자료유형  

 학위논문

Control Number  

0017163972

International Standard Book Number  

9798384485469

Dewey Decimal Classification Number  

595

Main Entry-Personal Name  

Foote, Gabriel Gene Zukosky.

Publication, Distribution, etc. (Imprint  

[S.l.] : University of California, Davis., 2024

Publication, Distribution, etc. (Imprint  

Ann Arbor : ProQuest Dissertations & Theses, 2024

Physical Description  

144 p.

General Note  

Source: Dissertations Abstracts International, Volume: 86-04, Section: A.

General Note  

Advisor: Chiu, Joanna.

Dissertation Note  

Thesis (Ph.D.)--University of California, Davis, 2024.

Summary, Etc.  

요약The introduction of livestock and wildfire suppression beginning in the mid-nineteenth century in the western United States have homogenized the structure of its mixed-conifer forests, where stands are unnaturally dense and exhibit higher rates of canopy and shrub cover compared to pre-suppression conditions. The increased continuity between surface fuels and tree crowns combined with climate change-driven droughts have exacerbated the severity-both in intensity and extent-of recent wildfires in the western US. Changes in vegetation and surface fuels resulting from altered disturbance regimes and human activities (e.g., silvicultural practices) are likely to influence the abundance and diversity of arthropod taxa and functional feeding guilds, many of which provide ecological services to forest ecosystems and surrounding landscapes. However, basic information on the community-level responses of most insect guilds to large-scale fire events is unavailable, despite increases in their occurrence in recent years. Similarly, thorough documentation of changes in insect community assemblages and diversity following various forest restoration efforts to prevent unnaturally large or severe wildfire is lacking for several ecoregions of the southwestern US. For this dissertation, I documented the community-level responses of bees (Hymenoptera: Apiformes) and yellowjacket wasps (Hymenoptera: Vespidae, Vespinae) to changes to forest structure following wildfire and restoration treatments in montane, coniferous forests of California and New Mexico, USA. Objectives and major findings from individual dissertation chapters are summarized below.Chapter one: I documented the early successional responses of bee communities and individual bee functional groups to the 2020 Creek Fire, a large-scale disturbance that burned several thousand hectares of submontane, montane, and upper montane mixed-conifer forest within the Sierra National Forest, California. The objectives of this research were to document post-fire relationships between stand-level burn severity and local bee diversity within these different biotic zones. I further determined whether these relationships' general patterns varied with time (one vs. two years post-fire) or along an elevational gradient. Across all biotic zones, bee communities were generally more abundant and speciose in burned versus unburned stands one year post-fire, regardless of local burn severity. During the following summer, however, bee abundance and species richness were generally highest in stands that burned at severities more representative of the local ecosystem's natural fire regime. We observed similar patterns between the abundance of individual bee functional groups and local burn severity within individual biotic zones and between sample years. Variation in local community assemblages also increased with fire severity and time since fire across all biotic zones. Increases in grass or shrub layers between years were likely correlated with changes in local bee abundance and diversity, particularly at lower elevations. Overall, our findings suggest that stand-level relationships between post-fire bee abundance or diversity and fire severity may vary along elevational gradients or among different forest types found within a large-scale wildfire boundary. The pattern of these relationships may also change between the early, successive years following these disturbances. Importantly, our observations suggest low to moderate intensity fire characteristic of prescribed burns used to restore or maintain the function of lower elevation, mixed-conifer forests in the Californian Sierra Nevada mountains will likely benefit bee communities at both local and regional scales.Chapter two: Regional-scale reductions in fire activity associated with centuries of logging and livestock grazing in the southwestern United States have contributed to the encroachment of pinyon pine and juniper (PJ) into high-elevation forests historically dominated by ponderosa pine. It is unclear whether alterations in overstory structure and ground cover conditions following PJ encroachment into ponderosa pine forests influence the diversity or community compositions of ecologically important insect groups like wild and native bees. I documented bee community and functional group responses to 1) variation in ponderosa pine cover within a montane PJ-ponderosa pine forested landscape in Northern New Mexico, and 2) stand-thinning operations used to restore a ponderosa pine-dominant overstory across the broader landscape. Overall, bees were significantly more abundant in stands with moderate to high amounts of ponderosa pine cover in comparison to stands that were dominated by pinyon pine and juniper. However, neither bee diversity nor local community structures were significantly affected by variation in overstory tree composition, possibly due to the relative uniformity in canopy structure and ground cover conditions across the study site. While local bee abundance may be reduced in stands with high amounts of PJ cover, these findings suggest that PJ encroachment likely does not negatively impact bee communities residing in forested landscapes historically dominated by ponderosa pine in this ecoregion. Regardless, management practices that reduce canopy closure, maintain or increase ponderosa pine dominance, and preserve or create key habitat features (snags, bare soil patches, and floral resources) are likely to benefit wild bees in these ecosystems.Chapter three: Documentation of the community-level responses of social yellowjacket wasps to wildfire in coniferous forests of the western United States is lacking, despite their ubiquitous distribution, ecological function and occasional pest status within these ecosystems. I sampled the local yellowjacket community along a burn severity gradient in montane, mixed-conifer stands located within various fire boundaries that occurred between 2015-2020 in the Californian Sierra Nevada mountains. I determined: 1) how post-burn patterns in yellowjacket abundance and diversity changed over time; and 2) how post-burn yellowjacket abundance and diversity varied along a burn severity gradient within individual fire boundaries. Regardless of burn severity, wildfire significantly reduced yellowjacket abundance and species richness during the immediate (≤ two) years following stand disturbance, possibly due to flame-induced wasp mortality combined with the destruction of above-ground foraging, nesting and overwintering substrates. Stands that burned at high severity within older fire boundaries had high rates of shrub and grass cover, and were predominantly inhabited by large numbers of pestiferous Vespula pennsylvanica wasps. Forest-obligate yellowjacket species were generally only collected in unburned stands or in locations that burned at relatively low severity. Combined, these results suggest unnaturally high severity fire within these forests might facilitate increases in pestiferous yellowjacket populations due to favorable stand conditions. In contrast, lower severity burns characteristic of prescribed fire used to restore or maintain the function of mixed-conifer forests in the Central Sierra Nevada may provide the added benefit of short-term reductions in unwanted yellowjacket population levels in areas of concern.

Subject Added Entry-Topical Term  

Entomology.

Subject Added Entry-Topical Term  

Ecology.

Subject Added Entry-Topical Term  

Wildlife management.

Subject Added Entry-Topical Term  

American studies.

Index Term-Uncontrolled  

Bees

Index Term-Uncontrolled  

Pollinators

Index Term-Uncontrolled  

Restoration

Index Term-Uncontrolled  

Wildfire

Index Term-Uncontrolled  

Yellowjackets

Added Entry-Corporate Name  

University of California, Davis Entomology

Host Item Entry  

Dissertations Abstracts International. 86-04A.

Electronic Location and Access  

로그인을 한후 보실 수 있는 자료입니다.

Control Number  

joongbu:656511