High Nature Value farmland (HNVf) refers to traditional agricultural landscapes which support high levels of biodiversity. HNVf is declining across Europe, through both intensification and abandonment, raising concerns about the conservation of species associated with it. One argument is that such HNV species are better described as being dependent on disturbance, and that management practices on HNVf mimics the effects of natural disturbance processes such as herbivory, fire, severe weather and flooding, which are often suppressed across much of Europe. If true, one innovative approach for conserving HNV species would be to restore natural disturbance processes, as advocated by the "rewilding" conservation movement. I set out to explore the feasibility of this approach, focusing on flooding. Restoration of flood regimes is receiving growing attention, not only for its biodiversity benefits but also to reduce the risk of flooding in downstream urban areas, improve water quality, and increase the amenity value of rivers. I carried out four linked studies. Each followed a broadly similar approach: I selected sampling locations both in floodplain areas and comparable surrounding farmland, I surveyed birds and butterflies as indicator taxa of biodiversity, I carried out habitat mapping, and I estimated disturbance through both field measurements and remotely sensed data. My first study was around the Pripyat river in Ukraine, which has a large floodplain that has had minimal human intervention. I found that several, but not all, HNV species had higher population densities in the floodplain than in the surrounding HNV farmland, and several more had approximately equal population densities in the two habitats. This suggested intact flood regimes can retain some species that are elsewhere restricted to HNVf. My second study was around the river Rhône, France, where a restoration project has increased flow in floodplain channels and improved their connectivity with the main channel. I compared restored and non-restored segments of floodplain channel, as well as farmland and other habitats. While I found significant differences in population densitiesbetween habitat types, few species showed significant differences between restored and non-restored segments, suggesting that restoration had only limited ecological impacts on the wider landscape. My third study investigated a more ambitious restoration project which has reconnected a large area of floodplain to the river Peene in Germany. I found many HNV species had equal or higher population densities in the restored floodplain than in the surrounding unrestored farmland. This demonstrates that it is possible to restore the effect of natural flood disturbance on habitats and species. However, not all HNV species benefitted from flood-disturbed habitats, so clearly other conservation interventions need to be considered. For the final study, pooling data from all three sites I looked for associations between species' traits and environmental variables. My aim was to identify traits which predict species' responses to the environment, and hence which species are most likely to benefit from restoration. However, I did not find any significant associations in my data. In conclusion, I demonstrated that flood-disturbed habitats are suitable for many species traditionally associated with HNV farmland, and further that restoring flood disturbance processes can recreate those habitats. As such, reconnecting rivers and restoring floodplains would be a useful conservation intervention for species threatened by the abandonment or intensification of HNV farmland in Europe. However, other species did not benefit, and require other conservation interventions, perhaps other forms of rewilding, or continued incentivisation of favourable farming practices.

Islands have been characterized based on vegetation and topography as exhibiting different disturbance regimes - reinforcing or resisting. This study had two objectives: quantify barrier island upland migration and vegetation cover change over 32 years (1984-2016), and assess tolerance of two prevalent dune grass species, A. breviligulata, and S. patens to sand burial. Using Landsat imagery from the Virginia Coast Reserve, islands were categorized within the disturbance resistance/reinforcing framework based on dune elevation. Resistant areas were associated with woody cover and low marsh to upland migration while reinforcing areas had low vegetation cover and high rates of migration. System-wide, migration rates increased over time and large losses of upland and marsh, paired with expansions of woody cover occurred. In the field, each grass species was subject to repeated burials. S. patens was able to maintain biomass and height in high rates of burial, whereas A. breviligulata did not survive.

Floods are major disturbance events for riverine ecosystems, directly and indirectly impacting organisms and their habitat. In this study I investigated the role of riverine floods and flow alteration in regulating aquatic macroinvertebrate population and community structure. I examined this problem using a variety of methods: a meta-analytic review of primary studies from the literature, a mathematical model synthesizing population and flood ecology, a multi-year experimental flood program in an arid-land river, and a field investigation of flood recovery behaviors in a charismatic larval odonate. I found that floods significantly reduced invertebrate abundance in the short term, but had varied effects across particular study sites, microhabitats, and taxonomic groups. I determined that both resistant and resilient capabilities are important to persistence of invertebrate populations after disturbance events, and that these traits may act in a binary fashion. Recovery over time of invertebrate populations may be partially due to "hidden resistance" of spatially displaced individuals in side-channels, benthic substrate, and vegetation or wood. Some invertebrates adapted to flood-prone rivers may possess behavioral adaptations for returning to the main-channel of the river after flood events. This dissertation contributes to riverine disturbance ecology and provides information useful to prediction and management of ecosystem flows in rivers. / Graduation date: 2012

