Field Borders Provide Winter Refuge for Beneficial Predators and Parasitoids: A Case Study on Organic Farms

Semi-natural field borders are frequently used in midwestern U.S. sustainable agriculture. These habitats are meant to help diversify otherwise monocultural landscapes and provision them with ecosystem services, including biological control. Predatory and parasitic arthropods (i.e., potential natural enemies) often flourish in these habitats and may move into crops to help control pests. However, detailed information on the capacity of semi-natural field borders for providing overwintering refuge for these arthropods is poorly understood. In this study, we used soil emergence tents to characterize potential natural enemy communities (i.e., predacious beetles, wasps, spiders, and other arthropods) overwintering in cultivated organic crop fields and adjacent field borders. We found a greater abundance, species richness, and unique community composition of predatory and parasitic arthropods in field borders compared to arable crop fields, which were generally poorly suited as overwintering habitat. Furthermore, potential natural enemies tended to be positively associated with forb cover and negatively associated with grass cover, suggesting that grassy field borders with less forb cover are less well-suited as winter refugia. These results demonstrate that semi-natural habitats like field borders may act as a source for many natural enemies on a year-to-year basis and are important for conserving arthropod diversity in agricultural landscapes.     

Crystal structure of a photolyase bound to a CPD-like DNA lesion after in situ repair

DNA photolyases use light energy to repair DNA that comprises ultraviolet-induced lesions such as the cis-syn cyclobutane pyrimidine dimers (CPDs). Here we report the crystal structure of a DNA photolyase bound to duplex DNA that is bent by 50 degrees and comprises a synthetic CPD lesion. This CPD lesion is flipped into the active site and split there into two thymines by synchrotron radiation at 100 K. Although photolyases catalyze blue light-driven CPD cleavage only above 200 K, this structure apparently mimics a structural substate during light-driven DNA repair in which back-flipping of the thymines into duplex DNA has not yet taken place.     

Ultrasonographic examination of the forestomachs and the abomasum in ruminal drinker calves

Background

The study investigated the ultrasonographic appearance of the reticulum, rumen, omasum and abomasum of calves with ruminal drinking syndrome.

Methods

In ten milk-fed calves with ruminal drinking syndrome the reticulum, rumen, omasum and abomasum were examined by ultrasonography using a 5-MHz linear transducer before, during and after the ingestion of milk.

Results

The reticulum could be imaged in eight of ten calves before feeding. The reticular wall appeared as an echoic line, similar to mature cattle, and reticular folds were seen in eight calves. The reticular content appeared as echoic heterogeneous fluid. Reticular contractions were biphasic with 1.0 ± 0.38 contractions per minute. The rumen had a mean wall thickness of 2.1 mm dorsally, 3.5 mm at the level of the longitudinal groove, and 3.2 mm ventrally. The ventral sac of the rumen of all calves contained echoic heterogeneous liquid. During feeding the milk entering the rumen could be seen as hyperechoic liquid in five calves. The omasum was seen on the right side as a crescent-shaped line medial to the liver in seven calves. Only the omasal wall closest to the transducer was seen as an echoic line with a mean thickness of 2.7 mm. The ultrasonographic appearance of the omasum did not change during or after feeding. The abomasum was seen immediately caudal to the xyphoid on both sides of the midline before feeding. The mean length at the ventral midline was 22.2 cm. The ingesta were heterogeneous in all calves and the abomasal folds were distinct in eight. The mean lateral expansion of the abomasum from the ventral midline to the left and right varied from 8.7 to 13.8 cm and from 4.3 to 11.3 cm. The milk entering the abomasum was observed in all calves, and signs of milk clotting were seen in all calves 15 minutes after feeding.

Conclusion

This study showed that ultrasonography is useful for detecting milk in the reticulum and rumen of calves with ruminal drinking syndrome.     

