Effect of fertilization on the biomass production of coppiced mixed birch and willow stands on a cut-away peatland

This investigation deals with the biomass production of coppiced mixed birc h and willow stands growing on a peat cut-away area at Aitoneva, Kihnio (62 degrees 12'N, 23 degrees 18'E), Finland. The 16-year-old stands were harve sted and left to coppice for 14 years, fertilization experiment (control, P K and wood ash fertilization) with three replications was established after the clear cutting. The mother stands before clear cutting (11,000 stems pe r hectare on average) were dominated by silver birch (69% of the stem numbe r). After clear cutting the number of stems rose 7-fold to 75 500 stems ha( -1). Now the stands were dominated by Betula pubescens with 46% out of the total stem number, the share of B. pendula being only 25% and with Salix sp p 29%. At the age of 14 years self-thinning had decreased the stem number t o 12,800 stems ha(-1). The leafless biomass production of the coppiced stan ds on the control plots was lower than that of the seed originated mother s tands had been during the previous rotation. However, with fertilization th e 14-year-old coppiced stands reached the same total production as the 16-y ear-old mother stands had reached. The foliar phosphorus concentrations sho wed a severe phosphorus deficiency on the controls. Fertilization increased biomass of the stands considerably. After 14 growing seasons the above-gro und leafless dry-mass of the fertilized stands was 61.8 (PK-fertilization) and 61.4 t ha(-1) (Ash) and that of the control stands 37.6 t ha(-1). A sin gle PK fertilizer application had increased the standing biomass by 24 t ha (-1) (64%). Even though fertilization increased biomass production it did n ot increase nutrient concentrations of wood and bark, but rather decreased them. Fertilization decreased the nitrogen concentrations of leafless above -ground biomass. (C) 1999 Elsevier Science Ltd. All rights reserved.