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Forest Management and Understory Bees

by:Annika Keeley.

As described in the section on sustainable forest management, forest management had little impact on the species richness of the understory plants. However, many studies in other tropical forests have shown that the number of bird and butterfly species decreases rapidly when forests are logged and managed . To see if the Tirimbina forest managed for timber production conserves tropical biodiversity Manuel Rincón from CATIE and his colleagues from CATIE, the Smithsonian Tropical Research Institute, and the Instituto Nacional de Biodiversidad (INBio), studied understory bees 6-8 years after the implementation of liberation and shelterwood treatments . They chose understory bees, because they knew that these animals are adapted to live and forage in deep shade and high relative humidity. They expected that animals adapted to these conditions would respond quickly to changes in the microclimate on the forest floor caused by canopy openings from logging and management.

Before talking about the results of this study, let us first learn a little bit about the bees. As you can imagine for the tropics, there is an incredible diversity of bees in the Tirimbina reserve. There are three major groups: the stingless bees (Meliponini), the orchid bees (Euglossini), and another very diverse group called the Halictinae. The stingless bees live in colonies. They can only bite, but not sting. They nest in hollow trunks, tree branches, underground cavities, or rock crevices, and some species produce so much honey that people will keep them in boxes, even though they are tiny . The orchid bees are thus named because the male bees visit orchid flowers to collect not nectar but fragrances that they’ll use attract females . The orchids rely on the male bees for pollination. The Halictinae group that occurs at Tirimbina consists mostly of solitary, small species. Most bees belong to this group. It is so diverse and so little studied that 62% of the species found during the study at Tirimbina had not been scientifically described.

understory bees 1
understory bees 2

The conclusion of the study was surprising: the number and kinds of bees in the managed forest did not differ from that in the unmanaged forest. This means that either the forest disturbance caused by forest management did not change the understory conditions for the bees, or 6-8 years after the management action, the understory was again similar to that of a natural, closed forest. Thus, the understory bees responded differently than expected and unlike other groups of animals like birds and butterflies respond to changes in the forest. Different groups of animals need to be studied to determine the effect of forest management on biodiversity for conservation!

Lawton, J.H., D.E.Bignell, B.Bolton, et al. 1998. Biodiversity inventories, indicator taxa, and effects of habitat modification in tropical forests. Nature 391: 72-76. Rincón, M., D.W.Roubik, B.Finegan, D.Delgado, and N.Zamora. 1999. Understory bees and floral resources in logged and silviculturally treated Costa Rican rainforest plots. Journal of the Kansas Entomological Society 72(4): 379-393. Ramirez, S.R., D.W.Roubik, C.Skov, and N.E.Pierce. 2010. Phylogeny, diversification patterns and historical biogeography of euglossine orchid bees (Hymenoptera: Apidae). Biological Journal of the Linnean Society 100: 552– 572.

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