Modelling and valuing the environmental impacts of arable,forestry and agroforestry systems: a case study

The use of land for intensive arable production in Europe is associated with a range of externalities that typically impose costs on third parties. The introduction of trees in arable systems can potentially be used to reduce these costs. This paper assesses the profitability and environmental externalities of a silvoarable agroforestry system, and compares this with the profitability and environmental externalities from an arable system and a forestry system. A silvoarable experimental plot of poplar trees planted in 1992 in Bedfordshire, Eastern England, was used as a case study. The Yield-SAFE model was used to simulate the growth and yields of the silvoarable, arable, and forestry land uses along with the associated environmental externalities, including carbon sequestration, greenhouse gas emissions, nitrogen and phosphorus surplus, and soil erosion losses by water. The Farm-SAFE model was then used to quantify the monetary value of these effects. The study assesses both the financial profitability from a farmer perspective and the economic benefit from a societal perspective. The arable option was the most financially profitable system followed by the silvoarable system and forestry. However, when the environmental externalities were included, silvoarable agroforestry provided the greatest benefit. This suggests that the appropriate integration of trees in arable land can provide greater well-being benefits to society overall, than arable farming without trees, or forestry systems on their own.     

Engaging farmers in environmental management through a better understanding of behaviour

The United Kingdom’s approach to encouraging environmentally positive behaviour has been three-pronged, through voluntarism, incentives and regulation, and the balance between the approaches has fluctuated over time. Whilst financial incentives and regulatory approaches have been effective in achieving some environmental management behavioural change amongst farmers, ultimately these can be viewed as transient drivers without long-term sustainability. Increasingly, there is interest in ‘nudging’ managers towards voluntary environmentally friendly actions. This approach requires a good understanding of farmers’ willingness and ability to take up environmental activities and the influences on farmer behavioural change. The paper aims to provide insights from 60 qualitative farmer interviews undertaken for a research project into farmers’ willingness and ability to undertake environmental management, particularly focusing on social psychological insights. Furthermore, it explores farmers’ level of engagement with advice and support networks that foster a genuine interest, responsibility and a sense of personal and social norm to sustain high quality environmental outcomes. Two conceptual frameworks are presented for usefully exploring the complex set of inter-relationships that can influence farmers’ willingness to undertake environmental management practices. The research findings show how an in-depth understanding of farmer’s willingness and ability to adopt environmental management practices and their existing level of engagement with advice and support are necessary to develop appropriate engagement approaches to achieve sustained and durable environmental management.     

Secondary hypothyroidism following head trauma in a cat

An 18-month-old female neutered domestic short hair cat was examined because of marked polydipsia and stunted growth following head trauma when it was 8 weeks old. Diagnostic evaluation revealed hyposthenuric urine, low concentrations of thyroid hormone and undetectable thyroid stimulating hormone concentrations which did not rise following thyroid releasing hormone administration. Lateral radiographs of the left and right tibiae revealed incomplete mineralisation of the greater tubercle and open physis. An almost empty sella turcica and a greatly reduced pituitary were visible on magnetic resonance images of the brain. A presumptive diagnosis of secondary hypothyroidism and central diabetes insipidus following head trauma was made.     

Modeling hydrology, metribuzin degradation and metribuzin transport in macroporous tilled and no-till silt loam soil using RZWQM

Due to the complex nature of pesticide transport, process-based models can be difficult to use. For example, pesticide transport can be effected by macropore flow, and can be further complicated by sorption, desorption and degradation occurring at different rates in different soil compartments. We have used the Root Zone Water Quality Model (RZWQM) to investigate these phenomena with field data that included two management conditions (till and no-till) and metribuzin concentrations in percolate, runoff and soil. Metribuzin degradation and transport were simulated using three pesticide sorption models available in RZWQM: (a) instantaneous equilibrium-only (EO); (b) equilibrium-kinetic (EK, includes sites with slow desorption and no degradation); (c) equilibrium-bound (EB, includes irreversibly bound sites with relatively slow degradation). Site-specific RZWQM input included water retention curves from four soil depths, saturated hydraulic conductivity from four soil depths and the metribuzin partition coefficient. The calibrated parameters were macropore radius, surface crust saturated hydraulic conductivity, kinetic parameters, irreversible binding parameters and metribuzin half-life. The results indicate that (1) simulated metribuzin persistence was more accurate using the EK (root mean square error, RMSE = 0.03 kg ha(-1)) and EB (RMSE = 0.03 kg ha(-1)) sorption models compared to the EO (RMSE = 0.08 kg ha(-1)) model because of slowing metribuzin degradation rate with time and (2) simulating macropore flow resulted in prediction of metribuzin transport in percolate over the simulation period within a factor of two of that observed using all three pesticide sorption models. Moreover, little difference in simulated daily transport was observed between the three pesticide sorption models, except that the EB model substantially under-predicted metribuzin transport in runoff and percolate >30 days after application when transported concentrations were relatively low. This suggests that when macropore flow and hydrology are accurately simulated, metribuzin transport in the field may be adequately simulated using a relatively simple, equilibrium-only pesticide model.     

