Effects of increasing landscape heterogeneity on local plant species richness: how much is enough?

Contemporary landscape ecology continues to explore the causes and consequences of landscape heterogeneity across a range of scales, and demands for the scientific underpinnings of landscape planning and management still remains high. The spatial distribution of resources can be a key element in determining habitat quality, and that in turn is directly related to the level of heterogeneity in the system. In this sense, forest habitat mosaics may be more affected by lack of heterogeneity than by structural fragmentation. Nonetheless, increasing spatial heterogeneity at a given spatial scale can also decrease habitat patch size, with potential negative consequences for specialist species. Such dual effect may lead to hump-backed shape relationships between species diversity and heterogeneity, leading to three related assumptions: (i) at low levels of heterogeneity, an increase in heterogeneity favours local and regional species richness, (ii) there is an optimum heterogeneity level at which a maximum number of species is reached, (iii) further increase in spatial heterogeneity has a negative effect on local and regional species richness, due to increasing adverse effects of habitat fragmentation. In this study, we investigated the existence of a hump-shaped relationship between local plant species richness and increasing forest landscape heterogeneity on a complex mosaic in the French Alps. Forest landscape heterogeneity was quantified with five independent criteria. We found significant quadratic relationships between local forest species richness and two heterogeneity criteria indicators, showing a slight decrease of forest species richness at very high heterogeneity levels. Species richness–landscape heterogeneity relationships varied according to the heterogeneity metrics involved and the type of species richness considered. Our results support the assumption that intermediate levels of heterogeneity may support more species than very high levels of heterogeneity, although we were not able to conclude for a systematic negative effect of very high levels of heterogeneity on local plant species richness.     

ULTRASONOGRAPHIC CHARACTERISTICS OF THE ABDOMINAL ESOPHAGUS AND CARDIA IN DOGS

Differential diagnoses for regurgitation and vomiting in dogs include diseases of the gastroesophageal junction. The purpose of this cross‐sectional study was to describe ultrasonographic characteristics of the abdominal esophagus and gastric cardia in normal dogs and dogs with clinical disease involving this region. A total of 126 dogs with no clinical signs of gastrointestinal disease and six dogs with clinical diseases involving the gastroesophageal junction were included. For seven euthanized dogs, ultrasonographic features were also compared with gross pathology and histopathology. Cardial and abdominal esophageal wall thicknesses were measured ultrasonographically for all normal dogs and effects of weight, sex, age, and stomach filling were tested. Five layers could be identified in normal esophageal and cardial walls. The inner esophageal layer was echogenic, corresponding to the cornified mucosa and glandular portion of the submucosa. The cardia was characterized by a thick muscularis, and a transitional zone between echogenic esophageal and hypoechoic gastric mucosal layers. Mean (±SD) cardial wall thicknesses for normal dogs were 7.6 mm (±1.6), 9.7 mm (±1.8), 10.8 mm (±1.6), 13.3 mm (±2.5) for dogs in the <10 kg, 10–19.9 kg, 20–29.9 kg and ≥30 kg weight groups, respectively. Mean (±SD) esophageal wall thicknesses were: 4.1 mm (±0.6), 5.1 mm (±1.3), 5.6 mm (±1), and 6.4 mm (±1.1) for the same weight groups, respectively. Measurements of wall thickness were significantly correlated with dog weight group. Ultrasonography assisted diagnosis in all six clinically affected dogs. Findings supported the use of transabdominal ultrasonography as a diagnostic test for dogs with suspected gastroesophageal disease.     

Quantifying and simulating carbon and nitrogen mineralization from diverse exogenous organic matters

The potential contributions of exogenous organic matters (EOMs) to soil organic C and mineral N supply depend on their C and N mineralization, which can be assessed in laboratory incubations. Such incubations are essential to calibrate decomposition models, because not all EOMs can be tested in the field. However, EOM incubations are resource-intensive. Therefore, easily measurable EOM characteristics that can be useful to predict EOM behaviour are needed. We quantified C and N mineralization during the incubation of 663 EOMs from five groups (animal manures, composts, sewage sludges, digestates and others). This represents one of the largest and diversified set of EOM incubations. The C and N mineralization varied widely between and within EOM subgroups. We simulated C and N mineralization with a simple generic decomposition model. Three calibration methods were compared. Individual EOM calibration of the model yielded good model performances, while the use of a unique parameter set per EOM subgroup decreased the model performance, and the use of two EOM characteristics to estimate model parameters gave an intermediate model performance (average RMSE-C values of 32, 99 and 65 mg C g⁻¹ added C and average RMSE-N values of 50, 126 and 110 mg N g⁻¹ added N, respectively). Because of the EOM variability, individual EOM calibration based on incubation remains the recommended method for predicting most accurately the C and N mineralization of EOMs. However, the two alternative calibration methods are sufficient for the simulation of EOMs without incubation data to obtain reasonable model performances.     

