Text by Lauri Laanisto & Martin Zobel
Alvar grasslands are probably one of the better-studied ecosystems in Europe. They are narrowly distributed in Swedish islands, Estonia, and tiny bits also in western Russia near St Petersburg. (Though, rather similar ecosystems can be also found around the Great Lakes area, in Northern America.) And somehow it has also happened that the density of good plant ecologists is also high in aforementioned countries…
Although we already know quite a lot about how alvar ecosystems function – from historical and large-scale processes building up species richness (for example this one) to disturbance practices and short-term diversity dynamics (for example that one) -, there are still some blank spots in our knowledge. This particular study tried to cover one of these – secondary succession dynamics of often overlooked bryophytes and lichens in alvar communities, and how does it correspond with plant secondary succession dynamics in the same communities.
For that the covariation of plants, bryophyes and lichens was recorded in several alvars in different successional stages (young, intermediate, mature). The results indicate, as empirically predictable, that from the richness point of view plants have the fastest successional dynamics, then come bryophyes, and the lichens are the slowest. However, the changes in all life forms, whether in the abundance or diversity, happened rather concurrently. Different life forms seem to be associated in different successional stages, it´s just that bryophes and especially lichens need more time to arrive.
Citation: de León, D. G., Neuenkamp, L., Gerz, M., Oja, E., & Zobel, M. Secondary succession in alvar grasslands–do changes in vascular plant and cryptogam communities correspond?. Folia Geobotanica, DOI: 10.1007/s12224-016-9260-1 (link to full text)
Although bryophytes and lichens are frequently vital components of aboveground communities, their interrelationships with vascular plant communities are poorly known. We addressed small-scale covariation of vascular plant and cryptogam (bryophytes and lichens) communities during secondary succession from abandoned gravel pit towards thin soil calcareous (alvar) grassland communities. The cover, richness and diversity of vascular plants, bryophytes and lichens were studied. Whereas vascular plants showed the fastest successional dynamics in terms of richness, bryophytes showed a fast successional dynamic in terms of cover and diversity; the establishment of lichens was the slowest. THe cover, richness and diversity of different life forms changed concurrently. There were significant associations among the species composition of all life forms considered. The strongest relationship was found between lichens and vascular plants in mature stages. We conclude that alvar grasslands are certainly an example of a community in which the association between the vascular plant and the cryptogam communities may influence the overall vegetation succession, and the strength of this association increases during secondary succession.