rade) with latitude for each of our planetary models.
Earth equivalent biotic zones have been colored into the chart showing the migration of plant life related to APST.
The temperatures given in the table were calculated as follows:
Example #1: 140ºF (hot planet’s APST) – 68ºF (Earth’s APST) = 72ºF difference (on hotter planet)
Therefore, 72ºF hotter (in general) + 81ºF at Earth 0º latitude (equator) = 153º F at 0º latitude (equator) on hot ASPT planet.
Example #2: 68ºF (Earth’s APST) – 32ºF (cold planet’s APST) = -36ºF cooler difference (on cooler planet).
Therefore, -36ºF cooler (in general) + (-4ºF on Earth at 70º latitude) = -40ºF at 70º latitude on the cold planet.
Look across the top of the Biotic Zone Table to locate 113ºF, then read down the column to find the approximate surface temperature at a given latitude. On a planet with an APST of 113ºF, the equatorial temperature would be about 126ºF, at 60º latitude it would be a warm 80ºF and a cool 41ºF at 70º latitude.
Drawn to overlay the preceding table are the color coded, approximate temperature and latitude boundaries, of the various biotic communities found on Earth. I’ve extended the APST range an additional 15ºC on either side of the conditions used in this study to demonstrate the serious deterioration of the planets habitability, see double blue and double red verticle lines toward either side of the chart.
In the column at far right, Earth’s APST (average planetary syrface temperature) and general biotic conditions per latitude have been included for comparison.
Note that the biotic community we are accustomed to on Earth, would be seen to shift toward the planets equator with a reduction in the average planetray surfave temperature; conversely, the biotic zones would shift toward the poles with an increase in APST.
In order to better understand the migration of biotic zones and the general climate of our model planets, I’ve included the illustrations below showing and equatorial and polar view for each 15ºC change in APST within the SRAPO filter parameters. An Earth model has been included for comparative reference.
Model illustrations on the left, provide an equatorial view of the planet with latitudes shown on the extreme left and temperatures on the right.
The models on the right, are shown in a polar view. The numbers entered above the pole are latitude and number below are the average temperatures for the given latitude.
Environmental Limiting Factors & The Plant Community
The planetary models we looked immediately above, have no axial inclination, we were determining the average temperature for a latitude; the length of the day to night cycle made no contribution. The parent star will rise and set in the same locations daily. Each day at local noon, the sun will have risen to it’s highest point in the morning sky and will begin its move lower in the afternoon sky. The elevation the sun rises to above the horizon al local noon will depend on ones latitude on the planetary surface.
On a planet with no axial inclination and 0ºC APST, plants in the equatorial zone, below 25º latitude, would be exposed to nearly perpendicular sunlight at local noon.
On planets with0 to 30ºC APST, most of the plant communities exist below 60º latitude. In these locations, the noon sunlight comes from a position relatively high in the sky. This results in the tropical and cool forest developing ‘ vertical light gathering stratification’. Hence we would find fungi located in the lower strata, rising above the fungi would be the shade lovers, then the shade tolerant and finally a canopy of sun seekers.
On 0º axial inclination planets, with 45ºC to 60ºC APST, the majority of the plant community exists above 45º latitude. Under these conditions, the tropical and cool forest would tend to develop ‘horizontal light gathering stratification’. On the equatorial side of the forests reaching deeper and deeper into the hotter zones, plants would decrease in size or biomass, attempting to adapt to extreme temperatures. On the polar side of the forests, plant life would again decreas