Long-term trends in the abundance of Mediterranean wetland vertebrates: From global recovery to localized declines

Biodiversity loss is unevenly distributed in space and time. Species have reached critically low population sizes in some areas, and remain abundant in others. Similarly, some species may benefit from successful conservation plans, while others still experience severe population depletions driven by negative impacts of human activities. Although several indicators have been proposed to measure the fate of biodiversity, they are generally only implemented globally so their relevance for regional assessment is still unclear. Here, we calculated the first regional trend in the Living Planet Index for the Mediterranean wetlands (Med LPI), an indicator that summarizes the fate of global biological diversity based on the temporal trends in abundance of vertebrate populations. The Med LPI was based on 1641 vertebrate populations of 311 species recorded in Mediterranean wetlands from 1970–2008, in 27 different countries. We investigated whether trends in the Med LPI differed between eastern and western Mediterranean countries, which have different socio-economic contexts. Finally, we assessed whether and how the trend in the Med LPI was robust to changes in the number and identity of species considered. We found that, at the Mediterranean scale, the Med LPI increased steeply, which could be taken at first sight, as a general recovery of wetland biodiversity in this biogeographical region. However, we found highly contrasting spatial trends within the Mediterranean region: the average trend was positive for western and negative for eastern countries. Moreover, we showed that depending on the method used to estimate the trend in Med LPI, it can be sensitive to the number and identity of the species considered. We suggest that understanding the regional discrepancies of the trend in biodiversity indicators as well as their robustness to the species represented in the index will enhance progress assessment towards global and regional conservation strategies.     

Elephant-induced structural changes in the vegetation and habitat selection by large herbivores in an African savanna

African elephants can affect the quality of the habitat of other species by breaking or uprooting trees and shrubs in savannas. Their effect on vegetation has been widely studied but less is known about the effects of such vegetation changes on other animals. We studied how changes in the vegetation caused by elephants influence the selection of microhabitats by five African herbivore species (giraffe, kudu, steenbok, impala, and zebra) in Hwange National Park, Zimbabwe. There was no clear significant effect of overall elephant-induced vegetation changes on microhabitat selection except for the small species (steenbok and impala) that used vegetation modified by elephants preferentially. This is consistent with a medium-term browsing facilitation hypothesis. More subtle possible effects were detected for larger browsers (giraffe and kudu). They selected areas with broken and uprooted plants and avoided coppiced areas. All of the browsers selected sites characterized by plants uprooted and broken by elephants, which were associated with a higher visibility, and ultimately a better probability of detecting an approaching predator, suggesting that perceived predation risk plays an important role in microhabitat selection. These results illustrate how elephants can initiate indirect effects that influence microhabitat selection by other herbivores. Understanding the indirect effects of elephants through changes in food availability and predation risk thus needs further investigation. The results of this study do not provide support for the hypothesis that elephant-induced changes in the structure of habitats have caused the declines in the populations of the other herbivores in the study area.     

Plant species traits regulate methane production in freshwater wetland soils

Ecosystem and biogeochemical responses to anthropogenic stressors are the result of complex interactions between plants and microbes. A mechanistic understanding of how plant traits influence microbial processes is needed in order to predict the ecosystem-level effects of natural or anthropogenic change. This is particularly true in wetland ecosystems, where plants alter the availability of both electron donors (e.g., organic carbon) and electron acceptors (e.g., oxygen and ferric iron), thereby regulating the total amount of anaerobic respiration and the production of methane, a highly potent greenhouse gas. In this study, we examined how plant traits associated with plant inputs of carbon (photosynthesis and biomass) and oxygen (root porosity and ferric iron on roots) to mineral soils relate to microbial competition for organic carbon and, ultimately, methane production. Plant productivity was positively correlated with microbial respiration and negatively correlated to methane production. Root porosity was relatively constant across plant species, but belowground biomass, total biomass, and the concentration of oxidized (ferric) iron on roots varied significantly between species. As a result the size of the total root oxidized iron pool varied considerably across plant species, scaling with plant productivity. Large pools of oxidized iron were related to high CO₂:CH₄ ratios during microbial respiration, indicating that as plant productivity and biomass increased, microbes used non-methanogenic respiration pathways, most likely including the reduction of iron oxides. Taken together these results suggest that increased oxygen input from plants with greater biomass can offset any potential stimulation of methanogenic microbes from additional carbon inputs. Because the species composition of plant communities influences both electron donor and acceptor availability in wetland soils, changes in plant species as a consequence of anthropogenic disturbance have the potential to trigger profound effects on microbial processes, including changes in anaerobic decomposition rates and the proportion of mineralized carbon emitted as the greenhouse gas methane.     

