ABSTRACT
Perhaps the most widely studied substrate succession was the successive development of fungal strains and other decomposer organisms on the inside of pine needles, from tree foliage to humified litter. Using litter bags and moist chamber cultures, Kendrick and Burges (1962) followed the fate of Scots pine needles (
Pinus sylvestris
L.) over the course of seasons and years and recognized several well-marked steps in the fungal succession. Their study was exemplary inasmuch as they displaced studies on fungal successions from the field of mycology to that of soil ecology. From their results, it appeared that needles, as leaves (Kinkel et al., 1987), were small temporary islands, the inhabitants of which evolved together with their habitat both in space (vertical litter transfer) and time (season, year), while internal resources became progressively depleted. This scheme was reminiscent of patterns and processes observed in the successional development of plant communities by Watt (1947). Other authors described similar sequences in other pine species, pointing out the worldwide occurrence of a low number of more or less pine-specific fungal colonizers succeeding each other in a linear way (Watson et al., 1974; Mitchell and Millar, 1978b; Soma and Saitô, 1979). Other interesting results of pine studies were that the course of fungal succession was strongly influenced by (1) the start of colonization when the needle was still living (Mitchell et al., 1976; Mitchell and Millar, 1978b), (2) the nutrient status of the foliage (Lehmann and Hudson, 1977; Mitchell and Millar, 1978a), and (3) climate (Van Maanen et al., 2000; Gourbière et al., 2001), but did not seem to be affected by surface grazing of the needles (McLean et al., 1996).
