Data from: Trophic interactions regulate peatland carbon cycling

Peatlands are the most efficient natural ecosystems for long-term storage of atmospheric carbon. Our understanding of peatland carbon cycling is based entirely on bottom-up controls regulated by low nutrient availability. Recent studies have shown that top-down controls through predator-prey dynamics can influence ecosystem function, yet this has not been evaluated in peatlands to date. Here, we used a combination of nutrient enrichment and trophic-level manipulation to test the hypothesis that interactions between nutrient availability (bottom-up) and predation (top-down) influence peatland carbon fluxes. Elevated nutrients stimulated bacterial biomass and organic matter decomposition. In the absence of top-down regulation, carbon dioxide (CO2) respiration driven by greater decomposition was offset by elevated algal productivity. Herbivores accelerated CO2 emissions by removing algal biomass, while predators indirectly reduced CO2 emissions by muting herbivory in a trophic cascade. This study demonstrates that trophic interactions can mitigate CO2 emissions associated with elevated nutrient levels in northern peatlands.

泥炭地（Peatlands）是长期封存大气碳的效率最高的自然生态系统。此前学界对泥炭地碳循环的认知，完全基于低养分有效性调控的上行控制（bottom-up control）机制。近期研究表明，基于捕食者-猎物动态的下行控制（top-down control）可影响生态系统功能，但截至目前该效应尚未在泥炭地中得到验证。本研究通过养分添加与营养级操纵相结合的实验手段，验证了“养分有效性（上行控制）与捕食作用（下行控制）的交互作用会影响泥炭地碳通量”这一假说。养分富集可促进细菌生物量提升与有机质分解过程。在无下行调控的情况下，分解作用增强所驱动的二氧化碳（CO₂）呼吸排放，会被藻类生产力提升所抵消。植食动物通过移除藻类生物量加速了二氧化碳排放，而捕食者则通过营养级联效应抑制植食作用，间接降低了二氧化碳排放。本研究证实，营养级交互作用可缓解北方泥炭地中养分富集所引发的二氧化碳排放。