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Farmland
Kinds of Farmland Terms modified by Farmland Selected AbstractsThrushes now largely restricted to the built environment in eastern EnglandDIVERSITY AND DISTRIBUTIONS, Issue 4 2000Christopher F. Mason Abstract. ,I studied the distribution and density of three thrush populations, blackbird Turdus merula, song thrush T. philomelos and mistle thrush T. viscivorus, in an urban and contiguous rural area, totalling 2636 ha, in eastern England. Populations of these species are declining and I found 826, 85 and 30 territories of blackbird, song thrush and mistle thrush, respectively. Significantly more territories of all species than expected were within the urban boundary. Significantly more territories than expected were found of all three species in the built environment (residential housing, factories, schools, etc. with their associated gardens and green-space), urban and rural areas combined. Farmland occupied 67% of the study area but held significantly fewer blackbird and mistle thrush territories than expected, associated mainly with the small amount of grass; song thrushes were not recorded on farmland. Rural woodland and scrub held more blackbird and song thrush territories than expected. Song thrush was significantly associated with scrub within the urban boundary. With all three species largely absent from farmland, residential habitats can be considered as habitat refuges. The consequences of this for conservation and planning are discussed. [source] Rezoned for Business: How Eco-Tourism Unlocked Black Farmland in Eastern ZimbabweJOURNAL OF AGRARIAN CHANGE, Issue 4 2001David McDermott Hughes Eco-tourism is undermining black smallholders' entitlement to land in Zimbabwe. In the 1890s, British administrators restrained whites from alienating the whole of the country by demarcating native reserves. In terms of this limited aim, the policy of native reserves worked. It ensured a land base for black agriculture, particularly for women and children. In the late 1980s, however, CAMPFIRE (Communal Areas Management Programme for Indigenous Resources) invited the tourism industry to begin operations in the lowland reserves. These ?rms have claimed land, made money and relocated smallholders. Based on economic and ecological arguments, CAMPFIRE has rede ?ned the black entitlement as merely a claim competing with those of other ,stakeholders'. No guarantees exist for residents and cultivators. Indeed, government and NGOs are fast transforming the lowland reserves into privileged and subsidized investment zones. Held in check for a century, a new kind of settler colonialism is sweeping down from the highlands. [source] Land use and soil erosion in the upper reaches of the Yangtze River: some socio-economic considerations on China's Grain-for-Green ProgrammeLAND DEGRADATION AND DEVELOPMENT, Issue 6 2006H. L. Long Abstract Soil erosion in the upper reaches of the Yangtze River in China is a major concern and the Central Government has initiated the Grain-for-Green Programme to convert farmland to forests and grassland to improve the environment. This paper analyses the relationship between land use and soil erosion in Zhongjiang, a typical agricultural county of Sichuan Province located in areas with severe soil erosion in the upper reaches of the Yangtze River. In our analysis, we use the ArcGIS spatial analysis module with detailed land-use data as well as data on slope conditions and soil erosion. Our research shows that the most serious soil erosion is occurring on agricultural land with a slope of 10,25 degrees. Both farmland and permanent crops are affected by soil erosion, with almost the same percentage of soil erosion for corresponding slope conditions. Farmland with soil erosion accounts for 86·2,per,cent of the total eroded agricultural land. In the farmland with soil erosion, 22·5,per,cent have a slope of,<,5 degrees, 20·3,per,cent have a slope of 5,10 degrees, and 57·1,per,cent have a slope of,>,10 degrees. On gentle slopes with less than 5 degrees inclination, some 6,per,cent of the farmland had strong (5000,8000,t,km,2,y,1) or very strong (8000,15000,t,km,2,y,1) erosion. However, on steep slopes of more than 25 degrees, strong or very strong erosion was reported for more than 42,per,cent of the farmland. These numbers explain why the task of soil and water conservation should be focused on the prevention of soil erosion on farmland with steep or very steep slopes. A Feasibility Index is developed and integrated socio-economic assessment on the feasibility of improving sloping farmland in 56 townships and towns is carried out. Finally, to ensure the success of the Grain-for-Green Programme, countermeasures to improve sloping farmland and control soil erosion are proposed according to the values of the Feasibility Index in the townships and towns. These include: (1) to terrace sloping farmland on a large scale and to convert farmland with a slope of over 25 degrees to forests or grassland; (2) to develop ecological agriculture combined with improving the sloping farmland and constructing prime farmland and to pay more attention to improving the technology for irrigation and cultivation techniques; and (3) to carry out soil conservation on steep-sloping farmland using suggested techniques. In addition, improving ecosystems and the inhabited environment through yard and garden construction for households is also an effective way to prevent soil erosion. Copyright © 2006 John Wiley & Sons, Ltd. [source] Old Fields: Dynamics and Restoration of Abandoned FarmlandAUSTRAL ECOLOGY, Issue 5 2009EDDIE VAN ETTEN No abstract is available for this article. [source] Flying Foxes Prefer to Forage in Farmland in a Tropical Dry Forest Landscape Mosaic in FijiBIOTROPICA, Issue 2 2010Article first published online: 29 SEP 200, Matthew Scott Luskin ABSTRACT To test flying fox adaptations to a habitat mosaic with extreme deforestation, the abundance, habitat choice and feeding behavior of the Pacific flying fox, Pteropus tonganus, were investigated across 16 islands of the Yasawa archipelago, Fiji. The habitat mosaic is formed by 4.3 percent tropical dry forest and 3.3 percent farmland, leaving exotic grasslands and stands of Leucaena leucocephala to overrun the vast majority of land. Pteropus tonganus abundance was high (5757 bats) despite deforestation and hunting. Roosting sites were restricted to native forest fragments. Grasslands and stands of L. leucocephala were completely void of bats at all times. The mean foraging density in farmland was four times higher than in forests and foraging competition was routinely observed in farmland but was extremely rare in forests. The author suggests that during the study, extensive foraging in farmland was supporting the high P. tonganus population. Additionally, the preferential foraging in farmland was responsible for the low foraging densities within forests and dramatically less intraspecies