Causes of Landscape Pattern

Temporal variation in abiotic factors: Milankovitch Cycles Changes in the earth’s orbital parameters Changes 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 ages Causes Ice ages About a 5 o C change in mean global temperatures between glacial and interglacial conditions About a 5 o C change in mean global temperatures between glacial and interglacial conditions

For the current Interglacial period, peak warming, about 1-2 o C warmer than present, occurred about years ago (not shown in figure above) For the current Interglacial period, peak warming, about 1-2 o C warmer than present, occurred about years ago (not shown in figure above) The “Little Ice Age” was about 1 o C cooler than current temperatures The “Little Ice Age” was about 1 o C cooler than current temperatures Anthropogenically driven climate change (“super interglacial”) due to the burning of fossil fuels is predicted to result in a warming of about 2-4 o C over the next century. Anthropogenically driven climate change (“super interglacial”) due to the burning of fossil fuels is predicted to result in a warming of about 2-4 o C over the next century.

PNW Vegetation Response: Glacial to Interglacial Brubaker 1991

PNW Fire Frequency/Size Response: Little Ice Age to Present Wallin et al. 1996

Decadal variations in climate: The Sahel zone in Africa 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 Dark line is mean position. End of colonial rule for most countries in this region

Decadal variations in climate: El Nino/Southern Oscillation

Tend to be great snow years in the PNW!

Decadal variations in climate: El Nino/Southern Oscillation

Temperate Forest Majority lie between 40 o and 50 o. Majority lie between 40 o and 50 o. Rainfall averages 650 – 3,000 mm. Rainfall averages 650 – 3,000 mm. Fertile soils Fertile soils Long growing seasons dominated by deciduous plants. Long growing seasons dominated by deciduous 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 moisture and nutrients From Swanson et al. 1988

Spatial patterns: Landform constraints on disturbance From Swanson et al. 1988

Spatial patterns: Dispersal constraints

Spatial patterns: Potential range changes under 2 x CO 2

Biotic Disturbance Agents Beaver Beaver Bison Bison Bugs Bugs Humans Humans

Historic Changes in Forest Cover

Forest Cover Change in Wisconsin