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<br />~) <br /> <br />Management Situation byRevision Topic <br /> <br />s~ ) <br /> <br />The composition of plant communities changes as soil characteristics change. The plant community <br />composition expressed on a shallow, rocky soil will be very different from the plant community <br />composition expressed on a deep, loamy soil. Generally, the shallow soil cannot hold as much water <br />as the deeper soil. <br /> <br />Climate has a strong impact on plilnt community composition; for example, envision two areas on a <br />lawn receiving vastly different amounts of precipitation. If one stops watering half of a bluegrass <br />lawn in the San luis Valley, the bluegrass community will die and be replaced by a weedy plant <br />community that does not need artificial watering. Climate characteristics such as temperature, <br />precipitation, and humidity have a strong influence on plant community composition. <br /> <br />Animals are another important influence on plant community composition. Animals select and <br />remove certain plants which changes the composition of plant communities over time. <br /> <br />,., Another important determinant of plant community composition is the flora of an area. The flora is <br />essentially a list of only those plants that have adapted to exist in an area. <br /> <br />Thus, plant community composition can only consist of those plants that are ecologically adapted to <br />live in an area. A plant community is complex and there are many interrelationships with the <br />environment that allow the community to exist in space and through time. <br /> <br />Plant Communitit'J6 and V~trt;ation Zont'J6 <br /> <br />The first plants to inhabit bare ground are called pioneers. These picneer species make the site <br />slightly more hospitable for another group of plants to establish. This sequence continues until a <br />stable plant community is maintained and is not replaced by another plant community. The <br />sequence of one plant community replacing another through time is called plant succession. A <br />climax plant community is the result of. plant succession over time. <br /> <br />The RGNF exhibits a variety of plant communities. Plant communities that maintain their population <br />sizes or regularly fluctuate around a stable equilibrium at climax are termed 'plant associations' <br />(Daubenmire 1968). Plant associations are diagnostic of an area's potential vegetation at the Climax <br />phase of plant succession. Knowing the potential on a site is important because it is the most <br />meaningful integration of the environmental factors affecting vegetation. For example, a sprucelfir <br />climax may experience a severe burn. The burned stand may be dominated by grasses and forbs for <br />the next several yeilrs. Eventually, aspen may begin appearing on the site. In 30 to 40 years, spruce <br />may begin appearing on the site. One hundred years after the burn, the stand may be dominated by <br />mature aspen with scattered, young Engelmann spruce. It may then take an additional 100 to 200 <br />years for the stand to appear like it did before the burn. Having an idea of site potential and some <br />idea of the possible plant communities that may occur through plant succession provides options for <br />changing plant diversity. <br /> <br />There are a variety of plant jIIssociations on the RGNF. A list of some prominent plant associations is <br />shown in Table 11I-5. The vegetation zones are presented from the highest elevations to the lowest <br />elevations on the RGNF. The most extensive forested plant association is the subalpine fir - <br />engelmann sprucelRocky Mountain whortleberry type. Since most of the forest types ,are in mature <br />structural stages (Table 11I-4), many forest plant communities are in a late seral stage (a transitional <br />community in plant succession). <br /> <br />11I-19 <br /> <br />(0"')430 <br />.~ v"" '- <br />