Total ginger removed from all four plots
Digging out the A quadrats was especially strenuous because ginger roots are very heavy. The plots were positioned far back from my house, because the forest farther away from the house is in a much more "natural state" than that close by. All of the ginger that was removed from the plots had to be put inside garbage bags and then taken to the local dump. It couldn't be thrown in a hole, because it'd grow back in an instant, even if it were deeply buried; and it couldn't be used as plant mulch because it is too stringy to shred. I did this entire procedure on September 19, 2004. On November 2, all the pH measurements were taken again, and on December 22, all of the native plants that had been measured for height before were re-measured, and all the pH measurements were taken once more.
Chart 1: Soil pH Averages Per Quadrant in Plot 1 (Click to enlarge)
At the end of this process, I analyzed my results. Although at first I didn't detect any obvious trends, under close analysis the data presented an interesting result. The pH measurements taken near hapu'u pulu ( Cibotium glaucum) plants were much more acidic (6.5, 5.1, 6.1, and 6.0) than those taken near the Kahili ginger ( Hedychium gardnerianum), which proved to be much closer to alkaline (6.99, 6.89, 7.00, and 6.70).
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A malnourished hapu'u pulu (Cibotium glaucum) growing out of the middle or a large area of ginger in Plot 4
When I researched previous studies, I found out that other invasive plants, such as Morella faya and Falcateria moluccana, actually changed the chemical makeup of the soil, making it easier for invasive plants to grow and harder for natives to grow. It is possible that H. gardnerianum is doing the same. Previous studies, especially one performed by Kolea Zimmerman, showed that hapu'u pulu is a very important nursery log for native plants, including 'ohi'a lehua. It may be assumed that native plants prefer more acidic soil, because the soil surrounding the hapu'u is more acidic. The soil surrounding the ginger is nearer to alkaline, and many fewer native plants grew next to the ginger than next to the hapu'u.
There were some uncontrolled variables that may have affected this study. The positioning of my experimental plots, for example, may have influenced my data. If the four plots had been directly adjacent to each other, which they were not, the tree cover overhead would have been more similar, as would the amount of rainfall. The rain in Volcano is very much affected by eruptions from Kilauea and therefore most likely contains some acid. If the plots had been close together, the amount of acid rain received would have been more consistent. The level of available sunlight would also have been more consistent. And if the plots had been all in one place, they would have been easier for me to access, and I might have been able to take more data samples from them.
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