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Grassland productivity across brittle environments
by Jim Howell
The properties shown are managed under planned grazing. Stock densities are very high relative to conventional management. Slide captions provide details.
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All images copyright Jim Howell
Although all three environments are brittle, differences in biological productivity require different management of the tools of grazing and animal impact.
In low-production environments, plants may require long recovery periods between grazings due to typically slow (in the cold environments) or very erratic (in warmer environments) growing conditions. It is relatively easy to produce widespread overgrazing of plants when animals return too soon. Plants must recover to the point that sufficient material is present to both feed the animals and replenish the litter that protects the soil surface.
With slow or erratic growth, plants and soil surfaces take a long time to begin suffering from excessive rest, or overrest, compared to high-production environments. Because forage quality is usually high, and because mature soil caps are not usually present, very high stock densities are generally less critical to achieving a well-disturbed soil surface and even level of forage utilization. Nonetheless, the bigger and more concentrated the herd, the better for overall ecosystem process functioning
In contrast, plants typically grow so fast in high-production environments that overgrazing is less of a problem. Vast amounts of low quality forage usually ensure an adequate supply of litter, but plants must be eaten or trampled down before the next growing season or they become a major liability. So do undisturbed soil surfaces, which can develop a thick algae cap in just one season. Dealing with these two major challenges requires very high stock density and heavy animal impact every year. See my landscape brittleness and productivity article for more information.
-- Jim Howell
Jim Howell and his wife Daniela ranch outside Montrose, Colorado, U.S.A. They run tours of holistically managed farms and ranches around the world. Jim also writes a regular column for Holistic Management In Practice magazine. Contact him at firstname.lastname@example.org.
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