Short-term asynchrony of root and shoot growth links to soil carbon flux dynamics

Root dynamics and allocation belowground are a major uncertainty in ecosystem studies because roots are hard to measure in comparison to leaves, which can be assessed at fine timescales using a variety of remote sensing approaches. We built an automated minirhizotron system capable of taking root images on a sub-daily scale and analyzed all high frequency images from this with a neural network approach. We pair this with a daily series of above-ground vegetation indexes of the same plants from standardized ‘phenocam’ digital camera methods. Here we will demonstrate, from a mesocosm experiment that 1) in a mixed species mesocosm, root and shoot production (i.e. rate of change of indexes) as not synchronized on short (multi-day) timescales and 2) root growth rate was more important than overall biomass and leaf growth rate in determining variability in soil CO₂ efflux. Hence this efflux was likely driven by root growth respiration rather than maintenance respiration. We also show the first results from applying similar principles to ecosystem measurements.