title: Effects of topoclimatic complexity on the composition of woody plant communities.
abstract: Topography can create substantial environmental variation at fine spatial scales. Shaped by slope, aspect, hill-position and elevation, topoclimate heterogeneity may increase ecological diversity, and act as a spatial buffer for vegetation responding to climate change. Strong links have been observed between climate heterogeneity and species diversity at broader scales, but the importance of topoclimate for woody vegetation across small spatial extents merits closer examination. We established woody vegetation monitoring plots in mixed evergreen-deciduous woodlands that spanned topoclimate gradients of a topographically heterogeneous landscape in northern California. We investigated the association between the structure of adult and regenerating size classes of woody vegetation and multidimensional topoclimate at a fine scale. We found a significant effect of topoclimate on both single-species distributions and community composition. Effects of topoclimate were evident in the regenerating size class for all dominant species (four Quercus spp., Umbellularia californica and Pseudotsuga menziesii) but only in two dominant species (Quercus agrifolia and Quercus garryana) for the adult size class. Adult abundance was correlated with water balance parameters (e.g. climatic water deficit) and recruit abundance was correlated with an interaction between the topoclimate parameters and conspecific adult abundance (likely reflecting local seed dispersal). However, in all cases, the topoclimate signal was weak. The magnitude of environmental variation across our study site may be small relative to the tolerance of long-lived woody species. Dispersal limitations, management practices and patchy disturbance regimes also may interact with topoclimate, weakening its influence on woody vegetation distributions. Our study supports the biological relevance of multidimensional topoclimate for mixed woodland communities, but highlights that this relationship might be mediated by interacting factors at local scales.
authors.affiliation: Department of Integrative Biology, University of California, Berkeley, CA 94720, USA meagan_oldfather@berkeley.edu.
authors.forename: Meagan F
authors.initials: MF
authors.lastname: Oldfather
authors.affiliation: Department of Biological Sciences and Bolus Herbarium, University of Cape Town, Private Bag, Rondebosch 7700, South Africa.
authors.forename: Matthew N
authors.initials: MN
authors.lastname: Britton
authors.affiliation: Department of Integrative Biology, University of California, Berkeley, CA 94720, USA.
authors.forename: Prahlad D
authors.initials: PD
authors.lastname: Papper
authors.affiliation: Department of Plant Sciences, University of California Davis, Davis, CA 95618, USA.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Koontz
authors.affiliation: Pepperwood Preserve, 2130 Pepperwood Preserve Road Santa Rosa, CA 95404, USA.
authors.forename: Michelle M
authors.initials: MM
authors.lastname: Halbur
authors.affiliation: Pepperwood Preserve, 2130 Pepperwood Preserve Road Santa Rosa, CA 95404, USA.
authors.forename: Celeste
authors.initials: C
authors.lastname: Dodge
authors.affiliation: Water Resources Discipline, U.S. Geological Survey, Placer Hall, 6000 J Street, Sacramento, CA 95819, USA.
authors.forename: Alan L
authors.initials: AL
authors.lastname: Flint
authors.affiliation: Water Resources Discipline, U.S. Geological Survey, Placer Hall, 6000 J Street, Sacramento, CA 95819, USA.
authors.forename: Lorriane E
authors.initials: LE
authors.lastname: Flint
authors.affiliation: Department of Integrative Biology, University of California, Berkeley, CA 94720, USA Jepson Herbarium, University of California, Berkeley, CA 94720, USA.
authors.forename: David D
authors.initials: DD
authors.lastname: Ackerly
keywords: California; climatic water deficit; community analyses; oak woodlands; topoclimate; woody vegetation