Resumo Trabalho

AS CROSTAS BIOLÓGICAS DE SOLO DA CAATINGA E OS FATORES INFLUENCIANDO SUA PRESENÇA

FLÁVIA DANIELLE AMORIM DE OLIVEIRA, ARTUR GONÇALVES DE SOUZA MENEZES e orientado por MARCELO TABARELLI e orientado por MARCELO TABARELLI

Biological soil crusts (BSC) are communities of microorganisms and non-vascular plants that cover soil surfaces, primarily along arid regions of the planet. Formed as an intrinsic association between soil particles and organisms such as cyanobacteria, algae, lichen and moss, BSC can be the main source of primary productivity, soil fertility and energy balance locally (Ferrenberg, 2017). We recently observed communities of BSC in the Brazilian semi-arid Biome known as Caatinga. The BSC cover, community structure and ecological roles lack research in the Caatinga, although this system has continually been suffering from anthropic pressures like subsistence farming cycles, overgrazing and trampling by domestic animals, and the extraction of wood (Ramos et al. 2008) that may be negatively affecting its biota. This study aims to better understand the BSC cover in Caatinga, analyzing predicting variables of its presence, and describing the organisms present in the community (which has not been described yet); thus, contributing to the global assessment of BSC distribution, and to the knowledge of Brazilian semiarid biological soil crust. Through the point-intercept methodology, the soil cover was analysed, with the quantification of the explanatory variables: (1) trampling area; (2) canopy openness; (3) litterfall; and (4) soil penetrability. The light penetration was measured through gap light analyzing using hemispherical photographs ran in the software Gap Light Analyzer. All the variables were tested using a multiple linear regression test. The community was described to the genus level. The taxa found include (1) one genus of cyanobacteria (Schizothrix); (2) one genus of liverwort (Riccia); (3) one genus of fungi (Buelia); (4) four genus of lichens ( Acarospora, Cladonia c.f. cervicornis spp. vertilicillata, Lecidea, and Peltula - a genus of new occurrence in Brazil). Refering to the distribution, the variable trampling area accounted for the distribution of crusts with great significance (p<0,001). The other variables could not explain the presence of BSC significantly. That indicates that the environmental drivers are not the main factor limiting BSC distribution, but actually the anthropic factors are better explaining its presence or absence.. Thus, this study reiterates the reasonably well structured view that trampling acts as a pressure factor limiting BSC distribution (Belnap, 2011). The BSC of the Caatinga may be under specially severe pressure, since the region counts with abundant flocks of goats, that may be suppressing these populations. This scenario may be a severe one, as the BSC are expected to influence the system’s biogeochemistry and global climate regulation.

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