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Plants
Plants surround us, shelter us, feed us, and form the aesthetic and functional backdrop to our lives. Were it not for green plants, there would be no life as we know it on Earth. Despite their central importance to our lives, many of us are no more aware of the plants we live among than we are of billboards. Ask yourself these simple botanical Jeopardy questions: How many trees can you name on sight? What is the first bush to bloom in your yard each spring? Are the conifer trees on Mt. Lassen the same species as those you can find in the Sierra Nevada? Are they the same species as the trees in the mountains above Los Angeles?
Plants can be categorized into various groups or sets that share characteristics, life style traits, and adaptations to their environment. This chapter starts with huge generalities about all plants and gradually focuses in on specific traits of some of the important plants of California.
LIFESTYLES OF RICH AND FAMOUS PLANTS
Warm and wet conditions promote the growth of plants. Cool, cold, and dry conditions cause plants to slow down metabolically. Thus tropical rainforests are “ideal” spots for plants to grow. Most of the world, however, is not a tropical rainforest, so the story of plant adaptation is the story of the development of alternative lifestyles to cope with the diverse deviations from ideal climate conditions that the majority of the world presents.
Conifer trees in front of the Mt. Lassen volcano. Photo by Kerry Heise
Some plants live for a few months, others for many years. Indeed, the longest-lived organisms on Earth are plants. One species of Mediterranean sea grass (Posidonia oceanica) is one of the slowest-growing and longest-lived plants in existence, with some large clones estimated to be thousands of years old. Trees are perhaps the most familiar, archetypal plants. Trees generally grow from seeds, starting out as collections of a few cells and enlarging to become the most massive and the tallest organisms on Earth. Trees are said to be both perennial and woody. Perennial plants are those that live more than one year and generally pass an unfavorable season in a dormant or inactive state.
Trees can also be divided into those that are deciduous and those that are evergreen. Deciduous trees and shrubs lose their leaves during the unfavorable season, whereas evergreen trees and shrubs keep individual leaves for more than one growing season, and may be photosynthetically active during the unfavorable period.
Shrubs are another type of woody plant. They generally have more than one stem, whereas trees classically have only one main trunk. Shrubs generally keep to below 15 feet tall; trees are often much larger. Is the 25-foot-tall, single-trunked rhododendron in your neighbor’s yard a tree or a shrub? Exceptions to these rules abound, so shrub and tree are general terms without precise distinctions.
The last category of woody plants of relevance to California naturalists is lianas, or woody vines. Most plants desire to maximize their exposure to sunlight. Essentially, they compete for sunlight. Trees compete by putting huge allocations of resources into growing a stem that allows them to overtop other plants. Lianas are cheaters: they utilize the structure of trees and shrubs to get to the canopy without making the investment in a large stem. There are four genera of lianas that are common in California: poison oak (Toxicodendron), wild grape (Vitis), honeysuckle (Lonicera), and virgin’s bower (Clematis). These four plant genera illustrate the three mechanisms lianas use to climb: twining, tendrils, and adventitious roots. Honeysuckle stems wrap around the stem they climb: they twine. Poison oak can climb tree trunks or bare walls using sucker-like roots: adventitious roots. Grapes use the grappling hooks of the plant world: tendrils.
Annual plants are distinct from perennials in that they complete their life cycle in one growing season. They pass the unfavorable season as a seed. Those of you who have grown tomatoes from seed will be familiar with the concept. Tomatoes have an annual lifestyle: one good growing season and leave behind seeds. Such well-known spring wildflowers as Chinese houses (Collinsia), baby blue eyes (Nemophila), and popcorn flower (Plagiobothrys) are annuals, as are many of the plants that grow wild in the hills of California.
The California poppy is a familiar wildflower. Poppies are herbaceous (nonwoody) plants and they have a little secret: they grow as both annuals and herbaceous perennials! In favorable circumstances they switch from being an annual to being an herbaceous perennial. At the close of the favorable season, poppies may translocate carbon compounds and minerals to their roots. At the return of the favorable season, they may begin to grow once again, powered by the energy and nutrients stored in the roots, rather than starting from a seed. This phoenix-like rebirth driven by stored reserves is a major class of adaptation of California plants, referred to as the herbaceous perennial lifestyle. Examples of other plants with this lifestyle that may be familiar to you are soap root (Chlorogalum), blue dicks (Dichelostemma), and mule ears (Wyethia). Trees and shrubs are easy to tell from herbaceous plants. Annuals and perennials are more difficult to distinguish. Often you will need to expose the root or follow the plant’s growth over the course of a year to distinguish an annual from a perennial.
The stored energy in a mariposa lily (Calochortus) bulb or a snake-root (Sanicula) tuber allows it to produce leaves much more quickly than the seed of an annual poppy, which must start from scratch to build a plant body by photosynthesis. Thus herbaceous perennials can overtop and exclude annuals in stable, predictable environments, like woodlands and shrublands. But in open and disturbed environments, annuals come into their own, playing on their ability to produce numerous seeds. Human activity, in maintaining many open and disturbed environments, has created a bonanza for annuals.
