Surface Soil Canopy Position Nutrients

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Soils were sampled under Prosopis at four sites and under Larrea at one site on the Jornada Desert Site on October 1, 1986. Samples were taken from two depths (0-15cm, 15-30cm) for three canopy positions and one interzone position for each tree or shrub. Four trees or shrubs were sampled at each site. The soils were analyzed for Total Kjeldahl Nitrogen (TKN), and inorganic N-- nitrate-N and ammonium-N.

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Field and electronic data sheets

Soil samples were taken (augered) from three canopy positions, base, mid-canopy, and outer edge-of-canopy, beneath each tree or shrub (four per site). Also sampled was an interzone position in an unvegetated area one canopy radius (distance) away from the edge of the tree canopy. The interzone distance was less when tree spacing was closer. Two soil depths, 0-15cm and 15-30cm, were sampled at each position. Sampling took place on October 1, 1986. Soil samples were air-dryed in a glasshouse and ground to pass a 2-mm sieve. Total N was digested by Kjeldahl digestion block techniques (Bremner and Mulvaney, 1982). Digest NH4-N was analysed using an automated salicylate procedure (Technicon Industrial Method No. 329-74W/B). Inorganic N (NH4-N and NO3 + NO2-N) was extracted with 2M KCl (Keeney and Nelson, 1982). Ammonium-N in the extracts was analyzed colorimetrically (indophenol blue) in an automated procedure (Technicon Industrial Method No. 154-71) and NO3 + NO2-N was measured by an automated Cd reduction colorimetric procedure (Technicon Industrial Method No. 100-70W/).

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*Four mesquite ecosystems were studied: playa, coppice dune, arroyo, and grassland. An ecosystem dominated by the non-legume, Larrea tridentata, and lacking mesquite was included as a reference. The arroyo, grassland, Larrea 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.


Three times (January, May, and September)

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