Abstract: Through overall survey, sampling survey and laboratory analysis, the geographical coordinates, elevation, climate, soil and vegetation of the distribution area of Thuja sutchuenensis were analyzed to reveal its habitat characteristics and their relationships. The objective was to provide basic data and theoretical basis for the effective protection of T. sutchuenensis. The results showed that: (1) The main distribution zone of T. sutchuenensis located in Southern and Southeast of China’s Daba Mountain, including Chengkou County and Kaizhou District of Chongqing City, Xuanhan County of Sichuan Province. The geographical distribution range of T. sutchuenensis was 31°25′ N—31°44′ N and 108°23′ E—108°54′ E, and its vertical distribution range was from the elevation of 700 to 2200 m. (2) The distribution area was warm and humid with the annual mean temperature of 9.98 ℃. The highest temperature and the lowest temperature were 29.1 and -7.2 ℃, respectively. Annual precipitation was 1315.2 mm, and the snow cover of the highest distribution altitude had a period of 3 months. The soil types were mountainyellowbrown soil and mountainbrown forests soil, the soil was neutral or alkalescent, and soil density and porosity were generally suitable for plant growth. (3) The zonal vegetation in the distribution zone was deciduous broad-leaved forest with evergreen broad-leaved synusia. T. sutchuenensis was mainly distributed in the warm, low mountain, deciduous and broad-leaved mixed forest area and humid, middle mountain, coniferous forest area. The main companion trees were Cyclobalanopsis jenseniana, Carpinus fargesiana, Cyclobalanpsis gracillis, Carpinus cordata var. chinensis and Quercus semecapifolia. The age structure of T. sutchuenensis population was not integrated. Seedlings and young trees with basal diameter less than 4 cm were only 25-800 plants per hectare, indicating an obvious population decline. (4) The geographical isolation of Qinling Mountain and Daba Mountain played an important role for its preservation. The strong tolerance toward drought and barrenness was an important reason for its survival and growth on the cliff edge and steep slope of the limestone area. Decentralized distribution and small population of T. sutchuenensis were closely related to its poor natural regeneration capacity and excessive disturbance of human activities.

Key words: soil moisture, litter quality, litter decomposition, sensitivity index, Korean pine forest