PARTS OF A PLANT
Plants grow by making stems. In order for a plant to produce a leaf, it must make a stem. Some stems are very contracted (think of a cactus), others more elongate and easily visible, but all plants must make stems to produce leaves. Leaves are usually the primary locality of photosynthesis, thus it behooves plants to make leaves. As the stem elongates, leaves are produced sequentially, from the near end of the stem out to the tip. At the base of each leaf is a remarkable structure, a bud. A bud is a clump of tissue specialized to be ready to grow a new stem, leaf, or flower. Buds are often visible at the base of the leaf. The easiest time to see buds on deciduous plants is during the dormant season. Often buds in this season are enlarged and prominent, but even during the growing season and on evergreen plants, buds are often discernible. Buds consist of the tissue that will become the new stem, leaf, or flower, surrounded and protected by one or many bracts or scales. The bracts and scales are evolutionarily modified leaves. They enclose the dormant bud tissue and protect it from weather extremes (cold, dry) and predators. When the new stem begins to grow, the bud scales relax and open to allow the new stem to elongate. Typically they fall from the plant and may be noticeable on the ground, or the bud scale scars they leave upon dropping may be visible or prominent on the stem.
As stems elongate, they produce successive leaves along their length. Leaves come in a startling variety of shapes and sizes and are arranged upon the stem in typical patterns. Leaves may be arrayed along a stem in alternate, opposite, or whorled fashion. The leaves themselves may be simple (undivided) or compound (divided). Leaves can also be very thin — needles are in fact a kind of leaf!
Flowers can be thought of as variations on a theme. The theme is four whorls of modified leaves, the sepals, petals, stamens, and pistil.
Flower buds of wild lilac (Ceanothus). Buds are condensed tissue ready to expand when the growing season begins. Photo by Lynn Watson, Santa Barbara
Forms of leaves. From left to right: bigleaf maple (Acer macrophyllum), simple leaf deeply palmately lobed; Pacific bleeding heart (Dicentra formosa), three-part compound leaf, deeply dissected; oceanspray (Holodiscus discolor), leaves simple, alternate, and toothed; snowberry (Symphoricarpos albus var. laevigatus), leaves simple, opposite, and toothed at all margins. Photo by Kerry Heise
Parts of a flower. The critical parts every naturalist must be able to recognize are the sepals, petals, stamens, and pistil. Courtesy of Mariana Ruiz Villarreal
Very generally, the function of the sepals is to enclose and protect the inner parts: the petals, stamens, and pistil. Petals are the often highly colored part of the flower that signals to potential pollinators that “there may be a reward here, please investigate” and can be thought of as a kind of advertising. The stamens are the functionally “male” part; they are the site of pollen production. The pistil is the functionally “female” part, largely characterized by an ovary within which the seeds develop.
The function of flowers is to produce seeds. The function of seeds is to allow the plant to have progeny both locally and distantly. The intermediate step between flowers and seeds is the fruit. Fruits are the enlarged, mature ovaries that were present in the flower. Fruits come in a bewildering array of shapes and sizes, from tiny orchid fruits an inch long with 25,000 seeds to the baseball-sized fruits of the buckeye (Aesculus) with only one seed. The unifying theme is that all fruits are ripened ovaries.
Because plants have had millions of years to try different strategies for success (about 65 million in the case of flowering plants), many different solutions to the mechanics of seed production have evolved. Every type of flower you see today has a unique, ancient lineage. The result is a bewildering array of different-looking flowers (about 250,000 kinds on Earth today). In some plants the sepals and petals are just alike and are called tepals (many lilies). Different parts of the plant may be modified to produce nectar: the leaves (Prunus), petals (Ranunculus, Aquilegia), sepals (Ipomoea), stamens (Viola), or base of the pistil.
What this means is that every flower in your garden or your local park is a mystery waiting for you to investigate it. Try dissecting a flower. Perhaps you’ll start with a California poppy. Look for the sepals, petals, stamens, and pistil. Try to find an old poppy flower that has dropped its sepals, petals, and stamens, to see what the ovary looks like as the seeds develop.
Pollination
Functionally, producing seeds is the name of the game. To reproduce, plants need to put “male” and “female” parts together. That is, they must unite pollen with ovaries. For maximum effectiveness (that is, for the best rearrangement of genetic material), it is best to mate with another individual, not with yourself. (Yes! Plants have the option to mate with themselves!) Most plants attempt not to mate with themselves; they try to promote outcrossing. One of the best methods plants have developed to ensure outcrossing is to use animals to carry pollen from one plant to another. This system is a typical business deal, with payments (rewards) for services rendered, advertisement, and competition. Think of a bumblebee hovering around a manzanita (Arctostaphylos) flower in January. Why should it? For the reward. Manzanitas pay bumblebees with sugar water (nectar). Some flowers pay in nectar, others pay in pollen, a very few pay in oils, but there is no free lunch. To some extent everyone gets what they need or want. The bumblebee (pollinator) gets food for itself or its offspring. The plant gets transfer of pollen from one flower to another. Plants that use animals to transfer pollen must provide two functions: advertising and reward. They must attract the pollinator and reward it for its work. The advertising generally consists of gaudily colored sepals or petals or stamens. This is a visual attractant to cue the pollinator. Olfactory cues (smells) may also be used, either separately or in combination with visual cues. This is one of the great ancillary benefits of pollination: wonderful smells are produced that we can enjoy if we take time to smell the roses.
There are, however, plants that are pollinated in a different way. Some plants are pollinated entirely or in part by wind or water transport of pollen. Grasses are perhaps the most familiar example of a wind-pollinated plant. Because wind-pollinated plants do not need the services of animal transport agents, they can dispense with the costs of advertisement (pollinator attraction) and reward (pollinator payment). A quick look at a grass will show that most do not have colorful parts or smell good to attract an animal. A closer look would show that most grasses have dispensed with sepals and petals completely, and they do not have parts that produce nectar as a reward.
