Tropical forests have been a center of study to understand global patterns of native and invasive species distribution. Non-native species can take advantage of limiting resources, which creates a chain of competition between native species. The objective of this research was to quantify the competitive effects of soil nutrient manipulation on native vs. non-native plants, using their photosynthetic rates and biomass as a productivity measurement. Understanding the ecological processes associated with vegetation in a controlled environment are key to comprehend plant physiology in more complex ecosystems. We anticipated that biomass and photosynthetic rates for native species will performed better under low nutrient availability and non-native plants will performed better in conditions of higher nutrient availability. Plant species representative of Hawaiian wet forests such as (Acacia koa (native)) and (Psidium cattelanium) (invasive)) were selected. By using the LI-COR 6400, methods were based on measuring maximum photosynthetic rates (Amax) under ideal conditions of light, CO2, temperature, and humidity. Nutrient reduction treatments were performed with carbon amendments as sawdust and sucrose, and the nutrient addition treatment was performed with fertilizer application. The pots had five soil nutrient manipulation levels: control, nutrient reduction high, nutrient reduction low, nutrient addition high, and nutrient addition low.
Results/Conclusions
Results were analyzed using a one-way ANOVA test, in which Acacia koa had higher photosynthetic and biomass rates than Psidium cattelanium when they were both planted in the same pots. Furthermore, there was no significant difference (P-value of 0.287) in photosynthetic rates through the different soil nutrients availability, meaning that the native species can grow and be productive when they are in competition with non-native species in the same pot. These results partially supported my hypothesis that non-native species performed better when they are in high nutrient availability in the soil. This results give a positive feedback to the native species of Hawaii showing that even though soils are rapidly changing because of the disturbance and non-native species presence, we can say that Koa is a plant that can adapt to different types of environments, but it’s evident that it prefers soils with low nutrient availability. The implication of these results may help the scientific and local community to establish a baseline for restoration and forest management in the Pacific Region.