Not All Shrubs are Equal: The Outsized Ecological Consequences of Ericaceous Shrub Encroachment on Communities and Ecosystem Processes

Aadia Moseley-McCloud , Aimee Classen

Shrubs are functionally important and found across various ecosystems. Over the past few decades, shrubs have been expanding their ranges and encroaching within grassland, temperate, boreal, and tundra ecosystems. Because of this range expansion and their functional importance, shrubs are altering abiotic factors, biotic interactions, and ecosystem processes. However, shrubs of the Ericaceae family are functionally distinct and their traits have outsized effects on ecosystems. Over the past few decades, several reviews have detailed the expansion of shrubs and their impacts on communities and ecosystem processes, but shrub species have been pooled, which has masked the unique functionality of, specifically, ericaceous shrubs. In this review we aim to (1) synthesize the existing literature on the effects of ericaceous shrub encroachment on abiotic factors, plant and soil microbial communities, and ecosystem processes, (2) argue that the distinct traits, and thus functionality of ericaceous shrubs is stronger than what the pooled literature currently reflects, and (3) identify key literature gaps that should be addressed in future research. This review highlights that considering species identity (e.g., ericaceous or non-ericaceous) in future shrub encroachment studies and reviews is key for fully understanding the degree to which these species are affecting ecosystems.