Fungal colonization as affected by litter depth and decomposition stage of needle litter

The present study was designated to evaluate the relative effects of litter depth and decomposition stage of needles on fungal colonization of needle litter in field experiments. The experiment was carried out in coniferous temperate forests in central Japan. Needle litter of Chamaecyparis obtusa and Pinus pentaphylla var. himekomatsu at two decomposition stages (recently dead and partly decomposed) were placed into the organic layer at two depths (on the surface of and beneath the litter layer). Fungal colonization of needles after 1 year was examined in terms of hyphal abundance and frequency of fungal species. Total and live hyphal length on needles were affected by the litter depth and (or) the decomposition stage of needles. Length of darkly pigmented hyphae on needles was 1.7–2.6 times greater beneath the litter layer than on the litter surface regardless of the decomposition stage of needles. Length of clamp-bearing hyphae in Pinus pentaphylla was 5.0–5.2 times greater in partly decomposed needles than in recently dead needles regardless of the litter depth. Frequencies of Pestalotiopsis spp. and Cladosporium cladosporioides were higher on recently dead needles than on partly decomposed needles and (or) were higher on the litter surface than beneath the litter layer. Frequencies of Trichoderma, Penicillium, and Umbelopsis species generally were higher on partly decomposed needles than on recently dead needles and were higher beneath the litter layer than on the surface.