Cooperative Extension ServiceU.S. Department of Agriculture
Jeffrey E. Herrick
Justin W. Van Zee
Kris M. Havstad
Laura M. Burkett
Walter G. Whitford
Caryl L. Elzinga
Daniel W. Salzer
John W.Willoughby
Sampling PrinciplesIntroduction to sampling
Sampling
The process of selecting a part of something with the intent of
showing the quality, style, or nature of the whole
Why Sample?
To learn about population or area of interest
Difficult to accurately census
To make inferences about population
To generalize with confidence
Populations and Samples
Population: Complete set of Individuals or entire area that you
want to describe, or make inferences about The set of variables in
the sampling universe
Consists of ALL sampling units
Sample: Subset of the population Subset of sampling units
Sampling units
Choice of sampling unit depends on objectives for sampling What
do you want to know? Why?
Types Points
Transects
Quadrats or plots
Individuals Whole plant
Plant parts
Plant BiomassIntroduction to measuring Biomass on Rangelands
Plant Biomass Terminology
Phytomass
Production
BiomassYield
Browse
Double Sampling Methods
Double_Sampling.xlsxDouble_Sampling.xlsx
Indirect MethodsCapacitance Meter
Electronic capacitance is related to biomass because capacitance
is directly affected by height and density of forage in a plot.
Electronic capacitance must be converted to biomass with a double
sampling procedure like that outlined above. In the regression
equation the capacitance becomes the estimated value.
Rising Plate Meter
The rising plate meter is also a double sampling technique were
some of the plots must be clipped to calibrate the meter. The
height must be converted to biomass with a double sampling
procedure like that outlined above. In the regression equation the
height becomes the estimated value.)
Spectral reflectance
Spectroreflectance curves are measured with a spectrophotometer
and then related to biomass.
Cover, height, and density estimates have also been used to
estimate biomass and have been found reliable in some vegetation
types.