Measuring Eastern Redcedar (Juniperus virginiana L.) Mass With the Use of Satellite Imagery

Eastern redcedar (Juniperus virginiana L.) is an aggressively spreading native species in Oklahoma grasslands. It decreases rangeland forage production, and has been implicated in reducing stream flow and groundwater recharge. Industrial-scale plans to use redcedar as a biofuel source are being considered. Optimal placement of redcedar-based industries requires determination of redcedar availability. Such large-area inventories of redcedar mass can be practically addressed via aircraft or satellite remote sensing. Therefore, we conducted a study in central and western Oklahoma to develop and test a remote-sensing–based allometric equation relating redcedar canopy area to aboveground dry mass (AGM). We used automated methods to measure tree canopy area from georectified, pan-sharpened, multispectral QuickBird images having a spatial resolution of 0. 45 m² per pixel ground sample area. We also measured the canopy area and fresh and dry mass of these trees with the use of destructive sampling techniques. Regression analysis showed that satellite-derived measurements of canopy coverage explained about 85% of field-measured redcedar dry AGM in the study plots. The resulting allometric equation was applied to an independent data set, yielding dry AGM of 38.2 metric tons ? ha^?1, which was well within the field-measured range of 36–43 metric tons ? ha^?1. The allometric equation was then applied to Natural Resources Conservation Service measurements of redcedar canopy coverage for 17 counties in Oklahoma, to determine that the area of interest contains a median value of about 11.5 million metric tons of redcedar AGM. These results indicate that 0.45-m² spatial resolution multispectral imagery can be a useful tool for rapid and reliable measurement of redcedar dry AGM.     

Organic acid concentrations in soil solution: effects of young coniferous trees and ectomycorrhizal fungi

Organic acids may play a key role in rhizosphere and pedogenic processes. The effects of young trees and ectomycorrhizas on the soil solution concentrations of low molecular weight organic acids (LMWOAs) were studied in soil columns (E horizon) in the presence or absence of Pinus sylvestris and Picea abies with or without three ectomycorrhizal fungi. Several LMWOAs were identified at concentrations ranging from <0.1 to 11 μM. Compared to soil columns without tree seedlings, the presence of non-mycorrhizal or mycorrhizal tree seedlings sometimes resulted in small but statistically significant increases in citrate, formate, malonate and oxalate concentration. The general nutrient concentration and low P had little short-term effect on soil solution organic acid concentrations. The results suggest that biodegradation rather than production may be the major factor regulating soil solution organic acid concentrations.     

Creaming in black tea

Tea cream is the precipitate formed as tea cools. Its formation has been studied by X-ray scattering, and it is shown that a higher tea concentration leads to earlier onset of creaming and larger particles and that addition of theaflavin and calcium promotes creaming. Association constants between the major components of black tea have been obtained using NMR and show that calcium and glucose enhance the self-association of caffeine, polyphenols, and theaflavin but have little effect on hetero-association. Glycosylation of a polyphenol reduced self-association and reduced binding to caffeine. We conclude that theaflavin is important for the initiation of creaming, forming nanoclusters of typically 3 nm diameter, whereas caffeine acts more to fill in the gaps within the clusters and thus adds to the bulk of tea cream without being necessary for its initiation. Tea creaming may be reduced by increasing the solubility of the polyphenols (i.e., by glycosylation) or by removing calcium. Tea cream; theaflavin; caffeine; small-angle X-ray scattering; NMR; colloid.     

Hydroxylysyl pyridinoline cross-link concentration affects the textural properties of fresh and smoked Atlantic salmon (Salmo salar L.) flesh

A simple HPLC method is presented to quantify the low concentration of hydroxylysyl pyridinoline (PYD) cross-links in Atlantic salmon (Salmo salar L.) muscle. The method involved the extraction of tissue with NaOH prior to hydrolysis, which greatly reduced the amount of protein to be hydrolyzed and made downstream operations easier and more reproducible. The concentration of PYD was 426 pmol g(-)(1) dry mass muscle in post-rigor muscle stored at 0 degrees C and sampled 3 d after death. Hydroxproline (HYP) concentration was determined following NaOH extraction as a measure of collagen content. In post-rigor samples, the alkaline-insoluble HYP fraction comprised 18.3% of the total HYP. Scanning electron microscopy revealed shrinkage of muscle fibers and a retraction of the connective tissue matrix in smoked salmon. PYD concentration was relatively resistant to processing to the smoked product, decreasing by around 11.7%, as compared to a 22.2% decrease in HYP. There was a positive correlation between PYD concentration and the firmness of post-rigor muscle samples as measured by an instrumental texture analyzer, explaining 25% of the total variation. A weaker but still significant correlation was found between PYD concentration and firmness in the smoked product. There was no relationship between fillet firmness and total collagen concentration, although the correlation with HYP in the alkaline-insoluble fraction was significant at the 6% level (P = 0.057). Our results indicate that only 1-3% of collagen molecules are linked by nonreducible mature cross-links in harvest size farmed Atlantic salmon and that PYD concentration is an important raw material characteristic for flesh quality.     

