Data from: Topography constrains the climatic response of treeline migration in Taiwan’s subalpine forests
Data files
May 08, 2026 version files 4.22 MB
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Forest_Cover_Change_KYCHEN.zip
4.01 MB
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README.md
10.41 KB
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Spatial_Regression_Analysis_KYCHEN.zip
13.85 KB
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Treeline_Position_KYCHEN.zip
186.11 KB
Abstract
Treelines are moving upslope, but the rates and drivers differ among different regions globally. Many studies have examined the relationship between treeline movement and climate change, particularly rising temperature, while the role of topographical factors has received much less attention, despite the longstanding recognition of its importance. We examined treeline dynamics from 1980 to 2021 in two mountain ranges of Taiwan, the Yushan Mountain Range (YMR) and the Central Mountain Range (CMR), in relation to topography and climate using multi-temporal aerial imagery and U-Net deep-learning segmentation. Treeline elevation advanced approximately 60 m in the two mountains and was accompanied by forest area expansion of 197 ha in the YMR and 158 ha in the CMR, which was mainly due to upward forest movement, not tree densification. Elevation, increases in growing-season temperature and minimum temperature, and growing-season precipitation were important predictors of forest area expansion. In contrast, elevation, increases in growing-season precipitation and maximum temperature, and slope steepness were key predictors of treeline movement. Treeline upslope migration was approximately two times greater during the 1980–2001 period (2.1 m yr-1 in the YMR and 1.6 m yr-1 in the CMR) compared to the 2001–2021 period (1.0 m yr-1 in the YMR and 0.75 m yr-1 in the CMR), likely because forests already occupied most of the suitable habitat, and topographic factors constrained upward movement. Our study highlights the importance of accounting for both climatic and topographic factors in understanding treeline responses to climate change. In addition, our results indicate that treeline advance in mountain island forests, such as those in Taiwan, may be approaching an elevational limit, above which further upward migration is likely to exhibit a more muted response to further warming.
Dataset DOI: 10.5061/dryad.ncjsxkt8x
Description of the data and file structure
This repository contains processed and derived datasets supporting the study “Topography constrains the climatic response of treeline migration in Taiwan’s subalpine forests.” The data describe forest cover change, treeline position, and spatial regression analyses for two high-elevation mountain regions in Taiwan: the Yushan Mountain Range and the Central Mountain Range.
The deposited files are derived data products generated by the authors from aerial photographs, climate data, topographic data, and forest resource survey data. The original aerial photographs, original TCCIP climate datasets, original digital terrain model, and original Fourth National Forest Resource Survey datasets are not redistributed in this Dryad repository.
The repository includes three main archives:
1. Forest_Cover_Change_KYCHEN.zip
2. Treeline_Position_KYCHEN.zip
3. Spatial_Regression_Analysis_KYCHEN.zip
1. Forest Cover Change
File: Forest_Cover_Change_KYCHEN.zip
This archive contains CSV files representing forest and non-forest classification data for the Yushan Mountain Range and the Central Mountain Range in 1980, 2001, and 2021. The classification was derived from multi-temporal aerial photographs using a U-Net deep-learning segmentation model, followed by checking, cleaning, and spatial processing. The original aerial photographs are not included.
Files included:
- CM__ForestCoverChange.csv: Forest/non-forest classification data for the Central Mountain Range.
- YS__ForestCoverChange.csv: Forest/non-forest classification data for the Yushan Mountain Range.
Variables:
- Forest1980: Binary forest cover classification for 1980. 1 = forest; 0 = non-forest.
- Forest2001: Binary forest cover classification for 2001. 1 = forest; 0 = non-forest.
- Forest2021: Binary forest cover classification for 2021. 1 = forest; 0 = non-forest.
- Elevation: Elevation of the sampled location, in meters above sea level.
- lon_wgs84: Longitude of the sampled location in decimal degrees, WGS 1984.
- lat_wgs84: Latitude of the sampled location in decimal degrees, WGS 1984.
Coordinate reference system:
The forest cover CSV files use longitude and latitude coordinates in the WGS 1984 geographic coordinate system.
2. Treeline Position
File: Treeline_Position_KYCHEN.zip
This archive contains treeline position data stored as ESRI shapefiles. The shapefiles represent treeline positions in the Yushan Mountain Range and the Central Mountain Range for 1980, 2001, and 2021. Treeline positions were derived from the forest/non-forest classification results generated by the authors.
Files included:
- CM_1980_Treeline_Position.shp and associated shapefile component files
- CM_2001_Treeline_Position.shp and associated shapefile component files
- CM_2021_Treeline_Position.shp and associated shapefile component files
- YS_1980_Treeline_Position.shp and associated shapefile component files
- YS_2001_Treeline_Position.shp and associated shapefile component files
- YS_2021_Treeline_Position.shp and associated shapefile component files
Each shapefile is provided with its associated component files, including .shp, .shx, .dbf, and .prj files. These files should be kept together when opening the data in GIS software.
Attribute variables:
- LEFT_FID: Internal GIS processing identifier for the feature on the left side of the treeline segment. This field was not used as an analytical variable.
