Characteristics of nutrient biocycling of natural forests on the Gongga Mountain

Hengduan Mountains form the southeastern margin of the Qinghai-Tibetan Plateau. The main culmination is the Gongga Mountain, reaching 7 556m in western Sichuan Province. The vertical vegetation belts on the east slope of the Gongga Mountain are complete. Natural forests are distributed in altitude from 1 800m to 3 600 m. Abies fabri forest is the main vegetation type.Nutrient distribution and biocycling of natural forests on the Gongga Mountain were studied. The results showed that N,P and K storage in evergreen and deciduous broad-leaved mixed forest, Abies fabri mature and middle aged forests averaged 1 720.076, 2 103.290 and 1 748.229 kg/hm², respectively;average return by littefall was 66.577, 34.850 and 33.917 kg/(hm²·a), respectively; retention averaged 73.759, 95.387 and 81.603 kg/(hm²·a). Abies fabri forests have a stronger N, P and K retaining ability, and a lower cycling rate of N,P and K than that of evergreen and deciduous broad-leaved forests.