The effectiveness of ditch banks as dispersal corridor for plants in agricultural landscapes depends on species' dispersal traits
Dijk, W.F.A. van; Ruijven, J. van; Berendse, F. ; Snoo, G.R. de - \ 2014
Biological Conservation 171 (2014). - ISSN 0006-3207 - p. 91 - 98.
agri-environment schemes - european countries - biodiversity - grassland - farmland - habitat - colonization - fragmentation - connectivity - pollinators
The effectiveness of agri-environment schemes (AES) in enhancing biodiversity in agricultural landscapes is still strongly debated. In the Netherlands, one of the most widely implemented AES is the management of ditch banks to enhance plant species diversity. Previous research has shown that this type of AES has not led to increases in plant diversity. However, this work also showed that the success of this type of AES may depend on the presence of source populations in the surrounding areas. In this study we investigated if species-rich nature reserves can act as seed sources for agricultural ditch banks under AES and whether this function of nature reserves differs among plant species with different dispersal capacities. We used data collected by farmers over a 10 year period to analyse trends in species richness of target plants and in different dispersal groups in ditch banks under AES at different distances from nature reserves. Our results demonstrate that nature reserves can act as species rich sources in agricultural landscapes and that adjacent AES ditch banks can facilitate the colonisation of the surrounding agricultural landscape. However, the suitability of ditch banks as corridors depends on the dispersal capacity of a species. Particularly water-dispersed species clearly spread from nature reserves into the surrounding agricultural landscape along ditches. In contrast, species without adaptations to disperse over long distances do not show these spatiotemporal patterns.
Systematic planning and cultivation of agricultural fields using a geo-spatial arable field optimization service: Opportunities and obstacles
Bruin, S. de; Lerink, P. ; Riviere, I.J. la; Vanmeulebrouk, B. - \ 2014
Biosystems Engineering 120 (2014). - ISSN 1537-5110 - p. 15 - 24.
margins - biodiversity - landscape - farmland - machines - guidance - coverage - habitat
This paper describes a geo-spatial arable field optimization service (GAOS) and an assessment of users' experiences after three years of experimental operation. The service was developed in close cooperation with farmers. It allows farmers to optimize the locations of tracks within their fields, explore different options and download these to commercial Global Navigation Satellite System-guided steering systems. GAOS runs as a web service using standards defined by the Open Geospatial Consortium and is being operated by a group of farmers who received a few hours of training. The objective of optimization is to maximize efficiency by avoiding both inefficient turns and discontinuous swaths. Where applicable, released space is converted into field margins that meet environmental objectives and potentially generate additional income. The system provides dedicated functionality for geometrical operations, such as uploading and splitting of fields, merging and splitting of field edges, and manual editing of reference lines in the headlands. Acknowledged beneficial features include reduced expenditures on time and wasted resources and support for planning spraying paths. Given its complexity, most farmers preferred specialists to operate the system rather than operating it themselves. Future development should aim for simpler operation and full support for interactive coverage planning as well as computational optimization.
Life-history and ecological correlates of population change in Dutch breeding birds.
Turnhout, C.A.M. van; Foppen, R.P.B. ; Leuven, R.S.E.W. ; Strien, A.J. van; Siepel, H. - \ 2010
Biological Conservation 143 (2010)1. - ISSN 0006-3207 - p. 173 - 181.
global climate-change - extinction risk - migratory birds - netherlands - trends - conservation - biodiversity - farmland - declines - britain
Predicting relative extinction risks of animals has become a major challenge in conservation biology. Identifying life-history and ecological traits related to the decline of species helps understand what causes population decreases and sets priorities for conservation action. Here, we use Dutch breeding bird data to correlate species characteristics with national population changes. We modelled population changes between 1990 and 2005 of all 170 breeding bird species using 25 life-history, ecological and behavioural traits as explanatory variables. We used multiple regression and multi-model inference to account for intercorrelated variables, to assess the relative importance of traits that best explain interspecific differences in population trend, and to identify the environmental changes most likely responsible. We found that more breeding birds have increased than decreased in number. The most parsimonious models suggest that ground-nesting and late arrival at the breeding grounds in migratory birds are most strongly correlated with decline. Increasing populations are mainly found among herbivores, sedentary and short-distance migrants, herb- and shrub-nesting birds and large species with a small European range. Declines in ground-nesting and late arriving migrant birds suggest that agricultural intensification, eutrophication and climate change are most likely responsible for changes in Dutch breeding bird diversity. We illustrate that management strategies should primarily focus on the traits and causes responsible for the population changes, in order to be effective and sustainable.
