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Utah State University (2020)

Effect of Biocrust Development on Establishment of Native Plants in a Salt Desert System

Owen, Merran

Titre : Effect of Biocrust Development on Establishment of Native Plants in a Salt Desert System

Auteur : Owen, Merran

Université de soutenance : Utah State University

Grade : Master of Science (MS) 2020

Résumé
Salt desert shrublands are semiarid, shrub-dominated ecosystems that inhabit salt- affected soils. In Great Basin salt deserts, exotic annual plants are invading and displacing native plants. Low plant productivity and slow population growth of native plants in these ecosystems makes them vulnerable to invasion and limits their ability to compete with invasive plants and return to a natural state. Active revegetation efforts, such as planting and direct seeding of native plants, are often unsuccessful for the same reasons. Biological soil crusts (communities of cyanobacteria, lichen, moss, microfungi and other microorganisms that live on the surface layer of the soil) are an important component of salt deserts and commonly occur in the interspaces between plants. Biological soil crusts may provide favorable places to target revegetation practices, as they can provide increased water and nutrients to vascular plants. Additionally, exotic annual species are less able to invade and dominate biological soil crusts. I tested how differing levels of crust development (the amount of cyanobacteria and other organisms) influence the effectiveness of two methods of planting native species : broadcast seeding and transplanting of greenhouse-grown seedlings. Experiments were done in a degraded salt desert shrubland in southeastern Idaho, on salt-affected soils. I evaluated planting techniques in areas of both high and low crust development. Treatment combinations were applied to three native grasses, Indian ricegrass (Achnatherum hymenoides (Roem.& Schult.) Barkworth.), squirreltail (Elymus elymoides (Raf.) Swezey), basin wildrye (Leymus cinereus (Scribn. & Merr.) √Å. L√∂ve) and one native forb, gooseberryleaf globemallow (Sphaeralcea grossulariifolia, (Hook. & Arn.) Rydb.). Plant survival, size and reproductive success were measured at different points in time for a year after planting. Broadcast seeding largely failed across all levels of crust development and species. Biological soil crusts improved the ability of spring-planted species, in a dry year, to survive through the first summer after planting. The survival of transplanted seedlings varied across species. This study demonstrates the greater success of transplanting as a method of native species establishment, and the benefits of high soil crust development in the initial establishment of transplanted seedlings during dry times.

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Page publiée le 24 octobre 2020