Long-term perspectives on lagged ecosystem responses to climate change: Permafrost in boreal peatlands and the Grassland/Woodland boundary

Changes in climate could have far-reaching consequences for ecosystems sens itive to changes in temperature and precipitation, such as boreal permafros t peatlands and grassland/woodland boundaries. The Long-term data from our studies in these ecosystems suggest that transient responses of permafrost and vegetation to climate change may be difficult to predict due to lags an d positive feedbacks related to vegetation and disturbance. Boreal permafro st peatlands comprise an ecosystem with strong local controls on microclima te that influence the formation and thaw of permafrost. These local control s may preserve permafrost during! the transient stages of climate warming, producing lagged responses. The prairie-forest border region of the norther n Great Plains has experienced frequent change and has complex dynamics inv olving transitions in the grassland composition of prairie and in the degre e of woodiness in bordering forests. Fire frequency interacts with fuel loa ding and tree recruitment in ways that affect the tinting and direction of change. Lags and thresholds could lead to sudden large responses to future climate change that are not readily apparent from current vegetation. The c reation of adequate models to characterize transient ecosystem changes will require an understanding of the linkages among processes operating at the scale of 10s of meters and over long time periods.