Northern peatlands provide important ecosystem services and while these ecosystems
are facing large increases in the areal extent and frequency of climate-mediated
disturbances (e.g., wildfire, drought), they are generally resilient to these disturbances.
Numerous autogenic ecohydrological feedbacks operate within peatlands that regulate
their response to changes in seasonal water deficit. However, our recent research has
determined that shallow peatlands have greater water table variability and drawdown
rates, moisture stress and depths of burn than deeper peatlands. Moreover, we found
that peatland carbon sequestration was significantly lower during periods when the water
table dropped below the peat layer, which occurs more often in shallow peatlands. This
suggests that shallow peatlands are less resilient to disturbance due to the limited
capacity of their autogenic ecohydrological feedback mechanisms to mitigate
disturbance, when compared to deeper peatlands.
We explore how several ecohydrological feedbacks change in sign and strength with
increasing peatland depth and argue that shallow peatlands represent ecohydrological
sentinels for climate change; acting as a bellwether for deeper peatlands in a future with
more frequent, prolonged, and intense water deficits. We suggest that an explicit
quantification of peatland feedback mechanisms across a gradient of hydroclimatic
settings, and the thresholds and constraints they operate under, will help identify
systems at greatest risk for loss of function or catastrophic degradation under climate
change. Furthermore, this work provides insight into peatland restoration and peatland
evolution as all deep peatlands were, at one point, shallow and perhaps at the height of
their vulnerability.