Effects of guanidinoacetic acid supplementation on nitrogen retention and methionine flux in cattle

Creatine stores high-energy phosphate bonds in muscle and is synthesized in the liver through methylation of guanidinoacetic acid (GAA). Supplementation of GAA may therefore increase methyl group requirements, and this may affect methyl group utilization. Our experiment evaluated the metabolic responses of growing cattle to postruminal supplementation of GAA, in a model where methionine (Met) was deficient, with and without Met supplementation. Seven ruminally cannulated Holstein steers (161 kg initial body weight [BW]) were limit-fed a soybean hull-based diet (2.7 kg/d dry matter) and received continuous abomasal infusions of an essential amino acid (AA) mixture devoid of Met to ensure that no AA besides Met limited animal performance. To provide energy without increasing the microbial protein supply, all steers received ruminal infusions of 200 g/d acetic acid, 200 g/d propionic acid, and 50 g/d butyric acid, as well as abomasal infusions of 300 g/d glucose. Treatments, provided abomasally, were arranged as a 2 × 3 factorial in a split-plot design, and included 0 or 6 g/d of l-Met and 0, 7.5, and 15 g/d of GAA. The experiment included six 10-d periods. Whole body Met flux was measured using continuous jugular infusion of 1-¹³C-l-Met and methyl-²H₃-l-Met. Nitrogen retention was elevated by Met supplementation (P < 0.01). Supplementation with GAA tended to increase N retention when it was supplemented along with Met, but not when it was supplemented without Met. Supplementing GAA linearly increased plasma concentrations of GAA and creatine (P < 0.001), but treatments did not affect urinary excretion of GAA, creatine, or creatinine. Supplementation with Met decreased plasma homocysteine (P < 0.01). Supplementation of GAA tended (P = 0.10) to increase plasma homocysteine when no Met was supplemented, but not when 6 g/d Met was provided. Protein synthesis and protein degradation were both increased by GAA supplementation when no Met was supplemented, but decreased by GAA supplementation when 6 g/d Met were provided. Loss of Met through transsulfuration was increased by Met supplementation, whereas synthesis of Met from remethylation of homocysteine was decreased by Met supplementation. No differences in transmethylation, transsulfuration, or remethylation reactions were observed in response to GAA supplementation. The administration of GAA, when methyl groups are not limiting, has the potential to improve lean tissue deposition and cattle growth.     

Influences of hanging ratio,fishing height,twine diameter and material of bottom-set gillnets on catches of dusky flathead <Emphasis Type="Italic">Platycephalus fuscus</Emphasis> and non-target species in New South Wales,Australia

ABSTRACT:   Three experiments were done to test for the influences of different (i) hanging ratios (E = 0.5, 0.65 and 0.8); (ii) fishing heights (25 and 12 meshes); and (iii) twine diameters (0.41, 0.56 and 0.62 mm) and materials (multifilament nylon and multimonofilament nylon polyamide) on catches and by-catches in the estuarine gillnet fishery for Platycephalus fuscus in New South Wales, Australia. In each experiment, the various 100-m treatment panels comprising 80-mm (nominal) mesh rigged according to the different configurations being examined were configured in a single gang between 1090 and 1310 m in length, and fished according to commercial practices. The results showed no significant differences between different hanging ratios or twine diameters for the numbers, weights and size compositions of catches and by-catches. Twine material had an effect on only one key by-catch species ( Acanthopagrus australis ), with fewer caught in panels made from multifilament nylon compared with multimonofilament nylon. In contrast to the above modifications, lowering the fishing height of the floatline significantly reduced total by-catch by up to 46% and the individuals of key by-catch species ( Mugil cephalus , A. australis and Girella tricuspidata ) by between 60 and 85% with no effect on catches of targeted P. fuscus , or legally retained byproduct, Portunus pelagicus . The results are used to provide directions for the future management of this fishery and have relevance to other similar bottom-set gillnet fisheries.     

The effects of environmental change on the spatial and environmental determinants of community-level traits

An advantage of trait-based approaches to ecology is the ability to predict the response of a species assemblage to environmental change through trait–environment relationships. Because species assemblages are also known to be affected by spatial processes, variation in community-level traits may be similarly affected by spatial structure. Furthermore, the importance of spatial structure may vary with changes to the environment. Using a dataset describing a local stream fish assemblage and environmental variables, we examine the relative contribution of environmental and spatial factors in explaining variation in community-level traits across seasons. We also test for any spatial structuring of community-level traits. For most traits, seasonal environmental change did not seem to alter the relative importance of environmental factors. Traits that did not vary consistently with environmental variables across seasons exhibited significant spatial structure. Overall, relationships between traits and environmental variables seemed to operate on a continuum with ‘environmental traits’ (those that were strongly correlated with environmental variables in response to environmental change) at one end to ‘spatial traits’ (those that did not correlate with environments, but exhibited spatial structure) at the other. We suggest that the distinction between these types of traits is important, as different modeling approaches would be appropriate in using community-level traits to predict the response of species assemblages to environmental change.