Absence Of Plants Research Articles

Comparative study of Trichoderma gene expression in interactions with tomato plants using high-density oligonucleotide microarrays

Trichoderma spp. are widely used as biopesticides and biofertilizers to control diseases and to promote positive physiological responses in plants. In vitro and in vivo assays with Trichoderma harzianum CECT 2413 (T34), Trichoderma virens Gv29-8 (T87) and Trichoderma hamatum IMI 224801 (T7) revealed that these strains affected the growth and development of lateral roots in tomato plants in different ways. The early expression profiles of these Trichoderma strains were studied after 20 h of incubation in the presence of tomato plants, using a high-density oligonucleotide (HDO) microarray, and compared to the profiles in the absence of plants. Out of the total 34 138 Trichoderma probe sets deposited on the microarray, 1077 (3.15 %) showed a significant change of at least 2-fold in expression in the presence of tomato plants. The numbers of probe sets identified in the individual Trichoderma strains were 593 in T. harzianum T34, 336 in T. virens T87 and 94 in T. hamatum T7. Carbohydrate metabolism - the chitin degradation enzymes N-acetylglucosamine-6-phosphate deacetylase, glucosamine-6-phosphate deaminase and chitinase - was the most significantly overrepresented process commonly observed in the three Trichoderma strains in early interactions with tomato plants. Strains T7 and T34, which had similar positive effects on plant development in biological assays, showed a significantly overrepresented hexokinase activity in interaction with tomato. In addition, genes encoding a 40S ribosomal protein and a P23 tumour protein were altered in both these strains.

Calcium constrains plant control over forest ecosystem nitrogen cycling

Forest ecosystem nitrogen (N) cycling is a critical controller of the ability of forests to prevent the movement of reactive N to receiving waters and the atmosphere and to sequester elevated levels of atmospheric carbon dioxide (CO2). Here we show that calcium (Ca) constrains the ability of northern hardwood forest trees to control the availability and loss of nitrogen. We evaluated soil N-cycling response to Ca additions in the presence and absence of plants and observed that when plants were present, Ca additions "tightened" the ecosystem N cycle, with decreases in inorganic N levels, potential net N mineralization rates, microbial biomass N content, and denitrification potential. In the absence of plants, Ca additions induced marked increases in nitrification (the key process controlling ecosystem N losses) and inorganic N levels. The observed "tightening" of the N cycle when Ca was added in the presence of plants suggests that the capacity of forests to absorb elevated levels of atmospheric N and CO2 is fundamentally constrained by base cations, which have been depleted in many areas of the globe by acid rain and forest harvesting.

Hot spots for nitrous oxide emissions found in different types of permafrost peatlands

Recent findings on large nitrous oxide (N2O) emissions from permafrost peatlands have shown that tundra soils can support high N2O release, which is on the contrary to what was thought previously. However, field data on this topic have been very limited, and the spatial and temporal extent of the phenomenon has not been known. To address this question, we studied N2O dynamics in two types of subarctic permafrost peatlands, a peat plateau in Russia and three palsa mires in Finland, including also adjacent upland soils. The peatlands studied have surfaces that are uplifted by frost (palsas and peat plateaus) and partly unvegetated as a result of wind erosion and frost action. Unvegetated peat surfaces with high N2O emissions were found from all the studied peatlands. Very high N2O emissions were measured from peat circles at the Russian site (1.40±0.15 g N2O m−2 yr−1). Elevated, sparsely vegetated peat mounds at the same site had significantly lower N2O release. The N2O emissions from bare palsa surfaces in Northern Finland were highly variable but reached high rates, similar to those measured from the peat circles. All the vegetated soils studied had negligible N2O release. At the bare peat surfaces, the large N2O emissions were supported by the absence of plant N uptake, the low C : N ratio of the peat, the relatively high gross N mineralization rate and favourable moisture content, together increasing availability of mineral N for N2O production. We hypothesize that frost heave is crucial for high N2O emissions, since it lifts the peat above the water table, increasing oxygen availability and making it vulnerable to the the physical processes that may remove the vegetation cover. In the future, permafrost thawing may change the distribution of wet and dry surfaces in permafrost peatlands, which will affect N2O emissions.

