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Mosaicos Geoecológicos da Tundra de Nunavik: Análise Espacial da Dinâmica Recente Através de Deteção Remota (Kangiqsualujjuaq, Canadá)
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Os impactes das mudanças climáticas mostram-se particularmente incidentes no Ártico e Subártico.
Nas regiões com permafrost rico em gelo, observam-se alterações na paisagem, como a formação de
lagoas termocársicas, arbustização e a expansão da vegetação para norte. As unidades geoecológicas de
um setor do Subártico canadiano foram caracterizadas usando dados de deteção remota de ultra-alta e
muito alta resolução. A área de estudo localiza-se no sudeste da Baía de Ungava, a 8 km a noroeste de
Kangiqsualujjuaq, no limite tundra-floresta boreal. Estas unidades resultam de um passado de
deglaciação, submersão e emersão marinha, acompanhada por agradação e fusão do permafrost. A
análise foi baseada em imagens óticas e multiespectrais de drone e em dados de espetrometria de campo
recolhidos em 2022, numa fotografia aérea histórica de 1960, e em imagens multiespectrais de satélite
de muito alta resolução de 2013 e 2019. Foi elaborada cartografia geomorfológica e das comunidades
vegetais, e analisada a evolução das comunidades entre 2013 e 2019. As unidades geoecológicas foram
identificadas e caracterizadas segundo a distribuição das comunidades e a sua relação com as formas e
processos geomorfológicos. A evolução das unidades entre 1960 e 2022 foi avaliada para uma área
amostra. A área de estudo é morfologicamente diversa, apresentando moreias de fundo, depósitos
fluviomarinhos, palsas e lithalsas. Entre 2013 e 2019, os processos de arbustização revelam-se pouco
significativos, dado o reduzido período de análise, prevalecendo a influência de fatores de microescala.
Coníferas e Salix destacam-se pelo aumento de área ocupada, por alargamento da copa e colonização
por Salix em setores onde ocorreu perturbação. Na análise da dinâmica geoecológica registou-se uma
maior influência do clima no controlo da dinâmica da paisagem, sobrepondo-se aos constrangimentos
ecológicos e geomorfológicos locais. Planaltos e aglomerações palsicas e lithalsicas destacam-se pela
maior perda de área, associada à fusão do permafrost.
Climate change has been significantly impacting the Arctic and Subarctic. In ice-rich permafrost regions, landscape changes have been occurring, such as the formation of thermokarst lakes, shrubification processes, and the northward expansion of vegetation. Using ultra-high and very highresolution remote sensing data, the geoecological units were characterized and analyzed, for an area at the tundra-boreal forest transition in the southeastern of Ungava Bay, in the Canadian Subarctic, 8 km northwest of Kangiqsualujjuaq. These units reflect a history of deglaciation, marine submergence, and later emergence. The last period was accompanied by permafrost aggradation and thaw. The analyzis was based on optical and multispectral drone images and field spectrometry data collected in 2022, historical aerial photographs from 1960, and very high-resolution satellite multispectral images from 2013 and 2019. Geomorphological and vegetation community maps were produced. The evolution of vegetation communities between 2013 and 2019 was determined. Geoecological units were identified and described based on the vegetation community distribution and its relation with landforms and geomorphological processes. The evolution of the units between 1960 and 2022 was analyzed in a sample area. The study area exhibits diverse landforms, such as moraines, fluviomarine terraces, palsas, and lithalsas. Shrubification processes between 2013 and 2019 were of small significance, due to the short period analyzed. Tree and shrub colonization rates were mainly affected by microscale factors. Conifers and Salix showed the highest increase, mostly due to vertical growth and canopy expansion. New colonization and secondary succession events in disturbed areas were also identified within Salix communities. When analyzing geoecological dynamics over a longer period, it becomes evident that climate has a greater influence on landscape evolution and dynamics than local ecological and geomorphological constraints. Palsa and lithalsa plateaus and agglomerations, experienced the greatest area loss due to abrupt permafrost thaw.
Climate change has been significantly impacting the Arctic and Subarctic. In ice-rich permafrost regions, landscape changes have been occurring, such as the formation of thermokarst lakes, shrubification processes, and the northward expansion of vegetation. Using ultra-high and very highresolution remote sensing data, the geoecological units were characterized and analyzed, for an area at the tundra-boreal forest transition in the southeastern of Ungava Bay, in the Canadian Subarctic, 8 km northwest of Kangiqsualujjuaq. These units reflect a history of deglaciation, marine submergence, and later emergence. The last period was accompanied by permafrost aggradation and thaw. The analyzis was based on optical and multispectral drone images and field spectrometry data collected in 2022, historical aerial photographs from 1960, and very high-resolution satellite multispectral images from 2013 and 2019. Geomorphological and vegetation community maps were produced. The evolution of vegetation communities between 2013 and 2019 was determined. Geoecological units were identified and described based on the vegetation community distribution and its relation with landforms and geomorphological processes. The evolution of the units between 1960 and 2022 was analyzed in a sample area. The study area exhibits diverse landforms, such as moraines, fluviomarine terraces, palsas, and lithalsas. Shrubification processes between 2013 and 2019 were of small significance, due to the short period analyzed. Tree and shrub colonization rates were mainly affected by microscale factors. Conifers and Salix showed the highest increase, mostly due to vertical growth and canopy expansion. New colonization and secondary succession events in disturbed areas were also identified within Salix communities. When analyzing geoecological dynamics over a longer period, it becomes evident that climate has a greater influence on landscape evolution and dynamics than local ecological and geomorphological constraints. Palsa and lithalsa plateaus and agglomerations, experienced the greatest area loss due to abrupt permafrost thaw.
Descrição
Palavras-chave
Arbustização Deteção remota Geoecologia Permafrost Termocarso