Calibration of simulated rainfall characteristics for the study of soil erosion on agricultural land
Ries, J.B. ; Seeger, K.M. ; Iserloh, I. ; Wistorf, S. ; Fister, W. - \ 2009
Soil & Tillage Research 106 (2009)1. - ISSN 0167-1987 - p. 109 - 116.
drop size distribution - optical spectro pluviometer - hydrological response - rehabilitated areas - runoff - spain - management - distributions - farmland - basin
Rainfall simulation is a widely used method for soil erosion studies on agricultural land. Major problem of this experimental research method is the comparability between different simulators due to differences in simulated rainfall. Therefore the purpose of this study is to characterize the rainfall produced by a rainfall simulator which was widely used during the last decades. Four different calibration methods were used to assess the drop size distribution: (1) Indication Paper, (2) Plaster Micro Plot, (3) Joss–Waldvogel Disdrometer and (4) Laser Distrometer (Thies). Additionally, the latter one was used to measure drop fall velocity in combination with drop diameter. The spatial rainfall distribution pattern on the plot was measured with 100 rainfall gauges. The spatial rainfall distribution pattern clearly shows a heterogeneity, which is caused by the used nozzle configuration. Considerable differences in drop-size distribution can be observed depending on the used measurement technique. Laser Disdrometer and Plaster Micro Plot cover the whole produced drop size spectrum ranging from 3.0 mm, whereas Indication Paper as well as the Joss–Waldvogel Disdrometer primarily show drops smaller than 2.0 mm. Characterisation of rainfall is therefore strongly dependent on the used method and if different methods are used, may lead to contradictory results. The volume drop size distribution reflected by the Laser Distrometer is very similar to that one produced by rain with an intensity of 40 mm h-1. Nevertheless, with maximum velocities above 10 m s-1 small drops are by far too fast and large drops with velocities dominantly below 5 m s-1 are too slow compared to natural rainfall. As an overall result, the simulator can be characterised as suitable for runoff and infiltration measurements, but with constraints due to the low reproducibility of the spatial rain distribution. As a consequence of the produced drop spectrum and fall velocity the erosion quantities may be underestimated systematically. For this, methodological development has to be focussed on homogeneous spatial rainfall distributions and on increasing the amount of large drops with higher fall velocities
Do meadow birds profit from agri-environment schemes in Dutch agricultural landscapes?
Breeuwer, A.J.G. ; Berendse, F. ; Willems, F. ; Foppen, R. ; Teunissen, W. ; Schekkerman, H. ; Goedhart, P.W. - \ 2009
Biological Conservation 142 (2009)12. - ISSN 0006-3207 - p. 2949 - 2953.
godwit limosa-limosa - farmland - biodiversity - intensification - management - abundance - success
Since 1992 the European Union helps member states to reverse the loss of biodiversity in agricultural landscapes by the financial support of agri-environment schemes. Long-term studies investigating the effects of these schemes are an essential prerequisite for the development of an effective policy to restore biodiversity on farmland. In Dutch meadow landscapes almost all agri-environment schemes focus on the restoration of meadow bird populations by postponement of the mowing date. Between 1990 and 2002 we measured long-term changes in meadow bird densities in areas with and without agri-environment schemes in the Netherlands, both before and after the start of the contract. During these years bird territories were surveyed during five field visits between 15 March and 15 June. Densities of black-tailed godwit (Limosa limosa), and redshank (Tringa totanus) were higher in the areas with management agreements, but these differences were already present before the start of the contracts. After the start of the management contracts densities of black-tailed godwit and oystercatcher (Haematopus ostralegus) did not increase, while those of lapwing (Vanellus vanellus) and redshank even declined relative to the control areas. It is concluded that the current agri-environment schemes are not sufficient to restore meadow bird populations in Dutch agricultural landscapes. In addition to the prescribed postponement of the mowing date, it is probably necessary to raise groundwater levels and to reduce fertilization to allow for the development of an open vegetation structure that will increase chick survival to sufficiently high levels
Diagnosing declining grassland wader populations using simple matrix models
Klok, C. ; Roodbergen, M. ; Hemerik, L. - \ 2009
Animal Biology 59 (2009)1. - ISSN 1570-7555 - p. 127 - 144.
