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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 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.Soil mineralization was examined on the control and fertilized treatment transects in association with the vegetation biomass study. In 1989, soil properties were measured. This Dataset contains soil moisture correction factor, sample weight, total inorganic nitrogen (NO3+NO2-N), and nitrogen in ammonium (NH4-N) for Week 0 of nitrogen mineralization potentials. This sampling is complete.
Data sources:
Methods:
Field and electronic data sheets.
This is the detailed procedure used:
A total of 60 samples will be collected from 30 stations. 1 composite sample will be taken on each side of the transect midline, and will consist of 4 1" soil cores taken approximately 2m down from the plant line intercept line and spaced over 15m perpendicular to the transect. This is a total of 30 soil samples at 15 stations on each of the control and treatment transects. Monday, November 27 1. 60 samples are collected on Monday morning and must be processed that afternoon. 2. Mix samples thoroughly by shaking the bag after untying it. 3 Add approximately 10 g to 48 KCl bottles containing 100 ml 2N KCl and labeled with a 5 character code such as C60E. (Week 0.) We will reuse these bottles several more times. 4. Shake each bottle vigorously 30 times and leave on table. 5. Sieve each sample through a 2-mm sieve and then put about 20 g in soil moisture cans for moisture content. RETIE BAGS AND REFRIGERATE UNUSED SOILS. Tuesday, November 28 1 Filter 60 KCl extracts into 60ml bottles labeled C12W-F to T90E-F. Use Whatman #42 filter paper that has been pre- washed with KCl. (F means "Field.") Thursday, November 30 1 Label a total of 180 vials as follows: 60 vials as C12W-2 through T90E-2. (week 2) 60 vials as C12W-4 through T90E-4. (week 4) 60 vials as C12W-8 through T90E-8. (week 8) 2. Remove soil moisture cans from oven, weight and calculate moisture content. 3. Calculate moisture to add to bring moisture content to 8%. ml's = (8 - MC)/4 where MC is moisture content of field soil. 4. Put 25.0 g of soil from each sample into each of 3 vials labeled with the same sample number. For example, weigh soil from sample C12W into vials labeled C12W-2, C12W-4, and C12W-8. 5. Cover vials with 3 layers of Glad Wrap secured with rubber bands. 6. From each sample put approximately 10 g into 100 ml 2N KCl and shake vigorously 30 times. Leave out on table. (Use bottles previously labeled.) 7. Add appropriate amount of water to the vials through the Glad Wrap using a 2.5-ml syringe. Do not shake the vials. Puncture the Glad Wrap with the syringe even if it is not necessary to add water. 8. Weigh vial+sample+Glad Wrap+rubber band and record weight. 9. Incubate the vials at 35oC. AIR DRY THE REMAINING SOIL for 10 days and then store. Friday, December 1 1. Filter KCl extracts using prewashed Whatman #42 filter paper into 60-ml bottles labeled C12W-0 through T90E-0. (Time zero.) Monday, December 4 1. Weigh soil moisture cans and calculate soil moisture content. Thursday, December 7, 14, 21, 28, January 4, 11, 18 1. Weeks 2 and 4 (December 14 and 28): Remove the appropriate vials for extraction first (see below). 2. Weigh each vial and add enough water from a 2.5-ml syringe through the existing hole in the Glad Wrap to return the weight to the original value. Thursday, December 14 1. Remove the week 2 vials (labeled with "-2"). 2. Dump vial on freezer paper and split vertically with scoop. 3. Put about 1/2 (about 10 g) in 125-ml bottles with 2N KCl and shake vigorously 30 times. Use 125-ml bottles already labeled. 4. Put remaining soil in soil moisture can, record weight, and oven dry for 72 hours. 5. Adjust moisture content in remaining vials (see above). Friday, December 15 1. Filter 60 KCl extracts using prewashed Whatman #42 filter papers into 60-ml bottles labeled C12W-2 through T90E-2. Monday, December 18 1. Weigh soil moisture cans and calculate soil moisture content. Thursday, December 28 1. Remove the week 4 vials (labeled with "-4"). 2. Dump vial on freezer paper and split vertically with scoop. 3. Put about 1/2 (about 10 g) in 125-ml bottles with 2N KCl and shake vigorously 30 times. Use 125-ml bottles already labeled. 4. Put remaining soil in soil moisture can, record weight, and oven dry for 72 hours. 5. Adjust moisture content in remaining vials (see above). Friday, December 29 1. Filter 60 KCl extracts using prewashed Whatman #42 filter papers into 60-ml bottles labeled C12W-4 through T90E-4. Tuesday, January 2 1. Weigh soil moisture cans and calculate soil moisture content. Thursday, January 25 1. Remove the remaining vials. 2. Dump vial on freezer paper and split vertically with scoop. 3. Put about 1/2 (about 10 g) in 125-ml bottles with 2N KCl and shake vigorously 30 times. Use 125-ml bottles already labeled. 4. Put remaining soil in soil moisture can, record weight, and oven dry for 72 hours. Friday, January 26 1. Filter 60 KCl extracts using prewashed Whatman #42 filter papers into 60-ml bottles labeled C12W-8 through T90E-8. Monday, January 29 1. Weigh soil moisture cans and calculate soil moisture content.
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. 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. Perpendicular to each transect and crossing at each station marker is the 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 marker by short rebar sticking up about 6 inches aboveground. The plant line intercept transects are thus perpendicular to the direction of major drainage flow. There are 91 stations on each of the 3 2.7 km transects.
Maintenance:
Sampling occured once in 1989. This study is complete.