The recent increase in large fires in southwestern forests has prompted concern regarding their ecological consequences. Recognizing the importance of spatial patterns in influencing successional processes, I asked: (1) How do large fires change plant communities?; (2) What are the implications of these changes for ponderosa pine forests?; and (3) What is the relationship of fire severity to gradients of climate, fuels, and topography? To address the first two questions, I studied succession in the woody plant community at two sites that burned in high-severity fire: La Mesa fire in northern New Mexico (1977) and Saddle Mountain in northern Arizona (1960). After large fires, abiotic conditions, associated prefire plant distributions, and spatial patterns of burning interacted to result in particular successional outcomes. Variation in abundance and diversity of species that spread from a refuge of seed sources remaining after the fire followed the model of wave-form succession. I investigated the implications of large fires for ponderosa pine by examining the influence of spatial patterns of burning on regeneration. Tree density corresponded most closely with particular scales of seed dispersal kernel and neighborhood severity metrics. Spatial patterns of burning remained influential even after consideration of variables describing subsequent burning and the physical and biotic environment. Age structure of young forests indicated that populations spread in a moving front and by long-distance dispersal. To explore the relationship between fire severity and climate, I investigated how the spatial heterogeneity of high-severity patches varied among 20 fires across gradients in fire size and climate. The largest fires generally occurred during cool dry La Niña climates, however, several fires deviated from this trend. Some spatial properties of severity did not correspond to fire size or to changes in climate. Characteristics of fuels and topography altered spatial patterns of severity, but interactions with extreme burning conditions may have disrupted these local influences in both La Niña and El Niño fires. Spatial patterns of fire severity are central to understanding ecological dynamics following large fires in southwestern forests. Moreover, simplistic assumptions regarding the relation of fire severity to fire size and climate should be viewed with caution.

The hemlock-silverbell (Tsuga canadensis-Halesia tetraptera) forest type is known to exist in only two places, the Great Smoky Mountains National Park (GRSM) and the Joyce Kilmer National Memorial Forest. The hemlock component of this forest type is currently threatened by the hemlock woolly adelgid (Adelgis tsugae), an invasive aphid-like insect native to Japan. This current status has given rise to the need to investigate the ecological resources of this rare forest type before the hemlock component dies out. The objectives of this study were to determine the nature of the plant/environment and plant/plant associations within this forest type. Within this forest type hemlock was negatively related to protection, aspect, and slope steepness and silverbell was positively related to aspect and slope steepness. This study also identified some interspecific associations such as the negative relationship in the understory between hemlock and striped maple, and provided evidence that understory stems are exhibiting a growth response to hemlock decline in these stands. The information obtained from this study characterizing the plant/environment interactions and even the structural and species components of this forest type will serve as a baseline of data from which to measure change and will provide insight into the mechanisms of species distribution and perhaps into short term scenarios of forest response to hemlock decline and mortality.

As disturbance frequencies, intensities, and types have changed and continue to change in response to changing climate and land-use patterns, coastal communities undergo shifts in both species composition and dominant vegetation type. Over the past 100 years, fire suppression throughout the Northern Gulf of Mexico coast has resulted in shifts towards woody species dominance at the expense of marsh cover. Over the next 100 years, sea levels will rise and tropical storm activity is projected to increase; resultant changes in salinity could reduce cover of salt-intolerant fresh marsh species. Together, the effects of fire suppression upslope and rising salinities downslope could "squeeze" fresh marsh species, reducing cover and potentially threatening persistence. To mitigate the effects of fire suppression, the use of prescribed fire as a management tool to mimic historic conditions is becoming increasingly widespread and will likely gain further popularity during the 21st century. Ecological shifts that will result from changing disturbance regimes are unknown. It was hypothesized that two recent hurricanes, Ivan and Katrina in 2004 and 2005, respectively, and a prescribed fire, in 2010, differentially affected species along the estuarine gradient and drove overall shifts away from woody dominance. Overall community composition did not change significantly in the intermediate and fresh marsh zones. However, significant changes occurred in the salt and brackish marshes and in the woody-dominated fresh marsh-scrub ecotone zones. Relative to 2004, woody species abundance decreased significantly in all zones in 2006, following Hurricanes Ivan and Katrina, and 2012, following the hurricanes and fire, though woody species regeneration in the marsh-scrub ecotone had begun to occur by 2012. It is hypothesized that interacting changes in fire and tropical storm regimes could release upslope areas from coastal squeezing.

