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Headwaters

I have the privilege of engaging California's communities with the aspiration of safeguarding the sustenance and well-being that its oak-woodland watersheds and the people that are a part of them provide. This millennia-long integrated relationship of humans and land has parallel histories in other Mediterranean parts of the world. The following blog is the first of occasional installments about working Mediterranean landscapes in California and around the globe. Combined they will explore the concepts of watershed functions, working landscapes and Mediterranean climate, vegetation and management. Join me in experiencing these settings, growing our appreciation for the integrated nature of these landscapes and people, and gaining understanding and tools for our tenure as stewards. - David Lewis, director, UC Cooperative Extension, Marin County

Ghost pines, live oaks, black oaks and madrones, among other trees, make their stand interspersed with annual and perennial grasses at the headwaters of a California watershed. (Photo: David Lewis)

I am standing where stream flow begins, in a nameless tributary of the Russian River to the east of Hopland, Calif. This particular spot and location has been a grazing livestock ranch, primarily sheep, going back more than 100 years (learn more). This is one of thousands of spots in a watershed where water comes to the surface, joins in a channel and starts its path downstream. Many of us have stood at a confluence of two rivers or an estuary where a watershed's outfall meets an ocean. These locations are the stream's or river's end, their terminus. Where I am standing, is the headwaters of a stream system, where water is initially released and visible as a thin, shallow bouncing band.

Watersheds collect, store, and transport water. The transport function is performed by streams and rivers. These are dynamic, pervious channel networks each with a beginning and an end. At any part of the network, the channel is that lowest point in the landscape, stretching from one stream bank to the other, and generally widening in the downstream direction, until the stream mouth empties into another water body. 

At the other end of a network is the channel head, where the channel begins. This is where I am standing. Channel heads are found in small, intimate folds in the landscape. These depressions are referred to by many names — draws, bowls, hollows — the place in hills where the slopes become shallow and coalesce.

Like an amphitheater, the surrounding hillslopes rise around me. Reaching out at shoulder height, I can almost touch these slopes. The mixed oak woodland and interspersed grasslands are in attendance across these slopes. Ghost pines, live oaks, black oaks and madrones, among other trees, make their stand interspersed with annual and perennial grasses blanketing the ground. This mosaic of vegetation is hosted and sustained by the complex mix of marine sediments that have been pushed up, forming these hills, and erosion carving the stream channel. Below the surface are soils one to three feet deep that have developed from the underlying geology.  

It's March 3, 2019, and on the cusp of spring. Between the light breezes, the stream water sings its way downstream. I think back to the intense storms that moved across this part of California the week before and the resulting floods in the lower portion of the Russian River. Those and earlier winter storms soaked into the soil until the soil reached its capacity to hold water. Once the soils were primed, water was released to the channel network. That water is still being released now, days later, and will be for several more months into May or even June. Rainfall for this area and most of California has been substantial, matching amounts not seen since 1983, and definitively ending the nearly five-year drought. This contrast in extremes is the norm for California, meaning the next drought or next flood is only a year away.  

Downstream the Russian River is perennial, flowing year-round. But here at the channel head, flow is intermittent on an annual cycle. Rains begin in the fall, with headwater surface flows starting in late fall or early winter, once soils are saturated. This wetting up process reverses in the spring, until the channel head is dry.  

At some point this year flow in the headwaters will stop. Saturated soils releasing water laterally below the ground surface, will gradually release less and less water to the channel. Trees and grasses will demand more and more water as they leaf out and grow. As soils pores empty of free water, the remaining moisture is held more tightly to soil particles and plant root surfaces through a physical tension. Eventually the channel head will run dry.

While you may not have the opportunity to visit a channel head and experience the place where stream flow starts and stops each year, you are often closer to one than you think. Driving a rural road or hiking in a favorite park or open space will invariably find you crossing one of these unnamed headwater streams. As you do, give a look upstream, from where the water going past you has come. Up the channel into the bowl is one of the channel heads and headwaters for the watershed you are in.

I don't know when I will get to this channel head again. However, this place where surface flow is initiated will be close in my mind, particularly, as I visit the confluences and estuary of the Russian River, during the wet and dry periods and high and low rainfall years to come.

To learn more about these specific watersheds and research conducted in them this article is suggested. If interested in learning how stream flow is generated in California oak woodland watersheds you may want to read this article

Posted on Monday, April 15, 2019 at 9:38 AM
  • Author: David Lewis
Focus Area Tags: Natural Resources

Honey, Let's Go Taste Honey!

