Influence of Fertilization in a Natural Populus tremula Stand

The aim of this study was to investigate productivity and wood quality of a typical natural aspen stand (Populus tremula L.) growing under varying rates of fertilizer addition in South Sweden. The stand developed from root shoots after harvest of a 40-year-old aspen stand. Fertilizer was added at rates of 0, 50, 100 and 200 kg N ha(-1) yr(-1). When the experiment started, the trees were 8 years old and until then the mean of annual stem and branch production of the control treatment was 2.8 t d.w. ha(-1). During the 3-year experimental period the production of the control was 3.2 t d.w. ha(-1) yr(-1). Fertilized treatments, however, increased in productivity up to 7.3 t d.w. ha(-1) yr(-1). Growth increase was significant (p<0.05) for all fertilized treatments. Over the whole experimental period, growth could be expressed as a linear function of the N-fertilization rate. Phosphor-fertilization did not improve growth. At the end of the experiment the stand had 2.89 trees m(-2) and then the wood density of stems and branches was 0.35 g cm(-3), and the percentage dry matter was 48 %. Wood density and percentage oven-dry matter were both higher in branches than in stems. The stem biomass averaged 88% of the above-ground wood biomass.