Woody plant expansion has been documented for decades in many different ecosystems, often due to anthropogenic disturbances to the environment and yielding vast changes in ecosystem functioning. While causes and consequences of woody expansion have been well documented, few studies have investigated functional traits of woody species that promote rapid expansion in range. My objective was to determine if hydraulic efficiency confers enhanced photosynthetic efficiency so that functional traits representing light and water use may be possible mechanisms facilitating woody encroachment into grasslands and forest understories. I quantified leaf-level light environment, photosynthetic activity, and hydraulic characteristics of three sympatric broadleaf evergreens of varying leaf life span (Ilex opaca, Kalmia latifolia, and Myrica cerifera) in a deciduous forest understory to understand seasonal intra- and interspecific ranges of broadleaf evergreen physiology. Additionally, I investigated the effects of age on physiological efficiency of M. cerifera across a chronosequence (i.e., space for time substitution) of shrub thicket development in order to understand possible age-related physiological mechanisms facilitating shrub expansion. Lastly, I determined functional traits and resulting physiology that contribute to rapid expansion and thicket formation of an invasive, deciduous, N-fixing shrub, Elaeagnus umbellata, and a native, evergreen, N-fixing shrub M. cerifera. When compared to co-occurring evergreen species, electron transport rate (ETR) of M. cerifera was nearly double that of I. opaca or K. latifolia in summer. Photosynthetic capacity was positively related to hydraulic capacity among understory evergreens. Furthermore, photosynthetic and hydraulic efficiency of M. cerifera remained consistent despite considerable differences in thicket age and development. Both similar and contrasting functional traits of E. umbellata and M. cerifera allowed for enhanced light capture and water movement, and reductions in subcanopy light penetration. Enhanced hydraulic and photosynthetic efficiency relative to co-occurring species contributes to rapid range expansion and thicket formation by promoting enhanced productivity and limiting successful colonization of other species. My results indicate that there may be suites of functional traits linked to expansive success and thicket-formation, yet differences in functional traits between native and invasive species represent alternative strategies leading to rapid growth and thicketization.

Doctor of Philosophy / Department of Division of Biology / John Blair / The feasibility of restoration, which traditionally targets historical conditions, is questionable in the context of global change. To address this, my dissertation investigated (Chapter 2) the patterns of restoration establishment along a chronosequence of restored prairies with respect to nearby remnant prairies, (Chapters 3-4) responses of plant communities in restorations initiated using different methods (levels of species richness and sowing density) to drought, which is projected to increase in frequency, and (Chapters 5-6) the effects of propagule source and variation (mixing among sources) on restoration establishment and the generality of restoration outcomes across variable environments using reciprocal common gardens of multi-species restoration seedings. Chapter 2, published in Restoration Ecology, showed that restoration led to the recovery of desirable characteristics within several years, but restorations utilizing primarily fall-collected seeds likely diminished the representation of early phenology species, so biodiversity may be further enhanced by including early phenology species in seeding mixes. Chapters 3 and 4, published respectively in Ecological Applications and Applied Vegetation Science, examined the establishment of native plant communities after seeding and their responses to experimentally imposed drought. Both high seed mixture richness and high density seeding resulted in greater establishment of native, seeded species compared to low richness and low density treatments, and exotic species were less prevalent in high richness and high density treatments. However, we found little evidence of differential drought resistance, recovery, and resilience among treatments. This result coupled with increases in exotic species following drought suggest that other forms of active management may be needed to produce restored plant communities that are robust to climate change. Chapter 5 (published in Ecosphere) iii and Chapter 6 found that seed source affects individual species establishment, community structure, and productivity. However, there was no consistent advantage for any source, including local sources, across sites or species. This suggests that source effects on single species or effects observed at single locations should not be broadly generalized. Together, this dissertation shows that restoration can recover many characteristics of native prairies and that manipulation of seeding practices (seed mixture richness, seeding density, seed source) influence grassland establishment in terms of productivity, community structure, invasion, and the abundance and survival of individual species.

