Constraints and Drivers of Dissolved Fluxes of Pyrogenic Carbon in Soil
and Freshwater Systems: a Global Review and Meta-analysis
Abstract
Pyrogenic carbon (PyC) is a significant component of the global soil
carbon pool due to its longer environmental persistence than other soil
organic matter components. Despite PyC’s persistence in soil, recent
work has indicated that it is susceptible to loss processes such as
mineralization and leaching, with the significance and magnitude of
these largely unknown at the hillslope and watershed scale. We present a
review of the work concerning dissolved PyC transport in soil and
freshwater. Our analysis found the primary environmental controls on
dissolved PyC (dPyC) transport are the formation conditions and quality
of the PyC itself, with longer and higher temperature charring
conditions leading to less transport of dPyC. While correlations between
dPyC and dissolved organic carbon in rivers and other pools are
frequently reported, the slope of these correlations was pool-dependent
(i.e., soil-water, precipitation, lakes, streams, rivers), suggesting
site-specific environmental controls. However, the lack of consistency
in analytical techniques and sample preparation remains a major
challenge to quantifying environmental controls on dPyC fluxes. We
propose that future research should focus on the following: (1)
consistency in methodological approaches, (2) more quantitative measures
of dPyC in pools and fluxes from soils to streams, (3) turnover times of
dPyC in soils and aquatic systems, and (4) improved understanding of how
mechanisms controlling the fate of dPyC in dynamic post-fire landscapes
interact. With more refined quantitative information about the controls
on dPyC transport at the hillslope and landscape scale, we can increase
the accuracy and utility of global carbon models.