The concept of the ecotone was formalised by Clements (1 905) as a boundary zone between plant communities. Little research exists on the ecological importance or the geographical variability of these zones. Two types of boundaries are acknowledged: the ecotone and the ecocline. The ecotone is a sharp boundary; the ecocline a gradual boundary. The term 'transitional area' is proposed here to more accurately describe these areas as this research demonstrates that a complex continuum exists between the two end points. Additionally, mosaics often complicate the nature of the transition and may form a boundary type in their own right. Upland plant communities represent important semi-natural habitats within the British Isles. Effective management depends on an understanding of their structure and function. This research is primarily concerned with the description of structure (spatial pattern and variability in floristic composition) but explanation of these patterns is only possible through an understanding of function (vegetation dynamics). Pilot studies determined an appropriate methodology for studying transitional areas. The approach progressed from a linear transect to a two-dimensional rectangular transect. The pilot studies also evaluated a range of methods for data analysis. Extended field sampling followed which included 23 sites in 4 locations: Dartmoor, Snowdonia, North York Moors and Barra, Western Isles of Scotland. Data analysis exposed the complexities of the transitional areas sampled but 'noise' often obscured the true characteristics. To overcome this a Species Ratio Index Model was devised to identify the strength of signal for each boundary. The final characterisation of transitional areas is based on three main components: ecotone, ecocline and mosaics, each displaying varying amplitude. Of the sites sampled, few boundaries revealed single characteristics and the majority were far more complex than their observed patterns implied. On the basis of this characterisation a classification is proposed which incorporates both natural and anthropogenic factors. The classification represents an important contribution to the understanding of boundary types. This study reinforces the significance of boundaries in the landscape. The potential for future research is great, particularly through the development of a predictive model for management purposes.

Pulse subsidies account for a substantial proportion of resource availability in many systems, having persistent and cascading effects on consumer population dynamics, and the routing of energy within and across ecosystem boundaries. Although the importance of resource pulses is well-established, consumer responses and the extent of resource partitioning is not well understood. I identified a pulse of marsh cyprinodontoid, invertebrate, and sunfish prey, entering an estuary, which was met by an influx of both marsh and estuarine predators. In response to the pulse, consumers showed marked diet segregation. Bass consumed significantly more cyprinodontoids, bowfin consumed significantly more invertebrates, and snook almost exclusively targeted sunfishes. The diversity of the resource pulse subsidizes multiple consumers, routing pulsed production through various trophic pathways and across ecosystem boundaries. Preserving complex trophic linkages like those of the Everglades ecotone may be important to maintaining ecosystem function and the provisioning of services, such as recreational fisheries.

Forest encroachment has been documented across North America, from British Columbia to New Mexico, and is a growing concern due to loss of essential grassland habitat. Climate change, fire suppression, changes in grazing regimes, and differences in microclimate between topographic gradients are the main factors associated with forest encroachment into grasslands. Small-scale factors, such as competition and facilitation also play an important role in forest-grassland dynamics. I examined forest-grassland dynamics in southwest Yukon through dendroecological techniques and repeat image analysis. Dendroecological techniques were used to identify periods of tree encroachment, changes in age structure, pulses of tree establishment and possible correlations with climatic variables. Dendroecological results indicated that over the last 60-80 years, trees have invaded an average of 30 meters into grasslands on south-facing slopes and flat terrain in southwest Yukon. Ecotones on north-facing slopes appear stable with little advance into grasslands over the last 60 years. Results indicate forest encroachment varies across topography and between tree species. Repeat image analysis was also used to examine landscape changes over a 60-year time period near Kluane Lake. Forest encroachment was investigated using landscape metrics which characterized changes in grassland configuration across three time periods (1947, 1979, 2007) in a 10km2 area. Total grassland area decreased from 214.4 hectares in 1947 to 137 hectares in 2007 and coincided with extensive grassland fragmentation. One hundred and seventy grassland patches were identified in 1947 which increased to 270 patches in 2007. Although tree invasion was found across all topographic gradients, results complement dendroecological analyses with flat terrain and south-facing slopes experiencing the greatest loss of grassland. It is possible that the increase in trembling aspen (Populus tremuloides) on south-facing slopes and flat terrain is due to warmer temperatures in the area. Aspen establishment coincided with warmer temperatures however further work is needed to identify the influence of changes in fire and grazing regimes. Although southwest Yukon grasslands are limited in distribution they are ecologically significant and provide habitat for unique assemblages of flora and fauna. / Thesis (Master, Geography) -- Queen's University, 2012-09-18 01:03:21.524