Phosphorus and Nitrogen Fertilization Effect on Phosphorus Uptake and Phosphatase Activity in Ryegrass and Tall Fescue Grown in a Chilean Andisol

A series of short-term experiments were carried out to assess the effect of phosphorus (P) and nitrogen (ammonium [NH4+-N] or nitrate [NO3−-N]) fertilization on P uptake and phosphatase activity in ryegrass and tall fescue cultivated under greenhouse conditions. Ryegrass or tall fescue plants were grown in an acidic Andisol in the presence or absence of P and increasing doses of NO3−-N or NH4+-N fertilizers. At the end of the experiment, soil phosphatase activity (P-aseRhiz), pH, and Olsen-P were determined in the rhizosphere soil. Plant biomass, P uptake, and root surface phosphatase (P-aseRoot) were also assayed for both plant species. Furthermore, soil incubation experiments at increasing doses of P, NO3−-N, or NH4+-N were performed to evaluate the fertilizer effect on soil phosphatase activity (P-aseBulk) and microbial biomass carbon in the bulk soil. In the absence of plants, P-aseBulk was inhibited and microbial biomass carbon was raised at increasing P supply levels. In the greenhouse experiments, P uptake by tall fescue was about 67% higher than that of ryegrass at low soil P availability, which suggests that tall fescue was less sensitive to P deficiency than ryegrass. For both plant species, P-aseRhiz did not vary as a consequence of P addition. On the other hand, fertilization with the highest NH4+-N dose strongly decreased soil pH and shoot P content, as well as it increased P-aseRoot activity. This fact denotes that P-aseRoot behaved as a strategic response parameter to P stress with insufficient impact on plant P nutrition in both plant species.

Removal of antibiotics from urban wastewater by constructed wetland optimization

Seven mesocosm-scale constructed wetlands (CWs), differing in their design characteristics, were set up in the open air to assess their efficiency to remove antibiotics from urban raw wastewater. A conventional wastewater treatment plant (WWTP) was simultaneously monitored. The experiment took place in autumn. An analytical methodology including HPLC–MS/MS was developed to measure antibiotic concentrations in the soluble water fraction, in the suspended solids fraction and in the WWTP sludge. Considering the soluble water fraction, the only easily eliminated antibiotics in the WWTP were doxycycline (61 ± 38%) and sulfamethoxazole (60 ± 26%). All the studied types of CWs were efficient for the removal of sulfamethoxazole (59 ± 30–87 ± 41%), as found in the WWTP, and, in addition, they removed trimethoprim (65 ± 21–96 ± 29%). The elimination of other antibiotics in CWs was limited by the specific system-configuration: amoxicillin (45 ± 15%) was only eliminated by a free-water (FW) subsurface flow (SSF) CW planted with Typha angustifolia; doxycycline was removed in FW systems planted with T. angustifolia (65 ± 34–75 ± 40%), in a Phragmites australis-floating macrophytes system (62 ± 31%) and in conventional horizontal SSF-systems (71 ± 39%); clarithromycin was partially eliminated by an unplanted FW-SSF system (50 ± 18%); erythromycin could only be removed by a P. australis-horizontal SSF system (64 ± 30%); and ampicillin was eliminated by a T. angustifolia-floating macrophytes system (29 ± 4%). Lincomycin was not removed by any of the systems (WWTP or CWs). The presence or absence of plants, the vegetal species ( T. angustifolia or P. australis), the flow type and the CW design characteristics regulated the specific removal mechanisms. Therefore, CWs are not an overall solution to remove antibiotics from urban wastewater during cold seasons. However, more studies are needed to assess their ability in warmer periods and to determine the behaviour of full-scale systems.

