STUDIES ON THE DECOMPOSITION OF CONIFEROUS LEAF LITTER

Summary In a study of some aspects of the rate and type of decomposition of leaf litter of Abies grandis Lindley, Picea sitchensis (Bongard) Carrière, and Pinus sylvestris L., the external features of the needles at different stages of decay have been recorded, together with the micro‐fungi appearing on the needles and cultured from them. A regular sequence of colour changes was demonstrated, from the original green to grey‐green, brown, grey to black. Unless conditions were very favourable, the litter of Picea sitchensis changed colour much more slowly than that of the other species. The proportion of collapsed leaves increased progressively with time, although in the earlier stages of decay reversion to the non‐sunken condition could occur by water uptake. A definite succession of fungi was recorded as the litter decomposed. Needles remaining affixed to the tree were commonly colonized by Fusicoccum bacillare , accompanied on needles of Pinus by Lophodermium pinastri . On freshly fallen needles, Haplographium penicilloides, Aspergillus fumigatus , and Penicillium frequentans occurred frequently, together with white hyphal ‘cushions’ in the stomatal apertures, and a sterile net‐forming surface mycelium. Older litter was colonized by Trichoderma viride, Oidiodendron fuscum , and Verticicladium trifidum. Mucor hiemalis and Aposphaeria sp. were present throughout the period of decay, together with a number of less common species.