Ecossistema de várzea: etnobotânica e ecofisiologia

Abstract

The Amazon lowlands are fluvial floodplains that have forests which are periodically inundable by white water rivers and that present extensive rich areas speaking of natural resources of great ecological, economic and social importance for the riparian communities. This paper aimed to characterize the ecophysiological behavior of ethno botanical value species in the Amazon lowland based on the stomatal conductance (gs) in two seasonal periods (rainy and dry) and two distinct topographic environments (low floodplain and high floodplain). An ethnobotanical survey was conducted concerning 32 families that were polled through semi-structured questionnaires. To analyze data ethnobotanical rates were used, such as the Relative Frequency of Citation, the Use Value, the Loyalty Level, the Rank Order Priority and the Diversity and Equitability by Shannon- Winner. There were 33 mentioned species and 32 identified ones that fit 7 different categories of use, alimentary, medicinal, fuel, marketing, construction, craft and shading .The cataurizeiro (Crataeva tapia L.) was the most cited species (56%) and the sapucaia chest nut tree (Lecythis pisonis Cambess.) was the one with the highest Use Value (1.0) and the category alimentary use displayed the greater diversity. (H’=1, 43). The Saracura community has rich knowledge regarding the use of native plant species, which are used mainly as food. For the ecophysiological characterization based on the gs, among 33 species seven were selected: Garcinia braziliensis , Crataeva tapia, Nectrandra cuspidate, Senna reticulate, Laetia corymbulosa, Pseudobombax munguba, Neea macrophylla. The gs physiological readings were achieved with the aid of an AP4 porometer in three different timetables (8:00 – 9:30, 12:00-1:00 p.m, 5:00-6:30p.m) through the day. It was observed that the floodplain species have variable physiological plasticity, and the gs differs among the seasonal periods and the topographic environments. In the dry period the stomatal conductances among the species are homogeneous and reduced, whereas in the rainy one they are heterogeneous and high. N. macrophylla demonstrated to be the most tolerant species regarding the water deficit of the dry period and S. reticulata, on the other hand, the most sensitive. The most tolerant species when it comes to flooding was C. tapia and the most sensitive was G. brasiliensis. Therefore we can say that there is a difference regarding these species ecophysiological behavior between the dry and rainy periods.