LTER-I Transect plant line intercept data. This data set is as transcribed (UNSORTED) from cassette tape with one intercept observation per record. Data consist of week number, transect, station, segment number, plant species, and length of species intercepted by line stretched between 2 rebar the length of the 30 meter plant line intercept transect. Measurements are made on 30-meter line intercept transects located perpendicular to each of 91 stations on each of the 2.7 km long Control, Treatment, and Alternate Control Transects established at the beginning of LTER-I. Each plant line transect is divided into 6 5-meter segments. Annuals are measured only in the first meter of segments 1, 2, and 3 and in the last meter of segments 4, 5, and 6. Perennials are measured for the full length of all segments. On March 19, 2000, an arson burn occurred of 2.5 acres of the upper grassland area on the Summerford bajada just below the powerline road. The area affected included portions of the LTER-I Transect Plant Line Intercept study that was begun in 1982. To evaluate the impact of the burn on those lines, the line intercepts were read for the upper grassland area extending from immediately above the creosotebush fringe to the base of Summerford Mountain. The stations measured were C73-C89, T75-T90, and X76-X91 (Control, Treatment, and Alternate Control, respectively). Measurements were made immediately after the burn, after the spring growing season, and after the fall growing season in 2000 only. In the initial sampling period, the burn area intercepted by the line was noted in the data set using a "species" code of BURN. BACKGROUND. In the spring of 1982, as part of the establishment of the Jornada Long-Term Ecological Research site in southern New Mexico, a 135 ha portion of a 1500 ha, internally drained, watershed was exclosed from grazing by domestic livestock. Prior to exclosure the watershed, as well as the rest of the Jornada basin, had been moderately to heavily grazed for the past 100 years. Concurrent with grazing, the vegetation had undergone a dramatic change from desert grassland, with an almost continuous cover of C4 perennial grasses, to isolated patches of the original grassland in a mosaic with desert shrub dominated plant communities (Buffington and Herbel, 1965). The exclosure lies along a northeast facing piedmont slope at the base of a steep isolated mountain peak, and covers a variety of component landforms from the foot of the mountain to the basin floor. This provided the opportunity to investigate the response of vegetation with respect to landscape characteristics as well as release from grazing.