Oceanic core complexes at slow‐spreading ridges represent the uplifted footwalls of large‐offset ‘detachment’ faults that initiate at steep dips, and rotate to flatten via a ‘rolling hinge’ mechanism ...in response to flexural unloading. A key question is whether oceanic core complex development is accommodated entirely by displacement on the detachment fault zone, or if significant internal deformation of the footwall occurs during flexure and rotation. We investigate this by constraining the internal architecture of the Atlantis Massif oceanic core complex (Mid‐Atlantic Ridge, 30°N) using Formation MicroScanner borehole wall images and cores from the 1416 m‐deep Integrated Ocean Drilling Program Hole U1309D. Two distinct sets of structures are observed. N‐S‐striking, E‐dipping structures dominating the upper 385 m are interpreted as a brittle to semi‐brittle zone of fracturing in the footwall. Structures with this geometry occur down to 750 m below seafloor, suggesting that the detachment damage zone extends deep into the footwall. The nature of this deformation is, however, enigmatic: several cataclastic shear zones with reverse geometry in their current orientations may be rotated extensional faults or relate to shortening at the base of the flexing beam of a very weak footwall. By contrast, E‐W‐striking, N‐ and S‐dipping structures dominate the lowermost kilometer of the borehole. They likely represent conjugate fractures formed in the hanging wall of a late, E‐W normal fault zone, separating gabbroic rocks of the central dome of Atlantis Massif from serpentinized peridotite to the south, responsible for post‐detachment uplift of the southern margin of the massif.
Key Points
Provide insights into the structural architecture of an oceanic core complex
Determine the depth extent of detachment‐related deformation
Integrate unoriented core observations with fully oriented logging data
Between 1988 and 2007, set-aside, a European Commission production control measure, took an average of 10% of arable farmland in the EU out of production each year. In 2007, the set-aside rate was ...set to 0% and the scheme was later abandoned altogether. By assessing associations of farmland birds with set-aside and quantifying the extent of set-aside loss, this study aims to assess the implications of set-aside loss for farmland bird conservation. During the lifespan of set-aside, a large number of studies assessed the biodiversity value of set-aside and other agricultural crops and habitats. Where possible we considered measurable benefits of set-aside. However, some studies did not specify the type of set-aside and in some cases set-aside fields were grouped with cereal stubble fields. In these cases, we took the pragmatic approach of assessing the value of generic stubble fields as a conservative minimum estimate of the value of set-aside fields. A re-analysis of data from 30 intensive studies demonstrates that farmland bird densities tended to be higher on set-aside than on either cereal or oilseed rape crops. Without mitigation, these are the two crops likely to replace most set-aside fields. We estimate that 26-52% of the farmland populations of key granivorous passerines were present on stubble fields, giving an indication of the proportion of birds likely to be present on set-aside fields within this broader category. An extensive survey of lowland farmland during winters 1999/2000, 2000/2001 and 2002/2003, repeated in February 2008, showed a doubling of the number of 1-km squares with no stubble and a halving of the number of squares with more than 10 ha of stubble. After set-aside abandonment, 72% of squares had no stubble in the important late winter period, confirming that many of the former stubble fields were retained as set-aside. A simple correlative model suggests that this could cause a small increase in the rate of decline of Skylark Alauda arvensis and Yellowhammer Emberiza citrinella populations, assuming causal links between stubble area and demography. However, even if this assumption cannot be supported, these results clearly indicate that a significant proportion of some farmland bird populations will need to find alternative breeding and foraging habitats.
European farmland hosts a species assemblage of animals and plants which have undergone declines through the late twentieth and early twenty-first centuries, at least partly as a result of increased ...productivity. Further increases in human populations, changes in availability and cost of raw materials, policy constraints, price volatility and climatic changes will further drive greater efficiency and high yields in agriculture, with the risk of further adverse environmental impacts. We assess the effects of different management priorities (production-driven cropping vs. wildlife-friendly farming) at an arable farm in eastern England on food production, greenhouse gas (GHG) emissions and biodiversity. We modelled one actual and three alternative cropping scenarios using actual yields from the farm over 13 years, to calculate total yields and those foregone for agri-environmental measures. We measured crop yields, relative abundance of 19 farmland bird species, and CO
2
and N
2
O emissions related to crop production. Removing up to 10.5% of land from production coupled with a more diverse rotation (including legumes) resulted in a large increase in breeding birds (177%) and reduction of 9.4% in GHG emissions at the cost of 9.6% of food energy. Food protein lost was only 2.9%. A smaller increase in bird numbers of 50% could be achieved at a much smaller cost to yield (∼1.7% energy or protein) but with correspondingly smaller emissions reductions (1.2%). Results are discussed within the context of continued biodiversity loss to agriculture, increasing food demand and changing diets.
