Data and analysis files to perform analyses in LaManna et al. 2022 (Ecology Letters), "Tree species diversity increases with conspecific negative density dependence across an elevation gradient." The R code and data files (.RData) included in the ZIP file here run analyses from LaManna et al. "Tree species diversity increases with conspecific negative density dependence across an elevation gradient." The data are publicly available at https://andrewsforest.oregonstate.edu/data. We respectfully request that you cite our paper when using this analysis code. If you desire to use the data in publication, please contact us for permission. In addition to citing the LaManna et al. paper above, please also use the following citation if using the data provided here: Franklin, J., Bell, D.M. & Shaw, D.C. (2021). Long-term growth, mortality and regeneration of trees in permanent vegetation plots in the Pacific Northwest, 1910 to present, ver. 16. Environmental Data Initiative. This paper is currently under review – more detailed instructions for using the data will be added here prior to publication of the paper. Thank you! Instructions for use of code: For all analyses, make sure all files included in the zip file are in your R working directory. For species richness analyses, open "HJA_LaManna_RefStand_Species_Richness_Data.RData" and run the R code: "HJA_LaManna_RefStand_Species_Richness_Analysis_Jan_2022.R". For survival analyses, begin by opening "HJA_LaManna_RefStand_Survival-Growth_Data_Prep.RData" and run one of the "HJA_LaManna_RefStand_ExpSurvival_Analyses_Jan_2022...R" files. For growth analyses, begin by opening "HJA_LaManna_RefStand_Survival-Growth_Data_Prep.RData" and run one of the "HJA_LaManna_RefStand_Growth_Analyses_Jan_2022...R" files.