Gionata Bocci

Augmenting flower trait diversity in wildflower strips to optimise the conservation of arthropod functional groups for multiple agroecosystem services

AbstractSown wildflower strips are increasingly being established in Europe for enhancing arthropod conservation and the provision of ecosystem services, including biotic pollination and natural pest control. Here we use floral traits to identify different plant functional effect groups. Floral resources were provided in four experimental levels characterised by a cumulatively increasing flower trait diversity and vegetation stand complexity. The first level consisted of a bare control strip, whilst in each subsequent level three wildflower species with different functional traits were added (Level 0: control; Level 1: three Apiaceae species; Level 2: three Apiaceae and three Fabaceae species; Level 3: three Apiaceae, three Fabaceae species, and Centaurea jacea (Asteraceae), Fagopyrum esculentum (Polygonaceae), Sinapis alba (Brassicaceae)). Plots with sown wildflower strip mixtures were located adjacent to experimental plots of organically-managed tomato crop, which is attacked by multiple pests and partially relies on bees for fruit production, and hence dependent on the provision of pollination and pest control services. Results obtained here show that the inclusion of functionally diverse wildflower species was associated with an augmented availability of floral resources across time, and this increased the abundance of bees and anthocorids throughout the crop season. Several natural enemy groups, such as parasitoids, coccinelids and ground-dwelling predators, were not significantly enhanced by the inclusion of additional flower traits within the strips but the presence of flower resources was important to enhance their conservation in an arable cropping system.

Contrasting effects of cover crops on 'hot spot' arbuscular mycorrhizal fungal communities in organic tomato

Arbuscular mycorrhizal fungal (AMF) communities are fundamental in organic cropping systems where they provide essential agro-ecosystem services, improving soil fertility and sustaining crop production. They are affected by agronomic practices, but still, scanty information is available about the role of specific crops, crop rotations and the use of winter cover crops on the AMF community compositions at the field sites. A field experiment was conducted to elucidate the role of diversified cover crops and AMF inoculation on AMF diversity in organic tomato. Tomato, pre-inoculated at nursery with two AMF isolates, was grown following four cover crop treatments: Indian mustard, hairy vetch, a mixture of seven species and a fallow. Tomato root colonization at flowering was more affected by AMF pre-transplant inoculation than by the cover crop treatments. An enormous species richness was found by morphological spore identification: 58 AMF species belonging to 14 genera, with 46 and 53 species retrieved at the end of cover crop cycle and at tomato harvest, respectively. At both sampling times, AMF spore abundance was highest in hairy vetch, but after tomato harvest, AMF species richness and diversity were lower in hairy vetch than in the cover crop mixture and in the mustard treatments. A higher AMF diversity was found at tomato harvest, compared with the end of the cover crop cycle, independent of the cover crop and pre-transplant AMF inoculation. Our findings suggest that seasonal and environmental factors play a major role on AMF abundance and diversity than short-term agronomic practices, including AMF inoculation. The huge AMF diversity is explained by the field history and the Mediterranean environment, where species characteristic of temperate and sub-tropical climates co-occur.

Utilisation of plant functional diversity in wildflower strips for the delivery of multiple agroecosystem services

Increased plant diversity in cropping systems can play an important role in agriculture by enhancing arthropod‐mediated ecosystem services, including biological control and pollination. However, there is limited research investigating the concurrent influence of plant functional diversity within cultivated systems on different arthropod functional groups, the provision of multiple ecosystem services, and crop yield. During a field experiment, repeated over 2 years, we measured the effect of increasing plant functional diversity on community structure of arthropod visitors, the abundance of multiple pests and induced crop damage, and fruit production in two varieties of tomato. Plant resources (floral and extra‐floral nectar and pollen) were included within experimental plots in four levels, with each level increasing the plant functional group richness, based on floral morphology and availability of resources, in a replacement series. The presence of sown flower mixtures in experimental plots was associated with increased abundance and diversity of natural enemy functional groups and an enhanced abundance of bees (Hymenoptera: Apiformes). However, we only detected relatively small variability in arthropod visitors among types of mixtures, and increased abundance of natural enemies did not translate into stronger pest suppression or reduced crop damage. Lepidoptera pest damage was significantly higher in plots adjacent to wildflower strips, an ecosystem disservice, but a significantly higher crop productivity was recorded from these plots. Our results provide evidence that inclusion of non‐crop plant resources in agroecosystems can improve the conservation of beneficial arthropods and may lead to increased crop productivity.

