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Quiz

Question

What factors should be of concern to Tim?

Looks Good! He should be reviewing records with all of these factors in mind because each one plays a critical role in affecting vegetation response to grazing. Date of grazing is associated with the plants? stages of growth and growing conditions. Length of the recovery period is determined by frequency of grazing. Intensity of grazing is the critical factor affecting the amount of leaf area and meristematic tissue remaining following defoliation.

To review this concept click on the link Defoliation of Grasses and Broadleaves.

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Question

 A review of grazing records indicates that the pastures in the allotment have been grazed in same sequence for nearly a decade and that the pastures of concern have been grazed heavily in late June to late July of each year. The warm-season grasses are in what stage of growth at this time?

Looks Good! Initiating growth in late May to mid-June, warm-season grasses like prairie sandreed and sand bluestem are mostly in the elongation stage during this period. Most tillers would be in a late-elongation stage by mid-July.

To review this concept click on the link How Perennial Plants Grow.

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Question

With this background information on timing and intensity of grazing and stage of growth of the warm-season grasses, Tim needs to work through a series of questions to develop grazing options that will allow him to achieve his goal of improving rangeland condition. At what stage of growth is removal of the apical meristem (growing point) by grazing most likely to occur?

Looks Good! Internodes are elongated and the apical meristem is elevated and susceptible to removal by even light to moderate levels of grazing.

To review this concept click on the link Defoliation of Grasses and Broadleaves.

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Question

What is the location of new growth for tillers that have their apical meristems removed?

Looks Good! With removal of apical meristem, the tiller will no longer grow. Bud(s) at the base of tiller will be stimulated to begin growing, if growing conditions favor new growth.

To review this concept click on the link Defoliation of Grasses and Broadleaves.

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Question

What are sources of energy (carbohydrate) to fuel new tiller growth?

Looks Good! New tiller growth requires energy in the form of nonstructural carbohydrates (e.g., sugars). Leaf area (i.e., photosynthesis) can be the source of much of this carbohydrate if the level of defoliation was light to moderate; however, carbohydrate reserves may be used heavily if the level of defoliation is moderate to heavy.

To review this concept click on the link Carbohydrates and Defoliation.

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For what purposes are carbohydrate reserves used?

Looks Good! Carbohydrate reserve is the source of energy for the tiller/plant when there is little to no leaf area.

To review this concept click on the link Carbohydrates and Defoliation.

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Question

When does a perennial grass plant store carbohydrates?

Looks Good! Carbohydrates are stored when more carbohydrates are being produced by photosynthesis (source) than what the plant is demanding for growth (sink). Photosynthesis obviously is not occurring when the plant is dormant and the demand for carbohydrates is very high when the tiller is rapidly growing.

To review this concept click on the link Carbohydrates and Defoliation.

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What will the carbohydrate reserve level be for most perennial grasses at the late elongation stage?

Looks Good! Carbohydrate storage in most perennial grasses in the central Great Plains starts following the elongation stage when much of the demand for tiller growth has been greatly reduced. Non-defoliated tillers at this time have a high leaf area and demand is largely limited to the inflorescence and seedhead. Prior to the reproductive stage, grasses generally are using reserves to complement photosynthesis in leaves.

To review this concept click on the link Carbohydrates and Defoliation.

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Question

What will happen to the carbohydrate reserve level immediately after defoliation of the plant, including removal of the apical meristem?

Looks Good! The reduced leaf area and energy required to initiate new tiller(s) will cause a reduction in carbohydrate reserves.

To review this concept click on the link Defoliation of Grasses and Broadleaves.

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Question

By the end of the growing season, what will the level of carbohydrate reserves be for this defoliated grass plant compared to a non-defoliated plant?

Looks Good! A plant with tillers defoliated at late-elongation stage will rely heavily on carbohydrate reserves to support new growth and will have reduced leaf area to produce carbohydrates; therefore, level of carbohydrate reserves will be relatively low. The plant also will be recovering from defoliation during a time of the year when soil moisture is relatively low and daylength is decreasing.

To review this concept click on the link Defoliation of Grasses and Broadleaves.

Figure 1 (Walter Schacht, 2005)

Figure 2 (Walter Schacht, 2005)

Figure 3 (Walter Schacht, 2005)

Figure 4 (Walter Schacht, 2005)

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Question

 Which of the photographs above represent a plant community that has been grazed annually at the late-elongation stage?

Looks Good! There will be heavy use of the desired warm-season grasses during a critical time of their growth cycle resulting in an increase of shortgrasses and forbs.

To review this concept click on the link How Perennial Plants Grow

two grasses with 7' deep roots
two cut bundles of grass with 4' deep roots. A spiny bush is present between the two grasses

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Question

Which of the above sketches best illustrates the below and above-ground relations in a pasture grazed annually at the late-elongation stage?

Looks Good! There will be heavy use of the desired warm-season grasses during a critical time of their growth cycle resulting in an increase of shortgrasses and forbs.

To review this concept click on the link How Perennial Plants Grow

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Question

Tim decides that the timing of grazing needs to be change. He recommends changing the timing of grazing to either the vegetative stage or the dormant season. Why would a change to grazing at the vegetative stage most likely result in an increase in the desired warm-season grasses (i.e., prairie sandreed and sand bluestem) and rangeland condition?

Looks Good! The apical meristem would not be removed; therefore, the grazed tillers to grow. Leaf area would be added rapidly because meristems would remain intact, growing conditions likely would be favorable for growth, carbohydrate reserves likely would be available to support leaf growth. The grasses also would have the remainder of the growing season to grow and recover from grazing.

To review this concept click on the link How Perennial Plants Grow

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Question

Why would the practice of grazing during dormancy likely not negatively impact the desired warm-season grasses and improve rangeland condition?

Looks Good! Grasses are dormant during the winter and the above-ground plant material has no immediate function (some nutrient reserves may be in the stem bases). Leaving above-ground growth to accumulate during the growing season is positive, and removing the accumulated plant tissue in the winter has no detrimental effect.

To review this concept click on the link How Perennial Plants Grow

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