The Traverse Creek Botanical Special Interest Area was established to protect a community of plants associated with the serpentine soils of the locale. Serpentine soils have high concentrations of metals like magnesium, nickel and chromium which few plant species can tolerate; these metals have an effect on soil chemistry and mineral availability. Species that do tolerate serpentine are often ecological specialists, adapted or evolved for serpentine environments.
Traverse Creek is ideal for photographers interested in both botany and time-lapse imagery. Lewisia rediviva, which is tolerant of serpentine soils and present here in quantity, will only open during the mid-day sun. Time-lapse imagery of the flowers opening and closing is possible from mid-morning to late afternoon. Conversely, the flowers of most plants of today's species are closed during the same time period. They only begin to open in the late afternoon, and then the flowers persist through the night and early morning. This is somewhat evident in my photographs, as the first image (with only one flower fully open in the mid-bottom centre) is from when I arrived on-site, and the third image is from when I left.
This species is Linanthus dichotomus, commonly known as evening-snow (Calphotos link, with more images). An annual species, it can sometimes be seen in dense stands when conditions are right, such as timely and sufficient rainfall (I believe this can occur at the Traverse Creek site, but not this year).
I should point out that the Jepson eFlora recognizes two subspecies of Linanthus dichotomus: subspecies dichotomus, which has the evening-open (or vespertine) behaviour, and Linanthus dichotomus subsp. meridanius, which has a daytime-open behaviour. Likely, this decision was in part based on the strength of the evidence from this paper: Chess, SK et al. 2008. Geographic divergence in floral morphology and scent in Linanthus dichotomus (Polemoniaceae). Am. J. Bot. 95(12):1652-9. doi: 10.3732/ajb.0800118. The scientists discovered significant differences between the scents of the two subspecies (by measuring the type and quantity of the floral volatile compounds). Compounds that typically attract nighttime moths were found in high concentrations in Linanthus dichotomus subsp. dichotomus, while Linanthus dichotomus subsp. meridanius had a suite of compounds more typically associated with attracting generalist daytime pollinators.
The El Dorado chapter of the California Native Plant Society shares more information about the Traverse Creek Botanical Special Interest Area.