HARNESSING ECOLOGICAL PRINCIPLES AND PHYSIOLOGIC MECHANISMS IN DIVERSIFYING AGRICULTURAL SYSTEMS FOR SUSTAINABILITY: EXPERIENCE FROM STUDIES DEPLOYING NATURE-BASED SOLUTIONS IN SCOTLAND

To achieve the triple challenge of food security, reversing biodiversity declines plus mitigating and adapting to climate change, there is a drive to embed ecological principles into agricultural, value-chain practices and decisionmaking. By diversifying cropping systems at several scales there is potential to decrease reliance on inputs, provide resilience to abiotic and biotic stress,enhance plant, microbe and animal biodiversity, and mitigate against climate change. In this review we highligh...     

Suppressive ability of selected fodder plants on the growth of Parthenium hysterophorus

Parthenium hysterophorus is an invasive weed in Australian rangelands. It displaces valuable fodder plants and causes significant production losses within the cattle industry. Glasshouse screening trials were used to test 20 selected fodder species (test species) for their suppressive ability against P. hysterophorus growth. The trials used two planting densities (four or six plants per pot) and five planting frequencies. Each density by planting frequency was replicated three times. The dry shoot biomass of the test species was used to calculate a suppression index, in order to rank the relative suppressive abilities of the test plants. Setaria incrassata, Panicum maxicum and Cenchrus ciliaris were ranked as strongly suppressive, while Astrebla squarrosa, Bothriochloa pertusa, Themeda triandra, Astrebla elymoides, Bothriochloa decipens, Eulalia aurea and Lablab purpureus were moderately suppressive. The other test species had only poor suppressive abilities. A second glasshouse trial assessed the growth characteristics of the test plants at 13, 27 or 40 days after transplantation (DAT). Test species that strongly suppressed the growth of Parthenium hysterophorus had several attributes that included the ability to attain a greater height, the rapid production of tillers or a branched canopy and an extensive leaf area and root system; these growth attributes were present as early as 13 DAT. The present glasshouse screening approach identified several fodder species for further testing in field trials, and because the attributes that allow the test species to suppress Parthenium hysterophorus are present at the earliest stages of the plant’s life cycle, a rapid screening method is proposed that assesses these attributes at 27 DAT.     

Accuracy and precision of the continuous underway fish egg sampler (CUFES) and bongo nets: a comparison of three species of temperate fish

We examine the accuracy and precision of the continuous underway fish egg sampler (CUFES) relative to bongo nets based on the catch ratio of Atlantic cod (Gadus morhua), American plaice (Hippoglossoides platessoides), and cunner (Tautogolabrus adspersus). We derived expectation of catch ratios based on the application of a one-dimensional model of the vertical distribution of fish eggs applied to cod and on prior data on egg vertical distribution. Samples were collected in May and August 2001, two periods when the vertical structure of the water column differed substantially. Stationary CUFES collections did not yield significant differences in accuracy or precision relative to the underway CUFES. In May, when there was relatively little stratification, the CUFES-to-bongo catch ratio of cod and plaice eggs was well within expectations based on model predictions. In August, the CUFES-to-bongo catch ratios of cod and cunner were higher than expected. Generally, there was a greater proportion of early stage eggs in bongo than in CUFES samples, with the strongest differences in American plaice. The replicate variance of the CUFES was ∼25 times greater than that of the bongo nets, probably because of the large volumes sampled by bongo nets relative to the CUFES. Given that the CUFES provides greater accuracy in mapping but lower precision than bongo nets, multiple sampling gears may be the most effective method for surveying fish eggs of pelagic and demersal species.     

AIR AND WATER PERMEABILITY OF COMPACTED UNSATURATED COHESIVE SOIL

The air and water permeabilities of unsaturated cohesive soils have been measured in a modified triaxial cell permeameter which maintains separate continuity of both the air and water phases during permeation. Three different cohesive soils have been tested and the results interpreted in terms of the cluster concept of soil structure, which recognizes the existence of both macro- and micro-pores. Both air and water permeability are shown to be dominated by the geometry and degree of saturation of the intercluster macro-pores. Compression of the soil always reduces the air permeability but can increase the water permeability by increasing the membrane flow around the clusters. The relations between soil suction, occlusion of the air channels, and compaction water content have also been studied.     

Use of a Vascular Skeletal Muscle Graft for Canine Esophageal Reconstruction

A technique for reconstruction of the thoracic esophagus was evaluated in 13 dogs. A 9 x 10 cm section of transversus abdominis muscle was harvested, fashioned into a tubular graft, and vascularized via the greater omentum. The vascularized tube was advanced into the caudal thorax through the diaphragm at a second surgery 20 to 44 days after harvesting the section of the transversus abdominis muscle. A 5 cm section of caudal thoracic esophagus was replaced with the vascular tubular graft. One dog died because of incarceration of the intestine within the tube and two dogs were euthanized because of infected tubes. One dog died due to an anesthetic complication, one dog had a diaphragmatic hernia and died, and one dog died from pyothorax. Leakage of luminal contents at the anastomoses did not occur in any dog. Seven dogs survived both surgeries but showed deglutitory difficulty 6 days postoperatively due to the grafted esophageal segments becoming severely strictured in each case. Angiography demonstrated vascularization of the full thickness of the graft in each of the seven dogs. An unacceptably high incidence of infection and stricture formation made this technique unsuitable for clinical use.