ABSTRACT Background/Question/Methods Monocultures and diverse mixtures of perennial bioenergy cro... more ABSTRACT Background/Question/Methods Monocultures and diverse mixtures of perennial bioenergy crops are being considered for sustainable energy feedstocks, and diverse mixtures offer additional value by increasing species diversity and providing wildlife habitat. Perennial cropping systems are known to enhance ecosystem services relative to annual crops; however, the difference in services provided by perennial monocultures versus diverse species mixtures is not yet well understood. We investigated belowground ecosystem effects of a monoculture of switchgrass (Panicum virgatum) and a diverse mixture of native grassland species established on erodible agricultural land in SW Wisconsin, USA. These crops were established in 2008 and received a treatment of prescribed fire or no fire in 2009. We estimated the effects of species diversity and prescribed fire on N availability, net mineralization rate, and soil respiration in May, July and September 2010. We also measured activities of 8 microbial exoenzymes in September 2010. Results/Conclusions Preliminary analyses indicate that species composition and burning did not affect N availability and net mineralization rates. N availability was greatest and net mineralization rate was lowest in July, relative to May and September. Soil respiration in was increased by fire in the monoculture and decreased by fire in the diverse mixture in July, and the opposite trend was observed in September. Soil respiration decreased over time in the burned monoculture and unburned diverse mixture. Analyses of microbial exoenzyme activities will be presented. Together, the processes we evaluated elucidate the effects of plant species diversity and fire on overall resource availability and nutrient cycling across a growing season. These results will help evaluate the effects of alternative bioenergy crops on ecosystem function.
ABSTRACT Background/Question/Methods Monocultures and diverse mixtures of perennial bioenergy cro... more ABSTRACT Background/Question/Methods Monocultures and diverse mixtures of perennial bioenergy crops are being considered for sustainable energy feedstocks, and diverse mixtures offer additional value by increasing species diversity and providing wildlife habitat. Perennial cropping systems are known to enhance ecosystem services relative to annual crops; however, the difference in services provided by perennial monocultures versus diverse species mixtures is not yet well understood. We investigated belowground ecosystem effects of a monoculture of switchgrass (Panicum virgatum) and a diverse mixture of native grassland species established on erodible agricultural land in SW Wisconsin, USA. These crops were established in 2008 and received a treatment of prescribed fire or no fire in 2009. We estimated the effects of species diversity and prescribed fire on N availability, net mineralization rate, and soil respiration in May, July and September 2010. We also measured activities of 8 microbial exoenzymes in September 2010. Results/Conclusions Preliminary analyses indicate that species composition and burning did not affect N availability and net mineralization rates. N availability was greatest and net mineralization rate was lowest in July, relative to May and September. Soil respiration in was increased by fire in the monoculture and decreased by fire in the diverse mixture in July, and the opposite trend was observed in September. Soil respiration decreased over time in the burned monoculture and unburned diverse mixture. Analyses of microbial exoenzyme activities will be presented. Together, the processes we evaluated elucidate the effects of plant species diversity and fire on overall resource availability and nutrient cycling across a growing season. These results will help evaluate the effects of alternative bioenergy crops on ecosystem function.
Fire suppression and changing climate have resulted in increased large wildfire frequency and sev... more Fire suppression and changing climate have resulted in increased large wildfire frequency and severity in the western United States, causing carbon cycle impacts. Forest thinning and prescribed burning reduce high-severity fire risk, but require removal of biomass and emissions of carbon from burning. During each fire a fraction of the burning vegetation and soil organic matter is converted into charcoal, a relatively stable carbon form. We sought to quantify the effects of pre-fire fuel load and type on charcoal carbon produced by biomass combusted in a prescribed burn under different thinning treatments and to identify more easily measured predictors of charcoal carbon mass in a historically frequent-fire mixed-conifer forest. We hypothesized that charcoal carbon produced from coarse woody debris (CWD) during prescribed burning would be greater than that produced from fine woody debris (FWD). We visually quantified post-treatment charcoal carbon content in the O-horizon and the A-horizon beneath CWD (> 30 cm diameter) and up to 60 cm from CWD that was present prior to treatment. We found no difference in the size of charcoal carbon pools from CWD (treatment means ranged from 0.3-2.0 g m-2 of A-horizon and 0.0-1.7 g m-2 of O-horizon charcoal) and FWD (treatment means ranged from 0.2-1.7 g m-2 of A-horizon and 0.0-1.5 g m-2 of O-horizon charcoal). We also compared treatments and found that the burn-only, understory-thin and burn, and overstory-thin and burn treatments had significantly more charcoal carbon than the control. Charcoal carbon represented 0.29% of total ecosystem carbon. We found that char mass on CWD was an important predictor of charcoal carbon mass, but only explained 18-35% of the variation. Our results help improve our understanding of the effects forest restoration treatments have on ecosystem carbon by providing additional information about charcoal carbon content.
