More disturbance from wind and fire in a warmer climateJuly 1995 derecho series From: R.H. Johns and J.S. Evans: www.spc.noaa.gov/misc/AbtDerechos
Minneapolis Star tribuneBefore and after the 1999 blowdownin the Boundary Waters, northern MN
Wind does selective weeding of the forestDivergence of forest composition after wind versus wind/firecombination BWCAW case study
Tornado reports per decade. Paul Huttner, MPR.
Wind + Fire = majortransformationof the forestPhotos: Dave Hansen
Native insects play a major role in forest changeBenign native insects can have outbreaks in a warmer climate.For example, mountain pine beetle in British Columbia—anative insect that caused massive tree mortality over 30 millionacres of lodgepole pine forest, and could threaten jack pinein MN
Comparing the 2060s with current Dai, 2010, Drought under global warming, Climate Change DOI: 10.1002/wcc.81
Photo: Dave HansenMore drought = trees under stress and forest dieback
Impacts of deer grazing reinforcing climate changeSylvania Wilderness maple and hemlock forest in 1990
Sylvania in 2006, after the deer have eatenPictures from Salk, Frelich, Montgomery, Calcote, and Ferrari, preliminary acceptance inForest Ecology and Management
Global warming orGlobal worming?Earthworms are ecosystemengineers that can alter thestructure of soil, and changethe H2O, N and P cycles, Cdynamics and seedbedcharacteristics on aregional scale
Heavily earthworm infested siteswithout lawn. Photo: Paul Ojanen (left), DaveHansen (right) Earthworms warm the soil by removing insulating O horizon, compact the soil, cause more runoff, create lower avail- ability of N and P, lower the species richness of native plants and facilitate invasive plants
Seed emergence experimentwith endogeic and anecicearthworms both present:Graminoids are favored
Lawn of sedge created by earthworm and deerPhoto: Paul Ojanen
Photos: J. Schlaghamersky Stage 2, Dendrobaena only Stage 3, + Aporrectodea ssp. and L. rubellus Stage 4, + L. terrestris
Invasive plants that may be facilitated byearthworm invasion:Buckthorn (common and glossy)Garlic mustardTatarian honeysuckleBlack swallowwort (Cynanchum)Japanese barberryHemp nettle (Galeopsis tetrahit)Veronica ssp.Stiltgrass (Microstegium)
Fisichelli study of sapling success and growth overa 4 degree F temperature gradient in mixed boreal-northern hardwood forests 14 Sapling growth study sites
Local Scale: 3 overstory neighborhood types Temperate Mixed Boreal >67% Temperate 33-67% Temperate <33% Temperate Overstory Type overstory tree overstory tree overstory tree rel. abundance rel. abundance rel. abundance
Species Regeneration Response to: Temp Precip pH Deer Litter Conspecific Depth OverstoryFir/Spruce 0 0/-Red maple 0 0/-Sugar maple
Methods: Sizing Up the Competition; Growth Measurements 5 species Radial Growth Height Growth ‘09 ‘08 Distance between Balsam fir ‘07 terminal bud scars (Abies balsamea) White spruce (Picea glauca) Red maple (Acer rubrum) Sugar maple (Acer saccharum) Red oak (Quercus rubra)
Results: Temperate sapling relative performance ‘cooled’ by deer(a) low browse pressure15 A. balsamea Height growth (cm yr ) −1 10 A. balsamea balsamea A. glauca P. balsamea A. glauca 7 P. glauca P. balsamea A. rubrum Abies balsamea A. glauca P. rubrum Picea glauca 5 4 A. rubrum A. glauca P. saccharum Acer rubrum 17.0 17.5 18.0 18.5 19.0 A. saccharum rubrum A. saccharum Acer saccharum(b) high browse pressure A. rubrum Q. rubra Quercus rubra A. rubra saccharum 15 Summer Temperature (°C) Q. saccharum A. Q. rubra Height growth (cm yr ) −1 10 Q. rubra 7 Q. rubra 5 4 17.0 17.5 18.0 18.5 19.0 Mean summer temperature oC Summer Temperature (°C)
Sugar maple versus spruce in the temperate-boreal ecotone Temp change Deer, moose, earthwormsTemperature pushing harder than opposing forces
Temperate BorealTemperate forest tree species are now invading boreal stands,but this process is slowed by deer in some areas. For now, themixed forest zone is becoming broader.
Silty clay loam With serial correlation SandSerial correlation prevented maple from replacing spruce forest on sand,but not silty clay loam, for a 2xCO2 scenario. Cohen and pastor 1991.
Sugar maple versus oak in in the temperate zone Temperature change, earthworms DeerNo net direction???
Expect mesic forest types such as northern hardwoodsto contract their niche Silt loam Loam Loamy sand
Mark StennesEcological blueprints for a warmer climateA forest of American basswood, elms, Kentucky coffeetree,hackberry, and bur oak could be the future for central andnorthern Minnesota, northern Wisconsin and Upper Michigan
If the climate trends towards a Savanna climate on shallow soils: •Try for the best savanna possible (i.e. native species, not buckthorn). •Resources for assisted migration and seed amplificationThe Prairie Enthusiasts would be necessary Buckthorn on rocks in northern MN Photos: Paul Ojanen Molly McGovern
Multiple impacts of climate change at the prairie-forest border. Frelich and Reich, 2010 Frontiers in Ecology and the Environment Warmer climate, More frequent and longer Longer growing season droughts CO2 fertilization Warmer and Exotic earthworms drier soil spread faster Lower soil N deposition nutrient status More deer Kill seedlings More fires and prevent reproduction More wind storms Kill adult trees and lack of Savannification replacement Pests and diseases spread faster
Thresholds for disturbance severity necessary to changeforest composition are lower when a forest is under stress Clearcut or stand leveling wind High Ecosystem wellLate adapted to climatesuccessional Ecosystemdominance under stress from climate Low Low High Disturbance severity
What does this all mean?Global warming is about the effects of droughts, storms,fires, bugs, worms and deer on the forestThese factors will reinforce the impacts of changingtemperature and lead to more divergence among soil typesThese factors will make abrupt change afterdisturbance more likelyFuture forests and savannas that replace thecurrent forests will have novel plant compositiondue to different filters on which species are successful
Questions? Layne KennedyLee Frelich and clones at work during Ham Lake Fire, Seagull Lake, May 6, 2007