Search

The success of conservation efforts on set-aside lands in the UK depends to a large extent on shifting its focus to different habitats in various kinds of locations. Results of a species-decline analysis, which reveal a decrease in rare plants in chalk grasslands and dwindling populations of butterflies and grasshoppers in heathlands, wet vegetation and woodland edges, can be used to formulate efficient methods of habitat conservation and management.

1 We investigated the role of non-native species (neophytes) in common British plant communities using botanical data from two stratified random surveys carried out in 1990 and 1998. 2 We found that from 16 851 plots surveyed in 1998 there were 123 non-native species found mostly in arable, tall grass/herb and fertile grassland habitats. Invasive non-native species, e.g. Fallopia japonica, Impatiens glandulifera and Rhododendron ponticum, were uncommon in this survey. 3 Between 1990 and 1998 the total number of non-native species increased but the mean number of species per sample plot decreased. The mean cover of non-natives increased from 1.2% to 1.9%. 4 There were positive spatial and temporal relationships between non-native and native species diversity. However, there was a weak negative relationship between changes in non-native cover and native diversity. 5 The species composition and ecological traits of communities containing non-natives were very different from those that did not contain them. 6 In the British countryside non-native species were mainly found in habitats with anthropogenic associations, high fertility, high number of ruderal species and high diversity. There is also an indication that successional shifts where competitive invasive species dominate involve non-native species. 7 National-scale changes in plant community composition are likely to be closely correlated with external land-use impacts. Changes such as eutrophication, nitrogen deposition and increased fertility in infertile habitats are likely to benefit both native and non-native invasive species; however, currently these trends benefit native species much more often than non-natives. 8 Non-native species are known to have significant effects on native species at local scales in many countries; however, at the landscape scale in Great Britain they are best considered as symptoms of disturbance and land-use change rather than a direct threat to biodiversity.

The extent to which conversion to organic farming influenced habitat diversity within less favored areas (LFAs) was determined. Similar numbers of conventional (not converted) (n = 16), recent converts (<5 years;n = 13) and long-standing converts (>5 years;n = 16) were surveyed. Each holding was characterized in terms of habitat classes using a rapid ground survey. Conversion to organic farming had little effect on overall habitat diversity. This could be linked to the physical challenges of farming in LFAs limiting management options. The results highlight the need for a separate evidence base for the development of policies relating to farming and biodiversity in marginal areas. [ABSTRACT FROM AUTHOR]

The UK Farm Scale Evaluations (FSE) compared the effects on biodiversity of management of genetically modified herbicide-tolerant (GMHT) crops and conventional crops over the shorter term. We simulated population changes over seven 4-year rotations (28 years) for weeds in crop rotations that included cereals and spring-sown GMHT and conventional oilseed rape and beet, using FSE data and assuming the continuation of the weed management systems practised in the FSE. The weed density dependence that was modelled integrated change caused by population dynamics and farmers’ responses to changes in weed density. Predicted weed seed populations decreased under conventional management and at a greater rate under GMHT. Total seed densities were lower for GMHT cropping by a factor of 0.7–0.8. The predicted distributions of weeds had more fields with lower weed densities under GMHT cropping. Such changes could affect animal populations on farmland, depending on the scale of uptake of GMHT crop cultivars. [ABSTRACT FROM AUTHOR]

The UK Farm-Scale Evaluations (FSE) compared the effects on biodiversity of management of genetically modified herbicide-tolerant (GMHT) spring-sown crops with conventional crop management. The FSE reported larger weed abundance under GMHT management for fodder maize, one of three crops studied. Increased seed production may be important for the long-term persistence of these arable weeds and may benefit invertebrates, small mammals and seed-eating birds. In three-quarters of FSE maize fields, growers used atrazine on the conventionally managed half, reflecting contemporary commercial practice. Withdrawal of the triazine herbicides atrazine, simazine and cyanazine from approved lists of EU chemicals could therefore reduce or even reverse the reported benefits of GMHT maize. Here we analyse effects of applications of triazine herbicides in conventional maize regimes on key indicators, using FSE data. Weed abundances were decreased greatly relative to all other regimes whenever atrazine was applied before weeds emerged. Here, we forecast weed abundances in post-triazine herbicide regimes. We predict weed abundances under future conventional herbicide management to be considerably larger than that for atrazine used before weeds emerged, but still smaller than for the four FSE sites analysed that used only non-triazine herbicides. Our overall conclusion is that the comparative benefits for arable biodiversity of GMHT maize cropping would be reduced, but not eliminated, by the withdrawal of triazines from conventional maize cropping. [ABSTRACT FROM AUTHOR]

Examines the responses of perennial grass Agrostis curtisii to elevated temperature and carbon dioxide. Patterns of ecotypic differentiation; Increase of shoot biomass; Dangers of extrapolating evolutionary plant responses to carbon dioxide from short-term experiments.

Examines the effects of Free-Air Carbon Dioxide Enrichment on experimental grassland communities. Measurement of plant biomass; Response of Lolium perenne to carbon dioxide fumigation; Use of meta-analysis.

Focuses on Agrostemma githago L., an annual herb with a strong tap root. Geographical and altitudinal distribution; Habitat; Communities; Response to biotic factors and management; Morphology; Biochemical data; Phenology; Viability of seeds.

Studies the effects of a range of densities of Bromus sterilis on the growth of winter wheat sown in pots containing soil from two fields at each of two locations in England. Emergence of B. sterilis on the heavy Oxfordshire soil; Different responses of the crop and weed on the clay soil caused by waterlogging.

Studies the variability in the relationship between crop yield and weed density for winter wheat and Bromus sterilis at two locations in Great Britain. Results of non-linear regression analysis; Variation in the effect of weed density on crop performance.

Analyzes the competition within two-species mixtures of plants. Estimation of survival, mean yield per plant and per unit area; Monoculture growing of Argostemma githago and Triticum aestivum; Competitive superiority of Avena fatua over Avena barbata.