Litter production and nutrient return in New Zealand eucalypt short-rotation forests: implications for land management

Litter fall plays a major role in the cycling of energy and nutrients in woodland ecosystems. The amount of litter produced and nutrients returned in two population-density trials of Eucalyptus brookerana and E. saligna short rotation forests were monitored over a one-year period in Palmerston North, New Zealand. The results showed that the higher the plant density, the greater the weight of the litter fall and with higher levels of nutrients. The differences were less evident after tree canopy closure. The highest annual litter fall recorded was >10 Mg ha(-1) oven dry, of which leaves contributed over 90%. Total nitrogen and phosphorus return was up to 140 and 8.2 kg ha(-1), respectively. About 70% to 80% of the total annual litter fall occurred during summer time. To minimise depletion of nutrients from the site, trees should be harvested in autumn or winter to ensure a sustainable production system. However, to remove as many nutrients as possible in an effluent land treatment system where nutrient removal is the main objective, trees should be harvested in summer before the peak time of nutrient return. (C) 1999 Elsevier Science B.V. All rights reserved.