Habitats In Agricultural Landscapes Research Articles

Two-stage channels can enhance local biodiversity in agricultural landscapes

Field drainage causes habitat loss, alters natural flow regimes, and impairs water quality. Still, drainage ditches often are last remnants of aquatic and wetland habitats in agricultural landscapes and as such, can be important for local biodiversity. Two-stage channels are considered as a greener choice for conventional ditches, as they are constructed to mimic the structure of natural lowland streams providing a channel for drainage water and mechanisms to decrease diffuse loading. Two-stage channels could also benefit local biodiversity and ecosystem functions, but existing information on their ecological benefits is scarce and incomplete. We collected environmental and biological data from six agricultural stream systems in Finland each with consequent sections of a conventional ditch and a two-stage channel to study the potential of two-stage channels to enhance aquatic and riparian biodiversity and ecological functions. Biological data included samples of stream invertebrates, diatoms and plants and riparian beetles and plants. Overall, both section types were highly dominated by few core taxa for most of the studied organism groups. Riparian plant and invertebrate communities seemed to benefit from the two-stage channel structure with adjacent floodplains and drier ditch banks. In addition, two-stage channel sections had higher aquatic plant diversity, algal productivity, and decomposition rate, but lower stream invertebrate and diatom diversity. Two-stage channel construction did not diversify the structure of stream channels which is likely one explanation for the lack of positive effects on benthic diversity. However, both section types harbored unique taxa found only in one of the two types in all studied organism groups resulting in higher local gamma diversity. Thus, two-stage channels enhanced local biodiversity in agricultural landscapes. Improvements especially in aquatic biodiversity might be achieved by increasing the heterogeneity of in-stream habitat structure and with further efforts to decrease nutrient and sediment loads.

Seasonal and habitat dependence of plant species, functional and phylogenetic diversity in agricultural landscapes

The biodiversity of agricultural landscapes is under significant threat, while non-agricultural habitats within these landscapes play a crucial role in biodiversity conservation. There has been limited investigation into how plant species, functional and phylogenetic diversity varies across different seasons and habitats in agricultural landscapes. Thus, we carried out a survey of the plant communities in non-agricultural habitats in China's lower Yellow River plain. We investigated the diversity features of plant functionality, phylogeny, and plant species. We compared differences in plant community structure using non-metric multidimensional scaling analysis and tested phylogenetic signal using phylogenetic methods. Our analysis of plant community and diversity characteristics revealed significant differences in plant community structure between seasons and habitats, with the season having a more significant impact. The levels of plant species, functional, and phylogenetic diversity followed a seasonal pattern, with spring seeing the highest values and autumn seeing the lowest. Woodland and hedgerow habitats had the highest levels of diversity, while field roads had the lowest. The community phylogenetic structure of non-agricultural habitats was relatively concentrated and mainly influenced by human interference and environmental filtering. These findings offer scientific support for the preservation of ecosystem services and biodiversity in agricultural landscapes.

Agricultural landscape composition alters ant communities in maize fields more than plant diversity enrichment

Abstract. Pasaribu DN, Rizali A, Tarno H, Priawandiputra W, Johannis M, Buchori D. 2024. Agricultural landscape composition alters ant communities in maize fields more than plant diversity enrichment. Biodiversitas 25: 205-213. Fragmented natural habitats in human-modified landscapes play a crucial role in conserving biodiversity. Ants, as keystone species, are integral to terrestrial ecosystems, making it essential to comprehend the factors influencing their survival. This study investigates the impact of agricultural landscape composition and plant diversity enrichment (flowering plants) management on shaping ant communities in maize (Zea mays L.) fields. The research occurred in maize fields surrounded by other crops, semi-natural habitats, and housing areas in Malang District, East Java, Indonesia. The four agricultural areas were divided into control and treatment plots, considering landscape composition parameters, particularly Class Area (CA) and the Number of Patches (NP), measured within a 500 m radius. The landscape around the maize fields was characterized by manually digitizing land use. Six types of plant diversity enrichment were employed in this study: wild cosmos (Cosmos caudatus), white buttercup (Turnera subulata), sunflower (Helianthus annuus), long bean (Vigna unguiculata), ornamental bean (Arachis pintoi), and coral vine (Antigonon leptopus). The study was divided into the dry season (April-July 2022) and the wet season (September-December 2022). Ant sampling was conducted using pitfall traps and, based on generalized linear models, revealed that plant diversity enrichment management did not affect species richness, abundance, or composition of ants. Landscape composition positively influenced ant species richness but negatively impacted species composition, particularly the number of semi-natural habitat patches. Maize crop age also positively influenced ant species richness but negatively affected beta diversity. Wet season was also found to have a negative effect on beta diversity. In conclusion, the proportion of semi-natural habitats in agricultural landscapes and crop age contribute significantly to species richness and species composition of ants.

