Biology 141
Thinking about environmental variation and local ecological pattern.

K.E. Clifton

Lewis & Clark College

 

 

 

Separating the "environment" into two components: The "abiotic" and the "biotic".

Mostly we've talked about the abiotic

Considering local natural areas from an ecological perspective... e.g., Tryon Creek State Natural Area

1)    Think about the physical environment:

What is there? 

Sunshine, Water, Nutrients, Oxygen... we would expect life to be present

Is there pattern to the availability of these environmental variables? What influences them?

 

Orientation

Shade

Slope

Elevation (proximity to creek)

etc.....

 

A reminder that scientists, like most of the planet, use the metric system for measurments and statistics

An observation provides a "snapshot:" of conditions. What about more general patterns of climate not in space, but in time?

 

An archive of information on Portland's climate

 

Some data on Temperature:

 

The average temp here: Mean: 62.6 °F (17.0 °C)

 

Some stretches of extreme weather:

            Lowest temp: -3° F (-19.5°C; 1950) and only 6 days below zero in 125 years.

            38 days with min temp of below freezing (1949)

            19 days with MAX temp of below freezing (1930).  Also 12 days in 1957

What about heat?

            107° (41°C) max for July and Aug. 105° in Sept.  These are infrequent

Means are much more moderate:

 

 

What about Rainfall?

 

            Average: 36 inches/year (91 cm) mostly in Nov to March

 

            Max: 63.21 in 1996 (160 cm)

 

 

It is also quite variable on monthy and daily scales (max in 24 hrs: 2.61 (6.5 cm))

 

Wind

            Average: 8 mph

            Max recorded: 104 mph

            Max for months: Jan '51: 63, Feb '58: 68, Mar '63: 71, Apr '57: 63, Nov '61: 71, Dec '51: 74

 

What constraints do these conditions generate? 

 

What sort of Biome would you expect?  16-17°C and 90 cm of rain (Temperate forest (close to grassland). Remember our graph of Biomes vs rain and temperature? Look east of Portland (other side of the Cascades) and what do you see?

What kinds of organisms do we find?

 

Plants:

Trees: mix of evergreens and deciduous,

Shade adapted understory; annuals and some perennials

 

Animals

            Ectotherms

                        Amphibians

                        Reptiles

                        Fish

            Endotherms

                        Mammals (smaller ones may hibernate)

                        Birds (some migratory species)

 

Remember to think about how body size matters for these different animals and especially how surface area (4πr2 for a sphere) scales as a square function while volume (4/3πr3) scales as a cube function. This means that surface area to volume ratios decrease as an organism gets larger.

 

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