TY - JOUR A1 - Holzschuh, Andrea A1 - Dormann, Carsten F. A1 - Tscharntke, Teja A1 - Steffan-Dewenter, Ingolf T1 - Mass-flowering crops enhance wild bee abundance JF - Oecologia N2 - Although agricultural habitats can provide enormous amounts of food resources for pollinator species, links between agricultural and (semi-)natural habitats through dispersal and foraging movements have hardly been studied. In 67 study sites, we assessed the interactions between mass-flowering oilseed rape fields and semi-natural grasslands at different spatial scales, and their effects on the number of brood cells of a solitary cavity-nesting bee. The probability that the bee Osmia bicornis colonized trap nests in oilseed rape fields increased from 12 to 59 % when grassland was nearby, compared to fields isolated from grassland. In grasslands, the number of brood cells of O. bicornis in trap nests was 55 % higher when adjacent to oilseed rape compared to isolated grasslands. The percentage of oilseed rape pollen in the larval food was higher in oilseed rape fields and grasslands adjacent to oilseed rape than in isolated grasslands. In both oilseed rape fields and grasslands, the number of brood cells was positively correlated with the percentage of oilseed rape pollen in the larval food. We show that mass-flowering agricultural habitats—even when they are intensively managed—can strongly enhance the abundance of a solitary bee species nesting in nearby semi-natural habitats. Our results suggest that positive effects of agricultural habitats have been underestimated and might be very common (at least) for generalist species in landscapes consisting of a mixture of agricultural and semi-natural habitats. These effects might also have—so far overlooked—implications for interspecific competition and mutualistic interactions in semi-natural habitats. KW - spillover KW - trap nests KW - pollen KW - oilseed rape KW - canola Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-126852 VL - 172 IS - 2 ER - TY - JOUR A1 - Holzschuh, Andrea A1 - Dormann, Carsten F. A1 - Tscharntke, Teja A1 - Steffan-Dewenter, Ingolf T1 - Mass-flowering crops enhance wild bee abundance JF - Oecologia N2 - Although agricultural habitats can provide enormous amounts of food resources for pollinator species, links between agricultural and (semi-)natural habitats through dispersal and foraging movements have hardly been studied. In 67 study sites, we assessed the interactions between mass-flowering oilseed rape fields and semi-natural grasslands at different spatial scales, and their effects on the number of brood cells of a solitary cavity-nesting bee. The probability that the bee Osmia bicornis colonized trap nests in oilseed rape fields increased from 12 to 59 % when grassland was nearby, compared to fields isolated from grassland. In grasslands, the number of brood cells of O. bicornis in trap nests was 55 % higher when adjacent to oilseed rape compared to isolated grasslands. The percentage of oilseed rape pollen in the larval food was higher in oilseed rape fields and grasslands adjacent to oilseed rape than in isolated grasslands. In both oilseed rape fields and grasslands, the number of brood cells was positively correlated with the percentage of oilseed rape pollen in the larval food. We show that mass-flowering agricultural habitats—even when they are intensively managed—can strongly enhance the abundance of a solitary bee species nesting in nearby semi-natural habitats. Our results suggest that positive effects of agricultural habitats have been underestimated and might be very common (at least) for generalist species in landscapes consisting of a mixture of agricultural and semi-natural habitats. These effects might also have—so far overlooked—implications for interspecific competition and mutualistic interactions in semi-natural habitats. KW - spillover KW - pollen KW - oilseed rape KW - canola KW - trap nests Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-132149 VL - 172 IS - 2 ER - TY - JOUR A1 - Krimmer, Elena A1 - Martin, Emily A. A1 - Holzschuh, Andrea A1 - Krauss, Jochen A1 - Steffan‐Dewenter, Ingolf T1 - Flower fields and pesticide use interactively shape pollen beetle infestation and