As invasões biológicas e seus efeitos sobre os sistemas locais de usos de plantas na caatinga e no carrasco – Nordeste do Brasil.

Abstract

The aims of this work were to register the floristic composition and the structure of the alien flora in two regions of the northeastern semi arid, their potentialities to local residents, as well as to test hypothesis related to influence of alien species linked to cultural issues, verifying whether they act in the cultural impoverishment, enrichment and/or cultural facilitation. The work was carried out in anthropogenic areas in two semidecidual dry forests at the northeast of Brazil (Caatinga and Carrasco). Initially the floristic sampling was conducted to the recognition of the alien flora (360 plots). After that, semi-structured interviews were done and the checklist-interview method was applied with aim of to gather information about the recognition, availability and local uses, as well as to understand how such plants are settled in the residents’ cultural context from the two communities. In relation to the floristic composition, the families with the most richness are Fabaceae and Poaceae both with 8 species (Crato) and Asteraceae (4), Malvaceae, Rubiaceae and Solanaceae (three species (Caruaru)). In Crato, the most representative species in number of individuals are Diodella teres (1535) and Bidens bipinnata (814). To Caruaru are Diodella teres (1066) and Blainvillea acmella (944). Shannon Index was 2,13 to the community settled in the carrasco vegetation and 2,09 to the community located at caatinga area there was no significantly statistical difference between the diversity of two areas (t = 1,382, p>0,05). In relation to the richness of the tow areas there was a low similarity (J = 0,291). In anthropogenic áreas of carrasco, density recorded was 4.739 ind. 180m-2, to environment of caatinga of the overall density was lower, 5.283 ind. 180m-2. In Minguiriba (carrasco) there was a negative correlation between dominance perceived by residents (value ranging from 1 to 4, were 1 is very dominant and 4 few dominant) and abundance found in the plots (rs=-0.4701, p=0.0033). Already in Riachão de Malhada de Pedra (caatinga) there was no correlation between the abundance observed by the community informants and recorded within the plots (rs=-0.1018,p=0.5548). The predominant use was forage in the two communities (81% e 83% - carrasco and caatinga, respectively), followed by medicinal plants seguido (59% and 47%), food (13% and 11%), technology (10% and 25%) and others (21% and 8%). The most recognized plants are also the locally most used plants (p<0,05). In relation to local validation of the three hypothesis of cultural invasion, it can be observed that the “model” was not applied suitably to the studied communities, with the regard to cultural impoverishment, because there are reports to the enrichment and cultural facilitation to all uses categories in the studied areas. With our results, we can highlight the local importance of alien plants to people from the two communities, in relation to availability, recognition, uses and local cultural representation of such species.