After living in the San Gabriel Valley for nearly 30 years, I thought I had seen and done everything nearby until I started researching about the forests of California. Partially due to proximity and also thanks to television news covering various fires over the years, nearby forests like Angeles National Forest, Cleveland National Forest, and San Bernardino National Forest are well known.  But the San Dimas Experimental Forest (SDEF) right in my backyard? Until recently I did not even know it existed.

Photo by Kathy Rudnyk

According to the US Forest Service’s Pacific Southwest Research Station, the San Dimas Experimental Forest is the only experimental forest in Southern California. This forest is used to gather data for multiple organizations, such as US Forest Service, USDA, National Atmospheric Deposition Program/National Trends Network, and UNESCO. Established in 1933, it was designed to study hydrology and ecology, but then it grew into many more research opportunities.

Listed as a Biosphere Reserve through UNESCO’s Man and the Biosphere Programme (MAB).  This organization gathers and studies scientific data to investigate just how people relate to their natural environment – a “landscapes for learning”, “experimental ecological reserve” or a “laboratory regions of sustainable development”.  According to the MAB, there are 669 biosphere reserves located in 120 countries all over the world. Of that total number, America hosts 47 biosphere reserves.

Map: Pacific Southwest Research Station – US Forest Service

Since 1982, San Dimas has also been monitoring air quality on the site, with numerous universities gathering information to assist their own research from within a compound built during the Depression focusing upon areas of hydrology, soil science, environmental science, ecology, biology, geography, and geology. Creating a sustainable future using the principals of science is a goal I am very interested in as a horticulturalist – someone who looks to science and art for the best ways to grow and care for plants.

Photo by Kathy Rudnyk

Over 17,000 acres in the San Gabriel Mountains are dedicated to the experimental forest. But the San Dimas Experimental Forest looks nothing like a typical forest filled with acres and acres of large conifers; it’s more of a chaparral, featuring ecological plant communities of coastal sage scrub, oak woodlands on the north and cooler sides of the foothills, with mixed conifers throughout.  Emerald green grass covers the hills in the winter and spring, turning gold at even the hint of summer. In some areas, the forest has transitioned from a native plant community to a grassland community, and now back to a native chaparral plant community.  There are a few riparian areas, and on the north side of the foothills communities of oak woodland plants can be found. The Fern Canyon Research Natural Area is also contained within the San Dimas Experimental Forest.

Recent notifications for prescribed burns occurring within the experimental forest.

One experiment caught my eye was conducted in the winter of 1957 – 1958 under the direction of Director Keith Arnold. The population in Southern California was rapidly growing, dire concern was sounded for additional sources of waters.  To address this challenge, the California Division of Forestry, Los Angeles County Fire Department and the Angeles National Forest agreed to remove the natural riparian woodland within the 875 acres surrounding Monroe Canyon, as it was taking too much water for the surrounding population.  Experimental results helped open up new water opportunities, with chaparral foliage removed on the slopes of the foothills with deep soils.  The area was sprayed according to the 1957 Annual Report by the US Forest Service with silvicides, and it was revegetated with grass seed. Since more water flowed into the streams below, all of the native riparian plants were treated with poisons, and silvicide and sulfur dioxide applications were applied onto the competitive chaparral foliage. According to San Gabriel Valley Tribune, the area was later treated with Agent Orange, a highly toxic herbicide with a long half-life. Rainfall was measured daily around the areas, as well as lysimeters were built, both to gauge the amount of run-off within a designed section of land.

Photo by Kathy Rudnyk

According to a forest ranger who I spoke with during 626 Golden Streets, water experiments are still being conducted even today. Fire has also played a part in the history of the forest, burning most of the site within recent years, providing a new opportunity for research data gathering; pollution has also impacted trees, like the Ponderosa Pine (Pinus ponderosa).

A living laboratory like the San Dimas Experimental Forest is especially important because the impact of the research work has long lasting effects on the future, but I also believe it should also be shared with the public. I applaud the possibility that this beautiful area may eventually be opened to the public, especially after noting the San Dimas Experimental Forest was recently designated as a part of the National Monument.  This may bring valuable funding to preserve some of the early testing facilities.

Hope to see you on the trails and from our local Metro rails soon!



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