24. Ecosystem Climate Manipulations
sponse to climate change may be related to longterm response to differing climate conditions. Thus,
field manipulation experiments should not be performed in isolation, but in tandem with a variety of
laboratory and other field techniques and development of mechanistic and statistical models.
Simulation models of soil and ecosystem processes can be used to integrate experimental findings into existing large-scale ecosystem models,
and ecosystem climate manipulation experiments
offer a sensitivity analysis and testing of current
models of ecosystem function in various biomes
(NSFESP 1991). Ecosystem climate manipulations
provide an unparalleled opportunity to calibrate and
validate mechanistic models, a great virtue since
lack of suitable observations is inhibiting the evaluation of universal land surface schemes (Gates et
al. 1995). For example, in the meadow warming
experiment of Harte et al. (1995b), Shen (1998)
calibrated a microclimate model with soil temperature and moisture data from control plots, then
validated the model against the treatment minus
control difference. This constitutes a rigorous validation against an independent data set, something
rarely possible but much desired in modeling
studies.
Ecosystem field studies combining more than
one manipulation (warming, CO2, UV, moisture, or
other stresses) are becoming more common (e.g.,
Beerling and Woodward 1994; Chapin et al. 1995;
Nijs et al. 1996; Repo et al. 1996; Tissue and
OescheI1987). Cost may be an issue, as long-term
field studies of enhanced CO 2 concentration or
UV-B radiation are difficult and expensive, and
some manipulations are problematic to design and
implement. The complication of confounding factors (i.e., difficulty attributing an observed response
to a particular forcing variable) can be reduced with
an appropriate factorial design, provided a sufficiently large area of habitat is available for experimentation. Both single-variable and combinedvariable manipulations have merits and pitfalls, and
each yields information not extractable from the
other.
Most ecosystem climate manipulations have focused on alpine, subalpine, Arctic, and sub-Arctic
ecosystems, because global climate change is predicted to be especially pronounced in these types
of systems, and also because these systems are considered to be especially sensitive to changes. There
365
is much to be learned from ecosystem manipulations in other regions, such as midlatitudes and
tropics. Future work might beneficially target these
gaps.
References
Adamse, P.; Britz, SJ. Rapid fluence-dependent responses to ultraviolet-B radiation in cucumber leaves:
The role of UV-absorbing pigments in damage protection. l Plant Physiol. 148:57--62; 1996.
Anderson, lE.; Williams, J.; Kriedemann, P.E.; Austin,
M.P.; Farquhar, G.D. Correlations between carbon isotope discrimination and climate of native habitats for
diverse eucalypt taxa growing in a common garden.
Aust. J. Plant Physiol. 23:311-320; 1996.
Anderson, lM. Responses of soils to climate change. In:
Woodward, EI., ed. Global Climate Change: The Ecological Consequences. Advances in Ecological Research. Vol. 22. New York: Academic Press,
1992:163-210.
Barnes, P.w.; Flint, S.D.; Caldwell, M.M. Early-season
effects of supplemented solar UV-B radiation on seedling emergence, canopy structure, simulated stand
photosynthesis and competition for light. Global
Change BioI. 1:43-53; 1995.
Beerling, DJ.; Woodward, F.I. The climate change experiment (CLIMEX): Phenology and gas exchange responses of boreal vegetation to global change. Global
Ecol. Biogeogr. Lett. 4:17-26; 1994.
Bjorn, L.O.; Murphy, T.M. Computer calculation of solar
ultraviolet radiation at ground level. Physiol. Vegetat.
23:555-561; 1985.
Bridgham, S.D.; Pastor, J.; Updegraff, K.; Janssens, J.A.;
Malterer, T.J. [Abstract] Paper presented at the Ecological Society of America Annual Meeting, Snowbird, Utah, July 30 to August 3, 1995.
Brooks, P.D.; Williams, M.W.; Schmidt, S.K. Microbial
activity under alpine snowpacks, Niwot Ridge, Colorado. Biogeochemistry 32:93-113; 1996.
Burke, I.C.; Elliott, E.T.; Cole, C.V. Influence of macroclimate, landscape position, and management on
soil organic matter in agroecosystems. Ecol. Applic.
5:124-131; 1995.
Caldwell, M.M.; Camp, L.B.; Warner, C.w.; Flint, S.D.
Action spectra and their key role in assessing biological consequences of solar UV-B radiation change. In:
Worrest, R.C.; Caldwell, M.M., eds. Stratospheric
Ozone Reduction, Solar Ultraviolet Radiation, and
Plant Life. Berlin: Springer-Verlag; 1986.
Caldwell, M.M.; Flint, S.D. Stratospheric ozone reduction, solar UV-B radiation and terrestrial ecosystems.
