Structural equation modelling reveals plant-community drivers of carbon storage in boreal forest ecosystems

Abstract

Boreal forest ecosystems are important drivers of the global carbon (C) cycle by acting as both sinks and sources of atmospheric CO 2 . While several factors have been proposed as determining the ability of boreal forest to function as C sinks, little is known about their relative importance. In this study, we applied structural equation modelling to a previously published dataset involving 30 boreal-forested islands that vary greatly in their historic fire regime, in order to explore the simultaneous influence of several factors believed to be important in influencing above-ground, below-ground and total ecosystem C accumulation. We found that wildfire was a major driver of ecosystem C sequestration, and exerted direct effects on below-ground C storage (presumably through humus combustion) and indirect effects on both above-ground and below-ground C storage through altering plant-community composition. By contrast, plant diversity influenced only below-ground C storage (and even then only weakly), while net primary productivity and decomposition had no detectable effect. Our results suggest that while boreal forests have great potential for storing significant amounts of C, traits of dominant plant species that promote below-ground C accumulation and the absence of wildfire are the most important drivers of C sequestration in these ecosystems.

Key biogeochemical factors affecting soil carbon storage in <i>Posidonia</i> meadows

“…Posidonia tissues contain relatively high amounts of degradation-resistant organic compounds in their tissues (e.g., lignin and cellulose; Harrison, 1989;Klap et al, 2000;Torbatinejad et al, 2007) and high C / N ratios (Duarte, 1990;Pedersen et al, 2011;Kaal et al, 2016). In contrast, seston and algal detritus, which contributed as much as 64-75 % of the C org in the deeper sites, have a higher labile C org content (Laursen et al, 1996) more likely to be remineralized during early diagenesis (Henrichs, 1992), potentially explaining the higher soil C org decay rates in the deep (at 8 m) P. sinuosa meadows. However, the soil C org decay rates in P. sinuosa meadows at 6 m depth were in the range of those found at 2 and 4 m depths.…”

“…In addition, finally, while both autochthonous (e.g., plant detritus and epiphytes) and allochthonous (e.g., seston and terrestrial matter) sources contribute to the C org pool in seagrass soils (Kennedy et al, 2010), the proportion of seagrass-derived C org may be an important factor controlling C org storage capacity. Seagrass tissues contain relatively high amounts of degradationresistant organic compounds (e.g., lignin and cellulose; Harrison, 1989;Klap et al, 2000;Torbatinejad et al, 2007;Burdige, 2007) compared to seston and algal detritus (Laursen et al, 1996), which are more prone to remineralization during early diagenesis (Henrichs, 1992).…”

“…However, there has been a tendency to simplify regional and global estimates of C org stocks in seagrass ecosystems from a very limited data set, based on few species and habitats (Nelleman et al, 2009;Fourqurean et al, 2012). Geomorphological settings (i.e., topography and hydrology), soil characteristics (e.g., mineralogy and texture) and biological features (e.g., primary production and remineralization rates) control soil C org storage in both terrestrial ecosystems (Amundson, 2001;De Deyn et al, 2008;Jonsson and Wardle, 2009) and in mangrove and tidal salt marshes (Donato et al, 2011;Adame et al, 2013;Ouyang and Lee, 2014). However, our understanding of the factors regulating this variability in seagrass meadows is limited (Nellemann et al, 2009;Duarte et al, 2010;Serrano et al, 2014).…”

Accounting Carbon Storage in Decaying Root Systems of Harvested Forests

“…During the growth of forests, both the above-and belowground biomasses act as ''sinks'' where C is sequestered for decades or even centuries (Jonsson and Wardle 2010). In southern pine forests, most of the belowground biomass is in coarse roots Laiho and Finer 1996;Johnsen et al 2001).…”

A Review of Strong Evidence for the Effect of Functional Dominance on Carbon Stocks in Natural Forest Ecosystems

“…In some studies, the species or functional groups have been experimentally removed from initially homogeneous woody communities in the field (Aguiar and Sala, 1994;Diaz et al, 2003;Bret-Harte et al, 2008;Wardle et al, 2008;Urcelay et al, 2009). Further, many studies have been independently tested the effects of different components of FTD, particularly CWM and FD effects, in natural forests and also assessed the trait-specific relationships with C stocks in natural forest ecosystems (Caspersen and Pacala, 2001;Delagrange et al, 2008;Jonsson and Wardle, 2010;Ruiz-Jaen and Potvin, 2011;Wardle et al, 2012). However, empirical studies focusing on the comparison of CWM (the mass ratio hypothesis) and FD (the niche complementarity) effects on C stocks in the naturally established forest ecosystems are still very scarce (Conti and Diaz, 2013;Cavanaugh et al, 2014;Finegan et al, 2015).…”