1.TITLE
1.1 DATASET IDENTIFICATION
Stomatal Resistance
1.4 Revision date of this document
15 Feb 93
2.INVESTIGATORS
2.1
Principal Investigator
Dr Simon J. Allen
2.2
Title of investigation
Water use by vegetation in the Sahel
2.3
Contacts
2.3.1
2.3.2
2.3.3
2.3.4
2.3.5
Dr C.J. Holwill
Institute of Hydrology, Wallingford, England
(0491) 38800
CAJH@UK.AC.NWL.IA
(0491) 32256
2.4 Requested form of acknowledgement
Funding from the Overseas Development Administration is gratefully
acknowledged.
3 INTRODUCTION
3.1 Objective/Purpose
To determine the evaporation from the herbaceous substrate at the
fallow site
3.2
Summary of parameters
Stomatal resistance from the herbaceous substrate and underlying
soil
3.3
Discussion
4. THEORY OF MEASUREMENTS
5. EQUIPMENT
Evaporation chamber measuring relative humidity and temperature
5.1.3 Key Variables
Stomatal resistance
5.1.4 Principles of operation
Stomatal resistance (and hence evaporation) can be calculated from
the slope of vapour density
v time
5.1.6
Manufacturer of instrument
MP1000 Rotronic temperature and humidity probe
Campbell Scientific Inc
14-20 Field St
Shepshed, LEICS
ENGLAND
Tel: 01144509601141
Chamber:
Institute of Hydrology
Wallingford,
England
Tel: 0491 38800
5.2
Calibration
5.2.1 Specifications
5.2.1.1 Tolerance
Temperature:
Input range -40 to 60 deg C
Precision 0.1 deg C
Humidity:
Input range 0-100%RH
Precision < 0.5% RH
5.2.3 Other calibration information
6.PROCEDURE
6.2 Spatial Characteristics
6.2.1 Spatial coverage
Ten measurements of 0.6*0.44m each at Southern Supersite at fallow
site.
6.2.2 Spatial resolution
Point measurements
6.3
Temporal Characteristics
6.3.1 Temporal coverage
On a number of runs, each lasting for 2/3 days ie no continuous
collection throughout SOP
6.3.2 Temporal resolution
2-hourly intervals on days of measurement during daylight hours
7. OBSERVATIONS
7.1 Field notes
Fallow measurements were made outside the WAB but as close to the
WAB as possible. Data
taken over the herbaceous substrate may be affected by long
shadows from nearby bushes
during the early evening, and to a lesser extent in the morning.
Dew in the morning also
affects the measurements
Each set of data refers too a specific plot, and the mean and
standard error of the mean are
also given for all the plots. Associated with each plot are the
leaf area measurements which
were determined at the end of the run. These are given as a
separate dataset. The numbering
of the leaf area plot measurements corresponds directly to the
numbering of the 10 areas in
this file.
8. DATA DESCRIPTION
8.2 Type of data
1 observation date
2 time of observation
3 stomatal resistance #1
4 stomatal resistance #2
5 stomatal resistance #3
6 stomatal resistance #4
7 stomatal resistance #5
8 stomatal resistance #6
9 stomatal resistance #7
10 stomatal resistance #8
11 stomatal resistance #9
12 stomatal resistance #10
13 mean stomatal resistance #1-#10
14 standard error of mean
15 revision date
0-3000
0-3000
0-3000
0-3000
0-3000
0-3000
0-3000
0-3000
0-3000
0-3000
0-3000
0-3000
s/m
s/m
s/m
s/m
s/m
s/m
s/m
s/m
s/m
s/m
s/m
s/m
(MISSING = .)
8.3 Sample database record
12SEP92 14:15 103.3 132.2 145.3
110.8 34 15MAR93
99.2 102.1 145.8 123.5 89.9 78.9 88.9
8.4 Data format
OBSERVATION DATE:
observation was made in the
column contains the date on which the
format DDMMMYY
OBSERVATION TIME:
column contains the time when the
observations were made, in GMT,
in the format HH:MM
STOM
STOM
STOM
STOM
STOM
STOM
STOM
STOM
STOM
STOM
RES#1
RES#2
RES#3
RES#4
RES#5
RES#6
RES#7
RES#8
RES#9
RES#10
Stomatal
Stomatal
Stomatal
Stomatal
Stomatal
Stomatal
Stomatal
Stomatal
Stomatal
Stomatal
resistance
resistance
resistance
resistance
resistance
resistance
resistance
resistance
resistance
resistance
for
for
for
for
for
for
for
for
for
for
plot
plot
plot
plot
plot
plot
plot
plot
plot
plot
#1 (s/m)
#2 (s/m)
#3 (s/m)
#4 (s/m)
#5 (s/m)
#6 (s/m)
#7 (s/m)
#8 (s/m)
#9 (s/m)
#10(s/m)
MEAN RES
(s/m)
Mean stomatal resistance for all plots
STD ERR RES
Standard error of MEAN RES (s/m)
REV DATE
revision data for the data
9. DATA MANIPULATION
10. ERRORS
Presence of dew during early morning measurements may have an
effect on the measurement.
11. NOTES
12. REFERENCES
12.2 Journal Articles and Study Reports
W. Koshiek (1981) A rapid-circulation Evaporation Chamber for
measuring bulk stomatal
resistance. J. Appl. Met., 20, 42-52
Ground Station Documentation
1.
INVESTIGATOR
1.1
Dr Simon J. Allen
1.2
Dr Catherine J. Holwill
1.3
16/02/93
1. Stomatal Resistance
2. STATION IDENTIFICATION AND LOCATION
2.1
Southern Supersite Fallow Bush.
Nearest village = Sadore
2.2 Station Code
2.3 Latitude
13 14.63'
2.4 Longitude
2 14.65'
2.5
Altitude
250m
2.6 Super Site and WAB
SS
3. Data Acquisition
10 aluminium bases were positioned in two parallel rows of five
approximately 1-2m apart close to
the WAB.
Measurements were taken over each of the ten bases at twohourly intervals. The chamber
is lowered directly onto the area marked by the base and remains in place
by virtue of its weight.
Between the base and the bottom of the chamber is a layer of insulating
material which keep the
system as airtight as possible. The fans remained on continuously
throughout the series of
measurements and logging of the humidity and temperature data was carried
using a Campbell 21x
logger. Each measurement lasted approx 2 minutes and in between
measurements the temperature
and humidity were allowed to return to their normal values.
At the end of the measurement period ie after up to 3 days of data had
been collected in this manner,
the vegetation enclosed by the bases was then cut by hand and the leaf
area, fresh weight, and later,
dry weight then determined. This data is given in a separate dataset and
refers dirctly to these
measurements.