Efeitos de borda sobre comunidades de musgos (Bryophyta) epifíticos em área de Cerrado no Brasil Central
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2009-02-24
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Universidade Federal de Goiás
Resumo
Microclimatic changes enhanced by the proliferation of edges in fragmented landscapes,
known as "edge effects" may result on shifts in species composition, structure of communities
and ecological processes. Despite the dramatic increase in edge areas caused by
anthropogenic habitat fragmentation, the edges and their areas of influence is a relevant
structural feature also in the natural landscape. This is evident in the Cerrado biome, which is
suffering an accelerated degradation and habitat loss and is composed of mosaics of
vegetation types which are common boundaries or ecotones. The bryophytes are an ideal
group for assess the edge effects because are vulnerable to microclimatic changes promoted
by their physiological conditions, making them particularly useful as indicators of the adverse
fragmentation effects. Thus, this study aimed to assess how the communities of epiphytes
mosses (Bryophyta) respond to forest edges originated of anthropogenic fragmentation and
the natural edges in the grassland-forest transitions in the Cerrado. The study areas are located
in the Parque Estadual da Serra de Caldas Novas and its surroundings, including
municipalities of Caldas Novas and Rio Quente, state of Goiás. Sampling was done in three
habitat types: (1) gallery forests on the slopes of the mountain with abrupt transitions to rock
outcrops fields, (2) edge (0 to 10 m) and (3) interior (100 to 110 m) of seasonal forest
fragments surrounded by a matrix of grazing. These were the three treatments considered in
the analysis, described by the abbreviations: BN (natural edge), BA (anthropogenic edge) and
IF (interior of the fragment). For each treatment four replicates were selected. Four plots
(10´10m) were randomly delimited along transects (10´200m) for each treatment in each
area. For the sampling of mosses in the plots, were selected all trees with perimeter at breast
height (PBH) ≥ 20 cm and with minimum bryophytes coverage of 300cm2. For the
quantitative survey of mosses was employed the interception line method. The comparison of
Jackknife richness estimates (33.56 to IF, 30.56 to BA and 25.63 to BN) showed that there
were differences between IF and BN. The coverage of mosses was significantly higher in BN
than in BA (F2,45 = 5.34, p = 0.008). The analysis of similarities (ANOSIM) showed that the
community of mosses was more distinct in BN, and the composition of species in this
environment was significantly dissimilar to BA in IF (R = 0.198, p < 0001). Two factors may
explain the fact that the edge effect on species richness and coverage of epiphytic mosses has
not been shown in this study: (1) The homogeneity of the vegetation structure observed
between edge and interior and (2) the fact that the study had considered only the mosses,
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whereas many studies confirm a higher sensitivity to disturbance of the liverworts. Clearer
effects were observed between BA and BN, both in coverage and in species composition,
which is probably due to differences in spatial and temporal development of these edges, or
topographic features of the gallery forests, particularly the fact of being located in depressions
with creeks, which probably provides more moisture in these environments. The chi-square
test showed significant differences in the frequency of occurrence of life forms in the different
treatments, except for the tuft form. The greatest value of chi-square occurred to the
flabelliform life form, which predominated in BN, collaborating with the evidence already
presented of microclimatic conditions more favorable to mosses in BN, since the flabelliform
habit are intolerant to desiccation. This indicates that the use of functional groups of
bryophytes, such as life forms can generate more generalization and get clearer answers than
species richness in the evaluation of the edge effects.
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CARVALHO, Maria Adriana Santos. Edge effects on epiphytic mosses (Bryophyta) community in brasilian Cerrado. 2009. 61 f. Dissertação (Mestrado em Ciências Biológicas - Biologia) - Universidade Federal de Goiás, Goiânia, 2009.