Seed Dispersal
One of the most fascinating aspects of plant morphology is the complex array of forms that have developed to transport seeds to suitable places for them to grow. Seeds can be transported externally when they are caught on the fur or feathers of mammals or birds. They can also be transported internally, as when bears eat manzanita berries and the seeds are pooped out in a great steaming heap on the other side of the mountain, or when birds eat elderberries (Sambucus) and the seeds fall thousands of feet to splat in a landslide. One of the most wonderfully whimsical seed dispersal systems you will see is dispersal by ants. Many plants in California, and more globally, produce seeds with an oil-rich food body (an eliasome) attached. Ants gather the seeds, eat the eliasome, and discard the seed, which then grows in its new home. California examples of ant dispersal are Dicentra, Genista, Scoliopus, Trillium, Vancouveria, and Viola sempervirens.
PLANT COMMUNITIES OF CALIFORNIA
Every individual plant is unique in its form and each species has a distinct set of environmental tolerances that influence where it can be found. When plants with similar environmental requirements are regularly found together, we call them a plant community. Such communities blend into one another, so the concept is useful mostly as a human construct to make it easier to talk about natural environments.
The plant communities of California are determined by the various plant species’ genetic requirements and tolerances interacting with all of the aspects of the local environment. Climate, geology, and interaction with animals — notably elk, cattle, and people — influence the local and regional distribution of plants. Fire is also a huge factor in determining the distribution of plants. The broad treatment of plant communities that follows generalizes the plant communities of California into only a few, easily identifiable groups: beach vegetation (strand), grassland, salt marsh, freshwater marsh, coastal scrub and chaparral, mixed evergreen forest, oak woodland, riparian (or gallery) forest, coniferous forest (includes Douglas-fir forest, redwood forest, closed-cone pine forest, as well as other montane forest types), and hot deserts.
Beach vegetation, or strand, is the low, sparse, windswept carpet of plants occupying the sandy shore and the dunes and bluffs immediately adjacent to them. This group of plants is composed primarily of annual or herbaceous perennial plants. These plants must be able to put up with the thrashing delivered by ocean waves, high salinity, extreme winds, shifting substrate, and blowing sand. Many of these plants have very wide geographic ranges, with seeds that are dispersed by flotation in ocean currents up and down the Pacific Coast. This community is highly altered by people in many places, with seawalls, coastal homes and communities, and introduction of European beach grass being the main avenues of impact.
There is an abundance of grassland in California mostly composed of nonnative European and Asian annual grass species which often exists without much shrub or tree cover. The occurrence of grassland throughout the California Coast Ranges and Sierra foothills is intimately intertwined with historical land use, although there are some naturally treeless areas. Woodlands, forests, and chaparral have been cleared throughout the state for agriculture or pasture, usually by cutting and burning. The natural succession of grassland to brush to woodland or forest is retarded or suspended by grazing or burning. In most areas, grasslands return to shrublands and woodlands without fire or grazing. Wind-dispersed coyote brush (Baccharis pilularis) and bird-dispersed poison oak (Toxicodendron diversilobum) are usually the first colonizers, followed by trees such as oaks (Quercus), bay trees (Umbellularia californica), or Douglas-fir (Pseudotsuga menziesii).
This phenomenon is illustrated by the Golden Gate National Recreation Area. The land between the Golden Gate Bridge and Olema was a series of cattle ranches between 1820 and 1970. The ranches were first logged, then heavily grazed. Photos of the coastal slope from the 1950s and 1960s show expansive grasslands (cattle pastures). Since the land was purchased by the National Park Service in the 1970s, it has not been grazed. Coastal sage scrub has almost completely covered the former pastures and is now being invaded by Douglas-fir trees and bay trees, in part due to fire suppression.
A few areas where native grasses thrive still exist. Rangeland managers and restoration ecologists would like to replace exotic annual grasses with native grasses, as this increases the native biodiversity associated with these areas. In many grasslands, removing livestock and fire can cause overproduction of exotic annual grasses and result in the loss of native grasses and forbs.
Many otherwise rare grassland species are found primarily on serpentine soils. These are generally unfriendly places for plants to grow unless, like some California native plants, species evolve to thrive in these conditions and thereby avoid competition with species less tolerant of these harsh soils. Serpentine soil areas support a higher ratio of native plants to introduced plants than nonnative grasslands. Areas with serpentine soils are great places to see incredible displays of brilliantly colored wildflowers.
Salt marsh is another community of herbaceous plants, those adapted to periodic inundation (flooding) by salt water, followed by exposure to extreme solar radiation. Salt marsh is further characterized by extremely low soil oxygen and high rates of soil deposition, thus the plants of salt marshes must be able to cope with regular inundation and burial. Salt marsh plants are twice daily inundated with salt water and must be able to cope with high soil salinity and low oxygen. Not so obviously, many salt marshes have creek channels running through them and may seasonally be flooded with freshwater, another extreme rigor to which marsh plants must be adapted. When you think of salt marshes, you want to include both the vegetated and bare areas (the mudflats, tidal channels, and stream channels). The bare mudflats and the vegetated areas are intimately linked and function together as parts of a system, with the vegetated areas occupying slightly higher elevations and performing primary production, and the bare areas at slightly lower levels, getting inundated more deeply, and supporting diverse communities of invertebrate consumers and decomposers.
