Title: Microclimatic performance of a free-air warming and CO₂ enrichment experiment in windy Wyoming, USA

Abstract

In order to plan for global changing climate experiments are being conducted in many countries, but few have monitored the effects of the climate change treatments (warming, elevated CO2) on the experimental plot microclimate. During three years of an eight year study with year-round feedback-controlled infra-red heater warming (1.5/3.0°C day/night) and growing season free-air CO2 enrichment (600 ppm) in the mixed-grass prairie of Wyoming, USA, we monitored soil, leaf, canopy-air, above-canopy-air temperatures and relative humidity of control and treated experimental plots and evaluated ecologically important temperature differentials. Leaves were warmed somewhat less than the target settings (1.1 & 1.5°C day/night) but soil was warmed more creating an average that matched the target settings extremely well both during the day and night plus the summer and winter. The site typically has about 50% bare or litter covered soil, therefore soil heat transfer is more critical than in dense canopy ecosystems. The Wyoming site commonly has strong winds (5 ms-1 average) and significant daily and seasonal temperature fluctuations (as much as 30°C daily) but the warming system was nearly always able to maintain the set temperatures regardless of abiotic variation. The within canopy-air was only slightly warmed and above canopy-air was notmore » warmed by the system, therefore convective warming was minor. Elevated CO2 had no direct effect nor interaction with the warming treatment on microclimate. Relative humidity within the plant canopy was only slightly reduced by warming. Soil water content was reduced by warming but increased by elevated CO2. This study demonstrates the importance of monitoring the microclimate in manipulative field global change experiments so that critical physiological and ecological conclusions can be determined. Highly variable energy demand fluctuations showed that passive IR heater warming systems will not maintain desired warming for much of the time.« less

Authors:

LeCain, Daniel ^[1]; Smith, David ^[1]; Morgan, Jack ^[1]; Kimball, Bruce A. ^[2]; Pendall, Elise ^[3]; Miglietta, Franco ^[4]; Liang, Wenju ^[5]

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+ Show Author Affiliations

1. United States Department of Agriculture, Fort Collins, CO (United States)
2. United States Arid-Land Agricultural Research Center, Maricopa, AZ (United States)
3. Univ. of Western Sydney, Sydney (Australia)
4. Instituto di Biometeorologia, Firenze (Italy)
5. Chinese Academy of Sciences (CAS), Beijing (China)

Publication Date:

Fri Feb 06 00:00:00 EST 2015

Research Org.:

United States Department of Agriculture, Fort Collins, CO (United States); Univ. of Wyoming, Laramie, WY (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Biological and Environmental Research (BER)

OSTI Identifier:

1193634

Alternate Identifier(s):

OSTI ID: 1454916

Grant/Contract Number:  

SC0006973

Resource Type:

Accepted Manuscript

Journal Name:

PLoS ONE

Additional Journal Information:

Journal Volume: 10; Journal Issue: 2; Journal ID: ISSN 1932-6203

Publisher:

Public Library of Science

Country of Publication:

United States

Language:

English

Subject:

54 ENVIRONMENTAL SCIENCES