Soil provides the foundation for plant and tree growth in a forested ecosystem. Boreal forest soil represents one the largest pools of carbon (C) in the northern hemisphere. In an undisturbed forest system, C and nutrients are effectively recycled and lost only through natural processes. Forestry operations remove large quantities of C and nutrients from the system in the form of biomass.
In here recent study Lilli Kaarakka researched the effects of physical and chemical disturbance on boreal forest soil and vegetation. Kaarakka examined two contrasting soil-affecting treatments practiced in Finland – stump harvesting and sprinkling infiltration as case studies. Sprinkling infiltration alters the chemical composition of forest soil, whereas stump harvesting results in changes especially in the physical structure of the forest soil.
The effects of stump harvesting on forest soil surface disturbance, soil C and N dynamics, understory vegetation, and coarse woody debris (CWD) were studied in stands located in Central and Southern Finland. The findings indicate that stump harvesting causes soil surface disturbance, and changes in soil C and nitrogen dynamics. Furthermore, the stump-coarse root compartment represent a significant portion of the stand CWD and belowground biomass. Consequently, forest management utilizing stumps will result in C losses from the stand.
The effects of sprinkling infiltration on forest soil, tree growth and understory vegetation and their respective recovery were studied in an experimental stand that had been infiltrated with surface water in order to produce artificial groundwater in Central Finland. Sprinkling infiltration had short-term effects on tree growth and long-term effects on soil processes and understory vegetation. Sprinkling infiltration can thus affect ecosystem recovery.
The results of this dissertation demonstrate that disturbances affect the function and structure of forest soil and these changes can persist on the surface of the soil in the organic layer and deeper in the mineral soil. Furthermore, it highlights the need for long-term perspectives in ecosystem management and planning.
The public examination of Lilli Kaarakka’s (MMM, M.Sc.) dissertation will take place Friday 9th of November 2018 at noon at University of Helsinki, Viikki Campus (Auditorium B2, Latokartanonkaari 7).