Effects of single- vs mixed-species restoration planting on biodiversity: A systematic review

Abstract

Tree planting is expected to play a major role in achieving the restoration goals set globally to mitigate the impacts of climate change and to promote biodiversity and ecosystem services provision. However, the effectiveness of tree planting can vary depending on the contexts and methods employed. While there is growing evidence supporting the benefits of mixed-species planting for biodiversity, a comprehensive quantitative analysis of this knowledge is currently lacking. Moreover, specific taxonomic groups may respond quite differently to tree diversity at different spatial scales. To address this knowledge gap, we are conducting a systematic review to examine the effects of mixed vs pure planting on biodiversity. Our aim is to identify both global and regional patterns in the response of biodiversity to mixed planting, considering overall biodiversity as well as specific taxonomic groups. Through a systematic search employing several search engines, we initially retrieved 6,374 studies potentially addressing our research question. Based on title and abstract we preliminarily selected 178 relevant field studies. These publications will undergo further selection through full-text assessment, considering their experimental design, the type of analysis conducted, and the format of the data provided. From the final pool of studies, we will extract data that allow us to conduct meta-analyses of experimental comparisons between mixtures and monocultures. In addition to identifying overall patterns in biodiversity responses, we will examine variations across different regions, climates, and ecological and management conditions. These analyses will provide insights into the underlying processes that drive the effects of mixed planting on biodiversity, and will allow us to offer case-specific recommendations for management practices involving restoration planting.