Final Project

Introduction Puerto Rico has seen significant changes in flora species in its 40 million years of evolutionary history. In its original state, Puerto Rico had nearly 100 percent forest cover with 547 native species. However, as with many other regions, European discovery of the island lead invasive species and land use practices to decrease forests so that 6 percent of Puerto Rican forest cover remained and 1 percent was original, unmodified forest. With species introduction, a total of 750 species can now be found on the island. Chemical activity and geographic overlays play a major role in the introduction of invasive species in Puerto Rico. With increased global warming, the chemical make-up of Earth’s surface is undergoing a major change. Increased levels of nitrogen and carbon can now be found in soils, plant matter, and in the air humans and plants take in. This all has an effect on the introduction of invasive species. Furthermore, geographic entities such as the building of homes, roads, and water structures further help the growth of invasive species. Many native species cannot tolerate the stress of urban life, while invasive species seem to thrive in areas cultivated by humans. Methods With the help of a professor at UCLA and a former employee of hers, I obtained the GIS data needed for this project. I received a land cover layer, soil type layer, and a layer containing the points of the research. I also received a Microsoft Excel sheet containing all the chemistry data connected to coordinate points needed to analyze the chemical effects pollution has on invasive species. Along with more data, I was only given ammonium and nitrate by themselves, so I needed to calculate the ratio of ammonium to nitrate in excel. The only information I needed to download was major roads in the United States of America, which I obtained from the UCLA Mapshare website. My first step was to create a map of the study site to give viewers an idea of where the study site was. Therefore I had to create a data frame that contained the points of the research and the cover type map provided to me. However, when I went to insert the legend, it contained about 100 different cover types. Therefore, I had to add a new value to the attribute table of the areas that were necessary for the study. I then created the legend from this new data frame. My next step was to interpolate the chemical data given to me to see the effects of nitrogen and nitrogen fixers in the forest area. I added two more data frames and the added XY Data to the maps, which provided the maps with the points connected with the chemical data. I then interpolated both nitrogen and the ratio, given to me in the excel sheet, using the IDW technique. These provided me with regions most affected by the chemical changes due to pollution. I then needed to evaluate the geographic influences, so I created a new data frame which contained the major roads of Puerto Rico. In order for the buffer not to take a long time, I selected attributes by location and selected the roads only located in Puerto Rico. I then proceeded to use the Buffer Wizard to create four 1 km buffers around the roads to indicate which areas where affected most by human influence. Lastly to see these results put together, I used the raster calculator to calculate both roads and nitrogen as well as the ratio and the effect of roads. I then put the last touches on the maps, making them all align, adding a north arrow and scale bar, and making the maps look visually appealing. Results The interactions between invasive species and soil chemistry are a two-way interaction. Invasive legume trees often fix nitrogen in areas where there was originally native forest cover filled with native non-nitrogen fixers. Nitrogen fixers are able to fix nitrogen from out of the air and soil, while native non-nitrogen fixers are left at a major disadvantage because they are unable to perform these activities. Nitrogen fixers therefore have a competitive advantage in areas where there are low nitrogen levels because native species will be unable to get enough nitrogen in order to survive, since nitrogen is one of the most common limiting factors for tree growth. Based on the nitrogen level map, the areas in green should be the areas with the most invasive species and the white areas with the most native. The map illustrates that areas around the outskirts of the study site should have the most invasive species while the farther in one goes, the less invasive species should be seen. The green to yellow areas indicate what areas are most suitable for the growth of invasive species. The second soil chemistry and invasive species interaction is the relationship between ammonium and nitrate. At the same time that invasive species are fixing nitrogen, they are increasing soil nitrogen overtime and actively bringing in nitrogen from the atmosphere. This can be changing and increasing mineral nitrogen pools. I calculated a ratio of ammonium over nitrate to indicate the introduction of where invasive species may be changing mineral nitrogen in Puerto Rican forests. The area most altered by the ammonium/nitrate ratio is shown in white on the Ratio: Ammonium/Nitrate map. This indicates an area where invasive species are altering the chemical make-up of the soil. Due to this finding, invasive species should also be found in the area surrounding the white spot. This point is also located on the outskirts of the study area, which coincides with the data presented in the nitrogen level map. Invasive species should most likely be found on the outer regions of the study area. Changes in geography of the region also play a major role in predicting where the introduction of invasive species can be found in Puerto Rican forests. Invasive species can more easily flourish in regions closer to roadsides, while native species suffer. Native species prefer secluded regions that are least affected by human impact. The Road Buffer map shows that the points located in the center of the study area are those that are farthest away from the major roads. Therefore, once again the areas located in the center of the study area, should be the ones that see the least amount of invasive species coming into their region. They are protected by the distance from the road side to their own location. Finally, the calculation maps once more prove that areas located in the center of the study site should be the ones least affected by invasive species. When adding together the effects of nitrogen and the effects of the roads, the Nitrogen+Roads map shows that the outskirted regions are the low regions, which for nitrogen are the ones most likely to aid the growth of invasive species. The Ratio+Roads maps also reflects the same relationship of decentralized locations having higher values, which for this ratio reflects more evidence of the introduction of invasive species because they are fixing nitrogen into the soil. Conclusion Because the study regions are located in areas surrounded by urban life, geographic changes such as roads and global warming harshly affect the introduction of invasive tree growth in forests. Based on the evidence from the maps, invasive species should be found most often in the areas more closely connected to the runoff of pollution and acitivty from the urban center. Therefore, the regions that will remain most preserved should be the regions located in the center of the study area away from the effects of pollution and the wear and tear of daily urban life, such as the building of roads and homes. Saving these center locations, and continuing to keep these areas largely untouched, will help to preserve the beauty and originality of Puerto Rican forests.