ABSTRACT Background/Question/Methods Fire is a key natural disturbance in the Laurentian mixed fo... more ABSTRACT Background/Question/Methods Fire is a key natural disturbance in the Laurentian mixed forests of the Great Lakes region, USA. Recent patterns of prolonged regional drought suggest that the ecological effects of wildfire may become increasingly severe due to increased forest susceptibility to fire. Although soil organic matter content and characteristics are important controls on post-fire forest soil nutrient availability and forest recovery, our current understanding of how contrasting levels of fire severity influence soil organic matter is limited. The 2011 Pagami Creek wildfire in northern Minnesota was a historical fire event and resulted in a range of fire severity levels determined via remote sensing and field measurements. To evaluate the effects of fire severity on forest soil organic matter, we quantified post-fire (October-November 2011) total soil carbon (C) and nitrogen (N) using elemental analysis, and black (pyrogenic) C using nuclear magnetic resonance (NMR) spectroscopy in areas classified as low to high fire severity. Results/Conclusions Relative to unburned reference soils, soil total C content in the organic soil layer decreased in high-severity areas, whereas no significant effect occurred in low- or moderate-severity areas. There were no effects of fire or fire severity level on soil total C content in the 0-10 cm or 10-20 cm mineral soil depths, or on soil total N content in organic or mineral soil. Fire decreased soil C:N ratio in organic and mineral soil layers. The magnitude of fire effect on soil C:N ratio increased with fire severity in the organic soil layer, and decreased with depth. Results on pyrogenic C content and relationships with soil total C and N contents, and C:N ratio will be presented. Our results indicate that fire effects on soil C content and C:N ratio are limited primarily to the organic soil layer, and that effects on mineral soil are minimal. These results represent short-term fire effects, and provide a baseline for evaluating longer-term effects due to altered organic matter composition. Understanding the environmental effects of forest fire as a function of fire severity is critical for developing appropriate forest management policies and practices that minimizing detrimental effects and promote long-term resilience of fire-prone forests.
ABSTRACT Background/Question/Methods Monocultures and diverse mixtures of perennial bioenergy cro... more ABSTRACT Background/Question/Methods Monocultures and diverse mixtures of perennial bioenergy crops are being considered for sustainable energy feedstocks, and diverse mixtures offer additional value by increasing species diversity and providing wildlife habitat. Perennial cropping systems are known to enhance ecosystem services relative to annual crops; however, the difference in services provided by perennial monocultures versus diverse species mixtures is not yet well understood. We investigated belowground ecosystem effects of a monoculture of switchgrass (Panicum virgatum) and a diverse mixture of native grassland species established on erodible agricultural land in SW Wisconsin, USA. These crops were established in 2008 and received a treatment of prescribed fire or no fire in 2009. We estimated the effects of species diversity and prescribed fire on N availability, net mineralization rate, and soil respiration in May, July and September 2010. We also measured activities of 8 microbial exoenzymes in September 2010. Results/Conclusions Preliminary analyses indicate that species composition and burning did not affect N availability and net mineralization rates. N availability was greatest and net mineralization rate was lowest in July, relative to May and September. Soil respiration in was increased by fire in the monoculture and decreased by fire in the diverse mixture in July, and the opposite trend was observed in September. Soil respiration decreased over time in the burned monoculture and unburned diverse mixture. Analyses of microbial exoenzyme activities will be presented. Together, the processes we evaluated elucidate the effects of plant species diversity and fire on overall resource availability and nutrient cycling across a growing season. These results will help evaluate the effects of alternative bioenergy crops on ecosystem function.
