Sierra Nevada

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This article has been extracted from “Wild California Vanishing Lands, Vanishing Wildlife” by “Raymond F. Dasmann”. Sierra Nevada is a mountain range in the Western United States, between the Central Valley of California and the Great Basin which is well described at “Tree Removal Hayward CA

Johan Muir often referred to the Sierra Nevada as “the cathedral of light.” 
The range is an open cordillera, with extensive meadows and white granite faces planed off by past glaciers.  Originally, much of the forest on west slope facing the Central Valley consisted of enormous trees, widely spaced, with little bushy undergrowth.  The giant sequoias are best known, of course, but they were highly local in distribution, between Yosemite Sequoia National Park at mid elevations. An investigation of the spotty distribution of big trees found that they were clustered in areas plotted by Forest Service fire lookouts as being of great attraction to lightning strikes.  Presumably the lightning started frequent ground fires that exposed mineral soil required for sequoia seedlings to become established.  The lightning fires, plus those started by aborigines, maintained the open “cathedral” aspect of the forests on the western slope, consisting not only of sequoia but also of magnificent boles of yellow pine, sugar pine, and red fir.  As noted by many early visitors, brush and tree reproduction were infrequent.

Sierra Nevada
Sierra Nevada

     The higher, exposed reaches of the mountains have always been open, but the forest zone has been greatly modified.  Beginning with the Gold Rush, logging removed most of the mature timber, making way for dense stands of shrubs and young trees.  The logging slash and vigorous new growth supplied fuel for destructive wildfires of a sort rarely experienced in the primeval forest.  Subsequent effective forest fire prevention has permitted proliferation of heavy ground cover and forest reproduction, even in national parks and other areas that were not logged.  These sequential changes in woody vegetation have altered the habitat for wildlife populations occupying the Sierra forests.  The mule deer serves to illustrate the point.

     The mountain men and pioneers who explored the Sierra Nevada in the early 1800s found abundant deer in the western foothills, but relatively few deer in the upper reaches of the range or on the eastern slope.  The foothill deer were a resident population of the non migratory black-tailed race of mule deer.  They apparently thrived in the oak park lands and foothill riparian strips described so graphically by Fremont.  The migratory deer that summer in the high country and drop down to intermediate level in winter (3,000 to 5,000 feet on the western slope) were scarce because brush species needed for their winter forage were not abundant in the mature forest at that level.  However, when the forest was logged and burned, brush fields in profusion sprang up, supplying abundant and nutritious winter food on which the mi9gratory deer could thrive.  On the western slope some of the principal browse species were buck brush and deer brush (two species of Ceanothus) and mountain mahogany (Cercocarpus).  On the east slope the most important browse was bitter brush (Purshia), key winter deer food

    Persistent over-hunting kept deer populations at a low level from 1850 to about 1920, but with effective legal protection, deer proliferated rapidly thereafter to fill the niche inadvertently created for them by slash-and-burn forestry.  Migratory herds on both slopes of the Sierra reached peak levels in the 1940s; deer hunters were happy, and government wildlife agencies proudly took credit.  But ecologic balances can be notably unstable, and the sequential stages of plant succession that gave rise to good deer range advanced to engulf the browse plants in the closing canopy of a maturing young forest.  Loss of the nutritive forage plants was considerably hastened by the high numbers of deer themselves, which over browsed the most palatable species both on the winter ranges and in the high country where they migrated to rear their fawns.  Additional grazing by domestic livestock compounded the problem.  In the 1960s and 1970s deer numbers steadily declined to a level about one-third that of the peak years.

     The changes in forest cover that governed deer numbers had an equal impact on other animals.  Species such as the pileated woodpecker were very much at home in the primeval mature forest.  Snag tops of old trees offered sites for nest cavities and foraging grounds for the big birds to seek wood-boring insects.  Replacement of most of the tall timber with brush fields and young forest left scant pileated woodpecker habitat.  Similarly, p0ine martens and fishers utilized tall dense forest as one habitat component, and their numbers dropped to a very low level as a result of logging, combined with persistent over trapping.  Now the marten population is again increasing, and the fisher is reoccupying some localities in northern California.  In 1937 Joseph Grionnell reported that their larger relative the wolverine, whose home is the higher reaches of the mountains, was limited to a mere handful of survivors in the vicinity of Sequoia National Park. Protection from trapping permitted an increase in numbers and a spread of occupied range to encompass the whole Sierra Nevada and the Cascades from northwestern California on into Oregon.

Sierra Nevada
Sierra Nevada

     The beaver, which originally was practically nonexistent on the west slope of the
Sierra Nevada and was completely absent on the east slope, profited greatly by the destruction of the mature forest and the intrusion of hardwood second growth, especially aspen.  Beavers depend on foods such as aspen and willow for winter sustenance, and they responded in numbers as these plants proliferated.  Today beavers are widespread and abundant on both slopes.

     The upper reaches of the Sierra Nevada, where the wolverine again wanders, are the areas favored by backpackers and wilderness lovers.  In midsummer, when the mosquitoes have largely disappeared and the weather is consistently pleasant, the high sierra is indeed and delightful pleasure ground.  The meadows are lush green, dotted with colorful wildflowers.  Marmots bask on sunny boulders.  Chipmunks and golden-mantled ground squirrels scuttle about popular campsites, picking up crumbs dropped by previous campers.  On talus slopes the industrious pikas are curing hay and storing it deep among the rocks for winter.  Horned larks and rosy finches are feeding their newly fledged young.  And the glassy surface of a nearby lake may be dimpled by rising trout.  It is no wonder that thousands upon thousands of visitors shoulder their packs and hike into the Sierra each summer.