Epsilon Archive for Student Projects

Abstract

Boreal forests have the potential to mitigate the increased concentrations of greenhouse gases (GHGs) in the atmosphere. However, forestry alters the soil biogeochemical processes which can cause an increase in GHG emissions from nearby water bodies, soil and vegetation. Soil biogeochemical processes related to GHG emissions are in general higher in the wet zones of soil and vegetation near freshwater bodies – riparian zones (RZs). Leaving the RZs during clearcutting as riparian buffer zones (RBZs) can prevent soil disturbances and hence prevent GHG emissions from nearby water bodies. However, whether the design of the RBZs matter in terms of minimising GHG emissions from the soil and vegetation is not sufficiently investigated. This study aimed to investigate how clearcutting in a boreal forest located in Vindeln municipality in Västerbotten, Sweden, affected the soil temperature, soil moisture and soil-atmosphere carbon dioxide (CO2) and methane (CH4) fluxes and whether the factors differed between a wide (15 meters) and a narrow (5 meters) RBZ. The study followed a Before/After-Control/Impact (BACI) approach and the measurements were performed in two RBZs in an impact site before and after clearcutting and in a control site without clearcutting between the measurement occasions. Tree-atmosphere CO2 and CH4 fluxes of the two tree species silver birch (Betula pendula Roth) and Norway spruce (Picea abies (L.) H. Karst.) were also compared between the two RBZs in the impact site after the clearcutting. The results showed significant higher soil temperature (1.3 ± 0.5 ºC) after clearcutting relative to before clearcutting, in the narrow buffer relative to the control site. The results showed also significant lower soil CH4 uptake (0.0008 ± 0.00074 μmol m-2 s-1) after clearcutting relative to before clearcutting, in the narrow buffer relative to the control site. No significant clearcutting effects on soil moisture or soil-atmosphere CO2 fluxes were however shown. Both the silver birches and Norway spruces showed, in general, both CO2 and CH4 emissions. No significant differences in any of the factors soil temperature, soil moisture, soil-atmosphere CO2 and CH4 fluxes or tree-atmosphere CO2 and CH4 fluxes between the two RBZs were shown. Hence, according to the results of this study, the design of the RBZs, or more specifically the width, had no effect on CO2 or CH4 emissions from soil and vegetation in the RBZs. However, leaving stable RBZs that prevent an increase in soil temperature would, according to other similar studies, possibly reduce changes in soil biogeochemical processes related to GHG emissions from nearby water bodies, soil and vegetation and would therefore be recommended in boreal forests.