Thresholds and State Changes Climate Rate and Trajectory of Successional Changes in Ecosystem Processes Sensitivity and Response to Change Frequency and Intensity of Disturbances (Flooding, Fire, Thermokarst, Insect/Pathogens) Sensitivity and Response to Change Abundance of Key Species Thresholds and Regime Shifts Hypothesis: Novel boreal landscape patterns emerge when climate change leads to disturbance regimes that alter permafrost integrity and the abundances of key functional types.

Thresholds and State Changes 1) How often and under what circumstances does wetland drying or thawing of permafrost cause a change in ecosystem state? Document hydrologic changes in permafrost- dominated wetlands Interaction among landscape position and fire on permafrost thaw, thermokarst development and wetland drying? Using Landsat images, develop predictive relationship among landscape variables and change in wetland extent T1

Thresholds and State Changes 2) What disturbance-induced changes in functional types might trigger a change in ecosystem state, and what are the ecosystem consequences? Determine the effects of altered disturbance regime on successional trajectory and ecosystem processes Determine the disturbance frequency and conditions under which new successional trajectories occur Track tree establishment/community composition post burn. Experimentally manipulate seed and seedlings T2a Document effects of ecosystem change (fire, thermokarst) on organic matter/nutrient standing stocks and ecosystem processes Track community composition, C & N stocks/transformations post fire and thermokarst T2b

Thresholds and State Changes 2) What disturbance-induced changes in functional types might trigger a change in ecosystem state, and what are the ecosystem consequences? Document impacts of disease and insect outbreaks on ecosystem processes Document 1) interannual variation in the abundance of insect and pathogen species, and 2) consequences of selected outbreaks Determine impact on microclimate, stand dynamics, NPP, N-fixation T3

Thresholds and State Changes Monthly Talks: May: Spruce budworm and climate change (Juday) June: Predictive rules for post-fire succession in upland forests (Johnstone, Hollingsworth & Juday) July: Loss of moss as potential threshold (Turetsky, Mack and Hollingsworth) August: Permafrost driving variables and responses (Schuur and Jones)

August May/June The spruce budworm completes its life cycle within a 12- month period, but spread across 2 different years. First year events Second year eventsstart

Temperature control of spruce budworm 1st instar larva development rate (August). 13 o 23 o Han, E.; Bauce, E.; Trempe-Bertrand, F Development of the first-instar spruce budworm (Lepidoptera: Tortricidae). Annals of the Entomological Society of America 93(3): gs = green substance

? “In Alaska, significant budworm damage was detected in 1978 on white spruce in many residential and park areas of Anchorage.” (Holsten: USDA Forest Service, Alaska Region Leaflet R10-TP-11) Analysis: G. Juday

July 7 ( July 6 Leap yr.) ?July June July August

Data: National Weather Service Analysis: G. Juday no budworms Datastart

“Not known to breed in Alaska.” “Has occurred at Fairbanks, Haines, Pt. Barrow.” Armstrong Birds of Alaska. Cape May Warbler (Dendroica tigrina) : “ … the fortunes of its populations are largely tied to the availability of spruce budworms, its preferred food.” dendron = tree oikein = dwell tigrinus = striped

BARK spruce budworm damage heat/droughtlimitation Photo: C. Alix

1912 volcanic ash? 1993 & 95 spruce budworm defoliation 2004 record hot Data: G. Juday KILL ZONE

The 25th anniversary of the Rosie Creek Fire: Rules of post-fire succession in Alaska boreal forest Glenn Patrick Juday, Professor of Forest Ecology Bonanza Creek LTER monthly synthesis meeting Fairbanks, Alaska 12 June, 2008

Second 100 m (100 to 200 m) First 100 m (0 to 100 m) Surviving seed source stand Hectare1RSW Photo - BNZ LTER July, 2007

First 100 m (0 to 100 m) Second 100 m (100 to 200 m) Surviving seed source stand Hectare1RSW

comparable years (20th) comparable years (17th) comparable (12th) (5th)(20th)

crushing from snagfall primarilycumulative tree death?

Recruitment declines with organic depth 2-yr recruitment from seeding experiments (Alaska/Yukon) n=4 to 16 (total plots = 60) Aspen is more sensitive to organic layer thickness than conifers

Species- specific responses to seedbeds lead to strong effects on post- fire dominance Seedling Density Aboveground Biomass Burned spruce forest Alaska 40,000 ha burn 8 yrs post-fire n=19 stands

Fire & regeneration thresholds Residual organic layer determines seedbed quality Differences in species sensitivity lead to strong composition effects Increased fire severity => crossing threshold of residual organics => shift in successional trajectory

Critical Research Moving deeper in time –What are the longer term consequences of variations in fire severity? Understanding space –Which parts of the landscape are vulnerable to shifts in trajectories, and which aren’t? Can we test anticipated changes?

Changing moss communities and the potential for ecosystem thresholds in the Alaskan boreal forest Merritt Turetsky, Teresa Hollingsworth, Michelle Mack LTER Synthesis Talk and chapter for the CJFR special issue

Biodiversity Soil Habitat Ecosystem Productivity Organic matter and nutrient turnover Moisture/thermal regulation

Objective 1: Use meta-analysis to address “moss lore” Moss NPP inversely proportional to vascular plant production Moss NPP ≥ black spruce in boreal forest Moss decay  vascular litter Moss ≥ vascular biomass for long-term carbon storage

Boreal Productivity Wetland Upland U W Understory ANPP (g m -2 yr -1 ) U U U W W W W Spruce ANPP (g m -2 yr -1 ) Spruce generally > moss Spruce ANPP (g m -2 yr -1 ) Spruce generally > moss Moss NPP (g m -2 yr -1 )

Litter decay rates

Moss and long-term C storage Mass of peat (g/cm 2 ) Moss Sph/wood Sedge/moss Sedge/wood Sylvic Lacustrine Marl Wood Mass of peat (g/cm 2 ) Moss Sph/wood Sedge/moss Sedge/wood Sylvic Lacustrine Marl Wood

abundance (% cover) White Spruce (FP4) Alder/BP (FP2) Moss abundance at LTER sites year

1)Use meta-analysis to address key assumptions about moss and boreal ecosystem Moss vs. vascular NPP Moss vs. vascular decomposition Changing moss abundance with  N, temp, fire 2) Apply insight to understand implications of changing moss abundance across LTER sites Goals for synthesis chapter

PERMAFROST THAW AND THERMOKARST FORMATION

From Schuur et al. 2008

PERMAFROST THAW AND THERMOKARST FORMATION From Schuur et al. 2008