redshank tringa-totanus - godwits limosa-limosa - survival rates - conservation biology - breeding success - growth rate - management - netherlands - farmland - schemes
Many populations of wader species have shown a strong decline in number in Western-Europe in recent years. The use of simple population models such as matrix models can contribute to conserve these populations by identifying the most profitable management measures. Parameterization of such models is often hampered by the availability of demographic data (survival and reproduction). In particular, data on survival in the pre-adult (immature) stage of wader species that remain in wintering areas outside Europe are notoriously difficult to obtain, and are therefore virtually absent in the literature. To diagnose population decline in the wader species; Black-tailed Godwit, Curlew, Lapwing, Oystercatcher, and Redshank, we extended an existing modelling framework in which incomplete demographic data can be analysed, developed for species with a pre-adult stage of one year. The framework is based on a Leslie matrix model with three parameters: yearly reproduction (number of fledglings per pair), yearly pre-adult (immature) and yearly adult (mature) survival. The yearly population growth rate of these populations and the relative sensitivity of this rate to changes in survival and reproduction parameters (the elasticity) were calculated numerically and, if possible, analytically. The results showed a decrease in dependence on reproduction and an increase in pre-adult survival of the population growth rate with an increase in the duration of the pre-adult stage. In general, adult survival had the highest elasticity, but elasticity of pre-adult survival increased with time to first reproduction, a result not reported earlier. Model results showed that adult survival and reproduction estimates reported for populations of Redshank and Curlew were too low to maintain viable populations. Based on the elasticity patterns and the scope for increase in actual demographic parameters we inferred that conservation of the Redshank and both Curlew populations should focus on reproduction. For one Oystercatcher and the Black-tailed Godwit populations we suggested a focus on both reproduction and pre-adult survival. For the second Oystercatcher population pre-adult survival seemed the most promising target for conservation. And for the Lapwing populations all demographic parameters should be considered.
Development of biodiversity in field margins recently taken out of production and adjacent ditch banks in arable areas
Musters, C.J.M. ; Alebeek, F.A.N. van; Geers, R.H.E.M. ; Korevaar, H. ; Visser, A.J. ; Snoo, G.R. de - \ 2009
Agriculture, Ecosystems and Environment 129 (2009)1-3. - ISSN 0167-8809 - p. 131 - 139.
agri-environment schemes - intensively farmed landscapes - providing foraging resources - habitat quality - vegetation development - boundary vegetation - species richness - land-use - management - farmland
Taking field margins out of intensive cultivation is a common form of agri-environmental scheme and on-farm nature management. Typically, no nutrients or pesticides are applied in these margins, which may be sown either with a crop or with grasses and native flowering plants. In some cases the margins are mown, while in others they are left alone. Newly established grass margins are less species-rich than field boundaries or road verges with a long history, justifying the expectation that field margins, if properly managed and given time and appropriate seed sources, could develop into relatively species-rich vegetation. We studied the biodiversity of both margins taken out of production and adjacent ditch banks in the years following initial establishment of the margins. To this end we combined the data of three different projects in order to increase the sensitivity of the statistical analyses. The results showed that the plant species richness of the field margins increased in the years following establishment over a period of four years. In addition, shifts in species composition indicated a decrease in soil nitrate concentrations. The species richness of both butterflies and dragonflies may increase. The most striking result was the marked increase in the plant species richness of the adjacent ditch banks in the five years following creation of the margins. Here, too, changes in species composition indicated a decrease in soil nitrate. In the years following establishment of the field margins there was no increase in the cover of agriculturally harmful weeds in these margins. However, the number of harmful nematodes increased. Our results show the short term effect of establishing field margins. Long term effects are still in need for further research.
Identifying predators of eggs and chicks of Lapwing Vanellus vanellus and Black-tailed Godwit Limosa limosa in the Netherlands and the importance of predation on wader reproductive output
Teunissen, W. ; Schekkerman, H. ; Willems, F. ; Majoor, F. - \ 2008
Ibis 150 (2008)Suppl. 1. - ISSN 0019-1019 - p. 74 - 85.
