The fate of TERRestriAl forest CARBon from photosynthesis to structural biomass under climate change

Forests play a major role in the global carbon cycle.

They uptake carbon through photosynthesis, return much of it through respiration, and accumulate some fraction as structural biomass (Bst).

The forest carbon sink offsets nearly 30% of anthropogenic carbon-dioxide emissions, with Bst being the primary contributor to this sink due to its slow rate of turnover (years to centuries).

However, climate change is increasing the frequency and intensity of drought events and negatively impacting both photosynthesis and Bst.

As these two processes are interconnected but independently modulated by environmental variables, it is imperative that we track the fate of forest carbon through its lifecycle from uptake to allocation.

In TERRACARB, we will investigate the interactions between climate, photosynthetic carbon uptake, and carbon allocation to Bst during drought across spatial and temporal scales (tree to global; hourly to decadal).

To do so we will use an innovative interdisciplinary approach that combines remote sensing, eddy covariance, tree-rings, and point dendrometer derived estimates of productivity. First, we will investigate the decrease in photosynthetic carbon uptake during atmospheric and hydrologic drought.

Next, we will examine the mechanisms by which drought events leave behind ‘legacy effects’ of below normal carbon accumulation.

Finally, we will use a network of point dendrometers to evaluate the relationships between photosynthetic carbon uptake, tree radial growth, hydration, and climate variables at sub-seasonal timescales (hourly to daily) at five eddy covariance sites in Europe.

The findings from TERRACARB will help us better predict how forests will continue to accumulate carbon in the face of climate change.