Amounts and nutrient weights in litterfall, and their annual cycles, from a series of fertilizer experiments on pole-stage Sitka spruce

abonos npk azote calcio calcium climatic factors cycling degradation engrais npk facteur climatique forest litter forest plantations fosforo growth rate hojarasca forestal humus magnesio magnesium nitrogen npk fertilizers nutrientes nutrients phosphore phosphorus picea sitchensis potasio potassium reino unido seasonal variation site factors soil organic matter substance nutritive taux de croissance united kingdom volume volumen