crow predation - nest-predation - success - population - management - farmland - grasslands - survival - britain - birds
Farmland bird populations in the Netherlands have shown an accelerating decline in recent years, despite extensive conservation efforts including reserves, agri-environment schemes and protection of nests by volunteers. Although agricultural intensification is the main cause underlying these declines, there is a growing concern that the ongoing decline of grassland-breeding shorebirds in recent years is caused or aggravated by increasing predation. Although Red Fox Vulpes vulpes and Carrion Crow Corvus corone are often accused of causing widespread breeding losses, and calls for management of these species are made, very few field data are available on the incidence of predation on grassland shorebirds and the relative importance of different predators. To obtain such data, we identified egg predators using temperature loggers and continuous video recordings of 792 clutches, and chick predators by radiotagging 662 chicks of Black-tailed Godwit Limosa limosa and Northern Lapwing Vanellus vanellus. In total, 22 species were identified as predators of eggs or chicks, of which Red Fox, Common Buzzard Buteo buteo, Grey Heron Ardea cinerea and Stoat Mustela erminea were the most frequent. Eggs were taken primarily by mammals and chicks more often by birds. There was great variation in predation levels and species involved in predation of clutches between sites and years, but less in chick predation. Hence, there was no correlation between predation levels on clutches and those on chicks within the same sites. In sites where more then 50% of clutches were lost to predation, however, nocturnal predators took the larger share. As temporal and spatial variation on a small scale significantly influences predation levels, a site-specific approach based on sound knowledge of the local situation will be more effective in reducing predation on farmland birds than general, country-wide measures. Calculations based on our data indicate that eliminating only one loss factor at a time will often not reverse a local population decline, and provide a strong argument for targeting several locally limiting factors simultaneously instead of focusing on mitigation of predation alone.
Open-space preservation in the Netherlands: Planning, practice and prospects
Koomen, E. ; Dekkers, J. ; Dijk, T. van - \ 2008
Land Use Policy 25 (2008)3. - ISSN 0264-8377 - p. 361 - 377.
ruimtelijke ordening - physical planning - growth-management - land-use - urban containment - housing prices - policies - future - farmland - dynamics - england - lessons
Open-space preservation is a planner's issue that is constantly debated, in particular on the success of the implemented instruments. Assessments of policy effectiveness face many methodological problems that are briefly discussed here. We choose to analyse the contribution of Dutch policies to open-space preservation by comparing actual land-use developments within different restrictive planning regimes. The presented analysis differs from comparable efforts that usually rely on census statistics through its use of local-level geographical data and spatial analysis techniques. Our approach has the advantage of being able to analyse the impact of spatially explicit regional zoning regulations. In addition to comparing regions with strict and less strict regimes, this paper also assesses the importance of another open-space characterisation. The latter refers to a distinction in agriculturally shaped and exploited landscapes and natural areas. We conclude the analysis with a discussion on possible spatial planning implications.
Evaluation of meadow bird management, especially black-tailed godwit (Limosa limosa L.), in the Netherlands
Melman, T.C.P. ; Schotman, A.G.M. ; Hunink, S. ; Snoo, G.R. de - \ 2008
Journal for Nature Conservation 16 (2008)2. - ISSN 1617-1381 - p. 88 - 95.
agri-environment schemes - dutch agricultural grasslands - breeding birds - biodiversity - landscapes - farmland - habitat
Although the protection of meadow birds (amongst others Limosa limosa L.) is a key focus of Dutch nature conservation policy, management schemes (nature reserves and agri-environmental schemes) are not having the desired effect. This study examines the extent to which the disappointing results are related to suboptimal location of the managed sites. First, the extent to which the sites are located outside the core meadow bird area is assessed. Next, the proportion of sites affected by constraints, i.e. road traffic noise, landscape closure, excessive drainage and high predation pressure is analysed. For approximately 43% of these grounds it appears that management effects might be hampered by the aforementioned constraints. The extent to which the findings can explain the lack of ecological effectiveness is then discussed. Finally, we consider how the meadow bird area (ca. 570,000 ha) might be managed more effectively through spatial optimisation and how to do so without undermining the support of those carrying out day-to-day management (especially farmers and volunteers).
Direct and indirect effects of the most widely implemented Dutch agri-environment schemes on breeding waders
Verhulst, J. ; Kleijn, D. ; Berendse, F. - \ 2007
Journal of Applied Ecology 44 (2007)1. - ISSN 0021-8901 - p. 70 - 80.
