One of the Conservancy’s priority resources for management
at Tejon Ranch is our grasslands. Tejon
Ranch supports over 100,000 acres of grasslands, which in-turn support many
native plants and animals for which we would like to enhance conditions. Under the Tejon Ranch Conservation and Land
Use Agreement, conservation of the Ranch is via conservation easement and under
these conservation easements the Tejon Ranch Company retains the right to run
livestock in conserved lands. Therefore,
developing a better understanding of our grasslands and identifying ways to
better manage them has been a high priority for the Conservancy since its
inception. To gain this knowledge, we
embarked on what is now a 5-year research partnership with the UC Berkeley
Range Ecology Laboratory directed by Dr. James Bartolome. The research briefly discussed below will
ultimately serve as the PhD project of Sheri Spiegal, who is expecting to
finish her degree at the end of the year.
You can find more details on our grassland research at our website: http://www.tejonconservancy.org/research.htm
The focus of the Tejon Ranch grasslands research has been to
document how the composition of plant species in our grasslands changes from
one location to another on the Ranch and from year to year (primarily due to changes
in weather). One of the findings of
Sheri’s research is that geographic locations that support grasslands on Tejon
Ranch can be usefully organized into ecological
sites. An ecological site is a set of land units with a common
climate, similar topographic and soil characteristics that support similar potential
vegetation, and respond similarly to management. The idea is that a site with a particular
combination of soil, topography, and climate will support a specific set of
plant species, while another site with different soil, topography and climate will
support a different set of plant species.
For example, Sheri has found that sandy soils at flatter, low elevation
locations in the San Joaquin Valley support a different set of plant species
than do silty soils, on steeper sloped locations at higher elevations in the
foothills of the Tehachapi Mountains.
 | |
| Ecological sites can change over short distances. In the Tejon Hills, soils change quickly making room for a variety of rare plants. In the northwest (green) portion of this area, plants such as Comanche Point Layia (Layia leucopappa) can grow due to sandy soils. In the eastern, higher portion of the hills (red), clay soils support more geophytes, like striped adobe lily (Fritillaria striata). |
To-date
eleven ecological sites supporting grasslands have been identified at Tejon
Ranch. Furthermore, Sheri has also found
that plant species in our grasslands vary in their species composition from
year to year depending on weather, but that the changes in species composition
within ecological sites are more similar than the changes seen between
different ecological sites. So the
ecological site concept does appear to be a useful way to describe grassland
plant communities and their changes over time.
The use of ecological sites in range management is being promoted by
agencies such as the USDA Natural Resources Conservation Service (https://esis.sc.egov.usda.gov/About.aspx), and the Conservancy is
using this ecological site framework to organize our grassland and grazing
management planning.
"An ecological site is a set of land units with a common climate, similar topographic and soil characteristics that support similar potential vegetation, and respond similarly to management."
One of the interesting and relevant findings of this research
is that some ecological sites tend to support higher abundance of native plant
species, while other ecological sites are always dominated by nonnative plant
species, but the abundance of natives can vary dramatically from year to year
based on weather. Look at the photos
below, which show two different ecological sites (Sandy Alluvial Flats and
Sloping Loamy Sands) in two different years (2010, 2011). In general, the colorful wildflowers are
native species while the green grass is predominately nonnative. You can see that the Sandy Alluvial Flats
ecological site supported good native wildflowers in 2010, whereas the Sloping
Loamy Sands ecological site was dominated by nonnative grass. However, in 2011 both sites were dominated by
nonnative annual grass.
The Conservancy’s challenge is to identify grazing
management regimes that can enhance the native species that we care about. Based on this body of grasslands research, we
believe that some ecological sites, like the Sandy Alluvial Flats site, have a
greater potential to support native plants than do other sites (like the
Sloping Loamy Sands site). Understanding
ecological sites provides us information to consider where we prioritize our scarce management resources within the
large area of Tejon Ranch to get biggest native grassland biodiversity bang for
our buck. This research also gives us information on how to manage grassland biodiversity. We believe that in some cases the high
abundance of nonnative grasses depresses habitat quality for not only native
plants but some native animals as well.
We are currently working with the grazing lessees at Tejon to utilize
livestock as a management tool to help remove dense nonnative grasses in those
ecological sites that support high native plant potential to improve grassland
habitat quality.
Keep in mind that these are management experiments – we must
document whether the proposed managed grazing regime achieves our conservation
objectives or not. However, we feel that
5 years of grassland research has provided us with a strong science foundation
rationalizing these experiments, and we’ll learn about their efficacy from our
long-term monitoring. Stay tuned as we
continue to learn more about our grasslands and how to manage them!!
