Sampling Vegetation Attributes - Natural Resources Conservation ...
Sampling Vegetation Attributes - Natural Resources Conservation ... Sampling Vegetation Attributes - Natural Resources Conservation ...
102 METHODS—Double Weight Sampling J. Double-Weight Sampling 1. General Description This technique has been referred to by some as the Calibrated Weight Estimate method. The objective of this method is to determine the amount of current-year above-ground vegetation production on a defined area. The following vegetation attributes are monitored: • Peak standing crop, which is the above-ground annual production of each plant species • Species composition by weight It is important to establish a photo plot (see Section V.A) and take both close-up and general view photographs. This allows the portrayal of resource values and conditions and furnishes visual evidence of vegetation and soil changes over time. 2. Areas of Use This method can be used in a wide variety of vegetation types. It is best suited to grasslands and desert shrubs. It can also be used in large shrub and tree communities, but the difficulties increase. 3. Advantages and Limitations a Double-weight sampling measures the attribute historically used to determine capabilities of an ecosystem. b It provides the basic data currently used for determining ecological status. c Seasonal and annual fluctuations in climate can influence plant biomass. d Measurements can be time-consuming. e Current year’s growth can be hard to separate from previous years’ growth. f Accurate measurements require collecting production data at peak production periods, which are usually short, or using utilization and phenology adjustment factors. g Green weights require conversion to air-dry weights. h In most areas, the variability in production between quadrats and the accuracy of estimating production within individual quadrats requires the sampling of large numbers of quadrats in order to detect reasonable levels of change. 4. Equipment The following equipment is needed (see also the equipment listed in Section V.A, page 31, for the establishment of the photo plot): • Study Location and Documentation Data form (see Appendix A) • Production form (Illustration 22) • Sampling frames or hoops • One stake: 3/4- or 1-inch angle iron not less than 16 inches long
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- Page 62 and 63: D. Daubenmire Method METHODS—Daub
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- Page 91 and 92: METHODS—Point Intercept Examples
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- Page 118 and 119: Record weights of all plants within
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- Page 122 and 123: Use the following table to convert
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- Page 128: Study Location Notes Illustration 2
- Page 131 and 132: METHODS—Visual Obstruction—Robe
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- Page 138 and 139: VI. GLOSSARY OF TERMS A GLOSSARY ac
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- Page 146 and 147: VII. REFERENCES REFERENCES Barrett,
- Page 148 and 149: REFERENCES Floyd, D.A. and J.E. And
- Page 150 and 151: REFERENCES Mack, R. and D.A. Pyke.
- Page 152 and 153: REFERENCES Robel, R.J., J.N. Briggs
- Page 154 and 155: REFERENCES ———. 1981. Arid la
- Page 156 and 157: APPENDIX A APPENDIX A Study Locatio
102<br />
METHODS—Double Weight <strong>Sampling</strong><br />
J. Double-Weight <strong>Sampling</strong><br />
1. General Description This technique has been referred to by some as the<br />
Calibrated Weight Estimate method. The objective of this method is to determine<br />
the amount of current-year above-ground vegetation production on a defined area.<br />
The following vegetation attributes are monitored:<br />
• Peak standing crop, which is the above-ground annual production of each plant<br />
species<br />
• Species composition by weight<br />
It is important to establish a photo plot (see Section V.A) and take both close-up<br />
and general view photographs. This allows the portrayal of resource values and<br />
conditions and furnishes visual evidence of vegetation and soil changes over time.<br />
2. Areas of Use This method can be used in a wide variety of vegetation types. It<br />
is best suited to grasslands and desert shrubs. It can also be used in large shrub and<br />
tree communities, but the difficulties increase.<br />
3. Advantages and Limitations<br />
a Double-weight sampling measures the attribute historically used to determine<br />
capabilities of an ecosystem.<br />
b It provides the basic data currently used for determining ecological status.<br />
c Seasonal and annual fluctuations in climate can influence plant biomass.<br />
d Measurements can be time-consuming.<br />
e Current year’s growth can be hard to separate from previous years’ growth.<br />
f Accurate measurements require collecting production data at peak production<br />
periods, which are usually short, or using utilization and phenology adjustment<br />
factors.<br />
g Green weights require conversion to air-dry weights.<br />
h In most areas, the variability in production between quadrats and the accuracy<br />
of estimating production within individual quadrats requires the sampling of<br />
large numbers of quadrats in order to detect reasonable levels of change.<br />
4. Equipment The following equipment is needed (see also the equipment listed in<br />
Section V.A, page 31, for the establishment of the photo plot):<br />
• Study Location and Documentation Data form (see Appendix A)<br />
• Production form (Illustration 22)<br />
• <strong>Sampling</strong> frames or hoops<br />
• One stake: 3/4- or 1-inch angle iron not less than 16 inches long
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