Root biomass and underground C and N storage of primitive Korean pine and broad-leaved climax forest in Changbai Mountains at its different succession stages Community characteristics of main vegetation types along two altitudinal transects on mountains of northwestern Beijing, China Estimation of leaf area index of secondary Betula platyphylla forest in Xiaoxing‘an Mountains Distribution characters of fine root of artificial Pinus tabulaeformis and natural Betula platyphylla forests and their relation to soil nutrients in Hilly Loess Regions Photosynthetic Physiological and Ecological Characteristics of Betula platyphylla-Quercus liaotungensis Mixed Forests in Ziwuling Forest Area