The root systems of 48 perennial plants, representing nine species from the Rock Valley area within the northern Mojave Desert, were excavated by 10 cm depth increments to determine, by depth of soil, the distribution of roots larger than about 1/2 mm diameter. The depth of the root zone of all species was relatively shallow and obviously limited by depth of penetration of precipitation (about 10 cm mean annual rainfall).
There were species differences, however, in distribution of roots. Even though a sizeable proportion of the root systems was in the first 10 cm of soil, this portion consisted largely of multiple woody tap roots with relatively few small roots. In all cases except one (Krameria parvifolia Benth), more small roots were in the second 10 cm than in the first. From 50 to more than 80 percent of the total root systems were in the first 20 cm. In most cases the majority of small roots was found between 10 and 30 cm in depth. Very fine roots were sampled separately by depth and zone without regard for species because they could not be differentiated by species. Relative depth distribution of very fine roots at Rock Valley for 0–10, 10–20, and 20–30 cm, was about 17, 42, and 41 percent, respectively. The total for the first 20 cm was 59 percent. On a 22 April date, there were 225 kg/ha roots from winter annuals in the Rock Valley area; 19 percent of them were in the first 5 cm of soil in contrast to 8 percent in 10 cm of soil for perennials. On Pahute Mesa located in the southern Great Basin desert area of the Nevada Test Site in Artemisia tridentata Nutt. var. tridentata, 8 percent of the roots was in the first 5 cm, indicating more shallow rooting compared with the northern Mojave Desert.
Wallace, A.; Romney, E. M.; and Cha, J. W.
"Depth distribution of roots of some perennial plants in the Nevada Test Site Area of the northern Mojave Desert,"
Great Basin Naturalist Memoirs: Vol. 4
, Article 28.
Available at: http://scholarsarchive.byu.edu/gbnm/vol4/iss1/28