Alpine treeline ecotones (ATE) are the transition zones between contiguous subalpine forest and open alpine tundra. Because of their transitional natures formed by different ecosystems in high mountain areas, there are a variety of acute interactions between different species, between vegetations and environmental factors, and between ecological pattern and process. These interactions, or feedbacks, are often nonlinear in nature and make alpine treeline ecotones sensitive to environmental change, especially climate change. Feedbacks or nonlinear interactions between pattern and process create a variety of distinctive yet sometime surprising alpine treeline patterns. These nonlinear interactions between pattern and process and their resultant various patterns are defined as spatial complexity. In this study, the research framework of complexity theory was adopted. Dynamical simulations of alpine treeline ecotone is used as basic research method, and local nonlinear interactions, or more specifically, positive feedbacks are considered the key mechanism driving alpine treeline dynamics. A cellular simulation was created with tree/no-tree states that change as a function of probabilities of tree establishment and mortality which are functions of the neighborhood and an underlying gradient; the former changes in space and time endogenously; the latter can change in space and time exogenously. Three research projects were conducted for this dissertation that explore the endogenous and exogenous aspects of alpine treeline dynamics. First, the endogenous dynamics of alpine treeline ecotones was examined, which indicates that local positive feedbacks originated from interactions between trees can create fractal spatial dynamics in space and time. Second, the impacts of geomorphologic factors that impose an exogenous spatial structure on alpine treeline dynamics, was examined, which shows that there is a geomorphic limit to the endogenous fractal alpine treeline dynamics. Third, the impacts of climate change that imposes an exogenous temporal structure on alpine treeline dynamics was examined, which suggests that the self-organization nature of alpine treeline dynamics will not be significantly affected by external climate change and the use of alpine treeline ecotones as potential indicator of climate change is called into question. Results of this study suggest further research using complexity theory is needed to improve our understanding of alpine treeline dynamics and their interactions with exogenous environmental factors.

Doctor of Philosophy / Department of Geography / Richard A. Marston / David R. Seamon / Sprawling over 180 square miles of California’s Mojave Desert, Wonder Valley was founded in the early 1950s and today is an unincorporated community of approximately 1,000 residents. The community’s landscape is expansive and unsettling, featuring a chaotic assortment of residences that include abandoned homesteads, squatter settlements, artists’ studios, middle-class cabins, and luxury vacation properties. This dissertation explores Wonder Valley’s enigmatic place identity from residents’ point of view, drawing on an experiential understanding of place grounded in humanistic and phenomenological geography. Specifically, the dissertation makes use of Edward Relph’s explication of place identity to guide empirical inquiry and conceptual structure. Drawing on resident interviews, place observations, and textual analysis, the dissertation identifies and explicates three distinct Wonder Valley identities—homesteaders, dystopics, and utopics. Arriving in the 1950s, homesteaders were Wonder Valley’s first inhabitants and express a practical connection to the landscape that is interpreted in terms of environmental reach, specifically, the creation, maintenance, and extension of environmental and place order. During the 1970s, as many homesteaders abandoned Wonder Valley, dystopics arrived and today include two subgroups: first, a criminal element pulled to Wonder Valley because of its local isolation but regional proximity to Los Angeles; and, second, destitute squatters pushed out from other communities and having nowhere else to go. The third group identified is utopics, primarily artists from Los Angeles and San Francisco, who arrived in the early 1990s, attracted by Wonder Valley’s natural beauty and sacred ambience. The dissertation explores how these three groups arrived at different times, for different reasons, to create vastly different landscapes, to engage in opposing aims and activities, and to understand Wonder Valley’s meaning as a place in greatly contrasting ways. These differences in meaning are most directly expressed in the common areas of public land, which have often become sites of inter-group tension and conflict, particularly in regard to abandoned homesteads and the use of off-road vehicles. To interpret this group conflict conceptually, the dissertation develops what is termed existential ecotone— a unique mode of place experience generated by overlapping but contrasting modes of being-in-place.