lapwings vanellus-vanellus - site-fidelity - agricultural intensification - natal philopatry - food resources - birds - management - habitat - farmland - biodiversity
1. In the Netherlands, agri-environment schemes are an important tool for halting the ongoing decline of meadow birds and, in particular, waders breeding on wet meadows. The effectiveness of the main scheme, postponed mowing, is heavily debated because it does not result in higher breeding densities. Recently, agri-environmental collectives have become involved in the co-ordination of scheme applications and additional measures have been introduced. One of them is per-clutch payment: farmers are paid per wader clutch without being restricted in their farming practices. 2. We evaluated the effectiveness of the combination of the two measures, postponed mowing and per-clutch payment, by determining the number of birds and territories on 12.5-ha plots where both measures (on average 1.6 ha postponed mowing and 10.9 ha per-clutch payment) were being implemented. Conventionally managed grasslands served as controls. Additionally, on a field with postponed mowing and a paired control field, we measured a number of environmental factors that might influence wader distribution. 3. On plots operating a combination of postponed mowing and per-clutch payment, more territories of all bird species were found and more redshanks Tringa totanus were observed. The same pattern occurred on fields with per-clutch payment alone. On fields with postponed mowing alone, we found more territories of the most abundant wader species but on conventional fields we observed more lapwings Vanellus vanellus. 4. The positive effects of postponed mowing on wader territories were probably caused by small differences in soil moisture and groundwater level between the two field types, as inclusion of these factors in a general linear model rendered all scheme effects insignificant. 5. Postponed mowing affected the form and amount of fertilizer applied to the fields as well as available nitrogen, but none of the other environmental factors that were measured. Additional analyses identified groundwater depth, penetration resistance and prey density (earthworms, Lumbricidae, and leatherjackets, Tipulidae larvae) as the main factors determining wader density. 6. Synthesis and applications. Our results show that conservation measures consisting of postponed mowing and per-clutch payment implemented by agri-environment collectives do not support a higher abundance of waders but do support marginally higher breeding densities of waders compared to conventional farms. These results are probably due to differences in soil moisture and groundwater depth. The effectiveness of agri-environment schemes directed towards conservation of waders might be enhanced by including raised groundwater levels into scheme prescriptions.
Impacts of land-use change on biodiversity: An assessment of agricultural biodiversity in the European Union
Reidsma, P. ; Tekelenburg, T. ; Berg, M.M. van den; Alkemade, R. - \ 2006
Agriculture, Ecosystems and Environment 114 (2006)1. - ISSN 0167-8809 - p. 86 - 102.
grazing management - succulent thicket - bird populations - south-africa - diversity - vegetation - abundance - landscape - farmland - insect
The objective of this study is to assess land-use intensity and the related biodiversity in agricultural landscapes of the EU25 for the current situation (2000), and explore future trends, based on the four EURURALIS scenarios up to 2030. Data from the Farm Accountancy Data Network (FADN) were used to classify farm types in 100 regions of the EU15, according to agricultural intensity. For the ten New Member States (EU10), which are not yet considered by the FADN, country level data were used to obtain similar farm types. Three processes were considered for the assessment of future trends in agricultural land-use intensity: (1) land-use change, (2) conversion into organic farming, and (3) changes in productivity of crop and grassland production. An ecosystem quality value was attributed to each farm type according to dose-effect relationships between pressure factors and biodiversity compared to the value for an undisturbed situation. The biodiversity in agricultural landscapes was then calculated as the average ecosystem quality multiplied by the relative area size of each farm type within a region. A similar method of attributing ecosystem quality values to other land-use types allowed comparison between different land-use types. Referring to the current situation, results indicate the lowest ecosystem quality values to be found in intensively used agricultural areas in lowlands (e.g. The Netherlands and northern France) and irrigation systems (e.g. Greece), whereas relatively high values are found in Spain and the New EU Member States. Scenario results show that for the A1 scenario (Global economy), the highest loss in ecosystem quality will take place in all regions in croplands and grasslands. The B2 scenario (Regional communities) provides the best opportunities to improve ecosystem quality of agricultural landscapes. In most scenarios, agricultural land is decreasing, while the remaining agricultural areas tend to be used more intensively. The negative impact of intensification on biodiversity is partly set off by (active or spontaneous) nature development on abandoned agricultural areas, but the overall trend seems to be generally negative. The strength of this methodology is that it provides a quick overview of land-use intensity change and biodiversity trends. Through the use of this farm-type level of analysis we have provided a good picture of the differences in land-use intensity and the related biodiversity between the EU regions and the scenarios
Influence of seed density and aggregation on post-dispersal weed seed predation in cereal fields
Marino, P.C. ; Westerman, P.R. ; Pinkert, C. ; Werf, W. van der - \ 2005
Agriculture, Ecosystems and Environment 106 (2005)1. - ISSN 0167-8809 - p. 17 - 25.
