Print PageThe increase of large-scale disturbances to vegetation communities has ignited interest in rehabilitation efforts. One popular strategy is the application of seed mixes, thereby reestablishing plants more quickly than waiting for seeds to disperse naturally into large disturbed areas. This approach has a mixed record of success in desert regions, largely due to highly unpredictable precipitation patterns. Seeds that were broadcast over large areas after wildfires burned Mojave Desert shrublands during 2005 and 2006 had limited plant establishment in areas that received the lowest rainfall. Under the highly variable environmental conditions typical of deserts, the planting of nursery-grown stock with supplemental moisture may be an alternative, but this strategy has also had mixed success. We planted over 1,300 Nevada ephedra (Ephedra nevadensis) and over 4,500 blackbrush (Coleogyne ramosissima) at five burned sites in the northeast Mojave Desert which varied in soils, annual precipitation, and temperature. Seedlings planted in fall 2007 received one soil amendment (none, organic mulch, starch-based granular polymer, or slow-release irrigation gel) plus one watering treatment (none or monthly watering). Seedlings planted in fall 2009 received one soil moisture amendment (none, organic mulch, 2X mulch, or slow-release irrigation gel) based on results from the 2007 planting.
Results/Conclusions
Survival during one year for the early-colonizing ephedra was determined most strongly by site and whether a plastic cone or a cage was installed as protection from herbivores. Ephedra had high overall survival (87%), except at the coldest site where survival of plants with cages declined to 64%, and at the 2009 site where herbivore damage lowered survival to 45% after nine months. Blackbrush survival was most strongly controlled by soil amendment, watering, precipitation, temperature, pre-planting treatment, and whether a plastic cone or cage was installed. Survival of the late-colonizing blackbrush was 35%, less than half that of ephedra, and demonstrated a pronounced dependence on factors that increased soil moisture. Watering, addition of irrigation gel or mulch, and high cumulative precipitation all increased survival. Temperature had a less clear influence, with survival improving slightly only at the middle of the temperature range (23° C). Blackbrush plants that were pruned during their one year in the greenhouse had more than two times higher survival than those that were not pruned. Plastic cones improved survival compared with cages. Early-colonizing species are likely to have greater success for small-scale re-vegetation efforts in burned areas and require fewer resources than late-colonizing species such as blackbrush.
