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Extension Education: Plant Response Post Drought

by Wyoming Livestock Roundup

Land managers and extension educators talk about the importance of developing management plans, including drought plans. Drought plans should include what to do before, during and after a drought. Have you thought about how plants respond after a year or several years of drought? Hopefully you have and you’ve incorporated it into your drought management plan. If you haven’t, now is the time to learn and to consider integrating some of the following information into your drought management plan.

It’s important to understand the condition and management of rangelands before and during drought will influence how plants will respond following drought. There are a number of variables that influence post-drought plant response. For example, adequate residual plant cover helps to facilitate infiltration of precipitation by minimizing loss of moisture to evaporation. 

Plant response 

Drought causes the reduction of cell wall division and slows the production of chlorophyll, which is critical for photosynthesis. Transpiration and photosynthesis slow, which impacts shoot growth. 

Shoot growth is also influenced by the below ground biomass, or the roots, of a plant and it’s ability to access soil moisture. Seed head production and tillering could be reduced during a drought. 

Plants use existing carbohydrates stored in the roots and crowns of the plant to survive a drought. Plants could die if drought conditions persist.

Post drought

Plant response post drought is influenced by the severity and duration of a drought. Research, out of Fort Keogh, Mont., shows that droughts of one year may have very little impact on forage production in subsequent years.  If there is a one year drought the impact to plants will likely be minimal.  

Additional research showed that it might take three or more years of consecutive drought to show a carry-over of decreased tillering.  

Plants that survive a drought that persists and/or is severe can trick us into thinking the range has recovered. 

How? If plant mortality occurs there is less competition among plants for moisture and nutrients, which can result in above average plant heights and a mass of seed stalk production. 

However, overall forage production is likely less than an average year due to fewer plants growing.

You should carefully consider and plan how you will graze the first year post-drought regardless of the severity and duration of the drought. 

Monitoring after drought

One of your management goals the first year should be to facilitate plant growth and vigor and to leave adequate residual cover to feed back into the process.

There are several tools to use to monitor drought in your area.  

SNOTEL reports provide data on snowpack levels.  These will be important for irrigated lands and water for livestock.  Snowpack levels can change rapidly this time of year depending on temperatures and spring snowstorms, so it is critical that you carefully monitor snowpack and precipitation levels in your area.  

Snowpack levels have little impact on dryland forage production.   

For range pastures pay close attention to timing of precipitation.  Range forage production is directly related to spring soil moisture levels.  The Wyoming State Climate office is a good source for precipitation data throughout the state.  

The University of Wyoming Extension Range team wrote an article earlier this month about critical spring dates and what to do. The critical dates April 1, May 1 and June 1 correlate with the amount and timing of precipitation, the type of plants that grow in our arid and semi-arid climate and determining the capacity of the rangeland in terms of stocking rate.  

Most producers will need to balance their livestock’s use of irrigated and dryland forage to meet nutritional needs in a sustainable and profitable fashion.  Monitoring snowpack and the timing and amount of rainfall will help you estimate your forage base for the coming year. 

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