Each year the Merced River deposits sterile silt, sand, and gravel at the south end of Washburn Lake. Grasses and sedges take root in these new accumulations and stabilize them. Then, as these plants die over the years, they add an organic component to the sediments, converting them to soil. As the soil develops here, it becomes ripe for invasion by willows, which further modify the new soil. These trap more sediments, and they add detritus to the soil, enriching it and making it more suitable for other species.
Animals also influence the development of soils and thus affect the development of vegetation.
Most of the Yosemite landscape stands above the range of the lowly earthworm, but at mid-elevations, nature has other soil processors. Foremost among these is the industrious pocket gopher, who works year-round, even in the cold of winter when other rodents are either hibernating or living off their stored cache of food. Winter is actually a safer time for the gopher to work, for it can burrow along at the base of a snowpack without danger from its summer predators-hawks, owls, gopher snakes, weasels, badgers, foxes, and coyotes. In a mountain meadow a gopher population will churn up tons of soil each year. This process has numerous benefits all leading to the development of a richer soil.