Growth and nutrient content of herbaceous seedlings associated with biological soil crusts

摘要

Biological soil crusts of arid and semiarid lands contribute significantly to ecosystem stability by means of soil stabilization, nitrogen fixation, and improved growth and establishment of vascular plant species. In this study, we examined growth and nutrient content of Bromus tectorum, Elymus elymoides, Gaillardia pulchella, and Sphaeralcea munroana grown in soil amended with one of three levels of biological soil crust material: (1) a low-fertility sand collected near Moab, Utah; ( 2) sand amended with a 1-cm top layer of excised soil crust; and ( 3) crushed crust material. In addition, all plants were inoculated with spores of the arbuscular mycorrhizal fungus, Glomus intraradices. Plants were harvested after 10 weeks growth, dried, weighed, and leaves were ground for nutrient analysis. Three aspects of root architecture were also quantified. Soil crust additions significantly affected nearly all variables examined. Both above- and below-ground vegetative biomass were significantly increased in the presence of crust material. Similarly, reproductive tissue of the three species that flowered was greatest in the crushed-crust medium. The effect of soil crust additions is likely due to the increased nitrogen content of the crusts. Nitrogen tissue content of all four species was greatly enhanced in crusted soils. All species showed a decline in root/shoot ratio and specific root length with crust additions, indicating a shift in plant allocation pattern in response to improved soil fertility. These data support other studies suggesting that soil crusts have a positive effect on the establishment and growth of associated vascular plant species.