Shifts in functional traits and functional diversity between vegetation and seed bank

Abstract

Question Does the seed bank have a different functional trait signature to the vegetation and is this difference affected by productivity and disturbance? Do functional diversity differences exist between the vegetation and seed bank and are the differences modulated by productivity and disturbance. Location An area of diverse land use on the west coast of Scotland. Methods Parallel vegetation and seed bank surveys were carried out across 30 sites contrasting in land use, and hence productivity and disturbance regime. Data were analysed to assess overall differences between the seed bank and vegetation in community‐weighted mean for selected functional traits and to test if the difference was affected by productivity or disturbance. Three functional diversity indices were calculated for each seed bank and vegetation sample – functional richness, functional divergence and functional evenness – and each index was assessed for overall differences between the seed bank, the vegetation and differences modulated by disturbance and productivity. Results There were clear differences in many community‐weighted mean traits between the seed bank and the vegetation. Plants in the vegetation were characterized by increased stature, more conservative leaf traits, wind pollination and by being perennial, whereas plants in the seed bank had higher seed longevity, higher seed masses and were more frequently insect‐ or self‐pollinated. There was no difference in functional richness between the seed bank and the vegetation, and while both the seed bank and the vegetation functional richness were significantly lower than expected, the vegetation showed a bigger deviation from expectations compared to the seed bank. The functional diversity indices revealed different relationships between seed bank and vegetation against productivity and disturbance. Functional divergence (and its standardized effect size) indicated stronger habitat filtering for the vegetation at high levels of productivity or disturbance, while the effect size of functional richness and functional evenness suggested stronger filtering on the seed bank at high levels of productivity and disturbance. Conclusions The significant difference in traits between the seed bank and vegetation mean that following disturbance this is likely to have a considerable impact (at least in the short term) on ecosystem function. Functional diversity patterns were less clear, with conflicting evidence on habitat filtering, depending on the metric chosen.

Riparian plant guilds of ephemeral, intermittent and perennial rivers

“…Many of the traits that we expected to be linked exclusively with water availability were also related to fluvial disturbance. Canopy height varied strongly with water availability, but short canopy (thus less time to grow to maturity) also is selectively advantageous under very high disturbance (Westoby, ; Pakeman & Eastwood, ), explaining our finding of a positive relationship between canopy height and elevation above thalweg. Low‐density wood allows for rapid growth to reproductive age given ample water and thus is adaptive in high resource environments that are periodically ‘reset’ by scouring floods.…”

“…Abundance of plants with edible seeds or fruits is important in sustaining particular guilds of mammals and birds (Koniak, Noy-Meir & Perevolotsky, 2009). To address concerns regarding declines in pollinators and crop-pollinating ecosystem services, future assessments could include morphological adaptations for pollen vectors (Sacchi & Price, 1988;Lamb & Mallik, 2003;Pakeman & Eastwood, 2013).…”

Revisiting the Holy Grail: using plant functional traits to understand ecological processes

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Functional diversity: a tool for answering challenging ecological questions

“…Hejda & de Bello () used FD indices to show that invasive plants often introduce novel trait combinations to invaded plant communities. Pakeman & Eastwood () show contrasts in the relationship between FD and ecological gradients for vegetative vs seed bank communities. If future studies find a consistent disconnect between FD in vegetation and seed banks, this might improve our understanding of how disturbance impacts FD in plant communities.…”