ABSTRACT Background/Question/Methods Monocultures and diverse mixtures of perennial bioenergy cro... more ABSTRACT Background/Question/Methods Monocultures and diverse mixtures of perennial bioenergy crops are being considered for sustainable energy feedstocks, and diverse mixtures offer additional value by increasing species diversity and providing wildlife habitat. Perennial cropping systems are known to enhance ecosystem services relative to annual crops; however, the difference in services provided by perennial monocultures versus diverse species mixtures is not yet well understood. We investigated belowground ecosystem effects of a monoculture of switchgrass (Panicum virgatum) and a diverse mixture of native grassland species established on erodible agricultural land in SW Wisconsin, USA. These crops were established in 2008 and received a treatment of prescribed fire or no fire in 2009. We estimated the effects of species diversity and prescribed fire on N availability, net mineralization rate, and soil respiration in May, July and September 2010. We also measured activities of 8 microbial exoenzymes in September 2010. Results/Conclusions Preliminary analyses indicate that species composition and burning did not affect N availability and net mineralization rates. N availability was greatest and net mineralization rate was lowest in July, relative to May and September. Soil respiration in was increased by fire in the monoculture and decreased by fire in the diverse mixture in July, and the opposite trend was observed in September. Soil respiration decreased over time in the burned monoculture and unburned diverse mixture. Analyses of microbial exoenzyme activities will be presented. Together, the processes we evaluated elucidate the effects of plant species diversity and fire on overall resource availability and nutrient cycling across a growing season. These results will help evaluate the effects of alternative bioenergy crops on ecosystem function.
Fire suppression and changing climate have resulted in increased large wildfire frequency and sev... more Fire suppression and changing climate have resulted in increased large wildfire frequency and severity in the western United States, causing carbon cycle impacts. Forest thinning and prescribed burning reduce high-severity fire risk, but require removal of biomass and emissions of carbon from burning. During each fire a fraction of the burning vegetation and soil organic matter is converted into charcoal, a relatively stable carbon form. We sought to quantify the effects of pre-fire fuel load and type on charcoal carbon produced by biomass combusted in a prescribed burn under different thinning treatments and to identify more easily measured predictors of charcoal carbon mass in a historically frequent-fire mixed-conifer forest. We hypothesized that charcoal carbon produced from coarse woody debris (CWD) during prescribed burning would be greater than that produced from fine woody debris (FWD). We visually quantified post-treatment charcoal carbon content in the O-horizon and the A-horizon beneath CWD (> 30 cm diameter) and up to 60 cm from CWD that was present prior to treatment. We found no difference in the size of charcoal carbon pools from CWD (treatment means ranged from 0.3-2.0 g m-2 of A-horizon and 0.0-1.7 g m-2 of O-horizon charcoal) and FWD (treatment means ranged from 0.2-1.7 g m-2 of A-horizon and 0.0-1.5 g m-2 of O-horizon charcoal). We also compared treatments and found that the burn-only, understory-thin and burn, and overstory-thin and burn treatments had significantly more charcoal carbon than the control. Charcoal carbon represented 0.29% of total ecosystem carbon. We found that char mass on CWD was an important predictor of charcoal carbon mass, but only explained 18-35% of the variation. Our results help improve our understanding of the effects forest restoration treatments have on ecosystem carbon by providing additional information about charcoal carbon content.
ABSTRACT Background/Question/Methods Fire is a key natural disturbance in the Laurentian mixed fo... more ABSTRACT Background/Question/Methods Fire is a key natural disturbance in the Laurentian mixed forests of the Great Lakes region, USA. Recent patterns of prolonged regional drought suggest that the ecological effects of wildfire may become increasingly severe due to increased forest susceptibility to fire. Although soil organic matter content and characteristics are important controls on post-fire forest soil nutrient availability and forest recovery, our current understanding of how contrasting levels of fire severity influence soil organic matter is limited. The 2011 Pagami Creek wildfire in northern Minnesota was a historical fire event and resulted in a range of fire severity levels determined via remote sensing and field measurements. To evaluate the effects of fire severity on forest soil organic matter, we quantified post-fire (October-November 2011) total soil carbon (C) and nitrogen (N) using elemental analysis, and black (pyrogenic) C using nuclear magnetic resonance (NMR) spectroscopy in areas classified as low to high fire severity. Results/Conclusions Relative to unburned reference soils, soil total C content in the organic soil layer decreased in high-severity areas, whereas no significant effect occurred in low- or moderate-severity areas. There were no effects of fire or fire severity level on soil total C content in the 0-10 cm or 10-20 cm mineral soil depths, or on soil total N content in organic or mineral soil. Fire decreased soil C:N ratio in organic and mineral soil layers. The magnitude of fire effect on soil C:N ratio increased with fire severity in the organic soil layer, and decreased with depth. Results on pyrogenic C content and relationships with soil total C and N contents, and C:N ratio will be presented. Our results indicate that fire effects on soil C content and C:N ratio are limited primarily to the organic soil layer, and that effects on mineral soil are minimal. These results represent short-term fire effects, and provide a baseline for evaluating longer-term effects due to altered organic matter composition. Understanding the environmental effects of forest fire as a function of fire severity is critical for developing appropriate forest management policies and practices that minimizing detrimental effects and promote long-term resilience of fire-prone forests.
Uploads
Papers by Jessica Miesel