Calcium stable isotope ratios are a relatively new tool that biogeochemists can use to investigate the biogeochemical cycle of calcium in terrestrial ecosystems, having seen widespread application only in the past 15 years. To advance the application of calcium isotopes in biogeoscience research, I conducted three investigations focused on interpreting calcium isotope ratios in streamwater and in the cation exchange pool of forest soils. In the first study, we observe a shift toward lower 44Ca/40Ca ratios in streamwater draining a New Hampshire watershed after an experimental clearcutting event. Isotope ratio measurements of ecosystem calcium pools indicate that enhanced leaching of the soil exchangeable pool produced the observed shift in 44Ca/40Ca ratios. A trend towards decreased 44Ca/40Ca ratios in soils in the years following the harvesting indicates that calcium leached from the soil exchangeable reservoir was likely replaced by calcium released by the decay of belowground biomass, maintaining pre-harvest levels of exchangeable calcium even in the face of a significant ecosystem disturbance. In a second study, we observed significant differences in the 44Ca/40Ca of the soil exchange pool between two neighboring tropical watersheds, although 44Ca/40Ca of calcium inputs (bedrock and atmospheric deposition) at the two sites were indistinguishable. Further, both sites had higher 44Ca/40Ca ratios compared with external inputs, a relatively rare observation globally. We propose that hurricane disturbance best explains the high 44Ca/40Ca at each site, and that the difference in 44Ca/40Ca between the two sites can be accounted for by the magnitude of disturbance at each site. Finally, a synthesis of our new data with previously published results shows that globally, soil exchangeable 44Ca/40Ca ratios can be higher, lower or equal to external inputs. Modeling work indicates that in addition to isotopic fractionation, the balance in fluxes between vegetation and soil is critical in determining how soil exchangeable 44Ca/40Ca ratios vary relative to external inputs. When plant uptake and return to the soil are equal, soil and external inputs 44Ca/40Ca are equal, while high soil 44Ca/40Ca ratios develop when uptake exceeds return. Soil develops low 44Ca/40Ca when biomass obtains calcium from sources other than the exchangeable reservoir.

Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2016-03-31T15:55:37Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertação Edivaldo Lima PPGBA_2015.pdf: 1216837 bytes, checksum: a0087d1ed1223b4689da6194020ad828 (MD5) / Made available in DSpace on 2016-03-31T15:55:37Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertação Edivaldo Lima PPGBA_2015.pdf: 1216837 bytes, checksum: a0087d1ed1223b4689da6194020ad828 (MD5) Previous issue date: 2014-08-28 / FACEPE / O pisoteio decorrente do tráfego de pedestres sobre os recifes de coral é um fenômeno associado ao turismo em muitas praias de Pernambuco. No ambiente fital o pisoteio pode afetar as algas e a fauna associada, modificando a estrutura das comunidades. O filo Tardigrada é componente permanente da meiofauna sendo encontrado no sedimento marinho e associado a macroalgas. O presente trabalho teve como objetivo avaliar o efeito do pisoteio sobre os tardígrados associados ao fital dos recifes de Porto de Galinhas, PE. Para isso delineou-se experimentos observacionais e manipulativos com intuito de avaliar o impacto do turismo e das simulações de pisoteio humano sobre a comunidade de Tardigrada. No primeiro experimento foram determinadas estações pareadas ao longo dos recifes, seguindo os limites entre a área protegida e a exposta ao trafego humano, avaliando se a comunidade diferia em consequência do pisoteio. Os tardígrados apresentaram abundâncias aparentemente condicionadas pelo tipo de substrato, mostrando reduções na densidade quando associados a Gelidiela acerosa, e exibindo maior densidade na área impactada quando associados Chodrophicus papillosus. Para o segundo experimento foram determinados transects na área protegida do recife e executados dois níveis de intensidade de pisoteio sobre o substrato recifal. A avaliação do efeito do pisoteio seguiu um desenho experimental BACI (Antes/Depois e Controle/Impacto), sendo as amostras coletadas para monitoramento do nível de recuperação da comunidade com um, dois e três meses após cessado o pisoteio. Como resultado deste trabalho, houve redução das variáveis do substrato algal (biomassa, cobertura, peso do substrato e altura do tapete) e também na densidade de Tardigrada, com valores seguindo uma tendência de redução tanto maior o nível de estresse. Variações locais, foram determinantes para a estrutura