Forest Biomes - Plant Ecology in a Changing World · • coniferous forest temperate regions • coniferous forests • temperate deciduous forest • Mediterranean-climate woodland

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Plant Ecology in a Changing World Jim Ehleringer, University of Utah

http://plantecology.net

Forest Biomes

Forest Biomes Part 1

General climatic distribution patterns

Upper Millcreek Canyon

boreal regions • coniferous forest temperate regions • coniferous forests • temperate deciduous forest • Mediterranean-climate woodland subtropical and tropical regions • savanna • tropical rainforest

Forest biomes

There are five primary forest biomes:

Climatic patterns associated with forests

If precipitation > potential evapotranspiration throughout warm temperature periods, we find • tropical rainforest (winter warm) • temperate deciduous forests (winter cold) • temperate coniferous forests (summer cool) • savanna (summer wet only) If precipitation < potential evapotranspiration during warm temperature periods, we find • Mediterranean-climate woodland (winter wet)

cold warm

winter temperature

cool

warm

summer temperature

cool

tropical rain forest

coniferous forest

deciduous forest

coniferous forest

none

Mediterranean climate

Conifers tend to occur in regions with lower evapotranspiration rates than deciduous forests even though site water balance values may be similar.

Forest Biomes Part 2

Cold temperatures constrain upper tree limits whereas drought determines the lower limits

Black spruce dominate the boreal forests of Canada

Boreal forest climate diagrams (note temperature values)

The northern limits of boreal forest corresponds with lower permafrost limit The southern part of boreal forest corresponds with southern limit of winter arctic fronts

Climate diagrams of coniferous forests of the Pacific Northwest

Coniferous forests of the Pacific Northwest (40-70 m tall); central Oregon

Climate diagrams and plant distribution along Oregon transect

Spruce and hemlock are common in the wettest locations (central Oregon)

Juniperus osteosperma (dry end for conifers) Coral Pink, Utah

Forest Biomes Part 3

The interior coniferous forests exhibit strong distribution gradients along

elevational clines

Coniferous forest are found along elevation gradients in the West where rainfall ranges between 300-3000 mm per year

Generalization of forest tree gradients in the western U.S.

There are rainfall gradients within our own Wasatch Mountains

There are large rainfall gradients within our own Wasatch Mountains

Plant distribution gradients in Big Cottonwood Canyon, Utah

Slope aspects influence microsite water balance and therefore will also often determine vegetation composition at different elevations (Utah Valley)

Forest landscapes are often patchy, because of fires, logging, and ground water near the surface (Big Cottonwood Canyon, Utah)

Little Cottonwood Canyon

Land-use history has modified the landscape, reducing forest cover

Historical timber activities have reduced conifer abundances in Big Cottonwood Canyon

Juniperus osteosperma is also more common today because of land-use history (fire prevention) (Big Cottonwood Canyon)

Vegetation distribution along elevational gradients in Arizona and in Montana

also reflects the constraints of water stress and evapotranspiration

Forest Biomes Part 4

The eastern deciduous forests

Deciduous forest climate diagrams

The eastern portions of continents is frequently dominated by deciduous forests

http://www.ohio.edu/people/dyer/gifs/FOR_REG.jpg

Lower elevations along the Wasatch Mountains are dominated by a dwarf deciduous forest (oak-maple woodland)

riparian zone

oak-maple woodland

Oak woodland and grassland transition near Red Butte Canyon

Oak clones and maple expansion

on Mount Olympus

Forest Biomes Part 5

Savannas dominate seasonally dry tropical/subtropical regions (winter dry, summer wet),

whereas rainforests dominate aseasonal regions

Savannas have seasonal precipitation, whereas tropical rainforests tend to have aseasonal precipitation

rain forest savanna

tropical rain forest in Manaus, Brazil (25-40 m tall)

Amazon rain forest (ZF2, Manaus)

tropical rainforests are often very structured with several canopies layers as well as a well developed understory

Amazon rain forest (ZF2, Manaus)

gap in rainforest

Amazon rain forest (ZF2, Manaus)

Conversion to pasture is a form of land-use change that is changing the cover in many tropical forest regions

Amazon rain forest (ZF2, Manaus)

http://defensoresdanatureza.com.br/wp-content/uploads/2014/09/dia-nacional-do-cerrado-defensores-da-natureza-2-1024x694.jpg

Cerrado (savanna) in central Brazil

https://en.wikipedia.org/wiki/Savanna#/media/File:Tarangire-Natpark800600.jpg

Savanna in Tanzania

http://www.cas.vanderbilt.edu/bioimages/biohires/ecoregions/h50415oak-savannah5002.jpg

Savannas occur in temperate grassland-forest transition too (e.g., Minnesota) Cedar Creek Natural History Area