Application of anifHmicroarray to assess the impact of environmental factors on free-living diazotrophs in a glacier forefield

Glacier forefield environments are exposed to extreme and fluctuating climatic and nutritional conditions. The high diversity of free-living diazotrophic communities found in these environments indicates that nitrogen fixers are able to efficiently cope with such conditions. In this study, a nifH microarray was used to monitor changes in diazotrophic populations in the field over a season, in the presence or absence of plants and in 2 glacier forefields characterized by a different bedrock type (siliceous or calcareous), as well as at different temperatures (10 °C, 15 °C) and under different nitrogen fertilization regimes (0, 10, 40 kg N·ha(-1)·year(-1)) in laboratory systems. Population structures responded highly dynamically to environmental changes. Plant presence had the strongest impact, which decreased toward the end of the season and with high amounts of nitrogen fertilization. Temperature and nitrogen fertilization increases indirectly affected diazotrophic communities through their positive impact on plant growth. These results indicate strong carbon limitation in young glacier forefield soils. Phylotypes related to the genus Methylocystis strongly responded to environmental variations. These methanotrophic microorganisms, which are able to retrieve nitrogen and carbon from the atmospheric pool, are particularly adapted to the extreme nutritional conditions found in glacier forefields.

Emergence and patterning of the five cell types of the Zea mays anther locule

One fundamental difference between plants and animals is the existence of a germ-line in animals and its absence in plants. In flowering plants, the sexual organs (stamens and carpels) are composed almost entirely of somatic cells, a small subset of which switch to meiosis; however, the mechanism of meiotic cell fate acquisition is a long-standing botanical mystery. In the maize ( Zea mays) anther microsporangium, the somatic tissues consist of four concentric cell layers that surround and support reproductive cells as they progress through meiosis and pollen maturation. Male sterility, defined as the absence of viable pollen, is a common phenotype in flowering plants, and many male sterile mutants have defects in somatic and reproductive cell fate acquisition. However, without a robust model of anther cell fate acquisition based on careful observation of wild-type anther ontogeny, interpretation of cell fate mutants is limited. To address this, the pattern of cell proliferation, expansion, and differentiation was tracked in three dimensions over 30 days of wild-type (W23) anther development, using anthers stained with propidium iodide (PI) and/or 5-ethynyl-2′-deoxyuridine (EdU) (S-phase label) and imaged by confocal microscopy. The pervading lineage model of anther development claims that new cell layers are generated by coordinated, oriented cell divisions in transient precursor cell types. In reconstructing anther cell division patterns, however, we can only confirm this for the origin of the middle layer (ml) and tapetum, while young anther development appears more complex. We find that each anther cell type undergoes a burst of cell division after specification with a characteristic pattern of both cell expansion and division. Comparisons between two inbreds lines and between ab- and adaxial anther florets indicated near identity: anther development is highly canalized and synchronized. Three classical models of plant organ development are tested and ruled out; however, local clustering of developmental events was identified for several processes, including the first evidence for a direct relationship between the development of ml and tapetal cells. We speculate that small groups of ml and tapetum cells function as a developmental unit dedicated to the development of a single pollen grain.

