Weed diversity is driven by complex interplay between multi-scale dispersal and local filtering

Abstract

<jats:p>Arable weeds are key organisms for biodiversity maintenance and ecosystem service provision in agroecosystems. Disentangling the drivers of weed diversity is critical to counteract the global decline of farmland biodiversity. Even if distinct scale-dependent processes were alternatively proposed, no general framework unifying the multi-scale drivers of weed dynamics has yet emerged. Here, we investigate the joint effects of field- and landscape-scale processes on weed assemblages in 444 arable fields. First, field margins sheltered greater weed diversity than field core, evidencing their role as biodiversity refugia. Second, community similarity between field core and margin decreased with the distance to margin, highlighting a major role of local dispersal. Third, weed diversity at field margins increased with organic field cover in the landscape, pointing out massive regional dispersal. Fourth, while both local and landscape dispersal explained up to 41% of field core weed diversity, crop type strongly modulated their strength, depicting an intense filtering effect by agricultural management. This study sheds new light on the complex multi-scale interactions shaping weed diversity, field margins playing a key role by strengthening regional dispersal and sustaining local dispersal. Land-sharing strategies improving habitat heterogeneity both locally and regionally should largely promote agroecosystem multifunctionality and sustainability.</jats:p>

Proportion of Grassland at Landscape Scale Drives Natural Pest Control Services in Agricultural Landscapes

“…We used sentinel preys to estimate natural pest control potential as it is a standard and efficient method related to predator activity (Lövei and Ferrante, 2017;Boetzl et al, 2020a) and pest regulation (Perez-Alvarez et al, 2019). In each cereal field, we measured natural pest control as the realized predation rate on two common pests: the aphid Acyrthosiphon pisum (Ximenez-Embun et al, 2014) which is commonly used to estimate aphid predation in cereal fields (Winqvist et al, 2011;Ricci et al, 2019), and the weed Viola arvensis (Petit et al, 2017) which is relatively common in cereal fields (Bourgeois et al, 2020). Weed seeds were bought at Herbiseed (Reading, United Kingdom).…”

Do ecological specialization and functional traits explain the abundance–frequency relationship? Arable weeds as a case study

“…First, the influence of regional frequency on local abundance suggests that dispersal dynamics across weed communities can maintain weed pressure and spillover. Weed dispersal plays a key role both in space (exchanges between fields, Bourgeois et al (2020)) and in time (through the seed bank, Mahaut, Fried, and Gaba (2018)) by reducing the probability of local extinction (rescue effect) and increasing local abundance (Hubbell, 1997). In addition, since specialization to arable habitat was positively related to local abundance, the dispersal dynamic of abundant species from regional to local level is assumed to occur predominantly for weeds that are specialist of arable habitat and, therefore, mainly between arable fields.…”

Agricultural intensification erodes taxonomic and functional diversity in Mediterranean olive groves by filtering out rare species

“…In very simple and homogeneous agricultural landscapes, natural habitat patches are extremely rare and are expected to contribute negligibly to crop biodiversity, while as landscape complexity increases, the diversity within crops is expected to increase by spillover from natural habitats until saturation at high levels of complexity (Concepción et al, 2008;Tscharntke et al, 2005). In the case of herbs, increases in natural habitat cover surrounding the crop could mitigate agricultural intensification effects at the farm scale, providing a pool of herb species less similar to the ones in the field core (Bourgeois et al, 2020). The interplay between the level of local agricultural intensification and the degree of landscape complexity is thought to determine the effectiveness of AES on farmland biodiversity recovery (Kleijn et al, 2011;Tscharntke et al, 2005Tscharntke et al, , 2012, and their synergistic effects have been confirmed in infield herb assemblages (Roschewitz et al, 2005).…”