Eucalyptus urophylla root growth, stem sprouting and nutrient supply from the roots and soil

Lack of information concerning root growth of trees limits our knowledge of plant development and fertilizer response. The objective of this work was to study root growth dynamics of an E. urophylla forest after harvesting and the supply of nutrients from the roots and the soil to the new sprouts originating from the stumps. About 7-year-old eucalypt trees were felled and the sprouts and roots were sampled at 0, 60, 120, 180, 240, 330 days after harvesting. The roots were separated into fine roots (<1 mm), medium roots (1–3 mm), coarse roots (>3 mm), and taproot. Nutrient supply to sprouts from the old roots and the soil was calculated based on the change in nutrient content of the roots with time and accumulation of nutrients in the sprouts. Fine, medium and coarse root biomass increased with time after harvesting. However, the increase was more pronounced with fine roots. Between harvesting and day 60 of the new growth, all nutrients allocated to the sprouts, excluding potassium, were supplied by the soil. K was the nutrient most dependent on root reserves for the initial growth of sprouts. The contribution of the old roots to N, P, Ca, and Mg accumulation in the sprouts increased between day 60 and 120. At 330 days after harvesting, about 9.2, 23.9, and 12.6% of the N, K, and Mg, respectively, that had accumulated in the sprouts were supplied by the roots, while all P and Ca were supplied by the soil.