Graduate student Yao Cai (right) serves honey at the 2018 Picnic Day activities in Briggs Hall. (Photo by Kathy Keatley Garvey)

Honey, let's go taste honey! Yes, you can do just that at Briggs Hall during the UC Davis Picnic Day on Saturday, April 13. It's free and family...

Graduate student Yao Cai (right) serves honey at the 2018 Picnic Day activities in Briggs Hall. (Photo by Kathy Keatley Garvey)
Graduate student Yao Cai (right) serves honey at the 2018 Picnic Day activities in Briggs Hall. (Photo by Kathy Keatley Garvey)

Graduate student Yao Cai (right) serves honey at the 2018 Picnic Day activities in Briggs Hall. (Photo by Kathy Keatley Garvey)

Want to see honey bees near the honey tasting? Check out the Biological Orchard and Gardens (BOG), located by the Mann Lab, in back of Parking Lot 26.  Here a honey bee is nectaring on five-spot flowers, Nemophila maculata.  (Photo by Kathy Keatley Garvey)
Want to see honey bees near the honey tasting? Check out the Biological Orchard and Gardens (BOG), located by the Mann Lab, in back of Parking Lot 26. Here a honey bee is nectaring on five-spot flowers, Nemophila maculata. (Photo by Kathy Keatley Garvey)

Want to see honey bees near the honey tasting? Check out the Biological Orchard and Gardens (BOG), located by the Mann Lab, in back of Parking Lot 26. Here a honey bee is nectaring on five-spot flowers, Nemophila maculata. (Photo by Kathy Keatley Garvey)

Russet Mites on Tomatoes

Damage to Tomato leaves

Russet mites are most frequently found in outdoor container plantings. This suggests that they're introduced both in potting soils and plants brought into the garden. Use only dependable, high-quality potting medium and plants from a nursery you trust. Don't be afraid to ask if mites have been a problem. Even if they've been dealt with and the plant shows no signs of damage, eggs may still exist in the soil.

 

Introducing beneficial nematodes just as soil temperatures begin to warm and ahead of planting can help destroy eggs that are in the soil and nymphs once they hatch. Apply a second round of vermiculite-carried nematodes if damage to lowest leaves is spotted.

 

Avoid over-fertilizing plants. Mites are attracted to vigorous green growth that comes of too much nitrogen.

 

Periodic releases of predatory mites can blunt infestations, giving you time to deal with them. (Yes, the same spray mentioned below will also kill beneficial mites.)

 

Because of their near invisibility, it's difficult to apply insecticidal soaps to suspected mite infestations. Home-made sprays using garlic, hot peppers, or citrus oils will not usually take down mites but may provide some deterrent. (Because they often arrive in the wind, russet-hemp mites aren't easily deterred.)

Neem oil will repel and kill mites. It should be applied at first signs of damage.

Pyrethrum sprays have proven effective in killing mites but require complete coverage to ensure that none of the microscopic pests are overlooked. Tailor applications to the lifecycle of the mite. Spraying once a week — once every five days in warm conditions — for three to four weeks should cover adults, emerging nymphs, and eggs.

No matter which method you're using, close inspection of plants during treatment is crucial. Use a lens of 14X magnification or larger to see mites gathered at the center of curled leaves, at stem junctures, or in flowers. Don't wait to see how effective one treatment is before continuing or using another. Once infestations spread up plants, it's almost impossible to save the plant.

Don't hesitate to discard entire plants, even if they're not entirely affected. While you're treating affected plants, the mites are hurriedly spreading to others.

Prevent spreading mites. Discard infested plants in plastic bags and dispose of them in sealed garbage containers.

Release Predatory Mites (Phytoseiulus persimilis)

 

Posted on Friday, April 12, 2019 at 12:04 PM

Bugs Reign Supreme at UC Davis Picnic Day

UC Davis medical entomologist Geoffrey Attardo holds one of his images, a tsete fly. He does research on the fly. He also will be showcasing his other images of vectors on UC Davis Picnic Day. (Photo by Kathy Keatley Garvey)

What's a picnic without bugs? When the 105th annual UC Davis Picnic Day takes place Saturday, April 13, thousands of visitors will explore the...

