Functional diversity affects tree vigor, growth, and mortality in mixed-conifer/hardwood forests in California, U.S.A, in the absence of fire

•Stand functional diversity influences vigor and growth in California tree species.•Species-specific effects on vigor and growth range from positive to antagonistic.•Tree size modifies diversity effects on vigor, growth and mortality for most conifers.•Tree mortality is unresponsive to functional diversity, except in true firs.•Forest restoration will benefit from consideration of functional diversity.