Avaliação do estresse térmico na flora dos inselbergs do Alto Itatiaia

• Autor(a) principal: Ramalho, Henrique Dutra Souto
• Data de Publicação: 2018
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UERJ
• Texto Completo: http://www.bdtd.uerj.br/handle/1/7914
• topic: Increasing Temperature; Ecophysiology; Global Warming; Tropical Mountain; Barbacenia gounelleana; Ferneseea itatiaiae; Alstroemeria foliosa; Chionolaena isabellae; Afloramento Rochoso; Ecofisiologia; Aquecimento Global; Mudança Climática; Barbacenia gounelleana; Fernsea itaitiaie; Alstroemeria foliosa; Chionolaena isabellae; Ecofisiologia vegetal - Itatiaia (RJ); Inselbergs - Itatiaia (RJ); CNPQ::CIENCIAS BIOLOGICAS::BOTANICA

The vegetation of Itatiaia Nacional Park is rich in life forms and aggregate species of different phylogenetic origin like Andean, Brazilian Atlantic Forest and Brazilian Cerrado which even occur on rocky outcrops (inselbergs). This environment exhibit peculiar abiotic conditions such as lack of soil, short water supply, high irradiance and wide thermal variations. Photosynthesis is highly influenced by temperature and in a climate change scenario there is an urgent need to investigate about the capacity of tropical species to acclimate. Moreover, the inselberg s ecological succession depends on focal species that mitigate the harsh environmental conditions. Thus, the aims of this study are (1) to study the response of four rupicolous plant species two nursing pioneers (F. itatiaiae and Barbacenia gounelleana) and two climax species (Chionolaena isabellae and Alstroemeria foliosa) to thermal stress in a daily and seasonal scale; (2) simulate global warming effect (about +3ºC) in situ with open top chambers and to define the thermal limit of photosynthesis. To reach objective (1) it was considered the effects on ecophysiological traits such as photochemical efficiency of photosystem II, photosynthetic pigments and relative water content. Objective (2) was assessed by studying the drop in net carbon assimilation, the impact of rising temperature on Fv\Fm and stomatal conductance, using simultaneous analysis of gas exchange and chlorophyll fluorescence. Studied species showed distinct ecophysiological strategies to survive environmental fluctuations in light, temperature and water supply of mountain inselbergs, so that there was no unifying pattern determined by successional status (pioneers and climax). Climatic variation of temperature is more pronounced in a daily basis than seasonally. Although, only looking at seasonal amplitude is possible to reach extreme temperatures for photosynthesis, i.e. below 5°C and above 23°C. F. itatiaiae is a CAM species which the mesophyll reach temperatures close to 0°C in winter and yet showed no drop on photochemical efficiency, while others kept the mesophyll 4°C above air temperature. Thereby, F. itatiaiae and C. isabellae showed higher heat sensitivity, since photosynthetic compensation point was close to 25°C, very close to current maximum air temperature at Itatiaia National Park. Suggesting that any climatic heating would impact significantly these species. Alternatively, B. gounelleana showed positive assimilation rates in temperatures even above 40°C. In a scenario of increase in atmospheric temperature, our results indicate that rock colonization would remain through B. gounelleana successional way, and thus, a loss of functional and specific diversity should be expected