California Forests and Woodlands: A Natural History
222
California Forests and Woodlands: A Natural History
222Paperback(First Edition)
-
PICK UP IN STORECheck Availability at Nearby Stores
Available within 2 business hours
Related collections and offers
Overview
Product Details
| ISBN-13: | 9780520202481 |
|---|---|
| Publisher: | University of California Press |
| Publication date: | 06/16/1996 |
| Series: | California Natural History Guides , #58 |
| Edition description: | First Edition |
| Pages: | 222 |
| Sales rank: | 351,426 |
| Product dimensions: | 6.25(w) x 9.25(h) x 0.70(d) |
About the Author
Read an Excerpt
California Forests and Woodlands
A Natural HistoryBy Verna R. Johnston
The University of California Press
Copyright © 1994 Regents of the University of CaliforniaAll right reserved.
ISBN: 0-520-20248-1
Chapter One
Subalpine Forests* * * Backpackers hiking California's high, scenic trails often feel as close to paradise as they will ever be. Wandering among the rocky forested basins, lush meadows, and sparkling lakes at timberline opens top-of-the-world views. With snow-capped peaks above, wild-flower gardens in the seepages, and marmots sunning on the boulders, life can seem wondrously serene.
These delights on a congenial August day tell only part of the story. Harsh environmental conditions prevail in this zone most of the year. The Subalpine Forests that live at timberline, where trees straggle to their upper limits, climb there through a land ruled by rock and weather. Massive granite slabs, many polished to mirror brilliance by glaciers, hold large erratic boulders stranded eons ago by that same moving ice. Talus slopes of jumbled rock rise to rugged crests. In many areas, the only soil hugs tiny pockets in rock crevices. Fierce winds pick up the shallow, coarse, decomposing granite and blast off the windward sides of trees on exposed ridges. In a winter that may last ten months, temperatures range from roasting to below freezing, with frost possible any night of theyear. The only available water is from winter snowmelt, save for an occasional summer thunder shower. Solar radiation is intense.
Not many plants or animals can handle such extreme environmental conditions. The species that succeed have evolved special adaptations to subalpine rigors over time. The ways in which they combat the elements and spread their progeny over this beautiful but relentless landscape make a remarkable story.
California's subalpine domain covers roughly 8,000 to 11,000 foot elevations (2,400 to 3,300 m), with variations in species, as usual, in different parts of the state. The extensive Subalpine Forests of the Sierra Nevada, which lie just below the summits along 200 miles of the central and southern part of the range, will serve as our model of subalpine ecology, from which to explore briefly subalpine areas of California's Cascades and Warner and Klamath Mountains. The drier subalpine heights of southern California's mountains merit separate coverage, as do the inimitable subalpine Bristlecone Pine Forests of eastern California's White Mountains.
Whitebark Pine and Associates
The Whitebark Pine (Pinus albicaulis) is the most characteristic treeline conifer in the Cascades, Warner Mountains, and Sierra Nevada. In the Cascades, Whitebark Pines share timberline with Mountain Hemlocks (Tsuga mertensiana) and Shasta Red Fir on Mount Shasta. They also grow commonly on the high ridges of Lassen Volcanic National Park above a Mountain Hemlock zone and occur in scattered stands on several nearby Cascade summits. The Warner Mountains of northeastern California hold just one peak rising to tree limits, Eagle Peak, at 10,000 feet (3,000 m), which support bands of Whitebarks. In the Klamath Mountains of northwestern California, Whitebark Pines form open woodlands of dwarfed trees above high mountain meadows.
By far, the majority of Whitebark Pines in the state live in the Sierra Nevada. From the Tahoe region south to Mount Whitney, they cover an extensive high mountain realm. Growing as widely spaced trees on protected slopes, they stand 30 to 40 feet tall (9 to 12 m) with rounded crowns, silvery white barks, clustered needles (five to a bundle) at the ends of exceedingly flexible branches. Elsewhere, they form thickets, with multiple trunks sheltering resting hollows of White-tailed Jackrabbits, Mule Deer, and Bighorn Sheep (Ovis canadensis). Their knee-high elfinwood mats, often thick enough to hold a heavy hiker, march up to the 12,000-foot level (3,600 m). The species' genetic ability to grow low and horizontally enables it to survive the gales of heights well beyond the reach of its competitors.
Mountain Hemlocks also exhibit the inborn variability essential for success in both the upper and lower reaches of the subalpine zone. In the lower stretches they form almost pure groves in north- or east-facing canyons, where snow lingers well into summer. Tall, narrowly conical trees with soft bluish green needles that look starlike from above, Mountain Hemlocks carry a slightly nodding tip and add a grace to the stately forests where they frequently associate with Red Firs and Lodgepole and Western White Pines. In the northern Sierra, hemlocks are the dominant subalpine species.
