Short-term effects of lime application on soil properties and fine-root characteristics for a 9-year-old Sitka spruce plantation growing on a deep peat soil

摘要

Short-term effects of lime application on a 9-year-old Sitka spruce (Picea sitchensis (Bong.) Carr.)) stand planted on a deep blanket peat soil were investigated. Ground limestone was applied at three rates: 7.5 (L-1), 15.0 (L-2) and 22.5 t ha(-1) (L-3) Plus a control (L-0). The peat was sampled on the first and second growing seasons after lime application. Soil properties were examined for the litter layer and three depths of the peat profile at 5 cm intervals, while fine root (<2 mm in diameter) characteristics were examined for the litter layer and top 5 cm of the peat profile. Soil water pH and minerals were determined for the second growing season only. Liming decreased the concentration of N in the litter layer and top 10 cm of the peat profile at the first growing season. In contrast, concentration of this element in the litter layer and top 15 cm of the peat profile was increased by liming at the second growing season. Concentration of C in the liner and below-litter layers was unaffected by liming on both sampling occasions. Lime application increased the soil water pH and concentrations of P, Ca, B and NH4+-N in the soil water. Concentration of Mg in the soil water was increased by liming only for the L-2 and L-3 plots. The soil water had a high concentration of NO3--N in the L-1 plots and low concentrations of Cu and NO3--N in the L-3 plots compared with unlimed plots. Mean fine-root dry weight and length were 0.21 g l(-1) and 177 cm l(-1), respectively. Dead fine roots were present in small amounts and only in limed plots at the first growing season. Distribution of fine roots was restricted to the litter layer and the top 5 cm of the peat profile with the majority in the litter layer. Fine-root dry weight was unaffected by liming at the first growing season, but increased by 40, 93 and 127 per cent in the L-1, L-2 and L-3 plots, respectively, at the second growing season. Fine-root length in the L-1 plots was 36 per cent lower than that in the L-0 plots at the first growing season. Length of fine roots was increased by 93, 131 and 137 per cent in the L-1, L-2 and L-3 plots, respectively, at the second growing season. The L-1 Plots had a low number of long root tips (>1 cm in length) in the litter layer compared with the L-0 plots at the first growing season, while numbers of short (<1 cm in length) and long root tips were increased by liming at the second growing season. Number of root tips per fine root length (no. cm(-1)) in the litter layer and number of total root tips per root length were increased in the L-1 and L-2 plots. Concentrations of P, K, Ca and Mg in the live fine roots were increased by liming at the first growing season. Liming increased the concentration of Ca and decreased the concentrations of Mn and Al in live fine roots at the second growing season. It seems that fine-root minerals are changed by liming and Such changes are dependent on the time interval following lime application to the peat soil.