Grassland productivity across brittle environments
by Jim Howell
These photos demonstrate differences in standing biomass, ground cover, and stock density in highly brittle environments with different levels of biological productivity.
The properties shown are managed under planned grazing. Stock densities are very high relative to conventional management. Slide captions provide details.
Click a header to see an enlarged row or column with captions. Click a picture to see a larger captioned version, or view the full-size chart with captions (223 K).
| Large table (223 K) | Stock density | Growing season | Dormant season | Soil surface in dormant season |
|
Cold temperate steppe (low production) 14" (360 mm) precipitation, western Colorado, U.S.A. |
 slide 1 |
 slide 2 |
 slide 3 |
 slide 4 |
|
Mild temperate steppe (low production) 12" (300 mm) precipitation, southern New Mexico, U.S.A. |
 slide 5 |
 slide 6 |
 slide 7 |
 slide 8 |
|
High rainfall tropical savanna (high production) 35" (890 mm) precipitation high veld, Zimbabwe |
 slide 9 |
 slide 10 |
 slide 11 |
 slide 12 |
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
© 2003
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 howelljd@scranchtours.com.
Related articles and links
- Managing productivity in brittle grasslands by Jim Howell (slide show). Grazing management, biological productivity, and landscape management issues on high- and mid-rainfall tropical savannas, plus mild temperate and cold steppes.
- Brittleness: why management that helps some landscapes harms others (articles). If brittleness is new to you, start here.
- How can grazing heal land? A short introduction to the basics, with photos
Updated 30 April 2003
URL: managingwholes.com/photos/howell1/index.htm
