by Piter Kehoma Boll
Most ordinary people think of a tree as just that, a tree, a big plant with a hard tall stem which provides shade and oxygen and sometimes beautiful flowers or delicious fruits. So, it may not seem such a big issue to cut a tree and plant another to compensate that. After all, in some years that seedling will grow and replace completely the role of its precursor.
However, if you look closer, you’ll find that a tree is so much more than just a tree. You may see that there are other things growing on it, like epiphytic ferns, bromeliads, orchids, mosses, mushrooms, lichens, and mistletoes. And you can also find many animals eating or living on it as well, for example birds, spiders, harvestmen, insects, tree frogs, and even land planarians!
Moss and fungi growing on an orange tree. You can see some (out of focus) oranges in the background. Photo by Piter Kehoma Boll.*
Many invertebrate and epiphytic plant communities are highly dependent on the age of the trees, as well as on the tree species richness in forests. Saproxylic insects, i.e., those that live on dead wood, such as fungus gnats and beetles, are common in old forests. The same happens to lichens and, as they become established, they offer a range of food and nesting habitats for a lot of invertebrates.
An epiphytic fern over the same orange tree. Photo by Piter Kehoma Boll.*
As many invertebrates associated to old-growth forest are highly specialized, having a strong link with their host tree, they are very susceptible to forest fragmentation. That’s one of the reasons why a seedling cannot replace the ecological role of an old tree.
This feather tells us a bird has passed around here. Photo by Piter Kehoma Boll.*
Some studies have also shown that the whole community of organisms associated to trees, including epiphytic plants and invertebrates from the canopy and the leaf litter around it, can be influenced by intraspecific genetic variation of trees, i.e., even trees from the same species can have different organisms on and around them depending on their individual set of genes. This has implications for the whole ecosystem, since genetic diversity of trees influence the species diversity of the community.
So the next time you see a tree being cut, remember that it’s not just a tree being cut, but a whole community being put to death. And I hope that it will make you and other people to think a little bit more before doing something that looks far more trivial than it really is.
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Moeed, A., & Meads, M. J. 1983. Invertebrate fauna of four tree species in Orongorongo Valley, New Zealand, as revealed by trunk traps. New Zealand Journal of Ecology, 6, 39-53
Walsh, N. 2012. A preliminary study into the use of canopy invertebrates and sampling techniques in relation to forest indicators in a fragmented Scottish woodland – application and management. The Plymouth Student Scientist, 5 (2), 44-79
Zytynska, S., Fay, M., Penney, D., & Preziosi, R. (2011). Genetic variation in a tropical tree species influences the associated epiphytic plant and invertebrate communities in a complex forest ecosystem. Philosophical Transactions of the Royal Society B: Biological Sciences, 366 (1569), 1329-1336 DOI: 10.1098/rstb.2010.0183
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