A mineração causa graves impactos ambientais, sendo o solo um dos componentes do meio físico mais vulnerável durante a exploração das jazidas. O ciclo do N tem sido bastante estudado, entretanto, pouco se sabe sobre a trajetória de recuperação da sua ciclagem em florestas restauradas após a mineração de bauxita. O objetivo foi investigar de que maneira o processo de restauração florestal em área minerada para extração de bauxita interfere na ciclagem do nitrogênio no sistema solo-planta-serapilheira. Para tanto, foram mensurados nesses compartimentos a disponibilidade de N, suas razões N:P e a abundância natural do isótopo estável de N (?15N). As hipóteses propostas foram: \"A restauração florestal, conduzida pelo uso de técnicas de engenharia ecológica, plantio de espécies arbóreas nativas e adição de topsoil é suficiente para aumentar a disponibilidade de N no ecossistema\", e \"Áreas mineradas em processo de restauração florestal, com o avanço da sucessão ecológica, podem desenvolver uma dinâmica na ciclagem de N próxima ao ecossistema de referência, apresentando valores de concentrações desse nutriente nos seus compartimentos (solo-planta-serapilheira) semelhantes a esse ecossistema\". O estudo foi conduzido no município de Poços de Caldas/MG, sendo considerados três tratamentos: floresta nativa, área restaurada há aproximadamente 06 anos e área restaurada há 24 anos, com seis repetições para cada. O delineamento utilizado foi o inteiramente casualizado, no esquema de parcelas subdivididas. O ciclo do N não foi recuperado nas florestas em restauração. Entretanto, há uma tendência de a ciclagem desse elemento assemelhar-se a da floresta nativa, conforme o avanço da sucessão ecológica. Deste modo, ambas as hipóteses propostas foram confirmadas, sendo a utilização de técnicas de engenharia ecológica, plantio adensado de espécies nativas e a adição de topsoil, os principais responsáveis pelos resultados / Mining causes serious environmental impacts and the soil is the most vulnerable component of the physical environment during the exploitation of deposits. The N cycle has been extensively studied, however, little is known about the recovery trend of its cycling in forests restored after bauxite mining. The aim was to investigate how the forest restoration process in bauxite mined area interferes in the nitrogen cycling in the soil-plant-litter system. Therefore, we measured the availability of N, the N:P ratios and the natural abundance of N stable isotope (?15N) in these compartments. The hypotheses proposed were: \"Forest restoration, driven by the use of ecological engineering techniques, planting of native tree species and addition of topsoil is sufficient to increase the availability of N in the ecosystem\", and \"Mined areas in forest restoration process, with the advancement of ecological succession, can develop a dynamics in N cycling resembling to that of the reference ecosystem, presenting values of concentrations of this nutrient in their compartments (soil-plant-litter) similar to this ecosystem. The study was conducted in Poços de Caldas county, Minas Gerais state, Brazil, considering three treatments: native forest, area restored for approximately 06 years and a restored area for 24 years with six repetitions for each. The design was completely randomized in a split plot. The N cycle has not been recovered in forest restoration. However, there is a tendency of N cycling resemble that of the native forest as the advancement of ecological succession. Thus, both hypotheses were confirmed, and the use of ecological engineering techniques, dense planting of native species and the addition of topsoil, were the main responsible for these results

Thesis (Ph.D. (Environmental Science)--North-West University, Potchefstroom Campus, 2007.

The rehabilitation of degraded soils, such as those associated with post-mining sites, requires knowledge of the soil ecosystem and its physical, chemical, and biological composition in order for rehabilitation efforts to fulfil the long-term goal of reconstructing a stable ecosystem for rehabilitated mine soil. This study addresses the need for appropriate assessment criteria to determine the progress of rehabilitation and subsequently the success of management practices. Significant contributions made by this investigation included the establishment of minimum and maximum values for microbial community measurements from two case studies of rehabilitated coal discard sites. Furthermore, it was shown that there was no relationship between changes in microbial community function and structure and the rehabilitation age of the sites. Following this, the considerable impact of management practices on microbial communities was illustrated. The first part of the study investigated the temporal changes in microbial community function and structure in a chronosequence of rehabilitated coal discard sites aged 1 to 11 years. The most important observation made during the investigation of the microbial communities in the different aged soil covers of the rehabilitated coal discard sites, was that there was no relationship between rehabilitation age and microbial activity or abundance of certain microbial groups. What was responsible for a clear differentiation between sites and a shift in microbial community attributes was the management practices applied. A comparison of two chronosequences of rehabilitated coal discard sites was achieved by an application of the 'space-for-time' hypothesis. Sites of different ages and at separate locations ('space') were identified to obtain a chronosequence of ages ('time'). The two chronosequences included sites aged 1 to 11 years (chronosequence A) and 6 to 17 years (chronosequence B), respectively. Sites in the same chronosequence were managed identically, while there was a distinct difference in management practices applied to each chronosequence. The long-term effect of the different management regimes on the soil microbial community function and structure was investigated. Again, there was no relationship between rehabilitation age and microbial community measurements. Fluctuations of selected microbial properties occurred in both chronosequences and similar temporal trends existed over the rehabilitation periods. However, the less intensively managed chronosequence (8) seemed more stable (less fluctuation occurred) over the rehabilitation period than the more intensively managed chronosequence (A). It was therefore concluded that the microbial communities in the less managed sites maintained their functional and structural integrity within bounds in the absence of management inputs or disturbance. While there was similarity in the trends over time for individual microbial community measurements, the seemingly more stable conditions in chronosequence 6 are important in terms of the goal of rehabilitation. / Thesis (Ph.D. (Environmental Science)--North-West University, Potchefstroom Campus, 2007

