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.     

Predation of annual grass weed seeds in arable field margins

Seeds of three species of annual grass weeds (Alopecurus myosuroides, Avena fatua and Bromus sterilis) were placed in field margins around arable fields in a randomised block split-plot design experiment. The field margin vegetation was either sown or naturally regenerated and either cut or uncut. The seeds were either placed in cages designed to exclude small mammals and birds or were uncaged. The proportion of seeds removed was monitored on 10 occasions and mean seed loss was analysed. In general, a greater proportion of weed seeds was removed from uncaged trays in uncut swards, suggesting predation by small mammals, which inhabit tall grass. This effect was mainly due to removal of seeds of the two large-seeded species (A. fatua and B. sterilis), with A. fatua being especially favoured. It is therefore likely that small mammals play a role in the population dynamics of major crop weeds by feeding on their seeds in field margins, especially when these are dense and uncut.     

Swiss people's attitudes towards field margins for biodiversity conservation

Arable land in Switzerland harbours low biodiversity and lacks permanent species-rich structures. To remedy this situation, improved field margins (IFMs) will be introduced as a new ecological compensation type in the Swiss Lowlands. IFMs are extensively managed, sown species- and flower-rich vegetation strips which provide both habitats for a wide range of species and valuable structures for the ecological network. However, the success of ecological compensation measures depends strongly on their acceptance by farmers and the general public. In summer 2004, we investigated in a case study the attitudes of 108 Swiss people to IFMs directly in the field. Study participants were asked to rate the attractiveness of IFMs of different species richness and composition that were presented to them, to explain their rating and to estimate the number of species present. In addition, they were asked to imagine a field margin of their particular liking, to describe it, and to state their opinion on several aspects of IFMs. Study participants responded very positively to species-rich vegetation. The more species-rich an IFM was perceived to be, the more it appealed to them. Species richness and general diversity were named as the main reasons for a positive rating. Study participants strongly approved the establishment of improved field margins. The positive rating and high acceptance of IFMs in this study indicate that they may be a successful new tool for biodiversity enhancement in intensively used agricultural landscapes.     

Spatial aggregation facilitates coexistence and diversity of wild plant species in field margins

European agri-environment schemes encourage farmers to establish sown field margin strips to protect and enhance wild plant diversity. However, plant diversity in such wild plant sowings based on seed mixtures is often low due to the high competitiveness of few, common species. Here we analysed whether intraspecific aggregation could enhance the performance of less competitive species, and how plant performance is influenced by the number of species in a mixture. We focused on inter- and intraspecific competition between six agricultural wild plant species (Centaurea cyanus, Calendula arvensis, Melilotus officinalis, Poa annua, Bromus mollis, Medicago lupulina), and tested (i) two different seeding patterns (intraspecifically aggregated vs. randomly dispersed) and (ii) three different species mixtures (monocultures, three-species, and six-species mixtures). Plant performance was measured in terms of number of individuals, biomass per individual, and biomass per m². Intraspecific aggregation resulted in higher numbers of individuals of all species, while mixtures generated lower numbers of individuals. The performance of plant species differed depending on their position in the competitive hierarchy. Competitively weak species suffered much less from intraspecific than interspecific competition in terms of biomass, and the competitively weakest species became even excluded in the most species rich and randomly dispersed sowings with high interspecific competition. In conclusion, the performance of wild plant species was influenced by both seeding pattern and number of species in a mixture. Intraspecific aggregation enabled the coexistence of competitively weak species by reducing interspecific competitive exclusion processes. Consequently, agri-environmental schemes designed to preserve and enhance biodiversity should consider small-scale processes influencing the distribution and abundance of plants, and develop new agricultural sowing technologies to cultivate competitively weak and endangered wild plant species.     

