Pollination and dispersal trait spectra recover faster than growth form spectrum during the spontaneous succession in sandy old-fields

Edy Fantinato, Judit Sonkoly, Giulia Silan, Orsolya Valkó, Béla Tóthmérész, Balázs Deák, András Kelemen, Tamás Miglécz, Silvia Del Vecchio, Francesca Bettiol, Gabriella Buffa & Péter Török

Forest-steppe mosaic in the Kiskunság sand region, Hungary. Photo credit: Balázs Deák.

The widespread abandonment of agricultural areas and croplands is making large areas available to test techniques for the restoration of grassland habitats. Two main contrasting strategies have been adopted so far: active technical reclamation and “passive” spontaneous vegetation succession. Spontaneous succession relies on locally available supplies of seeds, which include soil seed bank and seed rain from adjacent plant communities. Besides being the most natural and cost-saving solution, spontaneous successions offer us the opportunity to study the temporal dynamics of grassland recovery, either through a synchronic (more demanding) or diachronic approach. In both cases, we gather strategic data to inform active grassland restoration plans.

A successful grassland restoration requires the recovery of both structure and function, i.e. the processes that ensure the self-organization and self-maintenance capacity of grassland ecosystems. Specifically, processes such as pollination, seed dispersal and vegetative growth deeply influence the functionality of plant communities by influencing plant species occurrence and assemblage. Processes linked to sexual reproduction (i.e. pollination and seed dispersal) are crucial in assuring plant species arrival and establishment in a given community, while vegetative growth can influence small-scale assemblage of plants through competitive and/or facilitative interactions for space and soil resources. Considering that reproductive and vegetative processes operate at different scales, we investigated whether their recovery times differed as well. To this aim, we compared the spectra of reproductive (pollination- and dispersal-related) and vegetative (growth form) traits between old-fields (i.e. former croplands) of different age and pristine grasslands. Specifically, we assessed which of the two sets of plant traits in old-field spontaneous succession first showed a spectrum comparable to that of pristine grasslands.

We carried out the study in the Kiskunság sand region (Central Hungary), where large-scale abandonment of low-productivity croplands has occurred since the seventies. This allowed us to compare reproductive and vegetative traits across recovered grasslands of different age (<10 yr old; 10–20 yr old; 20–40 yr old) and pristine grasslands.

We found that during spontaneous succession, the reproductive trait spectra became similar to that of pristine grasslands earlier than the vegetative one. In 10 yr old abandoned fields, pollination- and dispersal-related trait spectra did not show a significant difference to those of pristine grasslands; wind-mediated pollination and dispersal were the prevailing strategies. Contrarily, vegetative traits recover much slower, and differences in the growth form spectrum could be observed even after forty years of abandonment; in recovered grasslands erect leafy species prevailed, while the fraction of dwarf shrubs and tussock-forming species was significantly lower than in pristine grasslands.

When actively restoring grassland, we have to bear in mind that the recovery of the ecological processes of pristine grasslands might require different amounts of time, depending on the spatial scale at which they operate. Reproductive trait spectrum recovered earlier than the vegetative one since reproductive attributes first determine plant species arrival and occurrence in grassland communities. The recovery of the vegetative trait spectrum needs more time as interactions for space and soil resources operate on a smaller spatial scale.

This is a plain language summary for the paper of Fantinato et al. published in the Applied Vegetation Science. This post was prepared by Edy Fantinato, Gabriella Buffa, Judit Sonkoly and Péter Török.