Substrate age and tree islands influence carbon and nitrogen dynamics across a retrogressive semiarid chronosequence

Selmants, Paul C. and Hart, Stephen C. (2008) Substrate age and tree islands influence carbon and nitrogen dynamics across a retrogressive semiarid chronosequence. Global Biogeochemical Cycles, 22 (1). GB1021. ISSN 1944-9224

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Abstract

The long-term dynamics of carbon (C) and nitrogen (N) in semiarid ecosystems remain poorly understood. We measured pools and fluxes of surface soil C and N, as well as other soil properties, under tree canopies and in intercanopy spaces at four sites that form a volcanic substrate age gradient in semiarid piñon-juniper woodlands of northern Arizona, United States. Clay content and soil water-holding capacity increased consistently with substrate age, but both soil organic C and N increased only up to the 750,000 year site and then declined at the oldest (3,000,000 year) site. Measures of soil C and N flux displayed a similar pattern to total C and N pools. Pools and fluxes of C and N among the three canopy types became more homogeneous with substrate age up to the 750,000 year site, but disparity between tree and intercanopy microsites widened again at the oldest site. The δ15N of both tree leaves and surface soils became progressively more enriched across the substrate age gradient, consistent with a N cycle increasingly dominated by isotope fractionating losses. Our results point to consistencies in patterns of ecosystem development between semiarid and more humid ecosystems and suggest that pedogenic development may be an important factor controlling the spatial distribution of soil resources in semiarid ecosystems. These data should help both unify and broaden current theory of terrestrial ecosystem development.

Item Type:	Article
Publisher’s Statement:	Copyright 2008 by the American Geophysical Union.
ID number or DOI:	10.1029/2007GB003062
Keywords:	age of soil; Arizona; carbon cycle; chloroform fumigation; clay fraction; Cupressaceae; Developed Countries; ecosystem development; Ecosystems; eukaryotes; geochemical cycle; gymnosperms; isotope fractionation; isotope ratios; isotopes; isotopic composition; Juniperus; leaf canopy; leaves; Microbial biomass; nitrogen; Organic carbon; organic-matter accretion; organic matter in soil; Pinaceae; pines; Pinopsida; Pinus; Pinyon-Juniper woodlands; Plantae; primary succession; semi-arid environment; semiarid zones;soil-microorganisms; Soil organic matter; soil properties; spatial distribution; Spermatophyta; Stable isotopes; substrates; terrestrial environment; water holding capacity;
Subjects:	Q Science > QC Physics Q Science > QH Natural history
NAU Depositing Author Academic Status:	Faculty/Staff
Department/Unit:	Research Centers > Merriam-Powell Center for Environmental Research College of Engineering, Forestry, and Natural Science > School of Forestry
Date Deposited:	16 Oct 2015 23:06
URI:	http://openknowledge.nau.edu/id/eprint/715

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