Spectral Reflectance Characteristics and Chlorophyll Content Estimation Model of _Quercus aquifolioides_ Leaves at Different Altitudes in Sejila Mountain  
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1 Key Laboratory for Silviculture and Forest Ecosystem of State Forestry Administration, Key Laboratory for Silviculture and Conservation of Ministry of Education, Research Center for Urban Forestry of Beijing Forestry University, Beijing 100083, China; [EMAIL_ADDRESS] (J.Z. ); [PERSON]SS] (H.H. ); [EMAIL_ADDRESS] (C.M.B.) 2 Chinese Academy of Forestry, Research Institute of Tropical Forestry, Guangzhou 510520, China; [EMAIL_ADDRESS] 3 Forestry College of Guangxi University, Nanning 530005, China; [EMAIL_ADDRESS] * Correspondence: [EMAIL_ADDRESS] (Q.Y. ); [EMAIL_ADDRESS] (C.X. ); Tel. : +86-010-6233-7082 (C.X.) have an important impact on the morphological structure and physiological structure of plants [3; 4; 5; 6; 7]. Therefore, in order to ensure their normal growth, plants at different altitudes have gradually formed their own adaptive mechanism to resist adversity [7; 8; 9]. Southeast Tibet is one of the largest primitive forest regions in China, and is the key research area of plateau ecosystem in China. _Quercus aquifiloides_ is a unique tree species in northwestern Yunnan, southeastern Tibet and western Sichuan, which irreplaceable in water conservation, soil and water conservation and biodiversity protection [10; 11; 12; 13]. In particular, after the \"two barriers and three belts\" (the Qinghai-Tibet plateau ecological barrier, the loess plateau-Sichuan-Yunnan ecological barrier and the northeast forest belt, the northern sand prevention belt and the southern hilly mountain belt form an overall green development ecological contour) as the main body of China's ecological security strategic pattern was put forward, the ecological barrier function and position of _Quercus aquifiloides_ in Tibet area have become increasingly prominent [14]. At present, the research on this species mainly focuses on litter decomposition characteristics, soil respiration, genetic diversity, population spatial pattern characteristics, etc. [9; 10; 11; 12; 13]. However, there is still a large gap in the research on spectral characteristics of _Quercus aquifiloides_ leaves at different altitudes. Therefore, based on the importance and particularity of the region, understanding how to monitor and quickly obtain the growth status of _Quercus aquifiloides_ in different altitude environments is the key to its ecological service function and value. In recent years, more researchers have begun to study scientific issues of agriculture and forestry, based on hyperspectral technology, with the rapid development of hyperspectral technology. Research has shown that, compared with conventional research methods, hyperspectral technology has the advantages of simple data acquisition and rich information. Spectral data contain a lot of information, such as chlorophyll content, plant stress, water content, photosynthetic rate, etc. [16; 17; 18; 19; 20]. Extracting these information through various methods can effectively solve many ecological problems. Using reflectance spectroscopy to detect the physiological and ecological characteristics of plants has gradually become one of the research hotspots in forestry remote sensing. At present, scholars have carried out a large number of researches and pioneering applications using spectral reflectance, including the correlation between plant pigments and spectral reflectance, physiological adaptation of plants to changes in altitude, adaptation countermeasures of plants to drought conditions and other harsh environments, estimation of green plant productivity, monitoring seasonal changes of plant communities, biodiversity research, detection of plant diseases and insect pests and biological invasion patterns, fire monitoring, monitoring applied to carbon cycle and water cycle, environmental pollution monitoring, etc.