Interspecific wood trait variation predicts decreased carbon residence time in changing forests

1. Increasing disturbance will result in a significant flux in aboveground carbon (C) from live trees to deadwood, concurrent with compositional shifts. While interspecific decay variation is widely reported, the implications of forest compositional change on ecosystem-level deadwood decay and consequently, the future of a globally significant C pool have not been previously explored. 2. Leveraging a 25-year treefall record for two eastern hardwood forests in central Illinois, USA, we used a chronosequence approach to estimate downed deadwood decay rates for eight common tree taxa. We hypothesized the increasing dominance of Acer spp. in eastern forests, due to disturbance regime changes, is driving a decrease in the mean species-weighted deadwood decay rate, decreasing the total C storage capacity of regional forests. 3. We observed significantly greater interspecific variation in deadwood decay rates than short- term studies, with a thirteen-fold difference in half-lives between Aesculus glabra (T1/2 = 6.4 years) and Quercus spp. (T1/2 = 77.8) logs. The canopy-dominant Acer saccharum (T1/2 = 17.8) decayed significantly faster than other historically dominant eastern taxa, Quercus spp. and Fraxinus spp. (T1/2 = 47.4). At multi-decadal timescales, wood traits, notably taxon initial wood C:N ratio and Mn concentration, outweighed environmental factors in explaining variation in decay rates. A significant interaction between soil pH and wood Mn, which co-regulate microbial lignin degradation, suggests a similar importance of Mn in modulating woody debris decay rates as has been previously described for litter decay. 4. Synthesis. Our decay estimates highlight the importance of long-term studies for accurately assessing decay of recalcitrant species (high C:N ratio), as short-term decay studies are prone to underestimating their decay rates. Our results suggest that current and future forest compositional changes will have direct consequences on the residence time of the deadwood C pool due to interspecific wood trait variation.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Ecol, Evol, Conservation Biol

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2020

Author dc:creator

• Perez, Sierra Brown

Contributors dc:contributor

• Dalling, James W
• Fraterrigo, Jennifer M
• Yang, Wendy H
• Yannarell, Anthony C

• Deadwood
• carbon storage
• decay
• disturbance

Statement dc:rights

• Copyright 2020 Sierra Perez

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/108520

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/108520