Agroecological transition increases arthropod diversity and decreases herbivore abundance on field margins

1. In peri-urban areas, many farmers are transitioning from conventional agriculture to agroecological practices to reduce pesticide input and preserving ecosystem services such as natural pest control. Field margins represent a stable habitat for arthropods, but community structure depends on many factors, including management type and vegetation features.
2. We studied the effects of agroecological transitions and vegetation features on arthropods of horticultural field margins, focusing on three feeding guilds (herbivores, predators and parasitoids). We sampled arthropods using the beat-sheet method in five conventional fields and five under agroecological transition. We also measured vegetation height, richness, flower abundance and plant cover.
3. Our results showed that arthropod diversity was higher in agroecological fields whereas herbivore abundance was lower, with a consistent pattern across most taxonomic orders. Vegetation features displayed multiple effects among functional and taxonomic groups. Herbivores did not respond to most vegetation variables whereas predators correlated with several, with similar trends among orders.
4. We conclude that agroecological transitions and field margins with high vegetation richness and floral resources influence arthropod communities with potential benefits regarding pest regulation. These practices might be more effective if considered alongside other methods that enhance biodiversity and if they are consistent at a landscape scale.

     

The optimal age of sown field margins for breeding farmland birds

The Europe‐wide decline in the populations and diversity of farmland birds has not been stopped despite dedicated conservation efforts such as agri‐environment schemes (AES). The main reason for the lack of success of AES is considered to be their low ecological quality and insufficient area. Understanding the effects of different management strategies on the ecological quality of AES is therefore important. Here, we investigate the relationship between breeding bird density and species richness and the age of sown field margins, a widely used type of AES, in southwestern Switzerland. Territories of breeding birds were mapped on 67 field margins between 2004 and 2011. Territory densities (for eight species) and species richness were analysed in relation to age of the field margin. A general negative correlation between size of the field margin and territory density indicated that territory density was higher when the birds could forage in adjacent cultivated land. Territory densities and species richness increased up to an age of 4–6 years after sowing, depending on the species, and declined thereafter. The results suggest that the co‐occurrence of newly sown margins and margins over 3 years old will have a positive effect on breeding bird densities and species diversity.     

Agri-environment schemes and butterflies: the utilisation of two metre arable field margins

The utilisation of two metre field margins by butterflies was studied at three farms in Essex, south east England between 1997 and 2000. The aim of the study was to establish whether field margins, as set up and managed under Countryside Stewardship Scheme guidelines, were beneficial to common farmland butterflies. Thirteen two metre margins (total length 4478 m) and three sections with no margin (total length 656 m) were monitored over the 4 year period using the transect method. Significantly more Maniola jurtina, Thymelicus sylvestris and Thymelicus lineola were seen on the two metre margins than on the control sections, but there was a significant reduction in abundance of Thymelicus sylvestris, Thymelicus lineola and Ochlodes venata on the margins over the 4 year study period. Only the abundance of Pyronia tithonus increased significantly on the two metre margins over that period.     

Occurrence of an herbicide‐resistant plant trait in agricultural field margins

Agricultural environments allow study of evolutionary change in plants. An example of evolution within agroecological systems is the selection for resistance to the herbicide glyphosate within the weed, Conyza canadensis. Changes in survivorship and reproduction associated with the development of glyphosate resistance (GR) may impact fitness and influence the frequency of occurrence of the GR trait. We hypothesized that site characteristics and history would affect the occurrence of GR C. canadensis in field margins. We surveyed GR occurrence in field margins and asked whether there were correlations between GR occurrence and location, crop rotation, GR crop trait rotation, crop type, use of tillage, and the diversity of herbicides used. In a field experiment, we hypothesized that there would be no difference in fitness between GR and glyphosate‐susceptible (GS) plants. We asked whether there were differences in survivorship, phenology, reproduction, and herbivory between 2 GR and 2 GS populations of C. canadensis in agrestal and ruderal habitats. We found that geographic location was an important factor in the occurrence of GR C. canadensis in field margins. Although not consistently associated with either glyphosate resistance or glyphosate susceptibility, there were differences in phenology, survivorship, and herbivory among biotypes of C. canadensis. We found equal or greater fitness in GR biotypes, compared to GS biotypes, and GR plants were present in field margins. Field margins or ruderal habitats may provide refugia for GR C. canadensis, allowing reproduction and further selection to occur as seeds recolonize the agrestal habitat. Agricultural practices may select for ecological changes that feed back into the evolution of plants in ruderal habitats.     

