Ditch Banks Research Articles

Greater Anis (Crotophaga major) Commensal Foraging with Freshwater Fish in the Pantanal Floodplain, Brazil

Foraging associations between birds and other groups of animals have been widely reported in the literature. I report the first observation of a foraging tactic involving a flock of Greater Ani (Crotophaga major), which deliberately followed fish along an artificial ditch in the Pantanal wetlands, feeding on animals flushed by the movement of the vegetation on the ditch banks. Further observations of the feeding behavior and foraging tactics of Greater Anis are necessary to ascertain if this type of behavior is a frequent event or merely sporadic.

Effects of mowing date on the opportunities of seed dispersal of ditch bank plant species under different management regimes

Mowing and plant removal is a traditional practice in low-intensity farming and likely to lead to high plant species richness. Even today, scientific knowledge on the impact of mowing on seed availability is still very limited. We studied whether the seed availability of ditch bank plant species was affected by the timing of mowing and, if so, whether the effect varied according to management regime (nature reserve, agri-environment scheme (AES) with long-term management, AES with short-term management, conventional management). Our focus was on seed availability for transportation, because restoration of ditch bank vegetation is known to be limited by seed dispersal. The presence and seed-setting of 25 target species in 384 plots were recorded at the mowing date, under four management regimes. A Hierarchical Generalised Linear Model (HGLM) was used to analyse the effects of mowing date and management on the number of species setting seed. It suggests that when the mowing is twice annually, mowing on July 1st and on September 1st will result in a maximum number of species of which the seeds are available for transportation and, therefore, create largest opportunities for seed dispersal on ditch banks in the western peat area of the Netherlands. The effect of mowing date differs among species, with certain rare species like Caltha palustris and Lythrum salicaria in particular differing from the commoner species. A flexible mowing regime varying from year to year would therefore help to protect these rare species. The later peak in seed-setting found in nature reserves and long-term AES suggest a postponed mowing compared to conventionally management and short-term AES.

Spatiotemporal variation of plant diversity on ditch banks under different management regimes

Agricultural intensification has led to a loss of biological diversity at various spatial and temporal scales and understanding the mechanisms driving these changes would help target conservation efforts accordingly. In this study we used additive partitioning of diversity and the Jaccard index of similarity to estimate the spatial and temporal patterns of plant diversity on ditch banks under different management regimes (nature reserves and agricultural areas). We focused on a total of 118 species, including 18 indicator species of conservation interest, at 42 sites in three successive sampling periods. For all species taken together, beta diversity contributed most to total observed species diversity, but was less than expected under random distribution. Indicator species showed greater beta diversity on a spatial scale compared to all species, but much less so on a temporal scale. Importantly, the differences in indicator species composition on a spatial scale are probably due to environmental heterogeneity and dispersal limitation, indicating that management strategies should focus on both factors. Nature reserves showed higher alpha diversity within sites because of possible lower nutrient inputs and grazing intensity compared with agricultural areas, while both exhibited scale-dependent dispersal limitation.

History of Ecological Sciences, Part 37: Charles Darwin's Voyage on the Beagle

History of Ecological Sciences, Part 37: Charles Darwin's Voyage on the Beagle

Spatial variation in ditch bank plant species composition at the regional level: the role of environment and dispersal

Questions: Can patterns of species similarity on ditch banks be explained by environmental and dispersal factors and, if so, to what extent? Does the pattern of distance decay differ among different species groups (all species versus target species of conservation interest; species of different dispersal type)? Location: Krimpenerwaard, the Netherlands. Methods: In 2006-2007, ditch bank vegetation data on 130 terrestrial herbaceous species were collected on 72 plots. Species similarity was measured and related to environmental distance (soil type and nutrient level) and dispersal distance (geographic distance and limitation of dispersal by water, wind and agricultural activities) as explanatory factors using multiple regression on distance matrices (MRM). Differences in rates of distance decay in species similarity among different subsets of data (species groups) were investigated using randomization tests. Results: In all species, patterns of similarity of composition are influenced mainly by variations in dispersal, while for target species these are due to combined effects of environmental and dispersal variation. Compared with species using other dispersal mechanisms, water-dispersed species had half the rate of distance decay. Conclusions: For all species considered here, dispersal limitation seems more responsible for the spatial variation in species composition than environmental determinism. Conservation management focused on plant species diversity would be more successful in areas adjacent to those where a similar management regime is already in force. For target species of conservation interest, besides dispersal limitation, environmental determinants like nutrient level are also important. As a means of conserving such target species, therefore, focusing on reducing nutrient levels and facilitating species dispersal will be more effective than current management practices, which mainly focus on reducing fertilizer inputs.

Vegetation development in sown field margins and on adjacent ditch banks

The creation of temporal and newly sown field margins for 6 years is a common agri-environment scheme (AES) in the Netherlands. Conservation profits resulting from AES vary over different areas and need further studying. We examined plant species richness in such field margins and adjacent ditch banks in the province of Zeeland, where these linear elements do not experience plant biomass removal after mowing as management strategy. First, during 2 years, we inventoried field margins sown with a wildflower mixture and related the species composition and richness to the age of the margins. In a second assessment, we studied plant species richness on ditch banks protected from arable fields by these margins. Major clusters in a principal component analysis (PCA) on species composition in the field margins showed a succession from sown and ruderal annual species (year 1), to sown perennial species (year 2) and ending with a dominance by tussock forming grass species and Urtica dioica (year 5–6). Total plant species richness decreased with increasing age of the margins, and this was caused by the combination of a decline in sown species and a stable number of not-sown species. The presence of field margins during several years did not result in an increase in plant species richness on adjacent ditch banks. In both the field margins and on the ditch banks, mowing management is not followed by the removal of the cuttings. For plant conservation, the results of these field margins are disappointing, probably due to the lack of a proper management. Therefore, we recommend implementing a hay-making and opening management, to increase plant richness and to reduce noxious weeds in the margins and on the ditch banks.

The dispersal and deposition of hydrochorous plant seeds in drainage ditches

Summary1. Surface water is an important dispersal vector for wetland plant species. However, most previous studies on hydrochory (i.e. water dispersal) have focused on ecosystems with relatively rapid water flow. Therefore, there is a need to study such dispersal in slow‐flowing or stagnant waterbodies, such as drainage ditches, which might act as dispersal corridors between habitat patches.2. To gain insight into the mechanisms by which seeds are transported in drainage ditches, the effect of the velocity of wind and water on the rate of transport of floating seeds of three wetland species (Carex pseudocyperus L., Iris pseudacorus L. and Sparganium erectum L.) was investigated. Furthermore, in release and retrace experiments with painted C. pseudocyperus seeds, a number of factors potentially determining the probability of seed deposition were investigated.3. Net wind speed was found to be the main factor determining the rate at which seeds are transported in drainage ditches. No relation between water flow at middepth in the ditches and seed transport was found. Wind speed and flow at the water surface were positively related. The effect of wind speed on the rate of transport of floating seeds was greater for S. erectum seeds, because a greater ratio of their volume protrudes from the water, than for C. pseudocyperus and I. pseudacorus seeds.4. The principal factors that determine seed deposition were aquatic plant cover, ditch slope and indentations in the ditch bank. Seeds changed direction if the wind direction changed, or if there was a bend in the ditch. The final pattern of deposition was related to mean net wind speed. Mean transport distance after 2 days varied between 34 and 451 m.5. Unlike in rivers, seed transport in ditches was determined by wind speed and direction, enabling multidirectional seed dispersal. We conclude that in slow‐flowing waters, wind is a more important driver for hydrochorous seed transport than the flow of water. This sheds a new light on hydrochory and has important consequences for the management of otherwise fragmented wetland remnants.