Despite all of these seeming disadvantages, salt marshes are sites of very high primary plant productivity and behave as nurseries for fish and other inhabitants of the estuary environment. Salt marshes are typically very flat and occupy areas of high utility for human beings. Thus, salt marshes suffer greatly during development. Ninety percent of the original Bay-Delta salt marshes are now converted to other uses. Los Angeles and San Diego have similar histories of salt marsh loss. Salt marshes are perhaps the most threatened plant community of the California coastal zone.
Freshwater marsh is an assemblage of different microhabitats. It includes the giant tule beds of the primeval Central Valley, the complex sloughs and islands of the Delta, vernal pools imbedded in grasslands, the wooded transitional marshes at the upstream edges of salt marshes, and the woody and herbaceous vegetation surrounding lakes. Anywhere seasonal or permanent standing freshwater is a primary factor in determining what plants grow on a site can be considered a freshwater marsh.
The plants of freshwater marshes, like those of salt marshes, often must cope with low soil oxygen. They also experience seasonally fluctuating water levels. Seasonally or permanently flooded areas exclude the great majority of plants and provide an opportunity to those that can cope with these conditions.
Prior to the damming, diking, and channelization of the Sacramento and San Joaquin Rivers and most of their major tributaries, these great streams flooded much of the Central Valley annually during the wet season. Controlling these rivers has made possible one of the greatest, most productive agricultural enterprises in history, and has eliminated huge, expansive, productive wetlands. When the big rivers of the Great Valley flooded each year, they filled many off-channel basins with water to depths of 3 to 12 feet for three to six months. As the floods receded, the basins gradually dried down, so by the end of September they were baked hardpans of dry, cracked soil. These basins were populated with humongous stands of tules (Schoenoplectus).
Another unique feature of the large, flat river valleys of California is the development of small, shallow basins (vernal pools) on a variety of terraces and low spots in the valleys and surrounding foothills. These basins fill with water a few inches to a foot in depth, dry gradually, and support a unique flora of annual plants growing in concentric rings determined by water depth.
Anywhere a river or creek enters a lake, a salt marsh, or a larger river, freshwater may pond seasonally or permanently. These “transitional marshes” are often wooded with willows (Salix), alders (Alnus), ash (Fraxinus), maple (Acer), or sycamore (Platanus). Beneath these deciduous trees you will find the herbaceous vegetation of a marsh: cattails (Typha), tules, sedges (Carex), and rushes (Juncus).
All of these marsh habitats are extremely important to wildlife, from the great flocks of migratory waterfowl found in seasonal wetlands of the Central Valley; to beavers, muskrats, and rails in transitional marshes; to the endemic delta green ground beetle (Elaphrus viridis) which occurs only in association with Central Valley vernal pools in Solano County.
Coastal scrub and chaparral are brush communities, characterized by dense stands of shrubs 3 to 15 feet tall. The shrubs are usually close together and intricately branched enough to make human passage difficult or impossible. Bears, deer, pigs, coyotes, gray fox, wood rats, and rabbits, however, move through them with ease. The two main discernible types of brush communities are coastal scrub, near the ocean, and chaparral in hotter, dryer, more interior sites. In the interior (away from the coast, chaparral) the herbaceous layer is often depauperate, although near the coast (coastal scrub) the herbaceous plants between the shrubs may form the majority of the biomass.
Chaparral is often composed of nearly pure stands of manzanita (Arctostaphylos) 8 to 15 feet tall. In other areas, the cover is a mix of manzanita, chamise (Adenostoma fasciculatum), wild lilac (Ceanothus), scrub oak (Quercus), and bush monkey flower (Mimulus aurantiacus). Chamise and bush monkey flower commonly form pure stands. Chaparral occurs on hot, south-facing slopes and on hillsides characterized by impoverished soil such as heavy clay or thin, rocky soil. Chaparral is often the aggregation of woody plants that will first colonize a disturbed area, especially after a fire. Manzanita seeds are known for their ability to remain viable through long periods of dormancy (50 – 75 years!). Mature stands of chaparral provide a shaded seedbed for their successors, oak woodland and coniferous forest. Chaparral shrubs, especially chamise, provide excellent deer browse, and their growth is often retarded by the “hedging” effect of this browsing. Coastal scrub generally lacks manzanita and chamise, rarely rises above 8 feet in height, and is usually dominated by coyote brush, coastal sage (Artemisia californica), California blackberry (Rubus ursinus), flowering current (Ribes sanguineum), and sticky monkey flower (Mimulus aurantiacus).
Mixed evergreen forest is a composite of many different trees, including oaks, bay, Douglas-fir, madrone, tan oak, and others. This forest forms dense stands with adjacent trees touching each other’s canopies. Mixed evergreen forests occupy sites subject to frequent or infrequent, often intense, fires. Ability to stump sprout after fire as well as leathery, hard, often spiny, evergreen leaves are the prime attributes of this community type. All plant communities intermix with other community types to a greater or lesser extent, but botanists do recognize a wide variety of community types and species associations. The mixed evergreen forest grades into and borders conifer forest, oak woodland, and grassland. In many places distinguishing them is somewhat arbitrary. Old forests and ancient trees are difficult to find in this community type, since the stands are very fire prone, and individual trees often succumb to the fires that exclude conifers from the site.
