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Landowners Guide to Native Grass Enhancement and Restoration
1. Introduction and Background
by Mark Stromberg,
Ph.D. Hastings Natural History Reserve, UC-Berkeley
Sorry about the heavy dose of text. But it is a good story...
Native grasses are interesting characters. They can be amazingly old. Many bunches of purple needlegrass are at least 200 years old and some might live as long as 1,000 years. As one of the old Califorñios, they deserve our respect as tough survivors. Using roots that extend up to 18 feet, they tap into nutrients and water found deep in the soil, and so remain green even in the hot, dry months of fall. They have survived many long California droughts, attacks by insects and the impact of fire. They tolerate mowing, grazing and even foot traffic. Each year, they produce a modest crop of graceful seeds and sometimes these give rise to a few new plants. Our native grasses almost always occur in patches with bare ground between them. Wildflower often grow in these open spaces. Grasslands protect views from our dwellings and protect buildings from wildfires. They provide green fodder for wildlife and domestic animals, and cover for wildlife to build nests and hide. They harbor beneficial insects. Our native grasses provide a stunning visual diversity; indeed a window into the earth. When we take the time to look at a simple square foot of prairie grasses, an amazing complex of textures, colors and forms swirls before us.
The root systems of native perennial grasses gently form delicate long tubes deep into the dry soil- when the winter rains finally arrive, the rain percolates along the roots of the grass plants where it is stored deep in the soil. The native grass root systems filter pollutants and catch soil eroded from above and stabilize steep hillsides. When they eventually die, the roots of the native grasses become carbon and other nutrients that promote soil formation and deep soil nutrient enrichment.
Californias grasslands are cloaked in a mystery of loss. As we look across the landscape, we see that 99% of the golden rolling hills of California are covered in annual grasses from the barnyards of Spain. An observant landowner can recognize the native grasses and see that our perennial, native grasses are missing from much of the landscape. Knowing this, it makes owning an intact relict of native perennial grassland so much more valuable. But one might ask then, how did such a vast landscape become converted over such a large landscape and to such an extent?
If we understood why the native grasslands have become reduced, we will find the clues we need to manage or restore the native California grasslands. And, we have a few clues to help us in the process of discovering the answer to this mystery.
First, California is one of only five places on the earth where it does not rain in the summer, and where late winter rains are common. These Mediterranean climates are widely separated; as if they were five islands scattered across the earth (other are in Chile, Turkey-Spain, South Africa, Australia). Such islands, like all other true islands, tend to have many species that are found nowhere else on earth (endemic species). And like on most islands, the native plant and animals often have few defenses against invading newcomers (weeds, diseases, etc.). In Hawaii, for example, most of the nearly 1,200 native species are endemic. Extreme endemism, combined with a large number of non-indigenous plants and major habitat alteration by both Polynesians and Europeans, has made 61% of Hawaii's suite of native plants the most threatened of any state. California is the second (32%) in the list of states with the most threatened flora. Of some 4,800 plant species in the California Floristic Province (which extends north to Gold Beach, Oregon and south to Enseñada, Mexico) 2,500 are endemicthey occur nowhere else on Earth. (Doyle, 1997 Myers et al., 2000).
Here is another clue to the decline of native California grasslands; an invasion of exotic species occurred in California, indeed in most of North America. Certainly by the 1500s, Europeans from the Mediterranean started to arrive in California and brought with them non-native (exotic) plants accidentally, as ship ballast, for trade or intentionally as food, medicine or ornamental use (Brossard et al 200). Bricks in the first Spanish missions, made from mud mixed with soil from around the building site have very few seeds of these introduced weeds. As the missions were built, the brick had ever increasing amounts of seeds of these invaseive, aggressive non-native plants (Barbour and Withworth, 1992). Among these were the filaree (Erodium spp.) as well as ripgut (Bromus diandrus), wild oats (Avena spp.) and other small bromes (B. hordaceous) and fescues (Vulpia myuros, etc.). By the 1700s, Europeans had brought a suite of hundreds of non-native, short-lived (annual) Mediterranean-European plants that were, by chance, pre-adapted to thrive in this Mediterranean climate. And thrive they did! By the late 20th century, in most of Californias grasslands, most of the plant species present are exotic (Withers et al. 1999).
Exotic Invasions of North America (Maps-above). The percentage of plants that were non-native in regional and local floras, based on either a larger scale (left) or local scale (right) in about 1900 (top) and in 1996 (botton). Even "Kentucky" bluegrass is not native, and it was among many grasses brought into the east coast with the first wave of European settlement. The wave of non-native species has swept west at either scale. For mor information, see Withers et al. 1999.