Synergy between nature reserves and agri-environmental schemes in enhancing ditch bank target species plant diversity

The issue of what conservation strategies to apply in agricultural landscape for the most effective protection of biodiversity has been debated for some years. The creation and maintenance of nature reserves is often hampered by both ecological and economic factors, while the ecological effectiveness of agri-environment schemes (AES) is still being queried. Our study examined how the spatial pattern of nature reserves and AES affects the diversity of 25 target species of conservation interest in ditch banks and how this information might be used to develop a strategy resulting in synergy between protected areas and enhanced matrix quality. We studied target species plant diversity on 92 ditch banks under AES and on 102 banks not under such a regime; all of them running parallel to nature reserves. We compared the results with those obtained from a previous study which focused on ditch banks running transverse. On non-AES ditch banks running parallel to nature reserves, there was a significant decline in species richness with increasing distance from the nature reserve while this was not the case for AES ditch banks. The effect of AES differed between the two directions, with a significant effect beyond 200 m in the parallel direction and within 200 m in the transverse direction. Our results indicate that synergy between nature reserves and AES can enhance plant diversity and, since the AES effect was different in different direction due to wind direction and nitrogen input to adjacent fields, location of AES should be chosen carefully.

Evaluating management interventions in small populations of a perennial herbPrimula vulgarisusing spatio-temporal analyses of point patterns

Summary 1. In high-intensity agricultural landscapes, small landscape elements such as hedgerows, ditch banks, and rows of pollard trees may represent the last refuge of many plant and animal species, some of them being rare or even threatened with extinction. However, due to their small size and low habitat quality, long-term population survival cannot be ascertained and often active management is needed to maintain viable populations of species forced to survive in these small landscape elements. 2. Population models are needed to assess the threats to species at risk and to evaluate alternative management actions. Here, we present a methodology to evaluate management interventions using spatio-temporal analyses of point patterns. We apply this method to several populations of primrose Primula vulgaris in Flanders, where it is rare and predominantly occurs along ditch banks. 3. The effects of ditch bank clearing on the establishment success of seedlings was investigated by comparing spatial patterns of seedling recruitment, survival and mortality between populations that were grazed and populations that were severely disturbed by mechanical clearing of ditch banks followed by annual mowing. A total of 884 seedlings were mapped and monitored during 4 consecutive years (1999–2002). 4. In all populations, plants showed significant clustering, but in cleared sites only seedlings were significantly clustered around adults. Spatial patterns of mortality varied according to the management intervention. In grazed sites, mortality was almost random, whereas in cleared sites we found clear evidence for strong negative density-dependent mortality. There was no evidence that the presence of adults affected survival of recruits in any of the sites studied. 5. Synthesis and applications. This study shows that the analysis of spatial point patterns contributes to our understanding of the population dynamics of plant species occurring in different environments. The approach can be broadly applied to other plant species to elucidate the processes that determine the number of individuals that establish and persist into later life stages and will help conservation managers to refine management strategies intended to conserve or restore plant populations. In the case of P. vulgaris, increasing the availability of microsites is most likely to result in increased growth rates, as it results in increased recruitment and establishment of recruits.

Abundance of invertebrate prey for birds on organic and conventional arable farms in the Netherlands

SummaryAs a result of agricultural intensification, populations of farmland birds have been in steep decline for several decades. Reduction in food abundance has been mentioned as one factor behind these declines. Extensive farm management, such as use of organic methods, is expected to provide more food for birds. In this study we compared invertebrate prey abundance for birds during the breeding season between organic and conventional arable farms. We made comparisons for three different groups of birds: (1) birds feeding on soil-living invertebrates (earthworms), (2) birds feeding on ground-dwelling invertebrates and (3) birds feeding on aerial invertebrates. Invertebrate abundance was compared between organic and conventional farms, crop and non-crop habitats, and between crop and non-crop habitats under the same farm management. On organic sites, earthworm abundance was 2–4 times higher than on conventional sites, but no differences were found between crop types. Total abundance of ground-dwelling invertebrates did not differ between organic and conventional sites, but positive effects were found for several individual taxonomic groups, such as carabid beetles and spiders. On organic farms, invertebrate abundance was higher in carrots, cereals and onions compared to other crops; on conventional farms this was true for onions. When compared with most crops, ground-dwelling invertebrate abundance was low in uncropped field margins and on ditch banks. On organic farms, aerial invertebrate abundance was approximately 70% higher than on conventional farms. On cereal fields, aerial invertebrates were especially abundant.