There is a very odd word you must learn if you want to be a California naturalist: sclerophyllous. The word comes from the Greek roots sclero (hard) and phyllon (leaf). Sclerophyllous plants are those with hard leaves, often with short internodes and marginal spines. The hard, evergreen leaves of coast live oak (Quercus agrifolia) are classically sclerophyllous, as are those of the other evergreen oaks, madrones, bay trees, and many of the shrubs that occur in chaparral. The needles of pine trees and Douglas-firs can also be considered sclerophyllous. Sclerophyllous plants are thought to have developed in response to increasing aridity. Over time (20 million years), as California became increasingly arid, many species of plants were excluded — that is, they went extinct or were extirpated from California. Others changed; they evolved in response to the changing climate and developed adaptations to resist draught. Hard, evergreen (sclerophyllous) leaves is one such adaptation. The waxy coating on many sclerophyllous leaves, reduced numbers of stomates, and having stomates only on the lower surface of the leaf all help minimize water loss through the leaf surface. These abilities are critical in the Mediterranean type climate California shares with Chile, the Mediterranean region, South Africa, and southwestern Australia. All of these other areas with Mediterranean climate also have vegetation types dominated by sclerophyllous plants, so if you learn the concept here, it will serve you well in your travels to these other Mediterranean climate areas.
Sclerophyllous leaves of hoary manzanita (Arctostaphylos canescens). Sclerophyllous leaves are hard, waxy, usually simple, and untoothed. The red objects are the “little apples,” the immature manzanita fruit. Photo by Kerry Heise
Oak woodland is perhaps the most widespread and characteristic plant community in California. The term is usually reserved for the lands covered in deciduous oaks, with hillsides clothed in evergreen oaks falling under the banner of mixed evergreen forest. Oak woodland is rich and variable in its floristic makeup, shares dominance among five tree species, and has the richest, most diverse shrubby and herbaceous understory of any forest type. Oak woodland also seems to harbor the greatest variety of native perennial herbs of any community.
California’s oak woodlands are amazingly rich biologically. They provide habitat to 120 species of mammals, 147 species of birds, 60 species of amphibians and reptiles, and 5,000 species of insects and arachnids. Astonishingly, 1 acre of oak woodland can contain between 10 and 100 million individual insects and other invertebrates! In addition, oak woodlands provide watershed protection, open space, and opportunities for recreation.
Oak woodland can be dense or savanna-like. On cool north-facing slopes, the deciduous Oregon oak (Q. garryana) is often abundant in Northern California. It is the only California oak that continues north to Oregon, Washington, and British Columbia, where it seems to appreciate the increased rainfall. Oregon oaks can be thought of as our most moisture-loving oak. Blue oak (Q. douglasii) is the dominant oak on many extremely hot, arid sites, and in fact forms a “bathtub ring” around the Central Valley, essentially mapping the rain shadow areas in three dimensions. It is the diametric opposite of Oregon oak, specializing in the most arid sites that support large trees. Valley oak (Q. lobata) is abundant on deep soils of flats at low to medium elevations. It grows to enormous proportions in the deep, rich soils of valley bottoms, especially along creeks. Valley oaks also have the ability to survive flooding, often growing in areas where water stands for months during the wet season.
Oak woodland provides a variety of habitats for other plants, including those with deep shade, light shade, sunny openings between widely spaced trees, and seasonal shade below deciduous trees as well as branches where epiphytic lichens and mosses perch. Perhaps the seasonal change of light penetration into these deciduous forests is the most salient characteristic, accounting for the preponderance of herbaceous perennials and shrubs in the forest understory.
Once established, oaks become highly resistant to fires. Thick bark allows California oaks to withstand even moderately intense fires with little damage. When fire destroys foliage or small branches, oaks are capable of epicormic sprouting: they force out new shoots from larger branches and re-create their small branches and leaves quickly. When the entire trunk and major branches are killed, oak trees will often sprout from the burned stump and roots. They are highly fire-resistant trees, occurring in a landscape that has evolved with frequent fires as one of the signature conditions of life.
Native Americans reached population densities in California greater than those of any other nonagricultural people in the world. Acorns, the large, single-seeded fruits of oaks, were one of the primary resources that made this amazing population density possible.
Riparian forest is found along riverbanks and other bodies of water. The floodplains of the Sacramento, Salinas, Los Angeles, and other large and small rivers and streams are often lined with deciduous trees. The names of these trees read like a catalogue of eastern deciduous forest genera: Acer, Alnus, Fraxinus, Platanus. These are genera that do not do well in the hot, dry hills of California. Essentially, these trees are hiding in the cracks, escaping the severe draught that descends on California every June by living on the banks of streams. None of these riparian trees have the adaptations to aridity so widespread in other California plants. They don’t need to! They have their roots down in the permanent water source that allows them to transpire as much as they want to, with more water immediately available to replace that which was lost.
