排序方式： 共有13条查询结果，搜索用时 31 毫秒
1.
2.
Birds in woodland can be affected by increasing deer populations through changes to vegetation structure and potential impacts on foraging resources; these effects need to be better understood. Effects of deer browsing are reported from a replicated split-plot exclusion experiment in English coppiced woodland. All stages of growth were examined up to eight years after felling. We used standardised mist-netting (totaling 1920 h) to sample birds in breeding and post-breeding periods. Deer browsing strongly altered vegetation structure by reducing canopy cover and shrub layer foliage density. However deer did not affect invertebrate density per unit of foliage, providing no evidence of an ungulate-mediated plant chemical response affecting forage quality for invertebrate herbivores. At avian guild level, significantly more ground and understorey foraging birds were captured where deer were excluded, and negative responses to browsing were more marked for pooled migrants than pooled residents. At the species level, especially pronounced negative effects were evident for dunnock (Prunella modularis) and garden warbler (Sylvia borin); approximately five times more dunnocks were captured in deer exclosures than in browsed vegetation. We also detected negative responses to browsing by nightingale (Luscinia megarhynchos) and long-tailed tit (Aegithalos caudatus). No significant positive responses to browsing were detected. For some species the use of young re-growth increased post breeding relative to the breeding period, including a marked shift by pooled residents that involved a disproportionate number of juveniles. Previous studies in North America have shown that, through vegetation modification, ungulate activity can alter woodland bird assemblages; as far as we are aware this is the first experimental demonstration of effects in Europe, and at low to moderate browsing intensity typical of the wider landscape scale. 相似文献
3.
C. E. Dolman 《Canadian journal of veterinary research》1954,18(2):35-50
4.
OBJECTIVES: To investigate the beliefs of South African metropolitan adults regarding the importance of influencing cardiovascular health by eating certain food types, and to compare these beliefs between different race, living standards, age and gender groups. DESIGN: Randomised cross-sectional study. Trained fieldworkers administered questionnaires by conducting face-to-face interviews with consumers. SUBJECTS: Two thousand South Africans (16 years and older) were randomly selected from metropolitan areas in South Africa. The data were weighted to be representative of the total South African metropolitan population (N = 10 695 000) based on gender, age and race distribution. RESULTS: The majority (94 %) of the population indicated that it is important to influence cardiovascular risk-related health issues by eating certain food types, especially the higher LSM (Living Standard Measure) groups within the different race groups. Weight loss was considered the least important (61 % indicated that it is important) compared with cholesterol lowering (80 %), blood pressure (89 %), diabetes (86 %) and healthy blood vessels (89 %). In the higher LSM groups (7-10) higher proportions of respondents agreed than in the lower LSM groups (2 and 3). No differences were seen in responses between different gender, race and age groups.Conclusions and recommendationsThis study shows that the metropolitan South African adult population considers the influence on cardiovascular health by eating certain food types to be important. However, modifying weight loss by eating certain food types was considered less important. 相似文献
5.
F.J.W. Parmentier M.K. van der Molen R.A.M. de Jeu D.M.D. Hendriks A.J. Dolman 《Agricultural and Forest Meteorology》2009,149(6-7):1201-1208
The effect of shallow water table fluctuations on the evaporation and CO2 fluxes in a peatland is investigated. The fluxes of evaporation and net ecosystem exchange of carbon were measured from mid-spring to the end of summer in 2005 and 2006 and simulated independently with process models. The observed and modelled data were then compared along a gradient of water levels. Any variation along the gradient would imply an influence of the water table on the flux. It became evident that changes in the water table had no effect on the evaporation and CO2 fluxes of the peatland. A probable cause could be the high water content of the soil, even for the low water tables, and the stable thermal conductivity of the soil. This study has implications for current land use management, which is aimed at reducing CO2-emissions. Regulations are currently concerned with water table while this study shows that soil water content should be focused on as well. 相似文献
6.
Katherine L. Boughey Iain R. Lake Karen A. Haysom Paul M. Dolman 《Biological conservation》2011,(9):2300-2310
Although forest fragmentation can greatly affect biodiversity, responses to landscape-scale measures of woodland configuration in Europe have been examined for only a limited range of taxa. Almost all European bat species utilise woodland, however little is known about how they are affected by the spatial arrangement of woodland patches. Here we quantify landscape structure surrounding 1129 roosts of six bat species and a corresponding number of control locations across the UK, to examine associations between roost location and landscape composition, woodland proximity and the size of the nearest broadleaved woodland patch. Analyses are performed at two spatial scales: within 1 km of the roost and within a radius equivalent to the colony home-range (3–7 km). For four species, models at the 1 km scale were better able to predict roost occurrence than those at the home-range scale, although this difference was only significant for Pipistrellus pipistrellus. For all species roost location was positively associated with either the extent or proximity of broadleaved woodland, with the greatest effect of increasing woodland extent seen between 0% and 20% woodland cover. P. pipistrellus, Pipistrellus pygmaeus, Rhinolophus hipposideros, Eptesicus serotinus and Myotis nattereri all selected roosts closer to broadleaved woodland than expected by chance, with 90% of roosts located within 440 m of broadleaved woodland. Roost location was not affected by the size of the nearest broadleaved patch (patches ranged from 0.06–2798 ha ± 126 SD). These findings suggest that the bat species assessed here will benefit from the creation of an extensive network of woodland patches, including small patches, in landscapes with little existing woodland cover. 相似文献
7.
