| The experiment is currently scheduled to run 5 years
(2006-2010). The experiment will utilize Free Air CO2
Enrichment (FACE) technology designed by IBIMET, and infra-red heaters
installed in 3.4 m diameter rings to expose the native NMP and also the NMP
inter-planted to perennial weeds (below) to four combinations of CO2
and temperature, plus two watering treatments. The two water treatments are
designed to 1) simulate the effect of CO2 on plant water use
efficiency with water additions, thereby evaluating how much of the CO2
responses were due simply to improved plant/soil water relations, and 2)
separate the desiccating effect of infra-red warming from the purely temperature
responses. Each of the six treatments will be replicated in five rings, for a
total of 30 rings (map). The
treatments are designated as follows: ACN - ambient CO2, control temp, non-irrigated
AHN - ambient CO2, infra-red heating,
non-irrigated
ECN - elevated CO2 (570 µL L-1 CO2),
control temp, non-irrigated
EHN - elevated CO2, infra-red heating,
non-irrigated
ACI - ambient CO2, control temp, irrigated (to
simulate CO2 water savings)
AHI - ambient CO2, infra-red heating, irrigated
(to evaluate water-temp responses)
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| Each of the rings will be split into two sections by a 25
cm steel flange (ring diagram flange is
oriented with prevailing wind). One side features a northern mixed prairie (NMP)
partitioned into soil and plant sampling areas, plus sections for trace gas
measurements, a minirhizotron tube (Bartz Technology) for studying root
responses, soil water content (Sentek Envirosmart sensors) and air and soil
temperature measurements. The area on the other side of the ring is
partitioned into a one m2 interplanting of Linaria dalmatica (Dalmation
Toadflax) and 8 0.124 m2 areas with winter
annual grasses (Bromus tectorum, Vulpia octiflora), annual mustards (Descurainia
pinnata, D. Sophia) annual lambsquarters (Chenopodium album, C. leptophyllum)
and biennial composites (Centaurea diffusa, Grindelia squarosa. The weed
vs. NMP areas are randomly assigned within each ring, and the weed species are
randomly assigned to weed zones. An approximate 20 cm wide buffer strip
prevents sampling at the outer circle edge where accurate CO2 control
in the elevated CO2 rings is not possible and where plant-mediated
edge effects prevail. |
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