The tallgrass prairie has been severely reduced in size, making restoration important to maintain communities and functions of this ecosystem. A chronosequence approach was used to determine recovery of physical and biological soil properties. The recovery models of soil properties provided information to explain the variation in total C stock of the whole soil. Recovery models also provided information to design a competition experiment based on variation in whole soil conditions with land use history. The filter framework hypothesis is a useful concept for examining tallgrass prairie restoration; the theory states only a subset of species in the region will be able to establish in a specific location due to abiotic and biotic filters. With this theory in mind, I explored the influence of whole soil conditions as affected by land use history (cultivation/restoration) and how these conditions altered plant-plant competition dynamics of a dominant grass was studied. Belowground plant biomass recovers with cessation of tillage and restoration back to prairie, providing an organic matter source for microbial populations to recover and soil macroaggregates to form. This has potential to increase C sequestration in soils and decrease nitrous oxide efflux from soils. Intact 5.5 cm dia cores were collected to a depth of 10 cm in each field to determine physical and biological soil properties. Belowground plant, microbial community, and soil structure properties were modeled to recover coinciding with an increase in total C stock of the whole soil. Structural equation modeling revealed that soil structure physically protecting organic matter explained the most variation in soil carbon sequestration with restoration. Most of the total C was contained within the macroaggregate size fraction; within this fraction most of that C is within the microaggregates within macroaggregates fraction. Soil structure is critical for recovery of soil carbon stocks and the microaggregate within macroaggregate fraction is the best diagnostic of sequestered C. ANCOVA results indicate that while the slopes of nitrous oxide efflux rates did not differ, cumulative efflux differed, though this was not related to time since restoration. Dominant grasses, such as Andropogon gerardii, can exclude subordinate species from grassland restorations. Thus, understanding changes in competition dynamics of dominant grasses could help maintain richness in grassland restorations. There may be changes in competition dynamics with whole soil conditions affected by land use history (cultivation/restoration) as plant available nutrients will decrease, microbial populations will increase, and soil structure will improve with restoration from cultivation to prairie. Using 4 soil treatments of varying land use history with four species treatments, to determine if effects are general or species specific, pairwise substitution competition experiments were conducted. Relative A. gerardii response to competition was compared among soil and species treatments using competition intensity and competition importance indices utilizing final plant biomass, relative growth rate based on maximum height, and net absolute tiller appearance rate. The experiment was conducted over 18 weeks, allowing A. gerardii to flower. A significant intensity result and significant importance results utilizing biomass measurements indicated that the 16 year restored prairie soil cause A. gerardii to be a relatively better competitor against forbs than in all other soils except for cultivated soil, likely due to positive plant-soil feedbacks. Significant importance results utilizing tiller appearance rate indicated that the cultivated and 3 year restored prairie soil caused A. gerardii to be a relatively better competitor than in the 16 year restored and never cultivated native prairie soils, likely due to changes in whole soil conditions related to land use history. There were only general soil effects, as soil treatments did not interact with species treatments. A. gerardii was a relatively better competitor against non-leguminous forbs, indicating that legumes are a better competitor for a limiting nutrient than A. gerardii or that this species is not in direct competition with legumes.

The prairie communities that once dominated the landscape of Illinois have been reduced to a fraction of their former extent. Subsequently, considerable effort has been invested in the restoration of these lost communities, yet the comprehensive assessment of restoration success has only recently garnered interest. The objectives of this study were 1) to gauge the success of a prairie restoration project by measuring the components of ecological fidelity (structure/composition, function, and durability), and 2) to determine the factors that influenced success. Nineteen prairie plantings (ranging from two to 19 growing seasons old) at The Nature Conservancy's Nachusa Grasslands preserve were chosen for the assessment. Floristic quality was calculated to assess the composition component of ecological fidelity. Aboveground net primary productivity, soil bulk density, total soil nitrogen and total soil carbon were measured to assess the function component (soil measurements were taken at 0-5 and 5-15 cm depths). Results were compared to benchmark values taken from the literature and from samples of remnant prairies. Durability was determined by comparing measurements across a restoration chronosequence. To further evaluate the prairie plantings and restoration success, non-metric multidimensional scaling ordination was used to compare plantings based on their vegetation composition and soil characteristics (prairie remnants were also included in the comparison based on soil characteristics). Values of Mean C and FQI indicated successful levels among younger plantings, but durability was less successful according to the chronosequence. Seed-mix quality had the greatest influence (positive) on composition success. Aboveground net primary productivity levels were successful and durable overall, however, younger plantings exhibited successful levels of production more consistently than older plantings. Aboveground net primary productivity was most influenced (negatively) by the abundance of the exotic C3 grass genera Poa and Bromus. Functional success based on soil characteristics was limited. Soil bulk density, total nitrogen, and total carbon levels all differed among plantings and remnants at both depths, and evidence of levels recovering toward levels of remnants was not detected. The results of this study indicated that some components of ecological fidelity have been successfully restored, while others have not, and using a high-quality seed mix that resembles the species pool of remnant prairie and limiting the abundance of the dominant native C4 and exotic C3 grasses can improve the restoration of plant composition and ecological function in Illinois prairie plantings. The mixed results underscore the importance of examining more than one component of ecological fidelity when measuring success. Long-term monitoring is also recommended for evaluating restoration durability, especially for detecting changes among soil properties over time.

