noun. A line on a map, chart, or graph connecting points of equal value.

noun. Any of several types of line on a map, chart or graph that link points having the same value of a parameter

"Major climate-related species distributions at the large scale include the limit of trees, which is associated with the isoline for mean July air temperatures of about 10 °C [3] (as discussed in [4]) and soil temperature of 7 °C [5], and the limit of woody plants such as dwarf shrubs that are one indicator of the boundary of the polar desert biome [6]."

isopleth