DISSERTATION RESEARCH: Do accelerated microbial - organic matter interactions feed back to promote shrub growth in arctic tundra?

北极拥有陆地生态系统中最大的土壤碳库。随着气候变暖，了解这个碳库的变化变得越来越重要。土壤释放的碳将增加大气中二氧化碳的浓度，而土壤碳库的增加将从大气中消除二氧化碳。更高的气温已经引发了巨大的木本灌木在北极苔原上的广泛扩张，并似乎刺激了土壤碳的流失。这项研究考察灌木是否改变了微生物群落的组成，从而对灌木的生长产生了积极的影响。这些信息对于理解灌木如何影响北极植物和土壤的碳库至关重要。利用阿拉斯加的北极土壤，研究人员将建立一个植物生长实验，以确定灌木对不同土壤微生物和养分处理的反应。通过在一个实验中调查植物、土壤和微生物，这项工作将提高北极碳动态模型的准确性。此外，这项工作将培训本科生在现场和实验室的研究技能，并提供实践的科学经验。通过研究人员和佐治亚州当地教师的合作，这项研究的结果也将被整合到小学、初中和高中学生的教学计划中。这些研究人员之前的研究表明，灌木促进了一个更活跃、营养限制更少的微生物群落，这可能会导致灌木土壤中的碳损失。这些发现表明，灌木刺激土壤微生物活动是改善养分有效性的一种机制，但尚不清楚灌木诱导的微生物群落变化是否有利于灌木的生长。利用北极土壤，研究人员将使用完全析因设计，将土壤微生物来源(灌木和非灌木)与氮(+/-)和磷(+/-)交叉，并对三种灌木(Alnus ruticosa、Betula nana和Salix Pulchra)进行无菌对照。收集的数据将包括植物生物量、根共生体的量化和土壤微生物生物量。这些数据将被用来理解灌木-微生物关系的大小和方向，以及由微生物活动引起的碳损失是否可以通过灌木的碳收益来抵消。

The arctic holds the largest pool of soil carbon across land ecosystems. As the climate warms, changes to this carbon pool become increasingly important to understand. Carbon release from soils would increase concentrations of carbon dioxide in the atmosphere, while increases in soil carbon pools would remove carbon dioxide from the atmosphere. Higher temperatures have already trigged widespread expansion of large, woody shrubs across arctic tundra, and appear to stimulate the loss of soil carbon. This research examines whether shrubs change the composition of microbial communities in a way that positively impacts the shrub growth. This information is critical to understanding how shrubs affect carbon pools of plants and soils in the arctic. Using arctic soils from Alaska, the investigators will establish a plant growth experiment to determine how shrubs respond to different treatments of soil microbes and nutrients. By investigating plants, soils, and microbes in one experiment, this work will improve the accuracy of models of arctic carbon dynamics. In addition, this work will train undergraduates in both field and laboratory research skills and provide hands-on scientific experience. The results of this research will also be integrated into lesson plans for elementary, middle, and high school students through a collaboration between the researchers and local Georgia teachers. Previous research by these investigators demonstrates that shrubs promote a more active and less nutrient limited microbial community, which may lead to carbon loss from shrub soils. These findings suggest that shrubs stimulate soil microbial activity as a mechanism to improve nutrient availability, but it is unclear if shrub-induced changes to microbial communities benefit shrub growth. Using arctic soils, the researchers will establish a plant growth experiment using a fully factorial design crossing soil microbial source (shrub vs non-shrub) by nitrogen (+/-) and phosphorus (+/-) with a sterile control for three species of shrubs (Alnus fruticosa, Betula nana, and Salix pulchra). Collected data will include plant biomass, quantification of root symbioses, and soil microbial biomass. These data will be used to understand the magnitude and direction of shrub-microbial relationships and if carbon loss induced by microbial activity can be counterbalance by shrub carbon gain.