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Natural Site Conditions and their
Effects on Establishment in
Grassland Restoration 1
Margaret Livingston 2
Factors influencing establishment of three native species of grass, Arizona cottontop, plains
lovegrass, and bush muhlenbergia were investigated. Natural habitats of these grasses were
examined for conditions favorable to these species. From these observations, experimental
plantings were established to test the emergence and establishment of these grasses, and some
influences of associated species were determined.
Differences in germination requirements between bush muhly and plains lovegrass were evident
and emphasized the importance of coordinating plantings with natural rainfall patterns. Seed
retrieval studies revealed bush muhly germinates quickly but seedlings die if soil moisture is not
replenished. Lovegrass exhibits variable dormancy and may germinate up to three years after
planting. In areas with a summer monsoon season, the rainfall pattern in August provides the most
reliable time for plantings of warm season native grasses. Mulch provided the best microhabitat for
establishment of these species, compared to small rocks or furrows, by lengthening the time period
that soil moisture was available to seedlings. A layer of mulch may also reduce germination of
weedy or aggressive species such as Lehmann 1S lovegrass, which has a light requirement for
germination.
Characteristics of sites where these species were established in association with other species
were examined, and differences between species were evident. Arizona cottontop was versatile,
and plants were found either in the understory or in open areas. In some sites, plains lovegrass
was more dense in the open, but in other sites, there was no difference in density between full sun
and understory habitats. Bush muhly was always found in greater concentration under canopies
provided by mesquite, cholla or creosote, and may choke out creosote in some sites.
Although abiotic site characteristics may appear favorable for seeding a particular species,
nearby aggressive species may choke out the desired plant. Land managers must determine ways
to control invading species for successful establishment of native plants. Establishment is a lengthy
process. Seeded species may remain dormant for several seasons or migrate to microsites that
meet their requirements. Irrigation, or other alteration of natural conditions, may provide microsites
suitable for native plants that are not usually able to establish in the area.
1
2
Summarized by Linda Elliott, Arizona State University
Landscape Architecture , School of Renewable Natural Resources, University of Arizona,
Tucson, AZ.
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