We All Gotta Go Sometime

​TremblingTrembling aspens (Populus tremuloides) are among the world's most remarkable trees, forming vast clones that can live an improbably long time. These clones share a common root system, from which new trees arise, cover up to 43 hectares and persist up to a million years. The vigor of these ancient plants belies their years, leading to speculation that they defy aging or senescence. But demonstrating senescence or its absence in plants that live longer than we do is tricky. Now, in new research reported in this issue of PLoS Biology, Dilara Ally, Kermit Ritland, and Sarah Otto have overcome this obstacle partly by using declining fertility as a proxy for senescence. A forest stand of aspen. Populus tremuloides, like many other clonal plants, is capable of growing and reproducing throughout its life. Because clonal plants continually renew themselves, the question raised by these organisms is: do they age? Aging is thought to be a byproduct of natural selection acting most effectively earliest in life. Because species typically reproduce early in life, they can accumulate mutations that are deleterious late in life without jeopardizing their production of offspring. In contrast, clonal plants can also grow and reproduce sexually throughout their lives, raising the question of whether they senesce as they get older. Ally and colleagues thought they might for two reasons. First, longer-lived clones have had more cell divisions, increasing the accumulation of mutations in their “body” (somatic) cells. Second, because plant reproductive cells come from somatic cells, plants can pass mutations from their shoots and roots on to their offspring. To investigate whether trembling aspens do senesce, Ally and colleagues asked if advanced age was linked to diminished fertility in clones. Age was estimated using a molecular clock, which was based on the amount of genetic diversity aspen clones had accumulated from the time since they were seeds. Aspen clones are either male or female, and fertility was based on the amount of viable pollen produced by male clones. To rule out the effects of environmental factors on fertility, the researchers accounted for influences such as disease, herbivory, and soil quality. The aspen clones studied ranged from roughly 70 to 10,000 years old, and pollen analysis revealed a slow but steady loss of fertility with age. Fertility was cut by more than three-quarters in the oldest clone and, based on extrapolation, would likely have dwindled away entirely by 20,000 years. Thus, though it may take millennia, even plants that grow indefinitely will eventually succumb to old age. Next the researchers investigated whether vegetative growth (asexual reproduction) comes at the expense of sexual reproduction in aspen clones. However, they found no evidence of tradeoffs between asexual and sexual reproduction. New shoots did not grow faster in aspen clones that were less fertile, older clones were not necessarily bigger than younger ones, and bigger clones were not less fertile than smaller ones. Alternative explanations for the age-related fertility drop include heritable epigenetic factors such as DNA methylation, which can affect reproductive functions from flowering to self-fertility. These findings show that male trembling aspen clones are at risk of extinction as they lose fertility with age, because without sex they cannot disperse and start new clones. This work also raises a number of intriguing questions. Do male and female aspen clones lose fertility at different rates? Previous work suggests they might: sperm transmit more deleterious mutations than do eggs. And do other plants that form clones also lose fertility as they get older? Such astonishingly long-lived plants are found around the world, in habitats from land to sea, and include the Tasmanian tree Lagarostrobos franklinii, the Mediterranean sea grass Posidonia oceanica, and the western US fungus Armillaria ostoyae. The researchers' technique of using molecular clocks to estimate clone age opens up the possibility of answering these questions for a variety of ancient clonal plants in the wild. Ally D, Ritland K, Otto SP (2010) Aging in a Long-Lived Clonal Tree. doi:10.1371/journal.pbio.1000454

Epiphytic Growth Habits of Chilean Gesneriaceae And the Evolution of Epiphytes Within the Tribe Coronanthereae1

Abstract Three monotypic and endemic genera of epiphytic Gesneriaceae (Gesnerioideae, Coronanthereae) occur in temperate rainforests of southern South America. In this article, intraspecific differences in rooted substrate and interspecific variation in epiphytic growth habits among these three Gesneriaceae species were assessed. The presence or absence of plants on the ground and main rooted substrate when growing epiphytically on trees were used to characterize epiphytic growth habits in two old-growth temperate rainforests of northern Chiloe Island (42°30′S) in Chile. An evolutionary interpretation based on reported phylogenies and morphologies within the Coronanthereae is proposed. Two species of Chilean Gesneriaceae, Mitraria coccinea Cav. and Asteranthera ovata (Cav.) Hanst., originate from the forest floor, then climb on trees while maintaining their main roots in the ground, and are classified as secondary hemiepiphytes. The third species, Sarmienta repens Ruiz & Pav., was found exclusively on tre...

Behavior and aquatic plants as factors affecting predation by three species of larval predaceous diving beetles (Coleoptera: Dytiscidae)

Predation among aquatic invertebrate predators can have important effects on patterns of exclusion and coexistence in aquatic habitats, especially if these predators also act as intraguild predators. Such patterns may be explained by variation in predator foraging mode and in the extent and overlap of habitat use. Predaceous diving beetles (Coleoptera: Dytiscidae) are abundant in isolated bodies of water and are effective predators on many aquatic organisms, including other dytiscids. The under-investigated role of hunting behavior and habitat use in altering outcomes of predation under different plant densities may offer insights into patterns of coexistence among larval dytiscids. I performed experiments that quantified behavior of larvae of three common genera of dytiscids that share common prey and then measured predation among genera in the presence or absence of aquatic plants. Behavioral analyses concluded that there were significant differences in foraging modes, with Dytiscus primarily exhibiting sit-and-wait tactics, Graphoderus engaging in active, open water searching, and Rhantus displaying combinations of these behaviors. Predation among larvae was common and occurred when predators were larger than the prey, with no indication of prey preference. Incidence of predation among generic combinations depended on the presence of plants and appeared to be related to behavioral differences among genera. The presence or absence of plants and differences in larval behavior may help to mitigate predation by reducing negative interactions in natural aquatic systems. These results have implications for IGP interactions and may be one of the explanations for the observed richness of this group of predators within aquatic habitats.