parasitism in oilseed rape fields JF - Journal of Applied Ecology N2 - Pollen beetles (Brassicogethes spp.) are the main pests of oilseed rape (OSR, Brassica napus) in Europe and responsible for massive yield losses. Upcoming pesticide resistances highlight the need for other means of crop protection, such as natural pest control. Sown flower fields aim to counteract the decrease of insect biodiversity in agricultural landscapes by providing resources to ecosystem service providers. However, the optimal age and size of flower fields to increase natural pest control is still unclear. We conducted experiments on 31 OSR fields located along a gradient of landscape-scale semi-natural habitat (SNH). OSR fields were located adjacent to flower fields which differed in age, continuity and size, or adjacent to crop fields or calcareous grasslands. Pesticide-free areas were established to examine interactive effects of pesticide use and flower field characteristics. The abundance of pollen beetle adults and larvae, parasitism and superparasitism rates in OSR were recorded at increasing distances to the adjacent sites. Flower fields and calcareous grasslands increased pollen beetle parasitism when compared to OSR fields neighbouring crop fields. The threshold for effective natural pest control of 35% could be reached in the pesticide-free areas of OSR fields adjacent to calcareous grasslands and flower fields maintained continuously for at least 6 years. In pesticide-sprayed areas, pollen beetle parasitism and superparasitism declined with increasing distance to the adjacent field. Furthermore, flower fields larger than 1.5 ha were able to improve pollen beetle parasitism more than smaller fields. Synthesis and applications. To promote natural pest control in oilseed rape (OSR), large flower fields should be maintained for several years, to create stable habitats for natural enemies. The continuous maintenance of flower fields should be preferred, as ploughing and resowing after 5–6 years decreased the positive effects of the flower fields on natural pest control in adjacent OSR fields. However, pesticide use can abrogate positive effects of flower fields on pollen beetle parasitism. This study highlights that sown flower fields have the potential to increase natural pest control in OSR, but this potential is depending on its age, continuity and size and can be hindered by pesticide use. KW - agri-environment scheme KW - sown flower field age and size KW - oilseed rape KW - natural pest control KW - ecosystem services KW - distance-decay function KW - Brassicogethes spp. Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-258037 VL - 59 IS - 1 ER - TY - THES A1 - Schneider, Gudrun T1 - Effects of adjacent habitats and landscape composition on biodiversity in semi-natural grasslands and biological pest control in oilseed rape fields T1 - Effekte von Nachbarhabitaten und der Landschaftkomposition auf die Biodiversität in halb-natürlichen Grasländern und auf die biologische Schädlicngskontrolle in Rapsfeldern N2 - 1) Modern European agricultural landscapes form a patchy mosaic of highly fragmented natural and semi-natural habitat remnants embedded in a matrix of intensively managed agricultural land. In those landscapes many organism frequently cross habitat borders including the crop – non-crop boundary, hereby connecting the biotic interactions of multiple habitat types. Therefore biodiversity and ecosystem functions within habitats are expected to depend on adjacent habitat types and the surrounding landscape matrix. In this thesis the biodiversity of non-crop habitats, and ecosystem services and disservices in crop habitats were studied in the human-dominated agricultural landscape in the district Lower Franconia, Bavaria, Germany. First we examined the effect of adjacent habitat type on species composition, diversity and ecosystem functions in semi-natural calcareous grasslands, a biodiversity-rich habitat of high conservation value (chapter 2 and 3). Second we studied the effect of habitat composition in the landscape on herbivory, biological pest control and yield in oilseed rape fields (chapter 4). 