East and west boundary fence plant line intercepts - percent cover for 9 species, Jornada Basin, 1982 to 1992

Study number: 

120

Data set ID: 

210120002

Data Access: 

Unrestricted

Dataset status: 

Date range: 

1982-10-08 to 1992-09-11

Original investigator: 

Walter G Whitford

Data contact: 

Abstract: 

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. This summary data set consists of percent cover of 9 species from the plant line intercept measurements on either side of the LTER-I exclosure East and West boundary fence. Data is sorted by station, species i.d., then line segment. Along the East Boundary fence, the east side is ungrazed (control) and the west side is grazed (treatment). Along the West Boundary fence, the east side is grazed and the west side is ungrazed. Each plant line transect is divided into 6 5-meter segments. All perennials were measured at about 5 year intervals as the length of intercept along a 30-meter line perpendicular to the fence. Summary data includes only four of the 6 5-meter intervals due to disturbance along fenceline. Data from the 5-meter segment on either side of the fence was not included in summarizing the data. Summary data includes only 9 of the perennial species.

Data download: 

Methods: 

1982 and 1986 data recorded using field data sheets.

1992 and 1998 data recorded on audio tape and transcribed to floppy disk.

1. Permanently marked 30m line transects were located at about 50m intervals along the two parallel long axis fences of the LTER exclosure which begins immediately above the College Playa and extends toward Mt. Summerford. These fences run from north to south up the slope of the watershed, traversing the component landforms characteristic of the bajadas of the Basin and Range Province. The line transects are perpendicular to the fences and cross them at a fence post (either T-post or wood post) on the downslope side. They are thus perpendicular to the direction of major drainage flow. The line transects are identified by an aluminum tag wired to the fence post. The letter on the tag i.d. identifies the fence (East or West); the number is the station number (East: 1-30; West: 1-31).

Canopy cover of only perennial species intercepted by a line stretched the length of the 30-meter line transect are measured and recorded for each of 6 5-meter segments. The ends of the line are anchored by 3/8" rebar extending about 6 inches out of the ground. When measurements are to be made, a length of clothesline is stretched between the two rebar so it is taut. Before making readings, ensure the line is freed from obstructions so it is perfectly straight between the two rebar. This may require threading the line through large plants or lifting free where sections are snagged.

The clothesline used is pre-stretched overnight when new to minimize changes in length when stretched tight in the field. It is marked in 5 meter increments with enamel paint to indicate segment lengths. The length of the line should be checked before beginning a new season of measurements to ensure that stretching has not distorted line.

Data is recorded by identifying Station number (metal tag is located on fence post) and Segment number. The 5-meter segments are numbered 1 through 6 beginning at the west end of the line (right end if facing upslope). Length of each plant species that is intercepted by line is recorded. Multiple readings (intercept observation) can occur for a single plant if vegetation is broken up with open areas along the line intercept. Each new 5-meter line segment is identified as it is encountered. Plant species are recorded as a 4 letter acronym consisting of first 2 letters of genus and first 2 letters of species epithet. If a duplicate acronym results for 2 different species, generally the 3rd letter of the species epithet is then used. Acronyms used are found in the Plant Checklist for the NSF/LTER Jornada Sites.

Data sheets were used to record the data until Week 559. At this time tape recorders were used to record the field data. This data was entered and processed using several programs. INPUT.EXE (Fortran) is used to input tape recorded data. CONVERT.EXE (Fortran) is used to convert the entered tape recorded data to a format that matches that entered from data sheets. SRELCHEK.EXE (QuickBasic) error checks data. LTERCOVR.EXE (Fortran) summarizes and calculates mean percent cover for each species on each 30-meter line transect at each station.

Quality assurance: 

Beginning in 1992 field data is recorded on audio tape then transcribed using Fortran program INPUT.FOR.

Additional information: 

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. The northeast side of the exclosure is immediately upslope of the College Playa located near the NMSU College Ranch.

Permanently marked 30m line transects were located at 50m intervals along the two parallel long axis fences of the exclosure. These fences run from north to south (more or less) up the slope of the watershed, traversing the component landforms characteristic of the bajadas of the Basin and Range Province. The transects are thus perpendicular to the direction of major drainage flow.

There are 31 30-meter line intercepts located along the west boundary fence and 30 30-meter line intercepts located along the east boundary fence.

Line intercepts are located at every 5th fence pole (except where noted) starting near the ranch headquarters access road which passes by the playa. Fence poles are not marked and transects E01 and W01 are located several fence poles south of the road. [W04 is 6 posts from W03; W19 is 4 posts from W18.]

Each line intercept is 30 meters in length and divided into 6 5-meter segments; 3 segments of each line (15 meters) are inside the fence and ungrazed, the other 3 segments are outside the fence and is subject to grazing when pastures are stocked. Segments are numbered 1 - 6 beginning from the west end of the line (or if facing upslope while standing at the fence, segment 1 begins at the end of the intercept line to your right).

Maintenance: 

5 year intervals

Long-term dataset: 

Signature dataset: 

LTER Core Area(s): 

Data category: 

LTER VI Proposal Category: 

DOI: 

10.6073/pasta/8a89a

Research Network: