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DIVISION S-7-FOREST & RANGE SOILS

Phosphorus Pools in Tree and Intercanopy Microsites of a Juniper–Grass Ecosystem

^a Dep. of Plant Biology, Arizona State Univ., Tempe, AZ 85287-1601 USA
^b Environmental Resources Program, School of Planning and Landscape Architecture, Arizona State Univ., Tempe, AZ 85287-2005 USA

dm.green{at}asu.edu

Gradients of soil-nutrient distribution between trees and intercanopy areas are common in many semiarid woodland ecosystems. To test if microsites under and between canopies influenced P pool distribution in a semiarid woodland dominated by one-seed juniper [Juniperus monosperma (Engelm.) Sarg.] and galleta grass [Hilaria jamesii (Torr.) Benth.], we compared inorganic, organic, and microbial P pools under trees and intercanopy areas of two Aridisols. Soils collected (5–15 cm depth) under eight tree canopies and in eight intercanopy areas from a Calciorthid and a Camborthid were subjected to a sequential P fractionation scheme. Soils and microsites were significant independent factors determining total soil P, which ranged from to 1123 µg P g^-1 soil . Resin P was significantly influenced by the interaction of soils with microsite. Organic hydroxide P was the largest organic P fraction and exceeded or equaled the amount of resin P. It differed significantly between the Calciorthid at 10.1 µg P g^-1 soil and the Camborthid at 22.1 µg P g^-1 soil (SE = 1.6). Microsite and soil did not significantly affect microbial P, which ranged from 12.9 µg P g^-1 soil to 17.0 µg P g^-1 soil . Nutrients and microbial activity are usually concentrated under canopies in semiarid and arid ecosystems. This research shows that P pools distribution in the studied ecosystem did not follow this general pattern, and that soils may be more important in determining P pool distribution than microsites.

Abbreviations: P_i, inorganic P • P_o, organic P

This article has been cited by other articles:

				T. P. McGonigle, M. L. Chambers, and G. J. White Enrichment over Time of Organic Carbon and Available Phosphorus in Semiarid Soil Soil Sci. Soc. Am. J., August 25, 2005; 69(5): 1617 - 1626. [Abstract] [Full Text] [PDF]