Increases in the intensity of the management of agricultural grasslands over the past 50 years have reduced plant species diversity in swards and increased uniformity in structure through changes in ...fertilizer regimes, grazing and mowing practices. These factors, as well as increased disturbance and trampling, have reduced the number and diversity of forbs and thus the diversity and abundance of invertebrates, in particular of foliar species. Associated with these changes in management, there has been a large decline in the abundance of many species of farmland birds in pastoral areas and more local extinctions compared with arable areas. To understand the impact of these management changes on bird populations, and design measures to reverse the declines, it is necessary to identify the key factors influencing bird usage of fields. We review results from five studies, which have related fertilizer and grazing management to bird usage of grass fields. Species that fed on soil invertebrates tended to show a positive response to the amount of nitrogen fertilizer added and increased grazing pressure, although there was a high degree of correlation between these two variables. In summer, many species, including corvids, Common Blackbird Turdus merula, Common Starling Sturnus vulgaris, Pied Wagtail Motacilla alba and Hedge Accentor Prunella modularis, showed a negative relationship with sward height, and in winter more species showed a positive relationship with bare ground. Taller sward heights are associated with a greater abundance and diversity of bird invertebrate food resources, and accessibility of food items or a lower risk of predation (actual or perceived) are likely to be the reasons for birds choosing to forage on shorter swards and in areas with more bare ground. Birds feeding on soil invertebrates were found to be generally tolerant of modern management practices that maintain short swards short, as accessibility to the soil has been increased. Species that feed on foliar invertebrates or forb seeds have been affected negatively by modern grassland agricultural practices.
Trichomonosis, caused by the protozoan Trichomonas gallinae, is an emerging infectious disease in finches, and is more commonly found in columbids and raptors. Infections can be sub-clinical or cause ...morbidity and mortality, but the parasite is currently only detectable by incubation of an oral swab. Here, we test whether T. gallinae parasites can be detected by PCR from faecal or non-cultured samples from the oral cavity and gastrointestinal tract of infected Turtle Doves (Streptopelia turtur). PCR did not detect T. gallinae parasites in any faecal samples screened, and in only 1 of 11 oral/gastrointestinal samples (from the mouth of a nestling suspected to have died from trichomonosis). We conclude that both oral swabs and parasite culture are still necessary to detect the sub-clinical presence of T. gallinae infection in birds.
Intensification of agriculture is believed to have caused declines in farmland bird populations. One of the key elements of recent agricultural intensification is the increased use of pesticides. ...However, studies elucidating relationships between individual management practices and responses in bird populations remain rare. Here, evidence is presented of indirect effects of pesticides on behaviour and nestling condition of yellowhammers (
Emberiza citrinella L.). Insecticide use was associated with reduced abundance of invertebrate food at the field scale resulting, early in the season (when nestlings were fed exclusively on invertebrates), in a negative correlation with yellowhammer foraging intensity. There was also a negative relationship between insecticide use and nestling body condition. While cumulative effects of repeated spraying can have impacts, the occurrence of any insecticide spraying in the breeding season may be more detrimental than multiple sprays at other times. Minimising applications of persistent broad-spectrum insecticides during March–June, the provision of alternative unsprayed foraging habitat and advice on mitigating indirect effects of pesticides to advisers and users are likely to benefit nesting yellowhammers.
Capsule Bird and seed abundances decreased in both standard and enhanced Agri-Environment Scheme seed mixtures (plots of seed-bearing crops) between November and February. Aims We analysed effects of ...Agri-Environment seed mixture type (‘standard’ or ‘enhanced’), plot age and non-target species on seed and bird abundance. Methods Surveys were conducted in November/December and January/February on 36 standard and 19 enhanced seed mixtures to test effect of plot type and age on abundance of buntings, finches and seeds. Results Bunting and finch densities decreased between January/February and November/December. Seed decreased by approximately 70% between surveys, plot type did not affect depletion. Second-year plots contained nearly 90% less seed, and non-significantly lower bunting and finch densities. Bunting densities were positively related to cereal seed abundance, and finch densities to non-cereal seed; these relationships did not differ between plot types. There was no evidence that non-target species affected use of seed mixtures by target species. Conclusion There was no evidence that plot type affected seed or bird abundances. Increased quality and uptake of Agri-Environment Scheme seed-rich habitats (seed mixtures and over-winter stubbles, possibly alongside well-implemented supplementary feeding) is needed to provide late-winter seed, especially cereals for species of conservation concern.