No description available.

The West Florida Shelf (WFS) is one of the largest and most diversely-used continental shelf/slope systems in the world. The presence of paleoshorelines and scarped hardbottom outcrops (up to 4 m in relief) along the inner shelf (10-30 m depth) provide important habitat for a variety of infaunal, epifaunal, and fish assemblages that contribute to the productivity of the region. This dissertation will present a comprehensive overview of the geological, physical, and chemical settings of the inner West Florida Shelf, with particular focus on biological and ecological community dynamics of epibenthic macroinvertebrates, algae, and fish assemblages. Baseline and comparative data sets are presented in the form of historic and modern species lists, with focus on seasonal and intra-annual variations. Quantitative effects of disturbances (e.g., hurricanes, thermal stresses, and red tides) and subsequent recovery rates are discussed as they periodically perturb inner-shelf systems and can have significant effects on community structure. Benefits of and recommendations for using artificial reefs as restoration tools along the inner shelf, as mitigation for future disturbances, are presented.

京都大学 / 新制・課程博士 / 博士(生命科学) / 甲第23332号 / 生博第450号 / 新制||生||60(附属図書館) / 京都大学大学院生命科学研究科統合生命科学専攻 / (主査)教授 片山 高嶺, 教授 永尾 雅哉, 教授 上村 匡 / 学位規則第4条第1項該当 / Doctor of Philosophy in Life Sciences / Kyoto University / DFAM

Human activities and expansion have created novel disturbance patterns across Earth’s landscapes. Disturbance is an ecological interruption after which ecosystem recovery or transition into a new state can occur, affecting biodiversity, ecosystem functioning, and theavailability of ecosystem services. Fire and herbivory are two of the most widespread forces of disturbance which shape ecosystems globally. In temperate forest ecosystems, fire affects forest composition, which influences the diversity and resilience of ecosystems (chapters 1 and 2) and forest canopy structure, which is important to snowpack accumulation and the availability of water resources (chapters 3 and 4). In chapter one, the effects of conifer competition, which occurs under fire suppression, and ungulate herbivory on aspen regeneration and recruitmentwere examined. It was found that conifer competition, and ungulate herbivory both drastically reduced successful aspen regeneration and recruitment and had a larger effect than climatic or topographical variables. In chapter two, this understanding was used to investigate mechanicaland fire interventions by the National Forest Service in a mixed aspen conifer forest experiencing fire suppression and heavy ungulate herbivory. Untreated forests failed to recruit aspen suckers successfully due to conifer competition and ungulate browsing. Fire treatments were successful in restoring aspen habitat, but mechanical treatments failed due to heavy ungulate use, despitethe treatment eliciting high sucker densities. In chapter three, fire severity was found to have important implications for snowpack accumulation and snow-water content in alpine forests. High burn severity, which is projected to become more common under future climaticconditions, led to deeper and denser snowpack possibly buffering the effects of water loss in a warmer climate. In chapter four, the interaction between topography and vegetation in burned forest conditions was evaluated. It was found that topographical aspect likely mediates the effect of vegetation on snowpack and may have an opposite effect on snow accumulation and melt on north vs south facing aspects. A synthesis of studies from different regions further supports the idea that this relationship between fire and snow is heavily dependent on latitude, elevation, and slope angle. Together, these findings demonstrate that the resilience and persistence of aspenforest ecosystems in changing disturbance regimes depend on complex interactions among disturbance type, disturbance severity, landscape position, and hydrology. These interactions should be integrated into management strategies to protect ecosystems and ensure ecosystemservices for growing human populations in the western United States.