Documentation of Avian Species Composition and Assemblage in Agricultural Landscapes of Karnal, Haryana

Avian communities maintain ecological balance by  eliminating pests, providing ecosystem services, and  acting as biological indicators, thereby playing a pivotal  role in conserving agricultural landscapes’ integrity and  stability; thus from an environmental monitoring  standpoint, assessment of bird aggregations in various  landscapes is necessary. A three-year (2021, 2022 and  2023) bird survey was conducted to document the  checklist, density, and diversity of bird species  assemblage of agricultural landscapes in the Karnal  district of Haryana, India, to obtain the richness of birds  in different agricultural habitats. A total of 79 bird  species from 36 families and 14 orders were recorded;  two bird species (Alexandrine Parakeet and Black Headed Ibis) are listed as Near Threatened in the ‘IUCN’  (2010) category. Seventeen avian species with global  declining population trends are present in the study  area. The Passeriformes order, with 44 species, is the  most diverse in the study area. In all habitats, analysis of  food and feeding guilds, as well as perching activity,  revealed that the insectivorous guild (29) is dominant,  followed by Omnivore (25), Carnivore (11), Granivore  (7), Frugivore (5), and Nectarivore (2). The results of this  study indicate that, in order to enhance the quality of  bird habitat in agricultural landscapes, biodiversity friendly farming practices should be adopted. 

Hedgerows are more multifunctional in preserved bocage landscapes

Hedgerows are key wildlife habitats in agricultural landscapes, with presumably high multifunctionality – that is the capacity to provide multiple ecological, agronomic or cultural functions. However, knowledge gaps remain regarding the drivers of hedgerow multifunctionality and potential synergies and trade-offs between functions. In particular, it is unknown in which landscapes hedgerows best support a range of taxa and associated functions. We assessed the effects of hedgerow features, adjoining farming systems, landscape context, and their interactions on hedgerow multifunctionality based on four ecological functions – biodiversity conservation, potential pollination, potential predation, and pest colonization. We estimated these functions by the abundance and diversity of plant and arthropod taxa in 40 hedgerows, in Brittany (France). Results support previous studies showing the beneficial effects of flower cover, margin width, adjacent organic farming, and other variables related to hedgerow structural complexity on individual taxa or proxies of functions. Most importantly, our study reveals that hedgerows are more multifunctional in landscapes with dense hedgerow networks (so-called ‘bocage’ landscapes), which is likely the result of greater habitat amount, connectivity, and environmental heterogeneity. In addition, we find weak correlations between proxies of functions, and more synergies than trade-offs in response to the explanatory variables, indicating that there is considerable scope for improving the ecological value of hedgerows. We draw attention to the fact that ongoing destruction of hedgerow networks, including wide and structurally complex hedgerows, might lead to long-term or irretrievable loss of associated species and ecological functions, jeopardizing restoration and replanting efforts.

Contrasting effects of wooded and herbaceous semi-natural habitats on supporting wild bee diversity

The use of pesticides and the lack of resources caused by the simplification of landscapes are often cited as the main drivers of the loss of wild bees. Landscape complexity has been shown to interact with local pesticide use in studies of the effect of these factors on the abundance and diversity of insects. But, to date, few studies have simultaneously investigated local and landscape effects on wild bees using more precise descriptors of the landscape and of farming practices. The aim of the present study was thus to disentangle the effects of landscape composition and farming practices on the taxonomic and functional diversity of wild bees and their possible consequences for pollination potential. We analysed a dataset of 107 crops at whose edges wild bees were captured between 2013 and 2019. Pesticide treatments of each crop were recorded throughout the year. At the landscape level, the proportions of different types of land use were calculated in a circle with a radius of 500 m. We caught 1536 wild bees belonging to 86 species and, using generalized mixed modelling, found that the number of insecticide applications had a negative effect on wild bee abundance and richness, while forest cover within a 500-m radius had a positive effect on wild bees whatever the farming practices. However, we also showed that the effect of the proportion of permanent grasslands on taxonomic and functional diversity of wild bees differed depending on the use of fungicides in the field. Finally, we found a negative effect of the number of herbicide applications on pollination potential. This study advances our understanding of the contrasting but complementary roles of diverse semi-natural habitats in agricultural landscapes in supporting wild bee diversity and which, under certain conditions, may buffer the detrimental consequences of pesticide use.

