Litter-fall in a Pinus radiata forest: the effect of irrigation and fertilizer treatments.

A 15 yr-old Pinus radiata plantation near Sale, Victoria, Australia, was irrigated with waste-water for 3 yr. A litter-fall of 400 g m^-2 yr^-1 was recorded in irrigated plots compared with 320 g m^-2 yr^-1 in non-irrigated plots. The increase in litter-fall resulted from an increase in the production of new needles and greater shedding of older needles. Periods of soil water deficit caused increased shedding of needles in both irrigated and non-irrigated plots. Irrigation with waste-water increased the concentration and amounts of most elements in the litter-fall which were present in the waste-water. Increasing stress during spring and summer caused abscission of mature needles to occur more rapidly and higher in the crown, resulting in higher concentrations of N, P and K in falling litter. Male strobili contained very low concentrations of Ca and a sharp reduction in the concentration of this element occurred in litter-fall when strobili where shed in spring. Seasonal patterns observed in the concentrations of N, P and K in litter- fall were the reverse of those found in living foliage. -from Authors