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Frequent extreme weather events, which jeopardize agriculture by affecting crop health, characterize the ongoing climate change. Temporary patches where sown plants are poorly developed (hereafter “field defects”) are likely to increase with climate change and can be colonized by other plant species. Although perennial non-crop habitats can act as refuges for beneficial insects in agricultural landscapes and increase ecosystem services (ESs) in neighbouring arable fields, the relevance of field defects is unknown. Here, we quantified two ESs (pest and weed seed predation) in field defects within oilseed rape crops and related the ES levels with the activity-density of ground beetles and temperature. In 10 fields, we used artificial caterpillars made of plasticine and seed cards of two weed species (Taraxacum sp. and Stellaria sp.) to quantify the ESs in two sampling periods (spring and summer) and three habitat types: field defects, crops grown in standard conditions (field interiors) and crop-defect boundaries. Ground beetles were sampled using pitfall traps and classified into feeding guilds and body-size classes. Insects and mammals were the main pest predators, and predation increased in summer but did not differ among habitats. Seed predation rates for both species were significantly higher in summer. Predation upon Taraxacum seeds was higher in the field interiors, whereas the predation rate upon Stellaria seeds was significantly higher in the field interiors and defects compared to that in the crop-defect boundaries. The predation rate by insects increased with the activity-density of the medium- and large-sized carnivorous carabids, whereas the seed predation rate for both weed species was positively related to the activity-density of medium-sized herbivorous carabids. Finally, the mean and maximum temperatures were negatively linked to the predation rates on artificial caterpillars and seeds of Taraxacum, respectively. Our results suggest that these ephemeral habitats are not related to a strong decrease in ecosystem services; thus, field defects may not cause substantial changes in ES provisioning. We confirmed that ground beetles are important providers of both investigated ESs and showed that microclimatic conditions might play an important role in the regulation of ESs in agroecosystems. Grant Agency of the Czech Republic (18-26542S); Faculty of Environmental Sciences, Czech University of Life Sciences Prague (IGA) (42110/1312/3118) info:eu-repo/semantics/publishedVersion

Urbanization is one of the most important global trends which causes habitat reduction and alteration which are, in turn, the main reasons for the well-documented reduction in structural and functional diversity in urbanized environments. In contrast, effects on ecological mechanisms are less known. Predation is one of the most important ecological functions because of its community-structuring effects. We studied six forest habitats along a riverside urbanization gradient in Szeged, a major city in southern Hungary, crossed by the river Tisza, to describe how extreme events (e.g., floods) as primary selective pressure act on adaptation in riparian habitats. We found a generally decreasing predation pressure from rural to urban habitats as predicted by the increasing disturbance hypothesis (higher predator abundances in rural than in urban habitats). The only predators that reacted differently to urbanization were ground active arthropods, where results conformed to the prediction of the intermediate disturbance hypothesis (higher abundance in moderately disturbed suburban habitats). We did not find any evidence that communities exposed to extreme flood events were preadapted to the effects of urbanization. The probable reason is that changes accompanied by urbanization are much faster than natural landscape change, so the communities cannot adapt to them.

We studied the impact that two agro-ecological service crops or ASC, (vetch and barley), and two different ASC termination techniques (using a roller crimper or green manure) had on predation pressure in an organic vegetable system. We compared these two ASC termination techniques with a biodegradable plastic mulch, commonly used to control weeds in vegetable organic systems, over two consecutive growing seasons (2014–2015). Predation pressure was evaluated by means of artificial caterpillars made of green plasticine. Attack marks left on them were assigned to predators including chewing insects, birds and mammals. The frequencies of attack were significantly correlated with the activity density of carabids. In both experiments, carabid activity density was higher in ASC terminations than in the biodegradable plastic mulch control. Predation rate was significantly higher in the field with vetch flattened by roller crimper, while no significant difference was detected between termination techniques or in comparison with the control when barley was used as an ASC. The rate of ASC decomposition was higher in vetch than in barley and this could be the reason for the higher activity density of springtails in vetch. Carabid activity density was also positively correlated with springtail abundance. In conclusion, our field experiments showed that artificial caterpillars could represent a good standardized method to assess predation pressure in different habitats.

