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Graphing Techniques
Graphing Techniques
Sampling precision is improved by increasing sample size because data describing the vegetation attribute is collected for a greater proportion of the population. At some point, however, we begin to collect information that is repetitious and additional sampling becomes inefficient.
Rangeland Inventory, Monitoring, and Evaluation: General Principles
Rangeland Inventory, Monitoring, and Evaluation:
General Principles
Introduction | General Principles | Sampling Concepts | Vegetation Attributes
Rangeland Evaluation | Management Applications | Chapter Outline
Methods to Determine Frequency
Methods to Determine Frequency
There is only one general approach to determining frequency and it is based on identifying key species in each quadrat. It does not require that individuals are distinguished or counted. Therefore, variations of the basic method to determine frequency relate to properties of the sample unit and data manipulation.
Data Recording and Calculations to Determine Frequency
Data Recording and Calculations to Determine Frequency
The field sheet to record frequency usually includes a species list and a tally is made for every quadrat where the species is recorded. Only a single tally is made for each quadrat, which represents the presence of the species regardless of its abundance. If nested quadrats are used, more than one column is needed to separately recorded each quadrat.
Frequency
Frequency
Frequency is the vegetation attribute that describes the probability of finding a species within a particular area. The probability is based on the occurrence of that species in a series of sample units. For example, if a species has a frequency of 75%, we expect it to occur in three out of every four quadrats examined.
Rangeland Evaluation
Rangeland Evaluation
Introduction | General Principles | Sampling Concepts | Vegetation Attributes
Rangeland Evaluation | Management Applications | Chapter Outline
Use of Equipment
Use of Equipment
Poorly functioning equipment can jeopardize sample accuracy and sample precision. All measuring equipment, such as scales used to weigh samples for herbage biomass, should be regularly checked to confirm their accuracy. Other sources of measurement error include plastic tapes stretching with use and variations in pace-length among observers.