Data from: Soil organic carbon stability in forests: distinct effects of tree species identity and traits

Rising atmospheric CO2 concentrations have increased interest in the
potential for forest ecosystems and soils to act as carbon (C) sinks.
While soil organic C contents often vary with tree species identity,
little is known about if, and how, tree species influence the stability of
C in soil. Using a 40‐year‐old common garden experiment with replicated
plots of eleven temperate tree species, we investigated relationships
between soil organic matter (SOM) stability in mineral soils and 17
ecological factors (including tree tissue chemistry, magnitude of organic
matter inputs and their turnover, microbial community descriptors, and
soil physico‐chemical properties). We measured five SOM stability indices,
including heterotrophic respiration, C in aggregate‐occluded particulate
organic matter (POM) and mineral‐associated SOM, and bulk SOM δ15N and
∆14C. The stability of SOM varied substantially among tree species and
this variability was independent of the amount of organic C in soils.
Thus, when considering forest soils as C sinks, the stability of C stocks
must be considered in addition to their size. Further, our results suggest
tree species regulate soil C stability via the composition of their
tissues, especially roots. Stability of SOM appeared to be greater (as
indicated by higher δ15N and reduced respiration) beneath species with
higher concentrations of nitrogen and lower amounts of acid‐insoluble
compounds in their roots, while SOM stability appeared to be lower (as
indicated by higher respiration and lower proportions of C in
aggregate‐occluded POM) beneath species with higher tissue calcium
contents. The proportion of C in mineral‐associated SOM and bulk soil
∆14C, though, were negligibly dependent on tree species traits, likely
reflecting an insensitivity of some SOM pools to decadal‐scale shifts in
ecological factors. Strategies aiming to increase soil C stocks may thus
focus on particulate C pools, which can more easily be manipulated and are
most sensitive to climate change.