Hur en ökad marktemperatur påverkar fotosyntes och markrespiration i en boreal skog

Sammanfattning: During the year of 2008, a powerful earthquake hit the southern part of Iceland, which changed the geothermal conditions in the area around the city of Hveragerdi. Elevated soil temperatures in a nearby forest plantation have contributed to a unique opportunity for researchers to study how an increased soil temperature affects the boreal forest ecosystem, something that partly can be connected to the climate changes which are happening today. The boreal forest is representing a carbon sink and a buffert for the emissions that occurs. Changes in this ecosystem will for that reason contribute to major impact for the global carbon cycle. To study the impact of how elevated soil temperatures affects different processes in a plantation of Sitka spruce, studies were made on the photosynthesis of the trees and the respiration from the soil. One aim of the studies was to get indications for how the boreal forest ecosystem may look like in the future and how its role as a carbon sink will change. The soil respiration and the photosynthesis of the trees were measured at different temperature levels in the soil. According to the results, the ability to capture carbon dioxide in the trees increased up to +3oC, of which it thereafter decreased. On the other hand, in the soil ecosystem an increase in respiration was measured as a response of elevated temperature. In total, the soil ecosystem constituted a source of carbon dioxide. Conclusions from the measurements of photosynthesis and soil respiration indicated that the boreal forest probably will continue as a sink in the future, depending though on how big the increase in soil temperature will be. If our results can be generalized for what will happen when soil temperature increases in the boreal forest, it will strongly depend on how big the increase in average temperature will be. This will determine if the boreal forest in the future will continue to be a carbon sink or not. The role of the boreal forest as a carbon sink can therefore affect the global climate changes in a negative way at an increased soil temperature. The concentration of carbon dioxide will then increase even faster in the atmosphere.