The Potential of Arable Weeds to Reverse Invertebrate Declines and Associated Ecosystem Services in Cereal Crops

Abstract

There is global concern that invertebrate populations are declining rapidly, particularly in agricultural habitats. Declines have been attributed to the intensification of farming systems, with many studies focussing on a lack of semi-natural habitat in the landscape and the use of insecticides. However, within-field arable weeds are also an important driver of invertebrate abundance and the ecosystem services to which they contribute. This study focuses on the role of arable weeds in supporting invertebrate populations and selected ecosystem services they deliver., using winter wheat as a case study. Weed-invertebrate relationships were investigated across seven studies of winter-sown wheat spanning 18 years. Both phytophagous and predatory invertebrates responded to weed cover but to different degrees. Phytophages showed a stronger positive relationship with weed cover than the predators, because they rely on the resources provided by the weeds whereas predatory species response is likely to be mediated by their prey. Farmland bird chick-food indices were positively related to both broadleaf and grass cover in cropped fields, indicating that increased weed cover can provide increased invertebrate food for birds in winter wheat. Despite this potential, there were insufficient invertebrate food resources for birds in the majority of wheat fields sampled. Weed diversity did not play a significant role in moderating the relationships between weeds and invertebrate abundance, however this may be a function of the low weed diversity in modern winter wheat fields. In this study the weed species most frequently shown to predict the invertebrate community were:

Further evidence for a global decline of the entomofauna

“…2019; Smith et al . 2020). The development and implementation of effective insect conservation programs is challenging (Samways 2007; Samways et al .…”

An ecological future for weed science to sustain crop production and the environment. A review

“…As such, completely weed-free fields are an unrealistic goal: weeds will always arrive in farm fields through natural dispersal and dormancy processes, and resource availability and incomplete biotic resistance will always permit some weed establishment. This raises the question of whether it is possible to manage the composition and diversity of weed communities to increase their positive contributions to agroecosystem productivity and sustainability relative to their negative effects on crop growth (Storkey and Westbury 2007;Smith et al 2020).…”

“…Weeds and their management are critical to achieving agriculture's potential in both these roles. Uncontrolled, weeds could reduce global yields of major crops by around 34% (Oerke 2006), yet when too many weeds are removed from farmed landscapes, major declines in other wildlife follow (Marshall et al 2003;Bretagnolle and Gaba 2015;Smith et al 2020). Current agricultural systems, particularly in the developed world, are dominated by a paradigm of largescale, intensive, mechanised farming of a few major crops supported by inputs of mineral fertilisers and chemical crop protection products (Stoate et al 2001).…”

Crop Diversification for Improved Weed Management: A Review

“…However, the objective of the diversification strategies is not to eliminate all the weeds, instead to control them. Weeds offer various ecosystem services, which sometimes are beneficial to crops and humans [42][43][44][45][46][47].…”