I have been asked to be on the panel of speakers for an upcoming presentation on the Napa County Watershed and Oak Woodland Protection Initiative (WOWPI) on March 12. The event is to be sponsored by the League of Women Voters and the Napa Chapter of the Sierra Club.
My working topic is “The Importance of Oak Woodlands to Watersheds.” As an arborist, not a forester or watershed specialist, I have a lot of homework to do. But that is a good thing, considering I am a board member of the Napa County Resource Conservation District (RCD) and I represent the Napa RCD on the Napa County Watershed Information and Conservation Council (WICC). The board of that august body includes some of the council members from Napa County cities, county supervisors, representatives of various agencies, and residents.
For the WOWPI event, I will not be acting as a representative of the conservation district or conservation council, but I intend to provide solid information.
Beginning my self-education on the subject, I went back to the “Napa County Voluntary Oak Woodland Management Plan” to see what it says on the importance of oak woodlands in watersheds. The Napa County Board of Supervisors adopted that plan in October 2010.
Section I, the introduction, briefly explains the significance of the oak woodlands of Napa County, risks from developments and natural hazards, the need for a management plan to preserve and restore them, and the voluntary nature of the plan. It relies on participation by “willing landowners” with various agencies, nonprofits and conservation groups.
Section II gets into the area I have been asked to address: “The Value of Oak Woodlands”. It lists and explains them as follows:
B. Flood Protection
C. Erosion Control
D. Water Quality Protection
E. Air Quality Protection and Carbon Sequestration
F. Plant and Wildlife Habitat
G. Scenic and Public Recreation
H. Enhanced Property Values
I. Viticultural /Agriculture
J. Other: fodder for livestock, fuel/firewood, wood products, spiritual/emotional, and others.
For my assigned topic, the watershed value of oak woodlands, B, C, D, E, and I are of particular importance. Here is a very brief summary of the principles:
B. Flood Protection: Oak canopies hold rainwater temporarily on their leaves and stems, slowing runoff and potential for flooding. Oak woodlands with their deep roots and their naturally improved soils can capture and store more water than do grasslands.
C. Erosion Control: Oak canopies, the natural litterfall of leaves and twigs, and the network of roots and filaments of beneficial fungi prevent erosion by slowing raindrops, and binding soil into stable, structured soil particles that resist erosion and landslides.
D. Water Quality Protection: Because they improve soil structure and reduce erosion, oak woodlands hold soil and potential pollutants like pesticides and fertilizers in place, keeping them out of water supplies.
E. Air Quality and Carbon Sequestration: Oaks and other plants directly reduce ozone pollution by absorbing and destroying it in their leaves. They intercept particulate pollution, and they sequester large quantities of carbon dioxide in the various compounds that comprise woody stems, roots, and soil organic matter, thus countering some of the effects of greenhouse gasses that contribute to global warming. The shade of oak woodlands also reduces ground surface temperatures.
I. Viticultural/Agricultural: The diversity in oak woodlands can help minimize some pests and diseases in adjacent vineyards. e.g. cutting down oaks at the edge of vineyards can increase Armillaria (oak root fungus), which attacks grape vines. (Keeping oaks healthy and living tends to suppress oak root fungus.) Woodland diversity provides habitat for species that prey on some vineyard pests.
That is a brief look at a few aspects of the value of oak woodlands through the perspective of the voluntary plan enacted in 2010. That document runs 49 pages, not including the supporting documents. It deserves a thorough reading by voters.
Then consider the proposed Watershed and Oak Woodland Protection Initiative of 2018.