competition for forest resources. Further research is needed on seed dispersal within forests and to test for seasonal variations in bat abundance and feeding. [source] Enhancement of Farmland Biodiversity within Set-Aside LandCONSERVATION BIOLOGY, Issue 4 2004JOSH VAN BUSKIRK agricultura; biodiversidad; conservación; terrenos de reserva Abstract:,The efficacy of agricultural set-aside policies for protecting farmland biodiversity is widely debated. Based on a meta-analysis of 127 published studies, we found that land withdrawn from conventional production unequivocally enhances biodiversity in North America and Europe. The number of species of birds, insects, spiders, and plants is 1,1.5 standard deviation units higher on set-aside land, and population densities increase by 0.5,1 standard deviation units. Set-aside land may be especially beneficial for desirable taxa because North American bird species that have exhibited population declines react most positively to set-aside agricultural land. Larger and older plots protect more species and higher densities, and set-aside land is more effective in countries with less-intensive agricultural practices and higher fractions of land removed from production. Although policies specifically designed to protect biodiversity might work even better, current incentives clearly improve the standing of plants and animals in farmland. Resumen:,La eficiencia de las políticas de reservas agrícolas para la protección de la biodiversidad en tierras cultivadas esta ámpliamente debatida. Con base en un meta-análisis de 127 estudios publicados, encontramos que terrenos retirados de la producción convencional inequívocamente mejoran la biodiversidad en Norte América y Europa. El número de especies de aves, insectos, arañas y plantas es 1-1.5 unidades de desviación estándar más alto en terrenos de reserva, y las densidades de población incrementan en 0.5-1 unidades de desviación estándar. Los terrenos de reserva pueden ser especialmente benéficos para taxones deseables porque especies de aves norteamericanas que han presentado una declinación poblacional reaccionan positivamente a terrenos agrícolas de reserva. Parcelas más grandes y viejas protegen a más especies y tienen mayores densidades, y los terrenos de reserva son más efectivos en países con prácticas agrícolas menos intensivas y con mayores fracciones de tierras removidas de la producción. Aunque las políticas diseñadas específicamente para proteger la biodiversidad pueden ser mejores aún, los incentivos actuales claramente mejoran la situación de plantas y animales en tierras agrícolas. [source] "THEY COME IN PEASANTS AND LEAVE CITIZENS": Urban Villages and the Making of Shenzhen, ChinaCULTURAL ANTHROPOLOGY, Issue 3 2010JONATHAN BACH ABSTRACT This essay examines the ongoing process of postsocialist transformation at the intersection of cultural and economic forces in an urban environment through the example of the so-called "urban villages"(chengzhongcun) in Shenzhen, China, a booming southern Chinese city and former Special Economic Zone next to Hong Kong. This essay ethnographically examines the role of former rural collectives encircled by a city that has exploded from farmland to an export-driven city of over 14 million people in little over one generation. These villages form an internal other that is both the antithesis and the condition of possibility for Shenzhen city. By co-opting the market economy in ways that weave them into the fabric of the contemporary global city, the villages become as much an experiment as the Special Economic Zone itself. This essay analyzes the urban,rural divide as complicit in each other's continued production and effacement and explores how village and city exploit the ambiguities of their juxtaposition in the making of Shenzhen. [source] Range-wide patterns of greater sage-grouse persistenceDIVERSITY AND DISTRIBUTIONS, Issue 6 2008Cameron L. Aldridge ABSTRACT Aim, Greater sage-grouse (Centrocercus urophasianus), a shrub-steppe obligate species of western North America, currently occupies only half its historical range. Here we examine how broad-scale, long-term trends in landscape condition have affected range contraction. Location, Sagebrush biome of the western USA. Methods, Logistic regression was used to assess persistence and extirpation of greater sage-grouse range based on landscape conditions measured by human population (density and population change), vegetation (percentage of sagebrush habitat), roads (density of and distance to roads), agriculture (cropland, farmland and cattle density), climate (number of severe and extreme droughts) and range periphery. Model predictions were used to identify areas where future extirpations can be expected, while also explaining possible causes of past extirpations. Results, Greater sage-grouse persistence and extirpation were significantly related to sagebrush habitat, cultivated cropland, human population density in 1950, prevalence of severe droughts and historical range periphery. Extirpation of sage-grouse was most likely in areas having at least four persons per square kilometre in 1950, 25% cultivated cropland in 2002 or the presence of three or more severe droughts per decade. In contrast, persistence of sage-grouse was expected when at least 30 km from historical range edge and in habitats containing at least 25% sagebrush cover within 30 km. Extirpation was most often explained (35%) by the combined effects of peripherality (within 30 km of range edge) and lack of sagebrush cover (less than 25% within 30 km). Based on patterns of prior extirpation and model predictions, we predict that 29% of remaining range may be at risk. Main Conclusions, Spatial patterns in greater sage-grouse range contraction can be explained by widely available landscape variables that describe patterns of remaining sagebrush habitat and loss due to cultivation, climatic trends, human population growth and peripherality of populations. However, future range loss may relate less to historical mechanisms and more to recent changes in land use and habitat condition, including energy developments and invasions by non-native species such as cheatgrass (Bromus tectorum) and West Nile virus. In conjunction with local measures of population performance, landscape-scale predictions of future range loss may be useful for prioritizing management and protection. Our results suggest that initial conservation efforts should focus on maintaining large expanses of sagebrush habitat, enhancing quality of existing habitats, and increasing habitat connectivity. [source] Thrushes now largely restricted to the built environment in eastern EnglandDIVERSITY AND DISTRIBUTIONS, Issue 4 2000Christopher F. Mason Abstract. ,I studied the distribution and density of three thrush populations, blackbird Turdus merula, song thrush T. philomelos and mistle thrush T. viscivorus, in an urban and contiguous rural area, totalling 2636 ha, in eastern England. Populations of these species are declining and I found 826, 85 and 30 territories of blackbird, song thrush and mistle thrush, respectively. Significantly more territories of all species than expected were within the urban boundary. Significantly more territories than expected were found of all three species in the built environment (residential housing, factories, schools, etc. with their associated gardens and green-space), urban and rural areas combined. Farmland occupied 67% of the study area but held significantly fewer blackbird and mistle thrush territories than expected, associated mainly with the small amount of grass; song thrushes were not recorded on farmland. Rural woodland and scrub held more blackbird and song thrush territories than expected. Song thrush was significantly associated with scrub within the urban boundary. With all three species largely absent from farmland, residential habitats can be considered as habitat refuges. The consequences of this for conservation and planning are discussed. [source] Numerical and dietary responses of a predator community in a temperate zone of EuropeECOGRAPHY, Issue 2 2009Gilles Dupuy The generalist predation hypothesis predicts that the functional responses of generalist predator species should be quicker than those of specialist predators and have a regulating effect on vole populations. New interpretations of their role in temperate ecosystems have, however, reactivated a debate suggesting generalist predators may have a destabilizing effect under certain conditions (e.g. landscape homogeneity, low prey diversity, temporary dominance of 1 prey species associated with a high degree of dietary specialization). We studied a rich predator community dominated by generalist carnivores (Martes spp., Vulpes vulpes, Felis catus) over a 6 yr period in farmland and woodland in France. The most frequent prey were small rodents (mostly Microtus arvalis, a grassland species, and Apodemus spp., a woodland species). Alternative prey were diverse and dominated by lagomorphs (Oryctolagus cuniculus, Lepus europeus). We detected a numerical response among specialist carnivores but not among generalist predators. The dietary responses of generalist predators were fairly complex and most often dependent on variation in density of at least 1 prey species. These results support the generalist predation hypothesis. We document a switch to alternative prey, an increase of diet diversity, and a decrease of diet overlap between small and medium-sized generalists during the low density phase of M. arvalis. In this ecosystem, the high density phases of small mammal species are synchronous and cause a temporary specializing of several generalist predator species. This rapid functional response may indicate the predominant role of generalists in low amplitude population cycles of voles observed in some temperate areas. [source] Combining information from range use and habitat selection: sex-specific spatial responses to habitat fragmentation in tawny owls Strix alucoECOGRAPHY, Issue 2 2006Peter Sunde How individuals respond to habitat heterogeneity is usually measured as variation in range size and by ranking the relative importance of habitat types (habitat selection). The combined effect of how individuals incorporate different habitat types in their home ranges and allocate their time budget between them is rarely derived. Additionally, when home range size varies between individuals, habitat selection analyses might be flawed if foraging decisions are based on variation in absolute rather than proportional availability. We investigated the suitability of standard analytical approaches by measuring the spatial responses of tawny owls to habitat fragmentation. These owls inhabited woodland of various sizes, representing a fragmentation gradient from open farmland with small, isolated woodland patches, to continuous woodland within their home ranges. In 17 territories within open farmland, the available area covered by woodland increased with the square root of the area of open land embraced in the home range. The owls did not display functional response in habitat selection, but females selected woodland more strongly than males. Females utilised woodland 10 times more intensively in farmland than in continuous woods, whereas males utilised farmland woods 3.2 times more intensively. Moreover, females in farmland exploited woodland 3.2 times as intensively as males, apparently because of higher travel costs in open areas. Since the extensive variation in intensity of use as a function of total availability was not indicated from the analysis of habitat selection, we suggest that information about intensity of use be more widely used as a supplementary measure of habitat use patterns than appears to be the practice at present. [source] The importance of interspecific interactions for breeding-site selection: peregrine falcons seek proximity to raven nestsECOGRAPHY, Issue 6 2004Fabrizio Sergio The advent of GIS is initiating a rapid increase in the utilization of wildlife-habitat models as tools for species and habitat management. However, such models rarely include estimates of interspecific interactions among explanatory variables. We tested the importance of such variables by using the peregrine falcon Falco peregrinus, a medium-sized raptor frequently reported to be affected by heterospecifics, as a model species. In an Alpine population, compared to random locations, peregrines selected breeding sites farther from conspecifics, on taller cliffs, with higher availability of farmland and closer to raven Corvus corax nests. Within suitable habitat, peregrines selected sites near ravens and far from elevations associated with golden eagle Aquila chrysaetos nests. Productivity increased with cliff size, farmland availability (rich in the local main prey) and with proximity to ravens, suggesting that the observed choices were adaptive. Finally, at the regional level, peregrine density peaked at low elevation and was positively associated with raven density. The results suggested an active breeding association of peregrines with ravens, which may provide early-warning cues against predators and safe alternative nest-sites. They also confirmed the importance of including estimates of interspecific interactions among explanatory variables, which may: 1) make models more realistic; 2) increase their predictive power by lowering unexplained variance due to unmeasured factors; 3) provide unexpected results such as the cryptic, large-scale breeding association of our study; and 4) stimulate further hypothesis formulation and testing, ultimately leading to deeper ecological knowledge of the study system. [source] Effects of sequential depositional basins on lake response to urban and agricultural pollution: a palaeoecological analysis of the Qu'Appelle Valley, Saskatchewan, CanadaFRESHWATER BIOLOGY, Issue 3 2000Aruna S. Dixit 1. Palaeolimnological analyses of fossil diatoms and pigments were conducted in four lakes of the Qu'Appelle Valley, Saskatchewan, Canada, to quantify the effect of upstream depositional basins on lake response to urban and agricultural human activities. Pasqua, Echo, Mission and Katepwa lakes exhibit similar modern limnological characteristics, lie sequentially downstream from urban point sources of growth-limiting nitrogen (N), yet drain similarly large areas of farmland (38,40 × 103 km2). 