Causes of Landscape Causes of Landscape PatternPattern

Temporal variation in abiotic factors: Temporal variation in abiotic factors: Milankovitch CyclesMilankovitch Cycles

Changes in the earth’s orbital parametersChanges in the earth’s orbital parameters Leads to changes in inputs of solar radiation by about 3.5%Leads to changes in inputs of solar radiation by about 3.5% Causes Ice agesCauses Ice ages

About a 5About a 5ooC change in mean global temperatures between glacial C change in mean global temperatures between glacial and interglacial conditionsand interglacial conditions

About a 5About a 5ooC change in mean global temperatures between glacial and C change in mean global temperatures between glacial and interglacial conditionsinterglacial conditions

For the current Interglacial period, peak warming, about 1-2For the current Interglacial period, peak warming, about 1-2ooC C warmer than present, occurred about 9000-4000 years ago (not warmer than present, occurred about 9000-4000 years ago (not shown in figure above)shown in figure above)

The “Little Ice Age” was about 1The “Little Ice Age” was about 1ooC cooler than current temperaturesC cooler than current temperatures Anthropogenically driven climate change (“super interglacial”) due Anthropogenically driven climate change (“super interglacial”) due

to the burning of fossil fuels is predicted to result in a warming of to the burning of fossil fuels is predicted to result in a warming of about 2-4about 2-4ooC over the next century. C over the next century.

PNW Vegetation Response: Glacial PNW Vegetation Response: Glacial to Interglacialto Interglacial

Brubaker 1991

PNW Fire Frequency/Size Response: PNW Fire Frequency/Size Response: Little Ice Age to PresentLittle Ice Age to Present

Wallin et al. 1996

Decadal variations in climate: The Sahel zone in Decadal variations in climate: The Sahel zone in AfricaAfrica

Rainfall departures from the long-term mean for the Sahel Zone of Africa

Variation in the position of the 200 mm/yr rainfall boundary over the period from 19870-1990. Dark line is mean position.

End of colonial rule for most countries in this region

Decadal variations in climate: El Nino/Southern Decadal variations in climate: El Nino/Southern OscillationOscillation

Decadal variations in climate: El Nino/Southern Decadal variations in climate: El Nino/Southern OscillationOscillation

Tend to be great snow years in the PNW!

Decadal variations in climate: El Nino/Southern Decadal variations in climate: El Nino/Southern OscillationOscillation

Temperate ForestTemperate Forest Majority lie between 40Majority lie between 40oo and 50 and 50oo.. Rainfall averages 650 – 3,000 mm.Rainfall averages 650 – 3,000 mm. Fertile soilsFertile soils

Long growing seasons dominated by deciduous Long growing seasons dominated by deciduous plants.plants.

Short growing seasons dominated by conifers.Short growing seasons dominated by conifers. Biomass production can be very high.Biomass production can be very high. Many major human population centers.Many major human population centers.

Fig. 3 from Waring and Franklin 1979

Spatial patterns: Landform constraints on Spatial patterns: Landform constraints on moisture and nutrientsmoisture and nutrients

From Swanson et al. 1988

Spatial patterns: Landform constraints on Spatial patterns: Landform constraints on disturbancedisturbance

From Swanson et al. 1988

Spatial patterns: Spatial patterns: Dispersal Dispersal

constraintsconstraints

Spatial patterns: Potential range Spatial patterns: Potential range changes under 2 x COchanges under 2 x CO22

Biotic Disturbance AgentsBiotic Disturbance Agents

BeaverBeaver BisonBison BugsBugs HumansHumans

Historic Historic Changes in Changes in

Forest CoverForest Cover

Forest Cover Change in WisconsinForest Cover Change in Wisconsin