Natural enemies have been shown to be effective agents for controlling insect pests in crops. However, it remains unclear how different natural enemy guilds contribute to the regulation of pests and ...how this might be modulated by landscape context. In a field exclusion experiment in oilseed rape (OSR), we found that parasitoids and ground-dwelling predators acted in a complementary way to suppress pollen beetles, suggesting that pest control by multiple enemies attacking a pest during different periods of its occurrence in the field improves biological control efficacy. The density of pollen beetle significantly decreased with an increased proportion of non-crop habitats in the landscape. Parasitism had a strong effect on pollen beetle numbers in landscapes with a low or intermediate proportion of non-crop habitats, but not in complex landscapes. Our results underline the importance of different natural enemy guilds to pest regulation in crops, and demonstrate how biological control can be strengthened by complementarity among natural enemies. The optimization of natural pest control by adoption of specific management practices at local and landscape scales, such as establishing non-crop areas, low-impact tillage, and temporal crop rotation, could significantly reduce dependence on pesticides and foster yield stability through ecological intensification in agriculture.
Floral plantings are promoted to foster ecological intensification of agriculture through provisioning of ecosystem services. However, a comprehensive assessment of the effectiveness of different ...floral plantings, their characteristics and consequences for crop yield is lacking. Here we quantified the impacts of flower strips and hedgerows on pest control (18 studies) and pollination services (17 studies) in adjacent crops in North America, Europe and New Zealand. Flower strips, but not hedgerows, enhanced pest control services in adjacent fields by 16% on average. However, effects on crop pollination and yield were more variable. Our synthesis identifies several important drivers of variability in effectiveness of plantings: pollination services declined exponentially with distance from plantings, and perennial and older flower strips with higher flowering plant diversity enhanced pollination more effectively. These findings provide promising pathways to optimise floral plantings to more effectively contribute to ecosystem service delivery and ecological intensification of agriculture in the future.
Our quantitative synthesis of the impacts of floral plantings on pest control, crop pollination and yield reveals that flower strips, but not hedgerows, enhanced pest control services in adjacent fields by 16% on average, while effects on crop pollination and yield were more variable. Our synthesis identifies several important drivers of this variability in effectiveness of plantings: pollination services declined exponentially with distance from plantings, and perennial and older flower strips with higher flowering plant diversity enhanced pollination more effectively, with important implications for the the design and implementation of these measures to effectively promote ecological intensification of agriculture in the future
Mass‐flowering crops (MFCs) are increasingly cultivated and might influence pollinator communities in MFC fields and nearby semi‐natural habitats (SNHs). Across six European regions and 2 years, we ...assessed how landscape‐scale cover of MFCs affected pollinator densities in 408 MFC fields and adjacent SNHs. In MFC fields, densities of bumblebees, solitary bees, managed honeybees and hoverflies were negatively related to the cover of MFCs in the landscape. In SNHs, densities of bumblebees declined with increasing cover of MFCs but densities of honeybees increased. The densities of all pollinators were generally unrelated to the cover of SNHs in the landscape. Although MFC fields apparently attracted pollinators from SNHs, in landscapes with large areas of MFCs they became diluted. The resulting lower densities might negatively affect yields of pollinator‐dependent crops and the reproductive success of wild plants. An expansion of MFCs needs to be accompanied by pollinator‐supporting practices in agricultural landscapes.
Intraspecific genetic diversity is an important component of biodiversity. A substantial body of evidence has demonstrated positive effects of plant genetic diversity on plant performance. However, ...it has remained unclear whether plant genetic diversity generally increases plant performance by reducing the pressure of plant antagonists across trophic levels for different plant life forms, ecosystems and climatic zones. Here, we analyse 4702 effect sizes reported in 413 studies that consider effects of plant genetic diversity on trophic groups and their interactions. We found that that increasing plant genetic diversity decreased the performance of plant antagonists including invertebrate herbivores, weeds, plant-feeding nematodes and plant diseases, while increasing the performance of plants and natural enemies of herbivores. Structural equation modelling indicated that plant genetic diversity increased plant performance partly by reducing plant antagonist pressure. These results reveal that plant genetic diversity often influences multiple trophic levels in ways that enhance natural pest control in managed ecosystems and consumer control of plants in natural ecosystems for sustainable plant production.
