Plant communities across large portions of the southwestern United States have shifted from grassland to desert shrubland. Studies have demonstrated that soil nutrient resources become spatially more heterogeneous and are redistributed into islands of fertility with this shift in vegetation. This research addressed the additional question of whether soil resources become more temporally heterogeneous along a grassland-shrubland ecotome. Within adjacent grassland and creosotebush sites, soil profiles were described at 3 pits and samples collected for description of nutrient resources within the profile. Relative cover of plant species and bare soil were determined within each site by line transects. The top 20-cm of bare soil or soil beneath the canopy of grasses/creosotebush were collected 17 times during 1992-1994. Soil samples were analyzed for soil moisture, extractable ammonium and nitrate, nitrogen mineralization potential, microbial biomass carbon, total organic carbon, microbial respiration, dehydrogenase activity, ratio of microbial C to total C (C[mic]-to-C[org]), and microbial respiration to biomass carbon (metabolic quotient). The major differences in the structure of soils between sites were the apparent loss of a 3 to 5-cm depth of sandy surface soil at the creosotebush site and an associated increase in calcium carbonate content at a more shallow depth. Soils under plants at both sites had greater total and available nutrient resources with higher concentrations under creosotebush than under grasses. Greatest temporal variation in available soil resources was shown in soils under creosotebush. When expressed on an area basis, greater temporal variation in the total amount of available soil resources was shown in the grassland site, primarily due to greater plant cover (45% in grassland vs. 8% in creosote).
Knowledge Network for Biocomplexity (KNB) Identifier
Data Policies: This dataset is released to the public and may be freely downloaded. Please keep the designated Contact person informed of any plans to use the dataset. Consultation or collaboration with the original investigators is strongly encouraged. Publications and data products that make use of the dataset must include proper acknowledgement of the Sevilleta LTER. Datasets must be cited as in the example provided. A copy of any publications using these data must be supplied to the Sevilleta LTER Information Manager. By downloading any data you implicitly acknowledge the LTER Data Policy (http://www.lternet.edu/data/netpolicy.html).
Sevilleta Long Term Ecological Research (LTER) Project
1992-04-01 - 1994-08-30
Five Points is the area which encompasses the Five Points Black Grama and Five Points Creosote Core study sites and falls along the transition between Chihuahuan Desert Scrub and Desert Grassland habitats. Both sites are subject to intensive research activity, including NPP measurement, phenology observation, pollinator diversity studies, and ground dwelling arthropod and rodent population assessments. There are drought rain-out shelters in both the Black Grama and Creosote sites, as well as the mixed-ecotone, with co-located ET Towers.Five Points Black Grama is on the transition between Chihuahuan Desert Scrub and Desert Grassland habitat. The site is subject to intensive research activity, including assessments of net primary productivity, phenology, and pollinator diversity, amongst other projects. It is the site of the unburned black grama (GU) component of the Burn NPP study. On August 4, 2009, a lightning-initiated fire began on the Sevilleta National Wildlife Refuge. By August 5, 2009, the fire had reached the Five Points Black Grama site. Portions of this site were burned, but not the entirety. See individual projects for further information on the effects of the burn. The Five Points area emcompasses both the Five Points Black Grama and Five Points Creosote study sites. Five Points falls along the transition between the Chihuahuan Desert Scrub and Desert Grassland habitats. Both core sites are subject to intensive research activities, including NPP measurements, phenology observations, pollinator diversity studies, and ground dwelling arthropod and rodent population assessments. There are rain-out shelters for drought studies in both the Five Points Black Grama and Five Points Creosote sites.
White, Carleton; Kieft, Thomas L (2010-09-15): Temporal Dynamics of Soil Carbon and Nitrogen Resources Within a Grassland-Creosote Ecotone at the Sevilleta National Wildlife Refuge, New Mexico (1992-1994). Long Term Ecological Research Network. http://dx.doi.org/10.6073/pasta/0075c238f8795a68b1e412b8f996471d