Fig 1.
To monitor seed rain along the entire hydrological gradient, three replicate transects of five seed traps (squares picture left; close-up picture right) were pinned to the ground perpendicular to the stream channel. Vegetation surveys were carried out in permanent quadrats adjacent to each seed trap (rectangles; picture left). Stream water levels were registered using pressure transducers in water level gauges within 30 m of the nearest transect.
Fig 2.
Water level fluctuations relative to the mean water level during the sampling periods for the Hagmolenbeek (HM), Hooge Raam (HR) and Kleine Aa (KA).
Sampling periods are separated by vertical dotted lines. Seed trap elevation (relative to mean water level) of representative transects are indicated by horizontal lines.
Table 1.
Overview of the number of species and number of seeds deposited in seed traps per research site, period of monitoring and season.
Fig 3.
The effects of flooding and season on the number of species of deposited seeds (upper panels) and number of seeds (lower panels).
A comparison of flooded (FL) and non-flooded seed traps (Not FL) is given in the left panels (box widths proportional to number of seed traps). The effect of seed trap elevation relative to mean water level is given in the right panels (negative values represent seed traps below the average water level, positive values represent seed traps above it). Summer and winter data are displayed in different greyscales. In the right panels, blue lines represent modelled relationships between field data (circles) and the explanatory variables season and elevation, as analyzed in negative binomial GLMMs. Grey ribbons indicate the 95% confidence intervals (based on fixed effects only).
Table 2.
Forward selections of fixed effects in (negative binomial G)LMMs explaining species number and number of seeds in the seed traps.
Fig 4.
The effects of flooding and season on community-weighted means of seed traits of the deposited seed community.
A comparison of flooded (FL) and non-flooded (Not FL) seed traps is given in the left panels (box widths proportional to number of seed traps). The effect of seed trap elevation relative to the mean water level is given in the right panels (negative values represent seed traps below the average water level, positive values represent seed traps above it). Summer and winter data are displayed in different greyscales. In the right panels, blue lines represent modelled relationships between field data (circles) and the explanatory variables season and elevation, as analyzed in LMMs. Grey ribbons indicate the 95% confidence intervals (based on fixed effects only).
Fig 5.
Distance triplots of partial redundancy analyses on Hellinger-transformed seed deposition per research location with respect to the explanatory variables season and seed trap elevation.
Site scores are indicated by symbols, with symbol type determined by seed trap position along the riparian gradient, ranging from the dry end (upbank) to the wet end (channel) of the riparian gradient. Contour lines are added around sites scores with the same symbol type.