Climat. Change 28:375-394; 1994.
sponse to climate change may be related to longterm response to differing climate conditions. Thus,
field manipulation experiments should not be performed in isolation, but in tandem with a variety of
laboratory and other field techniques and development of mechanistic and statistical models.
Simulation models of soil and ecosystem processes can be used to integrate experimental findings into existing large-scale ecosystem models,
and ecosystem climate manipulation experiments
offer a sensitivity analysis and testing of current
models of ecosystem function in various biomes
(NSFESP 1991). Ecosystem climate manipulations
provide an unparalleled opportunity to calibrate and
validate mechanistic models, a great virtue since
lack of suitable observations is inhibiting the evaluation of universal land surface schemes (Gates et
al. 1995). For example, in the meadow warming
experiment of Harte et al. (1995b), Shen (1998)
calibrated a microclimate model with soil temperature and moisture data from control plots, then
validated the model against the treatment minus
control difference. This constitutes a rigorous validation against an independent data set, something
rarely possible but much desired in modeling
studies.
Ecosystem field studies combining more than
one manipulation (warming, CO2, UV, moisture, or
other stresses) are becoming more common (e.g.,
Beerling and Woodward 1994; Chapin et al. 1995;
Nijs et al. 1996; Repo et al. 1996; Tissue and
OescheI1987). Cost may be an issue, as long-term
field studies of enhanced CO 2 concentration or
UV-B radiation are difficult and expensive, and
some manipulations are problematic to design and
implement. The complication of confounding factors (i.e., difficulty attributing an observed response
to a particular forcing variable) can be reduced with
an appropriate factorial design, provided a sufficiently large area of habitat is available for experimentation. Both single-variable and combinedvariable manipulations have merits and pitfalls, and
each yields information not extractable from the
other.
Most ecosystem climate manipulations have focused on alpine, subalpine, Arctic, and sub-Arctic
ecosystems, because global climate change is predicted to be especially pronounced in these types
of systems, and also because these systems are considered to be especially sensitive to changes. There
365
is much to be learned from ecosystem manipulations in other regions, such as midlatitudes and
tropics. Future work might beneficially target these
gaps.
References
Adamse, P.; Britz, SJ. Rapid fluence-dependent responses to ultraviolet-B radiation in cucumber leaves:
The role of UV-absorbing pigments in damage protection. l Plant Physiol. 148:57--62; 1996.
Anderson, lE.; Williams, J.; Kriedemann, P.E.; Austin,
M.P.; Farquhar, G.D. Correlations between carbon isotope discrimination and climate of native habitats for
diverse eucalypt taxa growing in a common garden.
Aust. J. Plant Physiol. 23:311-320; 1996.
Anderson, lM. Responses of soils to climate change. In:
Woodward, EI., ed. Global Climate Change: The Ecological Consequences. Advances in Ecological Research. Vol. 22. New York: Academic Press,
1992:163-210.
Barnes, P.w.; Flint, S.D.; Caldwell, M.M. Early-season
effects of supplemented solar UV-B radiation on seedling emergence, canopy structure, simulated stand
photosynthesis and competition for light. Global
Change BioI. 1:43-53; 1995.
Beerling, DJ.; Woodward, F.I. The climate change experiment (CLIMEX): Phenology and gas exchange responses of boreal vegetation to global change. Global
Ecol. Biogeogr. Lett. 4:17-26; 1994.
Bjorn, L.O.; Murphy, T.M. Computer calculation of solar
ultraviolet radiation at ground level. Physiol. Vegetat.
23:555-561; 1985.
Bridgham, S.D.; Pastor, J.; Updegraff, K.; Janssens, J.A.;
Malterer, T.J. [Abstract] Paper presented at the Ecological Society of America Annual Meeting, Snowbird, Utah, July 30 to August 3, 1995.
Brooks, P.D.; Williams, M.W.; Schmidt, S.K. Microbial
activity under alpine snowpacks, Niwot Ridge, Colorado. Biogeochemistry 32:93-113; 1996.
Burke, I.C.; Elliott, E.T.; Cole, C.V. Influence of macroclimate, landscape position, and management on
soil organic matter in agroecosystems. Ecol. Applic.
5:124-131; 1995.
Caldwell, M.M.; Camp, L.B.; Warner, C.w.; Flint, S.D.
Action spectra and their key role in assessing biological consequences of solar UV-B radiation change. In:
Worrest, R.C.; Caldwell, M.M., eds. Stratospheric
Ozone Reduction, Solar Ultraviolet Radiation, and
Plant Life. Berlin: Springer-Verlag; 1986.
Caldwell, M.M.; Flint, S.D. Stratospheric ozone reduction, solar UV-B radiation and terrestrial ecosystems.
Climat. Change 28:375-394; 1994.