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Ecosystems

The fieldwork techniques introduced in this section are geared towards a range of different ecosystem settings, ranging from coastal sand dunes to woodlands and inland waters.

When you are using these techniques, why not consider focusing on one of the investigations in the list below:

  • Investigating the effects of a new development on a local ecosystem
  • A ‘what if...?' investigation, for example, if hedgerow x was removed, what would the ecological impacts be
  • Assessing the effectiveness of existing management strategies on an ecosystem and making suggestions for future plans, based on the data you collect
  • Examine local farmland or wasteland as an ecosystem in its own right - what is there already? Why is it like it is? What might change if the land-use changed
  • Seasonal changes, a long term study of an ecosystem and how the changing seasons and abiotic factors affect it
  • Global warming projections - predictions about how global warming might impact on an ecosystem, and what the impacts on human beings might also be
  • Global biomes - think about what you have found out and how your data helps to understand large-scale ecosystems and world biomes

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Sand dune transects

Dune profiles

Sand dune profiling is carried out using the same method as beach profiling.

The aim of dune profiling is to investigate the structure of the dune system from the fore dunes (most recently formed) at the seaward side of the dune system inland through the more mature and established dunes towards the climatic climax community. Usually, at the same time as recording the profile data, the line of the profile is taken as a transect line to investigate vegetation succession.

Succession transects

Aims

  • To examine the physical characteristics of a psammosere, the composition of vegetation species which exists in a sand dune ecosystem, and to investigate how this changes from the fore dunes through to the climax community. A good virtual fieldwork tour can be found on the Geo Resources website
  • To investigate other influences on the vegetation cover, for example management strategies, trampling, abiotic factors such as soils (see section below on soil analysis)
  • In combination with microclimate data, to investigate the distribution and adaptation of particular species
  • To evaluate the effectiveness of conservation strategies
  • To compare sand dunes with a different coastal ecosystem, for example a salt marsh

Equipment

  • Ranging poles
  • Tape measure
  • Compass
  • Quadrats or other sampling equipment
  • Random number tables (if needed)
  • Camera
  • Record sheets

Methodology

  1. Decide on a transect to follow across the dune system from the pioneer dunes towards the climax community. Lay a tape measure out to mark your transect route
  2. Place ranging poles at obvious changes in slope angle, and record profile data as for beach profiles
  3. Use a quadrat to sample the percentage vegetation cover and the frequency / coverage of different plant species at each sample point (a species identification chart or key will be required to identify the species). Typically, a quadrat is a grid of ten squares by ten squares allowing easy approximation of percentage cover. Abundance can also be recorded using the ACFOR scale:
The ACFOR scale for measuring species abundance
  • A = ABUNDANT (greater than/equal to 30%)
  • C = COMMON (20 to 29%)
  • F = FREQUENT (10 to 19%)
  • O = OCCASIONAL (five to nine per cent)
  • R = RARE (one to four per cent)

Figure one: Using a quadrat and species identification charts to calculate vegetation coverage
Figure one: Using a quadrat and species identification charts to calculate vegetation coverage.

  1. Other information may also be recorded along the transect, for example soil temperature, moisture content of soil, soil profiles - organic content, colour and texture, pH, wind speed, salinity. A visual comparison of the organic content of the soil can be made by attaching a strip of double-sided tape to a diagram of the dune profile and attaching a small sample of soil at each sample point (see figure two below).

Figure two: A visual representation of the changing organic matter content of soil across the sand dune ecosystem
Figure two: A visual representation of the changing organic matter content of soil across the sand dune ecosystem. Photo copyright Val Vannet.

  1. Photographs can be taken and used in the write-up to support the data.
  2. A sketch map of the dune system should also be included, annotated with information including natural features, evidence of management and human impact, transect lines.

