Grass production studies in the uplands of north-east Scotland 1. The effects of soil parent material, altitude and soil major group

Sites were established on good quality grass swards in areas representative of three of the most extensive soil parent materials in north-east Scotland and covering an altitudinal range of 260–460 m. Overall yields of herbage dry matter in 1975 were high, ranging from 6280 kg ha^-1 with no fertilizer to 9190 kg ha^-1 with an application of 100, 26 and 50 kg ha^-1 N, P and K respectively. Differences in production between parent material and altitude groupings were found to be associated with differences in major soils group and past land use, with long-enclosed brown earths outyielding podzols recently reclaimed from heather moorland by about 30% overall. Increasing inputs of fertilizer appeared to reduce the effects of soil and climatic conditions. Brown earths showed higher apparent recoveries of N fertilizer than did podzols.     

Habitat use by Thymallus thymallus in a chalk stream and implications for habitat management

Abstract Results of a number of studies on the interactions between grayling, Thymallus thymallus L., and its habitat in tributaries of the River Itchen, a chalk stream in Hampshire, southern England are reported. These include an investigation into the effect of riparian shading on T. thymallus growth and population density in relation to the development of in‐stream macrophyte cover, and the use of a multi‐point decoder system to record micro‐habitat use and preference of individual T. thymallus. In all stream sections, T. thymallus recruitment fluctuated greatly. Densities were generally low often restricting meaningful comparisons. However, where large differences occurred, wooded sections, with less aquatic macrophyte cover, generally had higher densities of T. thymallus. All age groups of T. thymallus (0+, 1+ and 2+) tended to occupy hard gravel substratum, both by day and by night in the autumn and winter, and used deeper and faster water with increasing age. The 1+ and 2+ groups were generally found in water 40–70‐cm deep with a velocity between 0.3 and 0.5 m s^?1, whilst the 0+ group showed a preference for shallower water with reduced velocity at night, particularly in the winter. The results are discussed in relation to habitat management where T. thymallus occur with other salmonids.     

A CASE FOR ASSESSING ALLOCASUARINA AND CASUARINA SPP. FOR USE IN AGROECOSYSTEM IMPROVEMENT IN SEMI-ARID AREAS WITH A FOCUS ON CENTRAL ANATOLIA,TURKEY

• Semi-arid ecosystems have been especially impacted by a long history of clearing, cropping and intensified grazing. • Selection of tree species for assessment for agroforestry needs to consider their utility and effectiveness in provision of ecosystem service, but also the wider consideration of preserving biodiversity. • Imperatives of agroecosystem services and biodiversity conservation (or restoration) will impact on species selection for agroforestry. • The potential of Allocasuarina and Casuarina for wider economic and ecosystem needs an endeavor to achieve demonstrable gains. Agroecosystems in water-limited contexts— Mediterranean, semi-arid and arid climatic zones—are too frequently degraded systems that will not provide the needed ecosystem services to ensure a future of sustainable agricultural production. The processes that have created this situation continue and are being accelerated by anthropogenic climate change. Increasing arboreal vegetation in these areas through agroforestry is an important strategy to conserve and improve their agroecosystems. Actinorhizal trees and shrubs in the Casurinaceae have a unique set of adaptations for heat and water stress, and/or infertile to hostile soils. Central Anatolia, Turkey is particularly at risk of increasing aridity and further degradation. Therefore, species of Allocasuarina and Casuarina have been evaluated for their potential use in agroecosystem improvement in semi-arid areas with a focus on Central Anatolia. Based on a semiquantitative environmental tolerance index and reported plant stature, eight species were identified as being of high (A. verticillata and C. pauper) to moderate (A. acutivalvis, A. decaisneana, A. dielsiana, A. huegeliana, C. cristata and C. obesa) priority for assessment, with none of these species having been adequately evaluated for agroforestry deployment in semi-arid agroecosystems in any context.     

Influence of dietary arginine and glycine content on thyroid function and growth of juvenile rainbow trout, Oncorhynchus mykiss (Walbaum)

Juvenile rainbow trout, held at 12°C on a 12 h light :12 h dark photocycle, were fed a constant ration (1 % of body wt day ^?1) of isonitrogenous and isoenergetic diets that varied in either arginine content (3.6-56.1 g kg^?1 dry matter; experiment 1), or glycine (3.3–118 g kg^?1 dry matter) and alanine (5.0-42.3 g kg^?1 dry matter) content (experiment 2). In experiment 1, the lowest dietary level of arginine depressed growth, feed efficiency, plasma l -thyroxine (T₄) and 3,5,3′-triiodo-l -thyronine (T₃) levels and hepatic T₄ 5’monodeiodinase (5'D) activity responsible for T₄-to-T₃ conversion. Over the dietary range of 7.1–56.1 g arginine kg^?1, there was no change in 5'D activity, despite an arginine stimulation of growth. The optimum level of arginine for growth was within the range of 14.1–28.1 g kg^?1 of the diet or 32–63 g kg^?1 of dietary protein. In experiment 2, an increase in dietary glycine level, at the expense of glutamic acid, increased 5'D activity without attendant elevation of the plasma T₃ level. The latter finding suggests that glycine also induced a compensatory increase in T₃ degradation rate. This may explain why the glycine-induced increase in 5'D activity was unaccompanied by any changes in growth indices. Alteration of dietary alanine content did not affect growth or thyroid function. We conclude that of the various dietary amino acids tested, only glycine led to a progressive stimulation of hepatic T₄ 5'D activity. However, because glycine likely enhanced T₃ degradation, no increases in plasma T₃ or growth indices were found. Glycine may serve as an advance signal that activates thyroid function immediately preceding or coincident with energy and nutrient (especially protein) intake. This, in turn, may improve the efficiency of nutrient absorption and/or post-absorptive anabolic events.     

The onset of downstream movement of juvenile Atlantic salmon, Salmo salar L., in a chalk stream

The downstream movements of wild Atlantic salmon, Salmo salar L., from their established feeding territories in the River Itchen, Hampshire, UK, were logged continuously over an 11-month period using a passive integrated transponder (PIT) antenna system. The time of these movements was then related to a number of monitored and calculated environmental parameters. Initial downstream movement of smolts in April was correlated with the onset of darkness, at which time salmon moved from their established feeding territories alone. No relationship was found between the number of smolts migrating and river flow or maximum daily water temperature. The timing of downstream movement of parr between October and March was random with regard to sunset and time of maximum daily water temperature, suggesting the environmental cue that initiates movement may be different outside the spring smolt period.