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Soil Respiration Response to Disturbance in a Northern Michigan Forest
Flynn, Conor R.

2012, Master of Science, Ohio State University, Environment and Natural Resources.
Carbon storage in eastern U.S. forests is threatened by stem-girdling invasive insects, along with natural succession as pioneer tree species age and die. In Northern lower Michigan we are investigating the impact of these intermediate disturbances on above- and below-ground carbon cycling across a mixed hardwood and pine forest. In spring 2008, early successional tree species, such as aspen (Populus grandidenta and P. tremuloides), were experimentally girdled in the Forest Accelerated Succession Experiment (FASET), while a nearby long-term research site, Ameriflux (AF), remained undisturbed. Soil respiration (Rs) is known to be responsive to disturbance and comprises the largest fraction of total ecosystem respiration (Re). However, determining effects of management on Rs is complicated by difficulties accurately measuring temporal variability in soil respiration and biophysical controlling factors such as soil temperature and soil water content (SWC). The objective of this study was to quantify Rs (soil CO2 efflux) and its constraints and drivers in disturbed and undisturbed forests and under early successional and late successional tree species. Rs, temperature, and SWC were intensively measured at four instrumented sites and extensively measured across the landscape along a number of 1km transects. A nested study design featured paired sites under early- and late-successional tree canopies (aspen and oak) in disturbed and undisturbed forest (FASET and AF). Rs was measured every hourly at the soil pits using an automated closed-chamber CO2 efflux system and biweekly along the 1km transects using a portable closed-chamber CO2 efflux system. Rs decreased under the canopy of disturbed aspen trees compared to controls aspen trees but was unchanged under the canopy of disturbed oak trees compared to control oak trees. Temperature sensitivity of Rs, as measured by a Q10 analysis, decreased under both aspen and oak trees in the disturbed forest compared to the control forest, indicating a possible decoupling between biophysical drivers and Rs following disturbance. A wavelet coherence analysis showed time-varying patterns of Rs responses to temperature and moisture, allowing inspection of diurnal Rs hysteresis as well as large effluxes associated with intermittent precipitation events. The results of this study show that further research is needed on the underlying mechanisms that control soil respiration and ultimately the C cycle of disturbed forest ecosystems.
Peter Curtis (Committee Chair)
Richard Dick (Committee Member)
Gil Bohrer (Committee Member)
103 p.

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Flynn, Conor. "Soil Respiration Response to Disturbance in a Northern Michigan Forest." Electronic Thesis or Dissertation. Ohio State University, 2012. OhioLINK Electronic Theses and Dissertations Center. 22 Aug 2017.

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Flynn, Conor "Soil Respiration Response to Disturbance in a Northern Michigan Forest." Electronic Thesis or Dissertation. Ohio State University, 2012. https://etd.ohiolink.edu/

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