But as Mountain Hemlocks ascend the higher rockbound slopes to 1,000 feet past their regular treeline in the central and southern Sierra, they assume the form of sprawling shrubs and gnarled mats close to the ground. The powerful winds that would scour an erect tree trunk bare and knock off its crown, will ride up and over a horizontally growing mat, merely shearing its top. Trees that have evolved this low form of elfinwood (known botanically in German as krummholz, for "crooked wood") are the common survivors in mountain heights around the world.
Lodgepole Pines which occupy sunny open slopes and flats in the lower subalpine belt as full forest trees have been slow to evolve the elfinwood mode of survival. As individual Lodgepole Pines climb toward timberline, most of them retain their erect, weathered stance as far up the heights as the elements allow them to grow. However, in a few areas, these pines are showing the genetic ability to form mats.
Sierra Junipers (Juniperus occidentalis var. australis) survive both ways in subalpine terrain, as mats and as erect trees. Short, thickset, cinnamon-trunked junipers form almost the sole species spaced over miles of granite domes and rocky outposts, their roots delving into seemingly hopeless rock fissures in successful quests for water. In the shelter of large boulders, junipers spread a tough horizontal mat of tight-fitting scaly leaves, angled like a roof to deflect winds up and over. Many of their wind-polished, half-bare, silvery trunks bend to buffer the low green growth in their lee.
Growth is slow for all trees in the austere mountain heights, varying greatly with local exposure, wind abrasion, sun, and the amount of snowmelt. Junipers growing in totally unfavorable microsites have been found to produce 136 annual rings in 2 inches (5 cm) of trunk cross-section. Like fellow slow-growing subalpine trees, they attain ripe old ages of 1,000 to 2,000 years or more. The Bennett Juniper near Sonora Pass, 85 feet tall (26 m) and 14 feet in diameter (4 m), has been estimated at 3,000 years.
Whitebark Pines may live 1,000 years. John Muir counted annual rings on a shrubby Whitebark Pine that was huddled behind a boulder at treeline. The 6-inch-wide trunk (15 cm) was 426 years old.
Just a slight earth rise or hummock makes a world of difference in the microsite of a tree or wild flower. Studies show that an inclined surface facing the sun receives half again more heat and light than a level surface. The importance of this added warmth to seedlings lucky enough to germinate in such favorable spots can be immense. Inclined surfaces also influence the distribution of the lovely White Heather (Cassiope mertensiana), the yellow-throated magenta Sierra Primrose (Primula suffrutescens), the red Mountain Heather (Phyllodoce breweri) and other wild flowers scattered among the rocks and crannies of the subalpine zone.
Spreading Progeny
The conifers of the high rocky slopes disseminate their seeds in a number of different ways. Sierra Junipers produce bluish berrylike cones whose seeds will not germinate unless they have passed through a bird or mammal digestive tract. Townsend's Solitaires, Coyotes, rabbits, and Martens, among others, act as willing agents.
Hemlocks and most pines rely on the wind to disperse their winged seeds, which are kept tightly sealed in cones until maturity. Whitebark Pine seeds are wingless when they leave the cone. Ordinarily this would doom the seeds to drop beneath the mother tree, but Whitebarks have no problem spreading their progeny widely over the high country. The story behind this involves a singular relationship with a bird as much at home in the heights as the pine itself, Clark's Nutcracker (Nucifraga columbiana).
A little smaller than a crow, gray with black and white wings and a sturdy, sharp bill, Clark's Nutcrackers begin feeding on Whitebark Pines in late summer, stripping first the closed purple cones and later the dry brown ones of their seeds. They eat some of the seeds on the spot, but the majority fall into a pouch on the floor of the bird's mouth. Roughly 150 Whitebark Pine seeds can fit into the pouch. Only two nutcracker species in the world own such pouches: Clark's in North America and the Eurasian Nutcracker (Nucifraga caryocatactes) in Europe and Asia, and both use it in the same way.
With a pouchful of seeds, the bird can still call its harsh "churr" as it flies to one of its specially chosen cache sites, often across ravines or ridges up to 12 miles away. Here it jabs its long, strong bill into the soil to make holes, one at a time, bringing up the pouched seeds and inserting from one to fifteen of them about an inch (2.5 cm) into the hole. It then rakes soil or litter over the burial spot before moving on to the next hole.
Favorite cache areas are south-facing slopes and ridges that are free of snow early in the spring, making the stored seeds accessible as both winter and spring fare. Such sites are scarce, and the birds often join in communal caches.
