Casey McCabe
Global Change: Biome Perspective
(Illustration by Nicolle Rager Fuller, National Science Foundation.)

Carbon sink through primary
production
 Stores less than boreal and tropical
 51% in living biomass
 37% in dead wood, litter and soil

(Bonan 2008, Pan et al. 2011)
Important for regional carbon
budgets

Contribution to global water
cycle and cloud formation

Rates vary across forest types

Forests and crops have higher
evaporative cooling than
grasslands

Forests have l0w albedo
compared to grassland/crops

Land use change in past
converted large amount of
temperate forest to cropland
 Highly managed
(Bonan 2008, Jackson et al. 2008, Peters et al. 2013)
Physicochemical
Changes
Indirect Effects
& Feedbacks
Megadisturbance
(Pautasso et al. 2012)
2013 IPCC Report
Temperature
Precipitation
CO2

Increased evaporation

Biological effects
 Changes in phenology
 Range shifts

Increased rain vs. snow and
snow melt
 Heat stress
 Changes in growth rate
▪ Increases and decreases
(van Mantgem 2009,
Keenan et al. 2014)

Very variable according to region
 Increases in eastern U.S., northern Europe, southeast Asia
 Decreases in western U.S., southern Europe, northeast
Asia, and eastern Australia

Some areas with increased drought or flooding
 Flooding can increase or reduce nutrient levels
 Drought can cause tree death and increase susceptibility to
pests, pathogens, and fire
(2013 IPCC Report, Bentz et al. 2010, Millar and Stephenson 2015)


Atmospheric CO2 is increasing
Positive for plant growth and water-use efficiency
▪ Response may be limited by water and nutrients
2013 IPCC Report
(Silva and Anand 2013)
(Bonan 2008)
 Temp =  Evaporation =  Evaporative Cooling
 Transpiration
 Drought
 Temp =  Snow = Yearly Soil Moisture
 CO2 =  Transpiration =  Drought Tolerance
 Temp =  Photosynthesis =  Carbon Sink
 CO2 =  Photosynthesis =  Carbon Sink
 Water =  Photosynthesis =  Carbon Sink
(Keenan et al. 2014)
(Millar and Stephenson 2015)
(van Mantgem et al. 2009)

Baseline mortality of trees is
increasing

Dead trees release large
amounts of carbon

Old-growth forests store
more carbon

Overall, increase in large disturbances across
the globe related to global change forcings

More intense droughts, fires, biotic
outbreaks, and heat waves
(Dale et al. 2001, Millar and Stephenson 2015)

Increasing due to temperature increase

20.4 million hectares of forest in the US
impacted by biotic forcing (10 Massachusetts)
annually
 The most expensive disturbances for humans

Magnitude of disturbance can equal or
surpass that of direct climate forcings
( Bentz et al. 2010)
(Flower and Gonzalez-Meler 2015)
Bentz, B. J. et al. Climate change and bark beetles of the western United States and Canada: Direct and indirect effects. Bioscience 60,
602–613 (2010).
Bonan, G. B. Forests and climate change: forcings, feedbacks, and the climate benefits of forests. Science 320, 1444–1449 (2008).
Dale, V. H. et al. Climate change and forest disturbances. Bioscience 51, 723–734 (2001).
Flower, C. E. & Gonzalez-Meler, M. A. Responses of temperate forest productivity to insect and pathogen disturbances. Annu. Rev. Plant
Biol. 1–23 (2015).
Jackson, R. B. et al. Protecting climate with forests. Environ. Res. Lett. 3, (2008).
IPCC Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the
Intergovernmental Panel on Climate Change (eds Stocker, T. F. et al.) (Cambridge Univ. Press, 2013).12.
Keenan, T., Gray, J. & Friedl, M. Net carbon uptake has increased through warming-induced changes in temperate forest phenology. Nat.
Clim. Chang. 4, 598–604 (2014).
Millar, C. I. & Stephenson, N. L. Temperate forest health in an era of emerging megadisturbance. Science 349, 823–826 (2015).
Pan, Y. et al. A large and persistent carbon sink in the world’s forests. Science 333, 988–993 (2011).
Pautasso, M., Döring, T. F., Garbelotto, M., Pellis, L. & Jeger, M. J. Impacts of climate change on plant diseases-opinions and trends. Eur. J.
Plant Pathol. 133, 295–313 (2012).
Peters, E. B., Wythers, K. R., Zhang, S., Bradford, J. B. & Reich, P. B. Potential climate change impacts on temperate forest ecosystem
processes. Can. J. For. Res. 950, 939–950 (2013).
Silva, L. C. R. & Anand, M. Probing for the influence of atmospheric CO2 and climate change on forest ecosystems across biomes. Glob.
Ecol. Biogeogr. 22, 83–92 (2013).
van Mantgem, P. J., Stephenson, N. L., Byrne, J. C., et al. Widespread increase of tree mortality rates in the western United States.
Science 323, 521–524 (2009).