The influence of trigger events on bursts of soil microbial metabolism and N2O production and consumption

气候驱动土壤中发生的生物过程，但在农业氮素管理中，气候描述得很少，也很少被考虑。这是由于土壤氮循环过程的数量和复杂性。在这个建议中，我们研究的作用，气候触发器（解冻的冻土和湿润的干燥土壤）刺激爆发的微生物活动，造成土壤氮素损失。具体来说，这项工作的重点是对无机氮过程，控制硝化和反硝化的时间和相对重要性，在生产N2 O排放的影响基板可用性。我的假设是，环境事件触发微生物代谢，通过释放底物作为微生物细胞裂解和溶解土壤有机质的结果。此外，微生物代谢作用于这些基质的速率，受土壤温度和含水量的影响，以及碳和氮分布的结构，决定了反硝化作用的位置，强度和产物，因此N2 O排放量。我的研究目标是了解气候和气候变化对土壤氮转化和氮损失的影响。本提案的具体目标是：首先（PhD 1）研究在受控环境条件下，由于解冻和湿润触发而导致N2 O爆发的机制;其次（PhD 2）研究在田间条件下，由于解冻和湿润触发而导致土壤剖面中N2 O的产生和消耗。这项研究利用了最近的技术发展，允许高频测量的同位素组成的N2 O排放量，以确定在触发事件的N2 O的来源。N2 O生产的测量将与土壤水分和温度的连续测量相结合，以提供触发事件的物理效应如何转化为微生物代谢变化的动态图像。* 这项研究的创新之处在于，它使用N2 O浓度和同位素组成的高频测量来研究与环境事件相关的微生物代谢的性质。使用15 N的N2 O的网站偏好将区分硝化和反硝化作为N2 O的来源，在这些事件以及N2 O的消耗反硝化。* 这项研究将深入了解气候变化对土壤微生物过程的潜在影响。更好地了解农业管理如何影响与解冻和湿润事件相关的N2 O排放。这对于制定战略以维持土壤肥力、减少农业温室气体排放、减少对水质的影响以及提高农业的盈利能力和可持续性十分重要。

Climate drives the biological processes occurring in soil yet is a poorly described and seldom considered part of nitrogen management in agriculture. This is due to the number and complexity of processes involved in the soil N cycle. In this proposal we examine the role of climatic triggers (thawing of frozen soil and wetting of dry soil) in stimulating bursts of microbial activity and causing soil N losses. Specifically this work focuses on the influence substrate availability on inorganic nitrogen processes that control the timing and relative importance of nitrification and denitrification in producing N2O emissions. My hypothesis is that environmental events trigger microbial metabolism through the release of substrates as a result of microbial cell-lysis and solubilization of soil organic matter. Further, it is the rate at which microbial metabolism acts on these substrates, as influenced by soil temperature and water content, and the architecture of carbon and nitrogen distribution which determines the location, intensity, and products of denitrification and therefore N2O emissions.***The goal of my research is to understand the impacts of climate and climate change on soil N transformations and nitrogen losses. The specific objective of this proposal is firstly (PhD1) to examine the mechanisms resulting in N2O bursts in response to thawing and wetting triggers under controlled environment conditions and secondly (PhD 2) to examine the production and consumption of N2O in soil profiles in response to thawing and wetting triggers under field conditions.***This research takes advantage of recent technological developments that allow high frequency measurement of the isotopomeric composition of N2O emissions to determine the source of N2O during trigger events. Measurements of N2O production will be coupled with continuous measurement of soil water and temperature to provide a dynamic picture of how the physical effects of trigger events are translated into shifts in microbial metabolism. ***This research is innovative in that it uses high frequency measurement of concentration and isotopomeric composition of N2O to study the nature of microbial metabolism associated with environmental events. The use of 15N site preference of N2O will distinguish between nitrification and denitrification as sources of N2O during these events as well as the consumption of N2O by denitrification. ***This research will provide insight into the potential impacts of climate change on soil microbial processes. A better understanding of how agricultural management impacts N2O emissions associated with thawing and wetting events. This is important for developing strategies to sustain soil fertility and reduce greenhouse gas emissions from agriculture, reduce impacts on water quality and increase the profitability and sustainability of agriculture.