Structure and Functioning of a Managed Grassland Ecosystem
Exercise B: Biomass of below ground vegetation

EQUIPMENT

Field

• tapes
• random number tab for locating sampling points
• polythene bags
• soil corers (Ideally, use a section of 5 cm diameter steel pipe with a sharpened cutting edge; plastic pipe and food tins will fracture or distort when twisted or hammered into the ground. Alternatively, a square of metal can be placed on the ground and vertical cuts made round the sides with a knife.)

Laboratory

• knife
• 2 mm sieve
• bucket
• paper bags
• balance
• drying oven

Reagents

Water softener (e.g. Calgon©)

METHODS

Field procedure

• Five cores, each 10cm deep and located at random from each side (mown and unmown) of the research area, are taken and placed in labelled bags.
• Soil cores should be pushed out of corers from the bottom, otherwise the sample will get jammed.
• The internal diameter of the corer is noted.

Laboratory procedure

• The green material is sliced off, with as little of the soil/root as possible.
• The cores are separated into 0-5, 5-10 cm depths.
• Each section is broken up into pieces smaller than a sugar lump and placed in a labelled container.
• A teaspoon of water softener is added to disperse the clay and the sample is just covered with water and left for 30 minutes.
• After checking that the lumps of clay have broken down, the material is carefully washed through a 2 mm sieve into a bucket, and stones, etc. are picked out.
• For more accurate (but laborious) determination of fine root biomass the sieve washings can be ‘panned’ by stirring to suspend the plant material, allowing a few seconds for sand/silt to settle and then decanting through a 0.25 mm sieve. This material is then washed into a tray of water to remove non-root material.
• The plant material is drained well and placed in paper bags for drying at 85°C for 24 hours.
• The dried material is weighed.

Data handling and statistical techniques

• The mean mass of roots in g m^-2 and standard errors for samples at different depths from mown and unmown areas are calculated.

Timetable

Field sampling and laboratory work can be carried out in 2 hours. Dried material is weighed the following day.

SPECIMEN RESULTS

Dry weight per unit area of below ground vegetation

The root biomass from the mown area is mainly fine grass material, whereas the unmown plot has a larger mass of rhizomes and coarse roots, distributed to greater depth.

DATA INTERPRETATION

There are significantly more roots in the unmown area than the mown area. This is because there are more plant species with robust rooting systems (perennial herbs, etc.) in the unmown area and the soil is less nutrient rich.

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