Relationships between soil seed bank composition and standing vegetation along chronosequences in a tropical dry forest in north-eastern Brazil

Abstract

To better understand the role of seed banks in ecological succession of dry forests, we compared similarities between vegetation and seed banks and assessed the relative contributions of seed dispersal and persistence in chronosequences in the Brazilian semi-arid region. To sample the standing vegetation and the seed bank, we collected data in three sites with three successional ages in each one (5 y, 25 y and 45 y). A total of 180 soil samples (three sites × three successional ages × 10 plots × two components) were collected. The composition of the seed bank was assessed by the seedling emergence method. Of 166 species identified in the standing vegetation, only 50 (30.1%) were also present in the seed bank, resulting in low similarity (Jaccard index = 0.02–0.21) and reflecting the rarity of woody species and the dominance of annuals (71% of richness). The relative importance of seed persistence and seed dispersal to seed banks composition were balanced in most cases (difference was not rejected in four out six comparisons). Those results suggest that seed banks in tropical dry forests are largely the result of high dispersal rates and the persistence of allochthonous annual species that contribute to decoupling seed bank and vegetation composition.

Dispersal syndrome influences the match between seed rain and soil seed bank of woody species in a Neotropical dry forest

“…The similarity between seed rain, soil seed bank and standing vegetation in our SDTF was higher than values reported for other forest ecosystems (45% vs an average of 31% ± 3.7: Hopfensperger, 2007), and among the highest for tropical forests (Hardesty & Parker, 2002; Hopfensperger, 2007; Gomes et al , 2019). This remarkably high similarity can be related to two not mutually exclusive factors.…”

“…In this sense, high similarity could prevent the presence of pioneer species in the soil seed bank. Although scarce, available information about the similarity between standing vegetation and soil seed banks in SDTF is contradictory, with some studies showing high similarity (Garwood, 1989) and others finding a low similarity (Rico‐Gray & García‐Franco, 1992; Uasuf et al , 2009; Savadogo et al , 2017; Gomes et al , 2019). This apparent discrepancy could be explained, at least partially, if the effects of dispersal syndrome and dispersal phenology are explicitly considered.…”

“…Nevertheless, in mature communities, the match can be low due to inputs of seeds coming from surrounding sites and communities, or due to the long-standing permanence in the soil seed bank of species from previous successional stages (Beatty, 1991;Laskurain et al, 2004;Martins & Engel, 2007;Gomes et al, 2019), even if they are not currently present in the standing vegetation (Pärtel, 2014).…”

“…Strong similarity among standing vegetation and soil seed banks has been documented in some pioneer communities such as those of ephemerals in some drylands (Caballero et al , 2008). Nevertheless, in mature communities, the match can be low due to inputs of seeds coming from surrounding sites and communities, or due to the long‐standing permanence in the soil seed bank of species from previous successional stages (Beatty, 1991; Laskurain et al , 2004; Martins & Engel, 2007; Gomes et al , 2019), even if they are not currently present in the standing vegetation (Pärtel, 2014). Mismatches can also emerge from the differential ability of plant species to establish soil seed banks.…”

“…However, the few studies available have shown that soil seed banks of woody species are also variable among SDTFs. While some studies have revealed a high presence of standing woody species in the soil bank (Garwood, 1989), other studies found a low similarity between the seed bank and standing vegetation (Rico‐Gray & García‐Franco, 1992; Uasuf et al , 2009; Savadogo et al , 2017; Gomes et al , 2019). Among other factors, these discrepancies could be related to differences in the seed banking ability of species with the different dispersal syndromes (Valenta et al , 2015).…”