Effects of plant diversity on nutrient retention and enzyme activities in a full-scale constructed wetland

This study focused on the relationship between plant diversity (six species richness levels) and nutrient retention and enzyme activities associated with carbon, nitrogen and phosphorus cycling in a full-scale constructed wetland (CW) fed with post-treatment domestic wastewater. Effects of plant species richness on nutrient retention and enzyme activities were assessed using soil chemical and zymological methods, respectively. Retention of NH 4–N and NO 3–N in the wetland substrate increased with increasing species richness, while phosphorus retention significantly decreased under the richness level of 16 species per plot. Activities of enzymes such as dehydrogenase, β-glucosidase, invertase, phenol oxidase, l-arsparaginase, protease and nitrate reductase, while they were affected by plant species richness, were strongly depended on the presence or absence of plants in CW substrate, while activities of enzymes such as CM-cellulase, urease and acid phosphatase were strongly depended on plant species richness. We conclude that plant species richness influenced nutrient retention and enzyme activities in the substrate in our subtropical CW; increase plant species richness in CW will likely improve the efficiency of wastewater treatment.

Combined stabilization ponds–constructed wetland system

Abstract In a pre-existing wastewater treatment pilot plant consisting of three interconnected waste stabilization ponds –a facultative pond followed by two maturation/aerobic ones – and located in Sindos near Thessalonica, Northern Greece, we introduced eight vertical flow constructed wetlands, identical in couples, that differ in substrate and plant presence and are fed from the outflow of the first maturation pond. This resulted in the creation of a combined waste stabilization ponds–constructed wetland system, which was being monitored systematically for 2 years in order to study its operation. The unit was fed with septage. The monitored parameters were BOD5, pH, conductivity and TSS. This article presents the results obtained from the aforementioned unit, which are juxtaposed to results recorded in the literature for systems with similar characteristics, before focusing on the differences recorded in the results due to the different characteristics of the wetlands (different substrates, presence or absence of plants). To evaluate the system efficiency, results obtained from the constructed wetlands are compared to respective results recorded from the second maturation pond located in the unit, the inflow of which is the same as that of the wetlands. The constructed wetlands that were left unplanted were the ones which exhibited the highest BOD5 and TSS removal and the lowest conductivities.

Autologistic models with interpretable parameters

Ecologists are interested in characterizing succession processes, in particular monitoring the spread of invasive species and their effect on resident species. In situations for which binary response variables representing presence or absence of plants are observed over a spatial lattice, it may be desirable to use a model that accounts for the statistical dependence in the data, as well as the effect of potential covariates. One such model is the autologistic regression model. We show that the typical parameterization of the autologistic model presents difficulties in interpreting model parameters across varying levels of statistical dependence, and propose an alternative (centered) parameterization that overcomes this difficulty.We use the centered autologistic model to study the dynamics over time of two species, Rumex acetosella and Lonicera japonica, in an abandoned agricultural field in New Jersey, and compare the results to those obtained from using the traditional autologistic parameterization.

Amendment of an Acid Mine Soil with Compost and Polyacrylate Polymers Enhances Enzymatic Activities but may Change the Distribution of Plant Species

