Wednesday, April 19, 2017

Wildflowers of the Sierra Nevada Foothills: Red Hills Area of Critical Environmental Concern

Red Hills Area of Critical Environmental Concern: a big name for a special place in the Sierra Nevada Foothills.  Markedly different from surrounding areas and supporting a unique assemblage of species, this area is considered a biological or ecological island.

Bitter root (Lewisia rediviva)

Driving past the Red Hills area on highway 108/120 west of the junction with highway 49, observant motorists will notice a striking difference between the grassy, oak-dotted hills that provide rangeland for grazing cattle, and the sparsely vegetated rocky terrain of the Red Hills. 

Buckbrush and Gray Pine cover Red Hills

The inhospitable soil of Red Hills excludes the annual (and exotic) grasses of surrounding areas and instead supports an assemblage of scraggly-looking gray plants, including Gray Pine (Pinus sabiniana) and Buck Brush (Ceanothus cuneatus), with an understory of herbaceous plants which put on a striking and unexpected wildflower show in the spring. 

In the spring, Goldfields (Lasthenia californica) carpet the ground at Red Hills.

The difference between the grassy oak savannahs and scrubby Red Hills, one might guess immediately, is a product of geology.

Five Spot (Nemophila maculata)

Most people probably immediately link that precious mineral gold to the Sierra Nevada foothill region, otherwise known as the Mother Lode.  But what many don't realize, is that tucked along the base of the Sierra Nevada mountains is a belt of metamorphic rock - slate, marble and the like - which includes a fair amount of California's state rock, serpentine.  Serpentine rocks and the soils derived from them underlie the unique landscape of Red Hills.

Bird's Eye Gilia (Gilia tricolor) - one of my favorite!  Notice the blue pollen on the anthers - a unique feature of gilias.

To understand the origin of these metamorphic rocks, one must travel back through millions of years of geologic history.  Between 544 and 65 million years ago (during the Paleozoic and Mesozoic eras), subduction was occurring along the western edge of the North American continent as plates converged.  As material from the seafloor, limestone reefs and even parts of oceanic crust was scraped up and "smashed" against the edge of the continent, intense heat and pressure metamorphosed or transformed this material into metamorphic rocks.  Differing occurrences of various minerals account for different types of rock.  For example, rocks from the earth's mantel, which have large amounts of the mineral olivine, form the rock serpentine. 

Bolander's Linanthus (Leptosiphon bolanderi) characteristically shows a slight affinity for serpentine soils.

The Red Hills area includes a large portion of the Tuolumne complex of ultramafic rocks, metamorphic rocks that are unusually high in magnesium and iron, as well as nickel, chromium and cobalt.  These minerals are not conducive to the growth of vegetation (magnesium, for one, causes calcium deficiency in plants); in high enough doses, they are toxic to plants.  Coupled with low amounts of the basic nutrients plants require (nitrogen, phosphorus, potassium), these serpentine soils create inhospitable growing conditions. 

Ithuriel's Spear (Triteleia laxa) is endemic (limited) to California.

 Yet, remarkably, life will always find a way, and a small handful of plants, often referred to as serpentine endemics, have adapted to grow and even thrive in these impoverished soils.  Gray Pine and Buck Brush, while present in other areas, seem oblivious to the unfavorable conditions of serpentine soils, and flourish where other foothill species cannot.  Several plants occur only in the Red Hills area and surrounding Tuolumne County, such as California Verbena (Verbena californica) and Rawhide Hill Onion (Allium tuolumnense).

Blue-eyed Grass (Sisyrinchium bellum)

The first time I visited Red Hills ACEC was on a field trip for a botany class I took at CSU Stanislaus; the second and third visit were also for field trips in other botany classes!  But there is clearly a reason this place holds such appeal for botanists, with its unique assemblage of species found nowhere else sprinkled amongst more widespread species that have managed to eke out existences in an otherwise unfriendly landscape. 

Shooting Star (Primula sp.)

Much like our desert regions, the Red Hills area has been neglected over the years: it was "unproductive" from an agricultural as well as mining standpoint, useful for little else besides a dumping ground and place to recklessly drive off-highway vehicles.  Thankfully, since the early 1990's it has been protected by the federal government and this valuable ecological island will be preserved.

Showy Red Sierra Onion (Allium obtusum)

Spring is undoubtedly the time to visit Red Hills: the creeks are running (in wet years), the wildflowers are blooming.  Goldfields color the otherwise gray hillsides, and it seems everywhere one looks, delicate blooms can be found hiding among rocky outcroppings.

Cream Cups (Platystemon californicus)

About 17 miles of looping trails wind throughout the area, providing ample opportunities for the hiker and the equestrian... during the winter and spring months.  (Conditions become quite desert-like during the long, hot, dry stretch of summer and fall.)  I highly recommend bringing a trail map with you, as trail markers are not always dependable.  A map can be accessed through the Bureau of Land Management's website:

Purple Mouse Ears or Douglas' Monkey Flower (Mimulus douglasii) is a miniscule flower
(the whole plants stands a proud 2 - 3 inches tall) with an affinity for serpentine soils.

For more information on the geology of the Mother Lode region (much, much more information) a geologic guide book titled "Roadside Geology and Mining History of the Mother Lode" is available in PDF form through the Bureau of Land Management, and can be accessed through their website.

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