Topic 7- Temperature

What makes up Geographical pattern For temperature

• Latitude - major determinant of temp. Season important due to tilt of Earth

• Distance from ocean- water has higher water storage capacity, buffers changes & continental locations gain or lose heat more quickly

• Elevation- 100 meters up make up 1 degree of latitude. Tree line growing season temp across the globe is relatively consistent

• Seasonality

Impact on temperature on growth factors

• Day length

-Number of days when above ground growth is possible (estimated as number of days between the average date of the last killing frost in the spring and first killing frost in the fall)

• Heat Sum Index

-Amount of heat that plants are exposed to

-Product of the number of days over a base temp and the number of daylight hours at that temp

-Imporatnt factor for flowering and bud burst in the spring (Variation across species)

Temperatures at the soil surface

• What drives daytime vs nighttime temps

• Important drivers of ecosystem productivity

• What influences soil temperature

What drives daytime vs nighttime temps

Day time: Regulated by SOLAR RADIATION

Night time: Determine by the amount of HEAT ABSORBED BY TERRESTRIAL OBJECTS and the ability of those objects to hold heat

Important drivers of ecosystem productivity

• Biological activity of roots and their associated microbial organism

• Nutrient and water uptakes

• Mineralization and Decomposition

What influences soil temperature

1.) Soil Water Content

2.) Soil Properties

-Thermal conductivity and Particle Size

3.) Leaf Litter

Microclimate and more

• Variation in climatic parameters within a small spatial scale)

Factors include abiotic and biotic

Abiotic- Topography, elevation, soil props, water bodies, sun exposure

Biotic- Stand Structure, Forest type, Density (greater density, greater modulating effect), Forest Age (old growth forests have the greatest ability to moderate temp use to complex structures

Consider all this for management

Frost Pockets/ Valley Fog

Influence of Temp on Photosynthesis

• All temps have a temp range where they preform best (photosynthesis will decrease outside this range)

• Extreme cold and heat

• Cold tolerance

What happens when plants experience extreme cold or heat

Cold:

• Slows down cell processes

• Causes plasma membrane to lose function

• Ice damage

Heat:

• Proteins lose function (help by helping denatured proteins to reform quickly)

• Cells dry out

Cold tolerance

Unprotected cells vs protected cells

Protected:

• Ice nucleating proteins

• Antifreeze proteins

• Solute transfer

• Membrane protection

Plant dormancy

Process of making the plant more tolerant to cold temperatures

Triggered by short days

• Pre Dormancy- Reversible (Startch starts to accumulate in roots)

• True Dormancy- Production of proteins, membrane lipids, and compounds for frost tolerance

Many plants skip true dormancy they go from pre to post

Plasticity, Acclimation, and Cold tolerance in plants

Frost hardiness is costly for trees, many species of Eastern trees exhibit variation in hardiness based on where in their range they are

Ex: Rhododendrons (Leaf Rolling)

Breaking Dormancy

Most temperate woody species require a period of cold temps before growth can resume in the spring. Once the chilling requirement is met, spring growth processes are temp dependent.

Stratification

Chilling requirements in seeds. How they break dormancy

All About Winter Cold Hardiness

Important in determining the Northern Limits of a species:

• Timing of a bud burst in relation to spring temperatures (Spring frost are more limiting than winter because the plant has broke dormancy)

• Trade offs in flushing time