Ecological theory suggests that several nested environmental filters, acting at different spatial scales, shape the assemblages of local plant species. However, it is unclear whether different ...biodiversity components, that is, taxonomy, function and phylogenetic, respond similarly to these filters. The integration of these different components into coherent and comprehensive analytical frameworks also remains unclear. In this study, we developed an approach to test the relative effects of elevation, habitat fragmentation and grazing management on the functional, phylogenetic, and taxonomic structures of mountain pastures. Thirty summer farms, distributed along an elevational gradient were surveyed in the Italian Alps. Within these farms (around 100ha), we identified all areas as one of two types of management (intensive or extensive), and we sampled three plots for each area, a total of 180 plots. Using the same mathematical framework, we quantified the functional (FD), phylogenetic (PD) and taxonomic (TD) diversity of each plot. We tested the influences of three environmental filters (elevation, habitat fragmentation and grazing management), using a series of partial regression analyses within a univariate and multivariate framework, as well as specific permutation schemes that accounted for our nested design. We found that elevation, habitat fragmentation, and grazing management affected the community structure, but in different ways. This finding confirmed that these filters operate at different scales and, despite some similarities, have different effects on various biodiversity components. Interestingly, FD was the only component that responded to all three types of predictors. Regarding functional aspects, elevation, as a broad-scale environmental gradient, showed a greater influence on dominant trait values, whereas at finer scales, grazing management had a primary effect on both dominant trait values and diversity measures. Habitat fragmentation showed a primary influence on TD, probably because the effect on dispersal limitations concerned mostly species availability. The hierarchical, multi-faceted approach adopted in this study yielded insights into the factors influencing biodiversity and community assembly processes in mountain pastures, thereby highlighting the importance of considering multiple facets of diversity in assessing the role of environmental filtering in vegetation structure.
•Despite the high number of agro-ecological publications, few lead to outcomes.•The pathway to outcomes is explored through an interactive web-based tool.•The spiral can be used at all levels, from ...policy makers to farm advisors and schools.•The aim is to inform efforts to enhance biodiversity-based agricultural systems.
The adoption of agro-ecological practices in agricultural systems worldwide can contribute to increased food production without compromising future food security, especially under the current biodiversity loss and climate change scenarios. Despite the increase in publications on agro-ecological research and practices during the last 35 years, a weak link between that knowledge and changed farmer practices has led to few examples of agro-ecological protocols and effective delivery systems to agriculturalists. In an attempt to reduce this gap, we synthesised the main concepts related to biodiversity and its functions by creating a web-based interactive spiral (www.biodiversityfunction.com). This tool explains and describes a pathway for achieving agro-ecological outcomes, starting from the basic principle of biodiversity and its functions to enhanced biodiversity on farms. Within this pathway, 11 key steps are identified and sequentially presented on a web platform through which key players (farmers, farmer networks, policy makers, scientists and other stakeholders) can navigate and learn. Because in many areas of the world the necessary knowledge needed for achieving the adoption of particular agro-ecological techniques is not available, the spiral approach can provide the necessary conceptual steps needed for obtaining and understanding such knowledge by navigating through the interactive pathway. This novel approach aims to improve our understanding of the sequence from the concept of biodiversity to harnessing its power to improve prospects for ‘sustainable intensification’ of agricultural systems worldwide.
Numerous studies have demonstrated that plant species diversity enhances ecosystem functioning in terrestrial ecosystems, including diversity effects on insects (herbivores, predators and ...parasitoids) and plants. However, the effects of increased plant diversity across trophic levels in different ecosystems and biomes have not yet been explored on a global scale. Through a global meta-analysis of 2,914 observations from 351 studies, we found that increased plant species richness reduced herbivore abundance and damage but increased predator and parasitoid abundance, predation, parasitism and overall plant performance. Moreover, increased predator/parasitoid performance was correlated with reduced herbivore abundance and enhanced plant performance. We conclude that increasing plant species diversity promotes beneficial trophic interactions between insects and plants, ultimately contributing to increased ecosystem services.
Landscape context influences wild bee abundance and diversity, alongside pollination‐related services. Growing evidence supports the positive effects of landscape heterogeneity on bee diversity and ...fruit production for pollination‐dependent crops in flatlands. However, little remains known about these relationships in mountainous environments where the landscape matrix surrounding crops is often more complex than in lowlands.
We conducted our study in apple orchards in South Tyrol, an Alpine region in Italy, using pan‐traps, direct observations of visitation frequency and a pollinator exclusion experiment. We investigated the scale‐dependent effects of landscape heterogeneity and other parameters on wild bee assemblages and the related pollination service they provide at five spatial scales (radius 100–2000 m).
We found that landscape heterogeneity positively affected the abundance and richness of wild bees, with the strongest effect at 500 m. We calculated a multidiversity index, reflecting the land‐use intensity based on the species richness of vascular plants, grasshoppers, butterflies, birds and bats. We identified a positive relationship between this multidiversity index and wild bee richness. Additionally, we found that visitation rate of wild bees was negatively affected by crop cover and that abundance of honeybees did not influence wild bee visitation rate or reproductive success. Finally, reproductive success was positively related to semi‐natural habitat cover.
Landscape heterogeneity should be maintained in apple orchards to continue to reap the benefits of vital pollination‐related services. Diversification strategies should be implemented to promote habitat diversity at small scales, even in regions with more than 80% of (semi‐)natural habitats.
Sintesi
L'abbondanza, la diversificazione delle specie e i servizi di impollinazione forniti dalle api selvatiche sono influenzati, tra gli altri fattori, dal paesaggio. Per le aree pianeggianti gli effetti positivi dell'eterogeneità del paesaggio sulla diversità delle api e sulla produzione di frutti per le colture dipendenti dall'impollinazione, sono assodati. Per contro, queste relazioni sono poco conosciute in montagna, dove la matrice paesaggistica che circonda le colture è spesso più complessa che in pianura.
