Interactions Between Soil Erosion Processes and Fires: Implications for the Dynamics of Fertility Islands     

Sujith Ravi  Paolo D’Odorico  Travis E. Huxman  Scott L. Collins 《Strength and Conditioning Journal》2010,63(3):267-274

Shrub encroachment in arid and semiarid rangelands, a worldwide phenomenon, results in a heterogeneous landscape characterized by a mosaic of nutrient-depleted barren soil bordered by nutrient-enriched shrubby areas known as “fertile islands.” Even though shrub encroachment is considered as a major contributor to rangeland degradation, little is known about mechanisms favoring the reversibility of the early stages of this process. Here we synthesize the interactions between fires and soil erosion processes, and the implications of these interactions for management of rangelands. The burning of shrub vegetation develops relatively high levels of soil hydrophobicity. This fire-induced water repellency was shown to enhance the soil erodibility in and around burned shrub patches. The fire-induced enhancement of local-scale soil erosion results from changes in the interparticle bonding forces between the soil grains, thus altering the way moisture is retained in the soil. It has been shown—with a number of wind-tunnel studies, field-scale manipulative experiments, microtopographic measurements, and isotopic tracer studies—how the fire-erosion interactions affect the dynamics of fertility islands. Further we propose a new conceptual model of resource “island” dynamics that explains some of the findings previously reported in the literature on the interactions between aeolian processes and arid-land vegetation. In particular, we highlight the ability of fires to enhance the erodibility of nutrient-rich soils accumulated under the shrubs favoring the redistribution of soil resources, thereby contributing to the reversibility of the early stages of shrub encroachment.  相似文献   

Oxygen consumption and ammonia excretion of the freshwater crab Trichodactylus borellianus exposed to chlorpyrifos and endosulfan insecticides   总被引：1，自引：0，他引：1  

Marcela C. Montagna  Pablo A. Collins 《Pesticide biochemistry and physiology》2008,92(3):150-155

The effects of lethal and sublethal concentrations of chlorpyrifos and endosulfan on oxygen consumption and ammonia excretion rate of the crab Trichodactylus borellianus were evaluated. Oxygen consumption and energy expenditure had significant effect in relation to exposure times. Regarding endosulfan, a significant difference in consumption among times of exposure was registered in 625 μg L⁻¹. Moreover, at the highest concentration, energy expenditure rate was observed stabilized during 1-3 h. A significant increase in ammonia excretion was evidenced in 150 and 300 μg L⁻¹ of chlorpyrifos. The O:N ratio showed a decrease in chlorpyrifos and in 2500 μg L⁻¹ of endosulfan. This indicated a shift towards protein primary metabolism. An increment in the O:N ratio was observed in the lower endosulfan solutions. The relation oxygen:nitrogen showed a shift towards lipid and carbohydrate primary metabolism. This work indicated the complexity of the metabolism in the freshwater crab affected by xenobiotic elements.  相似文献   

Association of KASP markers with Hessian fly resistance in wheat of diverse origin     

Damian Collins  Livinus Emebiri  Mui-Keng Tan  Mustapha El Bouhssini  Ossie Wildman 《Euphytica》2018,214(8):144

Hessian fly (Mayetiola destructor (Say)) is a major pest in wheat producing areas of United States, Canada, Europe, and North Africa but has not been found in Australia. Host plant resistance is thought to involve a similar strategy used against plant pathogen, and in this study, we sought to investigate whether disease-resistance gene markers can also be useful in selecting against Hessian fly attack. The genome-wide association study involved 251 wheat genotypes of diverse origin and 72 SNPs, selected on the basis of significant similarity of their associated contig sequences to putative disease resistance genes. A novel statistical approach for genome-wide scan was applied, which utilised genotype data scored as Null alleles in the mixed model, instead of deleting or treating them as missing alleles. The analyses identified four markers with significant associations at the 5% level, after applying the false discovery rate. These were located on chromosomes 4A, 4B, 5A and 7D, with the 5A locus mapping to the cluster of major genes that confer resistance to multiple Hessian fly biotypes. Amongst the diverse wheat accessions analysed, most of the susceptible phenotypes carried the A–G–C–C haplotype at the BS00064369, BS00007416, BS00077047 and HfrDrd_nt_143 loci, respectively. When heterozygotes were excluded, all the Australian wheat accessions carried this allelic combination. The combination of alleles conferring resistance depended on the origin of the wheat accessions, with ICARDA accessions carrying a preponderance of the C–C–CG–T. Of the 11 USA accessions used for this study, only Lola carried a favourable combination of alleles for resistance at these loci.  相似文献   

Changes in Ghanaian farming systems: stagnation or a quiet transformation?     