Enhancing plant diversity in agricultural landscapes promotes both rare bees and dominant crop‐pollinating bees through complementary increase in key floral resources

Summary Enhancing key floral resources is essential to effectively mitigate the loss of pollinator diversity and associated provisioning of pollination functions in agro-ecosystems. However, effective floral provisioning measures may diverge among different pollinator conservation targets, such as the conservation of rare species or the promotion of economically important crop pollinators. We examined to what extent such diverging conservation goals could be reconciled. We analysed plant–bee visitation networks of 64 herbaceous semi-natural habitats representing a gradient of plant species richness to identify key resource plants of the three distinct conservation target groups: rare bees (of conservation concern), dominant wild crop-pollinating bees and managed crop-pollinating bees (i.e. honeybees). Considering overall flower visitation, rare bees tended to visit nested subsets of plant species that were also visited by crop pollinators (46% and 77% nestedness in the dissimilarity between rare bees and wild crop pollinators or managed honeybees respectively). However, the set of preferred plant species, henceforth ‘key plant species’ (i.e. those species disproportionately more visited than expected according to their floral abundance) was considerably more distinct and less nested among bee target groups. Flower visits of all bee target groups increased with plant species richness at a similar rate. Importantly, our analyses revealed that an exponential increase in the flower abundance of the identified key plant species and complementarity in the bee visitation pattern across plant species ─ rather than total flower abundance ─ were the major drivers of these relationships. Synthesis and applications. We conclude that the multiple goals of preserving high bee diversity, conserving rare species and sustaining crop pollinators can be reconciled if key plant species of different target groups are simultaneously available. This availability is facilitated by a high floral resource complementarity in the plant community. The list of identified key resource plant species we provide here can help practitioners such as land managers and conservationists to better design and evaluate pollinator conservation and restoration measures according to their goals. Our findings highlight the importance of identifying and promoting such plant species for pollinator conservation in agricultural landscapes.

Landscape complexity and field margin vegetation diversity enhance natural enemies and reduce herbivory by Lepidoptera pests on tomato crop

Agricultural intensification may lead to higher pest pressure through the loss of natural plant assemblages, and associated reduction in natural enemy diversity, while providing increased crop area. We investigate the influence of field margin vegetation and landscape complexity on natural enemy diversity and crop damage caused by two Lepidoptera tomato pests (Tuta absoluta and Noctuidae). At the local scale, fields were bordered with herbaceous field margins of varying vegetation diversity. At the landscape scale, these fields were set in landscapes with increasing landscape complexity. Margin vegetation diversity was higher in landscapes with lower arable land cover, and was associated with increased floral resources and enemy diversity, with the latter being negatively related to T. absoluta-caused fruit injury. Total crop damage increased with arable land cover. These results imply that the suitability of farming practices for the conservation of natural enemies and pest control services is influenced by the landscape context.

TR8: an R package for easily retrieving plant species traits

Summary A large amount of data about plant functional traits are available for researchers, but it is scattered over various data bases; searching and downloading traits values for a specific list of plant species of interest can be a time-consuming and error-prone activity if carried out manually. The TR8 package for R was built to provide plant scientists with a simple tool for retrieving plant functional traits from freely accessible online traitbases.

Local and landscape factors affect sunflower pollination in a Mediterranean agroecosystem

In Europe, the surface devoted to sunflower cultivation has expanded by ∼ 26% from 2006 to 2016. Theoretically, this implies an increasing demand for pollinators, while at the same time, scientific reports claim that pollinator communities worldwide are threatened by multiple stressors such as agrochemicals, the loss of suitable habitats and habitat fragmentation. However, the question that arises is whether insect pollination is still relevant for modern sunflower varieties that are often highly self-fertile. Following recent studies which demonstrate that surrounding land use composition may affect ecosystem service provisioning in cropped fields, this study aims at re-examining the pollination status of sunflower while disentangling the effects of local and landscape variables on sunflower seed set and oil content in Central Italy. Commercial cultivars, regardless of their degree of self-fertility, showed increased seed set and oil content when receiving adequate amounts of cross-pollination; oil composition, though, was not affected by cross-pollination events. Honey bees accounted for the vast majority of pollinators ensuring an overall adequate pollination. Sunflower seed set was higher in fields surrounded by landscapes containing a greater abundance of beehives, early flowering crops, urban areas and woody linear elements; conversely, seed set was lower where herbaceous semi-natural habitats dominated the surrounding landscape. This information is necessary for a science-based planning of agricultural policies and shows that, despite the adoption of self-fertile cultivars, sunflower still benefits from insect pollination and land use planning may affect crop productivity.