Photos from the Field: Seed & Fern Spore Bank of an African Tropical Forest.

Esaete, J., Eycott, A. E., Reiniö, J., Telford, R. J. and Vandvik, V. (2014), The Seed and Fern Spore Bank of a Recovering African Tropical Forest. Biotropica, 46: 677–686. doi: 10.1111/btp.12167

Seed banks contribute to forest regeneration after disturbance, but less is known about fern spore banks, particularly in a paleotropical context. We sampled the buried seed and fern spore bank in Mabira Forest, a 300 km2 forest in central Uganda, to explore the effect of time since disturbance. Soil cores (5 cm depth) were taken from 39 plots across three different classes of ‘recovery’: (1) not disturbed since 1950; (2) logged between 1950 and 1980; and (3) cleared for agriculture between 1970 and 1990 but reforested since. Plant emergence was monitored in a glasshouse. We predicted that the seed bank would reflect time since disturbance, with more pioneer species in recently disturbed stands, and that the fern spore bank would reflect stand age less closely due to greater dispersal capacity. We recorded a median 752 seeds per square meter, most of which were trees; the most abundant species was the invasive tree Broussonetia papyrifera. The fern spore bank was twice as dense, but 95 percent of fern spores were of one species, Christella parasitica. Tree seed density was significantly affected by time since disturbance with fewer seeds in the older stands. Herb seed density, fern spore density, and species richness for all groups were not significantly affected by time since disturbance. Neither seed bank nor fern spore bank closely resembled the aboveground vegetation. We compared our results to existing literature on seed banks in tropical forests, finding that our densities are relatively high for African forests, but low compared to the Neotropics and Australia.
For more on the project, visit the project web page.
Some ferns have other means of spreading than only spores.(Photo by Vigdis Vandvik)

Some ferns have other means of spreading than only spores.(Photo by Vigdis Vandvik)

 Several team members plan the project. Lead author Josephine Esaete is the one wearing an orange cap.(Photo by Vigdis Vandvik)

Several team members plan the project. Lead author Josephine Esaete is the one wearing an orange cap.(Photo by Vigdis Vandvik)

Small, fast rivers generate a humid environment where ferns thrive. (Photo by Vigdis Vandvik)

Small, fast rivers generate a humid environment where ferns thrive.
(Photo by Vigdis Vandvik)

(Photo by Vigdis Vandvik)

Many species of the ferns certainly generate plenty of spores, but they are not common in the soil (or hard to germinate?). (Photo by Vigdis Vandvik)

Broussonetia papyrifera, an small invasive tree (co-author Richard Telford, 180cm, is included for scale). (Photo by Vigdis Vandvik)

Broussonetia papyrifera, an small invasive tree (co-author Richard Telford, 180cm, is included for scale).
(Photo by Vigdis Vandvik)

Christella parasitica, the spores of which completely dominated the dataset, soon got the nickname 'sun fern' because of its' ability to exploit sunflecks. (Photo by Vigdis Vandvik)

Christella parasitica, the spores of which completely dominated the dataset, soon got the nickname ‘sun fern’ because of its’ ability to exploit sunflecks. (Photo by Vigdis Vandvik)

Some ferns seemed to relish the very deep shade under the thickest canopy. (Photo by Vigdis Vandvik)

Some ferns seemed to relish the very deep shade under the thickest canopy. (Photo by Vigdis Vandvik)

Subsistence farming in enclaves within the forest.(Photo by Vigdis Vandvik)

Subsistence farming in enclaves within the forest.(Photo by Vigdis Vandvik)