Surface Soil Nutrients

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**The objective of the present research was to determine whether there have been changes in the structure and function of the surface (0-20cm) soil system, the zone most affected by litter decomposition, which is associated with the rapid movement of mesquite from historical habitats (arroyo and playa fringe) into recent habitats (grassland and dunes). We hypothesized that the soil biotic communities would be poorly developed in the recent mesquite habitats because of lower soil C and nutrient concentrations. As a result of these differences we predicted lower rates of net N mineralization in the soils from recent mesquite habitats. Data set contains analyses for gravimetric soil moisture, pH, phosphate, total Kjeldahl nitrogen, total phosphorus, NO3-N nitrogen mineralization, total inorganic nitrogen, NH4-N nitrogen mineralization, organic carbon, inorganic carbon, total roots, tap roots, intermediate roots, and fine roots.

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Field and electronic data sheets

**The soils were sampled in October 1986 at the end of the hot, dry summer season when surface soil biota in the Chihuahuan Desert reach their maximum densities. At each habitat type location (playa, arroyo, grassland and dune) soil samples were collected from the midcanopy beneath six mesquite plants at two depths (0-10 cm and 10-20 cm), using a bucket auger soil corer (7.5 cm diameter, 10 cm depth). The samples were placed in plastic bags, stored in a portable cooler, and then transported to the laboratories. These samples were later divided into subsamples for root mass, soil moisture, and soil chemical analyses. The gravimetric soil water content of the soil samples was determined 2-4 days after soil sample collection, immediately before nematode extraction. Samples used for texture, pH, total organic C, total N, and total P analyses were air dried in a glasshouse, ground to break up clay and caliche aggregates, and passed through a 2-mm mesh sieve. N mineralization and inorganic N analyses were made on field-moist soil. Total C was determined by dry combustion following pretreatment with acid to remove carbonates (Nelson and Sommers 1982). Inorganic C was determined by gravimetric loss of CO2 (U.S. Salinity Laboratory Staff 1954). Particle size distribution was determined by hydrometer method following pretreatment in the disperant sodium hexametaphosphate (Gee and Bauder 1986). Total N and P were determined by Kjeldahl digestion block technique (Bremmer and Mulvaney 1982). Soil NH4+-N and NO3+-N were extracted in a 2 N KCl solution, and analyzed using an automated salicylate procedure (Technicon Industrial Method No. 329-74 W/N). Available P was analyzed as NaHCO3 extractable PO4-P (Olsen and Sommers 1982). The N mineralization potential was estimated using a batch incubation procedure on freshly collected soil as described by Fisher et al. (1987). Two sets of 25-g soil subsamples were incubated at 29C for 4 weeks. The moisture content was adjusted to 0.1 g g-1 (field capacity) at weekly intervals. The soils were extracted with 2 N KCl (Keeney and Nelson 1982) and NH4+-N and NO3--N were determined as above. Net N mineralization was calculated as the net change in N occurring from the beginning to the end of the incubation period.

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*Four mesquite ecosystems were stuided: playa, coppice dune, arroyo, and grassland. The arroyo, grassland, and a playa site were loacated on the NSF Jornada Long Term Ecological Research (LTER) site situated 40 km north of Las Cruces, NM, in the northern Chihuahuan desert. A coppice mesquite dune site was located on the adjacent USDA Jornada Experimental Range about 15 km from the above sites.


One Sample (October)

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