- RIGHT_FID: Internal GIS processing identifier for the feature on the right side of the treeline segment. This field was not used as an analytical variable.
- Shape_Leng: Length of the treeline polyline segment, in meters.
Coordinate reference system:
The treeline shapefiles are stored in a projected TWD97 Transverse Mercator coordinate system with a central meridian of 121E and linear units in meters.
3. Spatial Regression Analysis
File: Spatial_Regression_Analysis_KYCHEN.zip
This archive contains processed analytical datasets in RDS format and R scripts used for the spatial regression analyses. The RDS files contain derived variables used to examine relationships between forest area change, treeline elevation change, climate variables, and topographic variables.
Files included:
- KYCHEN_wgs84.rds: Processed analytical dataset for the Yushan and Central Mountain Ranges.
- KYCHEN_SPregmd.R: Scripts used to conduct the regression analyses.
Variables in the RDS files:
- VarArea_ha: Forest area change response variable, in hectares.
- VarElevation: Treeline elevation change response variable, in meters.
- GP: Change in growing-season precipitation, in millimeters. The growing season was defined as May to October.
- GT: Change in growing-season mean temperature, in degrees Celsius. The growing season was defined as May to October.
- MaxT: Change in annual maximum temperature, in degrees Celsius.
- MinT: Change in annual minimum temperature, in degrees Celsius.
- Slope: Terrain slope steepness, in degrees.
- Elevation: Elevation, in meters above sea level.
- TPI: Topographic Position Index, unitless. Values near 1 indicate ridges, values near -1 indicate valleys, and values around 0 indicate relatively flat areas.
- HLI: Heat Load Index, unitless. This is an aspect-derived index representing potential incident solar radiation.
- LON_WGS84: Longitude in decimal degrees, WGS 1984.
- LAT_WGS84: Latitude in decimal degrees, WGS 1984.
Climate variables were derived from TCCIP climate data through downscaling, calculation, extraction, and random point sampling. The original TCCIP climate datasets are not redistributed here.
Topographic variables were derived from a digital terrain model. The original digital terrain model is not redistributed here.
Code/software
Forest/non-forest classification was conducted using U-Net deep-learning segmentation in ArcGIS Pro. Spatial processing was conducted using GIS software. Regression analyses were conducted in R.
Users may need GIS software or appropriate R packages to read these files. CSV files can be opened in spreadsheet software, GIS software, or R. RDS files can be read in R using readRDS(). Shapefiles can be opened in GIS software or in R using packages such as sf.
Access information
Other publicly accessible locations of the processed data:
None. The processed datasets are publicly released through this Dryad repository.
Data sources
The deposited files were derived from the following sources. The original external source datasets are not redistributed in this repository. Users who need the original source datasets should obtain them directly from the respective providers and follow the access, citation, and usage requirements specified by those providers.
1. Aerial photographs
Multi-temporal aerial photographs were obtained from the Aerial Survey and Remote Sensing Branch (ASRSB), Taiwan Image Services, Supplier, and System:
The source aerial images are not open-access and must be searched and purchased through the provider’s official platform. The original aerial photographs are not redistributed in this Dryad dataset. Only derived forest/non-forest classification data and treeline vector data generated by the authors are deposited here.
2. Climate data
Climate data were obtained from the Taiwan Climate Change Projection Information and Adaptation Knowledge Platform (TCCIP), National Science and Technology Center for Disaster Reduction:
https://tccip.ncdr.nat.gov.tw/
https://dx.doi.org/10.3390/w14030358
The original TCCIP climate datasets are not redistributed in this Dryad dataset. The deposited analytical datasets contain derived climate variables generated by the authors for this study. Users should follow the TCCIP citation and usage requirements when accessing the original data.
3. Topographic data
Topographic data were retrieved from the Ministry of the Interior's open data platform, Taiwan:
https://data.gov.tw/dataset/35430
The original topographic dataset is not redistributed in this Dryad dataset. Derived topographic variables used in the analysis are included in the processed analytical datasets.
4. Fourth National Forest Resource Survey data
Data from the Fourth National Forest Resource Survey were obtained from the Taiwan Government Open Data Platform:
https://data.gov.tw/dataset/57873
The original survey dataset is not redistributed in this Dryad dataset. It was used as a source of forest-type and grassland information during data preparation and model training.
Licensing and reuse notes
All files deposited in this Dryad dataset are processed or derived data products generated by the authors and are submitted under the CC0 waiver required by Dryad.
The original aerial photographs, original TCCIP climate datasets, original digital terrain model, and original Fourth National Forest Resource Survey datasets are not redistributed in this repository. Users who require the original source datasets should obtain them directly from the respective data providers and follow their access, citation, and usage requirements.
Notes for reuse
The forest cover CSV files contain binary forest/non-forest classifications for each sampled location and year. The treeline shapefiles contain line features representing derived treeline positions for each study area and year. The RDS files contain processed analytical datasets used for regression analyses of forest area change and treeline elevation change.
These files are intended to support reproducibility and interpretation of the analyses presented in the associated study. Users kindly cite the associated publication and this Dryad dataset when reusing the data.