Measurement of respiratory system compliance and respiratory system resistance in healthy dogs undergoing general anaesthesia for elective orthopaedic procedures

Objective The aim of this study was to investigate normal values for the dynamic compliance of the respiratory system (Crs) and respiratory system resistance (Rrs) in mechanically ventilated anaesthetized dogs.Study design Prospective clinical study.Animals Forty healthy dogs undergoing elective orthopaedic surgery. Body weight was (mean ± SD) 26.8 ± 10.7 kg (range: 1.9–45.0 kg), age 4.7 ± 2.9 years (range: 0.1–10.6 years).Methods Dogs were premedicated with acepromazine and methadone administered intramuscularly and anaesthesia induced with propofol intravenously. After endotracheal intubation the dog's lungs were connected to an appropriate breathing system depending on body weight and isoflurane in oxygen administered for maintenance of anaesthesia. The lungs were ventilated mechanically with variables set to maintain normocapnia (end‐tidal carbon dioxide concentration 4.7–6.0 kPa). Peak inspiratory pressure, Crs, Rrs, tidal volume, respiratory rate and positive end‐expiratory pressure were recorded at 5, 30, 60, 90 and 120 minutes after start of mechanical ventilation. Cardiovascular variables were recorded at time of collection of respiratory data.Results General additive modeling revealed the following relationships: Crs = [0.895 × body weight (kg)] + 8.845 and Rrs = [?0.0966 × body weight (kg)] + 6.965. Body weight and endotracheal tube diameter were associated with Crs (p <0.001 and p =0.002 respectively) and Rrs (p = 0.017 and p =0.002 respectively), body weight being linearly related to Crs and inversely to Rrs.Conclusion and clinical relevance Body weight was linearly related to Crs while Rrs has an inverse linear relationship with body weight in mechanically ventilated dogs. The derived values of Crs and Rrs may be used for monitoring of lung function and ventilation in healthy dogs under anaesthesia.     

Characterisation of the thermodormancy response in the everbearing strawberry ‘Everest’.

Summary

Temperature regimes that induce and ameliorate cropping troughs (“thermodormancy”) were evaluated over two seasons for the everbearing strawberry ‘Everest’. When plants were exposed to 26°C for 5, 10, 20 or 30 d in July, heat-induced troughs in cropping were observed in August. An important discovery was that cool (13°C) night temperatures ameliorated the severity of thermodormancy. In this study, thermodormancy appeared to be due principally to flower abortion post-anthesis, as large numbers of flowers emerged in mid-July, during the high temperature treatments, but went on to produce low fruit numbers in mid-August. Flower initiation itself (monitored by crown dissection) was not reduced by high temperatures. The observation that night-time temperature is critical for thermodormancy has significance for commercial production, in which protected cropping tends to increase average temperatures throughout the season, and venting tends to focus on day-time temperatures.     

Herbivore and pollinator responses to grassland management intensity along experimental changes in plant species richness

Agricultural intensification is a major driver of global environmental change. Disentangling the relative impact of losses in plant species richness and intensified management on higher trophic level organisms is important for conservation recommendations.We established different management regimes along an experimental gradient of plant species richness within “The Jena-Experiment” in Germany and quantified herbivory as well as grasshoppers and pollinators. Herbivory, grasshopper density and species richness and frequency of flower visiting pollinators were recorded two times in each of four subplots of altogether 80 plots differing in plant species richness. Each of the four subplots was subject to four different levels of fertilizer application and mowing to simulate very low, low, high and very high land use intensity.Fertilization and mowing significantly affected plant–herbivore interactions but plant species richness had no discernible effect. Grasshoppers were most abundant at high intensity subplots (3.1 individuals per m²) and least abundant on very low intensity subplots (1.3 individuals per m²). Leaf damage caused by herbivores was highest in even the very high intensity subplots (3.7%) with four mowing events per year and high amounts of fertilizer application and lowest on subplots with a low management intensity (2.4%) comprising two mowing events per year but no fertilizer application. In contrast, pollinators benefited most from lower management intensities, with only one or two mowing events and no fertilizer addition. In addition, higher numbers of flowering plant species and increased blossom cover was associated with enhanced pollinator species richness and flower visitation.Our results indicate that even in grasslands with high plant species richness, mowing and fertilization are more important drivers of herbivory and flower visitation by pollinators. Management with no more than two cuts per year and without fertilizer application in our grasslands balanced the ecosystem functions of increased pollination and decreased herbivory.