| Summary: | The influence of conventional (stem only) and whole tree (all above ground biomass) harvesting on soil characteristics and second rotation Sitka spruce (<I>Pica sitchensis</I> (Bong.) Carr.) growth was investigated on a peaty soil in Kielder Forest, Northumberland. One site was intensively studied in the third and fourth years after restocking. The full factorial experiment (established by the Forestry Commission and the Macaulay Land Use Research Institute) included three treatments; retention of harvest residues (±R), herbicide application (± H) and fertiliser additions (± F), giving eight treatments which were replicated in three randomised blocks. Of the treatments, the effects of ±R, ±H and their interaction were observed. Confounding effects of soil compaction resulting from the passage of machinery were reduced by driving harvesters between treatment assessment plots. The total nutrient capital (N, P, K, Mg and Ca) and physical characteristics including bulk density, horizon depth and oven dried weight of the soil (LFH and upper O horizons) were determined annually. <I>In situ</I> mineralisation of inorganic nitrogen, fluctuations in soil moisture content, organic matter, and pH were recorded throughout the third growing season using capped corers. The vegetation (species type, biomass and nutrient content) was surveyed in August of the third growing season. Phenological and morphological characteristics measured in spruce included timing of bud flush, occurrence and length of lammas growth, duration and length of the leader extension and tree height. Foliar nutrient concentrations (N, P, K, Mg and Ca) were analysed throughout both growing seasons. At the end of the fourth growing season root depth and distribution were observed in relation to waterlogging and anaerobic soil depth. Treatments did not consistently alter soil nutrient capital or annually measured soil physical properties. Compared to - R plots, residue retention reduced seasonal fluctuations in mean soil temperatures and moisture content, especially in the litter layer. Differences were greatest in the summer when temperatures were warmer and precipitation low. Net ammonification (88 kg N ha<SUP>-1</SUP>) and total nitrogen mineralisation (90 kg N ha<SUP>-1</SUP>) during the third growing season were not significantly affected by treatment. However, significantly greater nitrate was released in the LFH horizon of + R and + RH plots (P < 0.039).
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