Effects on soil characteristics by different management regimes with root sucker generated hybrid aspen (Populus tremula L. × P. tremuloides Michx.) on abandoned agricultural land

Abstract

Abstract: Fast-growing Populus species are becoming frequently used at afforestation of arable land globally and hybrid aspen is promising for short rotation forestry in the northern hemisphere. Knowledge about growth performance of the second-generation plantations, i.e., consisting of root sucker generated shoots after clearcutting of the original stand, is increasing, but less information is available on the effects on soil properties, especially with varying management. We followed the soil effects of three different management regimes, including 4-, 8- and 16-year rotations with thinning measures in the two longer rotations, in root sucker generated hybrid aspen on former agricultural land. The study was performed in a randomized block design and changes in soil variables were estimated by repeated sampling, i.e., at root sucker initiation and after eight years. Concentrations and pools of soil organic carbon (SOC) and soil nutrients, pH and bulk density were analysed in the 0-15 and 15-30 cm mineral soil. Common for all management regimes were unchanged SOC and nutrient pools; pH and bulk density were also unaffected during the study period. Afforestation effects on the vertical distribution of nutrients, i.e., redistribution of NH4-N, K and Mg from deeper to shallower soil by plant uptake and release through litter decomposition, were observed in all management regimes. A different effect was noted for NO3-N where a declining trend was observed. This could indicate a leakage of the ion, but NO3-N distributions in soils are variable which makes interpretations difficult. The results suggest that different management strategies have small initial effects on mineral soil characteristics. However, soil changes need to be followed for an extended period to get more information on the long-term impact of afforestation and management of root sucker generated stands.