Accounting Carbon Storage in Decaying Root Systems of Harvested Forests

Abstract

Decaying root systems of harvested trees can be a significant component of belowground carbon storage, especially in intensively managed forests where harvest occurs repeatedly in relatively short rotations. Based on destructive sampling of root systems of harvested loblolly pine trees, we estimated that root systems contained about 32% (17.2 Mg ha -1 ) at the time of harvest, and about 13% (6.1 Mg ha -1 ) of the soil organic carbon 10 years later. Based on the published roundwood output data, we estimated belowground biomass at the time of harvest for loblolly-shortleaf pine forests harvested between 1995 and 2005 in South Carolina. We then calculated C that remained in the decomposing root systems in 2005 using the decay function developed for loblolly pine. Our calculations indicate that the amount of C stored in decaying roots of loblolly-shortleaf pine forests harvested between 1995 and 2005 in South Carolina was 7.1 Tg. Using a simple extrapolation method, we estimated 331.8 Tg C stored in the decomposing roots due to timber harvest from 1995 to 2005 in the conterminous USA. To fully account for the C stored in the decomposing roots of the US forests, future studies need (1) to quantify decay rates of coarse roots for major tree species in different regions, and (2) to develop a methodology that can determine C stock in decomposing roots resulting from natural mortality.

Modeling the effects of forest management on in situ and ex situ longleaf pine forest carbon stocks

“…We assumed that thinning was from below and the diameter class of thinned trees corresponded to the 35th percentile (D 35 , cm). A decay rate of 15, 12 and 10%/year mass loss was assumed for foliage, CWD and lateral roots (Gholz et al, 1985(Gholz et al, , 1986Radtke et al, 2009;Wang et al, 2012). For tap root decomposition we used the model reported by Anderson et al (2014).…”

Clearcutting alters decomposition processes and initiates complex restructuring of fungal communities in soil and tree roots

“…The standing mass of roots is stand-specific, but may be very high. For example, the root systems in a Pinus taeda plantation contained approximately 32% (17.2 Mg ha −1 ) of the soil organic carbon [27]. Dead roots appear to contain a substantial amount of labile C, as apparent from the observation that approximately 35% of standing root mass was lost during 1 year after clearcutting of a spruce-fir stand and it is also supported by the observation that in the first season after the clearcut, respiration was 16% higher than in the uncut stand [28].…”

Sampling volume in root studies: the pitfalls of under‐sampling exposed using accumulation curves

“…; Robinson ; Wang et al . ). Conversely, the ~30% of root biomass held in fine roots represents a relatively dynamic source of C flow from plant biomass into the soil via turnover.…”

“…2a), but for different reasons. The biomass of live and decaying coarse roots, which equal an estimated 50% of stem biomass, represents a substantial and relatively stable pool of belowground C storage that is suggested to be largely underestimated (Albaugh et al 2006;Robinson 2007;Wang et al 2012). Conversely, the~30% of root biomass held in fine roots represents a relatively dynamic source of C flow from plant biomass into the soil via turnover.…”