Invertebrates in field margins: taxonomic group diversity and functional group abundance in relation to age

Sown, temporary field margins are a common agri-environment scheme (AES) in the Netherlands. Despite their wide application, though, there has been scarcely any long-term monitoring of the succession of invertebrates. In the field margins of 40 farms, invertebrate diversity and the abundance of three functional groups were assessed in relation to age. The diversity in terms of number of species groups was found to increase with the age of the margins. The abundance of herbivores and detritivores also showed a positive correlation with the age of the margins. However, the abundance of predators decreased with increasing age. Older margins showed a higher total vegetation cover and fewer plant species, also resulting in lower plant species evenness. We suggest several changes to the current AES regulations. For the conservation of invertebrate diversity, longer-lasting field margins are desirable. In addition, old margins are favoured by detritivores, a group that has particular difficulty finding suitable habitats in agricultural landscapes. However, such margins are less favourable from an agricultural perspective, as they appear unsuitable for high abundances of potentially useful predators and the high vegetation cover attracts many potentially harmful herbivores. To circumvent this, the AES might be extended by incorporating hay-making, which would reduce standing biomass and might lead to more predators and fewer herbivores.     

The effect of field margins on the yield of sugar beet and cereal crops

The effect of field margins on the yield of sugar beet, wheat and barley was studied on commercial farms and in a series of field experiments from 1992–1997. There was always a trend of increasing yield from the edge of the field to the centre, with a marked reduction around the ‘tramlines’ and the area where machinery turns. In the studies on commercial farms, headland yield loss varied widely. In sugar beet the headlands yielded 19–41% less than the centre, with a mean reduction of 26%. In cereals the range was 3–19%, with a mean loss of 7%. Headland yield reductions were generally smaller in the field experiments than those found on commercial farms. These headland effects did not move towards the centre of the field when grass margins were planted at the edge of the field; there was no significant effect on the yield of the adjacent crop. The presence of boundary trees had the greatest effect on yield: in the outer 9 m of the field, the area shaded by trees produced 4.4 t ha^-1 of wheat, and the area that was not shaded 8.1 t ha^-1. Turning of machinery also significantly reduced yield, while grazing by rabbits and hares surprisingly had no effect. Following the reform of the Common Agricultural Policy in 1992, the main effect of which was to change from a price support policy to direct payments to producers, farmers in the European Union who produce more than a specified tonnage of ‘eligible crops’ per year, are required to fallow a given percentage of their land (currently 5%), to qualify for Arable Area Payments. Growers can elect to fallow fields on a rotational basis, or permanently. Headland set-aside is a term used to describe strips of set-aside, a minimum of 20 m wide around the edges of fields. In these experiments, the headland effect did not extend beyond 20 m from the field edge. Therefore, particularly in fields with boundary hedges or trees, headland set-aside could effectively remove the poor-yielding area at the field margin.     

有机稻田埂植物上节肢动物多样性

对稻鸭共作有机稻和常规稻田埂杂草、大豆和芝麻上的节肢动物群落进行了全季节系统调查,共采集2纲、12目、76科、172种,其中天敌103种(包括33种蜘蛛,6种捕食性昆虫和64种寄生性昆虫)、植食性昆虫64种.结果表明,蜘蛛和天敌昆虫丰富度以有机稻田埂最大,其蜘蛛物种数和个体数是常规田埂的4.5倍以上,天敌昆虫物种数和个体数是常规田埂的1.5倍以上.比较田埂植物上昆虫多样性表明,在有机稻田,大豆和杂草田埂上的昆虫物种丰富度最大(71),其次是芝麻(62),而杂草上的Shannon多样性指数最大;在常规稻田,大豆田埂上昆虫丰富度(52)和Shannon多样性指数最大,杂草上的昆虫Shannon多样性指数最小.有机田埂杂草上蜘蛛和飞虱发生动态有明显的跟随现象,由于喷施杀虫剂防治飞虱,常规田埂杂草上的蜘蛛和飞虱数量都处于较低水平,且没有明显的跟随现象.调查结果说明,有机稻田比常规稻田更有利于天敌的保护,在常规管理模式下田埂种植大豆和芝麻对稻田节肢动物群落保护具有积极作用.     

