beyond tree longevity
THE EFFECT OF atmospheric CO2 on tree
growth and terrestrial carbon stocks
has been the subject of much debate. In
his Perspective “A matter of tree longevity” (13 January, p. 130), C. Körner
argued that faster tree growth does not
increase carbon storage because carbon
is inevitably released when trees die. This
is true for individual trees, but focusing
only on the longevity of these dominant
organisms overlooks the foundational
ecological principle that ecosystem
productivity and carbon storage depend
on interactions between fast, locally controlled processes (such as photosynthesis
and respiration) and slow, spatially broad
processes (such as bedrock weathering
and soil formation).
Foremost among the long-lasting
effects of trees is their influence on
the quantity and stability of microbi-
ally produced organic matter (1, 2).
Microbial growth is carbon-limited,
Notably, the effect of root-mycorrhizal
and the substrate provided to micro-
bial communities by plants can persist
for millennia in the soil (3). Contrary
to what Körner implies, all is not lost
when a tree dies, because a consider-
able amount of its carbon is transferred
to neighboring species through root-
microbial networks (4). These networks
also accelerate chemical weathering of
minerals, which consumes atmospheric
CO2 and increases carbon storage beyond
lithological saturation thresholds.
symbiosis (5) and carboxylate-releasing
root clusters (6) on weathering rates is
several-fold greater than that of climate.
Indeed, root-microbe associations that
evolved millions of years ago resulted
in continental-scale soil formation that
stabilized the climate system by removing
CO2 from the atmosphere and depositing organic materials, now referred to as
fossil fuel (7).
As for the canopy, Körner is correct
that tree growth in controlled CO2 enrich-
ment studies does not scale with carbon
sequestration, as shown in analyses of
natural forests (8). There are, however,
irrevocable parallels between plant
growth and soil development in which
fast physiological responses intersect
slow processes of soil formation. For
example, plant-soil connections dictate
patterns of biodiversity and soil carbon
storage (9) and changes in tree perfor-
mance often precede forest range shifts
(10). These examples illustrate how seem-
ingly weak ties between soil, plants, and
the atmosphere can be used to predict
strong shifts in terrestrial carbon stocks.
Lucas C. R. Silva
Environmental Studies Program, Department of
Geography, Institute of Ecology and Evolution,
University of Oregon, OR 97405, USA.
1. B. Bachelot etal.,Ecol.Appl. 6, 1881 (2016).
2. T. Winsome et al., Forest Ecol. Manag. 384,415(2017).
3. S. Trumbore, Annu. Rev. Earth Planet. Sci.37,47(2009).
4. Y. Y. Song, S. W. Simard, A. Carroll, W. W. Mohn, R. Sen Zeng,
Sci. Rep. 5, 8495 (2015).
5. L.L.Taylor, S.A.Banwart, P.J.Valdes,J.R.Leake,D.J.
Beerling, Philos. Trans. R. Soc. London Ser. B Biol. Sci. 367,
6. H. Lambers, E. Martinoia, M. Renton, Curr. Opin. Plant Biol .
25, 23 (2015).
7. J. A. Raven, D. Edwards, J. Exp. Bot .52, 381 (2001).
8. L. C. R. Silva, M. Anand, Glob. Ecol. Biogeogr.22, 83 (2013).
9. D. Sheil, B. Ladd, L. C. R. Silva, S. W. Laffan, M. Van Heist,
Environ. Conserv. 43, 231 (2016).
10. L. C. R. Silva etal ., Sci.Adv .2, e1501302 (2016).
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