mice apodemus-sylvaticus - arable habitat use - food preferences - bank - population - magnitude - emergence - abundance - farmland
The importance of density dependence, aggregation and background density of seeds on intensity of seed predation in cereal fields were examined in central Netherlands. Four sequential 1-week trials were conducted from 9 July to 8 August 2001 and lamb's quarters (Chenopodium album) was used as the test species. C. album was offered to potential predators by lightly adhering seeds to small strips of sand paper. The interaction between spatial scale and density dependence was tested at a large (varying seed density/block) and a small (varying seed density/card) spatial scale. Three distributions (random, even, aggregated) and two background (seed cards presented in plots with none versus many C. album seeds added to the soil) treatments were tested, all experiments being conducted simultaneously but in different fields. There was no large spatial scale density effect but in Week 4, a higher proportion of seeds was removed from the low-density seed cards. In the distribution study, significantly more seeds were removed from the aggregated distribution treatment in Week 2. In the background density study, predation was highest in Week 2 of the high background density treatment. In all experiments, there was considerable temporal and spatial variation in the intensity of seed predation. The importance of seed in the diet of seed predators declined with time, whereas the presence or the absence of density dependent predation was likely to be a function of the spatial scale at which densities were enhanced.
The ecological effectiveness of agri-environment schemes in different agricultural landscapes in The Netherlands
Kleijn, D. ; Berendse, F. ; Smit, R. ; Gilissen, N. ; Smit, J. ; Brak, B. ; Groeneveld, R.A. - \ 2004
Conservation Biology 18 (2004)3. - ISSN 0888-8892 - p. 775 - 786.
diversity - conservation - consequences - biodiversity - restoration - countryside - populations - intensity - farmland - europe
Agri-environment schemes are an instrument used by western European countries to counteract the negative effects of contemporary agriculture on biodiversity, but not much is known about their effectiveness. We investigated the ecological effects of Dutch agri-environment schemes aimed at promoting botanical diversity or meadow birds, and we tested whether the effectiveness of the schemes depends on landscape type or structure. In three different types of landscape, we surveyed plants, birds, bees, and hover flies on 78 paired fields that either had agri-environment schemes or were managed conventionally, and we collected data on a range of different environmental variables. Neither plant species richness nor abundance of meadow birds was higher on fields with agri-environment schemes. Landscape type had a significant effect on both species groups, but the effects of the schemes were independent of landscape type. Neither the diversity of plants nor the abundance of birds was related to any of the environmental variables. Agri-environment schemes designed to promote plant species richness or bird abundance did have positive side-effects because they enhanced the species richness of bees and hover flies, irrespective of the type of landscape. Furthermore, landscape type, groundwater level (hover flies), and area of wooded edges (bees) significantly affected both species groups. The failure of the schemes to promote the target species may be related to the high intensity of land use in The Netherlands. Simple conservation measures taken by farmers may not be sufficient to counteract the impact of factors that are often controlled at the landscape level (e.g., hydrology). Similar studies in other countries are needed to place the results of our study into a European context. Keywords: bees; biodiversity conservation; farmland; hover flies; meadow birds; policy evaluation; vegetation; aves de praderaabejas; conservació; n de biodiversidad; evaluació; n de polí; ticas; moscas; tierra de cultivo; vegetació; n
Relative importance of vertebrates and invertebrates in epigeaic weed seed predation in organic cereal fields
Westerman, P.R. ; Hofman, A. ; Vet, L.E.M. ; Werf, W. van der - \ 2003
Agriculture, Ecosystems and Environment 95 (2003)2-3. - ISSN 0167-8809 - p. 417 - 425.
mice apodemus-sylvaticus - agricultural landscape - postdispersal predation - harpalus rufipes - coleoptera - carabidae - farmland - habitat - maine
Exclosure trials were conducted in four organic cereal fields in The Netherlands in 1999 and 2000 to determine the relative importance of vertebrates and invertebrates in weed seed predation. The trials showed that seed predation by vertebrates was rather consistent and predictable, occurring on all fields and both years, being low early in the season, increasing towards mid-June and decreasing thereafter. The occurrence and level of seed predation by invertebrates were unreliable and unpredictable over time. Predation by both vertebrates and invertebrates showed no apparent pattern related to field margin. Vertebrates, presumably mice, accounted for the larger part of weed seed consumption (30-88% per fortnight and farrn). Invertebrates, probably granivorous ground beetles, accounted for the smaller part of seed consumption (4-38%). They were the dominant seed predators in only one out of eight cases in July 1999 (74%), and overall contributed little to variability in seed predation