|Data by Research Category|
Dataset: Rabbit Pellet Total Nitrogen
Rabbit pellets were collected from 24 5x5m plots at approximately 1 month intervals. Dry weight by date and plot was recorded. Pellets were subsampled and analyzed for Total N. Plots are located along LTER-1 Control and Treatment transects in creosotebush (around station C62 and T61) and upper basin slope. (See site description.) Plots are located along LTER-1 Control and Treatment transects in creosotebush (around station C62 and T61) and upper basin slope. (See site description.)
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. 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 on the east side of the Control transect, and the Alternate Control 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 at 30 meter intervals along each transect. LTER-I Control and Treatment transect, around C62 and T61 (creosotebush zone), and around C48 and T46 (upper basin slope). 3 paired 5x5 meter plots were established approximately halfway between transect sttations and approximately 5m from transect walkway on both the treatment and control transects in upper basin and creosotebush zones. Each pair of plots consists of a control and treatment. The control is closest to the transect walkway. The control is marked with wood stakes at plot corners. The treatment abuts the control and is fenced with aluminum window screening approximately 3" high. An additional inch on the bottom is folded inward and pegged to ground with "60 common" nails every 20cm to prevent rabbit pellets from rolling out of plots. 12" 1x2 wood stakes are placed every meter with the aluminum mesh stapled to them. 8" long 3/8" diameter rebar are placed between stakes to maintain an inward angle on screen to prevent rabbit pellets from rolling over the top during high winds.
Data book (titled "Herbage Wastage")Methods:
1. Initial collection consists of picking up both new and old rabbit cuttings from control and treatment plots and then sweeping plots to collect rabbit pellets. Clippings were placed in paper bags and rabbit pellet sweepings in large plastic gargage bags labeled with plot number and returned to Biology Annex for later processing. 2. Plots will be sampled monthly. Clippings and pellets will be picked up by hand. (The initial idea of vacuuming with CarVac didn't work.) 3. Clippings will be sorted by species, oven-dried at 50C, weighed, and subsampled for Total N analysis. 4. Rabbit pellets will be oven-dried, weighed, and subsampled for Total N analysis. 5. Subsample is ground in Wiley mill sufficient to pass through a #40 mesh. Nitrogen analysis is by Kjeldahl digestion. Each subsample is digested twice.