title: Temporal trends and sources of variation in carbon flux from coarse woody debris in experimental forest canopy openings.
abstract: Pulses of respiration from coarse woody debris (CWD) have been observed immediately following canopy disturbances, but it is unclear how long these pulses are sustained. Several factors are known to influence carbon flux rates from CWD, but few studies have evaluated more than temperature and moisture. We experimentally manipulated forest structure in a second-growth northern hardwood forest and measured CO2 flux periodically for seven growing seasons following gap creation. We present an analysis of which factors, including the composition of the wood-decay fungal community influence CO2 flux. CO2 flux from CWD was strongly and positively related to wood temperature and varied significantly between substrate types (logs vs. stumps). For five growing seasons after treatment, the CO2 flux of stumps reached rates up to seven times higher than that of logs. CO2 flux of logs did not differ significantly between canopy-gap and closed-canopy conditions in the fourth through seventh post-treatment growing seasons. By the seventh season, the seasonal carbon flux of both logs and stumps had decreased significantly from prior years. Linear mixed models indicated the variation in the wood inhabiting fungal community composition explained a significant portion of variability in the CO2 flux along with measures of substrate conditions. CO2 flux rates were inversely related to fungal diversity, with logs hosting more species but emitting less CO2 than stumps. Overall, our results suggest that the current treatment of CWD in dynamic forest carbon models may be oversimplified, thereby hampering our ability to predict realistic carbon fluxes associated with wood decomposition.
authors.affiliation: Department of Forest and Wildlife Ecology, University of Wisconsin-Madison, Madison, WI, 53706, USA. jforrester@wisc.edu.
authors.forename: J A
authors.initials: JA
authors.lastname: Forrester
authors.affiliation: Department of Forest and Wildlife Ecology, University of Wisconsin-Madison, Madison, WI, 53706, USA.
authors.forename: D J
authors.initials: DJ
authors.lastname: Mladenoff
authors.affiliation: Rubenstein School of Environment and Natural Resources, University of Vermont, Burlington, VT, 05405, USA.
authors.forename: A W
authors.initials: AW
authors.lastname: D'Amato
authors.affiliation: School of Forest Resources, University of Maine, Orono, ME, 04469, USA.
authors.forename: S
authors.initials: S
authors.lastname: Fraver
authors.affiliation: USDA Forest Service, Center for Forest Mycology Research, Madison, WI, 53726, USA.
authors.forename: D L
authors.initials: DL
authors.lastname: Lindner
authors.affiliation: Center for Agriculture, University of Massachusetts, Amherst, MA, 01002, USA.
authors.forename: N J
authors.initials: NJ
authors.lastname: Brazee
authors.affiliation: Department of Statistics, University of Wisconsin-Madison, Madison, WI, 53706, USA.
authors.forename: M K
authors.initials: MK
authors.lastname: Clayton
authors.affiliation: Department of Forestry and Environmental Resources, North Carolina State University, Raleigh, NC, 27695, USA.
authors.forename: S T
authors.initials: ST
authors.lastname: Gower
mesh_terms: D002244:Carbon / Q000032:analysis* / Q000378:metabolism; D057486:Carbon Cycle; D002245:Carbon Dioxide / Q000032:analysis / Q000378:metabolism; D065928:Forests; D005658:Fungi; D014197:Trees / Q000382:microbiology; D014934:Wood / Q000382:microbiology
chemical_list: D002245:Carbon Dioxide; D002244:Carbon
keywords: Canopy gap; Carbon flux; Coarse woody debris; Heterotrophic respiration; Stumps; Wood-decay fungi