1. Yellowhammers began to decline on British lowland farmland in the late 1980s and losses are presently 10% per year. This study examined variation in the habitat selection and breeding success of ...yellowhammers, allowing an evaluation of whether Britain's yellowhammer decline might have been caused by recent changes in agriculture. 2. Yellowhammer territories were associated with hedgerows, vegetated ditches and wide uncultivated grassy margins around fields. Pasture and silage leys were avoided. Nests were built among herbaceous vegetation in ditches or in the shrubby vegetation of hedgerows. 3. Breeding started slightly earlier on organic farms than on intensively managed farms, but no measure of breeding success differed between farm types. Predation was the cause of most (64%) nest failures. A maximum of three breeding attempts (two successful) was observed per pair, with a mean clutch size of 3.3, a Mayfield nest success rate of 0.46, and 2.6 nestlings fledged per successful brood. These data, together with published estimates of adult yellowhammer survival and of post-fledging survival among other passerines, suggest that breeding productivity is too low to maintain a stable population. 4. The removal of hedgerows or abandonment of hedge management, filling or clearing of ditches, intensification of grassland management and cropping or grazing right up to the field edge, are all likely to have adversely affected yellowhammers on lowland farmland in southern England. Policy reforms that redirect subsidy support to environmentally beneficial management of field margin habitats and retention of winter-feeding sites such as stubbles should assist in restoring populations of breeding yellowhammers on lowland farmland. 5. Our data expand further the array of farmland bird species for which interactions between agricultural change and population change are increasingly understood.
Research has shown a close correlation between the decline of the UK Skylark Alauda arvensis population and the replacement of spring‐sown cereals with winter‐sown varieties, in which advanced sward ...development prevents successful multiple nesting attempts and reduces access for foraging. Widescale reversal of sowing times is unlikely for commercial reasons, so research has recently focused on ways of manipulating the sward structure of winter wheat to prolong access to nest‐sites and food. An RSPB pilot study investigated leaving small ‘undrilled patches’ in otherwise conventionally managed winter wheat crops. This option was later incorporated into a fully replicated experimental design, as part of the Sustainable Arable Farming For an Improved Environment (SAFFIE) project. This large consortium‐led project aims to test solutions for improving biodiversity within winter‐cereal‐dominated rotations. The experiment described here ran over 2002–3, with three field‐scale ‘treatments’ on 15 sites in the first year. The treatments compare (1) conventional winter wheat, (2) winter wheat sown in double‐normal width (25 cm) wide‐spaced rows (WSR) and (3) winter wheat with two 4‐m by 4‐m undrilled patches per hectare (UP). Results from the 2002 breeding season showed that undrilled patch treatments supported more breeding Skylarks for longer, most likely by aiding accessibility of food. WSR rows were little used by Skylarks and did not improve the abundance of favoured seed and invertebrate food items over conventional crops. Nesting performance and foraging patterns are discussed with reference to invertebrate food abundance and its accessibility, as determined by sward structure.
Conserving farmland birds is a key objective for agri-environment schemes (AES) across Europe, with a number of management options aimed at providing invertebrate food and nesting habitats. We ...analysed territory settlement by two widespread but declining farmland buntings with contrasting nesting requirements: the Yellowhammer Emberiza citrinella, a boundary-nesting species, and the Corn Bunting Emberiza calandra, a ground-nesting species. The study was conducted on farms participating in the English Higher Level Stewardship scheme to test whether territory settlement is influenced by the provision of key arable AES options. Both species settled preferentially in localities containing sown arable field margins, while Corn Bunting also settled in localities containing nectar flower mixtures. These preferences are likely to reflect foraging rather than nesting habitat requirements. Yellowhammer selected territories containing hedgerows under AES management, which are nesting rather than foraging habitat but may also provide food. Uptake by land owners of several AES options likely to provide limiting resources for farmland birds was very low, and because uptake at the landscape scale is also low, wider-scale population level benefits are likely to be constrained. However, this is one of few studies demonstrating selection of widely applied arable AES options by breeding farmland birds.
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