Plant functional diversity is affected by weed management through processes of trait convergence and divergence

Abstract

Weed management involving tillage and/or herbicides has generally led to a decline of plant diversity in agroecosystems, with negative impacts on ecosystem services provision. The use of plant covers has become the predominant alternative in vineyard management, with numerous studies focusing on analyzing the advantages and disadvantages of plant covers compared to the aforementioned management. Although the impacts of weed management on taxonomic diversity have been widely studied, many gaps remain on their effects on plant functional diversity. As plant functional diversity is linked to the delivery of key ecosystem services in agroecosystems, understanding these effects could enable the development of more sustainable practices. From 2008 to 2018, a long-term trial was carried out in a Mediterranean vineyard to assess different agricultural practices. In this article, we examined how weed management, as well as irrigation use, could affect plant functional diversity. Based on 10 functional traits, such as plant height, specific leaf area or seed mass, we measured different indices of functional diversity and used null models to detect processes of trait convergence and divergence. Our results revealed that weed management and irrigation use had a significant effect on plant functional diversity. Mown plots showed the highest functional richness but were functionally convergent, since mowing was a strong functional filter on most of the traits. Tillage also behaved as a functional filter on some vegetative traits, but favored the divergence of certain reproductive traits. Herbicide-treated and irrigated plots showed the highest values of functional divergence by promoting more competitive species with more divergent trait values. The effect of weed management on these community assembly processes was shaped by the use of irrigation in vineyard rows, leading to functional divergence in those vegetative traits related to resource acquisition and seed mass. These results suggest that greater functional diversity may be associated with the bias caused by higher occurrence of competitive species (e.g. Convolvulus arvensis, Sonchus asper) with contrasting values for certain traits. Therefore, since these species are considered harmful to crops, higher plant functional diversity might not be a desirable indicator in agroecosystems.

Is Diversified Crop Rotation an Effective Non-Chemical Strategy for Protecting Triticale Yield and Weed Diversity?

“…The number of reports on the impacts of agricultural practices on the taxonomic and functional diversities of weeds has been increasing in recent years [37,48,[86][87][88][89]. However, there are still few studies comparable to the present study in terms of the research factors and methods used (e.g., formulas of indexes, weed abundance measures, and selection of functional traits) as various methodological approaches were used by other authors [37,88,89].…”

“…The number of reports on the impacts of agricultural practices on the taxonomic and functional diversities of weeds has been increasing in recent years [37,48,[86][87][88][89]. However, there are still few studies comparable to the present study in terms of the research factors and methods used (e.g., formulas of indexes, weed abundance measures, and selection of functional traits) as various methodological approaches were used by other authors [37,88,89]. A general opinion has been established that agricultural intensification reduces the taxonomic and functional diversities of weed communities [37,90], and herbicide use is among the indicators of this intensification at the individual field scale [37].…”

Identifying Plant Functional Traits of Weeds in Fields Planted with Glyphosate-Tolerant Maize for Preferable Weed Management Practices

“…There is a selection for species with either tolerance (vegetative) [49] or rapid colonisation ability (seeding) [50]. In the case of cropland disturbance, weed species traits enabling weeds to persist after herbicide application would be the most beneficial, but detrimental to the farmer, as they persist and thereby enable a shift in trait composition in the fields [51]. It is for this reason that the herbicide application protocol of this study included non-selective herbicides, to better manage those species often hard to control-especially where mechanical control is not possible.…”