Genesis of a soil seed bank on a primary succession in the Central Alps (Otztal, Austria)

Soil seed bank and standing vegetation were investigated on the Rotmoos Glacier foreland (Otztal, Tyrol, Austria) along the chronosequence (i.e. on the pioneer, early, and late successional stage) as well as on a subalpine pasture beyond the glacier foreland (old successional stage). We aimed to answer the following questions: (1) How large are soil seed banks along the successional gradient? (2) Do the seed banks reflect the actual standing vegetation or do they remember earlier successional stages or do they represent already the next successional stage? Soil samples were collected in late spring and a germination experiment was performed. The differences in seed bank size between succession stages and soil layers were proved by a two-way ANOVA. Similarities between seed bank and standing vegetation were tested by the Morisita-Horn index. Our results indicated that seed bank size significantly increased along the chronosequence, from 273 seedlings/m(2) in the pioneer stage, 820 seedlings/m(2) in the early successional stage, to 3527 and 3674 seedlings/m(2) in the late and old successional stage, respectively. The seed bank size was correlated with the vegetation cover along the successional gradient. The early succession stages were more similar to the standing vegetation as the later stages. A persistent soil seed bank has been found all along the successional gradient; however, size and composition changed from the pioneer to the old successional stage. (C) 2008 Elsevier GmbH. All rights reserved.