Growth development and plant-soil relations in midterm silver birch (Betula pendula Roth) plantations on previous agricultural lands in hemiboreal Estonia

摘要

The first silver birch (Betula pendula Roth) plantations aimed at short-rotation forestry (SRF) management were established in Estonia in 1999 on former arable land, as experimental and demonstration areas of this novel land use and silvicultural system. Growth and plant-soil relations in such silver birch plantations have more often been studied at a young age ( 10 years), while studies covering the later stages of the rotation period are rare. We used repeated monitoring of soil properties and tree growth in 11 midterm (15-year-old) SRF silver birch plantations to evaluate: (1) growth rate and productivity, (2) impact of soil physico-chemical properties on tree growth and (3) changes in the topsoil chemistry between young and midterm plantations. Growth and yield of midterm silver birch SRF plantations exceeded the best local birch forest yield table values by a factor of about 2. The best growth was observed on former agricultural soils corresponding to Oxalis and Oxalis-Myrtillus forest site types. Available water content in the topsoil layer (0-25 cm) had a significant positive effect on the growth rate of birches, with competitively dominant and medium trees more affected. The topsoil pH(KCl) (range 3.7-7.1) level had a negative effect on growth rate, especially in suppressed trees. The A-horizon of former agricultural soils had provided sufficient nutrients to ensure high productivity of the trees. During the 13 years between the two monitorings, concentrations of the topsoil total N and available P had remained at the same level, while available K and pH(KCl) had decreased significantly.