Flora in the ground cover is regulated, at least in part, by the canopy cover; hence different associations of pinyon-juniper woodland and each of the stands mentioned above have different plants, or a different distribution of the same kinds of plants, in their ground cover.
Units A, B, E, and parts of D and G in the western third of the grid are in pinyon-juniper woodland ([Fig. 5]). A relatively pure understory of Poa fendleriana (muttongrass), is typical of such woodland on the middle parts of the mesas. Woodland on the western third of the grid differs somewhat in that, when the area occupied by each plant is considered, Artemisia tridentata is codominant there with Poa fendleriana. As far as individual plants are concerned, Poa far outnumbers Artemisia. The next most abundant plants in the ground cover are Solidago petradoria (rock goldenrod), Chrysothamnus depressus (dwarf rabbitbrush), and Penstemon linarioides (penstemon), in that order.
In unit E there is a large depression, about 200 by 60 feet, created by removal of soil ([Fig. 8]). Artemisia nova grows there, and pioneering plants adapted to early stages of succession are present.
A zone of woodland, where Artemisia nova replaces A. tridentata as an understory codominant with Poa fendleriana, borders the pinyon-juniper-muttongrass community to the east. The next most abundant plants in the ground cover are Solidago petradoria, Penstemon linarioides and Comandra umbellata (bastard toadflax). Koeleria cristata (Junegrass) is as abundant as Comandra, but probably is less important as a source of food for mice.
A small strip of the pinyon-juniper-muttongrass community with an understory of Artemisia nova and Purshia tridentata (bitterbrush) adjoins the above area to the east (Figs. [5]-[8]). Solidago petradoria, Balsamorrhiza sagittata (balsamroot), and Comandra umbellata are the three most abundant plants in the ground cover. The terrain slopes eastward from this zone into a large drainage.
Fig. 5: Diagram showing the major associations of understory and overstory vegetation in a trapping grid located south of Far View Ruins, Mesa Verde National Park, Colorado.
As the forest floor begins to slope into the drainage, the ground becomes rocky and shrubs assume more importance in the understory. Most of this shrubby zone is on the slope; on the western side this zone abuts pinyon-juniper woodland, and on the eastern side is bordered by Artemisia tridentata in the sandy bottom of the drainage. Shrubs become more abundant and pinyon and juniper trees become less abundant as one approaches the drainage. In the vegetation maps, this brushy zone is delimited on the east by a heavy line passing vertically through the middle of the grid (Figs. [5]-[8]). The codominant shrubs in the understory of this zone are Amelanchier utahensis, Artemisia nova and Purshia tridentata. The three most abundant plants on the ground are Artemisia ludoviciana, Chrysothamnus depressus and Penstemon linarioides.