2. Analyses indicated that all lakes were naturally productive, contained eutrophic diatoms (i.e. Stephanodiscus niagarae, S. hantzchii, S. parvus and Aulacoseira granulata), and supported blooms of colonial (as myxoxanthophyll) and potentially toxic N-fixing cyanobacteria (aphanizophyll), even prior to the onset of European settlement (ca. 1890) and urban development (ca. 1930). 3. The onset of agricultural practices ca. 1890 had only modest effects on algal communities in the Qu'Appelle lakes, with subtle increases in eutrophic diatom species (Pasqua, Mission and Katepwa lakes) and 25,50% increases in pigment-inferred algal abundance (Echo, Mission and Katepwa lakes). 4. Despite naturally high production, total algal abundance (,-carotene) in upstream Pasqua Lake increased by more than 350% after intense urbanization beginning ca. 1930, while eutrophic diatoms became more common and cyanobacteria populations increased ten-fold. Principal components analysis (PCA) explained 64% of diatom variance, and identified three eras corresponding to baseline, pre-agricultural communities (1776,1890), an era of high production (ca. 1925,1960) and recent variable community composition following tertiary treatment of urban sewage (ca. 1977,1990). 5. Analyses of three downstream lakes demonstrated that urban impacts following 1930 remained evident in fossil profiles of ,-carotene and myxoxanthophyll, but that large blooms of N-fixing cyanobacteria were restricted to the past 25 years at downstream Mission and Katepwa lakes. Similarly, PCA showed that fossil diatom assemblages exhibited little directional variation until the 1970s. 6. Together, these analyses support the hypothesis that upstream lakes were effective at reducing the impacts of point-source urban nutrients on downstream lakes. In contrast, diffuse agricultural activities had only limited impacts on water quality and these were less well ameliorated by upstream basins. [source] Local Knowledge and Economic Realities Affecting Soil Erosion in the Rach Rat Catchment, VietnamGEOGRAPHICAL RESEARCH, Issue 1 2008DAO KIM NGUYEN THUY BINH Abstract Several parts of Binh Phuóc Province, southern Vietnam, suffer from degraded soils and vegetation as a result of both natural erosion of weak mud rocks and sandstones and intensive human activity, especially through land clearing for agriculture on unstable slopes, deforestation, and abandonment of poor farmland. The underlying cause of this land degradation has been the farming habits of migrants of varying ethnic groups who have settled in the area since 1980. The indigenous farming knowledge of these people and the role of that knowledge in soil erosion were examined by a series of household surveys. They enabled farming practices to be related to ground cover established from a 2002 Landsat 7 ETM (Enhanced Thematic Mapper), and erosion data from a series of erosion bridge measurements. A GIS (Geographical Information System) approach was piloted as a means of identifying areas vulnerable to erosion. This could then be combined with the understanding of farming practices to reveal the relative roles of farmer behaviour, crop cover, and slope and soil characteristics in the erosion process. Land use, local people's knowledge and economic realities are the main factors, as well as natural conditions, that drive this land degradation. [source] HALF A CENTURY OF CROPLAND CHANGE,GEOGRAPHICAL REVIEW, Issue 3 2001JOHN FRASER HART ABSTRACT. The census concept of total cropland is a better measure of effective agricultural land than is total farmland, which includes extensive areas of woodland owned by farmers. The cropland area of the United States dropped from 478 million acres in 1949 to 431 million acres in 1997, for a net loss of less than 1 million acres, or roughly one-fifth of 1 percent, per year. In the midwestern agricultural heartland most counties changed less than 5 percent in the half-century, and more counties gained than lost. The West was a crazy quilt of change, and in the East most counties lost more than 10 percent. Major metropolitan counties lost a few percentage points more than did adjacent areas, but at a lower rate per capita than the nation as a whole. Most of the loss of cropland was in marginal agricultural counties with soils of low inherent fertility and topography unsuited to modern farm machinery. The loss of cropland to suburban encroachment may be cause for intense local concern, but attempts to thwart development cannot be justified on grounds of a net national loss of good cropland. [source] Soil organic carbon stocks in China and changes from 1980s to 2000sGLOBAL CHANGE BIOLOGY, Issue 9 2007ZUBIN XIE Abstract The estimation of the size and changes of soil organic carbon (SOC) stocks is of great importance for decision makers to adopt proper measures to protect soils and to develop strategies for mitigation of greenhouse gases. In this paper, soil data from the Second State Soil Survey of China (SSSSC) conducted in the early 1980s and data published in the last 5 years were used to estimate the size of SOC stocks over the whole profile and their changes in China in last 20 years. Soils were identified as paddy, upland, forest, grassland or waste-land soils and an improved soil bulk density estimation method was used to estimate missing bulk density data. In the early 1980s, total SOC stocks were estimated at 89.61 Pg (1 Pg=103 Tg=1015 g) in China's 870.94 Mha terrestrial areas covered by 2473 soil series. In the paddy, upland, forest and grassland soils the respective total SOC stocks were 2.91 Pg on 29.87 Mha, 10.07 Pg on 125.89 Mha, 34.23 Pg on 249.32 Mha and 37.71 Pg on 278.51 Mha, respectively. The SOC density of the surface layer ranged from 3.5 Mg ha,1 in Gray Desery grassland soils to 252.6 Mg ha,1 in Mountain Meadow forest soils. The average area-weighted total SOC density in paddy soils (97.6 Mg ha,1) was higher than that in upland soils (80 Mg ha,1). Soils under forest (137.3 Mg ha,1) had a similar average area-weighted total SOC density as those under grassland (135.4 Mg ha,1). The annual estimated SOC accumulation rates in farmland and forest soils in the last 20 years were 23.61 and 11.72 Tg, respectively, leading to increases of 0.472 and 0.234 Pg SOC in farmland and forest areas, respectively. In contrast, SOC under grassland declined by 3.56 Pg due to the grassland degradation over this period. The resulting estimated net SOC loss in China's soils over the last 20 years was 2.86 Pg. The documented SOC