EAGER: Assessing the role of trophic interactions on peatland carbon cycling under varied nutrient availability

极北地区的泥炭地在其寒冷（有时是冰冻的）和潮湿的土壤中储存了大量的碳。虽然寒冷潮湿的环境显然很重要，但导致这些生态系统中积累如此多泥炭的生物因素并不完全清楚。该项目将研究如何在富矿溪长期生态研究网站泥炭碳循环的变化与营养的可用性。 研究人员将进行实验，以测试有关藻类以及藻类生产所支持的昆虫和无脊椎动物食物网对泥炭地碳积累的重要性的假设。食物网是泥炭地生态学知之甚少的一个方面，更好地了解是什么控制了其中的生物相互作用，将对理解全球碳循环产生深远的影响。除了在生态系统科学中绘制新的概念基础，该项目将支持两个早期的职业研究人员，涉及来自代表性不足的群体的本科生，并培训两名研究生。这个早期概念探索性研究资助（EAGER）项目挑战的概念，即北方泥炭地食物网内的能量流仅限于碎屑途径。通过碳补贴的贡献，并通过修改异养微生物的氧化还原电位，研究人员提出，藻类光合作用燃料的微生物循环，并有助于生态系统的碳和氮通量。该研究将评估自下而上与自上而下的影响（及其相互作用）对北方泥炭地食物网的相对重要性，使用析因实验来测试三个假设：1）在低养分可用性下，藻类生物量受到限制，分解主要受碎屑途径调节。2)增加养分供应促进藻类生物量和能量向食草动物的转移，从而从资源限制中释放出更高的营养水平。3)藻类中第二种能量途径的存在（可食用与不可食用）使营养级联静音，导致更大的稳定性（即，较低的变异系数）的食物网结构比预期的强自上而下的控制同质食用社区。

Peatlands in the far north store a very large amount of carbon in their cold (sometimes frozen) and wet soils. While the cold, wet environment is clearly important, the biological factors that cause so much peat to accumulate in these ecosystems are not entirely understood. This project will study how changes in peat carbon cycling at the Bonanza Creek Long-Term Ecological Research site vary with nutrient availability. Researchers will conduct experiments to test hypotheses concerning the importance of algae and the food web of insects and invertebrates that algal production supports, to accumulation of carbon in peatlands. Food webs are a poorly know aspect of peatland ecology, and a better understanding of what controls biotic interactions within them will have profound implications for understanding the global carbon cycle. In addition to charting new conceptual ground in ecosystem science, this project will support two early career researchers, involve undergraduate students from under-represented groups, and train two graduate students.This Early-concept Grant for Exploratory Research (EAGER) project challenges the notion that energy flow within the food web of boreal peatlands is limited to detrital pathways. Through a contribution of carbon subsidies and by modifying redox potential for heterotrophic microorganisms, the investigators propose that algal photosynthesis fuels a microbial loop and contributes to ecosystem carbon and nitrogen fluxes. The research will evaluate the relative importance of bottom-up versus top-down effects (and their interactions) on boreal peatland food webs using a factorial experiment to test three hypotheses: 1) Under low nutrient availability, algal biomass is constrained and decomposition is primarily regulated by detrital pathways. 2) Increasing nutrient availability promotes algal biomass and the transfer of energy to grazers, releasing higher trophic levels from resource limitation. 3) The presence of a second energy pathway in algae (edible vs. inedible) mutes the trophic cascade, leading to greater stability (i.e., lower coefficients of variance) in food web structure than would be expected with strong top-down control of a homogenous edible community.