Sazonalidade fenológica e aspectos funcionais de espécies lenhosas da caatinga : acompanhamento com câmera hemisférica e in loco

Abstract

Natural ecosystems need centuries to millennia to adapt to the damage caused by human interference and climate change. One way to follow this adaptation is through phenology that evaluates the recurrence of biological events in plants. For this, long-term studies are required, which can be obtained through digital cameras. The hypothesis of this work is that the phenological pattern of the caatinga species observed in loco is validated by the digital camera images, and aims to evaluate the phenological behavior and functional aspects of woody species in an area of caatinga and to compare with the images obtained from a hemispherical camera with observations made in loco. The field work was carried out in the municipality of Floresta, PE, during a period of one year, where 87 individuals belonging to eight species were studied. The abiotic variables were monitored by means of sensors coupled to a micrometeorological tower, installed in the experimental site. The plants were identified and monitored for phenological and morphophysiological parameters. A hemispherical digital camera was installed at the top of the tower and programmed to record an hourly image (from 6:00 a.m. to 6:00 p.m.) by means of which the green excess and the red index were identified, which indicate the green foliage and leaf senescence, respectively. The phenological phases were observed monthly and related to the meteorological variables and with functional characteristics of the plants. Two functional groups were found, composed of deciduous species and determined mainly by the following PCA variables: group 1 - flowering, budding, expanded leaf and wood density; group 2 - leaf area, fruiting, bark thickness, leaf fall and leaf area. The excess of green and the index of red, independent of the groups, showed that at the end of July was the period of greater senescence. In spite of this, there was variation in the excess of green, with the highest percentages of greening observed in May, reflecting the large amount of leaves produced and mature of the plants and smaller percentage in the month of June. Thus, the hemispheric camera constitutes a promising equipment to identify the phenological behavior of the plants in the field, without the continuous presence of the researcher.