%0 Journal Article %J Journal of Vegetation Science %D 1998 %T Recruitment of Quercus agrifolia in central California: the importance of shrub-dominated patches %A Callaway, R. M. %A Davis, F. W. %K aerial photo interpretation %K Angiospermae %K Biochemistry and Biophysics–Growth %K Biochemistry and Biophysics–Reproduction) Angiosperms Dicots Plants Spermatophytes Vascular Plants Patch Dynamics Shrub-Dominated Patches Vegetation Science California (USA %K coast live oak %K Differentiation) (Plant Physiology %K Gaviota State Park Fagaceae (Ecology Environmental Biology–Plant) (Plant Physiology %K Nearctic region) Quercus agrifolia [Coastal live oak] (Fagaceae): recruitment Fagaceae: Dicotyledones %K North America %K Plantae aerial photograph time sequence comparison: field method %K Spermatophyta %K time series %X Many perennial plants strongly enhance the survival of seedlings of other species. We studied patterns of long-term recruitment of Quercus agrifolia (Coastal live oak) associated with shrub-dominated communities by counting Q. agrifolia recruits on a time sequence of historical aerial photographs and comparing recruitment among mapped patches of coastal sage scrub, chaparral, and grassland in an 1120-ha landscape. Because we could not identify new recruits in existing woodlands with aerial photographs, we studied the recruitment of Q. agrifolia in this vegetation type indirectly by comparing population size structures and the spatial relationships between shrubs and recruits among woodlands that varied in understory community type. At the landscape scale, recruitment was higher in coastal sage scrub vegetation than predicted by the extent of its coverage, commensurate with the spatial coverage of chaparral, and very low in grassland. Recruitment within woodland communities also varied considerably. In woodland communities on sheltered, north-oriented topography with understories dominated by shrubs, there were large numbers of small Q. agrifolia, and recruits were not significantly spatially associated with shrubs within plots. In woodlands with herbaceous understories there were few individuals in the small size classes, and recruits were strongly spatially associated with shrubs within plots. Woodlands with shrub-dominated understories have population structures that appear to be stable, but woodlands with herbaceous understories exhibit size structures associated with declining populations. Quercus recruitment into shrub-dominated patches corresponds with previous documentation of facilitative relationships between shrubs and oak seedlings, and suggests the occurrence of an unusual form of patch dynamics in these landscapes. %B Journal of Vegetation Science %V 9 %P 647-656 %G eng %0 Journal Article %J Ecology %D 1993 %T Vegetation dynamics, fire, and the physical environment in coastal Central California %A Callaway, R. M. %A Davis, F. W. %K Gramineae Compositae Fagaceae (Ecology Environmental Biology–Plant) Plants Vascular plants Spermatophytes Angiosperms Monocots Dicots Grassland Coastal Sage Scrub Chaparral Oak Woodland Community Grazing Climax Community Landscape Ecology Markov chain m %X Current concepts of vegetation dynamics include that of the shifting landscape mosaic, but evidence for shifting mosaics in disturbed and undisturbed systems is primarily based on negative spatial relationships among adults and recruits, and not on measurements of actual shifts over time. We used aerial photographs to measure transition rates as evidence for mosaic shifts among grassland, coastal sage scrub, chaparral, and oak woodland communities in central coastal California between 1947 and 1989. In unburned plots without livestock, transition from grassland to coastal sage scrub was 0.69% per year, coastal sage scrub to oak woodland was 0.30% per year, and oak woodland to grassland was 0.08% per year. These transition rates, considered together, indicate that vegetation patterns may be dynamic on landscapes dominated by these communities. In burned plots without livestock, and in unburned plots where livestock were not excluded, transition rates were lowers, except for the conversion of oak woodland to grassland. In burned plots, a high rate of transition of coastal sage scrub to grassland was measured. Markov chain models predicted much less directional change in community proportions in either grazed or burned conditions than in ungrazed, unburned conditions. Some transition rates varied with substrate and topographical position, indicating that fire, grazing, and the physical environment interacted to determine direction and rate of vegetation change. Variation in transition on different substrates suggests that only portions of the vegetation of these landscapes may be dynamic, with some patches in certain combinations of environment and disturbance that change rapidly, and other patches that remain static as edaphic or topographic climax communities. %B Ecology %V 74 %P 1567-1578 %G eng