accumulation in farmland and forest soils could thus not compensate for the loss of SOC in grassland soils in the last 20 years. There were, however, large regional differences: Soils in China's South and Eastern parts acted mainly as C sinks, increasing their average topsoil SOC by 132 and 145 Tg, respectively. In contrast, in the Northwest, Northeast, Inner Mongolia and Tibet significant losses of 1.38, 0.21, 0.49 and 1.01 Pg of SOC, respectively, were estimated over the last 20 years. These results highlight the importance to take measures to protect grassland and to improve management practices to increase C sequestration in farmland and forest soils. [source] Unstructured grid generation using LiDAR data for urban flood inundation modellingHYDROLOGICAL PROCESSES, Issue 11 2010Ryota Tsubaki Abstract Inundation disasters, caused by sudden water level rise or rapid flow, occur frequently in various parts of the world. Such catastrophes strike not only in thinly populated flood plains or farmland but also in highly populated villages or urban areas. Inundation of the populated areas causes severe damage to the economy, injury, and loss of life; therefore, a proper management scheme for the disaster has to be developed. To predict and manage such adversity, an understanding of the dynamic processes of inundation flow is necessary because risk estimation is performed based on inundation flow information. In this study, we developed a comprehensive method to conduct detailed inundation flow simulations for a populated area with quite complex topographical features using LiDAR (Light Detection and Ranging) data. Detailed geospatial information including the location and shape of each building was extracted from the LiDAR data and used for the grid generation. The developed approach can distinguish buildings from vegetation and treat them differently in the flow model. With this method, a fine unstructured grid can be generated representing the complicated urban land features precisely without exhausting labour for data preparation. The accuracy of the generated grid with different grid spacing and grid type is discussed and the optimal range of grid spacing for direct representation of urban topography is investigated. The developed method is applied to the estimation of inundation flows, which occurred in the basin of the Shin-minato River. A detailed inundation flow structure is represented by the flow model, and the flow characteristics with respect to topographic features are discussed. Copyright © 2010 John Wiley & Sons, Ltd. [source] Modelling the hydrology of a catchment using a distributed and a semi-distributed modelHYDROLOGICAL PROCESSES, Issue 3 2005Ahmed Abu El-Nasr Abstract Various hydrological models exist that describe the phases in the hydrologic cycle either in an empirical, semi-mechanistic or fully mechanistic way. The way and level of detail for the different processes of the hydrologic cycle that needs to be described depends on the objective, the application and the availability of data. In this study the performance of two different models, the fully distributed MIKE SHE model and the semi-distributed SWAT model, was assessed. The aim of the comparative study was to examine if both models are equally able to describe the different phases in the hydrologic cycle of a catchment, given the availability of hydrologic data in the catchment. For the comparison, historic data of the Jeker river basin, situated in the loamy belt region of Belgium, was used. The size of the catchment is 465 km2. The landscape is rolling, the dominant land use is farmland, and the soils vary from sandy-loam to clay-loam. The daily data of a continuous period of 6 years were used for the calibration and validation of both models. The results were obtained by comparing the performance of the two models using a qualitative (graphical) and quantitative (statistical) assessment, such as graphical representation of the observed and simulated river discharge, performance indices, the hydrograph maxima, the baseflow minima, the total accumulated volumes and the extreme value distribution of river flow data. The analysis revealed that both models are able to simulate the hydrology of the catchment in an acceptable way. The calibration results of the two tested models, although they differ in concept and spatial distribution, are quite similar. However, the MIKE SHE model predicts slightly better the overall variation of the river flow. Copyright © 2005 John Wiley & Sons, Ltd. [source] Agricultural land use and Skylark Alauda arvensis: a case study linking a habitat association model to spatially explicit change scenariosIBIS, Issue 1 2010NIGEL D. BOATMAN The development of forward scenarios is a useful method of envisaging the environmental implications of potential changes in land use, as a tool for policy development. In this paper, a spatially explicit case study is used to provide insight into the environmental impacts of Common Agricultural Policy reform on Skylark Alauda arvensis, a species which is widespread on arable farmland, breeds in crops and has declined in recent decades. A generalized linear mixed model was used to estimate Skylark breeding population densities in different crops, using survey data collected from farms in the east of England, supplemented by the literature. Model outputs were then used to predict Skylark densities in an East Anglian Joint Character Area dominated by arable cropping. Predicted densities were mapped at field level using GIS, based on actual cropping derived from Integrated Administration and Control System data collected for the administration of subsidy payments. Three future scenarios were then created, based on expert opinion of potential changes in cropping over the next 5 years, and potential changes in Skylark density mapped on the basis of the predicted changes in cropping patterns. Overall, Skylark densities were predicted to decrease on average by 11,14% under ,market-led' (increasing wheat and oilseed rape, reduced set-aside) and ,energy crop' (5% area under short rotation coppice) scenarios, but remained virtually unchanged under an ,environment-led' (diverse cropping) scenario. The ,market-led' scenario is closest to short-term agricultural trajectories, but wider cultivation of biomass energy crops as modelled under the ,energy crop' scenario could occur in the medium term if energy policies are favourable. Appropriate mitigation strategies therefore need to be implemented if a continued decline in the Skylark population on lowland arable farmland is to be averted. The results provide a readily accessible visualization of the potential impacts of land-use change for policy-makers; similar techniques could be applied to visualize effects of changes arising through other drivers, including climate change. [source] Nest-site selection by Great Bustards Otis tarda suggests a trade-off between concealment and visibilityIBIS, Issue 1 2010MARINA MAGAÑA