ture range of 4ºC to 32ºC (39ºF to 89ºF) with an average of 23ºC (73ºF). The Arid desert has a hot, dry climate and is found to register the planets hottest surface temperatures. Plant life which has adapted to the dry, hot climate display biological adoptions for water collection and retention. On the hottest planets, many desert plants may display reverse phototropism; an hour after the sunrises, the plant may close its leaves, only to reopen them an hour or so before sunset. Succulent plants would have either a small leaf or no leaf at all, with photosynthesis occurring through the plant stem, as in the Barrel cactus and Saguaro cactus. The bulk of the trunk in these plant’s are composed of water storage cells; while the volume of the shoot is large, the surface area is small. This results in a large storage area for the areas biologically limiting factor, water, and a relatively small area from which they can lose their precious liquid reserves.
Non succulent plants will be modified with leathery leaves, thick cuticle layers on the outer surfaces of their leaves, they may have the ability to fold and curl, also leaves will likely be small. An example of a plant displaying many of these characteristics is the Creosote bush found commonly in the US southwestern arid desert.
In arid deserts, both succulent and non succulent plant species would have extensive root systems for water collection and potentially as locations for water storage.
Chemical inhibitors may also be used to maintain territory. This would result visually, in a more or less even spacing of the plants across the desert.
Other plants which have adapted to the Arid Desert might undergo their entire life cycle in that brief period when moisture was available. These ‘annuals’, with their fast growing shoots would die after the end of the moist season, leaving their seeds and/or a viable root system to lie dormant until the next moist period.
Animal life in the Arid Desert would tend to be either the small burrowing variety or larger, but thin. Due to the extreme temperatures, large animal life would have small body volume to large surface area ratios.
In these climatic conditions, both plant and animal life will have made specialized adoptions to reduce water loss; these adoptions may be biological or by technique or both.
Prairie & Grasslands
The condition of a temperate climate coupled with erratic and limited rainfall can extend grassland communities from the equator to near the polar region. On Earth, the grasslands have an annual precipitation rate that falls between 25% (10 inches) and 75% (30 inches) of the planets average. These areas are typified by small short lived plants, mainly annual and perennial herbs, relatively little rain, good fertile soil and numerous large herbivores.
In temperate regions on alien worlds which receive similar precipitation, we might expect to find similar types of biological adoptions. We might also expect to find such regions under agricultural use as fields or pasture amongst intelligent species.
While the plants and animal living in these zone will certainly look exotic, we will understand from their distribution and general adaptations to the limiting factors in the environment that they fill the same or similar roles in the ecology of the communities in which they live.
Cool Forest The temperate forest regions of Earth’s mid latitudes are extremely complex in their makeup and adoptions to temperature and moisture availability. Across broad regions of our own planet, the cool temperate forest experience temperatures ranging from -34ºC to 27ºC (-29ºF to 81ºF) with an average of 3ºC (37ºF) and precipitation rates of 10 to 60 inches per year.
The ability of a plant to survive freezing temperatures is called ‘frost resistance’, this ability varies widely among different species and is normally seasonal.
On cool and mild APST planets with low rates of axial inclination, frost resistant species would be found primarily in the mid to higher latitudes. As we encounter increased rates of axial inclination, frost resistance