Millennial-scale Dynamics of Continental Peatlands in Western Canada: Pattern, Controls and Climate Connection Zicheng Yu Lehigh University Bethlehem, Pennsylvania QUEST Workshop on CH4 & Wetlands June 2004, Bristol, UK

Acknowledgements  Dale Vitt, Kel Wieder, Merritt Turetsky, Dave Beilman, Ilka Bauer, Mike Apps, Celina Campbell, and Ian Campbell for sharing slides, data and ideas.  Climate Change Action Fund (Canada) and National Science Foundation (US) for funding.

Outline of Talk  Overview of continental peatlands in western Canada  Accumulation pattern & trajectories  Possible climate & global C cycle connections  Conclusions

Permafrost peatlands Open fens Treed fens Bogs (treed) Peatland Types in Western Canada

Total peatland area = 365,160 km 2 (21% landbase) 63% fens 28% permafrost bogs 9% non-permafrost bogs % Cover Vitt et al. (2000) Peatland Distribution

Nonpermafrost bogs Permafrost bogs Treed fens Shrubby fens Open fens - nonpatterned Open fens - patterned C Storage (Pg) Arctic Subarctic Montane High boreal Mid-boreal Parkland Total = 48 Pg Vitt et al. (2000) Peatland Carbon Storage

Fens are more important C pool and have larger area than bogs in continental Canadian peatlands, as well as bigger CH4 emitters, but we know much less about these ecosystems than bogs in general

Outline of Talk  Overview of continental peatlands in western Canada  Accumulation pattern & trajectories  Possible climate & global C cycle connections  Conclusions

Because: Observed pattern  Infer & understand the processes  Projecting future dynamics/trajectories Why accumulation pattern matters? (Concave) (Convex)

Concave Pattern from Oceanic Bogs (assuming constant PAR and decay) “apparent” C accumulation rate

Study Sites Basal dates from ~80 paludified peatlands 5 sites with hi- resolution peat core analysis

Loss-on-Ignition from Upper Pinto Fen Yu et al cm LOI n=20 dates also, 2-cm macro 2-cm isotopes

Peat Depth-Age Curve: Convex at UPF Yu et al Opposite to well- documented “concave” pattern

What Does This Indicate? Causes? decreasing peat-addition rates from acrotelm, and/or increasing catotelm decomposition rate

A Simple Extended Model Yu et al. 2003

Sensitivity to Changes in Decay & PAR Yu et al. 2003

Change in PAR over Time g m -2 yr g m -2 yr -1 Yu et al PAR decrease from initial 192 to eventual 26 g/m2/yr could explain the observed pattern

Summary I  The model suggests that unidirectional decrease of PAR from 192 to 26 g m -2 yr -1 over that 5400-yr period at UPF could result in the observed convex pattern.  Autogenic drying trend resulted from fen height growth gradually isolates peat surface from water and nutrient sources, causing decreased production, especially for water-demanding rich fen species - esp. in moisture-limiting continental regions.  This analysis indicates that continental peatlands with convex pattern may reach their growth limit sooner than previous model predicts.

Convex Other Sites I (Kubiw et al. 1989)

Western Canada: Slave Lake Bog (Kurry & Vitt 1996) Southwestern Finland: Pesansuo raised bog (Ikonen, 1993) Western Siberia: Salym-Yugan Mire (Turunen et al. 2001) Convex Other Sites II

Convex Pattern from Regional Sites (Yu & Vitt, in prep)

Outline of Talk  Overview of continental peatlands in western Canada  Accumulation pattern & trajectories  Possible climate & global C cycle connections  Conclusions

Climate Proxy from UPF (Yu et al. 2003)

UPF W. Canada (Yu et al. 2003)

Global Climate & C Cycle Connections? Yu et al Bond et al Indermuhle et al Chappellaz et al Brook et al. 2000

Summary II  Peat accumulation in western Canada shows sensitive response to Holocene climate variability at millennial time scale.  Peatland carbon dynamics may connect to change in atmospheric CO 2 concentrations (Peatlands in western Canada contain ~50 Pg C, which is equivalent to ~25 ppm CO 2 if all remained in the atmosphere).  Are there similar pattern in other peatlands of northern latitudes?

Pervasive Climate Controls of Peatland Dynamics A thawed bog shows similar millennial-scale variations Patuanak Bog (internal lawn)

Connection of Siberian Peatland Initiations and Atmospheric CH4 N = ~200 Smith et al. 2004

Bill Ruddiman’s hypothesis:  CO2 increase since 8 ka: caused by deforestation;  CH4 increase since 5 ka: caused by rice cultivation

Allogenic and Autogenic Controls of Peatland Dynamics: a conceptual model Yu et al Autogenic drying Climate wetting Climate fluctuations

The different accumulation pattern observed in continental peatlands suggests these peatlands follow different trajectories historically and may respond to climate change differently (compared to well-studied bogs); Continental peatlands appear to show sensitive responses to subtle millennial-scale moisture changes during the Holocene; Fens seem to be more variable in C accumulation and more sensitive (less self-regulating) to climate variations than bogs; Northern peatlands might have had detectable impacts on atmospheric CO2 and CH4 concentrations during the Holocene. Conclusions

Develop scaling-up models to take advantage of detailed inventory results from western Canada or other regions for regional CH4 emission estimates by peatland types (as a validating tool for global model?); Confirm the extent of past climate – peatland – global C cycle connections, particularly using multiple proxies from paired lake- peatland approach (lakes for independent climate reconstructions); Understand implications of permafrost (intact, thawing, and thawed) peatlands (and fen-bog transition) for CH4 emission/budget – permafrost is one of the biggest surprises to come in peatland C dynamics; Integrate/reconcile down-core paleo data with present-day instrumental C flux measurements. Suggestions