Many soils derived from pyrite mines spoils are acidic, poor in organic matter and plant nutrients, contaminated with trace elements, and support only sparse vegetation. The establishment of a plant cover is essential to decrease erosion and the contamination of water bodies with acid drainage containing large concentrations of trace elements. We tested the application of compost and polyacrylate polymers to promote the growth of indigenous plant species present in the mine area. Soil treatments consisted of unamended soil (control), soil with mineral fertilizers only, soil with fertilizer plus compost, soil with fertilizer plus polyacrylate polymers, and soil with fertilizer plus both amendments. Half of the soil was grown with Briza maxima L. (greater quaking grass), Chaetopogon fasciculatus (Link) Hayek (chaetopogon), and Spergularia purpurea (Persoon) G. Don fil. (purple sandspurry), while the remainder was left bare. In the absence of plants, the greatest improvements in soil conditions were obtained by the application of both amendments, which was associated with the greatest values of protease, acid phosphatase, and β-glucosidase, whereas the activity of cellulase and microbial respiration were similar in soil amended with compost or polymer. Dehydrogenase activity was greatest in soil with compost (with or without polymer), whereas urease activity was impaired by both amendments. In the presence of plants, the application of both amendments led to the greatest activities of protease, urease, β-glucosidase, cellulase, and microbial respiration, but acid phosphatase was mainly enhanced by polymer and dehydrogenase was increased by compost. Plant growth was stimulated in all treatments compared with unamended soil, but the greatest value for total accumulated biomass was obtained in fertilized soil receiving both amendments. However, species responded differently to treatment: while the growth of B. maxima was greatest in soil with compost and polymer, the growth of C. fasciculatus responded better to soil with compost, and S. purpurea grew better in polymer-amended soil. The amendments tested improved the quality of a mine soil and stimulated plant growth. However, botanical composition likely changes over time with amendments, and this needs to be considered when a large scale application of amendments is projected.

Effect of elevated CO 2 on soil N dynamics in a temperate grassland soil

The response of terrestrial ecosystems to elevated atmospheric CO 2 is related to the availability of other nutrients and in particular to nitrogen (N). Here we present results on soil N transformation dynamics from a N-limited temperate grassland that had been under Free Air CO 2 Enrichment (FACE) for six years. A 15N labelling laboratory study (i.e. in absence of plant N uptake) was carried out to identify the effect of elevated CO 2 on gross soil N transformations. The simultaneous gross N transformation rates in the soil were analyzed with a 15N tracing model which considered mineralization of two soil organic matter (SOM) pools, included nitrification from NH 4 + and from organic-N to NO 3 − and analysed the rate of dissimilatory NO 3 − reduction to NH 4 + (DNRA). Results indicate that the mineralization of labile organic-N became more important under elevated CO 2. At the same time the gross rate of NH 4 + immobilization increased by 20%, while NH 4 + oxidation to NO 3 − was reduced by 25% under elevated CO 2. The NO 3 − dynamics under elevated CO 2 were characterized by a 52% increase in NO 3 − immobilization and a 141% increase in the DNRA rate, while NO 3 − production via heterotrophic nitrification was reduced to almost zero. The increased turnover of the NH 4 + pool, combined with the increased DNRA rate provided an indication that the available N in the grassland soil may gradually shift towards NH 4 + under elevated CO 2. The advantage of such a shift is that NH 4 + is less prone to N losses, which may increase the N retention and N use efficiency in the grassland ecosystem under elevated CO 2.

Analysis of adenoviruses and polyomaviruses quantified by qPCR as indicators of water quality in source and drinking-water treatment plants

Three drinking-water treatment plants were analyzed for the presence of human adenoviruses (HAdV) and JC polyomavirus (JCPyV), previously suggested as viral contamination indicators, in order to define their water quality in relation to the presence of viral pathogens and the efficiency of the treatments applied. The 90% of the river water samples had positive results of HAdV (10 1–10 4 genome copies (GC)/L); and 48%, of JCPyV (10 0–10 3 GC/L). Lower concentrations of HAdV and JCPyV were found in different treatment steps of the plants in absence of bacterial standards. Virus removal efficiencies were higher than 5 logs in plants 1 and 3 and could be quantified as >2 logs in plant 2. However, three post-chlorinated samples from plants 2 and 3 (11%) were found to be positive for HAdV by qPCR, but did not show infectivity in the cell cultures assayed. Simple methods based on the adsorption–elution of viruses from glass wool give low-cost and efficient virus recovery from source water and large-volume water samples. Quantification of JCPyV and HAdV using qPCR is useful for evaluating virus removal efficiency in water treatment plants, identification of Hazard Analysis and Critical Control Points (HACCP) and as a molecular index of the virological quality of water. Though infectivity is not guaranteed when using qPCR techniques in water treated with disinfection processes, the quality of source water, where viruses have proved to have infective capabilities, and the removal efficiency of viral particles may be efficiently quantified.

