A number of nonlinear models have recently been proposed for simulating soil carbon decomposition. Their predictions of soil carbon responses to fresh litter input and warming differ significantly from conventional linear models. Using both stability analysis and numerical simulations, we showed that two of those nonlinear models (a two-pool model and a three-pool model) exhibit damped oscillat...

1 Plant and microbial nitrogen (N) dynamics were examined in soils of an Arctic salt marsh beneath goose-grazed swards and in degraded soils. The degraded soils are the outcome of intensive destructive foraging by geese, which results in vegetation loss and near-irreversible changes in soil properties. The objective of the study was to determine whether vegetation loss led to a decline in micro...

Anthropogenic O3 and CO2-induced declines in soil N availability could counteract greater plant growth in a CO2-enriched atmosphere, thereby reducing net primary productivity (NPP) and the potential of terrestrial ecosystems to sequester anthropogenic CO2. Presently, it is uncertain how increasing atmospheric CO2 and O3 will alter plant N demand and the acquisition of soil N by plants as well a...

Recent studies of SOC storage and turnover have employed 13C natural abundance ( 13C) as an in situ Soil organic carbon (SOC) is sensitive to management of tillage, marker of relic and recent SOC pools. Mass concentraresidue (stover) harvest, and N fertilization in corn (Zea mays L.), tions of SOC and the 13C signature are sufficient to but little is known about associated root biomass includin...

as sorgoleone (Einhellig and Souza, 1992; Einhellig et al., 1993; Weston et al., 1997) and phenolic acids (BenThe total phenol pool (kg ha21) of the aerial parts and roots of Hammouda et al., 1995; De Raissac et al., 1998) to the sorghum (Sorghum bicolor L. cv. CE145266) crops and their relationships to dry matter and total phenol concentrations (g kg21) were soil by decomposing crop residues (...

Soil organic carbon (SOC) pool is the largest among terrestrial pools. The restoration of SOC pool in arable lands represents a potential sink for atmospheric CO2. Restorative management of SOC includes using organic manures, adopting legume-based crop rotations, and converting plow till to a conservation till system. A field study was conducted to analyze soil properties on two farms located i...

The extent to which greater net primary productivity (NPP) will be sustained as the atmospheric CO2 concentration increases will depend, in part, on the long-term supply of N for plant growth. Over a two-year period, we used common field and laboratory methods to quantify microbial N, gross N mineralization, microbial N immobilization, and specific microbial N immobilization in three free-air C...

In PNAS, Sebilo et al. (1) present the fate of labeled nitrate in the soil–plant system over three decades and attempt to determine “to which extent and over which time periods fertilizer N stored in soil organic matter is rereleased for either uptake in crops or export into the hydrosphere.” I suspect that this mechanism of immobilization-mineralization turnover described by Sebilo et al. (1) ...

Published by the College of Tropical Agriculture and Human Resources (CTAHR) and issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture. Andrew G. Hashimoto, Director/Dean, Cooperative Extension Service/CTAHR, University of Hawai‘i at Mänoa, Honolulu, Hawai‘i 96822. An equal opportunity/affirmative action inst...