Dry-Season Dynamics of Soil Inorganic Nitrogen Pools in Primary Lithocarpus xylocarpus Forest and Degraded Vegetation in Ailao Mountain, Yunnan Province N Mineralization and Nitrification in a Primary Lithocarpus xylocarpus Forest and Degraded Vegetation in the Ailao Mountain, Yunnan Province STUDY ON THE ACCUMULATION AND BIOLOGICAL CYCLES OF CHEMICAL ELEMENTS IN LITHOCARPUS XYLOCARPUS FOREST IN NORTH SIDE OF AILAO MOUNTAIN