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Elevated CO2 and O3 Effects on Fine-Root Life Span in Ponderosa Pine

Donald L. Phillips¹, Mark G. Johnson¹, David T. Tingey¹ & Marjorie J. Storm²

Correspondence: (Login to view email address)

1. US Environmental Protection Agency
2. Dynamac International, Inc. c/o US EPA

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Document Type:

Poster

Date:

Received 31 August 2009 20:22 UTC; Posted 01 September 2009

Subjects:

Ecology, Earth & Environment, Plant Biology

Tags:

• fine roots
• life span
• turnover
• carbon dioxide
• Ozone
• ponderosa pine
• survival analysis
• proportional hazards

Abstract:

Atmospheric carbon dioxide (CO2) and ozone (O3) concentrations are rising, which may have opposing effects on tree C balance and allocation to fine roots. More information is needed on interactive CO2 and O3 effects on roots, particularly fine-root life span, a critical demographic parameter and determinant of soil C and N pools and cycling rates. We conducted a study in which ponderosa pine (Pinus ponderosa) seedlings were exposed to two levels of CO2 and O3 in sun-lit controlled-environment terracosms for three years. Minirhizotrons were used to monitor individual fine roots in three soil horizons every 28 days. Proportional hazards regression was used to analyze effects of CO2, O3, diameter, depth, and season of root initiation on fine-root survivorship. More fine roots were produced in the elevated CO2 treatment than in ambient CO2. Median life spans varied from 140-448 days depending on the season of root initiation. Elevated CO2, increasing root diameter, and increasing root depth all significantly increased fine-root survivorship and median life span. Life span was slightly, but not significantly, lower in elevated O3, and increased O3 did not reduce the effect of elevated CO2. These results indicate the potential for elevated CO2 to increase the number of fine roots and their residence time in the soil, which is also affected by root diameter, root depth, and phenology.

Collection:

2009 Annual Meeting of the Ecological Society of America

Presented at:

Ecological Society of America - 2009 Annual Meeting, Albuquerque, NM, 03 August 2009

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License:

This document is licensed to the public under the Creative Commons Attribution 3.0 License

How to cite this document:

Phillips, Donald, Johnson, Mark, Tingey, David, and Storm, Marjorie. Elevated CO2 and O3 Effects on Fine-Root Life Span in Ponderosa Pine. Available from Nature Precedings <http://dx.doi.org/10.1038/npre.2009.3703.1> (2009)

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