Winter as a driver of nitrogen cycle responses to environmental change: responses of leguminous plants to variability in freezing

冬季作为氮循环对环境变化反应的驱动因素：豆科植物对冰冻变化的反应

• 批准号: RGPIN-2020-06486
• 负责人: Henry, Hugh
• 金额: $ 3.42万
• 依托单位: University of Western Ontario
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=745740
• 关键词: Winter; driver; nitrogen; cycle; responses

Nitrogen is a key soil nutrient for plant growth. Therefore, a thorough understanding of the factors that affect nitrogen availability is crucial for predicting plant responses to environmental variation. Changes in soil freezing resulting from variation in winter conditions can have a substantial influence on the activities of soil microbes and plant roots, and thus can alter nitrogen availability and uptake by plants over the following growing season. However, an important question is whether soil nitrogen responses to severe freezing events can persist over the longer term. Although populations of soil microbes and plant root systems disrupted by freezing can recover by the next year, freezing-driven changes in the types and abundances of different perennial plant species could have lasting effects on soil nitrogen, because the nitrogen content of decomposing plant material differs among species. Legumes, which are plants that can obtain nitrogen directly from the air by partnering with specialized bacteria, may be more sensitive to freezing than other plant species. Given that the decomposition of legumes can increase soil nitrogen substantially, changes in legume numbers in response to changing winters could have strong effects on soil fertility. Research on this topic is particularly timely and important given that warmer winters are resulting in decreased snow cover, which can increase the freezing of plants that overwinter in soil. The overarching objective of my research program is to address how limits to the freezing tolerances of legumes can influence the extent to which winter processes control soil nitrogen availability both in natural plant communities (e.g. grassland) and managed ecosystems (cropland). Using a combination of experiments under controlled growth conditions and in the field, I will test the novel hypothesis that increased freezing intensity reduces the survival and growth of legumes disproportionately relative to non-leguminous plants. I will then use larger scale, multi-year field experiments in combination with nitrogen tracer techniques to examine how lethal or sublethal freezing damage to legumes affect the amount and timing of nitrogen availability over subsequent plant growing seasons. In addition to providing important knowledge regarding changes in the soil fertility of natural environments in response to variation in weather and climate change, this research will contribute significantly to the effective use of legumes in applied scenarios, such as in agricultural cover crop mixtures and in the selection of species for the restoration of native plant communities. Although winter biology has been explored most extensively in alpine and arctic systems, my research will focus on plants in northern temperate regions, which include the most highly populated and agricultural regions of Canada.

氮素是植物生长的关键土壤养分。因此，深入了解影响氮素利用率的因素对于预测植物对环境变化的反应至关重要。冬季条件变化引起的土壤冻结变化可能会对土壤微生物和植物根系的活动产生重大影响，从而改变植物在接下来的生长季节的氮素有效性和吸收。然而，一个重要的问题是，土壤氮对严重冰冻事件的反应能否持续更长时间。虽然被冰冻破坏的土壤微生物和植物根系的种群可以在第二年恢复，但不同多年生植物种类和丰度在冰冻驱动下的变化可能会对土壤氮产生持久的影响，因为不同物种分解植物材料的含氮量不同。豆类是一种植物，可以通过与特殊细菌合作直接从空气中获取氮，可能比其他植物物种对冷冻更敏感。鉴于豆类的分解可以大幅增加土壤氮素，豆类数量因冬季变化而发生的变化可能会对土壤肥力产生很大影响。鉴于冬季变暖导致积雪减少，这可能会增加在土壤中越冬的植物的结冰，因此对这一主题的研究尤为及时和重要。我的研究计划的首要目标是解决豆类植物耐寒性的限制如何影响冬季过程控制土壤氮素有效性的程度，无论是在自然植物群落(例如草原)还是在受管理的生态系统(农田)中。通过在受控生长条件下和田间试验的结合，我将检验这一新的假设，即与非豆科植物相比，增加冰冻强度会不成比例地降低豆类植物的存活和生长。然后，我将使用更大规模的多年田间试验，结合氮素示踪技术，研究对豆类的致命或亚致命冻害如何影响随后植物生长季节的氮素有效性和时间。除了提供关于自然环境土壤肥力随天气和气候变化变化的重要知识外，这项研究还将大大有助于豆类在应用场景中的有效利用，例如在农业覆盖作物混合中以及在选择物种以恢复本地植物群落方面。尽管冬季生物学在高山和北极系统中得到了最广泛的探索，但我的研究重点将放在北部温带地区的植物上，其中包括加拿大人口最稠密和农业地区。