Weed communities are more diverse, but not more abundant, in dense and complex bocage landscapes

Abstract

Bocage landscapes are characterized by a network of hedgerows that delimits arable fields. Such landscapes provide many ecosystem services, including biodiversity conservation, but their effects on weed communities remain largely unknown. Bocage landscapes could affect weed communities through two main processes: plant spillover from hedgerows and increased environmental heterogeneity in arable fields. These bocage effects are also likely to vary between farming systems (conventional vs. organic) due to differences in management practices. We sampled weed communities more than 20 m from field margins in 74 arable fields (37 per farming system). Fields were located along two independent landscape gradients of total length of hedgerows (with or without a shrub layer) and organic farming cover, in Brittany (France). We analysed the effect of ‘bocage’ (i.e. the density and complexity of hedgerow networks) and farming systems at field and landscape scales on species and functional diversity of weed communities. Further, we used fidelity to non‐crop habitats and Ellenberg indicator values to assess the ‘plant spillover’ and ‘environmental heterogeneity’ hypotheses, respectively. Weed communities were more diverse and more abundant in organic farming systems. In addition, weed communities were more diverse, but not more abundant, in denser and more complex bocage landscapes. ‘Bocage’ increased species diversity of weeds, but also community‐weighted variance of specific leaf area, plant height and seed mass. Positive effects of ‘bocage’ on weed diversity were driven by increased environmental heterogeneity rather than spillover of transient species from hedgerows. ‘Bocage’ effects were independent of farming systems at field and landscape scales. Synthesis and applications. Maintaining diverse weed communities is key to agroecological weed management and biodiversity conservation in agricultural landscapes. Farmers are often concerned that hedgerows harbour competitive plants spreading into field edges, thereby increasing weed pressure. However, our study shows that dense and complex bocage landscapes promote weed diversity in field cores, most likely by increasing environmental heterogeneity. Thus, bocage landscapes could actually enhance ecosystem services provided by weed communities and reduce weed‐crop competition.

Linking Forest Management Practices to the Functional Composition of Plant Communities

“…In addition, different forest types have variations in species composition, which affects the CWM and CWV of the entire plant community. This study contributes to understanding how forest management can influence the FCPC using CWM and CWV, which are closely associated with ecosystem functions and services [6][7][8]27]. We found that plantation forests (rotation ≤ 15 years), planted forests (rotation > 15 years), and agroforestry positively affected the CWM and CWV to an even greater extent than intact for-Figure 3.…”

“…However, the mechanisms underlying the different forest management practices that affect and shape the FCPC are unclear. Forecasting the two major components of functional composition (i.e., communityweighted mean and variance) is essential for ecosystem management to maximize the benefits for society and the environment [6][7][8]. Numerous studies have shown that the plant communities' geographic variation in functional composition can be shaped by environmental factors (e.g., climate, soil, and vegetation), which supports a systematic ecosystem properties and functions assessment that will be used to inform policy or for the design of conservation planning or ecological restoration strategies [1,2,4,6,9].…”

Institutionalization and Legislation of Organic Production in Brazil

“…The vegetative barrier may be used for biodiversity and conservation biological control improvement [52][53][54]. Then, next organic legislation updates could encourage the use of vegetative barriers instead of non-natural barriers, which is usually used as an emergency tactic, but sometimes stays as the definitive tactic as a barrier.…”

Farm management and landscape context shape plant diversity at wetland edges in the Prairie Pothole Region of Canada

“…Introduced plant species are often agricultural weeds or other invasive species, providing a disservice to farmers by competing with crops and requiring control by practices such as tillage or herbicide applications; they also compete with native plant species. However, we acknowledge that, in some circumstances, diverse weed communities can be important for agroecological weed management by reducing weed–crop competition as well as conservation of biodiversity (Boinot et al, 2023). For example, they could provide valuable ecosystem services via their role as refugia for predators of invertebrate pests.…”