Nazaire Houssou  Michael Johnson  Shashidhara Kolavalli  Collins Asante-Addo 《Agriculture and Human Values》2018,35(1):41-66

This research was designed to understand better the patterns of agricultural intensification and transformation occurring in Africa south of the Sahara using the Ghanaian case. The paper examines changes in farming systems and the role of various endogenous and exogenous factors in driving the conversion of arable lands to agricultural uses in four villages within two agro-ecologically distinct zones of Ghana: the Guinea Savannah and Transition zones. Using historical narratives and land-cover maps supplemented with quantitative data at regional levels, the research shows that farming has intensified in the villages, as farmers increased their farm size in response to factors such as population growth, market access, and changing rural lifestyle. The overall trend suggests a gradual move toward intensification through increasing use of labor-saving technologies rather than land-saving inputs—a pattern that contrasts with Asia’s path to its Green Revolution. The findings in this paper provide evidence of the dynamism occurring in African farming systems; hence, they point toward a departure from stagnation narratives that have come to prevail in the debate on agricultural transformation and intensification in Africa south of the Sahara. We conclude that it is essential for future research to expand the scope of this work, while policies should focus on lessons learned from these historical processes of genuine change and adaptation.  相似文献   

Prophylactic and therapeutic efficacy of Australian‐registered insecticide formulations against Old World screwworm (Chrysomya bezziana) infestation          下载免费PDF全文

PJ James  AH Wardhana  GW Brown  DG Mayer  R Urech 《Australian veterinary journal》2017,95(8):265-272

  相似文献   

Outbreaks of sarcoptic mange in free‐ranging koala populations in Victoria and South Australia: a case series          下载免费PDF全文

KN Speight  PL Whiteley  L Woolford  PJ Duignan  B Bacci  S Lathe  W Boardman  TF Scheelings  O Funnell  G Underwood  MA Stevenson 《Australian veterinary journal》2017,95(7):244-249

  相似文献   

Lidocaine or meloxicam analgesia decrease nociception as indicated by cardiovascular responses of halothane-anaesthetized Bos indicus bull calves during surgical castration     

H. Lehmann  G. Musk  M. Laurence  K. Bech-Gleerup  T. Collins  T. Hyndman  J. Tuke  C. Johnson 《Veterinary anaesthesia and analgesia》2017,44(1):195.e7

  相似文献   

Sarcoptic mange in badgers in the UK     

Collins R  Wessels ME  Wood R  Couper D  Swift A 《The Veterinary record》2010,167(17):668

  相似文献   

Comparison of infectivity of Eimeria tenella oocysts maintained at 4, 12 or 28°C for up to 10 months     

PJ JESTON  GW BLIGHT  GR ANDERSON  JB MOLLOY  WK JORGENSEN 《Australian veterinary journal》2002,80(1):91-92

  相似文献   

Validation of disease diagnoses reported to the National Animal Health Monitoring System from a large Colorado beef feedlot   总被引：1，自引：0，他引：1  

M D Salman  G R Frank  D W MacVean  J S Reif  J K Collins  R Jones 《Journal of the American Veterinary Medical Association》1988,192(8):1069-1073

Clinical observation and collection of biological specimens from a large beef feedlot (approximately 30,0000 animals) were used to evaluate 6 approaches for validation of a disease reporting system. Data collected during a 12-month period were used to evaluate each approach. A subsample of disease cases reported to the National Animal Health Monitoring System (NAHMS) was compared with the clinical observations of the investigators. Although the agreement between clinical diagnosis by the NAHMS veterinarian and by feedlot health crews was high, the sensitivity and specificity of specific diagnoses varied from 100 to 18% and from 99 to 76%, respectively, which suggests that regular clinical observations by a veterinarian are needed to validate disease diagnoses reported to NAHMS by producers. Subsampling of a group of cattle by means of paired serologic determination of antibodies to infectious bovine rhinotracheitis virus, bovine viral diarrhea virus, bovine respiratory syncytial virus, and parainfluenza-3 virus revealed a high serologic conversion rate to infectious bovine rhinotracheitis, and high levels of preexisting antibody to bovine respiratory syncytial and parainfluenza-3 viruses. It was concluded that the current method of data collection for Colorado feedlots provides an acceptable level of sensitivity and specificity for the program. However, disease events that are not of economic importance to the feedlot operator will be underestimated. If an objective of NAHMS is to develop a base line of animal health conditions, diagnosis of diseases by current methods will be satisfactory. Occasional validation through clinical observations by a veterinarian will suffice to monitor quality of collected data.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献