Great Bustards Otis tarda have expanded their habitat range from historical occupancy of natural steppes to arable farmland, where the species initially benefited from favourable feeding conditions. More recently, the species has suffered severe declines due partly to agricultural intensification. Nest losses and juvenile mortality are amongst the factors most seriously affecting survival probabilities of many populations of this endangered species, suggesting that management of nesting habitats would bring conservation benefits. We studied nest-site selection in a Great Bustard population of central Spain by radiotracking 42 females for periods of between 1 and 4 years. Females selected nest-sites in fallows or cereal fields, in areas of low patch-type diversity, far from human infrastructure, and with good horizontal visibility. These results suggest that females look for shelter, but also need to have good visibility while incubating, and they support the hypothesis that nest selection is a trade-off between concealment and visibility. We interpret both preferences as adaptations to reduce predation pressure, one of the main causes of nest failure in this species. Nests were placed on slopes significantly orientated to the southeast, which suggests that females also seek sites protected from the cold north-westerly winds that are prevalent in the study area. To reduce nest destruction, harvesting should be delayed as long as possible and habitat conservation measures should not be restricted to lek sites but also include nesting areas, which are frequently located far from leks. [source] Habitat selection by Ortolan Buntings Emberiza hortulana in post-fire succession in Catalonia: implications for the conservation of farmland populationsIBIS, Issue 4 2009MYLES H. M. MENZ The Ortolan Bunting Emberiza hortulana is a long-distance migrant that has suffered major population declines across much of its European breeding range. While northern populations are bound largely to farmland, Mediterranean populations are largely confined to habitats subject to recurrent wildfires. Habitat selection of the Ortolan Bunting was assessed in a recently burnt area in Catalonia at landscape and habitat scales. A Zero-inflated Poisson procedure was used to model the abundance of birds in relation to landscape and habitat variables. The most parsimonious landscape model predicted the highest abundance on south-facing slopes, with a gradient above 10°. The most parsimonious habitat model showed a positive quadratic effect of bare ground and regenerating oak Quercus spp., with predicted optima for abundance around 20,30% and 20% cover, respectively. There was a clear relationship between predicted abundance of the Ortolan Bunting and post-fire regenerating oak shrubs. South-facing, moderately sloping areas were favoured and bare ground was a key feature of the species' habitat. A matrix combining patches of sparse oak shrubs and patches of bare ground appears to be the optimal breeding habitat in the Mediterranean. The maintenance or provision of similar habitat features, especially patches of bare ground, may prove crucial for the conservation of rapidly declining Ortolan Bunting populations on farmland across temperate Europe. [source] Habitat selection and reproductive success of Ortolan Buntings Emberiza hortulana on farmland in central Sweden , the importance of habitat heterogeneityIBIS, Issue 3 2008ÅKE BERG Many granivorous birds have shown severe population declines in Europe during recent decades. The aim of the present study was to analyse habitat preferences and reproductive success of one such species, the Ortolan Bunting Emberiza hortulana, in different farmland habitats in south-central Sweden. Four seemingly different land-use types were preferred: permanent set-asides, short rotation coppice, and grazed and unmanaged semi-natural pastures. Territories and random sites differed considerably in the proportion of these preferred land-use types; 39% of territories had > 70% preferred habitat (at the 100-m scale) compared to 5% of random sites. In contrast, 22% of territories and 65% of random sites had no preferred habitats. All the preferred habitats had heterogeneous ground vegetation characterized by patches with bare ground, or at least sparse ground vegetation, intermixed with patches with taller vegetation. Ortolan Buntings also preferred a heterogeneous habitat structure with occurrence of field islets, shrubby edges, barns and electric wires, which could act as song posts or suitable nest-sites, in 88% of territories. At a larger (1-km square) scale, territories occupied by pairs aggregated strongly in areas with high proportions of preferred habitats. The number of territories with single males correlated positively with the number of pairs, which suggests that conspecific attraction may influence territory distribution. No measured habitat factors were related to reproductive success. However, due to habitat preferences and the higher proportion of paired males in one habitat type (set-aside), the production of young (fledglings/ha) is expected to be higher in set-asides, as well as in short-rotation coppices and semi-natural pastures. Thus, these habitats are important for the conservation of the Ortolan Bunting. Large areas with habitat structures such as field islets are especially important because the Ortolan Bunting breeds in aggregations in these areas. [source] Population trends of widespread woodland birds in EuropeIBIS, Issue 2007RICHARD D. GREGORY We explore population trends of widespread and common woodland birds using data from an extensive European network of ornithologists for the period 1980,2003. We show considerable differences exist in the European trends of species according to the broad habitat they occupy and the degree to which they specialize in habitat use. On average, common forest birds are in shallow decline at a European scale; common forest birds declined by 13%, and common forest specialists by 18%, from 1980 to 2003. In comparison, populations of common specialists of farmland have declined moderately, falling on average by 28% from 1980 to 2003. These patterns contrast with that shown by generalist species whose populations have been roughly stable over the same period, their overall index increasing by 3%. There was some evidence of regional variation in the population trends of these common forest species. The most obvious pattern was the greater stability of population trends in Eastern Europe compared with other regions considered. Among common forest birds, long-distance migrants and residents have on average declined most strongly, whereas short-distance migrants have been largely stable, or have increased. There was some evidence to suggest that ground- or low-nesting species have declined more strongly on average, as have forest birds with invertebrate diets. Formal analysis of the species trends confirmed the influence of habitat use, habitat