Grassland Vegetation Line-Intercept Transects at the Sevilleta National Wildlife Refuge, New Mexico (1989 - 2013)
In 1989, line-intercept transects were installed to evaluate temporal and spatial dynamics across vegetation transition zones. Currently, a 400m transect is sampled at a grassland site (Deep Well) which is dominated by Bouteloua eriopoda (black grama) and, near the southern end of the transect, B. gracilis (blue grama). A second grassland site (Five Points), dominated by B. eriopoda and, to the south, Larrea tridentata (creosote), is also sampled. Both sites are sampled twice a year, in May/June and September/October, and measurements are taken at a one-centimeter resolution. The biannual sampling protocol detects potential responses in both cool and warm season plants as well as pre- and post-monsoon dynamics. Several transects have been discontinued and data archived within SEV200.
Preparing Transects for Measurement:
A 100m measuring tape is unrolled and affixed to permanent pieces of rebar hammered into the ground at each of the four segments of a 400 m transect. For example, a tape is attached to the 0 meter (north) rebar stake and run to the 100 meter (south) stake. The tape is stretched as tightly as possible to get the straightest line. Windy days should be avoided as the wind moves the tape and results in inaccurate data.
Crew members work independently, each doing a 100 m segment simultaneously. Microcassette recorders and standard microcassettes are used to record the data. File names should be written on the cassettes as "fp" (Five Points), "dw" (Deep Well), or "dwb" (Deep Well-burn) for the location, followed by the transect number, date, and initials of the recorder. An introductory statement is recorded on the cassette (e.g. "It's May 9, 2099, Joe Smith recording at Deep Well Transect 2."
Each species or substrate (i.e., bare soil, litter) that intersects the tape and occupies at least one centimeter is recorded whether rooted beneath the tape or not. Observations are recorded at the cm level, the point at which the species or substrate first crosses the tape being stated. This starting location is noted but the ending point is considered to be the starting point of the next species or substrate. For example, Bouteloua eriopoda encountered at 12m 79cm, litter encountered at 12m 82 cm, bare soil at 12m 85 cm, and so forth.