68
200··
;?
~
150
0Z
CO
100
- 0
> () 50
0
5
10
15
20
CV of Input Variables (%)
800
700
;?
~
600
0500
0Z
co
400
'0
300··
> () 200
100
0
5
10
15
20
CV of Input Variables (%)
200
;?
~
150
c..
c..
Z
100
co
'0
> ()
50
0
5
10
15
20
CV of Input Variables (%)
tion in the case of the nitrogen balance method and
initial root length density in the case of the rninirhizotron method.
Two important points emerge from these analyses. First, the amount of uncertainty associated with
published estimates of BNPP and NFRP can be,
25
30
25
30
25
30
William K. Lauenroth
FIGURE 4.2. The relationship between
the coefficient of variation (CV) of the
input variables and the coefficient of
variation of the estimate of BNPP by the
biomass method described by Publicover and Vogt (1993).
FIGURE 4.3. The relationship between
the coefficient of variation (CV) of the
input variables and the coefficient of
variation of the estimate of BNPP by the
nitrogen balance method described by
Aber et al. (1985).
FIGURE 4.4. The relationship between
the coefficient of variation (CV) of the
input variables and the coefficient of
variation of the estimate of BNPP by the
rninirhizotron method described by
Hendrick and Pregitzer (1993).
and in most cases probably is, large. This underscores the importance of attempting to assess the
uncertainty associated with all published estimates
of BNPP. This is analogous to always including a
standard deviation or a standard error for every
mean. This or more elaborate statistical analyses