Worldwide decline of the entomofauna: A review of its drivers

Mycorrhizal fungi are a heterogeneous group of diverse fungal taxa, associated with the roots of over 90% of all plant species. Recently, state-of-the-art molecular and genetic tools, coupled to high-throughput sequencing and advanced microscopy, have led to the genome and transcriptome analysis of several symbionts. Signalling pathways between plants and fungi have now been described and the identification of several novel nutrient transporters has revealed some of the cellular processes that underlie symbiosis. Thus, the contributions of each partner in a mycorrhizal association are starting to be unravelled. This new knowledge is now available for use in agricultural practices.

http://www.biobits.di.unipmn.it/images/Documenti/review_bonfante_genre.pdf

Mechanisms underlying beneficial plant–fungus interactions in mycorrhizal symbiosis

Weeds are major constraints on crop production, yet as part of the primary producers within farming systems, they may be important components of the agroecosystem. Using published literature, the role of weeds in arable systems for other above-ground trophic levels are examined. In the UK, there is evidence that weed flora have changed over the past century, with some species declining in abundance, whereas others have increased. There is also some evidence for a decline in the size of arable weed seedbanks. Some of these changes reflect improved agricultural efficiency, changes to more winter-sown crops in arable rotations and the use of more broad-spectrum herbicide combinations. Interrogation of a database of records of phytophagous insects associated with plant species in the UK reveals that many arable weed species support a high diversity of insect species. Reductions in abundances of host plants may affect associated insects and other taxa. A number of insect groups and farmland birds have shown marked population declines over the past 30 years. Correlational studies indicate that many of these declines are associated with changes in agricultural practices. Certainly reductions in food availability in winter and for nestling birds in spring are implicated in the declines of several bird species, notably the grey partridge, Perdix perdix . Thus weeds have a role within agroecosystems in supporting biodiversity more generally. An understanding of weed competitivity and the importance of weeds for insects and birds may allow the identification of the most important weed species. This may form the first step in balancing the needs for weed control with the requirements for biodiversity and more sustainable production methods.

The role of weeds in supporting biological diversity within crop fields

Legumes can enter into symbiotic relationships with both nitrogen-fixing bacteria (rhizobia) and mycorrhizal fungi. Nodulation by rhizobia results from a signal transduction pathway induced in legume roots by rhizobial Nod factors. DMI3 ,a Medicago truncatula gene that acts immediately downstream of calcium spiking in this signaling pathway and is required for both nodulation and mycorrhizal infection, has high sequence similarity to genes encoding calcium and calmodulin-dependent protein kinases (CCaMKs). This indicates that calcium spiking is likely an essential component of the signaling cascade leading to nodule development and mycorrhizal infection, and sheds light on the biological role of plant CCaMKs.

Dependent Protein Kinase Required for Bacterial and Fungal Symbioses

A review of the abundance and diversity of invertebrate and plant foods of granivorous birds in northern europe in relation to agricultural change

Achieving sustainable crop production while feeding an increasing world population is one of the most ambitious challenges of this century1. Meeting this challenge will necessarily imply a drastic reduction of adverse environmental effects arising from agricultural activities2. The reduction of pesticide use is one of the critical drivers to preserve the environment and human health. Pesticide use could be reduced through the adoption of new production strategies3–5; however, whether substantial reductions of pesticide use are possible without impacting crop productivity and profitability is debatable6–17. Here, we demonstrated that low pesticide use rarely decreases productivity and profitability in arable farms. We analysed the potential conflicts between pesticide use and productivity or profitability with data from 946 non-organic arable commercial farms showing contrasting levels of pesticide use and covering a wide range of production situations in France. We failed to detect any conflict between low pesticide use and both high productivity and high profitability in 77% of the farms. We estimated that total pesticide use could be reduced by 42% without any negative effects on both productivity and profitability in 59% of farms from our national network. This corresponded to an average reduction of 37, 47 and 60% of herbicide, fungicide and insecticide use, respectively. The potential for reducing pesticide use appeared higher in farms with currently high pesticide use than in farms with low pesticide use. Our results demonstrate that pesticide reduction is already accessible to farmers in most production situations. This would imply profound changes in market organization and trade balance. Pesticide is a threat to the environment and human health. Whether reducing pesticide would necessarily undermine crop productivity remains elusive. Analyses of data from 946 farms in France show that reducing pesticide rarely decreases productivity.

Reducing pesticide use while preserving crop productivity and profitability on arable farms

Aim The problems in public health and field management in France caused by Ambrosia artemisiifolia L. require a better knowledge of the introduction and naturalization of this species in both the past and present. Location France. Methods The pattern of spread of A. artemisiifolia was investigated through the study of herbarium specimens. More than 1200 specimens were found in 58 herbaria and virtual herbaria in France and in bordering countries. The spread was analysed by mapping the localities for each 30-year period since 1863. Specific indications as 'new plant' were used to determine the timing of the introduction of the species into a new area. Results It seems that the spread of A. artemisiifolia is not linked to its presence in botanical gardens. The study of specimen labels indicates that this species has been introduced in France in seed crops at various independent geographical points and at various times since its introduction in natural habitats. Commercial trade and American troops have contributed to its spread. Main conclusions The spread of the species in area and in time over France showed no clear front: new localities separated by large distances were colonized simultaneously. Cumulative numbers of localities show a continuous increase during the twentieth century. Herbarium specimens can be used to follow the spread of A. artemisiifolia.

The historical spread of Ambrosia artemisiifolia L. in France from herbarium records

Arable weed decline in Northern France: Crop edges as refugia for weed conservation?

(1) Spatial pattern of weeds was analysed in an arable-soil seed bank after winter barley. Three hundred samples were taken in a 7-5 x 10m area. Three indices of dispersion (variance-to-mean ratio, Lloyd's mean crowding and Lloyd's patchiness) and the Moran's I statistic of spatial autocorrelation were calculated. (2) The seed bank of the field was almost exclusively composed of annual species, dominated by Thlaspi arvense (43.8%) and a subset of six species (41-7%). (3) For most species with a mean higher than 0-2 seeds per core, the seed pattern was patchy. Only two species, Avena fatua and Chenopodium polyspermum, had random pattern. For the other species, two types of aggregation have been found due to biological and agricultural factors.

Fabrice Dessaint

Papers

Reducing pesticide use while preserving crop productivity and profitability on arable farms

The historical spread of Ambrosia artemisiifolia L. in France from herbarium records

Arable weed decline in Northern France: Crop edges as refugia for weed conservation?

Spatial pattern analysis of weed seeds in the cultivated soil seed bank.

Weed species richness in winter wheat increases with landscape heterogeneity