specialization and nest-site; the effects of region and migration strategy were less clear-cut. There was also evidence to show that year-to-year variation in individual species trends at a European scale was influenced by cold winter weather in a small number of species. We recommend that the species trend information provided by the new pan-European scheme should be used alongside existing mechanisms to review the conservation status of European birds. The analysis also allows us to reappraise the role of common forest bird populations as a potential barometer of wider forest health. The new indicator appears to be a useful indicator of the state of widespread European forest birds and might prove to be a useful surrogate for trends in forest biodiversity and forest health, but more work is likely to be needed to understand the interaction between bird populations and their drivers in forest. [source] Do voles make agricultural habitat attractive to Montagu's Harrier Circus pygargus?IBIS, Issue 3 2007BEN J. KOKS Loss and degradation of habitat threatens many bird populations. Recent rural land-use changes in the Netherlands have led to a shift in habitat use by breeding Montagu's Harriers Circus pygargus. Since the 1990s, unprecedented numbers of this species have bred in farmland compared with numbers in natural habitat. Destruction of nests by agricultural operations, however, compromises breeding success. Between 1992 and 2005, the number of breeding pairs in the northeastern Netherlands was positively, though weakly, correlated with previous-year estimated abundance of voles, mostly Microtus arvalis. In good vole years, the onset of laying was earlier and mean clutch size was larger. Vole abundance was relatively higher in set-aside land and in high and dense vegetation. We suggest that agri-environmental schemes aimed at increasing the availability of voles in agricultural breeding areas may be an effective management tool for the conservation of Montagu's Harriers in the northeastern Netherlands. [source] Survival rates, causes of failure and productivity of Skylark Alauda arvensis nests on lowland farmlandIBIS, Issue 4 2002P. F. Donald This paper analyses data from 995 Skylark Alauda arvensis nests found on lowland farms in southern England from 1996 to 1998. The majority of recorded nest failures were caused by predation except in agricultural grass, where trampling and agricultural operations were equally important. Nest survival rates varied between crop types, nests in cereals being around twice as likely to succeed as nests in grass or set-aside. In cereals, nest survival rates increased with increasing distance from the nearest tramline and declined over the course of the breeding season. Predator control also had a significant independent effect on nest survival rates. On one farm where many other factors were held constant, a highly significant increase in nest survival rates from 12.3% to 40.7% coincided with the introduction of intensive predator control, which also appeared to bring forward mean laying dates. Most environmental factors explaining significant variation in nest survival rates did so only at the chick stage. The mean number of chicks produced per nesting attempt was 1.26 in cereals, 0.78 in set-aside and 0.63 in grass, the differences being due primarily to variation in nest survival rates. Low densities of Skylark territories in cereal crops are not therefore the consequence of low breeding success at the scale of the individual nest and probably reflect limitations on the number of attempts made in a season. Measures taken to improve the attractiveness of cereal crops as a nesting habitat for Skylarks, and beneficial changes in grassland management, are likely to increase overall productivity. [source] Population dynamics and reproduction of Northern Lapwings Vanellus vanellus in a meadow restoration area in central SwedenIBIS, Issue 3 2002Åke Berg To investigate the effectiveness of a meadow restoration programme, we studied the relationships between population changes and environmental changes, return rates and hatching success in a population of Northern Lapwings Vanellus vanellus. The study was performed on mixed farmland (59 km2) in central Sweden, an area that underwent extensive meadow restoration between 1985 and 1994. The study included more than 2600 nests, supplemented with observations of 127 individually colour-ringed Northern Lapwings. The breeding population varied (2.7,5.3 pairs/km2), but showed no significant trend with time. The population increased in years with high spring flooding levels. Population size was unrelated to demographic factors (e.g. hatching success the previous year (14,50%), and return rate). Lapwings moved considerably between years and their nest site fidelity was unrelated to previous hatching success or other factors, suggesting that changes in habitat quality and migration between populations were important in regulating population size. Recent extensive meadow restoration did not seem to aid the Northern Lapwing population; birds continued nesting on tillage even though most nests were destroyed by farming activities. A relatively high relaying frequency improved hatching success, which was still lowest in the most preferred habitats (spring sown crops, total hatching success c. 30%). The few Northern Lapwings breeding in the least preferred habitats (meadows and cultivated grassland) had a better hatching success (> 70% total hatching success), suggesting that habitat selection was not determined by hatching success. From these results, recommendations are made for the management of Northern Lapwing (and associated species) populations on farmland. [source] Body condition, growth rates and diet of Skylark Alauda arvensis nestlings on lowland farmlandIBIS, Issue 3 2001PAUL F. DONALD Factors affecting the diet, body condition and growth rates of Skylark chicks were assessed to examine their relationship to their agricultural environment during a critical period in the life cycle of this rapidly declining species. Rainfall explained the greatest amount of variation in body condition and growth rates and had a negative effect on both. Body condition indices were a good predictor of the likelihood of future partial brood loss to starvation. Low body condition in grass fields was related to a low diversity in the diet. Chicks fed insect larvae had higher body condition indices than those not fed larvae. Larger broods tended to have higher growth rates than smaller ones, whereas smaller broods tended to have higher body condition indices. Natural brood size reduction through the non-hatching of eggs resulted in higher body condition indices than were found in nests with the same number of chicks where all eggs hatched, this effect being independent of absolute brood size. There was no significant difference between crop types in the distance adult birds flew to forage for food for nestlings and foraging crop