Wild Floral Visitors Are More Important Than Honeybees as Pollinators of Avocado Crops

Wild insects provide pollination services in agroecosystems. Avocado is an economically important crop grown in the Chilean Mediterranean climate region and exported worldwide. Avocado pollination is managed using honeybee hives, while the role of wild insects as pollinators remains poorly known. We quantified the relative contributions of wild floral visitors and honeybees to the fruit set of avocados in two contrasting seasons (2015 and 2016) in Central Chile. Observations were made in 60 trees grown nearby (~300 m) to remnant patches of native sclerophyll vegetation. We found that honeybees and wild insects accounted for 48.6% and 51.4% of total floral visitation, respectively, with a 68% taxonomic similarity of floral visitors between seasons. The presence of honeybees significantly modulated the floral visitor composition and modified plant-pollination network parameters, which resulted in the biotic homogenization of the interaction network, through the increase of shared tree–floral visitor interactions, to the detriment of exclusive interactions. Finally, wild insects were more effective than honeybees in pollinating avocado trees and their contribution was greatest during the dry year. Thus, honeybees alone cannot be relied upon to deliver maximum pollination. We highlight ecological intensification practices to encourage wild insect visits and avoid native vegetation replacement with orchards. Therefore, we emphasize that future ecological intensification research should address agricultural practices to promote wild insects and evaluate the role of native vegetation as wild pollinator habitat in agricultural landscapes.

Improving and expanding hedgerows—Recommendations for a semi‐natural habitat in agricultural landscapes

Abstract Hedgerows provide habitat, shelter and resources for many species including functionally important taxa and threatened species. Hedgerows store carbon both above‐ and below‐ground and provide a range of other ecosystem services. Policies incentivizing increases in the extent and quality of hedgerows require evidence to determine how these increases may best support a wide range of taxa and to improve hedgerow habitat quality. Here, available evidence for increasing hedgerow extent and improving their quality is discussed in the context of current conservation policy. Moderate evidence supports a substantial increase in average hedgerow extent from 4.2 km/km2 to around 10 km/km2 in the United Kingdom, to optimize support for many wildlife taxa, habitat connectivity and carbon storage. Evidence also supports the development of wider and structurally denser hedges with more diverse structures and management approaches, and hedgerow networks that are well connected with each other and with other semi‐natural habitats. However, barriers may hinder the implementation of hedgerow policies, and there remain substantive gaps in the evidence base. Knowledge gaps include the current quality or condition of UK hedges, understanding in which landscape contexts new hedges would best be planted to support biodiversity, the role of hedgerows in connectivity as species' ranges change under a future climate, and whether an increase in hedgerow extent might increase the spread of invasive species, tree pests or diseases. These gaps must be filled if conservation policies, including future agri‐environment schemes, are to ensure that hedgerows reach their considerable potential in aiding nature's recovery and addressing climate change.

The effect of semi-natural habitat types on epigaeic arthropods: Isolate habitats make critical contribution to biodiversity in agricultural landscape

Semi-natural habitats in agricultural landscapes vary greatly in shape and vegetation characteristics. They can appear either as relatively large patches of several hectares or as narrow bands (less than 1 m wide) between fields and roads and between fields. Semi-natural habitats support biodiversity and associated ecosystem services on farmland, thereby contributing to sustainable agriculture.However, the effects of different semi-natural habitat types on the polytrophic level of epigaeic arthropods are still unclear. In this study, we classified semi-natural habitats into five types. (1) woody areal (WA), (2) woody line (WL), (3) herbaceous areal (HA), (4) herbaceous line (HL) and (5) isolate habitat (IH). We aimed to explore differences in epigaeic arthropod community composition in five different semi-natural habitats and the effects of different semi-natural habitats and different sampling locations on epigaeic arthropod activity-density and diversity. The results showed that epigaeic arthropod communities show significant differences, not only between farmland and semi-natural habitats, but also between different types of semi-natural habitats. Isolate habitats have the highest activity-density of epigaeic arthropods and Linear herbaceous maintain the highest epigaeic arthropod diversity. We also found in this study, both the activity-density and diversity of epigaeic arthropods showed edge-biased distribution. It may be possible to promote sustainable agricultural ecosystems by understanding the effect of semi-natural habitats on epigaeic arthropods, which is conducive to improving the quality of the agricultural ecological environment.

