Spatial variability of the soil seed bank in a heterogeneous ephemeral wetland system in semi-arid Australia

Abstract

Soil seed banks are an important component of plant community diversity in ephemeral wetlands, allowing many species to persist through unpredictable periods of flood and drought. Spatial variation of extant vegetation in such habitats commonly reflects patterns of flood history and often varies predictably between broadly differing hydro-geomorphic habitat types. Here we investigate whether spatial variation of soil seed banks is similarly controlled by fluvial processes at this scale. Results are presented from a seedling emergence trial using samples collected from a range of habitat types, and at different scales within these, in the ephemeral Narran Lakes system in semi-arid Australia. Composition and structure of soil seed banks varied significantly between habitat types reflecting broad differences in flood frequency. As predicted, germinable seed abundance was found to be highest in intermediately flooded habitats. Variability in soil seed bank composition at a local scale was also found to be influenced by hydrology with greater spatial heterogeneity evident in the river channel as well as amongst the least frequently inundated riparian and floodplain habitats.

Ecological significance of hydrological connectivity for wetland plant communities on a dryland floodplain river, MacIntyre River, Australia

“…However, other mechanisms are also likely. As has also been shown in other studies of seed bank germination, the largest number and diversity of germinations occurred in this study under water logged conditions (Warwick and Brock 2003;Webb et al 2006;James et al 2007;Reid and Capon 2011). Germinations from the submerged treatments were few, and this result cannot be attributed to light limitation, particularly given that germination was lowest in the water replacement treatment which removed algae that were potentially shading new germinants.…”

“…Trials were conducted in a greenhouse commencing in April and were maintained for 16 weeks, a duration that was chosen based on past studies that suggest that periods in excess of 12 weeks are required to allow plants to establish and be identifiable (Casanova and Brock 2000;Webb et al 2006). This duration also ensured substantial temperature change, which can also increase the diversity of germinant communities (Reid and Capon 2011;James et al 2007). As plants matured and flowered they were identified and removed so as not to add to the seed bank (Capon 2007).…”

“…Removing plants reduces competition and encourages continual germination in order to see the full extent of the seed bank, assuming germination is triggered by the imposed treatments (Reid and Capon 2011). Plants that became too large for the pots before they could be identified were repotted in deeper pots and separated from the remaining samples so as to reduce mortality and encourage flowering to aid identification (James et al 2007). …”

Variações espaço-temporais no estoque de sementes do solo na floresta amazônica

“…A densidade e a composição florística do banco de sementes também variam com os estágios sucessionais da Floresta Tropical, com a redução da densidade total e aumento na representatividade de sementes de espécies arbóreas lenhosas nos estágios mais avançados da vegetação (Saulei e Swaine 1988), entre microsítios dentro da mesma área (Rajan et al 1995;Costa, 1999;Miranda Neto et al 2010), com a produtividade dos ecossistemas localizados em diferentes altitudes e estações climáticas distintas influenciando os ciclos fenológicos das espécies (Williams-Linera 1993;Jordano 2000) e ainda pela ocorrência de eventos catastróficos como incêndios (Smith et al 2000) e inundações (James et al 2007).…”

Ephemeral wetlands of the Pilliga Outwash, northwest NSW.

“…To our knowledge, since 2005, information on temporary and ephemeral wetlands has only been collated for some areas of New South Wales (Hunter & Bell 2007;Bell et al 2008;Hunter & Bell 2009). In other areas such as western New South Wales, such information is often only available as part of localized vegetation description (McGann et al 2001), regional vegetation description (Benson et al 2006;Benson et al 2010), or from descriptions of communities establishing from seed banks (James & Capon 2007;Porter et al 2007). Wetland covers 5.6% of New South Wales; of this portion 96% is in western New South Wales (Kingsford et al 2004).…”