Abstract:

Litterfall and nutrient return patterns were studied in three successional stages of Abies fabri forests on the east slope of Gongga Mountain. The rate of litterfall showed an increasing trend while succession proceeded. The seasonality of litterfall of Abies fabri mature and young forests was unimodal, with a distinct peak in October and a lean period from May to June, while the seasonality of litterfall of Abies fabri middle age forest was a binomial curve, with peaks in May and October. Annual litterfall of mature, middle age and young forests averaged 2 809.925, 2 787.086, and 2 043.585 kg·hm-2·a-1, respectively. Leaf litter constituted 72.79%-77.66％of annual litterfall in all three forests. In all forests, the miscellaneous fraction made only a very small contribution 23%-3.54％) to the total litter production. The lichen and moss fraction also made a contribution (1.62%-5.19％) to the total litter production; this is an obvious feature of Abies fabri forest. Nutrient concentrations varied significantly between forests and litter fractions. Nutrient (N) concentrations were highest in the leaf litter, but litter concentration of mineral elements was lower than that of fresh foliage, due to resorption during senescence. The rate of N, P and K mass in the leaf that was resorbed during senescence showed an increasing trend in the order: middle age forest >mature forest > young forest. Nutrient (N, P, K) returns of the mature, middle age and young forests were 34.850, 33.917, and 42.571 kg·hm-2·a-1, respectively. There are many differences of the litterfall and nutrient return patterns between Abies fabriforests and other types of conifer forests in China, but there also exist some similarities with Abies forests in the Northwest of America.