The quality of flower-based ecosystem services in field margins and road verges from human and insect pollinator perspectives

We contrasted traditionally used indicators of service provision quality, such as overall species richness and growth form composition, to three more specific functional properties: functional diversity, functional intensity, and functional stability. We defined flower colour as a functional trait perceived differently by humans and insect pollinators, and used user specific colour richness, flower size, and species richness within colour group as indicators of these three properties. We asked (1) do field margins and road verges provide flower-based ecosystem services with the quality of permanent grasslands; and (2) do traditional and detailed functional indicators of service provision quality agree on the service quality ranking of habitats?In an agricultural landscape of central and south-eastern Estonia (115 ÿ 95 km area, centroid 26°49⿲43⿳ and 58°54⿲49⿳) we sampled 87 field margins and 111 road verges as linear grassland-substitution habitats, and 84 permanent grasslands to scale their service quality.Linear habitats generally provided service of lower quality than permanent grasslands, but detailed indicators showed less evident contrast among habitat types than the overall species richness and stronger contrast than the proportion of forbs. Detailed indices, however, had strong seasonal dynamics to take into account. Vegetation in the first year field margins had greater colour richness (functional diversity) and species richness within colour groups (functional stability), but the smallest flower size (functional intensity), in contrast to road verges. By the third year of succession, field margins had become more similar to road verges. Indication of service provision quality differed between humans and pollinators, but their estimates were correlated across habitats.We showed that (1) combinations of specific service quality indicators provide more adequate information than generalized richness or growth form system, and (2) single grassland surrogate habitat type is an insufficient service providing substitute for permanent grasslands, although a mosaic of these habitats might be more efficient. Therefore, remnant fragments of semi-natural grasslands should receive top priority attention for conservation and restoration, particularly in agriculture dominated landscapes.     

Contrasting trends of butterfly species preferring semi-natural grasslands,field margins and forest edges in northern Europe

Indicator classifications help us to focus on the most relevant groups of species in monitoring the effects of land use changes on biodiversity. We studied changes in distribution area of 74 butterfly species preferring one of the three common habitats of boreal agricultural landscapes: semi-natural grasslands (35 species), arable field margins (7) and forest edges (32). Using extensive atlas data from four time periods during the last 50 years in Finland, we quantified trends in the occupancy of the species in 10 km grid squares, and classified them into four classes: declining (23), stable (17), increasing (27) and fluctuating (7) species. Trends among the species favouring three habitats were different: 60% of the species of semi-natural grasslands had declined, whereas 86% of the species typical of open field margins had increased. An increase also predominated in species associated with forest edges. Declining and increasing species differed in three ecological characteristics: increasing species were more mobile, utilized a wider range of habitats and, based on their larval host plants, lived in more eutrophic habitats than declining species. Species overwintering as adults showed more positive trends in occupancy than species overwintering as eggs, larvae or pupae. Observed trends in occupancy are in good agreement with long-term changes in land use and habitat availability in Finland: a long-continued decrease in the area of semi-natural grasslands and an increased amount of open forest edges and clearings due to modern forestry during the past 50 years.     

