Canadell, J., R.B. Jackson, J.R. Ehleringer, H.A. Mooney, O.E. Sala, and E.-D. Schulze. 1996. A global review of rooting patterns. II. Maximum rooting depth. Oecologia 108:583-595.

The depth at which plants are able to grow roots has important implicationsfor the whole ecosystem hydrological balance, as well as for carbon andnutrient cycling. Here we summarize what we know about the maximum rootingdepth of species belonging to the major terrestrial biomes. We found 290 observations of maximumrooting depth in the literature which covered 255 woody and herbaceousspecies. Maximum rooting depth ranged from 0.3 m for some tundra speciesto 68 m for Boscia albitrunca in the central Kalahari; 196 species had roots at least 2 m deep, 50species had roots at a depth of 5 m or more, and 22 species had roots asdeep as 10 m or more. The average for the globe was 4.6±0.5 m. Maximumroot depth by biome was 2.0±0.3 m for boreal forest, 2.1±0.2 m for cropland, 9.5±2.4 m fordesert, 5.2±0.8 m for sclerophyllous shrubland and forest, 3.9±0.4 mfor temperate coniferous forest, 2.9±0.2 m for temperate deciduousforest, 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 tropicalgrassland/savanna, and 0.5±0.1 m for tundra. Grouping all the species across biomes (exceptcroplands) by three basic functional groups: trees, shrubs, and herbaceousplants, the maximum rooting depth was 7.0±1.2 m for trees, 5.1±0.8 mfor shrubs, and 2.6±0.1 m for herbaceous plants.

These data show that deep root habits are quite common in woody andherbaceous species across most of the terrestrial biomes, far deeper thanthe traditional view has held up to now. This finding has importantimplications for a better understanding of ecosystem function and its application in developing ecosystem models.