Herbicide Options for Rice Cutgrass (Leersia oryzoides) Control

Rice cutgrass is encroaching into rice fields from ditch banks and canals, especially into continuous rice fields where tillage is limited in the Mississippi Delta region of Arkansas. Experiments were conducted to evaluate the effectiveness of various herbicides applied alone on rice cutgrass and to determine if the effectiveness of bispyribac on rice cutgrass is influenced by number of applications, adjuvant type, and adjuvant rate. Glyphosate, glufosinate, and clethodim were the most effective herbicides when applied alone; however, none of these are labeled for over-the-top application in rice. Of those herbicides that can be applied over the top of rice, imazethapyr and bispyribac were the most effective, providing 52 to 62% rice cutgrass control, albeit imazethapyr can be used only in imidazolinone-resistant rice. The addition of an adjuvant to bispyribac improved rice cutgrass control, and sequential bispyribac applications were generally superior to a single application. Methylated seed oil/organosilicone/urea ammonium nitrate adjuvant increased rice cutgrass control with bispyribac, especially when bispyribac was applied as a single application. A single application of imazethapyr, bispyribac, halosulfuron, penoxsulam, clomazone, thiobencarb, cyhalofop, propanil, quinclorac, and fenoxaprop provided less-than-acceptable control, which partially explains the difficulty that growers are experiencing in controlling rice cutgrass, especially in continuous rice production.

Restoration of plant diversity on ditch banks: Seed and site limitation in response to agri-environment schemes

Recently it has become clear that seed limitation is probably a much more important factor in plant recovery than has often been recognized. However, in practice, restoration measures that are focussed on decreasing site limitation may actually increase seed limitation. We tried to determine whether the effects of restoration measures affect site or seed limitation or both. An experiment was set up on ditch banks in the Netherlands which applied agri-environment schemes (AES). To investigate whether nature reserves (seed source) can improve species diversity on the surroundings and to what extent AES is improving this function, we studied the plant diversity (presence of individual species and species richness) of ditch bank vegetations in relation to increasing distance from nature reserves. The presence or absence and species richness of 25 target plants were assessed in 26 ditch banks with AES and 36 non-AES at 15 plots each differing in distance to a nature reserve. Data were analyzed using a Hierarchical Generalized Linear Model (HGLM) with species richness and presence of individual species as response variables and distance to nature reserve and application of AES as factors, controlling for possible confounding factors. Results were interpreted as the effects of AES on seed and site limitation of the species. The results showed that plant diversity decreased significantly with distance from source populations. There were considerable differences in species diversity between AES and non-AES ditch banks, with the former showing greater plant diversity especially in the first 200 m from nature reserves. Presences of all individual species decreased with distance to nature reserve, but the strength of this relationship and the AES effects differed among species. AES ditch banks had lower site limitations for most plant species, but did not have lower seed limitation.

First Report of Crown Gall Caused by Agrobacterium tumefaciens on Euphorbia esula/virgata in Europe.

