classify_above_treeline {ElevDistr}

Classify points as above or below the treeline

Description

Calculates if the points (from the input data frame coords) are above the treeline (TRUE) or not (FALSE). This is achieved by using climate layers for growing season length and growing season temperature. For each coordinate a value from both rasters is extracted and added to the input data frame. Then points are classified, the default thresholds and the treeline definition is based on Paulsen and Körner, Alp. Bot. 124: 1-12 (2014). Classification (as boolean) is also added to the output.

Usage

classify_above_treeline(coords, gstRaster, gslRaster, gstTreshold = 6.4,
                              gslTreshold = 94)

Arguments

coords

Data frame representing coordinates (WGS 84) to be classified. The first column must contain the longitude, the second the latitude, both in decimal degrees. The values must be of the data type "numeric" and finite. A data frame can be generated by using the function generate_grid.

gstRaster

Climatic raster that contains the growing season temperature. Data type "SpatRaster".

gslRaster

Climatic raster that contains the growing season length. Data type "SpatRaster".

gstTreshold

Growing season temperature threshold for tree growth (in degree Celsius). One value, data type "numeric" and finite.

gslTreshold

Growing season length threshold for tree growth (days). One value, data type "integer" and finite.

Value

A data frame containing: longitude, latitude, growing season temperature, growing season length, and a boolean. The boolean indicates if the point is above the treeline.

Author(s)

Livio Bätscher, Jurriaan M. de Vos

Examples

#Get raster layer from CHELSA
gstURL <- paste0("https://os.zhdk.cloud.switch.ch/envicloud/chelsa/chelsa_V2/",
                 "GLOBAL/climatologies/1981-2010/bio/CHELSA_gst_1981-2010_V.2.1.tif")
gslURL <- paste0("https://os.zhdk.cloud.switch.ch/envicloud/chelsa/chelsa_V2/",
                 "GLOBAL/climatologies/1981-2010/bio/CHELSA_gsl_1981-2010_V.2.1.tif")

gst <- terra::rast(gstURL, vsi = TRUE)
gsl <- terra::rast(gslURL, vsi = TRUE)

#Classify a single point
point <- data.frame("lon" = 8.65, "lat" = 46.87)
classify_above_treeline(coords = point, gstRaster = gst, gslRaster = gsl,
                        gstTreshold = 6.4, gslTreshold = 94)

#Classify a dummy data frame
longitude <- rep(8.53, 11)
latitude <- seq(46.8, 46.9, 0.01)
temp <- data.frame(longitude, latitude)
classify_above_treeline(coords = temp, gstRaster = gst, gslRaster = gsl,
                        gstTreshold = 6.4, gslTreshold = 94)