There is an increasing interest for using renewable sources to replace a part of the fossil fuels in energy production in the European Union. In Finland, like in many forested countries, forest bioenergy is considered a sustainable and easily accessible energy resource. The aim of this study was to estimate the extent of soil surface disturbance caused by stump harvesting and how much biomass is removed from a stand in stump harvesting.
Finland has a long tradition of utilizing forest-based biomass for energy and industry purposes and the use has steadily increased in the past decade due to changes in international and regional energy policies. Intensive harvesting practices, in which a larger proportion of the woody biomass is removed from the forest stand, are becoming more common. The objectives of this study were to evaluate the spatial and temporal extent of soil surface disturbance caused by stump-root system harvesting and to quantify how much biomass and nitrogen is removed from the stand in stump and coarse root harvesting. The extent of surface disturbance was assessed in three clear-cut Norway spruce stands in southern and central Finland, differing in time since harvest. To determine the biomass distribution of the stump-root system, stumps and coarse roots were excavated at one of the experimental stands. Across all age classes (time since harvest) less soil surface had remained undisturbed at the stump harvesting sites (52%) than at the sites where only mechanical site preparation (28%) had been carried out. Thus, the findings of this study indicate that soil disturbance caused by stump harvesting can exist on forest soil surface for more than a decade following harvest. The total biomass of the stump-root system in the stand was estimated to 39.3 Mg ha−1 and 79% of this biomass was removed during stump harvesting and consequently, 8.3 Mg ha−1 of stump-root biomass remained in soil. The stump-root system accounted for 17% of the whole-tree biomass, and coarse roots and fine coarse roots represented a significant portion of it (73%). Thus, the stump-root system represents a large biomass component in boreal forest stands. However, forest management utilizing stumps may result in carbon losses from the stand. Download the article here: https://www.sciencedirect.com/science/article/pii/S0378112718304432
Coworkers: Sofie Hellsten
Report number: A2331
Authors: Sofie Hellsten, Kaarakka, L., Vaittinen, J., Marjanen, M., Kukkola, M., Saarsalmi, A., Palviainen, M., Helmisaari, H.-S.
Published in: Forest Ecology and Management, V 425, 27-34