Small light green individual heart shaped leaves growing close to the ground.
I think this might be miner's lettuce, but the leaf shape is different and the tiny white flowers are growing on stems rather than from the center of the leaf.
(Sierra Azul; Limekiln Trail)
Claytonia perfoliata (miner's lettuce, winter purslane, or Indian lettuce; syn. Montia perfoliata) is a fleshy annual plant native to the western mountain and coastal regions of North America from southernmost Alaska and central British Columbia south to Central America, but most common in California in the Sacramento and northern San Joaquin valleys.