Field work techniques Flashcards
Vegetation collection
Quadrat Advantages - Closed quadrat allows vegetation to be quantitatively recorded so that data can then be plotted graphically. Closed quadrat is objective so data from different sites can be compared.
Disadvantages - Quadrat can squash vegetation leading to over representation as vegetation spreads out. Difficult to identify different species of plants as we are not ecologists. Large squares are recorded as 4% individually, which may lead to over representation if a plant is only in a corner of a square.
Morphological mapping
Profile advantages - (gradient is recorded along the transect, stratified sampling). A profile shows the smaller variations in a slope that an OS map with 10m variations between altitude won’t show. The profile can be drawn parallel to a series of kite diagrams so that links can be made between plant growth on a transect and the nature of the slope.
Disadvantages - Clinometer is wobbly and hard to obtain the accurate gradient, a suntometer or theodolite is more accurate. Ranging poles which are needed to measure gradient are large and awkward to take with you, instead to similarly sized people can be used.
Fluvial Study
Depth - measured at ten points across the river, but at least ten data points are needed to be able to accurately draw a cross section.
Width - the width of the river must be measured and divided systematically into sites, however the width of the river can change depending on discharge. To improve this also measure the bank width which allows you to calculate the channel capacity before flooding occurs.
Velocity - measured at equal points across the river, comparable at different depths to access current. However, flow meters can often get stuck in turbulent water and gives an inaccurate speed.
Pebble analysis
Callipers are used to measure the a, b, c axis of the rocks (width, breadth, length). The rocks must be returned after to reduce environmental impact. Disadvantages - The same orientation of the rock from when it was picked up must be kept. Powers Shape Index (rounded, very rounded, angular, very angular) is subjective, to ensure consistency the same person should do this every time. In a river pebble study it is impossible to pick up both the smallest and largest rocks so only ‘collectable’ rocks are measured (not fully representative).
Soil Study
Soil moisture advantage - The soil sample is put in a tin foil tray weighed and dried at 1800 degrees Celsius for 3 hours and re-weighed, the difference can be put into a percentage to show moisture.
Disadvantage - Soil moisture can be unrepresentative if its been raining one day and not the next, if soil is collected on different days, making it incomparable.
pH advantage - probe can be used or soil taken back to the lab and pH calculated.
Disadvantage - It can be difficult to see the colour difference in a test-tube to accurately know the pH.
Other disadvantages - a soil pit can only be dug into the B-horizon or until a large rock. A soil auger can often stop at a depth to shallow because of rocks.
Traffic counts/ Pedestrian counts (these are the same apart from for pedestrian count the categories are based on age - it is hard to tell a person’s age from just seeing them)
Advantages - Differentiating traffic into categories helps to show the land use of the area. If the vehicle is stationary then you can record it’s place of origin by looking at the registration plate or a small sellers sticker on the back window, the type of car can also indicate the wealth of the area.
Disadvantages - For the data to be comparable between sites the data needs to be collected at the same time which requires multiple people. The time of day, weather and season will affect the traffic, to reduce the impact of this data should be collected at different times throughout the day. If the traffic flow is fast it is difficult to count and distinguish between the categories so human error is high.
EQI
Advantages - