1,721,286 research outputs found
Wildflower strips in the agroecosystem for pollinator biodiversity restoration: Which plant species are capable of self-seeding?
Full text linkThe success of wildflower strips for conserving pollinator biodiversity is often hampered by their poor sustainability, attributable to the short duration lifespan of the sown species. This three-year experiment aimed to: i) select the plant species that survived the agronomic disturbance practices implemented and ii) verify which crop management approach favoured their sustainability. Six experimental strips along the longest edges of the adjacent wheat crop were sown during the fall of 2019. The annual wildflower species that showed the best performances in emergence dynamics and seedling growth were some wildflowers derived from segetal weeds that are presently rare in conventional agroecosystems. The species Centaurea cyanus, Agrostemma githago, Glebionis coronaria among others attained the phenological stage of flowering most consistently, and also had the lowest mortality rates in the plant community studied. Despite preparing a stale seedbed, weeds were the most significant obstacle to the sustainability of the strips over time. Soil harrowing at the end of the summer lifecycle led to better plant survival performances (10.9 %) compared to senescent plant shredding (4.8 %). Harrowing also resulted in a greater wildflower survival the following year, as well as a higher number of pollinator visits. Honeybee visits were decreased by wildflower strip thinning over time, probably due to their typical constancy in the daily foraging choice for the same abundant species. A similar reduction was observed by the Lepidoptera. In contrast, generalist pollinators (i.e. Syrphidae, Bombyliidae, solitary bees and Coleoptera) were the least demanding pollinators in terms of the plant biodiversity of the sustainable wildflower strip. Harrowing led to a greater biodiversity of both wildflowers and pollinators (Shannon index, H '), and a lower weed dominance (Simpson index, D), compared to shredding. In summary, some segetal wildflowers could be incorporated into sustainable wildflower strips as they are self-seeding
Wildflowers-pollinator-crab spider predator food-web as indicator of the agroecosystem biodiversity
Full text linkWildflowers play a crucial role in the functionality of the agroecosystem food chain. In order to investigate the role of biodiversity in the relationships between wildflowers, relative pollinators and their crab spider predators, six wildflower communities, characterized by a different botanical complexity, were sown in a two-year experiment. The selected Mediterranean species flowered between March and September, with a peak during May. The indices of dominance (D) and biodiversity (H') of the wildflower communities confirmed two expected levels of floristic complexity of the oligo-specific plant communities (only three species) in comparison to the poly-specific wildflower communities (a further 20 species for each oligo-specific plant community). The greater floristic biodiversity facilitated a greater pollinator biodiversity (bees, solitary bees, bumblebees, lepidoptera, diptera syrphidae and bombyliidae) but the respective total visitation rate was unchanged. In the case of the lower floristic complexity (oligo-specific plant communities), the dominance of bees increased, confirming their tendency to always choose the same wildflower species to visit. The evaluation of the crab spiders detected on flowers, waiting for pollinators, showed a significant reduction in the case of additional botanical complexity. Indeed, significant linear regressions (p < 0.05) showed a direct relationship between the number of crab spiders observed and the dominance indices of the various wildflower communities. The paper also discusses the possible ecological role of crab spiders in the biodiversity sustainability of the various wildflower communities
Weed role for pollinator in the agroecosystem: Plant–insect interactions and agronomic strategies for biodiversity conservation
Full text linkThe growing interest in safeguarding agroecosystem biodiversity has led to interest in studying ecological interactions among the various organisms present within the agroecosystem. Indeed, mutualisms between weeds and pollinators are of crucial importance as they influence the respective survival dynamics. In this review, the mutualistic role of flower visitors and the possible (often predominant) abiotic alternatives to insect pollination (self- and wind-pollination) are investigated. Mutualistic relations are discussed in terms of reward (pollen and/or nectar) and attractiveness (color, shape, scent, nectar quality and quantity), analyzing whether and to what extent typical weeds are linked to pollinators by rigid (specialization) or flexible (generalization) mutualistic relations. The entomofauna involved is composed mainly of solitary and social bees, bumblebees, Diptera, and Lepidoptera. While some of these pollinators are polylectic, others are oligolectic, depending on the shape of their mouthparts, which can be suited to explore the flower corollas as function of their