Links across ecological scales: Plant biomass responses to elevated CO2
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Date
2022
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Abstract
The degree to which elevated CO2 concentrations (e[CO2]) increase the amount of
carbon (C) assimilated by vegetation plays a key role in climate change. However, due
to the short-term
nature of CO2 enrichment experiments and the lack of reconciliation
between different ecological scales, the effect of e[CO2] on plant biomass stocks
remains a major uncertainty in future climate projections. Here, we review the effect
of e[CO2] on plant biomass across multiple levels of ecological organization, scaling
from physiological responses to changes in population-,
community-,
ecosystem-,
and global-scale
dynamics. We find that evidence for a sustained biomass response
to e[CO2] varies across ecological scales, leading to diverging conclusions about the
responses of individuals, populations, communities, and ecosystems. While the distinct
focus of every scale reveals new mechanisms driving biomass accumulation under
e[CO2], none of them provides a full picture of all relevant processes. For example, while physiological evidence suggests a possible long-term
basis for increased biomass
accumulation under e[CO2] through sustained photosynthetic stimulation, population-scale
evidence indicates that a possible e[CO2]-induced
increase in mortality rates
might potentially outweigh the effect of increases in plant growth rates on biomass
levels. Evidence at the global scale may indicate that e[CO2] has contributed to
increased biomass cover over recent decades, but due to the difficulty to disentangle
the effect of e[CO2] from a variety of climatic and land-use-
related
drivers of plant
biomass stocks, it remains unclear whether nutrient limitations or other ecological
mechanisms operating at finer scales will dampen the e[CO2] effect over time. By
exploring these discrepancies, we identify key research gaps in our understanding of
the effect of e[CO2] on plant biomass and highlight the need to integrate knowledge
across scales of ecological organization so that large-scale
modeling can represent the
finer-scale
mechanisms needed to constrain our understanding of future terrestrial C
storage.
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Keywords
carbon dioxide, carbon turnover, CO2 fertilization, free-air CO2 enrichment (FACE), global carbon cycle, plant demography, terrestrial carbon storage
Citation
Maschler, J., Bialic-Murphy, L., Wan, J., Andresen, L. C., Zohner, C. M., Reich, P. B., Lüscher, A., Schneider, M. K., Müller, C., Moser, G., Dukes, J. S., Schmidt, I. K., Bilton, M. C., Zhu, K., & Crowther, T. W. (2022). Links across ecological scales: plant biomass responses to elevated CO2. Global Change Biology, 28(21), 6115–6134. https://doi.org/10.1111/gcb.16351