Restoring a Wet Meadow

Wet meadows are visually appealing landscapes with diverse plant life and natural beauty but are desirable for a number of other reasons:

• They filter runoff water, removing excess nutrients.

• They slow runoff and reduce downstream flooding while providing a large surface for groundwater storage.

• They support diverse plant communities which, in turn, support a wide variety of wildlife with crucial nesting, feeding, and cover areas.

• They provide green forage over a longer portion of the year in our semi-arid climate.

• Perhaps most importantly, wet meadows help mitigate climate change by  carbon sequestration, which involves capturing and storing large amounts of carbon in plants and soil through photosynthesis and the accumulation of organic matter in anaerobic soils. 

Wet meadows are threatened by a number of factors, particularly grazing and trampling which leads to erosion, channel incision, and dewatering of the soil.

When acquired, the BCCER had a meadow with a stream channel through it and some remnants of hydrophytes suggesting it had once been a wet meadow so we set out to restore it.

Hydrology

A wet meadow requires a more dependable water source than provided by California's seasonal rainfall. The upper watershed of this drainage is in a thick deposit of Lovejoy Basalt.  As the lava cooled and hardened, it shrank and fractured, creating what might be visualized as a pile of very coarse gravel on top of the relatively impervious Chico Formation. Rainwater percolating down into the basalt creates a perched aquifer that gradually leaks water to the downstream area well beyond the rainy season.

Management

In 2001, when the BCCER assumed management of this meadow, the stream occupied a well-defined channel, about a foot deep at the upper end of the meadow and 3-4 feet deep at the downstream end.  Most of the rest of the meadow supported upland vegetation, dominated by yellow star-thistle and non-native annual grasses.

Meadow

For management of the meadow, we had two goals in mind: increase the dominance of native herbaceous plants and make the stream channel less like a ditch. For the upland, we began a program of summer mowing (just before star-thistle seeds became viable) and fall burning (after the annuals had sprouted in response to fall rains) coupled with reintroduction of native perennial herbaceous plants as seeds or transplants. For the stream channel, we began to increase channel roughness by adding available obstructions for the water to flow around. 

Woody debris and rocks and were obvious but we also raked in some of the mowed star-thistle and tried to encourage the few existing hydrophytes by subdividing roots or spreading seeds. As the channel became more like a swale, we began introducing "starts" of hydrophytes from other parts of the BCCER.

2024 had relatively high rainfall but the last significant precipitation was in April. In mid-June there was still a wet meadow of 3 acres.

Upper Watershed

We also managed the upper watershed to increase water yield to the meadow. To do this we needed to reduce transpiration.  A logical approach was to decrease the relative dominance of evergreen trees. Most of our rain falls in winter when deciduous plants are inactive, allowing water to soak in and replenish groundwater and aquifers. Evergreen plants, being actively growing, will take up much of the water as it falls. Like many local areas subjected to fire suppression, the vegetation was shifting toward a dominance of canyon oaks with understory trees almost all canyon oaks less than a foot in diameter. We girdled most to allow them to die gradually while other plants assumed their space and sunlight. Larger canyon oaks were left to reduce the amount of carbon dioxide released into the atmosphere. However, in late winter of 2022, an unusual snow storm broke or uprooted many trees, particularly broadleaf evergreens like canyon oaks. Since an uprooted canyon oak will usually keep growing as well as sprouting new trunks from the base, we took advantage of the opportunity by cutting off the uprooted canyon oaks, then periodically removing basal sprouts so the roots would die. So, inadvertently, with help from the storm, we also removed many of the large canyon oaks. We revisit the area regularly to cut or uproot canyon oak seedlings and allow  deciduous seedlings to replace them.

Postscript

In Fall, 2024, the Park Fire ravaged the BCCER. Some effects are obvious: woody structures, including beaver dam analogues, are gone, the vegetation of the upper watershed is mostly killed or top-killed, all vegetation in the meadow burned off. This represents a set-back, but also opportunity: transpiration in the upper watershed is greatly reduced and the canyon oaks are all top-killed, helping us to restructure the ecosystem. Most of the hydrophytes are resprouting, others may have become too hot and need to be replaced. Heavy early rains  on the fire-denuded landscape sent unusually high quantities of water across the meadow, causing some erosion but the dense root systems of the hydrophytes resisted remarkably well. We scurried around, replacing burned-out dams with anything available and even dug lateral trenches to spread the excess water. While it currently looks chaotic,  the wet area of the meadow has, at least temporarily, increased. 

Stay tuned for updates.