Florian Hartig

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Hydrological recruitment niches of wetland plants are associated with dormancy, alternating temperature, and oxygen requirements

Tereza Mašková, Florian Hartig & Peter Poschlod

Basic and Applied Ecology, 93, 52–62 (2026)
Cite this
@article{maskova2026hydrological,
  author = {Tereza Mašková and Florian Hartig and Peter Poschlod},
  title = {Hydrological recruitment niches of wetland plants are associated with dormancy, alternating temperature, and oxygen requirements},
  journal = {Basic and Applied Ecology},
  volume = {93},
  pages = {52--62},
  year = {2026},
  doi = {10.1016/j.baae.2026.04.004},
}

DOI: 10.1016/j.baae.2026.04.004
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Abstract

Permanently or seasonally flooded wetlands are hotspots for plant diversity. Their community composition usually depends strongly on hydrological conditions, suggesting that hydrology drives community assembly. However, the mechanisms underlying this effect are still not fully understood, and they could arise either through hydrological effects on reproduction, growth or mortality of plants. Here, we concentrate on the effect of hydrology on seed germination, also known as the recruitment niche. We investigated seed germination in sediments from eight localities in southern Germany, exposing them to four permanently and two temporarily flooded treatments and tested for the association of species' hydrological niches with their functional traits (type of dormancy, alternating temperature and oxygen requirements for germination). Our results show that hydrological conditions significantly affected species-specific germination. Interspecific variation in germination responses could be partly explained by seed physiological traits: non-dormant species were more likely to germinate in non-flooded hydrological treatments and species with alternating temperature and oxygen requirements exhibited higher germination in dry and wet treatments. The longer flooded conditions persisted, the more negatively they affected the germination of these species. Overall, we conclude that hydrological conditions have trait-mediated species-specific effects on seed germination, and that these effects likely contribute to the final community composition.

What the paper shows and why it matters

(AI-generated)

Plant communities in wetlands change markedly along gradients of flooding, but it is unclear at which point in the life cycle water does its sorting: it could act on the reproduction, growth or survival of plants. The regeneration-niche idea (Grubb 1977) stresses that species differ in their regeneration requirements, which makes germination a candidate early filter. Yet how water levels and the timing of flooding shape where wetland species germinate, and whether physiological properties of seeds explain the differences between species, has been little studied. The paper asks whether flooding filters wetland species at germination, and whether seed traits explain which species pass.

The paper argues that germination acts as a hydrological filter on wetland plant communities, and that seed traits partly predict which species pass it. In a pot experiment, sediments with seeds from eight ponds and river arms in southern Germany were kept under four constant water levels, and for four sites also flooded to 40 cm and drained in June or August; seedlings of 66 species were analysed. Species whose seeds are not dormant rarely germinated under permanent flooding, whereas species with dormant seeds showed no significant difference between flooded and unflooded treatments. Species whose germination is reported to be higher under alternating temperatures or reduced under low oxygen germinated mainly in the unflooded treatments (dry to moist, or wet at the surface), and more after June than after August drainage. As these two responses are correlated in the data, the paper cannot separate them. Comparing individual species with published moisture indicator values for adult plants suggests that the germination niche can differ from the adult niche.

The paper reads the results as supporting the view that small differences in water level, and the timing of events such as a summer drawdown, can decide which species emerge from the seed bank and so send a newly forming or disturbed wetland towards different communities. It stresses a limit: only germination from seeds was studied, not vegetative regeneration or seedling survival, so the findings are likely not precise predictors for established wetlands, but are believed to be indicative for new communities at disturbed or newly created wetlands where the seed bank is intact. It sees this recruitment filter as relevant for predicting how plants persist under environmental change.

References