Great Basin Naturalist Memoirs


Soil profiles underneath shrub clumps and bare desert pavement were examined at 62 study sites located in both open and closed drainage basins of the northern Mojave Desert. Highly significant differences occurred in the root zone underneath shrub clumps with higher concentrations of the following soil properties: electrical conductivity (EC25°), Na, K+, Ca+ +, Mg+ +, Cl-, NO3-, and SO4=; exchangeable K+; cation exchange capacity: organic C and N; available P, and DTPA-extractable Fe and Mn. These differences reflect differential cycling caused by different plant species. The decomposition and mineralization of litter deposited underneath the perennial vegetation can account for these differences in soil properties which, collectively, increase the fertility of the soil underneath the vegetation canopy. Aboveground biomass of shrubs was measured and the nitrogen and mineral element composition of new photosynthetic tissue was determined. Estimates from a representative study site indicate that the reservoir of nitrogen and mineral nutrients in new leaf material of shrubs available for litter deposition could contribute 3.64 kg N, 0.31 kg P, 0.57 kg Na, 5.20 kg K, 4.95 kg Ca, 31.82 g Fe, and 4.30 g Mn per hectare. This source probably represents about one-third of the total amount of nutrients involved in annual turnover for the study area during a normal production year. The remaining contribution would be supplied from the standing dead wood in shrubs and as litter from annual plant species.