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Depth Distribution and Seasonal Populations of Mesquite‐Nodulating Rhizobia in Warm Desert Ecosystems
Author(s) -
Jenkins Michael B.,
Virginia Ross A.,
Jarrell Wesley M.
Publication year - 1988
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1988.03615995005200060026x
Subject(s) - larrea , ecosystem , rhizobia , soil water , environmental science , population , biomass (ecology) , ecology , agronomy , biology , nitrogen fixation , soil science , shrub , demography , sociology , bacteria , genetics
Deeply rooted woody legumes are common in desert ecosystems yet little is known about the distribution of their rhizobial symbionts in relation to their roots and soil properties of the systems. The distribution of mesquite ( Prosopis glandulosa Torr.)‐nodulating rhizobia was investigated to depths of 13 m in warm desert ecosystems. Soils were collected under mesquite from sand dune and playa ecosystems in the California Sonoran Desert, and from sand dune, playa, arroyo, and grassland ecosystems in the Chihuahuan Desert of southern New Mexico. A Larrea tridentata (DC.) Coville (creosote bush) ecosystem in New Mexico, containing no mesquite, was sampled as a reference. Three intact soil cores from each ecosystem were removed during the winter, spring, and fall from the New Mexico sites, and the winter from the California sites. Significant rhizobial population densities were measured in soil from 1‐ to 4‐m depths at the sand dune, arroyo, and playa ecosystems. At the playa ecosystem in New Mexico population densities > 10 5 cells kg −1 were measured in soils from 8‐m depth, and root nodules containing rhizobia were recovered in soil samples from 3‐, 4‐, and 7‐m depths. Multipleregression analysis of rhizobial concentration against soil NH 4 ‐N, PO 4 ‐P, electrical conductivity, and gravimetric water content indicated that no single soil factor was related significantly to rhizobial concentration across the ecosystems. Rhizobial densities varied with season in the dune and arroyo ecosystems. In these desert ecosystems significant rhizobial populations, root nodules, and presumably symbiotic N 2 fixation occur at soil depths rarely studied.