Monarch Butterfly Ecology, Behavior, and Vulnerabilities in North Central United States Agricultural Landscapes.

The North American monarch butterfly (Danaus plexippus) is a candidate species for listing under the Endangered Species Act. Multiple factors are associated with the decline in the eastern population, including the loss of breeding and foraging habitat and pesticide use. Establishing habitat in agricultural landscapes of the North Central region of the United States is critical to increasing reproduction during the summer. We integrated spatially explicit modeling with empirical movement ecology and pesticide toxicology studies to simulate population outcomes for different habitat establishment scenarios. Because of their mobility, we conclude that breeding monarchs in the North Central states should be resilient to pesticide use and habitat fragmentation. Consequently, we predict that adult monarch recruitment can be enhanced even if new habitat is established near pesticide-treated crop fields. Our research has improved the understanding of monarch population dynamics at the landscape scale by examining the interactions among monarch movement ecology, habitat fragmentation, and pesticide use.

Distance to semi‐natural habitats matters for arbuscular mycorrhizal fungi in wheat roots and wheat performance in a temperate agricultural landscape

Introduction The proximity of semi-natural habitats and agricultural fields in an agricultural landscape leads to unavoidable biological, chemical, and physical interactions. Fungi can negatively influence, but also support crop growth in agricultural fields. Therefore, in this field study we investigated the colonisation of arbuscular mycorrhizal (AM) fungi and non-AM fungi in winter-wheat roots as well as winter-wheat performance in distance to semi-natural habitats. Materials and Methods We sampled in an intensively managed agricultural landscape in North-east Germany along agricultural transition zones, that is, along 50 m-transects from semi-natural habitats like hedgerows and glacially created in-field ponds—so-called kettle holes—into agricultural fields. Results To our knowledge, we show for the first time that AM fungal colonisation in winter-wheat roots decreased linearly with increasing distance to semi-natural habitats while non-AM fungal root colonisation did not change. Winter-wheat grain yield and biomass slightly increased with increasing distance to hedgerows but not to kettle holes. This clearly shows that there is a difference between different crop performance parameters. Random forest machine learning algorithms confirmed the particular importance of distance to semi-natural habitats for AM fungal root colonisation and for winter-wheat grain yield. Less intensive agricultural management close to semi-natural habitats, for example, no herbicide and pesticide applications as a result of nature protection regulations, may partly explain this pattern. However, spatial response patterns of AM but not of non-AM fungi in wheat roots also point to changed ecological interactions close to semi-natural habitats. Conclusion Semi-natural and natural habitats in agricultural landscapes are slowly recognised not only to be important for biodiversity conservation, but also for sustainable crop production. Additionally, they may also be a tool for farmers and policy makers to improve sustainable landscape management. And agricultural transition zones are spatially and temporally complex dynamic ecosystems that should be the focus of further investigations.

Contribution of Agricultural Landscape Composition on Shaping the Interaction Between Pests and Natural Enemies in Cacao Agroforestry

Studies of the effects of landscape composition on pests and their natural enemies on agroforestry systems is still limited, whereas the system can maintain biodiversity. This research investigated the impact of agricultural landscape composition on shaping the interaction between pests and natural enemies in cacao agroforestry. The study was conducted in twelve cacao plantations spread across five districts in East Java, Indonesia. A sampling of insects was carried out by observing the intensity of pest attacks and the diversity and abundance of predators. The surrounding landscape of the cacao field was characterized by manually digitalizing the land use. The results found two main pests attacking all cacao plantations: cacao pod borer, Conophomorpha cramerella (CPB) with attack intensity 0.72-12.05%, and Helopeltis sp. with attack intensity 12.39-42.24%. Management of cacao plantations, such as intensification and canopy cover, significantly affected the attack intensity of CPB but not Helopeltis sp. Based on the generalized linear model, the landscape composition, especially the patch number of natural habitats, positively impacted CPB attack intensity and predator abundance. However, predator abundance harmed CPB attack intensity. In conclusion, the proportion of natural habitat in agricultural landscapes contributes to reducing the attack intensity of pests via maintaining natural enemy abundance.

