Decomposition rates of American chestnut (Castanea dentata) wood and implications for coarse woody debris pools

Abstract

Observations of the rapid growth and slow decomposition of American chestnut (Castanea dentata (Marsh.) Borkh.) suggest that its reintroduction could enhance terrestrial carbon (C) sequestration. A suite of decomposition models was fit with decomposition data from coarse woody debris (CWD) sampled in Wisconsin and Virginia, U.S. The optimal (two-component exponential) model was integrated with generic growth curves and documented longevity and typical stem density to evaluate how CWD and biomass pools relate to decomposition. CWD decomposed faster in Wisconsin (4.3% ± 0.3% per year) than in Virginia (0.7% ± 0.01% per year), and downed dead wood decomposed faster (8.1% ± 1.9% per year) than standing dead wood (0.7% ± 0.0% per year). We predicted considerably smaller CWD pools in Wisconsin (maximum 41 ± 23 Mg C·ha -1 ) than in Virginia (maximum 98 ± 23 Mg C·ha -1 ); the predicted biomass pool was larger in the faster growing Wisconsin trees (maximum 542 ± 58 Mg C·ha -1 ) compared with slower growing trees in Virginia (maximum 385 ± 51 Mg C·ha -1 ). Sensitivity analysis indicated that accurate estimates of decomposition rates are more urgent in fertile locations where growth and decomposition are rapid. We conclude that the American chestnut wood is intermediate in resistance to decomposition. Due to the interrelatedness of growth and decomposition rates, CWD pool sizes likely do not depend on species alone but on how the growth and decomposition of individual species vary in response to site productivity.Résumé : Les observations ayant trait à la croissance rapide et à la décomposition lente du châtaignier d'Amérique (Castanea dentata (Marsh.) Borkh.) indiquent que sa réintroduction pourrait accroître la séquestration terrestre du carbone. Une série de modèles de décomposition ont été ajustés aux données de décomposition de débris ligneux grossiers (DLG) échantillonnés au Wisconsin et en Virginie, aux États-Unis. Le modèle optimal (exponentiel à deux composantes), des courbes génériques de croissance, la longévité documentée et la densité typique de la tige ont été intégrés pour évaluer comment les DLG et les réservoirs de biomasse sont reliés à la décomposition. Les DLG se décomposaient plus rapidement au Wisconsin (4,3 ± 0,3 %·an -1 ) qu'en Virginie (0,7 ± 0,01 %·an -1 ) et les débris au sol se décomposaient plus rapidement (8,1 ± 1,9 %·an -1 ) que les débris sur pied (0,7 ± 0,0 %·an -1 ). Nous avons prédit que les réservoirs de DLG seraient considérablement plus petits au Wisconsin (maximum de 41 ± 23 Mg C·ha -1 ) qu'en Virginie (maximum de 98 ± 23 Mg C·ha -1 ); nous avons aussi prédit que le réservoir de biomasse serait plus gros chez les arbres du Wisconsin qui croissent plus vite (maximum de 542 ± 58 Mg C·ha -1 ) comparativement à ceux de la Virginie (maximum de 385 ± 51 Mg C·ha -1 ). Une analyse de sensibilité a indiqué qu'il était plus urgent d'obtenir des estimations précises du taux de décomposition dans les endroits fertiles où la croissance et la décomposition sont rapides. Nous arrivons à la conclusion...

The implications of American chestnut reintroduction on landscape dynamics and carbon storage

“…However, our simulations did show that Aggressive chestnut restoration can lead to a positive shift in the predicted biomass distribution of woody debris stocks, most likely due to the fact that chestnut wood decays at an unusually slow rate (De Bruijn et al. ). To the extent that dead wood is relatively resistant to disturbance (other than fire), locking carbon into slow‐decaying woody tissues may have a positive effect on the length of carbon storage, even if it does not affect the total mass of stored carbon.…”

“…Because American chestnut is fast-growing, long-lived, and resistant to decay (Youngs 2000, Ellison et al 2005, De Bruijn et al 2014a, its restoration could result in increased carbon sequestration and storage in the form of living and dead trees and durable wood products. Recent research on American chestnut ecology and silvics (i.e., growth, competitiveness, ecophysiology) in blight-free plantations has found superior growth compared to co-occurring species (Jacobs andSevereid 2004, McEwan et al 2006).…”

“…In fact, it appears that they store as much carbon in their boles as do other fast-growing species used for forestry plantations in southwest Wisconsin (Jacobs et al 2009). Given relatively low decay rate of chestnut wood (De Bruijn et al 2014a), this carbon also would be expected to remain in storage for a longer period. However, the potential for American chestnut to influence carbon dynamics at landscape scales remains uncertain because interacting factors such as competitors and relative resilience to the dominant disturbances influence these dynamics, and because we do not know how well American chestnut will be able to establish itself in contemporary forests.…”

“…Jacobs et al (2009) observed remarkable growth rates of chestnut, with trees consistently reaching diameter at breast height increments >1.5 cm/yr over at least the first two decades of development. De Bruijn et al (2014a) predicted that in a hypothetic monoculture, American chestnut could maintain an annual increment of 5-7 m 3 /ha for 200 yr or more. The generic parameters used for all other species were also assigned to chestnut.…”

Forecasting effects of tree species reintroduction strategies on carbon stocks in a future without historical analog

“…Net photosynthates are allocated to four pools: foliage, wood, roots and nonstructural carbon reserves. Biomass is moved to woody and litter dead pools through turnover or mortality (including by disturbances), which decay according to species‐specific decomposition rates (see Gustafson, De Bruijn, et al, and De Bruijn et al () for details). Carbon stocks in mineral soil are not tracked, but soil carbon tends to be the most stable of the carbon pools (Jackson et al, ).…”