Characterizing the recruitment nature of weed species

我的研究项目的核心目标是确定杂草是如何以及为什么会出现的。出苗的时间是植物物种成功的主要决定因素，对于杂草来说，从种子到幼苗的过渡代表了从最不脆弱到最脆弱的生命周期阶段的过渡。杂草出苗的相对时间（相对于作物）和成功也决定了杂草侵扰的竞争力，杂草逃脱管理的可能性，以及形成持久种子库的杂草种子的数量和质量。此外，出现时间是物种地理范围及其入侵潜力的关键决定因素。最后，出现的时间极大地影响了杂草物种（包括逃离农田的作物）在野生或半野生栖息地（包括路边）生存的能力。后者对景观尺度的基因流动和转基因作物与非转基因作物的有效分离具有影响。尽管它在这些方面的根本重要性，我们的理解的机制，出现时间仍然知之甚少，大多数杂草物种。迄今为止，在我的项目中，我们在这一领域做出了一些重大贡献，包括明确证明土壤中的种子深度是出苗时间的一个根本性的重要驱动因素，并且出苗条件的适宜性在很大程度上可以由种子深度决定。我们还表明，开花和种子脱落的时间可以在决定种子经历什么样的条件（包括它们是否被埋葬以及在多大程度上被埋葬）方面发挥非常重要的作用，而这反过来又可以决定出苗的时间。最近，使用加拿大fleabane，一个兼性的冬季一年生杂草（能够出现在一年中的某个时间），我们是第一个记录这些因素（开花和种子脱落的时间，种子深度）的影响的相互作用出现的时间。目前尚不清楚的是，这些观察结果在多大程度上代表了普遍性，在多大程度上影响了后代的种群表现（和杂草），以及这可能如何影响我们管理杂草的能力。我们在未来5年的方法将是展望杂草的生命周期（开花时间和种子脱落），以获得洞察力向后看（出苗和出苗时间）使用兼性冬季一年生杂草作为测试物种。这项研究将有助于更好地了解杂草出现时间的机制，从而为杂草管理、杂草风险评估以及转基因和非转基因作物的有效隔离提供帮助。

The core goal of my research program is to determine how and why weeds emerge when they do. The timing of seedling emergence is a prime determinant of plant species success and for weeds, the transition from seed to seedling represents a transition from the least to the most vulnerable life cycle stage. The relative timing (versus crop plants) and the success of weed seedling emergence also determines the competitiveness of weed infestations, the potential for weeds to escape management, and the quantity and quality of weed seeds left to form persistent seed banks. In addition, emergence timing is a key determinant of the geographic range of species and their invasive potential. Finally, time of emergence greatly impacts the ability of weed species (including crop plants that have escaped farmed fields) to survive in wild or semi-wild habitats including roadsides. The latter has implications for gene flow at the landscape scale and the effective segregation of genetically modified (GM) from non-GM crops. Despite its fundamental importance in these respects, our understanding of the mechanism of emergence timing remains poorly understood for most weed species. To-date in my program we have made some significant contributions in this area including clear demonstration that seed depth in soil is a fundamentally important driver of emergence timing, and that the suitability of emergence conditions can be determined to a great extent by seed depth. We have also shown that timing of flowering and seed shed can play a very significant role in determining what conditions seeds experience (including whether and to what extent they are buried) and that this, in turn, can determine timing of emergence. Most recently, using Canada fleabane, a facultative winter annual weed (able to emerge at an time of the year), we were the first to document an interaction of the effects of these factors (flowering and seed shed timing, and seed depth) on emergence timing. What is not clear is the extent to which these observations represent generalizations and to what extent the effects feed forward to impact population performance (and weediness) in future generations, and how this may influence our ability to manage weeds. Our approach over the next 5 years will be to look forward in the life cycle of weeds (flowering timing and seed shed) in order to gain insight looking backward (to seedling emergence and emergence timing) using facultative winter annual weeds as test species. This research will lead to a better understanding of the mechanisms driving weed emergence timing which in turn will provide insights to aid weed management, weed risk assessments and the effective segregation of GM and non-GM crops.