Simple and farmer-friendly bumblebee conservation: Straw bales as nest sites in agricultural landscapes

Many bumblebee species are declining due to a loss of semi-natural habitats in agricultural landscapes resulting in diminished forage and nest sites. Anecdotal experience indicates that bumblebees nest in straw bales, but scientific evidence is lacking. We spent 250 h screening for bumblebee nests in 1255 straw bales and ten straw stacks belonging to 58 farms in two intensively farmed Swedish regions and recorded nests, nest traffic, and straw characteristics. We supplemented the straw screening with screening of control areas, without straw, that were selected in similar environments as the areas with straw. We observed 45 bumblebee nests (including potential nests where a single bumblebee flew in or out of the straw) of eight species/species groups, including one red-listed, in or directly adjacent to the straw at 26 of the farms. Nests were mainly found in partly decayed straw and bales placed together. We found no nests in control areas. Based on our results, we suggest that straw can be used as an easy, cheap and efficient intervention to increase the availability of bumblebee nest sites in agricultural landscapes. Considering the costs and benefits of the alternatives, we conclude that straw addition has advantages over commercial bumblebee colonies for crop pollination purposes and over artificial nest boxes for conservation purposes.

[Effects of landscape complexity and local management on bee pollinator diversity in apple orchards in Changping District, Beijing, China.]

Pollinators provide important ecosystem services for crop production and food security. With the development of agricultural economy and the increasing intensity of land-use, a large number of natural or semi-natural habitats have been converted to croplands. Landscape homogenization and intensive management lead to the decline of wild bee diversity and threaten the sustainable agricultural production. In this study, we investigated the effects of landscape complexity (proportion of semi-natural habitats), local management practices (local flowering plant diversity and soil total nitrogen), and their interactions on diversity of bee pollinators in apple orchard in Changping District, Beijing. A total of 8642 bee individuals were captured, including 5125 honey bees and 3517 wild bees from 5 families, 14 genera, and 49 species. The optimal landscape scale for the response of bee diversity to landscape complexity and local management intensity was 500 m. Within 500 m radius of the site, the abundance of overall bees and wild bees significantly increased with increasing proportion of semi-natural habitats. The landscape complexity interacting with local flowering plant diversity significantly affected the richness of overall bee and wild bee. When the proportion of semi-natural habitats surrounding the apple orchards was low (≤29.9%), we found a positive effect of flowering plant diversity on the richness of overall bee and wild bee, whereas a reversed trend was found when the proportion of semi-natural habitats surrounding the apple orchards was high (>29.9%). In addition, the abundance of honey bees significantly increased with the increase of local flowering plant diversity and soil total nitrogen. The soil total nitrogen interacting with local flowering plant diversity significantly affected the honey bee abundance. At low levels of soil total nitrogen (≤1.9 g·kg-1), there was a positive effect of flowering plant diversity on honey bee abundance; whereas this trend was reversed at high levels of soil total nitrogen (>1.9 g·kg-1). Increasing the proportion of semi-natural habitats in agricultural landscape was beneficial to the increase of wild bee abundance, and flowering plant diversity could promote bee diversity but depending on landscape scale (proportion of semi-natural habitats) and local scale (nitrogen application). Therefore, multi-scale factors should be considered to develop conservation strategies to maintain the diversity of wild bees in agricultural landscape. Maintaining a higher proportion of cultivated land as much as possible is still a long-term requirement for production, while maintaining intermediate landscape complexity, increasing the diversity of flowering plants on the ground, and reducing the application of nitrogen fertilizer would be effective ways to promote the diversity of pollinating bees in apple orchards.

Pollinator enhancement in agriculture: comparing sown flower strips, hedges and sown hedge herb layers in apple orchards

In intensive agricultural landscapes semi-natural habitats for pollinators are often limited, although willingness to establish pollinator habitat is increasing among farmers. A common pollinator enhancement measure is to provide flower strips, but existent or improved hedgerows might be more effective. In this study, we compare the effectiveness of three pollinator enhancement measures at edges of conventional apple orchards: (i) perennial flower strips, (ii) existent hedgerows, and (iii) existent hedgerows complemented with a sown herb layer. We used orchard edges without any enhancement as control. The study took place over three consecutive years in Southern Germany. Wild bee abundance and species richness were highest in flower strips followed by improved hedges. Hoverflies were also most abundant in flower strips, but not more species rich than at control sites. Wild bee but not hoverfly community composition differed between control and enhancement sites. The overall pollinator community included only few threatened or specialized species. Flower abundance was the main driver for wild bee diversity, whereas hoverflies were largely unaffected by floral resources. Pollinator enhancement had neither an effect on the abundance or species richness within the orchards nor on apple flower visitation. Perennial flower strips seem most effective to enhance wild bees in intensive agricultural landscapes. Additionally, flower-rich hedgerows should be promoted to complement flower strips by extending the flowering period and to increase connectivity of pollinator habitat in agricultural landscapes.

