Author: Sarah T. HammanPublisher:
ISBN:
Category : Fire ecology
Languages : en
Pages : 182
Book Description
Altered Fire Regime Impacts on the Soil Biogeochemistry and Microbial Community Structure of Mixed Conifer and Ponderosa Pine Forests
Author: Sarah T. HammanPublisher:
ISBN:
Category : Fire ecology
Languages : en
Pages : 182
Book Description
Wildfire Impacts on Soil Carbon Pools and Microbial Communities in Mixed-conifer Forests of California
Author: Jaron AdkinsPublisher:
ISBN:
Category : Electronic dissertations
Languages : en
Pages : 262
Book Description
Forest ecosystems are important reservoirs for long term carbon (C) storage. Forests of the western United States account for 20-40% of total U.S. carbon C sequestration, and nearly half of the total C in these forests is stored in soil. However, many forests in the western U.S are experiencing wildfire conditions that diverge from historical fire regimes. Prior to Euro-American settlement, California's mixed-conifer forests typically experienced frequent surface fires of low to moderate burn severity, but, due to the combined effects of altered forest structure and climate change, now experience fires that are larger and more severe than historical conditions. Fires have numerous direct and indirect effects on the soil biological, chemical, and physical characteristics that influence the soil C cycle. Understanding how altered soil characteristics influence the cycling and persistence of soil C, and how they vary with severity, is important for managing forests for C storage and for predicting fire-climate feedbacks. My dissertation work incorporates observational and manipulative experiments to understand the direct and indirect effects of burn severity on soil C cycling and microbial communities over the short to intermediate term, with a particular focus on the distribution of soil C between active and slow cycling pools. Soil C can be conceptualized as discrete pools of variable persistence in soil. The active C pool is quickly decomposed, contributing to the return of CO2 to the atmosphere, whereas the non-active C pool is more stable and contributes to long term C storage. I leveraged a burn severity gradient resulting from a wildfire in a California mixed-conifer forest to determine the structure and kinetics of these C pools at an intermediate time point in post-fire recovery (i.e. three years). I found that the size of the non-active C pool was smaller in burned areas than unburned areas, and the kinetic rate of the non-active C pool was negatively related to burn severity. I also characterized the soil microbial communities across this severity gradient and identified the environmental characteristics responsible for differences. I found that fungal-to-bacterial ratio and oligotroph-to-copiotroph bacteria ratio decreased with burn severity, and these effects were driven by differences in live and dead tree basal area, soil nutrients, and pH. Leveraging another burn severity gradient, I then determined whether differences in microbial communities and soil C pools were related one-year post-fire in a mixed-conifer forest. I again found lower non-active C pool kinetic rates, and higher abundances of copiotrophic bacteria in burned compared to unburned areas. Differences in soil C pool kinetics were related to tree basal area, soil nutrients, and bacterial communities.I determined the short-term impacts of fire on soil C pools and cycling using lab experiments in which I manipulated soil heating intensity and pyrogenic organic matter (PyOM) additions. I found that high intensity soil heating can decrease microbial biomass C (MBC) accumulation, whereas PyOM had minimal effects on MBC in the short-term. Finally, I found that the size of the active C pool increased with soil heating intensity, while the kinetic rate of the non-active C pool decreased; PyOM primarily increased the size of the non-active C pool. Taken as a whole, my research suggests that fire induces short-term soil C losses by increasing the size of the active C pool, but, over the intermediate-term, residual soil C is more persistent. Fire severity is predicted to increase globally throughout the 21st century, and my research contributes to understanding how forest C storage will be affected by disrupted wildfire regimes.
Fire Effects on Soil Microbial Community Structure and Function in a Ponderosa Pine Ecosystem
Author: Aida E. Jiménez EsquilínPublisher:
ISBN:
Category : Forest ecology
Languages : en
Pages : 368
Book Description
Historical Fire Regimes in Ponderosa Pine Forests of the Colorado Front Range, and Recommendations for Ecological Restoration and Fuels Management
Author: Merrill R. KaufmannPublisher:
ISBN:
Category : Fire ecology
Languages : en
Pages : 22
Book Description
The Effect of Fire on Vegetation in Ponderosa Pine Forests
Author: Henry A. WrightPublisher:
ISBN:
Category : Fire ecology
Languages : en
Pages : 36
Book Description
The Relationship Between Forest Fires and Forest Dynamics in California's North Coast Bioregion: how Altered Fire Regimes Have Affected the Vegetative Outcomes of Oak Woodlands and Mixed Conifer Forests
Author: Max BencomoPublisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
Wildfire is a necessary part of ecosystem function in California, but fire suppression and the spread of invasive species have endangered many ecosystems. The North Coast bioregion of California has seen dramatic shifts in forest ecology and vegetative density, largely due to the disruption of historic fire regimes. Historic fire regimes were previously maintained through indigenous land management, but the arrival of European settlers in the 1850's initiated the changes reflected in current fire regimes. Not only is the North Coast bioregion the hotbed of recent fire activity, it is experiencing decreased counts of heterogeneity within forests while also seeing increased amounts of fuel loads that contribute to more severe fires. This paper utilizes a comparative analysis of mixed conifer forest and oak woodland ecozones, describing the vegetative outcomes of their altered fire regimes. Through the synthesis of case studies, government reports, impact assessments, and management plans, I investigated the current state of these landscapes and developed recommendations for future management. The combination of fire suppression and increasing invasive populations have led to numerous shifts in forest systems. Invasive species heavily influence forest fuel loads and can change ecosystem structure, which can subsequently alter the area's fire regime. Once a fire regime has changed it can imperil the livelihood of historic plant populations. Conifer forests are seeing shifts from resilient species to more fire-sensitive species, which can lead to the decimation of entire populations by high-severity fires. Oak woodlands are also suffering from fire regime changes, as conifers are encroaching and overtaking the forest canopy, drowning out oaks and reducing them to shrub species. Both mixed conifer forests and oak woodlands are threatened by changes in their respective fire regimes. These shifts in vegetation patterns can be amended through integrative management initiatives, notably the application of prescribed burns to aid the restoration of historical fire regimes.
