Influência do efeito de borda, da perda de habitat e de fatores abióticos na estrutura da comunidade lenhosa em fragmentos de cerrado denso na Alta Bacia do rio Araguaia
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2016-03-08
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Universidade Federal de Goiás
Resumo
Anthropogenic changes have changed land cover patterns and caused fragmentation of
ecosystems. These changes have several consequences for biodiversity, such as habitat
loss and isolation, creation of anthropic matrix, and edge effect. Few studies have
evaluated the effects of fragmentation in the Cerrado, especially the effects on
vegetation structure and abiotic attributes of savanna formations. Here, we sampled 17
fragments of Dense Cerrado in the Upper Rio Araguaia basin, which is a highly
fragmented area. Specifically, we compared the more altered Sub-basin of the Rio Claro
with the more conserved Sub-basin Rio Garças. Fragments had the fragile
Quartzipsamment soils. All fragments were larger than 50 ha and had pasture matrix.
Specifically, we asked the following questions: 1) What is the percentage of area lost by
fragments in the last 30 years? 2) How area loss influence the woody plant community
structure? 3) The species composition similarity decreases with geographical distance
between fragments? 4) The edge-interior gradient affects the woody plant community
structure? 5) How microclimate and physico-chemical variables vary along an edgeinterior
gradient? 6) The community structure of woody plants is influenced by
microclimate and physico-chemical characteristics of the soil? We sampled all woody
plants with diameter ground higher than 30 cm or equal to 5 cm, in three 20 x 50 m
plots along a edge-interior gradient in each fragment. We collected soils between 0 to 20
cm deep in all plots and the matrix. The air and soil temperatures, air humidity, altitude,
geographical position, and light intensity were collected along with soil samples. We
recorded 8,749 woody plants, belonging to 131 species. Fragment area was significantly
reduced between 1985 and 2013, but the historical and current area were not associated
with community structure and species diversity. We also did not find a correlation
between compositional similarity and geographic distance between fragments.
Additionally, 2,877 individuals of 116 species occurred at the edge, 3,038 individuals of
110 species occurred at intermediate environments, and 2,995 individuals of 107 species
occurred in the center of fragments. However, species composition and community
structure did not differ along the edge-interior gradient. Also, abiotic variables did not
differ along the matrix-edge-interior gradient. However, these variables differed
between the two sub-basins. The Rio Claro Sub-basin had higher values of Ca/CTC and
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Ca/K, which are related to nutrient availability in the soil. The spatial distribution of
plant species was influenced by altitude, humidity, silt, organic matter, pH, and calcium.
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SIQUEIRA, M. N. Influência do efeito de borda, da perda de habitat e de fatores abióticos na estrutura da comunidade lenhosa em fragmentos de cerrado denso na Alta Bacia do rio Araguaia. 2016. 92 f. Tese (Doutorado em Ciências Ambientais) - Universidade Federal de Goiás, Goiânia, 2016.