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Application of a conceptual framework to interpret variability in rangeland responses to atmospheric CO2 enrichment

Published online by Cambridge University Press:  05 October 2010

H. W. POLLEY ,
J. A. MORGAN  and
P. A. FAY
H. W. POLLEY*
Affiliation:
U.S. Department of Agriculture, Agricultural Research Service, Grassland, Soil and Water Research Laboratory, Temple, TX 76502, USA
J. A. MORGAN
Affiliation:
U.S. Department of Agriculture, Agricultural Research Service, Crops Research Laboratory, Ft. Collins, CO 80526, USA
P. A. FAY
Affiliation:
U.S. Department of Agriculture, Agricultural Research Service, Grassland, Soil and Water Research Laboratory, Temple, TX 76502, USA
*
*To whom all correspondence should be addressed. E-mail: wayne.polley@ars.usda.gov
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Summary

Plant productivity and other ecosystem processes vary widely in their responses to experimental increases in atmospheric carbon dioxide (CO2) concentration. A conceptual framework first suggested by Chapin et al. (1996) was adapted to address the question of why CO2 effects on primary productivity vary so greatly among rangelands and among years for a given ecosystem. The ‘interactive controls’ framework is based on the premise that the influence of elevated CO2 on productivity is governed by a set of internal variables that interact dynamically with ecosystem processes. These interactive controls, which include regional climate, soil resource supply, major functional groups of organisms and disturbance regimes, both regulate CO2 effects on ecosystems and respond to CO2 effects. Changes in interactive controls resulting from CO2 enrichment may feed back to dampen or amplify ecosystem responses to CO2. Most feedbacks from interactive controls will be negative and dampen CO2 effects on ecosystems. Negative feedbacks promote homeostasis in ecosystem processes and reduce the response of plant productivity to CO2. Positive feedbacks on CO2 responses are fewer, but can sustain or even increase benefits of CO2 enrichment for productivity. Positive feedbacks on CO2 responses occur most frequently through changes in plant species and functional group composition. Understanding positive and negative feedbacks on CO2 responses could be one key to predicting consequences of CO2 enrichment for rangeland productivity and other processes.

Type
Climate Change and Agriculture
Information
The Journal of Agricultural Science , Volume 149 , Issue 1 , February 2011 , pp. 1 - 14
Copyright
Copyright © Cambridge University Press 2010

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