Weeds are key components of agroecosystems because they support biological diversity within crop fields. Ecological indicators of weed diversity are usually assessed on a field scale, but weeds are distributed unevenly within fields. Here, we explore spatial distribution of diversity in weed seed banks, and how a failure of grass weed control may affect biodiversity indicators. We studied spatial distribution and stability of species richness, Shannon’s diversity index, and Pielou’s evenness index of a weed seed bank, site-specifically and for the entire field, over three years in a commercial winter wheat field regularly treated with narrow- and broad-leaved herbicides. 254 soil samples were taken on 10 m × 10 m grids at the beginning of each season. Seeds were identified by germination in a greenhouse and indices were assessed for each point. The spatial structure of the indices was described by spherical isotropic semivariograms. Our findings show that diversity and evenness computed for the entire field both decreased by 63% after lack of grass weed control, and increased 32% and 31%, respectively, the following year. However, richness, diversity and evenness were not homogeneous across the field. Diversity and evenness became increasingly patchy over time, as shown by a spatial dependence increasing by 21% and 40%, respectively, after two years. This finding is related to the reduction in the patch extension of broad-leaved species due to broad-leaved herbicide application each year and the expansion of grass patches due to the lack of grass control in the first year. Spatial location of patches was not stable over time. Nevertheless, weedy areas remained on the field and represent plant diversity caches that may contribute to maintaining global biodiversity. This information is missed if a single biodiversity index is computed for the entire field. Knowledge of spatial distribution of weed diversity within a field will be useful for identifying wildlife conservation areas and understanding changes in biodiversity in cropland ecosystems better.

中文翻译：

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谷物田杂草多样性的空间分布

杂草是农业生态系统的关键组成部分，因为它们支持作物田间的生物多样性。杂草多样性的生态指标通常在田间评估，但杂草在田间分布不均。在这里，我们探讨了杂草种子库中多样性的空间分布，以及草杂草控制失败如何影响生物多样性指标。我们研究了在商业化冬小麦田中三年定期进行窄幅和宽幅处理的杂草种子库的物种丰富度，香农的多样性指数和杂草的均匀度指数的空间分布和稳定性，以及针对整个田地的分布。阔叶除草剂。每个季节开始时，在10 m×10 m的网格上采集254个土壤样品。通过在温室中发芽鉴定种子，并评估每个点的指数。指数的空间结构由球面各向同性半变异函数描述。我们的发现表明，在缺乏草类杂草控制之后，整个田间的多样性和均匀度均下降了63％，第二年分别增加了32％和31％。但是，整个领域的丰富性，多样性和均匀性并不相同。随着时间的流逝，多样性和均匀性变得越来越斑驳，两年后的空间依赖性分别增加了21％和40％。这一发现与每年因使用阔叶除草剂而减少阔叶树种的斑块扩展以及由于第一年缺乏对草的控制导致草斑的扩展有关。补丁的空间位置随着时间的推移而不稳定。不过，田间仍保留有杂草，它们代表着可能有助于维持全球生物多样性的植物多样性贮藏室。如果为整个田地计算单个生物多样性指数，则会丢失此信息。田间杂草多样性的空间分布知识将有助于确定野生动植物保护区并更好地了解农田生态系统中生物多样性的变化。