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要快。曾经在冬季有规律积雪的地区现在经历了温暖的时期和雨雪事件，这可能会导致雪融化。如果没有持续的积雪，土壤在冬天将不再免受冰冻温度的影响，也不再受到水的保护。大多数研究都集中在植物生长的夏季土壤上，因此人们对冬季条件的变化将如何影响土壤分解、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融化积雪的实验，并沿着新汉普郡山脉的积雪梯度进行了观察，以了解积雪的变化将如何影响土壤过程。该项目提供冬季生态学、实验和数据分析方面的研究生和本科生教育。该项目还让社区成员，包括公立学校的学生，帮助监测新罕布夏州山区的雪和土壤状况，并帮助公众更多地了解冬季变化对社区的影响。持续积雪的消失增加了土壤气候的变异性，因为积雪融化会定期提高土壤水分水平，使土壤容易受到间歇性冰冻的影响。最近对旱地森林土壤的测量表明，这种冬季的变异性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的影响，并对温室气体产生影响，例如增加N2O通量和减少CH4吸收，并可能增加向水生系统输出的养分。这项研究将1)构建一个新的现场实验，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，以及一个对照，其中雪不被操纵；以及2)使用雪条件的自然梯度作为未来时间的空间替代。在实验范围内和跨越梯度，将测量土壤环境变量(温度、湿度、霜冻深度、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)和碳、养分和金属在土壤剖面中的淋溶。这项研究将产生所需的知识，以填补尚未解决的空白，即仲冬雪融化如何通过水分、温度和氧化还原的变化影响土壤生物地球化学，并量化这种雪的损失如何影响土壤。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.