Bahiagrass crop coefficients from eddy correlation measurements in central Florida

Bahiagrass (Paspalum notatum) is a warm-season grass used primarily in pastures and along highways and other low maintenance public areas in Florida. It is also used in landscapes to some extent because of its drought tolerance. Bahiagrass can survive under a range of moisture conditions from no irrigation to very wet conditions. Its well-watered consumptive use has not been reported previously. In this study, bahiagrass crop coefficients (K _c) for an irrigated pasture were determined for July 2003 through December 2006 in central Florida. The eddy correlation method was used to estimate crop evapotranspiration (ET_c) rates. The standardized reference evapotranspiration (ET_o) equation (ASCE-EWRI standardization of reference evapotranspiration task committee report, 2005) was applied to calculate ET_o values using on site weather data. Daily K _c values were estimated from the ratio of the measured ET_c and the calculated ET_o. The recommended K _c values for bahiagrass are 0.35 for January–February, 0.55 for March, 0.80 for April, 0.90 for May, 0.75 for June, 0.70 for July–August, 0.75 for September, 0.70 for October, 0.60 for November, and 0.45 for December in central Florida. The highest K _c value of 0.9 in May corresponded with maximum vapor pressure deficit conditions as well as cloud free conditions and the highest incoming solar radiation as compared to the rest of the year. During the summer (June to August), frequent precipitation events increased the cloud cover and reduced grass water use. The K _c annual trend was similar to estimated K _c values from another well-watered warm-season grass study in Florida.     

Correlation between earthworms and plant litter decomposition in a tropical wet forest of Puerto Rico

Earthworms are recognized to play an important role in the decomposition of organic materials. To test the use of earthworms as an indicator of plant litter decomposition, we examined the abundance and biomass of earthworms in relation to plant litter decomposition in a tropical wet forest of Puerto Rico. We collected earthworms at 0–0.1 m and 0.1–0.25 m soil depths from upland and riparian sites that represent the natural variation in soils and decomposition rates within the forest. Earthworms were hand-sorted and weighed for both fresh and dry biomass. Earthworms were dominated by the exotic endogeic species Pontoscolex corethrurus Müller; they were more abundant, and had higher biomasses in the upland than in riparian sites of the forest. Plant leaf litter decomposed faster in the upland than riparian sites. We found that earthworm abundance in the upper 0.1 m of the soil profile positively correlated with decomposition rate of plant leaf litter. Ground litter removal had no effect on the abundance or biomass of endogeic earthworms. Our data suggest that earthworms can be used to predict decomposition rates of plant litter in the tropical wet forest, and that the decomposition of aboveground plant litter has little influence on the abundance and biomass of endogeic earthworms.     

Extinction and ecosystem function in the marine benthos

Rapid changes in biodiversity are occurring globally, yet the ecological impacts of diversity loss are poorly understood. Here we use data from marine invertebrate communities to parameterize models that predict how extinctions will affect sediment bioturbation, a process vital to the persistence of aquatic communities. We show that species extinction is generally expected to reduce bioturbation, but the magnitude of reduction depends on how the functional traits of individual species covary with their risk of extinction. As a result, the particular cause of extinction and the order in which species are lost ultimately govern the ecosystem-level consequences of biodiversity loss.     

Correction to: Individual based modelling of fish migration in a 2-D river system: model description and case study

Landscape Ecology - In the original publication of the article, the third author name has been misspelt. The correct name is given in this Correction. The original version of this article was revised.     

Characterization of starch morphology,composition, physicochemi-cal properties and gene expressions in oat

Starch is the major carbohydrate in oat(Avena sativa L.) and starch formation requires the coordinated actions of several synthesis enzymes. In this study, the granule morphology, composition and physicochemical properties of oat starch, as well as the expressions of starch synthesis genes were investigated during oat endosperm development. Under the scanning electron microscopy(SEM), we observed that the unique compound granules were developed in oat endosperms at 10 days post anthesis(DPA) and then fragmented into irregular or polygonal simple granules from 12 DPA until seed maturity. The amylose content, branch chain length of degree of polymerization(DP=13–24), gelatinization temperature and percentage of retrogradation were gradually increased during the endosperm development; whereas the distribution of short chains(DP=6–12) were gradually decreased. The relative expressions of 4 classes of 13 starch synthesis genes characterized in this study indicated that three expression pattern groups were significantly different among gene classes as well as among varied isoforms, in which the first group of starch synthesis genes may play a key role on the initiation of starch synthesis in oat endosperms.     

