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). Three parallel transects (2.7 km in length) run from the middle of the College Playa up into the foot of Mt. Summerford. The Control transect is to the west, the Treatment transect is to the east side of the Control transect, and the Alternate Control is to the east of the Treatment transect. Each transect is 30 meters wide with a 45 meter buffer zone between each transect. The Treatment transect was treated annually until 1987 with NHNO3 in a concentration equal to 10g N/m2. The station markers occur at 30 meter intervals along each transect. Perpendicular to each transect and crossing at each station marker is the 30 meter plant line intercept transect. Biomass of annual and perennial forbs and grasses was obtained from a one meter quad selected at random just downslope from each of 6 5-meter segments of the 30 meter plant line transect located perpendicular to the transect station marker. Data presented here is for the control and treatment transects. This study is complete.
This data on annual herbaceous plants was measured on Jornada grasshopper study plots located on the east bajada of the Dona Ana Mts. Three plots were situated on the bajada parallel to and 200m south of the LTER transect. Two additional sets of three plots were located 5km and 10km south of the LTER transect. Each plot was composed of two 50m belt transects, each divided into ten 5m2 quadrats. Annual plants were measured in the NE 1m2 of each quadrat, once in May, July and September in 1983, 1984 and 1985. All individuals of each species were counted and measured. A mean diameter, height, and the total number of individuals/1m2/quadrat were recorded. This study is complete.