The coniferous forest is characterized by evergreen cone-bearing trees (conifers) with one or more species sharing dominance. In much of California, the Douglas-fir is an important species of different coniferous forest communities. In places, especially in the fog zone along the coast, Douglas-firs share dominance with the unique California relict, the sequoia, or coast redwood (Sequoia sempervirens). At the dryer extremes, Douglas-firs cohabit with draught- and fire-adapted conifers like the knobcone pine (Pinus attenuata). They may also interdigitate (interlock) with or border the coastal pine, or Bishop pine (Pinus muricata). Douglas-fir trees live in dynamic equilibrium with the plant communities that surround them. Douglas-firs constantly throw seeds into mixed evergreen forests, oak woodlands, chaparral, and grassland in an attempt to take over these communities’ land holdings. Douglas-fir trees will take advantage of the partial shade provided by oaks or manzanitas, seed beneath them, and grow up through them. The Douglas-firs then shade out the other species, eventually killing them. Fire interrupts and/or reverses these changes, as young Douglas-firs are killed outright by fire while oaks sprout from trunk or stump and manzanitas sprout readily from seeds or burls. Large (60-plus years in age), thick-barked Douglas-fir trees are impervious to ground fires, but they succumb to crown fires.
There is a class of coniferous trees in California that illustrates how closely adapted to fire the flora of California is. These trees, called closed-cone pines or fire pines, produce cones (woody, seed-bearing structures) that don’t open the first year. The cones and the seeds they contain are stored on the tree, often for many years. When a fire enters the stand, the closed-cone pines burst into flame, actually exacerbating the fire with flammable chemicals stored in their needles and bark. The entire stand is destroyed, but the fire has another effect. It allows the cones to open, releasing the stored seeds, which sprout in the now open and fertilized habitat following the fire, and the stand is renewed. What this leads to is even-aged stands of trees over large patches of landscape.
Redwoods are one of the signature trees of California. Virtually everyone has heard of them, most Californians have seen and perhaps walked in a redwood forest, and many of us have them growing as cultivated ornamentals within a block or two of our houses. Redwoods are conifers, like the Douglas-fir and the fire pines. Redwoods are also paleoendemics — a species with a range that is a small remnant of a former much larger geographic distribution. Redwoods have a long evolutionary history and a great fossil record. Fossils of redwoods have been found far beyond the current, relict (surviving) range of redwoods. Redwood fossils are known from throughout the western United States and Canada, as well as in Europe, Greenland, Alaska, and China. The oldest known redwood fossils date back 160 million years!
The Sierra Nevada range provides a clear example of how elevation and other environmental factors, such as latitude, aspect, parent material, and soil, determine the types of trees that grow in a certain place. On the west slope of the Sierra, forests generally arrange themselves in broad elevational belts dominated by one or several tree species. Imagine a hike from the Central Valley floor, somewhere east of Fresno, to the top of the Sierran crest. You would start in oak woodlands and grasslands of the lower foothills, which give way to conifers such as Douglas-fir, ponderosa pine (Pinus ponderosa), white fir (Abies concolor), and sugar pine (P. lambertiana). As you climb higher, these species are replaced by forests of red fir (A. magnifica), Jeffery pine (P. jeffreyi), and lodgepole pine (P. contorta ssp. murrayana). Higher still, you find yourself in a subalpine forest of mountain hemlock (Tsuga mertensiana), western white pine (P. monticola), whitebark pine (P. albicaulis), foxtail pine (P. balfouriana), and limber pine (P. flexilis). The subalpine forests consist of short trees shaped and pruned by the heavy snow and high winds of their high-elevation habitat.
California’s hot deserts, the Mojave, Colorado, and Sonoran Deserts, located in the southeast portion of the state, are primarily scrub-dominated landscapes. The three deserts are distinguished by their climates. The Mojave Desert, located farthest north, is influenced primarily by winter rain from the Pacific. The hotter, subtropical Colorado and Sonoran Deserts receive moisture from convection storms during the summer months (July – September), in addition to infrequent Pacific winter storms. Creosote bush (Larrea tridentata), white burr sage (Ambrosia dumosa), and brittle bush (Encelia farinosa) form vast areas of scrub vegetation across all these deserts, especially in well-drained washes, bajadas, and alluvial fans. Distinctive features of the Mojave Desert include woodlands of Joshua tree (Yucca brevifolia), black brush scrub (Coleogyne ramosissima), and salt-tolerant shrubs of the genus Atriplex.
The Life of the Salt Marsh Bird’s Beak
Flower stalk of salt marsh bird’s beak (Chloropyron maritimum). The leaves are purple and covered with white crystals of excreted salt. Photo courtesy of Brad Kelley
One of the unique inhabitants of salt marshes of the Bay-Delta is the salt marsh bird’s beak (Chloropyron maritimum), an inconspicuous annual plant known only from salt marsh habitats in coastal California. The salt marsh bird’s beak has seeds that are stimulated to germinate when salinity is low. In high-rainfall years, when the “salt” marsh is mostly rinsed of salt by flows of freshwater, the bird’s beak sprouts in abundance. In years of low rainfall, when salinity remains high, the bird’s beak may sprout in very low numbers or not at all! The plant completes its life cycle (nine months) in “typical” salt marsh conditions as the rains pass, tides bring salinity levels back up, and day length increases.
PLANTS AND PEOPLE
People do many things with plants, including move them around. When we move to a new home, we commonly bring plants from the old place. Chinese workers brought tree of heaven (Ailanthus altissima) seeds to California to remind them of the lives they left behind in China. Tree of heaven is now widespread in California, with clusters of trees often marking sites of former Chinese habitation. We also bring and import plants of agricultural or horticultural importance. This is quite a two-edged sword. On the one hand, importing avocado plants from Mexico adds a delightful item to our diet and commerce. On the other hand, Eucalyptus trees, imported from Australia for ornament and in the mistaken notion that they could be grown for lumber to make railroad ties, have become noxious weeds along the coast of California, where they seed readily and form large, expanding stands that exclude native California plants.
