A Tree Species Effect on Soil That Is Consistent Across the Species’ Range: The Case of Aspen and Soil Carbon in North America

Abstract

Trembling aspen covers a large geographic range in North America, and previous studies reported that a better understanding of its singular influence on soil properties and processes is of high relevance for global change questions. Here we investigate the potential impact of a shift in aspen abundance on soil carbon sequestration and soil carbon stability at the continental scale by conducting a systematic literature review using 23 published studies. Our review shows that aspen's effect on soil carbon is relatively consistent throughout the species range. Aspen stores less C in the forest floor but similar amounts in the mineral soil relative to conifers. However, a robust set of indicators of soil C stability, for example, degree of organo-mineral associations, proportion of readily-available or labile C estimated during long-term soil incubations or using hot-water extraction, pattern of soil C distribution, and temperature sensitivity of soil heterotrophic respiration, reveals that the soil organic carbon (SOC) stock under aspen is more stable, rendering it more protected against environmental changes and soil disturbances. Therefore, our continental-scale analysis highlights that an increase in the abundance of trembling aspen in North American forests may increase the resistance and resilience of soil C stocks against global changes.

Can Carbon Fluxes Explain Differences in Soil Organic Carbon Storage under Aspen and Conifer Forest Overstories?

“…The SOC stocks found in the mineral soils at TWDEF are comparable to values found in other areas in North America [49][50][51][52]. However, aspen do not always have higher SOC stocks than conifers [53]. Laganiére et al [52] found higher mineral SOC pools under aspen in Ontario, but not in Quebec.…”

“…Also, Laganiére et al [56] found a higher proportion of SOC distributed as LF in conifer soils, and higher CO2 evolution from these soils during incubation [52]. Overall, higher stability of aspen SOC seems to be a consistent finding in literature, as reviewed by Laganiére et al [53]. The strong correlation between root and LF C suggests that the major source of LF in the deeper depths is root detritus.…”

Soil organic carbon stability in forests: Distinct effects of tree species identity and traits

“…To examine these hypotheses and other effects of tree species on SOM stability in mineral soils, we used a common garden with replicated, monoculture plots of eleven tree species to investigate the impact of 17 ecological factors on five different indicators of SOM stability: heterotrophic respiration from incubated soils, the proportion of total SOM present in relatively stable SOM pools (including C in POM <20 µm and C in MOM <20 µm; Mueller et al, ), and the relative abundance of both 14 C and 15 N in bulk SOM. Although previous studies from this common garden in Poland and similar plantations in Denmark have investigated the effects of litter traits on C stocks in mineral soils (Mueller, Eissenstat, et al, ; Mueller et al, ; Vesterdal, Clarke, Sigurdsson, & Gundersen, ), these studies provide limited information on SOM stability because it can vary independently of SOM stocks (Frank, Pontes, & McFarlane, ; Laganière et al, ). Here, the ecological factors investigated included chemical properties of leaf litter and fine roots, estimates of the magnitude of organic inputs to soil, rates of decomposition and turnover for leaf litter, fine roots, and the organic horizon, key descriptors of the soil biotic community, and physicochemical soil properties.…”

“…This potential varies with tree species, which can substantially impact soil organic C pools (e.g., Cremer, Kern, & Prietzel, 2017;Dawud et al, 2016;Mueller et al, 2015). Little information, though, is available on the impacts of different tree species on the stability of organic C in soil (Ahmed, Smith, Jones, & Godbold, 2016;Augusto et al, 2015;Laganière, Boča, Van Miegroet, & Paré, 2017). Because tree species composition in forests is dynamic (Ellison et al, 2005;Fisichelli, Frelich, & Reich, 2014;Leithead, Anand, & Silva, 2010), particularly under a changing climate (Iverson & Prasad, 2001;Reich et al, 2015;Zolkos et al, 2015), a more detailed knowledge of tree species effects on soil C stabilization is crucial for predicting the persistence of soil C in forest ecosystems.…”

Microbial Taxa and Soil Organic Carbon Accumulation Driven by Tree Roots

“…However, limitations due to the use of traditional techniques hinder an accurate evaluation of soil microbial taxa, which has greatly delayed our understanding of several core ecosystem processes, such as variations in microbial communities, soil C accumulation, ecosystem succession, and ecosystem functions [20,21]. Identifying and quantifying the relative influence of root-microbial systems in forests remains a challenge for researchers [22]. Thus, there is still a limited understanding of the relationship between soil microbial taxa and soil C accumulation in a changing environment, especially in restored forest ecosystems.…”