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: 2021
• 资助国家: 加拿大
• 起止时间: 2021-01-01 至 2022-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=741244
• 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.

氮是植物生长的关键土壤养分。因此，全面了解影响氮素有效性的因素对于预测植物对环境变化的反应至关重要。冬季条件变化导致的土壤冻结变化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利用率和吸收量。然而，一个重要的问题是土壤氮对严重冰冻事件的反应是否可以长期持续。尽管因冰冻而破坏的土壤微生物和植物根系种群可以在明年恢复，但冰冻驱动的不同多年生植物物种的类型和丰度变化可能对土壤氮产生持久影响，因为不同物种分解的植物材料的氮含量不同。豆类是可以通过与特殊细菌合作直接从空气中获取氮的植物，可能比其他植物物种对冷冻更敏感。鉴于豆科植物的分解可以大幅增加土壤氮，因此冬季变化导致豆科植物数量的变化可能会对土壤肥力产生强烈影响。鉴于温暖的冬季导致积雪减少，这会增加在土壤中越冬的植物的冻结，因此对该主题的研究特别及时和重要。 我的研究计划的首要目标是解决豆类抗冻性的限制如何影响冬季过程控制天然植物群落（例如草地）和管理生态系统（农田）中土壤氮可用性的程度。通过在受控生长条件下和在田间进行的实验相结合，我将检验一个新的假设，即相对于非豆科植物，增加的冷冻强度会不成比例地降低豆科植物的存活和生长。然后，我将使用更大规模、多年的田间实验与氮示踪技术相结合，研究对豆科植物的致命或亚致死冷冻损害如何影响随后植物生长季节的氮可用性的数量和时间。除了提供有关自然环境土壤肥力随天气和气候变化变化而变化的重要知识外，这项研究还将为豆类在应用场景中的有效利用做出重大贡献，例如农业覆盖作物混合物和用于恢复本土植物群落的物种选择。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，但我的研究将集中在北温带地区的植物，其中包括加拿大人口最多和农业最多的地区。