Hypertrophy and hyperplasia resembling crown galls were found on roots of Euphorbia esula/virgata at a single site in east-central Hungary in 2005. E. esula/virgata, known as leafy spurge in North America, is an invasive species causing substantial economic losses to the value of grazing lands in the Northern Great Plains of the United States and is the target of biological control. E. esula/virgata is widely distributed throughout Eurasia and is found on ditch banks, along roadsides, and in other noncultivated areas in its native range. Large galls on roots resembling crown gall were first noted in 1992 on plants collected for phylogenetic studies from three locations in east-central Hungary. One of these sites was relocated during a 2005 survey and galls were collected from infected plants. Galls were diced and incubated overnight in tubes containing 3 ml of sterile water at room temperature (20 to 25°C). The supernatant was streaked onto plates of potato dextrose agar (PDA), medium 1A, medium 2E, and Roy/Sasser medium. After 7 days, colonies were picked and streaked and subsequently purified on PDA. Of 104 isolates used to inoculate three sunflower plants each (by puncturing roots just below the soil line with a sterile dissecting needle holding a drop of fluid matrix containing bacterial cells), 35 caused galls. Thirty-three isolates were randomly selected from the 104 and used to inoculate three tomato plants each at the soil line. Seventeen caused galls, including two isolates that did not cause galls on sunflower. Finally, none of 20 randomly selected isolates caused galls on kalanchoe plants (Kalanchoe blossfeldiana). Three isolates, which formed the largest galls on sunflower, were used to inoculate five plants of E. esula/virgata growing in a 1:1:1 (peat/sand/Bozeman silt loam) potting mix. The tests were repeated. Galls were visible on inoculated plants within 6 weeks. Diagnostic biochemical tests done prior to and after reisolation indicated that the causal agent was Agrobacterium tumefaciens, which differed from A. rhizogenes in the production of alkali from litmus milk, a positive reaction for the ferric ammonium citrate and 3-ketolactose tests, and negative reactions for tests to detect the production of acid from erythritol and alkali from malonic, l-tartaric, and mucic acid. The three isolates of A. tumefaciens from E. esula/virgata had identical sequences and clustered most closely (99.8 to 99.9% similarity) with five isolates of A. tumefaciens from Tibet and Japan on the basis of cluster analysis using 16S rRNA sequences. Crown gall of E. esula/virgata has also been found in Montana and western North Dakota, and isolates were identified as A. tumefaciens biovars 1 and 2 (1) (the latter is now known as A. rhizogenes). To our knowledge, this the first report of crown gall on E. esula/virgata in Europe. Reference: (1) A. J. Caesar. Plant Dis. 78:796, 1994.

No improvement of plant biodiversity in ditch banks after a decade of agri-environment schemes

Abstract Restoring plant species richness in intensively farmed areas by means of agri-environment schemes (AES) seems particularly difficult. We studied the effectiveness of a decade of AES in enhancing biodiversity in ditch banks on six modern dairy farms in the Western Peat District in the Netherlands, taking into account the roles of local productivity and of regional diversity and productivity. Biodiversity is characterised as total number of vascular plant species and number of target plant species and productivity as biomass, Ellenberg N -value and grass/forb ratio. We analyzed the repeated AES releves sampled in two periods, 1993–1995 and 2000–2003 and the diversity–productivity relationships in space and over time. For the analysis of the role of the regional factors, repeated AES and reference releves were compared. Number of target species remained stable, whilst the total number of species decreased, and the productivity increased in general in AES ditch banks. We found a clear negative diversity–productivity relationship in space and over time. AES ditch banks showed higher total number of species and comparable to higher number of target species than the reference ditch banks, in general, however, the productivity was also lower in AES ditch banks. The development of AES ditch banks was similar to the regional developments, although differences tended to become smaller in the study period. We hypothesize that the main reason that ditch bank AES do not overall successfully reduce productivity, is because the AES also recommended late mowing and that because of colonization constraints, the region cannot contribute to a positive development. Improvement of AES should, therefore, include adaptation of the mowing regime in high-productivity situations as well as regional strategies to restore the biodiversity of the ditch bank flora.

Development of biodiversity in field margins recently taken out of production and adjacent ditch banks in arable areas

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.