A histoplamose é uma micose sistêmica que pode se apresentar desde uma infecção assintomática até a forma disseminada, potencialmente fatal. Causada pelo fungo dimórfico Histoplasma capsulatum, é tratada de forma transdisciplinar, sua epidemiologia se alicerça em quatro pilares: biológico, social, econômico e cultural. Essa abordagem permite compreender o complexo sistema de irradiação da doença nos mais diversos ambientes, sendo mais comum em países tropicais e subtropicais. O Centro de Pesquisa Canguçu (CPC) localiza-se no estado do Tocantins, no município de Pium em uma região de transição dos biomas Cerrado/Amazônia. O presente trabalho objetivou analisar a participação dos morcegos frugívoros no processo epidemiológico de disseminação do fungo Histoplasma capsulatum no Centro de Pesquisa Canguçu, utilizando técnicas de captura com redes de neblina “mist nets” e coleta de material biológico do tipo guano seco e fresco e o cultivo em laboratório das amostras em Ágar Sabouraud a fim de se determinar a presença do agente etiológicoe as condições ambientais envolvidas na sua disseminação e infecção. Outro ponto relevante como foco do estudo foi o perfil climático da região e sua relação com as amostras das culturas obtidas em laboratório. Na área do Centro foi verificada a presença de esporos do fungo, assim também como no sistema gastrointestinal dos morcegos da espécie Carollia perspicillata, sendo positivada quinze por cento das culturas das amostras do guano seco e fresco, demonstrando a necessidade de cuidado redobrado com os frequentadores do Centro, em especial às pessoas imunocomprometidas. / Histoplasmosis is a systemic mycosis that can range from an asymptomatic infection to the disseminated, potentially fatal form. Caused by the dimorphic fungus Histoplasma capsulatum, it is treated in a transdisciplinary way, its epidemiology is based on four pillars: biological, social, economic and cultural. This approach allows to understand the complex system of irradiation of the disease in the most diverse environments, being more common in tropical and subtropical countries. The Canguçu Research Center (CPC) is located in the state of Tocantins, in the municipality of Pium in a transition region of the Cerrado / Amazon biomes. The objective of this work was to analyze the participation of frugivore bats in the epidemiological process of dissemination of the fungus Histoplasma capsulatum at the Canguçu Research Center, using mist nets and collection of dry and fresh guano type biological material. laboratory culture of the samples in Sabouraud Agar in order to determine the presence of the etiologic agent and the environmental conditions involved in its dissemination and infection. Another relevant point as the focus of the study was the climatic profile of the region and its relation with the samples of the cultures obtained in the laboratory. In the area of the Center, the presence of spores of the fungus was verified, as well as in the gastrointestinal system of the bats of the Carollia perspicillata species. Fifteen percent of the cultures of the dry and fresh guano samples were positivized, demonstrating the need for redoubled care with regulars of the Center, in particular to immunocompromised persons.

Salt marshes are some of the most productive and valuable landscapes on earth, but they are vulnerable to the effects of sea-level rise, erosion and eutrophication. These processes act on a wide range of temporal and spatial scales, which complicate assessments of the health and stability of marsh ecosystems. High-frequency monitoring using in situ sensors captures the complete range of these dynamics, but extracting meaningful physical and ecological information from these signals requires process-based models coupled with statistical techniques. I develop and apply such methods to study two coastal landscapes, a coastal pine forest on the Eastern Shore of Virginia and a mesotidal salt marsh complex in the Plum Island Estuary, Massachusetts. Observations from groundwater wells in the Virginia pine forest indicate that storms are the dominant controls on the hydrology of the forest and that tidal influence is nonexistent. This forest exhibits a distinct spatial pattern in age structure in which young trees do not grow at low elevations. This pattern can be explained by a model that includes the interaction of sea-level rise, storms and the age-dependent variation in tree stress response, which predicts that the long-term evolution of the boundary is an ecological ratchet. Stresses due to sea-level rise slowly push the boundary at which young trees can survive upslope. Powerful storms then kill the mature, persistent forest at low elevations, which quickly pushes the forest boundary up to the regeneration boundary. Salt marshes need to accumulate sediment to replenish material lost as sea-level rises and creek banks erode. Fluxes of sediment can be monitored with simultaneous high-frequency observations of flow from acoustic Doppler current profilers and turbidity from optical backscattering sensors. I first investigate the relationship between water level and flow in marsh channels and develop predictive stage-discharge models to simplify the monitoring of fluxes. I then construct sediment budgets for eleven salt marshes in the Plum Island Estuary. The observed budgets depend strongly on the unique hydrodynamic conditions of each marsh channel. Variability in these conditions leads to the observed spatial and temporal variability in sediment fluxes from these marshes.

One of the important contributions genetic studies have made to conservation is the ability to resolve taxonomy and define relationships among populations. However, this can be complicated when species exhibit hybridization. Hybridization can be an important part of the evolutionary process and a critical component in a species ability to adapt to a changing environment. Most hybrid zones are observed at ecotones between two distinct habitats and this may be important in defining the role of hybrid zones in the evolutionary process. I examined hybridization among the three distinct lineages of desert tortoises in the genus Gopherus. An important aspect of this study system is the presence of areas of overlap between divergent lineages of desert tortoise which allowed me to test hypotheses about which forces influence these taxonomic boundaries. Specifically, I tested hypotheses about the contribution of physical vs. ecological segregation and the relative importance of isolation and gene flow in the formation of these disparate desert tortoise lineages. I used mtDNA sequence data and 25 microsatellite loci to perform Bayesian clustering, clinal analyses and habitat suitability modeling to infer population structure and influence of landscape features at each contact zone. In both instances, I observed ecological niche partitioning and limited hybridization at ecotones. I then used mtDNA and four nDNA loci to perform a multi-locus phylogenetic analysis to estimate the species tree among desert tortoise lineages and tested for ancestral admixture with RNA-seq data using demographic inference employed in the software package ∂a∂i. My results validate taxonomic distinction among all three lineages without evidence of ancestral introgression. These data suggest that despite the presence of contemporary hybridization and incomplete reproductive isolation, divergence among these lineages is consistent with species-level differentiation. By clarifying the evolutionary processes that influence the distribution of desert tortoise lineages, this study will directly inform efforts to preserve the evolutionary potential of these threatened species. Ultimately, understanding the evolutionary history of desert tortoises not only clarifies the forces that have driven speciation in this group, but it also contributes to our knowledge of the biogeographic history of the southwestern deserts and how diversity is maintained within them.

