Effects of area and isolation of woodland patches on herbaceous plant species richness across Great Britain

Richness of Ancient Woodland Indicator plant species was analysed in 308 woodland patches that were surveyed during the Countryside Survey of Great Britain carried out in 1998. The Countryside Survey recorded vegetation plots and landscape structure in 569 stratified 1 km sample squares and developed a remotely-sensed land cover map of the UK. Using these datasets, we tested the hypothesis that Ancient Woodland Indicator species richness in woodland fragments was limited by patch area, shape and spatial isolation and that woodland patches located in the lowland region of Great Britain would respond differently than those in the upland region. The variation in Ancient Woodland Indicator species richness in the British lowlands (n = 218) was mainly explained by patch area and two measures of connectivity, the length of hedgerows and lines of trees in the 1 km square and the area of woodland within 500 m of the vegetation plot. By contrast, variation in Ancient Woodland Indicator species richness in the British uplands (n = 90) was related to Ellenberg scores of the vegetation communities sampled – a surrogate for habitat quality – and no significant effect of spatial structure was detected. It therefore appears that the degree of fragmentation of woodland in the British lowlands limits the distribution of Ancient Woodland Indicator species, while in the uplands, failed colonisation is a matter of habitat quality rather than a result of landscape structure.This revised version was published online in May 2005 with corrections to the Cover Date.     

Microbial and microfaunal community structure in cropping systems with genetically modified plants

Soils from field sites at Foulum (DK), Narbons (FR) and Varois (FR) planted with genetically modified maize expressing either the insecticidal Bacillus thuringiensis protein (Bt) or herbicide tolerance (HT), as described elsewhere in this volume, were analysed for nematodes, protozoa and microbial community structure. These analyses were mirrored in single-species testing and in mesocosm experiments, and were coordinated with field samples taken for microarthropods, enchytraeids and earthworms so allowing for cross-comparison and a better understanding of the results observed in the field. Over the first 2 years of the field experiments (in 2002 and 2003), the effect of Bt-maize was within the normal variation expected in these agricultural systems. Sampling in 2004 and 2005 was expanded to include the effects of tillage (i.e. reduced tillage versus conventional tillage) and also the use of HT-maize. Tillage had major effects regardless of soil type (Varois or Foulum), with reduced-tillage plots having a greater abundance of microfauna and a different microbial community structure (measured both by phospholipid fatty-acid analysis (PLFA) and by community-level physiological profiling (CLPP)) from conventionally tilled plots. Grass, as a contrasting cropping system to maize, also had an effect regardless of soil type and resulted in greater microfaunal abundance and an altered microbial community structure. Differences in crop management, which for the Bt-maize was removal of the insecticide used to control European corn borer and for HT-maize was a change in herbicide formulation, were only tested at single sites. There were differences in microbial community structure (CLPP but not PLFA) and sporadic increases in protozoan abundance under the Bt-crop management. The HT-maize cropping system, which covered a shorter period and only one site, showed little change from the conventional system other than an altered microbial community structure (as measured by PLFA only) at the final harvest. The Bt-trait had a minimal impact, with fewer amoebae at Foulum in May 2003, fewer nematodes at Foulum in May 2004 but more protozoa at Varois in October 2002 and an altered microbial community structure (PLFA) at Foulum in August 2005. These were not persistent effects and could not be distinguished from varietal effects. Based on the field evaluations of microfauna and microorganisms, we conclude that there were no soil ecological consequences for these communities associated with the use of Bt- or HT-maize in place of conventional varieties. Other land management options, such as tillage, crop type and pest management regime, had significantly larger effects on the biology of the soil than the type of maize grown.     

Nutritional stress as a cause of thymic atrophy in broiler chickens

A study was conducted to examine the effect of nutritional stress on the development of the thymus, bursa, and pancreas of 7-to-14-day-old commercial meat-type chickens. One group of 7-day-old chickens was given access to food for only 30 minutes daily for 7 days. The birds were necropsied, and the thymus, pancreas, and bursa were compared with those of the control chickens fed ad libitum and necropsied at 7 and 14 days of age. The thymuses from birds on the restricted diet were atrophied (0.45 +/- 0.08 g) and congested compared with the thymuses from chickens fed ad libitum (1.32 +/- 0.31 g). The bursae from chickens on a restricted diet were also smaller (0.26 +/- 0.08 g) than the bursae from birds with free access to food (0.74 +/- 0.11 g). The restricted diet did not appear to cause any gross or histological pancreatic changes. The thymic lesions produced by nutritional stress were similar to those observed in the runting/stunting syndrome.     

Exencephaly in araucana chickens and silkie bantams

Exencephaly and hydranencephaly were diagnosed in two 6-week-old araucana chickens (Gallus domesticus) and one adult silkie bantam (Gallus domesticus). The chickens were presented with large, subcutaneous, cranial soft-tissue masses and exhibited neurological signs. There was partial aplasia of the frontal bones, resulting in herniation of the cerebral hemispheres.     

