and pollutant export from the low impact subdivision remained unchanged from pre-development levels. TN and TP export from the low impact subdivision were consistent with export values from forested watersheds. The results of this study indicate that the use of low impact development techniques on a watershed scale can greatly reduce the impacts of development on local waterways.     

Isolated Spring Wetlands in the Great Basin and Mojave Deserts,USA: Potential Response of Vegetation to Groundwater Withdrawal

Desert springs, often the sole sources of water for wildlife and cattle, support wetland and wetland/upland transition ecosystems including rare and endemic species. In the basin and range province in Nevada, USA, springs in the Great Basin and Mojave deserts are sustained by interconnected deep carbonate and shallow basin-fill aquifers which are threatened by proposed groundwater withdrawal to sustain rapidly expanding urban areas, a common problem in arid regions worldwide. This paper draws on historic groundwater data, groundwater modeling, and studies of environmental controls of spring ecosystems to speculate on the potential effects of groundwater withdrawal and water table decline on spring-supported vegetation. The focus is on springs in the Great Basin and Mojave deserts representative of those that may be affected by future, planned groundwater withdrawal. Groundwater withdrawal is expected to reduce spring discharge directly through reduced flows from the shallow basin-fill aquifer or through reduction of the hydraulic head of the deep carbonate aquifer. This flow reduction will truncate the outflow stream, reducing the areal cover of wetland and wetland/upland transition vegetation. Lowering the local water table may also reduce the amount of upland phreatophytic vegetation by causing water levels to drop below plant rooting depths. Percolation of salts to surface soils may be reduced, eventually altering desert shrub cover from halophytes to nonhalophytes. The extent of these effects will vary among springs, based on their distance from extraction sites and location relative to regional groundwater flow paths. On-site monitoring of biotic variables (including cover of selected hygrophytes and phreatophytes) should be a necessary complement to the planned monitoring of local hydrologic conditions.