Transect plant line intercepts - percent cover by species

Average percent coverage of each plant species per 5-meter segment
along a 30-meter line intercept perpendicular to each of 91 stations
on each of the three LTER-I permanent transects. Data consists of
week number, transect, station number, species, carbon reduction
pathway, habit, form, and average percent cover. It is sorted by
transect, station number, then plant species.

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. Following January 1, 1987, spring line-
intercepts will only record cover of annual species. All perennial
cover data will be limited to fall samples. Both annuals and perennials
are measured during the fall. Measurements were made biannually from
1982 - 1988. After this they are measured every 5 years. Annuals are
measured through 1998; however, after this only perennials are measured
and only in the fall. 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.

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.