Abstract
The depth at which plants are able to grow
roots has important implications for the whole ecosystem
hydrological balance, as well as for carbon and nutrient
cycling. Here we summarize what we know about the
maximum rooting depth of species belonging to the major
terrestrial biomes. We found 290 observations of maximum
rooting depth in the literature which covered 253
woody and herbaceous species. Maximum rooting depth
ranged from 0.3 m for some tundra species to 68 m for
Boscia albitrunca in the central Kalahari; 194 species had
roots at least 2 m deep, 50 species had roots at a depth of
5 m or more, and 22 species had roots as deep as 10 m or
more. The average for the globe was 4.6_+0.5 m. Maximum
rooting depth by biome was 2.0+0.3 m for boreal
forest, 2.1_+0.2 m for cropland, 9.5-+2.4 m for desert,
5.2-+0.8 m for sclerophyllous shrubland and forest,
3.9+0.4 m for temperate coniferous forest, 2.9_+0.2 m for
temperate deciduous forest, 2.6_+0.2 m for temperate
grassland, 3.7_+0.5 m for tropical deciduous forest,
7.3+2.8 m for tropical evergreen forest, 15.0_+5.4 m for
tropical grassland/savanna, and 0.5_+0.1 m for tundra.
Grouping all the species across biomes (except croplands)
by three basic functional groups: trees, shrubs, and herbaceous
plants, the maximum rooting depth was 7.0_+1.2 m for trees, 5.1-+0.8 m for shrubs, and 2.6-+0.1 m for herbaceous
plants. These data show that deep root habits are
quite common in woody and herbaceous species across
most of the terrestrial biomes, far deeper than the traditional
view has held up to now. This finding has important
implications for a better understanding of ecosystem function
and its application in developing ecosystem models.
