This dataset includes plant species cover and height data measured in 1 m x 1 m quadrats at several sites and experiments under the Sevilleta LTER program. Quadrat locations span four distinct ecosystems and their ecotones: creosotebush dominated Chihuahuan Desert shrubland (est. winter 1999), black grama-dominated Chihuahuan Desert grassland (est. winter 1999), blue grama-dominated Plains grassland (est. winter 2002), and pinon-juniper woodland (est. winter 2003). Data on plant cover and height for each plant species are collected per individual plant or patch (for clonal plants) within 1 m x 1 m quadrats. These data inform population dynamics of foundational and rare plant species. In addition, using plant allometries, these non-destructive measurements of plant cover and height can be used to calculate net primary production (NPP), a fundamental ecosystem variable that quantifies rates of carbon consumption and fixation. Estimates of plant species cover, total plant biomass, or NPP can inform understanding of biodiversity, species composition, and energy flow at the community scale of biological organization, as well as spatial and temporal responses of plants to a range of ecological processes and direct experimental manipulations. The cover and height of individual plants or patches are sampled twice yearly (spring and fall) in permanent 1m x 1m plots within each site or experiment. This dataset includes core site monitoring data (CORE, GRIDS, ISOWEB, TOWER), observations in response to wildfire (BURN), and experimental treatments of extreme drought and delayed monsoon rainfall (EDGE), physical disturbance to biological soil crusts on the soil surface (CRUST), interannual variability in precipitation (MEANVAR), intra-annual variability via additions of monsoon rainfall (MRME), additions of nitrogen as ammonium nitrate (FERTILIZER), additions of nitrogen x phosphorus x potassium (NutNet), and interacting effects of nighttime warming, nitrogen addition, and El Niño winter rainfall (WENNDEx). To build allometric equations that relate biomass to plant cover or volume, a separate dataset of selectively harvested plant species is provided in "SEV-LTER Plant species mass data for allometry." Together, these datasets produce “SEV-LTER Plant biomass all sites and experiments” using the scripts posted with that dataset. Data from the CORE sites in this dataset were designated as NA-US-011 in the Global Index of Vegetation-Plot Databases (GIVD). Data from the TOWER sites in this dataset are linked to Ameriflux sites: ameriflux.lbl.gov/doi/AmeriFlux/US-Seg and ameriflux.lbl.gov/sites/siteinfo/US-Ses.