Considerations and possible limitations

  • It is important to keep the transect on a straight line across the sand dune system and to take a number of profiles across the width of the dunes for comparative purposes
  • The presence of some plant species may be dependent upon the season, and as a result the outcomes of the investigation may vary depending on the time of year
  • Use of percentage cover estimates and the ACFOR scale for vegetation coverage is a judgement rather than exact science, so may be subjective
  • Further guidance can be found on the Fieldwork Knowledge Library website

Using the data within an investigation

  • Profiles of dune system can be drawn and annotated to show morphology
  • Kite diagrams can be used to show vegetation changes along the transect
  • Human impact can be incorporated into the investigation through a study of human use and impact on the ecosystem through, for example, footpath erosion studies, trampling and questionnaires of use
  • An investigation can include an assessment of the management strategies that are in place and the effectiveness of these strategies
  • Secondary data, for example old photographs can help to investigate changes historically over time and used to forecast future change
  • Findings can also be used to inform management suggestions

Dots

Woodland transects

Aims

  • To investigate the effect of light on vegetation growth by using a transect from the edge of a woodland (or a clearing) into a wooded area. A light meter would be used at predetermined intervals along the transect to establish the levels of light penetrating the canopy, and the canopy can also be surveyed by holding a quadrat above your head and estimating percentage cover
  • To compare invertebrate communities along a transect into a wooded area
  • A comparison of deciduous and coniferous woodlands, or of woodlands under different management regimes in terms of factors such as the age and density of vegetation, the diversity of plant/invertebrate/bird/mammal species, light intensity or soil type.
    Vegetation succession transects can be carried out in much the same way as dune transects

Dots

Soil analysis

Aims

  • To investigate changes in soil characteristics and composition across a sand dune profile
  • To compare deciduous and coniferous woodlands
  • To compare woodlands under different management regimes
  • To investigate the impact of afforestation or deforestation on soil quality
  • To compare soils in different ecosystems, for example chalk downland and woodland

Equipment

  • Trowel or spade
  • PH probe and testing kit
  • Temperature and moisture probes
  • Infiltration equipment

Methodology

Soil texture

A small sample of soil should be collected and an identification key used to ascertain the type of soil. Sieves with a variety of mesh sizes can also be used to separate the different components of the soils sample, weigh each and then draw a triangular graph to represent the data. Photos and records should be taken along with a description of flora and soil fauna, and any evidence of human interference.

Soil profiles

A section is dug out of the soil so that the different horizons can be seen. Written descriptions can be recorded of the structure, texture, organic content, colour, and depth of each horizon. Note that horizons usually do not appear as level and distinct as in textbook diagrams - this is due to the effects of water and the activity of soil organisms.

Figure three: A podsol profile

Figure three: A podsol profile

Soil pH

Either an electronic meter can be used or the test-tube and indicator solution method where a soil sample is agitated with barium sulphate, distilled water and pH indicator solution, and compared to a BDH colour chart. Further information on methods of soil pH testing can be found on the Soil.net website.

Soil temperature and moisture

Temperature and moisture probes can be used. Alternatively, a soil sample can be taken in a sealed plastic bag and the moisture content found by weighing and drying out in an oven. Note that electronic probes often give more precise readings, but can be inaccurate if poorly calibrated or the batteries run low.

Infiltration rates

The infiltration rate of different soil types can be compared using an infiltrometer. Sites with different vegetation cover or surfaces subject to different conditions, for example trampled and untrampled can be compared. Also, sites can be examined at different times of the day or year, or before and after rainfall events.

The infiltrometer should be secured firmly into the ground, and water poured into the top of the tube. The rate at which the water infiltrates can be recorded in millimetres per minute. A constant ‘head' of water should be maintained.

If you don't have an infiltrometer, a simple alternative method for measuring infiltration can be found on the Field Studies Council website.

Dots

Invertebrate sampling

Aims

  • To investigate changes in invertebrate species numbers and densities related to abiotic factors, for example along a transect
  • To compare different ecosystems, or ecosystems under different management regimes

Equipment

  • Beating sheets or a sweep net
  • Tray
  • Pitfall traps
  • Identification charts or keys

Methodology

  1. Pitfall trapping is a popular and easy technique, and home-made devices can be used. A pitfall device is set up and left, usually overnight, to be checked the following day. Further information about pitfall trapping
  2. Sweep nets or beating sheets can be used, especially when investigating heavily vegetated areas such as woodland. A net is swept back and forth through the vegetation and the ‘collected invertebrates' can be examined and identified in a tray

Figure four: Equipment that can be used to sample invertebrates in a woodland ecosystem
Figure four: Equipment that can be used to sample invertebrates in a woodland ecosystem.
Photo copyright Anne Vaughan.

  1. Visual observations can be made of the number and species of invertebrates on plants

Considerations and possible limitations

  • It is important to consider the sampling method and the number of traps used, and the location for the traps. If using a sweep net, it is necessary to decide how long to use the equipment for and where
  • Weather conditions may affect results
  • How accurate are any visual observations and identifications made
  • How representative are the results of the whole, parent population of the ecosystem

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Freshwater invertebrate sampling

Aims

  • To investigate the biotic component of the freshwater ecosystem
  • To investigate the effect of the physical characteristics of a river on invertebrates, for example pools and riffles, meanders
  • To investigate the impact of human activities on freshwater ecosystems
  • In conjunction with water quality data, to assess the health of the ecosystem, and to make suggestions for its management

Equipment

  • Waders
  • Nets
  • Trays
  • Plastic spoon
  • ID charts or keys
  • Record sheets


Methodology

  • Kick sampling - A net placed on river bed and the area just upstream is disturbed by a gentle kicking motion with the foot
  • Sweep netting - The net is swept back and forth gently in a figure of eight motion

The sample collected is places into a tray of shallow water, and species can be identified using a chart or a key. More information about these techniques can be found on the Freshwater Biological Association website.

Considerations and possible limitations

  • Access to desired parts of the river may be problematic
  • It is important to consider the sampling method, including the locations chosen for sampling and the length of time to kick or sweep for
  • The accuracy of visual observations and identifications must be taken into account

Using the data within an investigation

  • Data should be used in conjunction with other information, for example with water quality to investigate the impact of human activity on water quality and freshwater invertebrate populations

Dots

Water quality measurements

Aims

  • To investigate any changes in water quality along the course of a river
  • To compare different rivers in different catchments with different land use to determine the impact of human activities on water quality
  • To investigate how water quality is managed

Equipment

  • Thermometer
  • Hatch kits to investigate dissolved nitrates and phosphates
  • Dissolved oxygen digital meter
  • Secchi disc
  • pH meter
  • BMWP scores index

Methodology, considerations and limitations

Sites should be identified using an appropriate sampling strategy. At each site, the following data can be collected:

  1. Water temperature, using a thermometer
  2. Dissolved nitrates and phosphates, using hatch kits
  3. Dissolved oxygen, using a digital dissolved oxygen meter. Alternatively, the Winkler method of estimating oxygen content can be applied. Further information on this technique can be found on the Louisiana University Marine Consortium website
  4. Water turbidity, using a Secchi disc. This is used to determine levels of light able to penetrate the water, and thus the turbidity of the water. The depth to which the circular disc sinks below the surface of the water before it disappears from sight is recorded at each site. A home made device is easy to make, and instructions are given in the local learning section of this website
  5. Water pH. A digital PH meter is the easiest to use, although accuracy can be affected by poor calibration and low batteries
  6. BMWP scores. The Biological Monitoring Working Party score was set up by the Department for the Environment in the 1970s and revised in the mid 1990s. It is used to assess water quality by assigning a score to different invertebrates according to their tolerance to pollution and low oxygen levels. Identification is made to Family level, and no account is taken of species abundance. Species that are least tolerant to pollution and low oxygen levels are given the highest score. Scores are recorded for all species found in a sample, and the average calculated by dividing the total score by the number of taxa found. This gives the average score per taxa, and is thought to be more accurate. The higher the score, the ‘better' the water quality

