Vegetation structure at a grassland-shrubland ecotone: Biotic versus abiotic factors leading to shrub invasion

TitleVegetation structure at a grassland-shrubland ecotone: Biotic versus abiotic factors leading to shrub invasion
Publication TypeConference Paper
Year of Publication1998
AuthorsHochstrasser T., Coffin D.P.
Conference Name83rd Annual Meeting, Ecological Society of America
Date Published1998
Conference LocationBaltimore, Maryland
ARIS Log Number089569
AbstractThe invasion of serai-arid grasslands in the Southwestern US by shrubs is usually attributed to the complex interactions between grazing, climate, and fire. However, different soils may have different sensitivities to invasion, such that shrubs would be confined to certain sites. Our objective was to evaluate the relationship between vegetation structure and variation in soil characteristics for a 500m x l00m grid across a grassland-shrubland transition zone. Soil samples to a depth of 30cm were taken from 10 x l0m quadrats and cover of the dominant species as well as importance of disturbance was assessed. Shrub cover was higher when die soil was shallower on a l0 xl0m scale. Vegetation and soil sampling around individual plants revealed that the probability of germination of shrub seedlings was higher within the canopy area of the shrub than it was in the interspaces, indicating that the microclimate and soil were more favorable around the adults. These results suggest that the shrub invasion took place mainly on soil less favorable for grassland. These favorable microsites may support a source population of shrubs for further spread in the landscape.