Functional composition of ant assemblages in habitat islands is driven by habitat factors and landscape composition

Fragmented natural habitats within human-transformed landscapes play a key role in preserving biodiversity. Ants as keystone species are essential elements of terrestrial ecosystems; thus, it is important to understand the factors influencing their presence. In a large-scale multi-site study, we surveyed ant assemblages using sweep netting and D-vac sampling on 158 ancient burial mounds preserving grassland habitats in agricultural landscapes in East-Hungary. We asked the following questions: (1) How do habitat factors and landscape composition affect species richness and functional diversity of ants? (2) Which ant traits are affected by habitat factors and landscape composition? Despite their small sizes, mounds as permanent and relatively undisturbed landscape elements could provide safe havens for diverse ant assemblages even in transformed agricultural landscapes. The complex habitat structure of wooded mounds supported high species and functional diversity of ant assemblages. Ant species on wooded mounds had small or medium-sized colonies, enabling the co-existence of more species. The effect of landscape composition on ant assemblages was mediated by habitat factors: steep slopes buffered the negative effect of the cropland matrix and enabled higher ant diversity.

Influence of habitat quality and resource density on breeding‐season female monarch butterfly Danaus plexippus movement and space use in north‐central USA agroecosystem landscapes

Abstract The eastern North American monarch butterfly is at risk of quasi‐extinction due, in part, to the loss of breeding habitat in agricultural landscapes of the USA Midwest. Because adult females are not patch residents, egg abundance and distribution across the landscape are a function of their perceptual range, flight directionality and flight step lengths. Conservation actions that account for habitat use in agricultural landscapes can enhance functional connectivity. Field‐captured females (n = 114) were released in a 64‐ha area containing restored prairies, grass‐dominated fields and crop fields in Floyd County, Iowa, USA, and two 1,000 m linear north–south sections of grass‐dominated roadside along secondary roads (~35 ha) with different proximity to prairie habitat in rural Story County, Iowa. Radio‐tagged or untagged monarchs were released in areas with high density, low density and zero density of forage and oviposition resources, as well as on habitat edges between high‐ and zero‐density habitats. Monarchs were observed for 1 hr. Radio‐tagged individuals that flew beyond visual detection were relocated using handheld radiotelemetry. Monarchs moved within and between habitat classes and typically performed upwind search behaviour. Monarchs successfully located resources, with some flying over 500 m to find high‐density areas, providing evidence that the monarch's perceptual distance is >100 m. Regardless of habitat class or field site, most step lengths were <50 m, and turn angles were directional. Large steps (≥50 m) crossing habitat boundaries occurred with approximately half of the monarchs, which may indicate initiation of long‐range searches for suitable habitat, consistent with their vagile behaviour. Establishing habitat patches 50 m apart in agricultural landscapes would facilitate efficient movement. Synthesis and applications. This study provides an extensive dataset of directly observed breeding‐season monarch butterflies to assess the utilization of agricultural landscapes. Documentation of step lengths >50 m in complex, agricultural landscapes would not have been possible without the aid of radiotelemetry. Results provide improved estimates of perceptual range and flight patterns within and between habitat patches that support models that simulate natural population dynamics to enable conservation planning at a landscape scale.

Taxon- and functional group-specific responses of ground beetles and spiders to landscape complexity and management intensity in apple orchards of the North China Plain