da comunidade de Tardigrada, dificultando a compreensão dos efeitos do impacto. O processo de recuperação foi independente da intensidade do distúrbio, alcançando valores estabilizados já no primeiro mês. / The trampling resulting from pedestrian traffic on coral reefs is a phenomenon associated with tourism in many beaches of Pernambuco. In phytal environment the trampling can affect the algae and associated fauna, modifying the structure of communities. The phylum Tardigrada is permanent component of the meiofauna being found in marine sediment and associated with macroalgae. This study aimed to evaluate the effect of trampling on tardigrades associated with the phytal of reefs of Porto de Galinhas, PE. For this were outlined observational and manipulative experiments in order to assess the impact of tourism and simulations of human trampling on the community of tardigrades. In the first experiment were paired certain stations along the reefs, following the boundaries of the protected area and exposed to human traffic, assessing whether the community differed as a result of trampling. The tardigrades presented abundances apparently conditioned by the type of substrate, showing reductions in density when associated with a Gelidiela acerosa, and exhibiting higher density in the impacted area when associated Chodrophicus papillosus. For the second experiment were determined transects in protected reef area and run two levels of intensity of trampling on reef substrate. The evaluation of the effect of trampling followed a experimental design BACI (Before / After and Control / Impact), being the samples collected for monitoring of the level of recovery of the community with one, two and three months after trampling ceased. As a result of this work, there was a reduction of the algal substrate variables (biomass, cover, substrate weight and turf height) and also the density of tardigrades, with values following a trend of greater reduction in both the level of stress. Local variations were crucial to the structure of the tardigrades community, making the understanding of the effects of the impact difficult. The recovery process was independent of the intensity of the disturbance, reaching values stabilized in the first month.

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This dissertation describes research investigating the potential for using Landsat data to identify and characterize woody canopy cover on reclaimed coal-mined lands through three separate studies. The objective of the first study was to assess whether surface coal mines in the forested central Appalachian regions of the US can be separated from the other prevalent forest-replacing disturbances through analysis of an interannual chronosequence of Landsat images. Disturbances were classified using descriptors of the disturbance/recovery trajectories: disturbance minimum, recovery slope and recovery maximum. Three vegetation indices (VIs) (normalized difference vegetation index, NDVI; tasseled cap greenness/brightness ratio, TC G/B; and inverse of Landsat band 3, B3I) were used to analyze multitemporal trajectories generated using both pixels and objects. Classification accuracies using objects were better than those obtained using pixels for all VIs. The highest object-based classification accuracy was achieved using TC G/B (89%), followed by NDVI (88%) and B3I (80%). The objective of the second study was to evaluate performance of a woody canopy cover (including both native and invasive species) estimation method based on the 2011 National Land Cover Database (NLCD) protocol for both mined and non-mined areas of the central Appalachians. Potential explanatory variables included raw and derived bands from leaf-on and leaf-off Landsat scenes plus terrain descriptors. Results show that the model developed to estimate canopy cover for mines (R2 = 0.78, Adj. R2 = 0.77, RMSE = 16%) is more robust than the models developed for non-mines, mixed, and all areas combined. The objective of the third study was to determine whether four disturbance/recovery parameters (recovery time, disturbance minimum, recovery slope, and recovery maximum), alone or in combination with variables identified in the second study, enable robust estimation of woody canopy cover on reclaimed surface coal mines. Of the disturbance/recovery parameters, only recovery time made a significant contribution to the model (R2 0.45, Adj. R2 0.44, RMSE 14%). Addition of leaf-on and leaf-off NDVI improved the R2 to 0.54 (Adj. R2 0.53, RMSE 13%). Analysis of Landsat data has strong potential for identifying reclaimed mines and characterizing the extent to which woody canopy has recovered post-reclamation. / Ph. D.