Walk over to your spice shelf and look at all of the choices you are faced with to season your meals: salt, pepper, nutmeg, cinnamon, turmeric, allspice, cloves, and on and on. Now ask yourself which of these spices were available to native Californians as they lived for over 10,000 years in California before the arrival of Europeans in 1492. Here is the list: bay leaves, bay nuts, and a few odd roots you probably haven’t heard of and certainly haven’t eaten. Perhaps native Californians acquired paprika or cayenne by trade from Mexico, but probably not, or if so in very limited quantities. The point is that the world we take for granted is hugely shaped by the intentional and accidental movement of plants from one continent to another. When we move plants and plant products on such a massive scale, there are inevitably stowaways, unintended hitchhikers who make the journey with the intended contents.
Because people have taken plants with them as they have moved around the world, the world we inhabit today is a composite of elements from diverse regions. Most everyone would agree that it is a good thing that rice from Southeast Asia is now available to grow in the Central Valley of California, which is one of the most productive rice-growing regions in the world. Many people would also be delighted that they can grow rhododendrons from the Himalayas in their yard. What most people don’t realize is that transporting plants for agriculture and horticulture can impact native plant and animal communities. For example, transporting cultivated Rhododendron plants from Europe was probably the way the water mold Phytophthora ramorum, which causes sudden oak death, arrived in California.
We have a series of technical terms to designate the status of plants relative to geography. Native plants are those thought to be native or original to a region. Redwoods can be called many names, including endemic, paleoendemic, and native to coastal California and southwestern Oregon. French broom (Genista monspessulana), on the other hand, is a nonnative. Before people brought it to California as a horticultural plant, French broom did not occur in California.
Because Eucalyptus globulus and French broom are capable of growing, setting seed, and reproducing successfully in California without the help of people, we consider them both nonnative and naturalized. Nonnative plants like these that have successfully become naturalized and have attracted the attention of people as problematic in one way or another are termed invasive plants or invasive exotics. In extreme cases, where naturalized nonnative plants have important economic impacts or negative financial consequences, usually by disrupting agriculture, they reach the ultimate status of being termed noxious weeds.
Some Important Invasive Species in California
Yellow star thistle. Photo courtesy of George Hartwell
Arundo. Photo courtesy of Joseph M. DiTomaso
California has nearly 5,000 native plant species, the most of any state in the United States. Over 200 invasive species are threats to California’s wildlands and native plant species. Invasive species are second only to development in eliminating native habitat. Some of these are below.
Arundo donax L. (arundo, giant reed)
Arundo invades riparian areas, drying up groundwater and displacing native vegetation. Winter rains can distribute reproductive parts of this plant down the creek.
Tamarix spp. (tamarisk, salt cedar)
Tamarisk invasions have numerous impacts, including clogging streams, drying up wetlands, and increasing the salinity of soil. About 1.5 million acres in the US Southwest have been invaded by tamarisk.
Delairea odorata (Cape ivy)
Cape ivy takes over large swaths of riparian areas by growing in a solid blanket that kills other vegetation.
Genista monspessulana (French broom)
French broom is highly destructive to native plants and can cover whole hillsides. Despite this, it is still sold as an ornamental in gardening stores.
Centaurea solstitialis L. (yellow star thistle)
Yellow star thistle can be found in over 15 million acres in California, including rangelands, native grasslands, orchards, vineyards, pastures, roadsides, and wasteland areas.
Aegilops sp. (goat grass)
Goat grass is of concern because it has the duel ability to hybridize with winter wheat and to invade serpentine soils. Invasion of serpentine soils is a concern, as those soils also harbor many species endemic to California.
Native American Plant Uses
Native Americans recognized that in California one of the most stable, abundant, storable food resources available to them were the fruits of oak trees, acorns. There is abundant evidence that native Californians harvested and stored great quantities of acorns, processed them into staple food items, and revered them in their religious worldview.
Although native Californians didn’t “plant” oak trees, they very much “tended” them. One of the forms of TLC native Californians applied to the oak trees they intended to harvest was to burn around and beneath them! Fire was a primary “agricultural” tool in pre-European California. Broadcast burning was practiced on a grand scale, and probably for multiple purposes. One of the effects of repeated burning, in many places on an annual basis, was to reduce or eliminate shrubs from the oak woodland understory. This had the effect of making travel easier, facilitated hunting by opening up visual corridors, and made the collection of acorns simpler by clearing the ground the acorns would fall on. More broadly, repeated burning opened meadows and increased their size. Grasslands were another of the resource-harvest areas native Californians relied on, for digging liliaceous bulbs and for harvesting the seeds of annuals and herbaceous perennials. Perhaps the second most important plant food resource in California was pinole, a mixture of the seeds of a variety of herbaceous plants collected by beating seed heads into baskets.
There is a plant common in coastal California called Indian plum, or oso berry (Oemleria cerasiformis). The fruits of this shrub were highly sought after and were considered a delicacy. This fact is a testament to the scarcity of choices native Californians had compared with modern Americans. Indian plums are small, with a single, large seed. The taste is initially sweet, but there is a strong, bitter aftertaste. Most people, when encouraged to try them, will not ask for a second one.
