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.
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| Lush yerba mansa (Anemopsis california) meadow within the
Tejon Creek riparian corridor. |
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| 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).
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| 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.
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| Felix Ratcliff checking out
wildlife camera results in the field. |
Felix has found that distinct plant communities occur on
stream reaches with distinct environmental characteristics. Depending on the
site, riparian habitats may be dominated by dense willows, have open canopies with
annual grasses in the understory, or have massive tangles of wild grapes
covering the ground and climbing the trees. The plant species and structure of
the habitat determine which wildlife species use the creek. Cattle and pigs are
by far the most commonly seen mammals in Felix’s study reaches, but mule deer,
bobcats, black bears, mountain lions, and badgers are detected regularly in
these riparian areas as well. He has found 5 snake species (California king
snake, Pacific rattlesnake, night snake, and gopher snake) and 4 lizards (side
blotched lizard, Gilbert’s skink, Western fence lizard, alligator lizard). The
Conservancy has also been sponsoring riparian bird surveys conducted by the
Southern Sierra Research Station, and Felix is incorporating their data into
his analyses. His preliminary analysis shows that some bird species are more
likely to occur in areas of the creek with a wider corridor of trees and
shrubs.
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| Cottonwood-willow riparian
forest in Tunis Creek, with large trees in the overstory. |
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| 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.
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| A forlorn Felix examining the
breached fence in the El Paso Creek pig exclosure. |
As part of our stewardship mission, the Conservancy will
continue to restore and enhance riparian and wetland habitats at Tejon Ranch.
Yes, the primary objective of our stewardship is to increase conservation
values of these habitats, but we also want to learn from our efforts so that we
can understand the
best ways to
increase conservation values and improve our work in the future. We want to continue
sharing these projects with you to illustrate the complex ecology of these
habitats and how we can better protect and manage them. So come on out to the
Ranch and learn more about our riparian conservation efforts!