Reduced pesticide inputs on cereal field margins: the effects on butterfly abundance

Abstract. 1. On a study farm in Hampshire where large blocks of cereal fields had the pesticide inputs on their headlands experimentally and selectively reduced (the practice known as 'conservation headlands'), numbers of butterflies were monitored over 4 years by using transect counts.
2. Consistently more butterflies were seen flying over field edges sprayed under the conservation headland regime compared to those that were fully sprayed.
3. A comparison of changes in butterfly abundance on the study farm containing conservation headlands with data from the National Butterfly Monitoring Scheme indicated that population increases in some species may result from the use of conservation headlands.
4. The implications of resource provisioning and the potential reduction of spray drift into field-margin habitats are discussed in relation to farmland butterflies.     

Biodiversity and seasonal variation of the cyanobacterial assemblage in a rice paddy field in Fujian, China

Cyanobacteria are one of the main components of the microbiota in rice paddy fields and significantly contribute to its fertilization. The diversity and changes of the cyanobacterial assemblage were investigated during a rice growth season and after harvest in a paddy field located in Fujian Province, China. The cyanobacterial populations were analyzed by a semi-nested PCR, followed by denaturing gradient gel electrophoresis analysis. Twenty-four phylotypes were identified from the denaturing gradient gel electrophoresis profiles. The number of cyanobacterial phylotypes showed a seasonal variation and reached a peak in September, both in the upper (0-5 cm) and the deeper (10-15 cm) soil fractions. Some cyanobacterial sequences were only present during the rice growth season, while others were only found after harvest.     

Manipulating field margins to increase predation intensity in fields of winter wheat (Triticum aestivum)

The effectiveness of natural enemies to control pests can be enhanced through habitat manipulation. However, due to the differences in their ecology, generalist and specialist species may respond differently to the same manipulation. Moreover, interactions among natural enemies (i.e. cannibalism, intraguild predation, hyperparasitism) may complicate the assumption that a higher density of natural enemies would increase the level of biological control. We investigated the natural enemy guild composition and the predation rate along flower vs. grass margins at the edge of winter wheat (Triticum aestivum) fields in Denmark. Natural enemies were sampled by pitfall trapping and by suction sampling; predation intensity was measured using two different sentinel prey methods: artificial caterpillars made of plasticine, and sentinel aphid colonies. Specialist and generalist species responded differently to the two margin types: specialists (mostly parasitic wasps) were attracted by the flower margins, while generalists (ground beetles, rove beetles and spiders) were more active in grass margins. The number of artificial caterpillars attacked was significantly greater in grass margins (mean = 48.9%, SD = 24.3) than in flower margins (mean = 30.7%, SD = 17.4). We found a significant positive relationship between the number of artificial caterpillars attacked by chewing insects, and activity density for large (≥15 mm) ground beetles. Predation of sentinel aphids in wheat fields did not vary significantly in relation to margin type. Our results suggest that flowering margins may be beneficial for canopy‐active specialist natural enemies, but grassy margins are more useful for ground‐active generalist predators.     

Effects of management and structural connectivity on the plant communities of organic vegetable field margins in South Korea

Field margins are an important component of the agri-environment as they contribute to maintaining ecosystem functions and protecting biodiversity. Field margin structure, landscape attributes, and management practices have been examined as determinants of plant species diversity and composition for mainly cereal field margins; however, relatively little is known about their influence on vegetable field margins. We selected three types of field margins (each n = 4; non-managed connected to forests, non-managed isolated, and isolated and managed margins with mowing and organic herbicide) adjacent to organic vegetable crop fields and recorded the species richness and abundance of all vascular plants. The effects of structural connectivity, weed control management, and margin width on the community composition, species richness, and diversity were examined using multivariate statistical techniques. Plant community composition was clearly explained by structural connectivity between field margin and forest, as well as by weed control management. In contrast, species richness of functional guilds was influenced by connectivity and margin width, but not by weed control management. All communities had similar numbers of summer and fall blooming nectar- and pollen-producing plants, an important source of pollination services. In addition, each community of field margin types, despite different species composition, had similar levels of Shannon diversity and evenness. Our results suggest that habitat arrangement is important for determining community composition in field margins. Management practices may be important in determining dominance patterns of individual species. A combination of various margin types and widths may be beneficial for biodiversity conservation and ecosystem services.