The Effects of Fire and Fuels Reduction Treatments on Fire Hazard and Soil Carbon Respiration in a Sierra Nevada Pine Plantation
Author: Leda Nikola KobziarPublisher:
ISBN:
Category : Forest fires
Languages : en
Pages : 416
Book Description
"Throughout fire-adapted forests of the western US, and in the Sierra Nevada of California specifically, wildfire suppression has produced forest structures conducive to more severe, costly, and ecologically deleterious fires. Recent legislation has identified the necessity of management practices that manipulate forests towards less fire-hazardous structures. In the approximately 30 year old pine plantations of the Stanislaus National Forest, extensive fuels reduction procedures are being implemented. This dissertation addresses whether silvicultural and burning treatments are effective at reducing the intensity and severity of potential fire behavior, and how, along with wildfire, these treatments impact the evolution of carbon dioxide from the soil to the atmosphere. The first chapter addresses the relationships between soil respiration, tree injury, and forest floor characteristics in high and low severity wildfire burn sites in a salvage-logged mixed-conifer forest. The results indicate that fire severity influences soil CO2 efflux and should be considered in ecosystem carbon modeling. In the next chapter, fire models suggest that mechanical shredding of understory vegetation (mastication) is detrimental, and prescribed fire most effective in reducing potential fire behavior and severity in pine plantations. The third chapter documents the impact of alternative fuels treatments on soil carbon respiration patterns in the pine plantations, and shows that mastication produces short-term reductions in respiration rates and soil moisture. The final chapter further examines the relationships of fire-induced tree injuries, forest floor structure, and environmental factors to soil respiration response to fuels treatments. Each chapter is written as an independent manuscript; they collectively serve to expand the limited understanding of the effectiveness and ecological consequences of fire and fuels treatments in coniferous forests."--Abstract
Fire and Fire Surrogate Effects on Soil Properties in a Sierra Nevada Mixed-conifer Forest
Author: Emily Eleanor Yukie MoghaddasPublisher:
ISBN:
Category :
Languages : en
Pages : 316
Book Description
Impacts of Post-fire Salvage Logging on Soil Chemistry, Physical Properties and Bacterial Community Composition in a Mixed-conifer Forest in Central Oregon
Author: Tara Nicolle JenningsPublisher:
ISBN:
Category : Forest soils
Languages : en
Pages : 144
Book Description
Land managers, scientists, and the interested public are confronted with uncertainty about the impacts of salvage logging on soil productivity. In recent years, stand-replacing wildfires in the western United States have increased in frequency, prompting the need to evaluate the effect of post-fire treatments on forest ecosystem recovery. This study examined whether compaction and subsoiling after post-fire salvage logging impacted the structure, metabolism, and function of soil bacterial communities, which were assessed using terminal restriction fragment length polymorphism (T-RFLP) and Biolog Ecoplates. Supporting data for these salvage logging effects included soil biological activities, soil chemistry, and physical soil properties in a mixed conifer forest in central Oregon. Post-fire salvage logging treatments had little effect on soil bacterial community richness, suggesting that soil bacteria in these post-fire landscapes are both tolerant of the occurrence of fires and resilient to disturbance. However, even though a statistically significant difference in bacterial species richness was not detected among treatments, a greater cumulative mean number of species was found across six sampling seasons in the compacted soil treatment compared to the fire-only and subsoiled treatments. This trend may be due to less predation on the soil bacteria by microbivores in the soil pores reduced in size by compaction. Additionally, there was a significant decline in the mean number of species after the spring 2007 sampling. A NMS ordination of the mean number of species suggested that the bacterial community composition changed after spring 2007. Furthermore, the lack of difference in mean number of species among treatments suggests that time since fire had a stronger effect on the structure of the soil bacterial community than did logging disturbance. Plant-available phosphorus and nitrogen concentrations were lower in the mechanically disturbed treatments than in the fire-only treatment. Soil respiration and soil phosphatase rates both were higher in the fire-only treatment. Mechanical disturbance may have long-lasting effects in an already nutrient limited system. No other differences among treatments for soil chemical properties were detected. Soil bulk density was lowest in the subsoiled treatment. Microbial community responses to burning and compaction caused by harvesting can be negative, neutral, or positive. While many factors, in addition to soil chemical and physical properties, affect the microbial community richness and functional diversity, our results support other recent studies showing that soil bacteria are resilient in disturbed environments.
Historical Wildfire Impacts on Ponderosa Pine Tree Overstories
Author: Peter F. FfolliottPublisher:
ISBN:
Category : Forest fires
Languages : en
Pages : 28
Book Description
The Rodeo-Chediski Wildfire--the largest in Arizona's history--damaged or destroyed ecosystem resources and disrupted ecosystem functioning in a largely mosaic pattern throughout the ponderosa pine (Pinus ponderosa) forests exposed to the burn. Impacts of this wildfire on tree overstories were studied for 5 years (2002 to 2007) on two watersheds in the area burned. One watershed was burned by a high severity (stand-replacing) fire, while the other watershed was burned by a low severity (stand-modifying) fire. In this paper, we focus on the effects of the wildfire on stand structures, post-fire mortality of fire-damaged trees, and stocking of tree reproduction. We also present a fire severity classification system based on the fire-damaged tree crowns and a retrospective description of fire behavior on the two burned watersheds.