2) We examined the effect of adjacent habitat type on the diversity of carabid beetles in 20 calcareous grasslands using pitfall traps. Half of the grasslands were adjacent to a coniferous forest and half to a cereal crop field. We found different species compositions of carabid beetles depending on adjacent habitat type. In addition calcareous grasslands adjacent to crop fields harboured a higher species richness and activity density but a lower evenness of carabid beetles than calcareous grasslands adjacent to forests. These differences can be explained by the spillover of carabid beetles from the adjacent habitats. After crop harvest carabid beetle activity density in crop fields decreased while in parallel the activity density in the calcareous grasslands adjacent to the crop fields increased, indicating an unidirectional carabid beetle spillover. Our results underline that type and management of adjacent habitats affect community composition and diversity in calcareous grasslands. Therefore nature conservation measures, which focused on the improvement of local habitat quality so far, additionally need to consider adjacent habitat type. 3) In addition to carabid beetle communities we also surveyed predation rates of ground-dwelling predators on the same calcareous grasslands in two study periods (June and late August). As ground-dwelling predators of forests or crop fields can move into adjacent calcareous grasslands we expected different predation rates depending on adjacent habitat type. We exposed in total 32.000 lady bird eggs as prey items on the calcareous grasslands in distances of 5 and 20m from the habitat border. We found higher predation rates on calcareous grasslands adjacent to forests than on calcareous grasslands adjacent to crop fields, but only on cool days. On warm days a very high extent (often 100%) of the exposed prey items were consumed adjacent to both habitat types, which did not allow the detection of possible differences between the adjacent habitat types. Predation rates differed not between the two study periods or the two distances to the habitat edge. The higher predation rates adjacent to forests can be explained by the spillover of ground-dwelling predators from forests into calcareous grasslands. Our results show, that spillover into semi-natural habitats affects ecosystem functioning in addition to species composition and diversity. 4) In chapter 4 of this thesis we examined the effect of spatiotemporal changes in crop cover on pest - natural enemy interactions and crop yields. During two study years we surveyed the abundance of adult and larval pollen beetles, parasitism of pollen beetle larvae by a hymenopteran parasitoid and oilseed rape yields of 36 oilseed rape fields. The surrounding landscape of the fields (1 km radius) differed in the oilseed rape proportion and in the inter-annual change in the oilseed rape proportion since the previous year. We found a dilution effect, i.e. a decreasing abundance with increasing oilseed rape proportions, for pollen beetle larvae and parasitoids in both study years and for adult pollen beetles in one study year. Oilseed rape yields increased with increasing oilseed rape proportions. Inter-annual changes in oilseed rape proportions led to inter-annual crowding and dilution effects for pollen beetles, but had no effect on parasitism or yield. Our results indicate the potential to reduce pest loads and increase yields in intensively managed oilseed rape fields by a coordinated management of the spatiotemporal oilseed rape cover in the landscape. 5) In summary, we showed in this thesis that the biodiversity and functioning of crop and non-crop habitats within agricultural landscapes is affected by the spillover of organisms and thus by the habitat composition in the close surrounding and in the broader landscape context. Spillover affects also ecosystem services and disservices and therefore crop productivity. Thereby the spatial and temporal variation of specific crop types in the landscape can be of particular importance for crop yields. Thus a coordinated landscape wide management can help to optimize both biodiversity conservation and the delivery of ecosystem services and thus crop yields. Future studies integrating landscape effects across