关键词: 3S, 假林线, 海拔, 坡度, 坡向, 广东石门台国家级自然保护区

Abstract: As an important ecological boundary, the pseudo-timberline is the product of multiple environmental factors, and widely distributed in subtropical regions, but the distribution characteristics and influencing factors are poorly understood. In this paper, spatial-temporal characteristics of the pseudo-timberline in Shimentai National Nature Reserve and its adjacent areas were studied with the 3S technology according to the high resolution QuickBird images and DEM data from two phases in 2011 and 2015. The results showed that: the pseudo-timberline was distributed at altitudes between 317 m and 1 569 m, of which 80% was from 700 m to 1200 m. Considering the distribution frequency of the pseudo-timberline at different altitudes, the overall trend firstly showed an increase, then followed by a decrease with increasing altitude, and the maximum frequency was found at the altitudes from 1 000 to 1 100 m, accounting for 18.33%. Meanwhile, the average altitude of the pseudo-timberline distributed in different slopes and aspects all showed a rising trend, but it was not very significant (P>0.1). The pseudo-timberline was mainly distributed on the slopes from 5° to 35°, while few was on the flat ground of less than 2°, and the vertical slope with gradient over 55°. The highest average altitude and the maximum altitude of pseudo-timberline were both concentrated on the slopes from 5° to 15°, while the lowest values all occured on the vertical slope, and the proportion of the pseudo-timberline was only 0.03%. The altitude of timberline indicated obvious variations in different aspects of the study area (P<0.001), in which the altitude on the north slope was significantly higher than that on the south, and that on the east slightly higher than that on the west. The highest altitude of timberline was on the northwest slope while the lowest was on the south slope. As for the distribution frequency of the pseudo-timberline on different slopes, the largest was on the west slope, reaching 22.65%, while the lowest on the northeast slope, only 6%, and that on the east slope and the west slope was far greater than that on the south slope and the north slope. The habitat of the plant communities near the pseudo-timberline is special, and the environmental factors that affect its distribution are also complicated. In the future, we need to further combine the high precision remote sensing image with the ground long-term field observation, so as to further study the spatial and temporal distribution characteristics of the pseudo-timberline and its influencing factors.

Key words: 3S, pseudo-timberline, altitude, slope, aspect, the Shimentai National Nature Reserve