Brown Farm is a 486 acre property. The Regional Parks Rodota Trail bisects the northern area of the farm and hikers can enjoy views of Brown Farm between Petaluma Avenue in Sebastopol and Llano Road. The farm has a holding pond that can be filled during the winter and spring to provide water for summer irrigation. Summer irrigation allows several local dairy producers to grow multiple hay crops in a season. Gravenstein and Windmill Creeks cross the property, traveling toward their confluences with the Laguna de Santa Rosa. Seasonal wetlands and valley oaks dot the landscape. Brown Farm has three non irrigated/farmed natural areas, all approximately 20 acres. The Brown Farm Valley Oak Restoration is located on the eastern border along the Llano Road frontage. The Brown Wildlife Area is located on the western end of the farm, bordering the Laguna de Santa Rosa. The Vernal Pool Natural Area is located on the northeastern area of the farm. A number of special management projects have occurred in both non-farmed areas, as well as throughout the greater farm.
Gravenstein Creek historically was likely a seasonal, shallow creek or swale. When the City of Santa Rosa purchased the property in 1979 there was no vegetation along this waterway due to years of livestock grazing the property. Beginning in 1996 a setback of 75 feet was established along both sides of the creek and native trees and shrubs were planted in 1996, 1998, 2005 and 2006. Approximately 2000 trees and shrubs have been planted, including willow, ash, valley oak, box elder, elderberry, hawthorn, black walnut, wild rose, coyote bush and currant. Riparian vegetation provides important food, shelter and shade for both aquatic and terrestrial wildlife. The corridor furnishes animals with a route to migrate or disperse under cover. Riparian and in-stream habitats support each other, providing necessary resources. Stream-side vegetation is rooted in rich soil, obtaining growth nutrients. The roots of trees and shrubs help hold the soil in place, preventing erosion. Leaves drop into the water, supplying food for aquatic microorganisms and insects. Insects and other invertebrates are consumed by fish that are in turn consumed by other animals. Organic matter is broken down by decomposers and returned to replenish the soil. Dense riparian canopy shades the water, preventing exposure to the sun, and resulting in a significantly lower water temperature. Many organisms have a narrow range of tolerance for temperature. Colder water holds more dissolved oxygen, a critical factor for many animals, especially certain species of fish.
Windmill creek flows along the southern border of Brown Farm, traveling west towards its confluence with the Laguna de Santa Rosa. The City of Santa Rosa was funded in 2000 for an exclusionary fencing project on Windmill Creek. The purpose of this project was to protect the creek from erosion and pollution while controlling exotic invasive species in the grassland and reducing fire potential with livestock. In the spring of 2000, seven thousand feet of fencing was installed, parallel to Windmill Creek at a set back of approximately fifty feet from both banks. In February 2001/02 Natural Resource Specialists (NRS) worked with schools and community groups to revegetate the creek. Valley oak acorns were planted in cups and leaf mulch piles. Arroyo willows were sprigged. Basket sedge and wild rose were transplanted. Annual maintenance of weeding and watering occurred for two years after each planting. Each year in June, after the ground is no longer wet enough to cause pitting, heifers are brought in from the neighboring dairy for three to six weeks. In 2003 a herd of approximately twenty young heifers grazed the valley oak/grassland complex for one month. The residual dry matter was reduced without significant damage to the oaks. NRS conducted a plant survey and found native forb and grass species in the grazed area. The fenced area was also monitored and the all planted species are doing well. Grazing has been continued in a similar time schedule and intensity.
Brown Farm Valley Oak Restoration
One of the first oak restoration projects in California took place on Brown Farm. In 1979 150 valley oaks were planted along the frontage of Llano Road. An additional 100 trees were planted in 1991. Oaks play an important role in the Laguna ecosystem. The valley oak is the most abundant oak species in the Laguna. They are found as a dominant tree in both the riparian and upland communities. Oaks form the foundation of an intricate food web where herbivores consume acorns, leaves, twigs, sap, roots, flowers and pollen. Because oaks have a diversity of food to offer, they support many types of organisms that use different resources from the same tree. Valley oaks provide shelter to many organisms. Every part of an oak from treetops to root tips is utilized. In the leaf canopy the wind, light and temperature are moderated. Birds take advantage of this protection to build nests and insects deposit eggs. Cavities in the limbs and trunks provide nesting and hiding opportunities even long after the tree has died. A standing dead tree is referred to as a snag. Often snags are removed and with them a potential home to animals using the cavities or living under the bark. Snags also serve as perches, used by birds of prey as they hunt. The leaf litter under the tree is a moist, nutrient-rich location where many invertebrates and microorganisms live. The soil below the rich litter, surrounding the roots, is home to many arthropods, protists, fungi and bacteria.
Brown Farm Wildlife Area
The western edge of the farm, bordering the Laguna de Santa Rosa, was removed from irrigation and farming in 1990. The area is within in the annual flood plain of the Laguna and the natural regeneration of riparian species has been dramatic. Forests of valley oaks are becoming established under the canopy of mature trees and across the grassland. Beds of basket sedge grow thickly along the bank of the Laguna. Thickets of California wild rose, California blackberry, snowberry and poison oak provide the under story of the riparian forest adjacent to the Laguna channel. Willow and ash create the next layer, followed by the valley oak which emerges high above the forest as the tallest tree.