Native grasslands often include areas of bare ground between the grass plants. This bare area once provided a place for annual flowers, and these can be seen in profusion in the Carrizo Plain, where distance between native bunch grasses are much greater than in this photo of Carmel Valey. This bare ground also provided an opening for Mediterranean plants that, by chance , were from a nearly identical environment. Many of California's non-native weeds spread through the entire state in less than a hundred years.Yellow star thistle, Centaurea solstitialis, and tumbleweed, Salsola tragus, are examples.
Photo. Purple needlegrass
(Nassella pulchra) in upper Carmel Valley. Note the spacing
between the plants. The dry, dead material between the green clumps of
graass is mostly Erodium and Vulpia. During very dry periods,
the mother plants can so deplete the deep soil moisture that they kill
the smaller seedlings. Thus, like many other desert plants, these Nassella
plants are farther apart than you would expect at random. The distance
between them, like trees in a orchard, reflects the long-term balance
between rainfall and the number of plants that can survive.
We know the approximate time of this invasion of non-natives into the California scene. Clues are found in early adobe bricks used in Spanish settlements made from native soil. The soil would include many of these types of seeds. Such debris was trapped in bricks that can give us approximate dates of introductions of non-natives. The oldest adobe buildings built in 1769 by Junipero Serra contain only the seeds of three common European weeds, including red filaree (Erodium spp.). As the missionaries moved north, the bricks contained more and more of the European weeds (Barbour and Withworth, 1992). Our native grasses persist, but during the spring, these annual invaders rapidly turn green, make big, abundant seed, drop them by the millions and then die. Only later in the year (photo) can one see how the deep-rooted native perennial grasses are still green. Studies done at the Hastings Natural History Reservation in upper Carmel Valley show that these clumps (see photo) survive at least 200 years and probably 1,000 years (Hamilton, 1997).
Another factor in the rarity of native perennial grasslands is that much of the natural carpet of life on the soil of California has been dramatically altered by human activity. Only about a quarter of Californias natural vegetation remains (Edgar, 2000). Even more problematic, the grasslands in California have been particularly hard hit, less than 1% of the original grasslands remain (Huenneke, 1989). Our coastal grasslands have almost entirely disappeared. Most of the reduction in California grasslands has been due to historical land use. The potreros were often the first places to have been plowed and planted with Spanish barley. Then, the deep, level soils of the valley bottoms saw their grand valley oaks removed and the areas planted to more grain. After the 1849 Goldrush, new homesteaders (1860s-1890s) sought a living by farming any available open land in Monterey County. Eventually, most of the arable land in Monterey County, like much of California's more productive soils, was disked or plowed each year. With each pass of a steel farm implement, the sensitive growing points of the native perennial grasses, located a few inches beneath the soil level, were removed and the grass plants died.
Exponential growth of the human population in California has converted much of the grassland and oak savanna into housing and associated roads, paved areas and disturbed lands.
What is exponential growth? An example might help; if a pond was being covered with lilies growing at an exponential rate, andyou knew it took 100 days to entirely cover the pond, on which day would half of the pond be covered? The 99th day.
Was historical intensive grazing a factor in the decline of native California grasses? California did not have extensive herds of grasslands animals, like buffalo in the Great Plains. Scattered herds of elk, deer, antelope other grazing animals were abundant. Unlike the Great Plains, where over the last 10,000 years many species of dung beetles developed, California has no native or endemic dung beeltes. This is clearl evidence that herds of dung-producing grazing animals were not part of the evolutionary background in California, as they were in the Great Plains (Mack and Thomson, 1982). Nevertheless, huge herds of sheep and cattle were introduced to California. From the early 1800s to 1880s millions ofof wild cattle ranged across central California. Tens of thousands of hides were shipped out of Monterey Bay each year by skinners in the 1850s who left the cattle carcasses to rot. One might think that the history of intensive grazing would have lead to the demise of large areas of native grasses. However, this is probably not so. Certainly some patches could be so heavily impacted by cattle that the native grasses were destroyed, for instance corrals and gathering areas. However, there are many examples from across the state that show moderate grazing, even a history of short-term intense grazing by cattle and sheep can be compatible with native grasses. Grazing lands are often the last significant refuges for areas with native California vegetation, including many patches of native grasses.