Effects of fertilization on Picea abies stands situated on drained peat soils

Norway spruce used for afforestation of drained peat soils frequently has low productivity and decay in a long-term, which could be related to soil chemical composition and nutrient status. The research aim was to elucidate the effect of PSM on new Norway spruce plantings (1st experiment) and 20-year-old spruce stands (2nd experiment) on drained peat soils by evaluating: (1) nutrient accumulation in soil-plant system, (2) soil microbiological activity, (3) health status of spruce individuals, (4) growth intensity and productivity of spruce, (5) changes in composition of vascular plant and moss species. The study was conducted at two forest (Myrtillosa turf.mel.) sites in Latvia, each consisting of two plots: control and treated with PMS (100gm-2in September 2007, 50gm-2in April 2008). During 2008–2016, regular analysis of soil, spruce needles, soil microbiology, assessment of tree crown vitality, stand productivity, inventory of vascular plant and moss species were done. The results showed that the fertilization with PMS resulted in a significantly improved K, Ca, Zn, and N status of trees, crown vitality and up to three times increased tree growth parameters at both experiments during the study period. The average count of bacteria and fungi in soil of fertilized plots, accompanied by a remarkable variability in the study years, was significantly higher only for the 1stexperiment. Fungi: bacteria ratio for the fertilized and control plots differed significantly only for the 1stexperiment. Significant increase of cover with nitrophilic plant (Urtica dioica, Antriscus sylvestris, Rubus idaeus) and moss (Plagiomnium cuspidatum, P. ellipticum) species at both fertilized sites were stated.