Jornada Basin LTER Research

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Dataset: Biomass at Fertilized and Unfertilized Transects in a Grazing Exclosure in the Jornada Basin,1989


   File description including attribute definitions: data_JornadaStudy_015_transect_vegetation_biomass_data
   Original Investigator: Walter G Whitford
   Duration: 1989 - 1989
   Dataset ID: 210015001
   DOI: 10.6073/pasta/6d8042aebd60fca10646e912eeb498e4
   Abstract:

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.


   Additional information:

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.

   Methods:

The Treatment transect was treated annually until 1987 with NHNO3 in a concentration equal to 10g N/m2. The control transect was not treated.  The station markers occur at 30 meter intervals along each transect.There are 91 stations on each of the 3 2.7 km transects. Perpendicular to each transect and crossing at each station marker is a 30 meter plant line intercept transect. This extends 15 meters on either side of the station marker. The ends of the plant line intercept transect are marked by short rebar sticking up about 6 inches aboveground. The plant line intercept transects are thus perpendicular to the direction of major drainage flow. Biomass of annual and perennial forbs and grasses was obtained from a one meter quad selected at random just downslope from each of the 6 5-meter segments of the 30 meter plant line transects.

Data is recorded by identifying Station number (metal tag is located on fence post) and Segment number corresponding to those of the 30 meter plant line intercept running perpendicular to the main transect and station marker. The 5-meter segments are numbered 1 through 6 beginning at the west end of the line (right end if facing upslope). Biomass quads were located just downslope of the line intercept segments. One 1-meter section of the 5-meter segment was selected randomly for the 1-meter quadrat. Both annual and perennial forbs and grasses were measured using biomass removals.

   Maintenance:

Data was collected one time. This study is complete.