Considerations and possible limitations

  • When measuring water temperature, it is important to ensure that the readings are not influenced by the temperature of the surrounding air. Shallow or surface readings are more likely to be affected by air temperature
  • Hatch kits used to measure dissolved nitrates and phosphates can be expensive, and small amounts are undetectable

Using the data within an investigation

  • Data can be used in conjunction with land use mapping in the river catchment area to determine the extent to which water quality is affected by different human activities. If water quality samples are taken along the length of the river, it may be possible to connect water quality to specific human activities
  • Secondary information from organisation such as The Environment Agency and Natural England, and local newspaper articles, can be used to link water quality with any existing local water management strategies

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Zone sampling

Aims

  • To investigate temporal variations and zonation of the salt marsh system, from the sea shore inland
  • To investigate the creek system and pans, and their importance to the ecosystem
  • To compare the slob and sward zones in terms of their soils, salinity, vegetation type and cover
  • To investigate the adaptations of different species to the unique abiotic conditions
  • To investigate succession from mud flats to salt marsh (halosere) across a transect
  • To compare salt marshes with other coastal ecosystems, for example sand dunes
  • To study the populations of particular species of plant and marine animals
  • To investigate ‘issues' such as drainage for agriculture, conservation, the effects of oil spills and coastal protection schemes in the area

Equipment

  • Plain paper, pencil and rubber
  • Tape measure
  • Compass
  • Quadrats or other sampling equipment
  • Random number tables if needed
  • Camera
  • Record sheets

Methodology

  1. Decide on a sampling method for assessing vegetation composition, cover and zonation a transect from the slob to the sward zone is often the most appropriate method
  2. Quadrats can be used at pre-determined intervals along the transect to estimate percentage vegetation cover, and a species identification chart or key to identify and record species found in quadrat
  3. Species abundance can be recorded by estimating percentage cover or using the ACFOR scale, where A = ABUNDANT (greater than / equal to 30%), C = COMMON (20-29%), F = FREQUENT (10-19%), O = OCCASIONAL (5-9%), R = RARE (1-4%)
  4. Soil testing may be carried out at suitable sites - perhaps one per distinct ‘zone' to record the organic content, colour, texture, PH and salinity
  5. Human impact can be investigated through transects across footpaths to assess the impact on vegetation cover of trampling and footpath erosion
  6. A sketch map of the marsh system should be included, annotated with physical features such as creeks, hummocks and pans, as well as evidence of human impact and management strategies, for example boardwalks, signs, fencing and bridges. The transect lines studied should also be marked on the map
  7. Photographs can be used to support the sketches and data collected

Considerations: Limitations and validity

  • Safety considerations are very crucial here, salt marshes are dangerous. The soft mud and creeks can cause restrictions to access. Tides can rise more quickly than a person can walk back over the marsh, and the creek system can cut routes off
  • When using quadrats for sampling, it is necessary to decide on the size of the quadrat, the placement of quadrats, the number of quadrats used and the distance between them
  • The time of year that the fieldwork is carried out may influence vegetation cover and plant identification
  • Percentage cover estimates and the ACFOR scale both involve the use of judgements rather than being exact science
  • Using the data within an investigation
  • Kite diagrams can be drawn to show vegetation changes along the transect. A software package which can be used to create kite diagrams and analyse species distribution is produced and distributed by the Hallsannery Field Centre in Bideford, Devon
  • A profile can be drawn and compared to textbook diagrams
  • Human impact and conservation needs or strategies can be incorporated into the investigation. Human use and impact on the ecosystem and management or protection strategies can be described and their effectiveness investigated
  • Questionnaires can be used to investigate human perceptions, usage and impact
  • Secondary data, for example old photographs and maps can help to investigate changes over time
  • Findings can be used to debate and suggest future management options
  • Data can be used in conjunction with other variables to compare differences such as soil characteristics, vegetation cover and species
  • Use the data to compare with another ecosystem, typically a sand dune. The different abiotic characteristics can be used to analyse and explain the unique physical characteristics of each ecosystem

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