destination had no effect on chick development. Differences between crop types in chick diet could be related to the documented effects of pesticides on different prey species. We suggest that recent agricultural changes have affected diet and possibly body condition, but that these effects are unlikely to have been an important factor in recent population declines. [source] Water management tasks in the summer polders of the Nemunas lowland,IRRIGATION AND DRAINAGE, Issue 2 2006Antanas Lukianas plaine d'inondation; polders d'été; gestion des eaux Abstract Surplus water during floods as well as the low level of the soil surface determine the complicated ecological, economic and demographic conditions in the Nemunas delta. Subsequently, it leads to different types and intensity of use of farmland as well as different methods of water regime regulation: summer or winter type polders. The building of 17 summer polders in the 32,500,ha floodplain area was a compromise, seeking to improve farming conditions and maintain the stability of the flood regime and ecology in the delta. Field measurements and mathematical modelling were carried out. As study results have shown, grass yield losses due to flooding depend on the distribution of water levels and flood duration in the summer polders. Relative damage to agriculture is insignificant and makes up only 10,15% of the total amount of flood damage in the Nemunas lowland. The field measurements and hydraulic and mathematical modelling of flow and sediment regime as well as study of flooding and changed farming conditions also show that it is possible to reduce the height of floods and economic and ecological damage. Rearrangement of the system of protective dikes, regulation of the main river canal and water/sedimentation regime with the help of pumping stations, decrease of pollutant migration into the Curonian Lagoon and Baltic Sea, and recreation of natural meadows are important in that case. Copyright © 2006 John Wiley & Sons, Ltd. Des eaux excédentaires en période de crues et un faible niveau du sol déterminent les conditions écologiques, économiques et démographiques complexes du delta du fleuve Nemunas. En particulier, des types et intensités différentes dans l'utilisation des terres arables, ainsi que des méthodes différentes de régulation du régime des eaux: polders d'été ou d'hiver. La construction de 17 polders d'été sur 32 500,ha de plaine d'inondation a été une solution de compromis pour améliorer l'agriculture et maintenir la stabilité du régime des crues et de l'écologie du delta. Des mesures de terrain et des modèles mathématique ont été réalisés. D'après les résultats des études, les pertes de récolte d'herbe dûes aux crues dépendent de la distribution des niveaux d'eau et de la durée de la crue dans les polders d'été. L'impact négatif sur l'agriculture est négligeable et ne représente que 10 à 15% des dommages totaux dus aux crues dans le delta du fleuve Nemunas. Les mesures de terrain et la modélisation hydraulique et mathématique de l'écoulement et de la sédimentation, ainsi que l'analyse des crues et des modifications de production agricole, prouvent également qu'il est possible de réduire la hauteur des crues et de diminuer ainsi les dommages économiques et écologiques. Dans ce cas, il convient de réorganiser le système des digues de protection, de réguler le chenal principal du fleuve et le régime de sédimentation des eaux à l'aide de stations de pompage, de réduire les déversements polluants dans la lagune Curonian et la mer Baltique, et de régénérer des pâturages naturels. Copyright © 2006 John Wiley & Sons, Ltd. [source] The Chilean Agrarian Transformation: Agrarian Reform and Capitalist ,Partial' Counter-Agrarian Reform, 1964,1980JOURNAL OF AGRARIAN CHANGE, Issue 1 2007Free-Market Neoliberalism, Part 1: Reformism, Socialism This article, which is published in two parts, is an empirical analysis of the Chilean agrarian reform (1964,1973) and ,partial' counter-agrarian reform (1974,1980). Its aim is to explain and interpret their logic and the changes they brought to Chile's agrarian property regime in particular and Chilean life in general. Chile's agrarian reform was successful in expropriating (under the Frei and Allende administrations, 1964,1973) the great estates of the hacienda landed property system. The capitalist ,partial' counter-reform then redistributed them (under the military, 1974,1980). CORA, the country's agency for agrarian reform, expropriated and subsequently redistributed 5809 estates of almost 10 million hectares, or 59 per cent of Chile's agricultural farmland. A large amount of the expropriated land (41 per cent) benefited 54,000 peasant households with small-sized family farms and house-sites. The rest of the farmland benefited efficient and competitive commercial farmers and agro-business and consolidated medium-sized farms. Of central concern is the role of the agrarian reform and subsequent ,partial' counter-reform processes in fostering the transformation of the erstwhile agrarian structure of the hacienda system toward agrarian capitalism. The redistribution of the agricultural land previously expropriated made possible the formation of an agro-industrial bourgeoisie, small commercial farmers, an open land market and a dynamic agricultural sector. While, however, under military rule, a selected few benefited with family farms and became independent agricultural producers, a large majority of reformed and non-reformed campesinos were torn from the land to become non-propertied proletarians in a rapidly modernizing but highly exclusionary agricultural sector. [source] Why Isn't More US Farmland Organic?JOURNAL OF AGRICULTURAL ECONOMICS, Issue 2 2010Nicolai V. Kuminoff D81; Q18 Abstract We develop a theoretical model to assess the dollar compensation required to induce conventional growers to convert to organic. The model incorporates the uncertainty in producers' expectations about future returns and about the impact of policy changes on these expectations in particular. We demonstrate that a new policy which favours organic can have opposing effects on the rate of conversion. An increase in relative returns to organic today will increase conversion rates. However, if the future of the policy programme is uncertain, its introduction can increase the value of waiting to switch, which will decrease conversion rates. We then develop an empirical switching regression model that enables direct estimation of the value associated with being able to postpone the conversion decision until some of the uncertainty is resolved. The model is applied to data on organic and conventional soybeans before and after major changes in US farm policy toward organic growers. The results suggest that sunk costs associated with conversion to organic coupled with uncertainty about future returns can help to explain why there is so little organic farmland in the USA. [source] | ||||||||||||||||||||||||||||||||||||||||