Nutcrackers live off their cached seeds until the seed crop of the next summer and show remarkable long-term spatial memories in relocating 60 to 90 percent of the caches. Research in the Rocky Mountains and in the Sierra Nevada has indicated that the birds apparently remember certain nearby landmarks such as trees, shrubs, logs, and boulders and triangulate the angles between those and their caches. Even when snow covers some of their cues, they can retrieve seeds from beneath the snow. Nutcrackers belong to the same family as jays and crows, which are considered among the most intelligent birds.
Since nutcrackers feed themselves and their young almost entirely on pine seeds, aside from occasional forays into insects, carrion, bird nests, and juvenile Belding's Ground Squirrels, they stash huge numbers of the nuts. Nutcrackers studied in Wyoming's Rocky Mountains each cached an estimated 98,000 Whitebark Pine seeds one autumn of a prime seed year. Sierran nutcrackers regularly cache up to 30,000 seeds. Such widespread storage means thousands of cache sites for the birds to remember.
It also means that many more seeds are buried than Clark's Nutcrackers need to survive. Some of the unrecovered seeds germinate in the snowmelt of the high country summer. Eventually groves of Whitebark Pines mark the old nutcracker caching sites.
Thus the bird and the tree benefit each other in a mutually useful relationship. The nutcracker transports wingless Whitebark Pine seeds over canyons, ridges, and glacier-carved cirques, unwittingly acting as a colonizer. The pine, in turn, provides a food supply of nuts rich enough in fat and protein to nourish nutcracker adults and young most of the year.
While Clark's Nutcrackers act as the chief dispersal agents for Whitebark Pine seeds, they are "aided" by Deer Mice, chipmunks, and Douglas Squirrels, which all live at subalpine elevations and make numerous large seed caches.
Deer Mice collect seeds from open cones. Their sense of smell is so keen that they probably relocate and eat most of their stores. Chipmunks climb the trees to harvest seeds, and disseminate some of them. Many of their caches are used up during hibernation. Douglas Squirrels nip off Whitebark Pine cones en masse during late summer and store them in heaps at the base of trees. The seeds remain inside the intact cones until eaten and probably only rarely reach ground favorable for germination.
Subalpine Rock Slide Mammals
Other mammals inhabit the subalpine rock slides. The Yellow-bellied Marmot (Marmota flaviventris) digs a den under piles of boulders anywhere from the Red Fir and Jeffrey Pine Forests at lower elevations to the rock avalanche areas at timberline. Everywhere it keeps an alert eye on its surroundings from a commanding perch atop a large rock or log, whistling a sharp warning to its fellows if intruders appear. In leisure moments, it spreads its body like a pancake on the granite, soaking up the sun.
The heavy bodied, short-legged marmot, about 2 feet long (.6 m), grizzled brown above and yellowish brown below with a mixture of black and white on the face, is the largest of the commonly visible high country rodents. Strictly a vegetarian, it grows fat during the summer months on the tender leaves and stems of grasses, wild flowers, and shrubs, as well as fruits and berries. But these short trips to minigardens within reach of its den always pose risks; predators such as Coyotes, Mountain Lions, or even rare native Red Foxes (Vulpes vulpes) may lurk nearby.
As winter approaches, the marmot retreats to its grass-lined den under the rocks. A complete hibernator, unlike bears and chipmunks, which awaken off and on during the winter, it curls up and sinks into a deep sleep. Its heartbeat drops from 100 beats a minute to four; its body temperature falls from 97\sz\F to 40\sz\F (36\sz\C to 5\sz\C); it breathes about once in 6 minutes and lives on its fat.
In other burrows among the talus slopes. Golden-mantled Ground Squirrels hibernate just as soundly. But the sprightly Pikas or Conies (Ochotona princeps), snug in their rockbound dens under the snow, move about during the winter, selecting food from the haypiles of grasses, sedges, wild flowers, pine needles, and shrubs which they collected, sun-dried, and carefully stored during the summer.
When winds blow snow away from their entrances, these little mammals emerge to nibble lichens off the exposed rocks or push through snow to nearby meadows, where they feed on the tips of plants extending above the snowline. Even when 15-foot drifts imprison them within their chambers, they occasionally issue thin, high-pitched calls from below.
Resembling roly-poly bundles of grayish tan fur, with a short head, round ears, and no visible tail, the 7-inch-long Pikas (17 cm) fit their high mountain environs to a tee. With an average body temperature of 104\sz\F (40\sz\C) and thick fur, they thrive on cold and cannot tolerate heat. A dozen species of them exist in the mountains of Asia; two kinds occur in North America, one in Alaska and one in the Sierra Nevada-Cascade chain and the Warner Mountains of northeastern California.
Continues...
Excerpted from California Forests and Woodlands by Verna R. Johnston Copyright © 1994 by Regents of the University of California. Excerpted by permission.
All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
Excerpts are provided by Dial-A-Book Inc. solely for the personal use of visitors to this web site.