In a forest shorter trees do not survive as well as trees that reach the top of the canopy. why is this the case?

The reason why in forests shorter trees do not survive as well as trees that reach the top of the canopy, would be: light distribution and access to sunlight.

Explanation:

It must be remembered that sunlight is a vital element for plant survival; without it, photosynthesis cannot take place, or will not be as efficient as it would be if there was full access to sunlight. Sunlight activates the electrons on clorophyll and with that a plant is able to produce ATP, which is the basic energy-producing unit in any living cell.

As such, in dense forests where we have tall and shorter, trees, those that reach the highest point of the canopy have access to most of the sunlight, while the shorter ones have to make do with whatever filters through the branches of the others. Thus, by not having as much access to sunlight, their photosynthetic processes are not as efficient. Those that adapt to lesser amounts of light, will survive, but the others won´t.

sand 60

clay 10

silt 30

sandy loam should be dominated by the sand. as the amount of sand increased, the amount of slit needed to anchor the plants' roots to the sand will also be increased. even though the amount is very little, 10% part of clay is still necessary for proper oxidation.

not sure if this is what you'r looking for eubacteria and archaebacteria