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RAINFOREST RESEARCH

Teachers attending the Amazon Workshop will join Dr. Lundie Spence, NC Sea Grant College Program, in her Banana/Fertilizer Research Project. This study will take place on the subsistence farm of Roger and Dona Tilde Ramos, which is near Rio Napo and Rio Sucusari. It is hypothesized that the application of nutrients through the use of commercial inorganic fertilizer can enhance plant growth of crops and delay or alleviate the need to slash and burn additional rainforest land.

Although the natural system of the Amazon basin is well-balanced with a rich diversity of plants and large biomasses, the soils of the Basin are old, weathered clays with very little residual nutrients. Slash and burn techniques are the only means for new plant material to thrive. Subsistence farming depends on these techniques. The slashing of existing or natural vegetation, followed by drying and subsequent burning, returns a set of nutrients to the soil in the form of ash. The standard nutrient story is that these nutrients can provide growth of banana, rice, legumes, and manioc for two to four seasons; then the nutrients are exhausted. The farmer is then forced to slash and burn another hectare to sustain crops.

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Our excursion to the Amazon rainforest was an exciting and educational experience. Our main goal was to assess fungal diversity, including mycorrhizal fungi in both primary and secondary forests. Since our microscopes were confiscated at customs upon arrival in Iquitos, completion of certain aspects of the study were out of the question. We were able to set up decomposition studies, spore traps, and do a general survey of decomposer fungi at the ACTS and Explorama sites.

The decomposition set-up may be of interest to teachers as it is easy to set up and also to assess the data. We used standard filter paper and determined the weights, placed single filters in an ‘envelope’ of hardware cloth and set them out at three different levels: litter layer surface, soil surface, and buried. The filters were removed after seven days, air-dried, and brought back to UM-Flint to determine weight loss (the length of time should be increased for temperate soils). An interesting aspect to this study was that the filters placed on top of the litter layer were quite obviously appreciated by the ants! They were almost half-chewed when we harvested them. So much for microbial decomposition!

There are a couple of points of interest with respect to fungal composition. First, the genera of fungi in the tropics are the same as those found in temperate regions (fungi don’t care where they live!). The most conspicuous fruiting bodies are of Marasmius spp. (Basidiomycotina), although there are plenty of Xylariales (Ascomycotina) present on the walkways. One problem we encountered during our survey was the lack of fruiting bodies for most species. Keying out a specimen usually requires 3-4 fruiting bodies and we were ecstatic when we encountered enough to do so. We think that, unlike what occurs in temperate regions, there aren’t environmental cues (or at least not the same cues) to trigger the production of fruiting bodies. Therefore, in order to do a complete survey, one would have to be able to collect throughout the year!

As far as the spore traps are concerned, this is a project we will be working on for a long time. We are currently isolating spores and culturing them to identify them. It is tedious and time-consuming work but will, of course, be worth the time and effort expended.

On a personal note, the most exciting event for me occurred on the canopy walkway at dawn. I was actually fortunate enough to see a light gap being created. It was visually awesome and spiritual as well.

Tracy Wacker, University of Michigan-Flint