several ecosystem functions, multiple taxonomic groups and different crop types are necessary to develop definite landscape management schemes. N2 - 1) Heutige europäische Agrarlandschaften bestehen aus einem Mosaik stark fragmentierter natürlicher und halbnatürlicher Habitate, die in eine Matrix aus intensiv bewirtschafteten Agrarflächen eingebettet sind. In solchen Landschaften überqueren Organismen häufig Habitatgrenzen, einschließlich der Grenze zwischen Agrar- und Nichtagrarhabitaten. Dabei verknüpfen sie die biotischen Interaktionen der verschiedenen Habitate miteinander. Deshalb ist zu erwarten, dass die Diversität und die Ökosystemfunktionen in Habitaten auch von den Nachbarhabitaten und der umgebenden Landschaft beeinflusst werden. In der vorliegenden Arbeit untersuchten wir die Diversität halbnatürlicher Habitate sowie die Ökosystemdienstleistungen in Agrarhabitaten im Bezirk Unterfranken in Bayern, Deutschland. Zum einen untersuchten wir den Einfluss von zwei verschiedenen Nachbarhabitattypen auf die Artenzusammensetzung, die Diversität und die Ökosystemfunktionen in halbnatürlichen Kalkmagerrasen, einem sehr artenreichen Habitat mit hohem Naturschutzwert (Kapitel 2 und 3). Zum anderen untersuchten wir den Einfluss der Habitatzusammensetzung in der Landschaft auf die Herbivorie, die biologische Schädlingskontrolle und den Ertrag in Rapsfeldern (Kapitel 4). 2) Mit Hilfe von Barberfallen untersuchten wir den Einfluss von zwei benachbarten Habitattypen auf die Diversität von Laufkäfern in 20 Kalkmagerrasen. Die Hälfte der Kalkmagerrasen grenzte an einen Nadelwald, die andere Hälfte an einen Getreideacker. Wir fanden unterschiedliche Artenzusammensetzungen der Laufkäfer in Abhängigkeit vom Nachbarhabitat. Außerdem fanden wir auf den Kalkmagerrasen neben Getreideäckern einen höheren Artenreichtum und eine höhere Aktivitätsdichte sowie eine geringere Evenness der Laufkäfer als auf den Kalkmagerrasen neben Nadelwäldern. Diese Unterschiede können durch den spillover von Laufkäfern aus den zwei unterschiedlichen Nachbarhabitaten erklärt werden. Nach der Getreideernte sank die Aktivitätsdichte der Laufkäfer auf den Getreideäckern und stieg parallel in den benachbarten Kalkmagerrasen an. Das weist auf einen einseitig gerichteten Spillover der Laufkäfer vom Acker auf die Kalkmagerrasen nach der Getreideernte hin. Unsere Ergebnisse zeigen, dass sowohl der Habitattyp als auch das Management benachbarter Habitate die Artenzusammensetzung und die Diversität auf Kalkmagerrasen beeinflusst. Daher sollten Naturschutzmaßnahmen, welche sich bisher nur auf die Verbesserung der lokalen Habitatqualität konzentrierten, zusätzlich den Habitattyp und das Management benachbarter Habitate berücksichtigen. 3) Neben der Zusammensetzung der Laufkäfergemeinschaften untersuchten wir auf den gleichen Kalkmagerrasen die Prädationsraten von auf dem Boden lebenden Prädatoren in zwei Untersuchungszeiträumen (Juni und Ende August). Da Prädatoren benachbarter Wälder oder Äcker auch in Kalkmagerrasen eindringen können, erwarteten wir unterschiedliche Prädationsraten in Abhängigkeit vom Nachbarhabitat. Wir brachten insgesamt 32.000 Marienkäfereier als Beute auf den Kalkmagerrasen aus. Die Eier wurden in Distanzen von 5 m und 20 m zur Habitatgrenze exponiert. Wir fanden höhere Prädationsraten auf den Kalkmagerrasen neben Wäldern als auf denen neben Äckern, allerdings nur an kühlen Tagen. An warmen Tagen wurden die exponierten Eier neben beiden Nachbarhabitaten zu sehr hohen Anteilen (oft zu 100%) konsumiert, was es nicht ermöglichte potentielle Unterschiede zwischen den beiden Nachbarhabitattypen zu ermitteln. Wir fanden keine Unterschiede in den Prädationsraten zwischen den beiden Untersuchungszeiträumen oder zwischen den zwei Distanzen zur Habitatgrenze. Die höheren Prädationsraten auf Kalkmagerrasen neben Wäldern an kühlen Tagen können durch den spillover von am Boden lebenden Prädatoren aus den Wäldern in die Kalkmagerrasen erklärt werden. Unsere Ergebnisse zeigen, dass Spillover in halbnatürliche Habitate neben der Zusammensetzung der Lebensgemeinschaft auch Ökosystemfunktionen beeinflussen kann. 4) In Kapitel 4 dieser Arbeit untersuchten wir den Einfluss von räumlichen und zeitlichen