What good is weed diversity?

J Storkey,P Neve,Matt Liebman

doi:10.1111/wre.12310

Abstract

SummaryShould the declining diversity of weed communities in conventionally managed arable fields be regarded as a problem? The answer to this question has tended to divide researchers into those whose primary focus is on conserving farmland biodiversity and those whose goals are dictated by weed control and maximising yield. Here, we argue that, regardless of how weeds are perceived, there are common ecological principles that should underpin any approach to managing weed communities, and, based on these principles, increasing in‐field weed diversity could be advantageous agronomically as well as environmentally. We hypothesise that a more diverse weed community will be less competitive, less prone to dominance by highly adapted, herbicide‐resistant species and that the diversity of the weed seedbank will be indicative of the overall sustainability of the cropping system. Common to these hypotheses is the idea that the intensification of agriculture has been accompanied by a homogenisation of cropping systems and landscapes, accounting for both declines in weed diversity and the reduced resilience of cropping systems (including the build‐up of herbicide resistance). As such, weed communities represent a useful indicator of the success of rediversifying systems at multiple scales, which will be a central component of making agriculture and weed control more sustainable.

Highlights

The number of weed species that are typically found in conventionally managed crop fields is a fraction of the levels recorded in the 1950-1970s, owing to increased fertiliser and herbicide use, simpler rotations and loss of field boundaries and semi-natural features in the landscape (Andreasen et al, 1996; Fried et al, 2009; Meyer et al, 2013)
This loss of infield biodiversity is a concern, reflecting an erosion of the natural capital and ecosystem services on which sustainable production is founded. For others, it is seen as a measure of successful weed control and the concept of conserving weeds within cropped fields is, at best, incomprehensible and, at worst, an insult to the efforts of weed scientists over the past half-century to reduce the serious yield losses inflicted by weeds (Oerke, 2006)
The focus here is on weed species richness and evenness, not density or total biomass

Summary

Should the declining diversity of weed communities in conventionally managed arable fields be regarded as a problem? The answer to this question has tended to divide researchers into those whose primary focus is on conserving farmland biodiversity and those whose goals are dictated by weed control and maximising yield. Should the declining diversity of weed communities in conventionally managed arable fields be regarded as a problem? We hypothesise that a more diverse weed community will be less competitive, less prone to dominance by highly adapted, herbicideresistant species and that the diversity of the weed seedbank will be indicative of the overall sustainability of the cropping system. Common to these hypotheses is the idea that the intensification of agriculture has been accompanied by a homogenisation of cropping systems and landscapes, accounting for both declines in weed diversity and the reduced resilience of cropping systems (including the build-up of herbicide resistance).

Introduction

Number of weed species recorded