Historical Indigenous Land-Use Explains Plant Functional Trait Diversity

Human land-use legacies have long-term effects on plant community composition and ecosystem function. While ancient and historical land use is known to affect biodiversity patterns, it is unknown whether such legacies affect other plant community properties such as the diversity of functional traits. Functional traits are a critical tool for understanding ecological communities because they give insights into community assembly processes as well as potential species interactions and other ecosystem functions. Here, we present the first systematic study evaluating how plant functional trait distributions and functional diversity are affected by ancient and historical Indigenous forest management in the Pacific Northwest. We compare forest garden ecosystems - managed perennial fruit and nut communities associated exclusively with archaeological village sites - with surrounding periphery conifer forests. We find that forest gardens have substantially greater plant and functional trait diversity than periphery forests even more than 150 years after management ceased. Forests managed by Indigenous peoples in the past now provide diverse resources and habitat for animals and other pollinators and are more rich than naturally forested ecosystems. Although ecological studies rarely incorporate Indigenous land-use legacies, the positive effects of Indigenous land use on contemporary functional and taxonomic diversity that we observe provide some of the strongest evidence yet that Indigenous management practices are tied to ecosystem health and resilience.