Effect of organic manure and the endogeic earthworm Pontoscolex corethrurus (Oligochaeta: Glossoscolecidae) on soil fertility and bean production

A biofertilisation assay was conducted in Maripasoula (French Guiana), testing the effects of three different organic amendments (manioc peels, sawdust and wood charcoal) and the inoculation of the endogeic earthworm Pontoscolex corethrurus on pod production of Vigna unguiculata sesquipedalis and on soil chemical properties (pH, C, N, total and exchangeable P and K). Pod production was highest with manioc peels as available P increased in the soil. Wood charcoal also had a beneficial effect on pod production as it decreased acidity and increased the C:N ratio in the soil. In sawdust-amended soil, pod production did not differ from that in unamended soil. Inoculation of earthworms at a density of 80 sub-adults m^-2 did not significantly affect either pod production or soil nutrient content directly, although it increased the positive effect of manioc peels on pod production. Soil nutrient content, pod production and earthworm density at the end of the experiment were negatively correlated with soil moisture and positively with each other. Despite the strong effect of moisture, this assay demonstrated an interaction between the earthworm P. corethrurus and the legume V. unguiculata sesquipedalis mediated by soil nutrient content and organic matter inputs. We conclude that manioc peels improved soil P availability and were an interesting amendment for legume crops. We discuss also the effect of earthworm inoculation.     

Microparticle dispensers for the controlled release of insect pheromones

The potential utility of micrometer-sized particles as controlled-release devices for the volatilization of insect pheromones for mating disruption applications is evaluated in this study for two pheromone/model compound systems (codlemone/1-dodecanol and disparlure/1,2-epoxyoctadecane). To expedite the measurement of release rates from these particle devices, two techniques based on thermogravimetric analysis (TGA) have been exploited: isothermal TGA (I-TGA) at elevated temperatures (40-80 degrees C) with N(2) convection and volatilization temperature (VT) by dynamic TGA. A correlation between these two methods has been established. Samples that exhibit a higher VT provide a lower release rate from a particle substrate. Using these techniques, it has been demonstrated that chemical interactions between adsorbed liquids and particle surfaces may play a small role in defining release characteristics under conditions of low surface area, whereas parameters associated with total surface area and micropore structure appear to be much more significant in retarding evaporation for uncoated particles containing an adsorbed liquid. Additional regulation of release rates was achieved by coating the particle systems with water-soluble or water-dispersible polymers. By careful selection of particle porosity and coating composition, it is envisioned that the evaporation rate of pheromones can be tailored to specific insect control applications.     

Evaluating foliar nitrogen compounds as indicators of nitrogen status in Prunus persica trees

Mobile nitrogen (N) forms may be better N indicators of the N status of trees than total nitrogen (TN) due to their higher sensitivity to increasing N supply. A field experiment was carried out over a 3-year period to compare foliar concentrations of total N (TN), soluble N (SN), chlorophyll (Minolta SPAD readings), NH₄–N and NO₃–N as indicators of soil N availability in nectarine, Prunus persica L. Batsch, cv. ‘Fantasia’ (grafted on ‘Nemaguard’ peach, P. persica × P. davidiana) trees. Young trees were exposed to a range of fertilizer-N application rates. Based on correlation analysis, the best association between leaf N compounds with soil N supply and trunk diameter and/or fruit yield was obtained with TN and chlorophyll SPAD readings. Leaf concentrations of mobile N compounds (NH₄–N and NO₃–N) increased more than any other N compound under high N supply; however, their inconsistency among years and low leaf concentration difficult their use as N indicators. The optimum foliar TN for growth decreased with tree age, 4.4%, 3.6% and 3.3% in non-bearing 1-year-old trees, non-bearing 2-year-old trees and 3.3 fruit-bearing 3-year-old trees. The optimum SPAD readings were 40 in 2-year-old trees and 42 in 3-year-old trees. Stable N compounds (TN and chlorophyll SPAD) could be used to N diagnosis in the zone of N deficiency, and soluble N compounds (NH₄–N and NO₃–N) to diagnoses N excess.