Mass Rearing of Pseudophilothrips ichini (Thysanoptera: Phlaeothripidae), an Approved Biological Control Agent for Brazilian Peppertree, Schinus terebinthifolius (Sapindales: Anacardiaceae)

Raddi, native to Argentina, Brazil, and Paraguay(Barkley 1944), is a non-native invasive weed inFlorida (Langeland & Burks 2008), California(Randall 2000), Hawaii (Hight et al. 2003), andTexas (Gonzalez & Christoffersen 2006). Thiswoody ornamental most likely was introducedinto Florida before 1900 (Morton 1978; Mack1991). It eventually escaped cultivation and is aserious problem in disturbed sites (e.g., fallowfarmlands, ditch banks), natural communitiessuch as pinelands, hardwood hammocks andmangrove forests, and the Everglades NationalPark (Toops 1979; Ewel et al. 1982).During the mid-1980s, Brazilian peppertreewas targeted for classical biological control inFlorida (Bennett et al. 1990; Habeck 1995). Thelong-term goal of this project is to introduce acomplex of specialist natural enemies into Floridathat are capable of selectively attacking and re-ducing the invasiveness of Brazilian peppertree.Surveys for natural enemies within the areas ofnatural distribution of Brazilian peppertree havebeen conducted, and biological and host rangestudies have been completed for several candi-date biological control agents (Cuda et al. 2006).In May 2007, the federal interagency TechnicalAdvisory Group for the Introduction of BiologicalControl Agents of Weeds (TAG) recommended therelease from quarantine of the stem-attackingthrips

Effect of Land Cover Data on Nitrous Oxide Inventory in Fen Meadows

Landscape representations based on land cover databases differ significantly from the real landscape. Using a land cover database with high uncertainty as input for emission inventory analyses can cause propagation of systematic and random errors. The objective of this study was to analyze how different land cover representations introduce systematic errors into the results of regional N2O emission inventories. Surface areas of grassland, ditches, and ditch banks were estimated for two polders in the Dutch fen meadow landscape using five land cover representations: four commonly used databases and a detailed field map, which most closely resembles the real landscape. These estimated surface areas were scaled up to the Dutch western fen meadow landscape. Based on the estimated surface areas agricultural N2O emissions were estimated using different inventory techniques. All four common databases overestimated the grassland area when compared to the field map. This caused a considerable overestimation of agricultural N2O emissions, ranging from 9% for more detailed databases to 11% for the coarsest database. The effect of poor land cover representation was larger for an inventory method based on a process model than for inventory methods based on simple emission factors. Although the effect of errors in land cover representations may be small compared to the effect of uncertainties in emission factors, these effects are systematic (i.e., cause bias) and do not cancel out by spatial upscaling. Moreover, bias in land cover representations can be quantified or reduced by careful selection of the land cover database.

The effect of agri-environment schemes on amphibian diversity and abundance

The Western Peat District of The Netherlands has a characteristic Dutch landscape. It consists mainly of meadows for dairy farming, crisscrossed by a dense network of ditches. Its biodiversity is regarded as of high national and international importance, but is declining as a result of intensive farming. Besides the establishment of reserves, measures to conserve and restore biological diversity have been implemented in the form of agri-environment schemes (AES). The aim of this research is to investigate, first, whether the reserves, assuming these provide source populations, affect the distribution of amphibians and, second, whether AES in the form of nature-friendly ditch bank management benefits amphibian diversity and abundance and enhances distribution across the agricultural landscape. In total, 42 ditches (24 control ditches and 18 AES ditches) were studied. Each ditch was perpendicular to the boundary of one of the reserves and was divided into five ditch sections of 100m spread over 800m, starting in the reserve and proceeding into the farmland. Generalized Linear Modelling was used to quantify the effect of nature-friendly ditch bank management (AES) and distance to the nature reserve on amphibian diversity and abundance. Species richness was high in AES ditches as compared to control ditches. The number of observed green frog (Rana esculenta synkl.) seemed to decline in the control ditches at large distances from the reserve. The other species, although their abundances were higher in the reserves, did not show a declining trend across the farmland. However, all adult amphibians except green frogs together had significantly higher abundances in the AES ditches compared to the control ditches. These results illustrate the potential role of agricultural ditches, combined with reserves and nature-friendly ditch bank management, in the conservation of amphibian populations.

