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. 2022 Apr 8:13:861231.
doi: 10.3389/fpls.2022.861231. eCollection 2022.

Alpine Treeline Dynamics and the Special Exposure Effect in the Hengduan Mountains

Fuyan Zou  1 , Chengyi Tu  1   2 , Dongmei Liu  3 , Chaoying Yang  1 , Wenli Wang  1 , Zhiming Zhang  1
Affiliations
Free PMC article

Alpine Treeline Dynamics and the Special Exposure Effect in the Hengduan Mountains

Fuyan Zou et al. Front Plant Sci. .
Free PMC article

Abstract

Alpine treeline is highly sensitive to climate change, but there remains a lack of research on the spatiotemporal heterogeneity of treeline and their relationships with climate change at the landscape scale. We extracted positions of alpine treeline from high-resolution Google Earth images from three periods (2000, 2010, and 2020) and analyzed the elevation patterns and dynamics of treeline positions in the Hengduan Mountains. Based on the treeline positions in 2020, a buffer zone of 300 m is established as the treeline transition zone, and the changing trend of the fraction vegetation cover (FVC) from 2000 to 2020 and its relationship with climate are also analyzed. Due to the special geographical and climatic environment, the treeline in the Hengduan Mountains area is high in the middle but lower in the surrounding areas. We found that over the past 20 years, the treeline position did not change significantly but that the FVC increased in 80.3% of the treeline areas. The increase in FVC was related to the decrease in precipitation in the growing season. The results also revealed a special exposure effect on the alpine treeline in the Hengduan Mountains. Because of the lower treeline, isotherm position caused by the monsoon climate, the treeline position on south-facing slopes is lower than that on slopes with other exposures. Our results confirmed that the pattern and dynamics of the alpine treeline are driven by the regional monsoon climate regime.

Keywords: exposure effect; fraction vegetation cover; landscape scale; the Hengduan mountains; treeline dynamics.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

FIGURE 1
FIGURE 1
Location of the studied treeline sites in Hengduan Mountains area. BSLL, Boshulaling Mountain; ML, Meili Snow Mountain; BM, Baima Snow Mountain; GZ, Gezong Snow Mountain; HB, Haba Snow Mountain; GG, Gongga Mountain; SS, Sanshen Mountain; YL, Yulong Snow Mountain; JP, Jinping Mountain.
FIGURE 2
FIGURE 2
(A) The position of treeline. (B) Extraction of treeline from Google Earth images.
FIGURE 3
FIGURE 3
(A) Variation of treeline elevation with longitude and latitude, orange lines represent treeline elevation contours; (B) average elevation of alpine treeline with different slope directions; (C) mean temperature of growing season of alpine treeline with different slope directions.
FIGURE 4
FIGURE 4
Causality test of factors affecting treeline elevation. (A) Treeline elevation; (B) the fraction vegetation cover; ρCCM represents the strength of causality.
FIGURE 5
FIGURE 5
Relationship between temperature change and treeline shift.
FIGURE 6
FIGURE 6
Spatial variation trend analysis of fraction vegetation cover on the main mountains in the Hengduan Mountains from 2000 to 2020.
FIGURE 7
FIGURE 7
Changes of the fraction vegetation cover in parts of each mountain range.
FIGURE 8
FIGURE 8
Partial correlations (Pearson’s r) between fraction vegetation cover and the two climatic variables. The intensity of colors and numbers indicate the strength of the correlation. Significant levels are: *P < 0.05; **P < 0.01.
FIGURE 9
FIGURE 9
The variation of mean temperature in growing season along the elevation gradient of treeline in different slope directions.
See this image and copyright information in PMC

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