Patterns of solanidine glycoalkaloid variation in four gene pools of the cultivated potato

Patterns of variation for the solanidine-based glycoalkaloids have been determined for tuber material of genebank accessions of landraces of the cultivated potato and three closely-related wild species. Total levels were low in the cultivated taxa investigated,S. phureja, S. stenotomum, and the tetraploidS. tuberosum in its two formsS. tuberosum ssp.tuberosum andS. tuberosum ssp.andigena. The only solanidine-based glycolkaloids found in the tubers investigated in this study were-solanine and-chaconine, with one additional related compound, dehydrocommersonine, found in tubers of an accession ofS. canasense. The ratio of chaconine : solanine differed markedly from a mean of 0.98 inS. phureja to 2.28 in ChileanS. tuberosum ssp.tuberosum. The chaconine : solanine ratio was relatively constant within these two taxa, reflecting their relatively narrow genetic bases, but was much more variable within the taxa regarded as ancestral,S. stenotomum andS. tuberosum ssp.andigena. The wild speciesS. sparsipilum has been implicated in the origin of the tetraploid potato,S. tuberosum, but there was no support for this from the patterns of variation in chaconine : solanine ratio. The cline of chaconine : solanine ratios in cultivated potatoes along the spine of S. America does not appear to relate to the influence of local wild species through introgression, but may instead reflect differing selective pressures acting in different parts of the native range of the cultivated potato.     

Variations in the rates of nitrification and denitrification during the growth of potatoes (Solanum tuberosum L.) in soil with different carbon inputs and the effect of these inputs on soil nitrogen and plant yield

Summary A potato crop (Solanum tuberosum L. cv. Maris piper) was grown in a soil to which N was added, as NH₄NO₃, with or without added C, as sucrose or straw. Shortly after amendment the soil, in all treatments, contained only relatively low levels of mineral N. However, these levels increased later. The increase, which was greatest in the absence of added C and least with added sucrose, occurred before the emergence of the plant canopy. The addition of C to the soil had no effect on plant yield, measured either as dry matter or total N content. The potential nitrification rate was high early in the season, and decreased significantly as the plants developed. The potential denitrification rate showed two significant peaks in activity, possibly related to plant development, the first to the development of new roots and the second to root senescence. It seems probable that the amount of C released by the potato plants was only about one-quarter of that required for the maximum microbial activity.     

A qualitative multi-attribute model for assessing the impact of cropping systems on soil quality

An important goal of the European Commission-funded ECOGEN project is to develop a computer-based decision support system (DSS) for the assessment of economic and ecological impacts of using genetically modified crops. In ecological impact assessment, special emphasis is put on soil biology and estimating soil quality from the observed biological parameters. Methodologically, we have addressed this goal using model-based DSS, taking the approach of qualitative multi-attribute modelling. The approach is based on developing various hierarchical multi-attribute models that consist of qualitative attributes and utility (aggregation) functions, represented by decision rules. The model presented in this paper assesses the impact of cropping systems on soil quality and can subsequently be used to assess crop management options. It was developed as a collaboration between ECOGEN soil experts and decision analysts, and consists of 34 attributes, hierarchically structured into eight levels. There are 21 input attributes, most of which measure the richness and biomass of representative soil organisms. The assessment of soil quality is based on two main indicators: (1) soil diversity (assessed through microfauna, mesofauna and macrofauna richness) and (2) soil functioning (in terms of leaching, comminution, mineralisation and plant growth). In the paper, we address the methodological aspects of the model and its development, and describe the components of the model (attributes, value scales, decision rules and weights). We present initial results of its application to the assessment of crop management on soil quality in the case of using conventional and Bacillus thuringiensis (Bt)-maize at three field sites in France and Denmark. Our finding was that soil quality was unaffected even though several input attributes had changed. We also analyse the sensitivity of the model and discuss its current and potential contribution to soil quality management. The model is operational (available through a web page) and can be used for the assessment, comparison and analysis of realistic management scenarios. Furthermore, it provides an effective means of synthesising a lot of data, encoding knowledge about soil-quality factors, supporting communication among experts, answering ‘what-if’ and ‘so-what’ questions, and supporting the evaluation of new agricultural practices.     

The representation and functional composition of carabid and staphylinid beetles in different field boundary types at a farm-scale

At the farm-scale, hedgerow, degraded hedgerow and fence field boundary types were sampled for overwintering carabid and staphylinid beetles. Distinct beetle assemblages were evident and the structural and botanical characteristics of the boundary types were good explanatory factors of the differences. Each field boundary type supported unique species not found elsewhere; nine species were contributed by hedgerows alone and six species each from degraded hedgerows and fences. Using a systematic complementary site selection method we determined that all field boundary types were of equal importance for full representation of carabid and staphylinid species at the farm-scale. Additionally, fence habitats supported generalist predators of crop pests in greatest densities, whilst degraded hedgerows were most valuable in providing refuge to species vulnerable to disturbance and habitat fragmentation. Contrary to expectation, woodland species were not more evident in hedgerows than either degraded boundaries or fence habitat. This study provides empirical evidence that some components of biodiversity and sustainable farming are best maintained by retaining habitat heterogeneity, including features currently considered of limited conservation value.