Accuracy of asymmetry indices of ground reaction forces for diagnosis of hind limb lameness in dogs

OBJECTIVE: To determine the accuracy of asymmetry indices of ground reaction forces (GRF) for diagnosis of hind limb lameness in dogs. ANIMALS: 36 healthy dogs and 13 dogs with naturally acquired cranial cruciate ligament rupture or hip dysplasia. PROCEDURES: Lameness for affected dogs ranged from not detectable to minor and constant. While dogs trotted on an instrumented treadmill, GRF variables were recorded and analyzed with asymmetry indices. Each index was tested for its ability to discriminate between healthy and affected dogs. Combinations of several indices were also assessed. RESULTS: Vertical force variables had better accuracy than craniocaudal force variables. Peak vertical force was the most accurate variable. Partial asymmetry during trotting was detected in healthy dogs. A multivariate approach that used peak vertical force and maximal rising slope yielded the optimum combination to distinguish between healthy and affected dogs. In addition, sensitivity of 92% or specificity of 95% may be achieved with 2 cutoff values while simultaneously maintaining specificity or sensitivity, respectively, at > 85%. CONCLUSIONS AND CLINICAL RELEVANCE: Asymmetry indices of GRFs were accurate for detection of hind limb lameness in dogs. This is particularly relevant for study designs in which only a single gait evaluation is possible.     

HPTLC screening of taro hybrids (Colocasia esculenta (L.) Schott) with high flavonoids and antioxidants contents

Taro (Colocasia esculenta) is the tropical root crop species featuring the greatest flavonoids diversity. Their quantification is important for breeding programmes focusing on biofortification. This study aims at developing an HPTLC protocol to compare the flavonoids fingerprints of more than 1800 hybrids belonging to 24 full‐sib families and to select genotypes with high levels of antioxidants. Twenty different chemical markers were identified based on bands R_f and colour. Flavonoids differ among individuals both quantitatively and qualitatively. Marker ‘A’ yielded the strongest antioxidant response to DPPH, equivalent to the one with quercetin pure standard. Overall, 377 high flavonoids content (HFC) hybrids were selected from 14 different families. The mean corm weight of HFC hybrids always appeared higher than the mean corm weight of the family they belong to. This method allows unambiguous selection of HFC hybrids. It also contributes to taro genetic improvement for nutritional value and access to new markets and to strengthen corm tolerance to pests and diseases. It could be applied to other tropical root crop species.     

Effects of type of added salt and ionic strength on physicochemical and functional properties of casein isolates produced by electroacidification

A procedure developed for soybean protein precipitation which was based on electrodialysis was tested for the production of acid casein from reconstituted skim milk. In a previous paper, the performance of bipolar membrane electroacidification (BMEA) was evaluated under different conditions of ionic strength (micro(added) = 0, 0.25, 0.5, or 1.0 M) and added salt (CaCl(2), NaCl, or KCl) (1). The aim of this study, which is the complement of the work on evaluation of BMEA performance, was to evaluate the functionality of the protein isolates produced by BMEA and to compare the BMEA isolates to commercial isolates and an isolate produced by chemical acidification. It was not possible to show differences between the functional properties of isolates produced by BMEA, except at 1 M CaCl(2) micro(added), due to the variability of the isolates. However, the results showed that it is possible to obtain isolates similar to commercial isolates and that the addition of salt during the process does not induce variations in functional properties. From results on mineral concentrations, it appeared that the addition of monovalent cations did not influence the retention of monovalent or divalent cations in the BMEA isolates, while addition of divalent cations (CaCl(2)) influenced the retention of magnesium. According to previous results on evaluation of BMEA performances under different conditions of ionic strength and added salt, the difference observed for the BMEA isolate produced at 1.0 M CaCl(2) was confirmed.     

What factors influence the stem taper of <Emphasis Type="Italic">Eucalyptus</Emphasis>: growth,environmental conditions,or genetics?

• Introduction   

Stem taper equations have been widely used for volume estimation to varied top diameter limits or for biomass calculations. However, their main drawback is that specific calibration is often necessary for each species or clone, and accounting for genetic and environmental effects is often a challenge.