Agricultural intensification has caused severe declines in ground-dwelling arthropods and associated ecosystem services. The conservation and re-establishment of semi-natural habitats in agricultural landscapes represent widely accepted measures to counter these declines. The effectiveness of these measures nonetheless varies between target taxa and their functional traits, while also being affected by local management. Here, we studied how species richness and abundance of different functional groups of carabid beetles and spiders in apple orchards were affected by landscape complexity (% semi-natural habitat) and local management intensity (mowing and soil total nitrogen (STN) content). Both abundance and species richness of non-carnivorous carabids and carabids overall were negatively affected by STN, while the abundance of carnivorous carabids and carabids overall was affected by interactive effects of mowing and landscape complexity, showing a positive response to mowing where semi-natural habitats are scarce, but negative responses in landscapes with a higher proportion of semi-natural habitats. The abundance of ground-hunting spiders and spiders overall was generally positively related to % semi-natural habitats, while the abundance of web-building spiders and the species richness of ground-hunting spiders showed a positive correlation with STN at landscapes with a low or medium abundance of semi-natural habitats, but a negative correlation where semi-natural habitats were more abundant. Non-carnivorous carabid diversity benefitted from low nitrogen application, while carnivorous carabid abundance benefitted from mowing intensity especially in simple and structurally homogenous agricultural landscapes. Both web-building and ground-hunting spiders positively responded to low nitrogen applications and intermediate landscape complexity. Overall, a low local management intensity promoted carabid beetles, while spiders were favored by increasing landscape complexity. We conclude that taxon- and functional group-specific, multi-scale conservation strategies are therefore required to conserve invertebrate predators in apple orchards.

Differential responses in spider oviposition on crop-edge gradients in agroecosystems with different management

Semi-natural habitats in agricultural landscapes offer reproduction and feeding sites for natural predators of pests. Spiders are among the most abundant and diverse generalist predators and can efficiently suppress pest populations in agroecosystems. However, despite the importance of these habitats, there is a significant gap of knowledge on oviposition sites of spiders in agroecosystems. Our main goal was to investigate if semi-natural habitats play an important role in spider oviposition in two crops with different agricultural managements. Our specific objectives were to estimate where spider oviposition is highest (in semi-natural habitats or in crops); if there are different responses between crops (alfalfa and soybeans); and to measure trap-nests efficiency as shelter and breeding places for vegetation-dwelling spiders. We used trap-nest technique, a novel method to collect spiders and their eggsacs. We carried out the study in 15 sites in soybean and 10 sites in alfalfa crops in order to sample spiders’ eggsacs and shelters. Each sampled site consisted of a semi-natural habitat (enclosures or edges) and its adjacent crop. We found that the number of eggsacs decreased from semi-natural habitats towards the interior of the soybean crop and the opposite pattern in alfalfa, where the number of eggsacs significantly increased within the crop. Our results provide evidence that spider reproduction takes place outside the crops, albeit only in soybean crops. Our findings were different in alfalfa with minimum use of agrochemicals and with a lesser seasonal disturbance, with a higher spider oviposition compared to semi-natural habitats. In addition, our results have several important implications for the management of agroecosystems. We consider that the use of these trap-nests is a suitable and a reliable tool to study vegetation-dwelling spiders in different ecosystems.

Assessing the Role of Kettle Holes for Providing and Connecting Amphibian Habitats in Agricultural Landscapes

The intensification of agriculture over the last few decades has caused habitat loss, which poses a significant threat to the survival of populations and species. Where habitats are connected, populations may escape the destruction of their habitat by migrating to another one. Consequently, the functional connectivity of landscapes has become an important focus for species conservation. Kettle holes are hotspots of biodiversity that provide suitable conditions for wildlife species (i.e., amphibians, insects, aquatic plants) and contribute to landscape heterogeneity. They are also considered to function as stepping stone habitats that contribute to habitat connectivity. This study assesses the contribution of kettle holes for (i) habitat provision and (ii) the functional connectivity of three amphibian species with different movement ranges, and (iii) the study identifies areas where the creation of stepping stone biotopes could improve functional connectivity. The contribution of kettle holes was assessed using GIS-based clustering within three research areas in Germany. It was found that the importance of kettle holes for providing amphibian habitats in the three studied areas was equal to or higher than that of other wetland habitats. The state of functional connectivity and the contribution of kettle holes differed strongly depending on the species’ range. For the short-range species, landscapes were highly fragmented, and the contribution of kettle holes was much smaller than that of corridor habitats. For the long-range species, all habitats suited for amphibian reproduction were connected, and the contribution of kettle holes was similar to that of corridor habitats. However, the contribution of both was mostly redundant. Overall, the results showed that kettle holes play a crucial role in habitat provision and function as important stepping stone biotopes in agricultural landscapes. The clustering method applied in this study provides a simple tool for landscape planning and environmental protection agencies, which can be easily adapted to analyze functional connectivity and habitat interactions for different species or landscapes.