Drought, Plants, Watersheds and Rangeland Health
Gene Gade, University Extension Educator, Crook CountyDrought has negative impacts on nearly all aspects of range livestock production and it is a
major stressor on the rangelands themselves. Droughts vary in frequency, severity and
duration, but they are an expected occurrence in the western United States. Native plants of
the region have to be adapted to cope with drought. However, the soil-water-plant complex is
the basis of the entire livestock enterprise. Use of these basic resources by domestic livestock
must be carefully managed during drought stress periods to avoid damaging them.
The short-term goal – Maintaining plant health during the drought: Drought can reduce
plant production by 50% of more from the average annual yield. Drought-caused reduction of
available feed is an immediate, but, hopefully, short-term problem for ranchers and wildlife
managers. If forage plants are allowed to retain enough photosynthetic capacity (i.e. leaf
tissue) to provide for their own needs during drought, most plants will survive and return to
normal production when precipitation is again adequate. Range grasses must have healthy
root systems to absorb available water efficiently, whether it is near the soil surface or deeper in
the soil profile. Most grasses must replace about 30% of their roots annually and removal by
grazing of the above ground parts of a grass have been shown to cause proportionate
reductions in the root system. Grasses that have been too severely grazed tend to have
stunted root systems and are less able to compete with neighboring plants to make use of soil
water that is present. Thus, over-grazing makes it even more difficult for plants to survive
drought and recover when it is over.
The long-term goal – Maintaining ecosystem and watershed health: Forage supply and
forage demand cannot remain out of balance for very long. If grazing demands on drought-
stressed plants remain at pre-drought levels, the health, vigor and productivity of desired forage
plants may be further reduced. The most palatable and productive plants may be damaged or
even killed by prolonged, severe grazing. The probable ecological result is that less
productive, unpalatable, or even poisonous plants will increase in abundance or that non-native
weedy plants will invade the range.
The watershed goal should be to increase or maintain water infiltration (absorption) into the soil,
rather than over-land flow (run-off). The best way to accomplish this goal is to maintain a
healthy plant community and plant residues on the surface. However, if drought and/or poor
grazing management results in less plant cover, soil erosion may be greatly accelerated.
Moderate erosion is likely to reduce water-holding capacity of the soil and its ability to support
desired plants. Severe erosion may even lower water tables, leaving all but the most deep-
rooted plants high and dry.
Such negative ecological changes are often very difficult, expensive, and time-consuming to
reverse. If key species have been lost or if severe soil loss has occurred, a turn-around may
not be possible, even with major technological interventions and drastic changes in grazing
management. Thus, degradation of watersheds and plant communities that began in a drought
lasting a few years, can reduce rangeland health and productivity for periods ranging from
decades to millennia.
Management Keys:
1) Adjust stocking rates, before the inevitable drought, to provide a forage reserve.
2) Make sure forage plants keep enough leaf area to stay healthy and maintain a good root
system. They will remain more productive and recover from drought more quickly.
3) Maintain some plant litter and residue on the surface. Residues protect soil from the
impact of raindrops that dislodge soil particles and begin erosion. It also reduces soil
temperature and evaporation loss.
4) Monitor utilization of preferred forage plants to determine when management
adjustments are needed. Make such adjustments, including some mechanism for
reducing grazing demand, before major damage to plants and soils has occurred.
5) Make range recovery a top priority once the drought breaks. Weed control, seeding or
other range improvements may be appropriate.