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California State Polytechnic University, Pomona (2018)

Factors Influencing Revegetation Efforts in the Mojave Desert : Field Studies and Meta-Analysis of the Morongo Basin and Joshua Tree National Park

Wagner, Marinna

Titre : Factors Influencing Revegetation Efforts in the Mojave Desert : Field Studies and Meta-Analysis of the Morongo Basin and Joshua Tree National Park

Auteur : Wagner, Marinna

Université de soutenance : California State Polytechnic University, Pomona

Grade : Master of Landscape Architecture 2018

Résumé
The Mojave Desert is threatened by a wide range of anthropogenic disturbances. This study examined the factors that influence revegetation efforts in the Mojave Desert ecoregion. The objectives were to determine influential existing conditions, biophysical, and anthropogenic factors, assess the effectiveness of various revegetation techniques, and comprehend vegetation succession following the revegetation of disturbed sites. Studies showed that research on the Mojave Desert was limited and focused to certain subregions. The south-central Mojave Desert, which comprises the Morongo Basin and Joshua Tree National Park, was especially limited in published research. Meta-analysis was used to determine the important variables, attributes, and indicators used to assess revegetation in the Mojave Desert. Ecological field methods, which included the belt-transect survey and soil testing, were used to monitor eight locations in the Morongo Basin and Joshua Tree National Park to determine key factors and the ways in which these sites were recovering. Data sets were analyzed to determine trends and biodiversity attributes including cover, density, and species richness. Ecological field studies indicated that revegetation was possible, but highly variable and slow for passive methods. After eleven years, one site that was revegetated with outplanted shrub species experienced an estimated increase 4.5 times that of the initial planting. Whereas, other sites saw moderate to limited recruitment or significant mortality of outplanted shrub species. Nonetheless, there was evidence of shrub establishment in both vertical and horizontal mulching of local decayed plant material. Ambrosia salsola was highly dominant across revegetation sites and Hilaria rigida was significantly abundant among reference sites. The meta-analysis revealed that variable existing conditions, soils, and herbivory had a significant impact on revegetation efforts. This study demonstrated the importance of synthesizing data and the need for more research on revegetation techniques and vegetation recruitment in the Mojave Desert.

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