Drivers of plant species richness and phylogenetic composition in urban yards at the continental scale
As urban areas increase in extent globally, domestic yards play an increasingly important role as potential contributors to ecosystem services and well-being. These benefits largely depend on the plant species richness and composition of yards.
We aim to determine the factors that drive plant species richness and phylogenetic composition of cultivated and spontaneous flora in urban yards at the continental scale, and how these potential drivers interact.
We analyzed plant species richness and phylogenetic composition of cultivated and spontaneous flora of 117 private yards from six major metropolitan areas in the US. Yard plant species richness and phylogenetic composition were expressed as a function of biophysical and socioeconomic variables and yard characteristics using linear mixed-effects models and spatially explicit structural equation modeling.
Extreme temperatures largely determined yard species richness and phylogenetic composition at the continental scale. Precipitation positively predicted spontaneous richness but negatively predicted cultivated richness. Only the phylogenetic composition of the spontaneous flora was associated with precipitation. The effect of lower temperatures and precipitation on all yard diversity parameters was partly mediated by yard area. Among various socioeconomic variables, only education level showed a significant effect on cultivated phylogenetic composition.
Our results support the hypothesis that irrigation compensates for precipitation in driving cultivated yard plant diversity at the continental scale. Socioeconomic variables among middle and upper class families have no apparent influence on yard diversity. These findings inform the adaptation of US urban vegetation in cities in the face of global change.
KeywordsPrivate gardens Socioeconomics Horticulture Homogenization Spatial autocorrelation Structural equation modeling
Research funding was provided by the National Science Foundation Macrosystems Biology Program in the Emerging Frontiers Division of the Biological Sciences Directorate and Long Term Ecological Research Program. The senior author was supported by the “Yard Futures” project from the NSF Macrosystems Program (EF-1638519). Data collection was supported by the “Ecological Homogenization of Urban America” project, funded by a series of collaborative grants from the NSF Macrosystems Program (EF-1065548, 1065737, 1065740, 1065741, 1065772, 1065785, 1065831 and 121238320); and additionally by grants from the NSF Long Term Ecological Research Program supporting work in Baltimore (DEB-0423476), Phoenix (BCS-1026865, DEB-0423704 and DEB-9714833), Plum Island (Boston) (OCE-1058747 and 1238212), Cedar Creek (Minneapolis-St. Paul) (DEB-0620652) and Florida Coastal Everglades (Miami) (DBI-0620409). We are grateful to the botanical field teams involved in yard sampling and data organization: BAL-Charlie Davis, Dan Dillon, Erin Mellenthin, Charlie Nicholson, Hannah Saunders, Avery Uslaner; BOS-Emma Dixon, Roberta Lombardiy, Pamela Polloni, Jehane Semaha, Elisabeth Ward, Megan Wheeler; LA-Aprille Curtis, La’Shaye Ervin; MIA-Bianca Bonilla, Stephen Hodges, Lawrence Lopez, Gabriel Sone; MSP-Chris Buyarksi, Emily Loberg, Alison Slaats, Kelsey Thurow; PHX-Erin Barton, Miguel Morgan.
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