Another layer of interdependence native Californians had with plants was their use of plants for tools and fibers. The baskets used to collect and store both pinole and acorns were made from various plant fibers, including willow, sedge, iris, hazelnut, ninebark, and redbud. Basket making in California reached levels of technical skill unsurpassed anywhere on Earth. Baskets were woven that were watertight! Basket making also intersected the realm of the mystical when designs for a basket were found in a weaver’s dreams. Digging sticks for harvesting liliaceous bulbs were crafted of mountain mahogany and toyon. Arrows were made of the straight stems of oceanspray. Houses and temporary shelters were made from a wide variety of plants, depending on the species available at a particular site.
We continue to depend on and interact with plants in numerous and sometimes surprising ways. California has been transformed since the arrival of Euro-Americans, with the damming of rivers for irrigation and flood control, the removal of oak woodlands, the plowing of the Central Valley for agriculture, the elimination of elk, and extensive grazing being perhaps the most noticeable. We have imported an astonishing array of plants to California from all corners of the world. California is a plant enthusiast’s dream come true. The variety of plants available for agriculture, horticulture, crafts, and study is truly remarkable.
CALIFORNIA’S PLANT COMMUNITIES AND CLIMATE CHANGE
Climate in much of California is predicted to become warmer and drier as a result of global accumulation of greenhouse gasses. This will affect native plant communities and populations. Blue oak – gray pine woodland may increase, and valley oak range is predicted to shrink. Reductions in water availability could impact vernal pools, ponds, wetlands, and spawning tributaries of rivers, impacting amphibians and fish, among other fauna. Fire risk will increase with increased temperature and decreased moisture; at the same time, fire suppression is likely to continue at the urban-wildland interface, leading to buildup of fuels and a greater potential for catastrophic fires in the future.
Climate change is already influencing the distribution of plant communities in California. For example, the downslope edges of forests in the Sierra Nevada have been shown to be creeping to higher elevations. What is unclear is how extreme the changes will be. Changes in species distributions, community composition, and dominant cover types are likely. These vegetation changes will influence the distribution of animals as well as ecosystem processes such as nutrient cycling.
The effects of climate change on plant communities include
Shifting of species ranges to the north
A loss of species in Southern California
An increase in invasive species
Increases in drought-tolerate species
Sea level rise, which will alter coastal plant communities, erode beaches, and inundate tidal areas, marshes, and wetlands
A more in-depth discussion of the effects of climate change and California’s natural communities can be found in the Climate Change section of Chapter 7.
Explore!
TAKE A CREEK WALK
Walk a local creek. Can you identify the riparian plants? (Beware of poison oak!!) Can you tell where the riparian community ends and the upland community begins? If you don’t want to walk alone, contact a local park or preserve, creek association, the California Native Plant Society, or a Sierra Club or Audubon chapter for information about creek walks.
LEARN ABOUT A LOCAL PLANT COMMUNITY
Choose a piece of land you care about, such as your own property, a local oak woodland, a redwood grove, a creek, a wetland, or a local park. Spend a day walking and sketching it and writing down what you notice. Then learn its history. Your local library, the county clerk’s office, and the park or preserve’s administration offices will have historical records, but you may find that the best source of information is oral history. Ask someone who has lived in the area for a long time about that land.
VOLUNTEER AT A NATIVE PLANT NURSERY
This is a fun way to learn local plants and also learn about local plant issues in your community. Look in the phone book, ask at conventional nurseries, or call your local California Native Plant Society chapter (www.cnps.org) to find a native plant nursery.
EXPLORE YOUR BACKYARD
Spend a half hour in your backyard without any interruptions. Take a journal and write down and/or draw what you see, hear, smell. Survey the plants and make note of any you can’t identify. Pick three to learn more about. Then go to a local park and see if you can find any plants that are the same as the ones in your yard.
PARTICIPATE IN A RESTORATION PROJECT
Restoration projects will get you pulling weeds, planting native plants, and if you are lucky, collecting seeds. They are fun and a great way to increase your knowledge of local plants. Check with local parks and creek “friends of” associations to see if they hold regular restoration days.
PRESS PLANTS
Pressing plants is another great way to get to know local plants. To make a small field plant press, cut two 8½ inch by 11 inch pieces of cardboard and place layers of newspaper between the cardboard. Collect the stem with attached leaves and, if at all possible, flowers and/or fruits, and place them on the newspaper, cover with several pieces of newspaper and cardboard, and wrap rubber bands around the bunch. A more complete guide for “How to collected, press, and mount plants” is available from Montana State University Extension at http://msuextension.org/publications/AgandNaturalResources/MT198359AG.pdf.
LANDSCAPE WITH NATIVE PLANTS AND WILDFLOWERS IN YOUR YARD
About 30 to 60 percent of urban freshwater is used for maintaining US lawns, along with the application of 67 million pounds of synthetic pesticides. Native landscaping makes your yard unique and attractive to native fauna such as butterflies. The California Native Plant Society website (www.cnps.org/cnps/horticulture/brochure.php) and the Nature Conservancy website (www.growingnative.com) have excellent information to get you started.
MAKE ART ABOUT PLANTS
Sit in a natural place you love and write a poem or a song, draw a picture, make a painting, or take a photograph of something that inspires you. Try to incorporate naturalist details into your work, such as the shape of the leaves, pollinators, insects that use the plants, seeds, or whatever you notice and feel drawn to.