ABSTRACT
The edge effect, triggered by habitat fragmentation, alters forest microclimates and influences the life cycle of plants. Phenology may indicate the first changes in phenological patterns in response to the effects of climate change. Climate regulates the phenology of ferns and climatic triggers influence plants in tropical and subtropical regions differently. This study analyzed and compared the phenology of fern communities of three sub-areas - natural edge, artificial edge, and forest interior - of a fragment of Araucaria Forest in the Floresta Nacional de São Francisco de Paula, Rio Grande do Sul, Brazil, and its relationship with meteorological, astronomical, and edaphic variables. Abiotic and edaphic data were monitored concomitantly with phenological data (leaf renewal and senescence and sporangia formation) in each sub-area over a biennium. Temperature, air humidity, and soil moisture, which undergo changes with the edge effect, influenced edge plants. Leaf renewal was the main phenophase showing strong indication of changes in vegetative patterns in natural and artificial edge communities. Among the communities, that of the artificial edge signaled phenological changes that could compromise the development of ferns if effects intensify over time. In this respect, the phenology of artificial edge ferns differed from that of plants growing in originally natural formations (natural edge and forest interior), showing that exogenous transformations represent a new environmental situation for ferns to develop.
Subject(s)
Araucaria , Ferns , Forests , Ecosystem , Microclimate , SeasonsABSTRACT
Climate regulates the fern phenology and climatic triggers influence plants from tropical and subtropical regions differently. Ferns depend on climate to regulate their life cycle, because they do not require animal interaction to reproduce. Through the pioneering study of the phenology of Araucaria forest understory in subtropical climate of Brazil, our main aims were (i) to verify which climatic variables influenced the phenological pattern of the community, (ii) to identify the differences in seasonality of ferns in distinct climatic zones of Brazil, and (iii) to compare the phenological pattern of ferns growing in other subtropical regions of the world. In an Araucaria forest fragment, we monitored the phenology of the fern community (leaf production, leaf senescence, and sporangium formation) over 2 years. At the same time, we collected photoperiod, temperature, and precipitation data. Ferns phenology was classified as continuous, discontinuous, regular, and irregular. Our results showed photoperiod and mean temperature as the best predictors for phenology. The reproductive event was seasonal, and the fern community presented themselves as continuous, irregular (activity index), and regular (intensity index) phenophases. Unlike ferns from tropical regions that generally regulate themselves by the rainfall, some ferns in a non-seasonal environment have seasonal behavior in their phenophases due to the greater amplitude of photoperiod and temperature. The community showed the same pattern of leaf production observed in populations of other subtropical regions in the world. This behavior represented the biological response of the vegetation dynamics in relation to the climatic variability of subtropical environment.
