CAREER: The end of winter: How changing snow conditions affect soil redox and biogeochemistry

冬天的变化比其他季节都快。曾经在冬季有固定积雪覆盖的地区现在经历了温暖期和可能导致雪融化的雨雪事件。没有持续的积雪覆盖，土壤将不再与冰冻温度绝缘，也不会在冬季受到水的保护。大多数研究都集中在植物生长的夏季土壤上，所以人们对冬季条件的变化如何影响土壤分解、温室气体排放和养分输出等过程知之甚少。这项研究使用了一个将融化雪的实验，以及沿着新罕布什尔州山脉的积雪梯度观察，以了解积雪的变化如何影响土壤过程。本项目提供冬季生态学、实验和数据分析的研究生和本科生教育。该项目还涉及社区成员，包括公立学校的学生，以帮助监测新罕布什尔州山区的积雪和土壤状况，并帮助公众更多地了解冬季变化对其社区的影响。持续积雪的消失增加了土壤气候的变化，因为融雪会周期性地提高土壤水分水平，使土壤容易受到偶发性冻结的影响。最近对山地森林土壤的测量表明，这种冬季变化正在引起氧化还原波动。氧化还原波动的增加将对土壤生物地球化学产生深远影响，对温室气体产生影响，如N2O通量增加和CH4吸收减少，并可能增加向水生系统的养分输出。本研究将1)构建一个新的原位实验，通过三种处理来操纵冬季气候：50%的降雪融化，100%的降雪融化，以及不操纵雪的对照；2)使用雪况的自然梯度作为未来时间的空间替代。在实验中，在整个梯度中，将测量土壤环境变量（温度、湿度、霜深、O2和氧化还原电位）和生物地球化学通量，包括温室气体产生（CO2、N2O、CH4）以及通过土壤剖面的碳、养分和金属的浸出。这项研究将产生所需的知识，以填补隆冬融雪如何通过湿度、温度和氧化还原的变化影响土壤生物地球化学的空白，并量化这种雪的损失如何影响土壤。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Winter is changing faster than other seasons. Regions that once had regular snow cover during winter now experience warm spells and rain-on-snow events that can cause snow to melt. Without consistent snow cover, soils will no longer be insulated from freezing temperatures or protected from water during the winter. Most research has focused on soils during the summer season when plants are growing, so little is known about how changes in winter conditions will affect soil processes like decomposition, greenhouse gas emissions, and nutrient export. This research uses an experiment that will melt snow, along with observations along a snow-cover gradient in the New Hampshire mountains, to understand how changes in snow cover will affect soil processes. This project provides graduate and undergraduate education in winter ecology, experiments, and data analysis. This project also involves community members, including public school students, to help monitor snow and soil conditions in the New Hampshire mountains and to help the public learn more about the effects of changes in winter on their communities.The loss of a persistent snowpack is increasing soil climate variability as snowmelt periodically raises soil moisture levels and leaves the soil vulnerable to episodic freezing. Recent measurements in upland forest soils indicate this winter variability is causing redox fluctuations. Increased redox fluctuations will have profound effects on soil biogeochemistry with implications for greenhouse gases, such as increased N2O fluxes and reduced CH4 uptake, and may increase nutrient exports to aquatic systems. This research will 1) construct a novel in situ experiment that manipulates winter climate with three treatments: melting 50% of snowfall, melting 100% of snowfall, and a control, where snow is not manipulated; and 2) use a natural gradient of snow conditions as a space-for-future-time substitution. Within the experiment and across the gradient, soil environmental variables (temperature, moisture, frost depth, O2, and redox potential), and biogeochemical fluxes, including greenhouse gas production (CO2, N2O, CH4) and the leaching of carbon, nutrients, and metals through the soil profile, will be measured. This research will generate the knowledge needed to fill the unaddressed gap of how midwinter snowmelt affects soil biogeochemistry through changes to moisture, temperature, and redox and quantify how this loss of snow affects soil.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.