Humankind draws important benefits from large-scale ecological processes termed ecosystem services, yet the status of several of them is declining. Reliable monitoring methods are essential for tracking the status of ecosystem services. Predation is the mainstay of natural pest control, a key ecosystem service. We used green plasticine caterpillars to monitor predation pressure, and to obtain baseline data on predator activity in transgenic Bt versus non-Bt maize fields in Old and New World countries. Predation pressure was measured at ground and canopy levels using an identical, small-plot experimental design in four European countries (Denmark, Slovakia, Romania and Italy) and Argentina. Total predation rate in maize was 11.7%d −1 (min. 7.2%d −1 in Argentina, max. 29.0%d −1 in Romania). Artificial caterpillars were attacked both by invertebrates (mostly chewing insects with 42.0% of the attack marks, and ants with 7.1%, but also predatory and parasitoid wasps, spiders and slugs), and vertebrates (small mammals 25.5%, and birds 20.2%). Total predation at ground level (15.7%d −1 ) was significantly higher than in maize canopies (6.0%d −1 ) in all countries, except Argentina. We found no significant differences between predator pressure in Bt versus non-Bt maize plots. The artificial caterpillar method provided comparable, quantitative data on predation intensity, and proved to be suitable for monitoring natural pest control. This method usefully expands the existing toolkit by directly measuring ecological function rather than structure.

South America is undergoing a rapid and large scale conversion of natural habitats to cultivated land. Ecosystem services (ESs) still remain important but their level and sustainability are not known. We quantified predation intensity in an Argentinian agricultural landscape containing remnants of the original chaco serrano forest by using artificial sentinel prey. We sought to identify the main predators, and the effect of landscape configuration and maize phenology on predation pressure by invertebrate and vertebrate predators in this landscape. The most common predators were chewing insects (50.4% predation events), birds (22.7%), and ants (17.5%). Overall predation rates in forest fragments (41.6% d-1) were significantly higher than in the surrounding maize fields (21.5% d-1). Invertebrate predation was higher inside and at the edge of forest fragments than within fields, and did not change with increasing distance from a fragment edge, indicating a lack of spillover from the native habitat remnants to the cultivated matrix at the local scale. Distance from a continuous forest had a positive impact on predation by invertebrates and a negative impact on vertebrate predation. Fil: Ferrante, Marco. Aarhus University. Flakkebjerg Research Centre. Department of Agroecology; Dinamarca Fil: González, Ezequiel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentina Fil: Gabor L., Lovei. Aarhus University. Flakkebjerg Research Centre. Department of Agroecology; Dinamarca

International audience; The sustainability of organic vegetable cropping relies on ecosystem services such as biocontrol. Vegetable agroforestry can combine perennial woody crops and non-woody crops, which may alter ground predator activity-density and predation potential. We used living sentinel prey (Cydia pomonella) to assess predation in two different months, as a function of three levels of canopy openness in an agroforestry system combining lettuce crops and grassy strips. Ground beetles and arachnids were sampled throughout the year and we analyzed summer data conjointly to assess potential differences in the activity-density of these major predators between treatments. We found significantly higher predation potential in June in all agroforestry treatments compared to the control. In August, however, no differences were observed. Ground beetles and Opiliones were the major predators involved in observed predation events at both sampling periods. Differences in predation potential in June (- 35% in the control compared to agroforestry treatments) could be due to differences in Pterostichus madidus and Opiliones activity-density, which may have increased due to warmer temperatures under trees compared to the control plot.

Lepidoptera is one of the most diverse orders of insects, their larvae are very abundant in many habitats, and frequent prey of various predators. To decrease predation risk, caterpillars developed several means of defence, among them timing their activity to avoid predators (seeking enemy-free time). Although the enemy-free time hypothesis is often invoked to explain caterpillar behaviour, empirical evidence for it is scarce. We tested whether such enemy-free time exists in a temperate forest by comparing predation pressure on artificial caterpillars during day and night on the ground in forest fragments in Denmark. We found a high predation rate, 23.9% d(-1), and higher predation rate at night (30.9% d(-0.5)) than during the day (17.0% d(-0.5)), both by invertebrate (23.3% d(-0.5) vs. 12.4% d(-0.5)) and vertebrate (8.5% d(-0.5) vs. 3.3% d(-0.5)) predators. The most important predators were chewing insects (73.4% of all attacks) and small mammals (19.0%). Attack rates on red caterpillars were higher (30.0% d(-1)) than on green ones (19.5% d(-1)). Overall, these data do not support the idea that night activity can provide enemy-free time for solitary caterpillars on the temperate forest floor.

The sentinel prey method can quantify predation pressure in various habitats. Real prey is assumed to more realistically mimic the predator experience but the predator can rarely be identified. Artificial prey made of plasticine may lack real chemical cues, but provides information about predator identity. However, the relationship between predation pressure registered by artificial versus real prey is not clear. We tested the relative attractiveness of artificial caterpillars, and intact, wounded, or dead larvae of the cabbage moth (Mamestra brassicae) for the carabid predator Pterostichus melanarius Illiger (Coleoptera: Carabidae). P. melanarius adults were attracted to dead caterpillars more than to live or wounded ones. Coating artificial caterpillars with caterpillar haemolymph increased their attractiveness. However, predators were not attracted more to healthy, real caterpillars than to “untreated” artificial ones. We conclude that using artificial caterpillars does not underestimate predation pressure by this carabid on healthy caterpillars.