Vernal Pool Natural Area
Dotted in the grassland mosaic on the Santa Rosa Plain is a special type of wetland known as vernal pools. Vernal pools are seasonal wetlands that are intermediate in moisture between the grassland and a permanent wetland such as a marsh. They occur in very few places in the world. The reason for their rareness is a set of three conditions necessary for their existence. These particular environmental factors are a topography of shallow depressions where water can collect, a water impermeable layer close to the soil surface and a rainfall regime that allows the pools to alternately pond and dry. All these requirements are met on the Santa Rosa Plain. Look at the landscape of the Santa Rosa Plain and notice that seemingly flat stretches are subtly contoured with shallow depressions. Sometimes these depressions are isolated pools and other times they are swaths, or swales, connecting one low area to another. Vernal pools are seasonal wetlands that fill during the rainy winter months and dry out completely during the summer drought. Wet winters and dry summers are known as a Mediterranean climate. The reason that rainfall collects in depressions in the landscape instead of soaking into the soil is due to some type of water-impermeable layer below the soil surface. In the Laguna uplands, the layer is a hardpan of clay. If the hardpan layer is cracked, the depressions will no longer function as vernal pools. Three main zones, the pool bottom, edge or margin and upland, describe vernal pools. As the winter rains abate and water recedes, vegetation blooms, creating the stratified zones that characterize vernal pools. Plants growing in the pool bottom are generally the last to flower. Inundation in the pool bottom may last three to five months. This discourages invasion from exotic annual grasses. For this reason vernal pools are often described as islands of native species. However, several drought years may allow the movement of upland grasses down to the pool bottom. The vernal pools and swales of the Santa Rosa Plain are diverse in topography, hydrology, flora and fauna. The species vary from one pool to another, even between pools located in close proximity. Basically there are no two alike, but they all share the annual regime of summer desiccation. Lack of summer moisture caused plants and animals inhabiting vernal pools to adapt in order to cope with this challenging environment. Plants adapted to vernal pools must be capable of germinating and beginning to grow in ponded or saturated conditions. Vernal pool flora often have leaves modified for floating, allowing exposure to sunlight for photosynthesis. Waterlogged soils create a low-oxygen environment so plants adapt with physiological features enabling them to transport oxygen from the leaf to the root area. Plants continue to grow as the water recedes and often change their morphology as they transition from aquatic to terrestrial. Most vernal pool species are annuals, producing flowers and setting seed before the soil is dry. Vernal pools are home to many animals. Amphibians, such as pacific chorus frogs and tiger salamanders, lay their eggs here. The young hatch and metamorphose to a terrestrial stage before the pools dry. Adults and young may then migrate away from the pool to spend the dry season elsewhere. Also living in vernal pools are many specially adapted microscopic creatures. They secrete a protective coating that allows them to resist desiccation, waiting in suspended animation until the next winter rains begin. Others leave eggs or cysts to endure the dry season in the pool bottom. Because of these necessary adaptations, vernal pools are home to organisms that are unique in the world. When an organism lives only in a specific geographic location it is referred to as endemic to that region. Endemic species are easily endangered because no backup populations exist elsewhere. All the plant and animal species endemic to the vernal pools of Santa Rosa Plain are in danger of extinction. Some vernal pool plants and animals have been officially recognized and listed by the state and federal governments as endangered species. In 1989 a process began to enhance vernal pools in the northeastern area of Brown Farm (grid 11). The area was removed from irrigation and farming, receiving an inoculation of topsoil from a vernal pool site that was slated for development. The pools receive ongoing monitoring and provided a site for research on the effects of litter (dead biomass) removal on vernal pool plant communities. Research indicates that removing the layer of litter give many species an opportunity to germinate and grow. Litter is removed manually by thatch rake and mechanically by mowing.
Valley Oak Buffer Areas
A farming setback from valley oaks allows natural regeneration under mature trees. The area under the canopy or drip-line of a tree is where acorns fall and germinate. Feeder roots close to the surface extend out even beyond the canopy and require protection from disking and plowing. Irrigation is redirected away from the mature trees to avoid stimulating weedy competition under the canopy and to lessen the potential for increased fungal growth on living trees.
Highway 12 Oak Mitigation Planting
When CalTrans widened Highway 12 on the north border of Brown Farm, 4 mature valley oaks were removed. To mitigate for this loss 875 valley oak seedlings were planted in a 10 acre strip along Highway 12. Survival to date has been greater than the required 80%.
Invasive species have the ability to thrive and spread aggressively outside of their natural range. Plants imported to new habitats have the ecological advantage of being introduced without their natural predators. The insects, diseases, parasites and foraging animals that prey on them are no longer present. Weed management requires multiple tools including, removal by hand, repeated mowing, grazing, burning and herbicide. All these management strategies have been employed on Brown Farm. The species of special concern include harding grass (Phlaris aquatica) and bristly ox tongue (Picris echioides).