depths. Consequently, the persistence dynamics of weed species show more successful survival in plants that are basically (occasional insect pollination) or totally (self and/or wind pollination) unspecialized in mutualistic relations. However, even weed species with typical abiotic pollination are at times visited during periods such as late summer, in which plants with more abundant rewards are insufficiently present or completely absent. Many typically insect-pollinated weeds can represent a valid indicator of the ecological sustainability of crop management techniques, as their survival dynamics are closely dependent on the biodiversity of the surrounding entomofauna. In particular, the presence of plant communities of species pollinated above all by butterflies (e.g., several Caryophyllaceae) gives evidence to the ecological compatibility of the previous agronomic management, in the sense that butterflies require certain weed species for oviposition and subsequent larva rearing and, therefore, provide further evidence of plant biodiversity in the environment
L.: Germination ecology, soil seed bank, and emergence dynamics in diversified cropping systems
No full textHeliotropium europaeum is a toxic annual weed that has been found with increasing frequency in the Mediterranean agro-environment. We investigated, both in laboratory and in field, the ecological aspects of this species in order to verify a possible connection between cropping systems and population increase. Its germination, characterized by a high thermal optimum (about 35 degrees C) is markedly reduced by burial. Strong depth-mediated germination inhibition was observed with over 2 cm of burial. Nongerminated seeds undergo a secondary dormancy highlighting their ability to form a persistent seed bank. Indeed the seed bank analysis carried out in an agroecosystem based on minimum tillage cropping systems showed a seed accumulation in the shallowest soil layers. The hypothesis that poor seed burial plays a crucial role in the population dynamics of this species was confirmed by the drastic reduction in seedling emergence after only 1 year of plowing. A strongly reduced emergence percentage was shown which causes not only a lower seedling density but also a lower inflorescence density and respective seed ripening. In conclusion, there is a clear relationship between an increase in this species and cultivation systems based on minimum tillage
3D-partition functions on the sphere: exact evaluation and mirror symmetry
No full textWe study N = 4 quiver theories on the three-sphere. We compute partition functions using the localisation method by Kapustin et al. solving exactly the matrix integrals at finite N, as functions of mass and Fayet-Iliopoulos parameters. We find a simple explicit formula for the partition function of the quiver tail T(SU(N)). This formula opens the way for the analysis of star-shaped quivers and their mirrors (that are the Gaiotto-type theories arising from M5 branes on punctured Riemann surfaces). We provide non-perturbative checks of mirror symmetry for infinite classes of theories and find the partition functions of the TN theory, the building block of generalised quiver theories. © 2012 SISSA
Soil texture involvement in wildflower strip ecosystem services delivery in Mediterranean agro-environment
Full text linkThe biodiversity restoration of the agroecosystem through wildflower strips is one of the most important agro-nomic strategies of the last few decades. However, poor knowledge of the bio-agronomic characteristics of the various wildflower species often leads to suboptimal performances especially as a result of their poor seed germination and poor seedling emergence due to the erratic soil texture. A two-year experiment involving the sowing of eighteen wildflower species in different texture conditions highlighted how some species emerged earlier or more effectively than others and verifying the consequent ecosystem service provided to pollinators. Species with smaller seeds were more inhibited by sowing in soil with high content of clay. Additionally, an inverse relationship (Boltzmann's sigmoidal regression) was found between seed weight and soil-mediated in-hibition. This soil-mediated inhibition was higher in the clayey textured soil, showing that this inhibition was mediated both by seed weight and by the clay particles of the soil. The reciprocal interference between the emerged seedlings also determined a further decline in the wildflower species with small seeds. This differing agronomic performance, after sowing in the two different soil textures, did not affect the number of pollinator visits. Performance differed both in terms of floristic biodiversity and pollinator biodiversity. Finally, the experiment highlighted the importance of the appropriate selection of the wildflower species for biodiversity restoration -not only in terms of pollen and nectar availability for pollinators, but also in terms of compatibility with the soil texture in which the wildflower seeds are sown
Role of durum wheat (Triticum durum Desf.) canopy height on Sinapis arvensis L. growth and seed production.
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