Introduction to Fall 2014 Ecesis, Volume 24, Issue 3
Over the past twenty years, I have been practicing restoration in California’s varied landscapes from the tidal marshes of the Tijuana Estuary to the Colorado River at the Picacho State Recreation Area, then north into the Sierras and west to the Bay Delta. I would opine that the number one enemy to restoration is compaction. Every successful restoration starts with a plan to re-create what took Mother Nature millions of years to perfect. Often our sites are newly graded areas, cut slopes, fill slopes, old agricultural lands, and decommissioned mines and oil fields. The most common problem is compaction and soil lacking proper structure and nutrients. Finding a balance between the engineers looking for compaction and the agronomist looking for agricultural suitability is a challenge. Most engineers do not allow any organics in the soil profile.
This creates several negative effects for the restoration. Compacted soil not only prohibits active root growth, it also inhibits water infiltration and water retainage. This results in most rainfall disappearing as run-off and creating erosion. Compacted soils do not provide adequate space for storage and movement of air, water, and nutrients for soil animals and root growth. This is why the use of low ground pressure equipment on restoration sites is so relevant — it allows the contractor to implement the project without compacting the soil. In fact, typical heavy equipment will leave the soil compacted and not prepared for the planting and seeding components of the project. A 6 foot, 250-lb. human actually exerts approximately 3.9 psi at the heel of a boot. Caterpillar’s 292 — a 14,000-lb. track steer loader — exerts only 3.5 psi!
What can we do during this extended period of drought to ensure our restoration projects will be successful? We can create healthy de-compacted soils that will allow for infiltration of rain events. Don’t let that rain run-off your site. It’s really not ‘how much did it rain?’ but ‘how much rain did we retain on our restoration site?’
Simply ripping, tilling or disking the soil does not correct the compacted situation without adding compost. How much compost do you need? Consult your local Soil Lab. As a general guideline, for most natives it is a 1% minimum, and ideally if we were to recreate Mother Nature in the Great Plains circa 1800, it would be 5%. With 5% organic matter in the top 8-12 inches of soil, we can build soil structure which will reduce compaction and improve infiltration. With 5% organic compost we can retain approximately 3.35 inches of the rainfall in the root zone (1/3 of southern California’s annual rainfall). That’s 90,000 gallons of water per acre of useable water reserve that would just be run-off on a compacted site. Compost is inexpensive and readily available in our recycle reuse programs throughout the state. So, while you are preparing your habitat restoration project to sustain and thrive during the drought, remember to “retain the rain” on your project site through use of low impact equipment for less compaction and by applying the proper amendments to the soil. — by Mark Girard, President of Habitat Restoration Sciences, Inc.