A mineração causa graves impactos ambientais, sendo o solo um dos componentes do meio físico mais vulnerável durante a exploração das jazidas. O ciclo do N tem sido bastante estudado, entretanto, pouco se sabe sobre a trajetória de recuperação da sua ciclagem em florestas restauradas após a mineração de bauxita. O objetivo foi investigar de que maneira o processo de restauração florestal em área minerada para extração de bauxita interfere na ciclagem do nitrogênio no sistema solo-planta-serapilheira. Para tanto, foram mensurados nesses compartimentos a disponibilidade de N, suas razões N:P e a abundância natural do isótopo estável de N (?15N). As hipóteses propostas foram: \"A restauração florestal, conduzida pelo uso de técnicas de engenharia ecológica, plantio de espécies arbóreas nativas e adição de topsoil é suficiente para aumentar a disponibilidade de N no ecossistema\", e \"Áreas mineradas em processo de restauração florestal, com o avanço da sucessão ecológica, podem desenvolver uma dinâmica na ciclagem de N próxima ao ecossistema de referência, apresentando valores de concentrações desse nutriente nos seus compartimentos (solo-planta-serapilheira) semelhantes a esse ecossistema\". O estudo foi conduzido no município de Poços de Caldas/MG, sendo considerados três tratamentos: floresta nativa, área restaurada há aproximadamente 06 anos e área restaurada há 24 anos, com seis repetições para cada. O delineamento utilizado foi o inteiramente casualizado, no esquema de parcelas subdivididas. O ciclo do N não foi recuperado nas florestas em restauração. Entretanto, há uma tendência de a ciclagem desse elemento assemelhar-se a da floresta nativa, conforme o avanço da sucessão ecológica. Deste modo, ambas as hipóteses propostas foram confirmadas, sendo a utilização de técnicas de engenharia ecológica, plantio adensado de espécies nativas e a adição de topsoil, os principais responsáveis pelos resultados / Mining causes serious environmental impacts and the soil is the most vulnerable component of the physical environment during the exploitation of deposits. The N cycle has been extensively studied, however, little is known about the recovery trend of its cycling in forests restored after bauxite mining. The aim was to investigate how the forest restoration process in bauxite mined area interferes in the nitrogen cycling in the soil-plant-litter system. Therefore, we measured the availability of N, the N:P ratios and the natural abundance of N stable isotope (?15N) in these compartments. The hypotheses proposed were: \"Forest restoration, driven by the use of ecological engineering techniques, planting of native tree species and addition of topsoil is sufficient to increase the availability of N in the ecosystem\", and \"Mined areas in forest restoration process, with the advancement of ecological succession, can develop a dynamics in N cycling resembling to that of the reference ecosystem, presenting values of concentrations of this nutrient in their compartments (soil-plant-litter) similar to this ecosystem. The study was conducted in Poços de Caldas county, Minas Gerais state, Brazil, considering three treatments: native forest, area restored for approximately 06 years and a restored area for 24 years with six repetitions for each. The design was completely randomized in a split plot. The N cycle has not been recovered in forest restoration. However, there is a tendency of N cycling resemble that of the native forest as the advancement of ecological succession. Thus, both hypotheses were confirmed, and the use of ecological engineering techniques, dense planting of native species and the addition of topsoil, were the main responsible for these results

京都大学 / 0048 / 新制・課程博士 / 博士(地域研究) / 甲第19833号 / 地博第189号 / 新制||地||66(附属図書館) / 32869 / 京都大学大学院アジア・アフリカ地域研究研究科東南アジア地域研究専攻 / (主査)教授 竹田 晋也, 教授 岩田 明久, 准教授 古澤 拓郎, 教授 神﨑 護 / 学位規則第4条第1項該当 / Doctor of Area Studies / Kyoto University / DGAM

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