Weed Seed Bank Diversity in Dryland Cereal Fields: Does it Differ Along the Field and Between Fields with Different Landscape Structure?

Yesica Pallavicini,Eva Hernandez Plaza,Jose L Gonzalez-Andujar,Fernando Bastida,Jordi Izquierdo,Montserrat Gallart

doi:10.3390/agronomy10040575

Yesica Pallavicini, Eva Hernandez Plaza + Show 4 more

Open Access

https://doi.org/10.3390/agronomy10040575

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Abstract

In this work, we aimed to test whether taxonomic diversity and functional diversity and the values of functional traits of the weed seed bank varied across the field, from margins to the core, and between fields embedded in distinct landscape structures. We sampled the seed bank of 47 conventionally managed cereal fields from two Mediterranean regions in Spain. In each field, three positions were selected: Margin, edge and core, and soil properties were measured for each position. Landscape structure was quantified for each field as the percentage of arable land in the surrounding 1 km radius circular sector. Seed bank diversity was characterized at the taxonomic (species richness, exponential Shannon index, and evenness) and functional levels (Rao’s quadratic entropy index and four corner analysis). For functional diversity, eight functional traits related to the whole plant life cycle were considered. Results showed a slight response of increasing taxonomic diversity from the core of the fields to the margins. Functional diversity was extremely low, indicating high similarity among species in terms of functional traits. Species in the seed bank were mostly therophytes, shorter than the crop plants, small seeded, flowering between the herbicide application of late winter and crop harvest, and showed seed dispersal by gravity or wind. This trait syndrome allows persistence in intensively managed arable lands. The similarity between fields in terms of functional diversity of the seed bank and in species traits may suggest that the intensity of management practices was similar across the fields. Moreover, it emphasizes that an increase in landscape heterogeneity, if based on other intensively managed cropping systems, may not be sufficient to augment functional diversity of weed communities. Therefore, in these areas, the seed bank could restore weed taxonomic diversity following changes in management practices, but functional diversity would still remain limited.

Highlights

A dramatic diversity loss in arable systems has resulted from agriculture intensification in recent decades
We aimed to test whether taxonomic diversity, functional diversity, and the values of functional traits of the weed seed bank varied along the field, from margins to the center, and between fields embedded in distinct landscape structures
As we looked at the weed species pool available for recruitment, our experimental approach was intended to quantify the germinating component of the seed bank, i.e., the portion of soil-stored seeds able to germinate along the current crop season

Summary

Introduction

A dramatic diversity loss in arable systems has resulted from agriculture intensification in recent decades. The soil seed bank can function as a reservoir of weed diversity that can serve to restore above-ground diversity in intensively managed agroecosystems As such, it has been considered indicative of the sustainability of a cropping system [1]. Agronomy 2020, 10, 575 weed seeds from the present and the previous years and, represents a synthesis of the management practices and the environmental conditions that a field has been subjected to during the years [2] In this manner, a low diverse weed seed bank, in terms of the number of species, may result from a continuous management regime that has filtered out species. In the case of the seed bank, this pattern could be more accentuated, which could support the idea that field edges and margins are effective refuges for declining weed species [5,7]

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