The wet zone – the lagg – that tends to form at the edge of ombrotrophic peatlands is believed to play an important role in promoting and maintaining the health of bog systems. The lagg is well-recognized by peatland scientists, yet empirical knowledge is surprisingly limited, and most of the characteristics associated with this ecotone come from qualitative observations. Understanding the role played by the lagg, and the potential impact its disturbance might have on the integrity of a raised bog system, is valuable for sustainable land management and peatland restoration science alike. This thesis explores and documents the basic ecohydrological characteristics of the lagg in the context of the neighbouring natural landscapes, and discusses the spatial properties of various types of laggs by exploring airborne LiDAR datasets to detect and position the ecotone. The specific objectives are 1) to describe the form and abiotic controls of the laggs and margins of bog peatlands, 2) to propose a conceptual model in cross-section of the “bog-lagg-mineral land” transition, 3) to explore the potential of data derived from aerial LiDAR (Light Detection And Ranging) to detect and locate laggs and lagg boundaries, and 4) to consider the spatial distribution of laggs around raised bog peatlands. Data were collected along 10 transects located within 6 relatively undisturbed bogs of the New Brunswick eastern lowlands, Canada. Each transect consisted of 4-6 wells, straddling the ombrotrophic bog and the adjacent mineral land, and of 3 nested piezometers in the center of each lagg. These instruments were used to monitor the position of the water table, to measure hydraulic gradient, hydraulic conductivity, and for water sampling. Dissimilarity analysis (edge-detection, split moving window) and similarity analysis (cluster, k-means) were used to test the delineation capacity of five variables derived from the LiDAR dataset; ground elevation (topography), vegetation height, topographic wetness index, and spatial frequency of both vegetation and ground LiDAR returns. The major abiotic control of the lagg appears to be topography. Two geomorphological categories were identified; confined and unconfined. The importance of topography is through the affect it has on water flow rates and direction, which in turn affect water chemistry, and most likely nutrient transport and availability, hence vegetation characteristics. Dissimilarity analysis of the five variables derived from LiDAR data revealed that some indicators were better at predicting the bog-lagg boundary (e.g. vegetation height), and others at finding the lagg-mineral land boundary (e.g. topography). In contrast, the similarity analysis gave more decisive influence to the topographic wetness index. When the lagg was confined between the bog and the adjacent upland, it took a linear form, parallel to the peatland’s edge. However, when the adjacent mineral land was flat or even sloping away, the lagg spatial distribution was discontinuous and intermittent around the bog. Our results confirms that laggs can take many forms, while suggesting two broad geomorphological categories from which they can more easily be studied and understood and highlight the potential offered by LiDAR technology in predicting their likely location around a raised bog. The results and conclusion from this research further our understanding of the goals to be achieved for ecological restoration, and favor sustainable management inclusive of the margins or bog peatlands.

4 Abstract The purpose of the diploma thesis is the analysis of changes in the alpine treeline ecotone with focus on the age structure and cover of the Norway spruce (Picea Abies) in the Giant Mountains in the 20th century. The altitudinal position and the tree density of the alpine treeline ecotone is a sensitive indicator which reflects the human impact as well as the climatic and air pollution changes. Methodical approach included the measuring of the age structure of the Norway spruce by using dendrochronology. In addition the changes of the spruce cover were evaluated from a series of aerial photographs dated 1936, (1953) 1964, 1985 and 2002. Those photographs were orthorectified and classified. The age distribution in the majority of the sample locations is irregular with some prominent peaks that are corresponding to the periods of good conditions and dips pointing out to the periods of disturbances. There is an evident peak during the 30s and 40s which is the same period of the increase of average temperatures of the growing season. On the contrary, depression during the 70s and 80s is detected only in the case of closed-canopy forest. The increasing number of trees during the 90s is related to the decreasing air pollution and to the higher average temperature. Relatively young age structure of the...