What is the role of local landscape structure in the vegetation composition of field boundaries?

Abstract.Question: How distinct is the flora of field boundaries? How does the structure of field boundaries determine the composition of vegetation?Location: Estonia, six 4 km × 4 km agricultural areas.Methods: We studied the vegetation of fields and field boundaries using 2 m × 2 m sample plots. We estimated the frequency of species in both habitat types, applied an MRPP test to analyse the vegetation composition of field boundaries with various combinations of landscape features (ditches, roads, tree and bush layers) illustrating this by DCA ordination, and used indicator species analysis to determine the characteristic species of each boundary type.Results: Ca. 45% of the flora of field boundaries comprised species found on agricultural land. Most typical species in fields — agrotolerants — were also the most common in field boundaries. The vegetation of road verges and grassy boundaries consisted mainly of disturbance‐tolerant species. Woody boundaries were characterised by shade‐tolerant and nitrophilous species. Ditch banks included species typical of moist habitats and semi‐natural grasslands. Few threatened or protected species were observed.Conclusion: The vegetation composition of field boundaries varied due to the complex effects of landscape structure around and in these boundaries. Plant species in agricultural landscapes can be classified into two broad emergent groups on the basis of their different responses to agricultural disturbances — agrotolerant species and nature‐value species. Agrotolerant species are promoted by agriculture, nature‐value species include rare weeds and habitat specialists. We suggest that high‐nature‐value species should prevail in monitoring the effects of land‐use intensification on biodiversity rather than total species richness.

At what spatial scale do high‐quality habitats enhance the diversity of forbs and pollinators in intensively farmed landscapes?

Summary Over the last decades, biodiversity in agricultural landscapes has declined drastically. Initiatives to enhance biodiversity, such as agri‐environment schemes, often have little effect, especially in intensively farmed landscapes. The effectiveness of conservation management may be improved by scheme implementation near high‐quality habitats that can act as a source of species. We evaluated up to what distance high‐quality habitats (nature reserves and artificially created flower‐rich patches) affect the diversity of forbs and pollinators in intensively farmed landscapes of the Netherlands. We surveyed forbs, inflorescences, bees and hover flies and estimated pollination services in transects along ditch banks extending 300 m from four nature reserves forming small islands in landscapes dominated by agriculture. In a separate experiment, we surveyed inflorescences, bees and hover flies in 1500 m long transects on farmland adjacent to five newly introduced flower‐rich patches and in five control transects. Species density of forbs declined over the first 75 m and species density and abundance of hover flies declined over the first 125 m beyond the nature reserves. Beyond these distances, no further declines were observed. The effects of flower‐rich patches were spatially limited. The species density and abundance of bees and hover flies were significantly enhanced in the flower‐rich patch, but only the abundance of hover flies was enhanced up to 50 m beyond the patch. Synthesis and applications. In intensively farmed areas, remnant high‐quality habitats sustain more abundant and diverse pollinator and forb communities than the surrounding countryside. They do enhance biodiversity on nearby farmland but increases are spatially restricted (< 150 m) and relatively small. These habitats may therefore function only as dispersal sources for ecological restoration sites or agricultural fields under extensification schemes that are located in close proximity. Habitat restoration in intensively used farmland should therefore be implemented preferentially in the immediate vicinity of high‐quality habitats. In the short term, newly created flower‐rich habitats are no alternative to pre‐existing seminatural habitats for the promotion of pollinators on nearby farmland.