Änderungen in der Rapsanbaufläche auf die Interaktionen zwischen Schädlingen und natürlichen Gegenspielern sowie auf Erträge. Dazu untersuchten wir in zwei Jahren auf insgesamt 36 Rapsfeldern die Abundanz adulter und larvaler Rapsglanzkäfer, Parasitierungsraten von Rapsglanzkäferlarven durch eine Schlupfwespe und Rapserträge. Die Landschaften im 1km Radius um die Rapsfelder unterschieden sich im Rapsanteil und in der Änderung des Rapsanteils seit dem Vorjahr. Wir fanden Verdünnungseffekte, d.h. eine sinkende Abundanz mit zunehmendem Rapsanteil, für Rapsglanzkäferlarven und Parasitoide in beiden Untersuchungsjahren und für adulte Rapsglanzkäfer in einem Untersuchungsjahr. Rapserträge stiegen mit höheren Rapsanteilen in der Landschaft. Eine Vergrößerung des Rapsanteils seit dem Vorjahr führte zu einer Verdünnung der Rapsglanzkäferpopulationen auf der vergrößerten Rapsfläche und eine Verringerung des Rapsanteils zur Konzentration auf der verkleinerten Rapsfläche. Die zeitliche Änderung des Rapsanteils hatte aber keinen Einfluss auf die Parasitierungsrate oder den Ertrag. Unsere Ergebnisse unterstreichen das Potential durch Management der räumlichen und zeitlichen Verteilung der Rapsanbaufläche Schädlingsdichten verringern und Rapserträge erhöhen zu können. 5) Zusammenfassend zeigt die vorliegende Arbeit, dass die Biodiversität und die Funktionen von Agrar- und Nichtagrarhabitaten in Agrarlandschaften durch den Spillover von Organismen und folglich durch die Habitatzusammensetzung in der unmittelbaren und weiteren Umgebung bestimmt werden. Spillover beeinflusst dabei auch Ökosystemdienstleistungen und daher die Produktivität in der Landwirtschaft. Die räumliche und zeitliche Variation der Anbaufläche einzelner Anbaufrüchte hat dabei eine besondere Bedeutung für landwirtschaftliche Erträge. Daher kann ein koordiniertes Landschaftsmanagement helfen, sowohl die Biodiversität in der Landschaft als auch die Produktivität von Agrarhabitaten zu optimieren. Um konkrete Landschaftsmanagementpläne entwickeln zu können, sind weitere Studien, die gleichzeitig mehrere Ökosystemfunktionen, verschiedene taxonomische Gruppen und unterschiedliche Anbaufrüchte untersuchen, nötig. KW - Landschaftsökologie KW - spillover KW - biological pest control KW - oilseed rape KW - calcareous grassland KW - crop harvest KW - community composition KW - landscape ecology KW - ecosystem services KW - Magerrasen KW - Rapsanbau KW - Laufkäfer Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-113549 ER - TY - JOUR A1 - Fricke, Ute A1 - Redlich, Sarah A1 - Zhang, Jie A1 - Benjamin, Caryl S. A1 - Englmeier, Jana A1 - Ganuza, Cristina A1 - Haensel, Maria A1 - Riebl, Rebekka A1 - Rojas‐Botero, Sandra A1 - Tobisch, Cynthia A1 - Uhler, Johannes A1 - Uphus, Lars A1 - Steffan‐Dewenter, Ingolf T1 - Earlier flowering of winter oilseed rape compensates for higher pest pressure in warmer climates JF - Journal of Applied Ecology N2 - Global warming can increase insect pest pressure by enhancing reproductive rates. Whether this translates into yield losses depends on phenological synchronisation of pests with their host plants and natural enemies. Simultaneously, landscape composition may mitigate climate effects by shaping the resource availability for pests and their antagonists. Here, we study the combined effects of temperature and landscape composition on pest abundances, larval parasitism, crop damage and yield, while also considering crop phenology, to identify strategies for sustainable management of oilseed rape (OSR) pests under warming climates. In all, 29 winter OSR crop fields were investigated in different climates (defined by multi‐annual mean temperature, MAT) and landscape contexts in Bavaria, Germany. We measured abundances of adult pollen beetles and stem weevil larvae, pollen beetle larval parasitism, bud loss, stem damage and seed yield, and calculated the flowering date from growth stage observations. Landscape parameters (proportion of non‐crop and OSR area, change in OSR area relative to the previous year) were calculated at six spatial scales (0.6–5 km). Pollen beetle abundance increased with MAT but to different degrees depending on the landscape context, that is, increased less