Vegetation development on deposit soils starting at different seasons |
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Authors: | Franz Rebele |
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Institution: | (1) Institute of Ecology, Technical University Berlin, Rothenburgstr. 12, Berlin, 12165, Germany |
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Abstract: | Permanent plots were created in different seasons (autumn and spring) and filled with two substrates: nutrient-rich topsoil
and nutrient-poor ruderal soil (n = 5 for each treatment). My objectives were to assess the influence of starting season on initial species composition, whether
differences at the start cause divergent or convergent pathways of succession and which mechanisms are operating during vegetation
development. Mean species richness (number of species per plot) and mean total cover of herb layer differed significantly
between substrates and changed significantly during 10 year succession, but there were no significant differences with respect
to starting season. However, seasonal as well as substrate effects were evident for particular dominant species and for the
pattern of successional sequences. When succession on topsoil plots started in spring, first summer annuals dominated, then
monocarpic and polycarpic perennial herbs, then herbaceous perennials together with woody perennials, and at the end of the
decade woody perennials. When succession started in autumn, polycarpic perennial herbs dominated from the beginning, and then
were replaced by woody perennials in the second half of the decade. On ruderal soil, there was a less rapid but continuous
increase of polycarpic perennial herbs and woody species, both on spring and on autumn plots, whereas short-lived plants were
more abundant in the first years and then decreased. Species turnover was very high from the first to the second year for
all treatments (except topsoil plots starting in autumn), but slowed down during succession. Priority effects due to starting
season caused high dissimilarity at the start on the nutrient-rich substrate, but convergent succession towards the end of
the first decade. The main mechanisms during early succession on the nutrient-rich topsoil were tolerance based on different
life-history traits and inhibition due to reduced light availability. There was no evidence for obligate facilitation. However,
an indirect facilitative effect by annuals, which slowed the development of herbaceous perennials down, and thus facilitated
growth of woody species, could be seen on topsoil when succession started in spring. |
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Keywords: | Convergence Divergence Permanent plots Succession Topsoil Urban ecology |
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