Oct 17, 2009

Field Trip to Atwell Island and Kaweah Oaks Preserve

As part of the California Invasive Plant Council Symposium I went on a field trip to Atwell Island, owned by the Bureau of Land Management, and the Kaweah Oaks Preserve, owned by the Sequoia Riverlands Trust. Both of these sites are in Tulare County, west of the Sierra between Fresno and Bakersfield in the Valley.

Given that Atwell Island is in a very dry area, even for the Valley, you might wonder how it got its name. The site was once part of Tulare Lake, an important wetland for birds, fish, and other wildlife. As part of the Pacific Flyway, Tulare Lake offered migrating birds a needed respite on their journey over the Valley. Management today aims to restore critical habitat for the San Joaquin kit fox, the Tipton kangaroo rat, the blunt-nosed leopard lizard, and one other lizard that I can't remember.

The area has changed dramatically since the reign of Tulare Lake, which was drained for agricultural use like many wetlands. Water diversions are used for irrigation, timing and directing the release of water to suit water-sucking crops such as cotton and alfalfa. Deep wells have also been sunk to extract groundwater, causing subsidence as well as ensuring that there is no water lingering at the surface in this former wetland. Irrigation methods leave much of the soil laden with salt, eventually driving them out of productivity.

The Atwell Island project reclaims retired farmland for restoration of critical habitat. Our tour of the site was amazingly instructive, particularly if you are interested in the intersection of agriculture and conservation. The land managers cannot convert all of the site at once, in part because they don't have enough seed to propagate native plants on all 7,000 acres at once. So they move slowly, converting about 400 acres per year at the moment. So there are still many fields with crops, such as alfalfa. They also used timed grazing to keep shrub density at a level that is suitable for the small focal species, which need a fair bit of bare ground (a common feature of desert habitat).

One of the coolest things about exploring the shrubs was finding a correlation between their genera and those found in salt marsh. Though the Atwell Island shrubs are in a very dry environment, they share with salt marsh plants a high tolerance of salt. I met these genera (Sueda, Atriplex) last fall in salt marshes in the Norfolk Broads. Seeing new species of them in a completely different environment was incredibly cool (despite the hot, dusty day).

I was really impressed by the whole project, especially when I heard about the efforts to reach out to the local community. The project has resulted in the hiring of a teacher through the summer months to work with local kids on science and environmental education. The use of grazing retains a culturally relevant use of the land, often important in generating local support. The development of a wetland site will create an amazing opportunity for local people to enjoy local and migratory wildlife, as well as a spot that isn't perpetually dry and dusty. I can't wait to go back when they have more of that element in place.

The Kaweah Oaks Preserve is a 320 acre gem of oak woodland, open pasture, and riparian habitat. In contrast to Atwell, a non-profit owns and manages the preserve, employing grazing and fire to maintain habitat values. Here the bedrock is much closer to the surface, keeping the water table higher. This has allowed the persistence of the oaks and riparian plant-life. The rarity of this habitat in the area makes it all the more important to the local wildlife.

Our tour explored the use of herbicide and biocontrol to manage invasive plant species. I felt like I learned a great deal about biocontrol, though I'm still not an advocate. I was stoked to hear that most efforts employed prescribed burns and timed grazing. Again the management kept a culturally relevant activity on the land, and the manager clearly had a great relationship with the farmer.

We saw some really amazing grasses, including clonal perennials and saltgrass. The latter has visible salt crystals on the blades, enticing grazers and eliminating the need for a manufactured salt lick. The shade of the oak groves gave us a fantastic break from the sun and dust as well as a chance to hear some really loud, persistent birds. We saw a migration of turkey vultures overhead, at least 25 of them soaring on thermal gusts very high in the sky. In the mix was a red-tail hawk according to the clever birders carrying binoculars.

This preserve is open to the public and I recommend it if you're in the area. Check the website for details. The land manager was really helpful after the tour when we asked him about getting into Sequoia National Park. He recommended the Lakes Trail, which we hiked on Sunday. It was a great call, backed up by park staff at the visitors center, who called it "the best trail in the park". I'll put pix up from that hike in a day or so.

1 comment:

Eric said...

Nice post - I was browsing the BLM site and having a hard time finding info about Atwell Island. Thanks!