Europe's terrestrial biosphere absorbs 7 to 12% of European anthropogenic CO2 emissions 总被引：2，自引：0，他引：2
Janssens IA Freibauer A Ciais P Smith P Nabuurs GJ Folberth G Schlamadinger B Hutjes RW Ceulemans R Schulze ED Valentini R Dolman AJ 《Science (New York, N.Y.)》2003,300(5625):1538-1542
Most inverse atmospheric models report considerable uptake of carbon dioxide in Europe's terrestrial biosphere. In contrast, carbon stocks in terrestrial ecosystems increase at a much smaller rate, with carbon gains in forests and grassland soils almost being offset by carbon losses from cropland and peat soils. Accounting for non-carbon dioxide carbon transfers that are not detected by the atmospheric models and for carbon dioxide fluxes bypassing the ecosystem carbon stocks considerably reduces the gap between the small carbon-stock changes and the larger carbon dioxide uptake estimated by atmospheric models. The remaining difference could be because of missing components in the stock-change approach, as well as the large uncertainty in both methods. With the use of the corrected atmosphere- and land-based estimates as a dual constraint, we estimate a net carbon sink between 135 and 205 teragrams per year in Europe's terrestrial biosphere, the equivalent of 7 to 12% of the 1995 anthropogenic carbon emissions. 相似文献
8.
Shin’ichi Iida Takeshi Ohta Kazuho Matsumoto Taro Nakai Takashi Kuwada Alexander V. Kononov Trofim C. Maximov Michiel K. van der Molen Han Dolman Hiroki Tanaka Hironori Yabuki 《Agricultural and Forest Meteorology》2009,149(6-7):1129-1139
We measured evapotranspiration in an eastern Siberian boreal forest, in which the understory was cowberry and the overstory was larch, during the entire growing seasons of 2005 and 2006. We compared evapotranspiration from the understory vegetation above the forest floor EU with evapotranspiration from the whole ecosystem above the overstory canopy EO. The EU/EO ratio had a seasonal trend with a flat-bottomed U-shape during the growing season (4 May–30 September). High-EU/EO ratios at the beginning and end of the growing season were observed because larch, one of the two sources of EO, was a deciduous tree, while the understory was the evergreen cowberry. The mean daily EU values during the foliated period of larch (1 June–31 August) were 0.8 and 0.9 mm day?1, or 51.4 and 51.8% of EO in 2005 and 2006, respectively. The understory vegetation was one of the most important components of the hydrologic cycle in this forest. A significant amount of EU was caused by plant physiological control, due to the aerodynamic conductance, which was much larger than the surface conductance, leading to a smaller decoupling coefficient. We found that 71% of EU was caused by the vapour pressure deficit above the forest floor. 相似文献
9.
Landscape Ecology - Restoring landscape connectivity can mitigate fragmentation and improve population resilience, but functional equivalence of contrasting elements is poorly understood.... 相似文献
10.
Katherine L. Boughey Iain R. Lake Karen A. Haysom Paul M. Dolman 《Biological conservation》2011,(6):1790-1798
Within agricultural landscapes, linear features such as hedgerows and tree-lines provide valuable habitat for many species. We use data from 315 transects, completed as part of a national acoustic survey of bat distribution, to examine the incidence of four bat species adjacent to linear features in rural areas. The use of linear features was assessed in relation to hedgerow width, tree density, the presence of water and woodland proximity. To examine the effect of tree density, linear features were classified as either hedgerows without trees, hedgerows with sparse trees (comprising <50% tree canopy) or tree-lines (>50% tree canopy). The use of linear features by Pipistrellus pipstrellus was not affected by tree density; linear features of all types were associated with a similar increase in P. pipistrellus incidence. The use of linear features by Pipistrellus pygmaeus was dependent on both tree density and the proximity of woodland; only linear features containing trees provided an increase in P. pygmaeus incidence regardless of woodland proximity. P. pipistrellus and P. pygmaeus incidence was not affected by hedgerow width or the presence of water. Incidence of Nyctalus noctula and Eptesicus serotinus was unaffected by the density of linear features of any type. Many agri-environment schemes offer financial incentives for the creation and management of hedgerows. Optimising the biodiversity gain provided by linear features will maximise the effectiveness of these schemes. Agri-environment measures that encourage the provision and retention of hedgerow trees will benefit bats in agricultural landscapes. 相似文献