Data on trees from the Sierra Monitoring Project (SMP)/Ecoregional Biodiversity Monitoring (EBM) project (“project”). Collected within 0.2-acre (0.081 ha) plots in the northern Sierra Nevada ecoregion, numbers of stems in size categories, by species. Randomly located plots above 3000 feet elevation were selected, one per USDA Forest Service Forest Inventory and Analysis (FIA) hexagon, stratified in 6 elevation zones: 3-4k, 4-5k, 5-6k, 6-7k, 7-8k, and 8,000+ feet, and constrained to fall more than 100m from roads. In the publicly-accessible data, location data will be restricted to FIA hexagon centers: actual plot locations are within 2.7 km of these points; and elevation, slope, aspect and other environmental data are accurate to the true location. Collected during growing seasons 2009-2018 by California Department of Fish and Wildlife (originally Fish and Game), North Central Region, Resource Assessment Program; funded by a State Wildlife Grant from the US Fish and Wildlife Service; initiated by Armand Gonzales, directed by David Wright, Canh Nguyen, Stacy Anderson. Counties included are: Plumas, Butte, Yuba, Sierra, Nevada, Placer, El Dorado, Amador, Calaveras, and Alpine. Because of access constraints, plots fall primarily on public lands – several random points selected that fell on private lands had to be rejected due to denial of access. Plots that were excessively steep (>35 degree slope), too close to development, with unsafe access, or requiring more than 5 hours hiking time were rejected for safety or practical reasons. When plots were rejected, another random selection was made in the same hexagon from the same elevation stratum, if possible. Tree species’ stems smaller than 4 inches diameter-at-breast-height are contained in a separate dataset (SMP/EBM shrub data).