Plant litter was collected in traps from 8 to 10 replicates each of Ambarosia dumosa. Ephedra nevadensis, Krameria parvifolia, Larrea tridentata, Lycium andersonii, and Lycium pallidum in Rock Valley, southern Nevada, USA. Collections were made at biweekly to monthly intervals from 1975 to 1977 and handsorted into leaves, stems, flowers, and fruits. Lycium pallidum produced the most litter, with annual means ranging from 52 to 173 g per shrub. Annual means per shrub for other species ranged from 39 to 89 g (Lycium andersonii), 27 to 77 g (Larrea tridentata), 20 to 29 g (E. nevadensis), 6 to 18 g (K. parvifolia), and 3 to 21 g (A. dumosa). Litter fall was generally correlated with annual rainfall, which was low in 1975 (62 mm), high in 1976 (223 mm), and close to the long—term mean in 1977 (141 mm). Leaves were generally the largest litter category, followed by stems, fruits, and flowers. Large sample variations were found, particularly for reproductive parts. Aboveground litter fall from the six species, which comprise °82% of perennial plant biomass and °81% of shrub cover in Rock Valley, was about 117 kg/ha in 1975 and 318 kg/ha in 1976. Total aboveground litter fall for Rock Valley (all perennial and annual plants) was estimated to be 194 kg/ha in 1975 and 530 kg/ha in 1976. Distinct litter fall patterns occurred for shrub species and litter categories. Most litter fell during the summer months, with individual species peaks reflecting particular phenologies. Significant amounts of live aboveground biomass were shed as litter. Amounts of litter from the six species ranged from 7 to 83% of their respective live aboveground biomass.

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Transpirational and net photosynthetic rates of several species of desert shrubs were measured as a function of season and environmental variables at the Nevada Test Site in the northern Mojave Desert. Drought—deciduous species, Ambrosia dumosa (Grey) Payne, Lycium andersonii Grey, and Lycium pallidum Miers, had higher maximum rates and greater water loss than the evergreen, Larrea tridentata Munz, and summer green, Krameria parvifolia Benth., species. Moisture status was the most critical factor determining gas exchange rates and affected temperatre optima and acclimation as the season progressed. Because of a dry spring season, the drought—deciduous species became dormant in late May—early June: the other two species exhibited by mid—June a small positive CO₂ uptake during the morning period. Desert plant species, with few exceptions, are extremely labile and exhibit large variability and different adaptive strategies.

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