Trees are an integral part of the Preserve ecosystem, performing multiple functions. For example, the root systems of trees enhance soil development and increase soil permeability, making it easier for water to move through the soil. The extensive root systems also help to hold soil in place, preventing soil and streambank erosion.
“To plant trees is to give body and life to one's dreams of a better world.” – Russell Page
Another function is the formation of organic matter on the soil surface from leaf litter, which creates a microhabitat for small animals and cycles important nutrients. As explained in the benefits section, trees can act as a natural filter, helping to improve air and water quality.
Finally, a key role of trees is providing habitat for numerous animals, including the golden-cheeked warbler.
The composition of tree species in an area depends on the local topography and availability of water. Riparian areas, which are lowlands found along creeks and rivers, are hosts to many tree species, especially those requiring a relatively large amount of water and deeper soils. Often, these species are mostly deciduous, meaning they lose their leaves in the winter. Common riparian species include pecan, black willow, hackberry, sycamore, bald cypress, and cottonwood.
In upland areas, tree species are a more drought-tolerant mix of deciduous and evergreen trees, which retain their leaves year round. Common upland species include Ashe juniper, live oak, Spanish oak, shin oak, escarpment black cherry, bigtooth maple, and cedar elm. The oak-juniper woodlands found in upland areas serve as prime habitat for the golden-cheeked warbler, as well as the insects it feeds upon.