strongly when OSR proportions were high (1‐km scale), interannually constant (5‐km scale) or both. In contrast, stem weevil abundance and stem damage did not respond to landscape composition nor MAT. Pollen beetle larval parasitism was overall low, but occasionally exceeded 30% under both low and high MAT and with reduced OSR area (0.6‐km scale). Despite high pollen beetle abundance in warm climates, yields were high when OSR flowered early. Thereby, higher temperatures favoured early flowering. Only among late‐flowering OSR crop fields yield was higher in cooler than warmer climates. Bud loss responded analogously. Landscape composition did not substantially affect bud loss and yield. Synthesis and applications: Earlier flowering of winter OSR compensates for higher pollen beetle abundance in warmer climates, while interannual continuity of OSR area prevents high pollen beetle abundance in the first place. Thus, regional coordination of crop rotation and crop management promoting early flowering may contribute to sustainable pest management in OSR under current and future climatic conditions. KW - canola KW - climate‐smart pest management KW - crop rotation KW - global warming KW - oilseed rape KW - pollen beetle KW - seed yield KW - stem weevil Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-312562 VL - 60 IS - 2 SP - 365 EP - 375 ER - TY - JOUR A1 - Bartomeus, Ignasi A1 - Potts, Simon G. A1 - Steffan-Dewenter, Ingolf A1 - Vaissiere, Bernard E. A1 - Woyciechowski, Michal A1 - Krewenka, Kristin M. A1 - Tscheulin, Thomas A1 - Roberts, Stuart P. M. A1 - Szentgyoergyi, Hajnalka A1 - Westphal, Catrin A1 - Bommarco, Riccardo T1 - Contribution of insect pollinators to crop yield and quality varies with agricultural intensification JF - PEERJ N2 - Background. Up to 75% of crop species benefit at least to some degree from animal pollination for fruit or seed set and yield. However, basic information on the level of pollinator dependence and pollinator contribution to yield is lacking for many crops. Even less is known about how insect pollination affects crop quality. Given that habitat loss and agricultural intensification are known to decrease pollinator richness and abundance, there is a need to assess the consequences for different components of crop production. Methods. We used pollination exclusion on flowers or inflorescences on a whole plant basis to assess the contribution of insect pollination to crop yield and quality in four flowering crops (spring oilseed rape, field bean, strawberry, and buckwheat) located in four regions of Europe. For each crop, we recorded abundance and species richness of flower visiting insects in ten fields located along a gradient from simple to heterogeneous landscapes. Results. Insect pollination enhanced average crop yield between 18 and 71% depending on the crop. Yield quality was also enhanced in most crops. For instance, oilseed rape had higher oil and lower chlorophyll contents when adequately pollinated, the proportion of empty seeds decreased in buckwheat, and strawberries' commercial grade improved; however, we did not find higher nitrogen content in open pollinated field beans. Complex landscapes had a higher overall species richness of wild pollinators across crops, but visitation rates were only higher in complex landscapes for some crops. On the contrary, the overall yield was consistently enhanced by higher visitation rates, but not by higher pollinator richness. Discussion. For the four crops in this study, there is clear benefit delivered by pollinators on yield quantity and/or quality, but it is not maximized under current agricultural intensification. Honeybees, the most abundant pollinator, might partially compensate the loss of wild pollinators in some areas, but our results suggest the need of landscape-scale actions to enhance wild pollinator populations. KW - biodiversity KW - pollination KW - honeybee KW - wild bees KW - agroecosystems KW - native pollinators KW - species richness KW - bee pollinators KW - wild KW - ecosystemservices KW - fruit-quality KW - oilseed rape KW - land-use KW - honey KW - patterns Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-116928 SN - 2167-9843 VL - 2 IS - e328 ER -