Yes the volume of air largely affected by animals is much obviously much smaller and could not be considered a layer. The phytosphere on the other hand has potential to extend beyond 400 feet above the surface.
The phytosphere is the layer of the earth's atmosphere closest to the crust and directly affected by the presence of plants. A sub layer of the troposphere, it is the thinnest layer of the earth's atmosphere, varying in thickness from around 300 feet above the ground down to a few centimeters, in some areas disappearing altogether. The phytosphere is differentiated from the troposphere by its unique properties. The word phytosphere is also used to describe zones where specific plants or plant types occur.
The composition of the air in the phytosphere can be slightly different from the surrounding troposphere as gases and water vapor are released and absorbed by plants. The phytosphere is often more humid than the adjacent lower troposphere. The gas temperature can be slightly more stable than the lower troposphere as well. The flow of air is reduced by the bodies of plants and the sunlight is reduced by shading from plant bodies. In climates where the temperature drops below zero degrees Celsius for long periods, the phytosphere may only have seasonal significance.
"Phyto" or plant and "sphere" where first used to describe a layer of the earth's atmosphere by Dr. Jeffrey Hodgins when he discovered that the properties of the layer were far different from those of the troposphere especially when the surface wind speed was relatively slow and during the growing season in a given area. He determined that the word phytosphere should be used to describe the airmasses most affected by plants.