Abbiamo condotto il nostro studio in 14 meleti dell’Alto Adige, utilizzando trappole, osservazioni dirette sulla frequenza di visitazione dei fiori del meleto e facendo anche un esperimento di esclusione degli impollinatori. Abbiamo analizzato gli effetti di alcune caratteristiche del paesaggio sulle comunità di api selvatiche e sul servizio di impollinazione che esse forniscono per cinque scale spaziali (raggio di 100‐2000 m dal centro dei meleti studiati).
Abbiamo riscontrato che l'eterogeneità del paesaggio influisce positivamente sull'abbondanza e sulla ricchezza di specie delle api selvatiche. L'effetto più forte si è verificato a un raggio di 500 m. Il tasso di visita delle api selvatiche sui fiori di melo è stato invece influenzato negativamente dalla percentuale di terreno agricolo coltivato attorno ai siti studiati. L'abbondanza delle api da miele non ha influenzato il tasso di visita delle api selvatiche o l'allegagione. Quest'ultima è risultata invece positivamente correlata all'estensione degli habitat seminaturali.
L'eterogeneità del paesaggio dovrebbe essere mantenuta nei meleti per continuare a beneficiare dei servizi vitali legati all'impollinazione. È necessario attuare strategie di diversificazione per promuovere la diversità degli habitat a piccola scala, anche nelle regioni con oltre l'80% di habitat (semi)naturali.
Zusammenfassung
Der Wildbienenbestand, die Artenvielfalt und die Bestäubungsleistungen werden unter anderem durch den landschaftlichen Kontext beeinflusst. Es gibt immer mehr Belege für die positiven Auswirkungen der landschaftlichen Heterogenität auf die Bienenvielfalt und die Obstproduktion bei bestäubungsabhängigen Kulturen im Flachland. Über diese Zusammenhänge in den Bergen, wo die Landschaftsmatrix rund um die Kulturpflanzen oft komplexer ist als im Flachland, ist jedoch wenig bekannt.
Wir führten unsere Studie in Apfelanlagen in Südtirol, einer Alpinen Region in Italien, durch. Dabei verwendeten wir Fallen, direkte Beobachtungen der Besuchshäufigkeit und ein Experiment zum Ausschluss von Bestäubern. Wir untersuchten die maßstabsabhängigen Auswirkungen der landschaftlichen Heterogenität auf die Wildbienenbestände und die von ihnen erbrachten Bestäubungsleistungen auf fünf räumlichen Skalen (Radius 100 ‐ 2.000 m) um das Zentrum der untersuchten Apfelanlagen.
Wir fanden heraus, dass sich die Heterogenität der Landschaft positiv auf die Abundanz und Artenvielfalt von Wildbienen auswirkte. Die stärkste Auswirkung zeigte sich bei einem Radius von 500 m. Die Besuchsrate der Wildbienen wurde hingegen durch Ackerfläche negativ beeinflusst. Die Abundanz von Honigbienen hatte keinen Einfluss auf die Besuchsrate von Wildbienen oder den Bestäubungserfolg. Schließlich stand der Bestäubungserfolg in einem positiven Zusammenhang mit der Bedeckung durch naturnahe Lebensräume.
Die Heterogenität der Landschaft sollte in Apfelanlagen beibehalten werden, um die Vorteile der lebenswichtigen Bestäubungsleistungen weiterhin nutzen zu können. Es sollten Diversifizierungsstrategien umgesetzt werden, um die Lebensraumvielfalt in kleinem Maßstab zu fördern, selbst in Regionen mit mehr als 80 % natürlichen (und naturnahen) Lebensräumen.
Wild bees thrive in landscapes with a heterogeneous matrix from small to large spatial scales, even in regions with abundant semi‐natural habitats. Higher proportions of semi‐natural habitat in the farmlands promote bee diversity and crop pollination services. Preserving habitat quality and integrity, as indicated by the multidiversity index that reflects a biodiversity measure of the whole ecosystem, is also critical to promoting the conservation of wild bee populations and pollination services.
An understanding of the climate conditions governing spatial variation in the reproductive performance of plants can provide important information about the factors characterizing plant community ...structure, especially in the context of climate change. This study focuses on the effect of climate on the sexual reproductive output of Dactylis glomerata L., a perennial grass species widely distributed throughout temperate regions. An indirect space-for-time substitution procedure was used. Sixty mountain populations of the same target species were surveyed along an elevation gradient, and then, a relevant climate model was used to infer a potential response to climate change over time. Within each population, information on the number of stems, seed number and seed mass were collected. Resource investment in reproduction (RIR) was quantified as seed number × seed mass. A clear variation was found in the reproductive performance of D. glomerata along the elevational gradient: RIR improved with increasing temperature. The best model included only one term: the maximum temperature of the warmest month. This study demonstrates that mountain ecosystems offer particularly good opportunities to study climate effects over relatively short distances and suggests that warming will enhance D. glomerata's reproductive output throughout its elevational range. Furthermore, it can be hypothesized that a potential migration of D. glomerata toward higher altitudes may occur in response to accelerated climate change.
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