The word “riparian” is derived from the Latin work ripa, which refers to the banks of a river. Riparian vegetation is adapted to life on river banks, including periodic inundation, movement of sediment and debris, and changes in the shape and location of the river channel. The shape and size of the river valley, channel shape, gradient, and hydrological setting (e.g., total precipitation, amount of precipitation as snow) all determine the plant species and structure of the vegetation communities along the river. Tejon Ranch has a huge diversity of riparian communities, corresponding to the landscape’s topographic, climatic, and hydrological diversity. These different vegetation communities support different wildlife species that use streams and riparian vegetation for cover, food, breeding, and as “movement corridors” through the watershed. These water sources and the variety of vegetative structure provided by riparian communities—herbaceous ground cover, shrubs, and tree canopy—are especially important in an arid landscape such as the southern San Joaquin Valley. Because of these factors, riparian habitats—in association with their adjoining terrestrial vegetation communities—often support high plant and animal species biodiversity.
|Lush yerba mansa (Anemopsis california) meadow within the Tejon Creek riparian corridor.|
|The riparian corridor of El Paso Creek connects low elevation grassland habitats to high elevation mixed conifer habitats.|
Riparian and other wetland communities are priorities for conservation management in the Conservancy’s Ranch-wide Management Plan (RWMP). The loss of understory by excessive dry-season grazing, and rooting of the channel and floodplain by feral pigs are the primary threats to the condition of riparian habitats at Tejon Ranch, particularly low elevation reaches of streams on the San Joaquin Valley side of the Ranch such as Tejon Creek, El Paso Creek, and Tunis Creek. Over the last 2 years the Conservancy has been working with our partners at the Tejon Ranch Company and the Echeverria Cattle Company (one of the Tejon cattle lessees) to develop new ranching infrastructure that, when completed in 2016, will allow us to reduce cattle grazing in riparian habitats during warmer, dryer times of the year. We are also exploring the effects of feral pigs by installing experimental pig exclosures in a few riparian areas (more on this below).
|New fence along lower Tejon Creek (left of photo along toe of slope) to allow better management of the riparian vegetation.|
This year Felix Ratcliff, a PhD Candidate at UC Berkeley, completed his 3rd year of research studying riparian habitats on the San Joaquin Valley side of Tejon Ranch, including reaches of Tejon Creek, Chanac Creek, El Paso Creek, and Tunis Creek. Supported by a generous anonymous donation to the Conservancy, Felix is investigating both the environmental factors—geology, soils, and elevation—and management factors—cattle grazing and feral pig disturbance—that shape these riparian communities. Thus, his research will help the Conservancy better understand how to improve the condition of riparian habitats to benefit native wildlife, such as breeding birds, and plants found along creeks on the Ranch.
|Felix Ratcliff checking out wildlife camera results in the field.|
|Cottonwood-willow riparian forest in Tunis Creek, with large trees in the overstory.|
|Willow riparian scrub in Sacatara Canyon is dominated by shrubby willows with few large overstory trees.|
Over the 3 years of the study, the riparian plant communities in his study reaches have remained fairly similar over time. This year the Conservancy installed fencing in 5 reaches of Felix’s study area to evaluate the effects of eliminating disturbance by pigs and cattle. With the installation of new fences and livestock water systems, we now can modify management practices to improve riparian conditions. Using Felix’s baseline data before installing the fencing, we have an opportunity to observe the effects that cattle and pigs have on vegetation (without and with the exclosures). And with the increasing chance of an El Niño winter, we may have the opportunity to see how riparian vegetation responds to a wet winter in different areas (keep your fingers crossed!).
On a side note, the pig exclosures provide a great example of the trials and tribulations of a field biologist (particularly one whose graduate school clock is ticking!). The Conservancy installed the 5 exclosures as part of Felix’s research project to determine the effects of eliminating pigs and cattle from the riparian habitats he is studying. The exclosures are square-ish, nearly 200 feet on a side, and straddle the creek, which means two sides of each exclosure cross the creek. You may also recall that while we are in our 4th year of drought (come on, El Niño), we did get some pretty good thunderstorms over the summer. Long story short, one of those summer thunderstorms sat over Tejon Ranch and caused very significant flooding and debris flows in El Paso and Tunis Creeks, blowing out the fence segments that crossed the creeks. Obviously not a very effective means of keeping cattle and pigs out! The idea of the experiment was to have 5 different study reaches (out of 15) with exclosures and the rest without. Having 2 of the 5 exclosures compromised was not good experimental design to say the least. Fortunately, with a little elbow grease from Conservancy staff Laura Pavliscak and Scot Pipkin, Felix was able to repair the exclosures. We are now waiting to see what El Niño will bring us but are hoping that we will not have the catastrophic debris flows that destroyed the exclosures this summer.
|A forlorn Felix examining the breached fence in the El Paso Creek pig exclosure.|