Resilience of soil microbial activity and of amino acid dynamics to the removal of plant carbon inputs during winter

Many temperate agricultural soils have prolonged periods in the winter when plant carbon inputs to the soil are low. Soil maintained at low temperature in the absence of plants was used to simulate the conditions in a vineyard soil during winter. In a four month simulated overwintering period we showed that the concentration of dissolved organic carbon and nitrogen in soil solution slowly declined alongside heterotrophic soil respiration. Measurements of free amino acid concentrations and turnover indicated that the amino acid pool in soil was rapidly depleted but readily replenished throughout the four-month period. This indicates that the soil contained intrinsic reserves of labile C that was capable of supporting the soil microbial community in times of reduced plant C inputs.

A field study of constructed wetlands for preventing and treating acid mine drainage

The formation of acid mine drainage (AMD) from mine tailings is a severe environmental problem associated with tailings impoundments. The study evaluated the ability of wetlands built on tailings impoundments to prevent AMD formation and to treat already formed AMD, with special emphasis on the role of wetland plants in the remediation process. Four small-scale surface-flow wetlands of different designs, containing either mine tailings or sand, an inflow of AMD or unpolluted water, and with or without emergent plants ( Phragmites australis, Carex rostrata, and Eriophorum angustifolium), were constructed at the Kristineberg mine tailings impoundment in northern Sweden in 2004. Water samples were collected every month in 2006 at inflow and outflow in order to analyse metals, sulphate, pH, and redox potential. At the end of 2006, plant and sediment samples were collected to enable the analysis of metal concentrations. The concentrations of Fe, Zn, Cd, and sulphate and pH did not change after passage through the wetlands treating AMD. However, the Cu concentration decreased by 36–57%, with the decrease higher in the presence than in the absence of plants. The study of AMD prevention indicated that metal concentrations in impoundment water tend to decrease as the water passes through the wetland. However, sulphate concentrations increase and the pH decreases in the water, suggesting sulphide oxidation of the mine tailings. On the other hand, wetland plants increased the pH, decreased the redox potential, and increased the metal concentrations in the substrate, despite the fact that metal uptake in the studied wetland plants accounted for only 0.002–2.9% of the annual metal loading into the wetlands, suggesting that plants promote metal sedimentation and adsorption. Emergent plants and the wetlands constructed in this study were thus inadequate to treat the very harsh AMD at the Kristineberg mine site.

Sea lion Otaria flavescens as host of the common vampire bat Desmodus rotundus

We explored how the common vampire bat Desmodus rotundus is able to survive on hyper-arid rocky islands along the Peruvian coast in the absence of plants and terrestrial mammals. We used carbon and nitrogen stable isotope analyses on D. rotundus hairs and feces to assess the pri- mary source of food, and compared our results with field observations near D. rotundus colonies. Data from stable isotope analyses were consistent with field observations, indicating that D. rotundus feeds on the South American sea lion Otaria flavescens, and occupies the third trophic level in a chain linking anchovies Engraulis ringens, O. flavescens, D. rotundus and a hippoboscid fly, Trichobius parasiticus. Our report demonstrates the importance of marine-derived resources for D. rotundus along the Peruvian coast.

Inference of allelopathy is complicated by effects of activated carbon on plant growth

Allelopathy can play an important role in structuring plant communities, but allelopathic effects are often difficult to detect because many methods used to test for allelopathy can be confounded by experimental artifacts. The use of activated carbon, a technique for neutralizing allelopathic compounds, is now employed in tests for allelopathy; however, this technique also could produce large experimental artifacts. In three independent experiments, it was shown that adding activated carbon to potting media affected nutrient availability and plant growth. For most species tested, activated carbon increased plant biomass, even in the absence of the potentially allelopathic agent. The increased growth corresponded to increased plant nitrogen content, likely resulting from greater nitrogen availability. Activated carbon also affected nitrogen and other nutrient concentrations in soil media in the absence of plants. The observed effects of activated carbon on plant growth can confound its use to test for allelopathy. The detection of allelopathy relies on the difference between plant growth in medium with carbon and that in medium without carbon in the presence of the potentially allelopathic competitor; however, this difference may be biased if activated carbon alters soil nutrient availability and plant growth even in the absence of the focal allelopathic agent.