The Arctic is warming four-times faster than the global average. This causes increased CO2 emissions from thawing permafrost soils that add to anthropogenic emissions, but also increased plant CO2 uptake under conditions more favorable for plant growth. The balance between these processes determines the future Arctic CO2 budget. In addition, plants can stimulate CO2 emissions from soils near their roots, via the rhizosphere priming effect. The intensity of priming is likely influenced by increasing plant productivity, deeper plant rooting favored by permafrost thaw, as well as changes in vegetation distribution such as northward-movement of the tree line, which can all already be observed across the Arctic.
PRIMETIME aims to provide the first observation-based estimate of total plant effects on circum-Arctic soil and ecosystem carbon stocks in a changing climate. Central questions include:
(1) How do different vegetation types affect soil and ecosystem carbon stocks and CO2 balance?
(2) How do changes in rooting depth interact with depth gradients of soil properties to affect carbon stocks and CO2 fluxes?
(3) What is the net effect of expected changes in plant productivity, vegetation distribution and rooting on ecosystem carbon storage across the circum-Arctic?