Efeito do sombreamento sobre a fotossíntese e mortalidade em espécies não arbóreas do cerrado stricto sensu.
Carregando...
Data
2019-03-18
Autores
Marroni, Guilherme Genova de
Título da Revista
ISSN da Revista
Título de Volume
Editor
Universidade Estadual Paulista (Unesp)
Resumo
O Cerrado é considerado o segundo maior bioma brasileiro em extensão, com ampla diversidade de espécies e endemismo. Nas últimas décadas, áreas de Cerrado vêm sofrendo alterações fitofisionômicas, devido principalmente à ausência do fogo. A sua ausência tem possibilitado que áreas de cerrado stricto sensu sejam invadidas por espécies arbóreas, levando ao adensamento da vegetação, que por sua vez, reduz a riqueza de espécies não lenhosas, por diminuição da luminosidade. Assim, o presente estudo avaliou as respostas de três espécies não arbóreas típicas do cerrado stricto sensu em condições artificiais de sombreamento, a partir de observações fenológicas da mortalidade e capacidade de rebrota, além da análise de parâmetros fotossintéticos. Após 14 meses de experimento, a taxa de mortalidade foi de 43% para as plantas sombreadas, enquanto que as controles (plantas não sombreadas) tiveram uma mortalidade de 10%. As espécies avaliadas (Hyptis campestris, Cissampelos ovalifolia e Lepidaploa chamissonis), quando sombreadas, apresentaram menor ponto de saturação e de compensação luminoso e menor assimilação de carbono, demonstrando potencial de aclimatação. Contudo, plantas sombreadas estão abaixo do ponto de saturação de luz, o que junto com as rebrotas sucessivas pode ter levado ao exaurimento das suas reservas, comprometendo sua sobrevivência. Desta forma, o adensamento vegetacional pode ser um risco para a preservação de plantas não arbóreas de Cerrado.
The Cerrado is considered the second largest Brazilian biome in extension, with wide species diversity and endemism. In the last decades, areas of Cerrado have undergone phytophysiognomic alterations, mainly due to the absence of fire. Its absence has allowed tree species to invade areas of cerrado stricto sensu, leading to the densification of vegetation, which in turn reduces the richness of non-woody species, due to the reduction of luminosity. Thus, the present study evaluated the responses of three non-arboreal species typical of cerrado stricto sensu under artificial shading conditions, based on phenological observations of mortality and resprouting capacity, as well as the analysis of photosynthetic parameters. After 14 months of experiment, the mortality rate was 43% for shaded plants, while the controls (unshaded plants) had a mortality of 10%. The evaluated species (Hyptis campestris, Cissampelos ovalifolia and Lepidaploa chamissonis), when shaded, showed lower saturation point and light compensation point and lower carbon assimilation, showing acclimatization potential. However, shaded plants are below the point of saturation of light, which along with the successive resprouts can have led to the exhaustion of their reserves, compromising their survival. In this way, vegetational densification may be a risk for the preservation of non-arboreal Cerrado plants.
The Cerrado is considered the second largest Brazilian biome in extension, with wide species diversity and endemism. In the last decades, areas of Cerrado have undergone phytophysiognomic alterations, mainly due to the absence of fire. Its absence has allowed tree species to invade areas of cerrado stricto sensu, leading to the densification of vegetation, which in turn reduces the richness of non-woody species, due to the reduction of luminosity. Thus, the present study evaluated the responses of three non-arboreal species typical of cerrado stricto sensu under artificial shading conditions, based on phenological observations of mortality and resprouting capacity, as well as the analysis of photosynthetic parameters. After 14 months of experiment, the mortality rate was 43% for shaded plants, while the controls (unshaded plants) had a mortality of 10%. The evaluated species (Hyptis campestris, Cissampelos ovalifolia and Lepidaploa chamissonis), when shaded, showed lower saturation point and light compensation point and lower carbon assimilation, showing acclimatization potential. However, shaded plants are below the point of saturation of light, which along with the successive resprouts can have led to the exhaustion of their reserves, compromising their survival. In this way, vegetational densification may be a risk for the preservation of non-arboreal Cerrado plants.
Descrição
Palavras-chave
Cerrado., Fotossíntese., Sombra., Espécies não arbóreas., Curvas de resposta à luz, Photosynthesis., Shade., Non-arboreal species., Light response curves.