Effects of mercury on soil microbial communities in tropical soils of French Guyana

In gold mining regions, the risk of soil pollution by mercury is a major environmental hazard, especially in tropical areas where soil microflora plays a major part in soil functioning, major bio-geochemical cycles and carbon turn-over. The impact of mercury pollution on soil microflora should thus be carefully assessed in such environments while taking into consideration the specificities of tropical soils. The aim of this study was to compare the effects of mercury (0, 1 and 20 μg of inorganic mercury per gram of soil) on the functional diversity and genetic structure of microbial communities in a tropical soil. We investigated the effects of mercury on tropical soil microflora using soil microcosms spiked with mercury and incubated at 28 °C for 1 month. Microcosm flora, its biomass and its activity, as well as its functional and genetic structure, were followed by cultural methods, measures of respiration, ECOLOG plates, and DGGE (denaturing gel gradient electrophoresis), respectively. Fate of total and bioavailable mercury was estimated by CVAFS (cold vapor atomic fluorescence spectrometry). Results obtained for the microcosms enriched with only 1 μg g^?1 mercury were indistinguishable from controls. Conversely, in the presence of high mercury contents (20 μg g⁽¹), an immediate effect was measured on soil respiration, functional diversity (ECOLOG plates) and genetic structure (DGGE), although no significant effect was observed on plate counts or microbial biomass. In addition, whereas microbial activities (respiration and functional diversity) rapidly regained control values, a lasting effect of the high mercury concentration was observed on the genetic structure of the soil microbial community. These modifications took place during the first week of incubation when total mercury concentration was declining and bioavailable mercury was at its highest.This multiple approach study is one of the first attempts at investigating the effects of mercury on soil microbial communities in tropical soils. Our results demonstrate that in the tropical soil under study, mercury affects the soil microbial communities in a different manner than was previously reported in temperate soils. Furthermore, mercury toxicity on soil microbes may be modulated by typical tropical soil characteristics.     

Evaluation of a Midhumeral Block of the Radial,Ulnar, Musculocutaneous and Median (RUMM Block) Nerves for Analgesia of the Distal Aspect of the Thoracic Limb in Dogs

Objective: To evaluate a technique for midhumeral peripheral nerve blockade in the dog. Study Design: Cadaveric technique development; in vivo placebo‐controlled, prospective crossover study. Animals: Canine cadavers (n=38) and 8 clinically healthy, adult hound dogs. Methods: A technique for peripheral block of the radial, ulnar, musculocutaneous, and median nerves (RUMM block) was evaluated using cadaver limbs. Eight purpose‐bred, research dogs were anesthetized; a RUMM block was performed on each thoracic limb. One limb from each dog randomly received 0.5% bupivacaine and the opposite limb was assigned to receive sterile saline solution as a control. After recovery from anesthesia, skin sensation at selected dermatomes was evaluated for 24 hours using a mechanical stimulus. Weight‐bearing, conscious proprioception, and withdrawal reflex were also evaluated. One month after initial testing, each dog was reanesthetized and each limb received the opposite treatment. Results: Sensory thresholds were significantly increased over baseline measurements when compared with control limbs for all nerves. Complete sensory block was achieved in radial (15/16), ulnar (3/16), musculocutaneous (8/16), and median (11/16) nerves, using a mechanical stimulus of analgesia. Complete simultaneous block of all nerves was only obtained in 1 of 16 limbs. Conclusion: RUMM block resulted in desensitization of the skin in the associated dermatomes for 4–10 hours. Complete sensory block of the dermatomes supplied by the radial nerve was most consistent. Clinical Relevance: RUMM block may be an effective technique to provide adjunctive analgesia for dogs undergoing surgery of the distal aspect of the thoracic limb.     

Carbon monoxide toxicity: a case series

Objective: To describe diagnostics, therapy, and sequelae of acute carbon monoxide (CO) toxicity because of a motor vehicle generator in 4 dogs and 2 cats. Series summary: Four dogs and 2 cats presented for recumbency, disorientation, dyspnea, and stiffness after an estimated 6–8 hour exposure to exhaust from a generator. Diagnostics included a serum carboxyhemoglobin levels evaluation, arterial blood gas analysis, pulse oximetry readings, and blood pressure measurements. Initial therapy included oxygen (O₂) administration, intravenous bronchodilators, fluids, and a hemoglobin‐based O₂ carrying (HBOC) molecule. Following administration of the HBOC, 4 of the 6 animals showed dramatic clinical improvement. Two weeks after hospital discharge, the owner reported potential hearing deficits in all animals. Brain auditory evoked response (BAER) tests were conducted in all surviving animals and some degree of hearing impairment was documented in all cases, with complete clinical resolution noted 6 weeks later. Unique information provided: This report describes the therapeutic use of an HBOC in acute isolated CO toxicity (i.e. without the complications of smoke inhalation). In addition, delayed nervous system dysfunction was documented in all surviving animals.