Stemflow Sampling

STEMFLOW

Sampling equipment

Number of stemflow collectors: Eight

Distribution of stemflow collectors on the plot: Strictly random selection of all living stems greater than 7 cm diameter at 1.3 m height

Sampler description: Helical gutters attached to the tree leading to an 80 litre bin

Material of the stemflow gutters: Extruded Silicone rubber gutter. Silicone tubing leads to the collecting bin.

Material of the stemflow bin: Graduated polyethylene 80 litre bin

Method of holding sampler: Stemflow gutter is attached to the tree using silicon mastic and stainless steel screws at upper and lower ends.

Height above ground: 130 cm

Collection

Collection frequency: Weekly

Collection Method: The volume of stemflow in the graduated bin is recorded on the field sheet. A sub-sample of 250 ml is taken from the 80 litre bin in a laboratory cleaned bottle. The remaining stemflow in the bin is carefully poured out around the base of the tree.

When the sampler overflows: If the bin overflows, then the maximum volume of container is taken as the sample volume. Some trees consistently gave large volumes of stemflow and in this case, an overflow bin was installed.

Samples are rejected when: The collector is damaged

There is litterfall in sample

There is ambiguously labelled samples, signs of human interference, recent maintenance or installation work on gutter

Stemflow sample transportation medium: 250 ml collection bottle with clean lid

Stemflow samples are transported to the laboratory by: Courier

Measures against sample contamination

from litterfall: Nylon Filter, 1 mm mesh, placed at the lower end of the gutter

from bird droppings: The bin has a lid which keeps out contamination

from animals / humans: Plot fenced

from algae growth: Storage container is opaque (dark green). Preservatives are not used, weekly sampling is intended to reduce algal growth

Stemflow sample protection measures used, to avoid unwanted biochemical changes during storage between sampling and analysis: Keep the sample in the dark

Cool the sample to < 4 degrees C when it arrives in the laboratory

Weekly sampling is intended to limit biochemical changes.

Cleaning procedures
Initially, the gutters, tubing and collection bins are cleaned prior to installation.
Cleaning procedure: Tap water rinse & brush; 3 distilled rinses, 3 distilled-deionised rinses; air dry.
Subsequently, the gutters and bins are not cleaned. However, after installation or maintenance, the initial four samples are discarded and not analysed.

Pooling of samples
Stemflow volume is measured for each individual sample in the field in the graduated bin.
Stemflow samples are pooled before analysis, in the laboratory in cleaned polyethylene bottles. After each collection the stemflow samples are pooled to 1 composite sample, weighted by sample volume
Contaminated samples are simply left out
Chemical analysis
Precipitation samples are chemically analysed on a weekly basis.
Pre-treatment methods: Filtering, Whatman 45 µm filter paper.
Analysis of precipitation samples comprises the following:

pH and Conductivity pH and Conductivity meters

Ammonium Colorimetrically using the phenol-hypochlorite method (Solórzano, 1967) read on a UV at 635 nm

Molybdate Reactive Phosphorus Acid-antimony-molybdate method (Murphy and Riley, 1962) read on a UV at 880 nm

Calcium, Magnesium, Potassium, Sodium, Manganese, total Aluminium Inductively-coupled-plasma optical-emission spectrometry (ICP). If K <1 mg L-1, potassium was measured by atomic absorption spectrometry (AA)

Chloride, Nitrate, Orthophosphate, Sulphate Ion chromatography (IC), using an anion exchange column and conductivity detection

Alkalinity Gran titration (Mackereth et al., 1978)

Total Nitrogen Digestion and colorimetric measurement (Koroleff, 1973)

Dissolved Organic Carbon UV at 320 nm (Gorham et al., 1985), after filtration through a 0.45 µm filter and calculation by regression equation

Repeat analysis is done on the basis of ion balances & ion ratios, comparing analysis to historical values for the same source. Critical limits are not applied. Following any repeat analysis, the less-unfamiliar-looking result is accepted. No sample is rejected on the basis of analytical results.

Last update: 20-March 2001
This page managed by: Gillian M. Boyle
FERG Research page
The FERG Homepage

Number of stemflow collectors:	Eight
Distribution of stemflow collectors on the plot:	Strictly random selection of all living stems greater than 7 cm diameter at 1.3 m height
Sampler description:	Helical gutters attached to the tree leading to an 80 litre bin
Material of the stemflow gutters:	Extruded Silicone rubber gutter. Silicone tubing leads to the collecting bin.
Material of the stemflow bin:	Graduated polyethylene 80 litre bin
Method of holding sampler:	Stemflow gutter is attached to the tree using silicon mastic and stainless steel screws at upper and lower ends.
Height above ground:	130 cm

Collection frequency:	Weekly
Collection Method:	The volume of stemflow in the graduated bin is recorded on the field sheet. A sub-sample of 250 ml is taken from the 80 litre bin in a laboratory cleaned bottle. The remaining stemflow in the bin is carefully poured out around the base of the tree.
When the sampler overflows:	If the bin overflows, then the maximum volume of container is taken as the sample volume. Some trees consistently gave large volumes of stemflow and in this case, an overflow bin was installed.
Samples are rejected when:	The collector is damaged
	There is litterfall in sample
	There is ambiguously labelled samples, signs of human interference, recent maintenance or installation work on gutter
Stemflow sample transportation medium:	250 ml collection bottle with clean lid
Stemflow samples are transported to the laboratory by:	Courier

from litterfall:	Nylon Filter, 1 mm mesh, placed at the lower end of the gutter
from bird droppings:	The bin has a lid which keeps out contamination
from animals / humans:	Plot fenced
from algae growth:	Storage container is opaque (dark green). Preservatives are not used, weekly sampling is intended to reduce algal growth
Stemflow sample protection measures used, to avoid unwanted biochemical changes during storage between sampling and analysis:	Keep the sample in the dark
	Cool the sample to < 4 degrees C when it arrives in the laboratory
	Weekly sampling is intended to limit biochemical changes.

pH and Conductivity	pH and Conductivity meters
Ammonium	Colorimetrically using the phenol-hypochlorite method (Solórzano, 1967) read on a UV at 635 nm
Molybdate Reactive Phosphorus	Acid-antimony-molybdate method (Murphy and Riley, 1962) read on a UV at 880 nm
Calcium, Magnesium, Potassium, Sodium, Manganese, total Aluminium	Inductively-coupled-plasma optical-emission spectrometry (ICP). If K <1 mg L-1, potassium was measured by atomic absorption spectrometry (AA)
Chloride, Nitrate, Orthophosphate, Sulphate	Ion chromatography (IC), using an anion exchange column and conductivity detection
Alkalinity	Gran titration (Mackereth et al., 1978)
Total Nitrogen	Digestion and colorimetric measurement (Koroleff, 1973)
Dissolved Organic Carbon	UV at 320 nm (Gorham et al., 1985), after filtration through a 0.45 µm filter and calculation by regression equation