UC Davis medical entomologist Geoffrey Attardo holds one of his images, a tsete fly. He does research on the fly. He also will be showcasing his other images of vectors on UC Davis Picnic Day. (Photo by Kathy Keatley Garvey)
UC Davis medical entomologist Geoffrey Attardo holds one of his images, a tsete fly. He does research on the fly. He also will be showcasing his other images of vectors on UC Davis Picnic Day. (Photo by Kathy Keatley Garvey)

UC Davis medical entomologist Geoffrey Attardo holds one of his images, a tsete fly. He does research on the fly. He also will be showcasing his other images of vectors on UC Davis Picnic Day. (Photo by Kathy Keatley Garvey)

These are the new t-shirts to be offered by the Entomology Graduate Student Association on UC Davis Picnic Day. From left are artists/scientists Ivana Li, Corwin Parker and Jill Oberski. (Photo by Kathy Keatley Garvey)
These are the new t-shirts to be offered by the Entomology Graduate Student Association on UC Davis Picnic Day. From left are artists/scientists Ivana Li, Corwin Parker and Jill Oberski. (Photo by Kathy Keatley Garvey)

These are the new t-shirts to be offered by the Entomology Graduate Student Association on UC Davis Picnic Day. From left are artists/scientists Ivana Li, Corwin Parker and Jill Oberski. (Photo by Kathy Keatley Garvey)

You know how loud cicadas are? Well, doctoral student/nematologist Corwin Parker drew this prize-winning sketch for a EGSA t-shirt: a cicada plugged into an amp.
You know how loud cicadas are? Well, doctoral student/nematologist Corwin Parker drew this prize-winning sketch for a EGSA t-shirt: a cicada plugged into an amp.

You know how loud cicadas are? Well, doctoral student/nematologist Corwin Parker drew this prize-winning sketch for a EGSA t-shirt: a cicada plugged into an amp.

Consider Forsythia

This time of year the show-stopper in our Suisun City front yard is the spring-flowering perennial shrub Forsythia: bold, fragrance-free yellow blossoms crowd its branches before any leaves appear. Flowering branches can be cut and forced. One sees this spectacular plant in local gardens so rarely that passers-by sometimes stop to ask what it is. I remembered it fondly as the first bright roadside accent against the shady evergreen backdrop of North Carolina yards and ordered some from our local nursery.

Genus Forsythia is part of Oleaceae, the olive family. One species is native to southwest Europe; the rest come from East Asia, where some are critically endangered because the plants are harvested for medicine. In our part of the world, many species and varieties--varying notably in height--are available to gardeners. Looking for something to plant in front of our raised front porch for early spring color, and later as a leafy green backdrop for smaller flowering plants, I bought two Monrovia Magical® Gold Forsythia, Forsythia x intermedia ‘Kolgold.' The label says “moderate grower to 5 ft. tall, 4 ft. wide.” Sunny exposure--check, well-drained soil—check, medium watering—check, fertilize before new growth begins in spring—check.

Those plants grew well all right! Bigger than advertised. Forsythia's fountain of long, leafy, branched stems occupied far more space than I expected. They blocked the view from the front porch and arched into flowering space needed by neighboring Lily-of-the-Nile (Agapanthus sp.). All of a sudden pruning, which should be done immediately after bloom, became a necessity.

University of Maine Cooperative Extension produced an excellent video about pruning Forsythia so as to preserve its graceful, arching shape. “How to Prune a Forsythia” is available on YouTube: https://www.google.com/search?ei=hPWnXMSoHoL8tAW-5JP4Cw&q=How+to+prune+Forsythia&oq=How+to+prune+Forsythia&gs_l=psy-ab.3..0j0i7i30l2j0l4j0i7i30j0l2.116708.117421..118343...0.0..0.123.556.0j5......0....1..gws-wiz.......0i71j0i7i5i30.wTtKi92ekgk#kpvalbx=1. I can only imagine the cascade of golden blossoms that would result. Because I have no other sunny spot for my plants, I pruned them into a hedgerow instead--“put them in a box,” as my cousin scornfully remarks. The Monrovia label is more forgiving: “For a formal appearance, shear annually after flowering.” I regret the loss of my Forsythia's natural form, but the hedgerow shape looks nice too.

 

Two photos by Patricia Matteson:

1) Closeup of Forsythia blossoms

2) Blooming Forsythia hedgerow in front of the raised porch

 

Forsythia hedgerow. photos by Patricia Matteson
Forsythia hedgerow. photos by Patricia Matteson

Forsythia blossoms closeup.
Forsythia blossoms closeup.

Posted on Thursday, April 11, 2019 at 10:15 AM

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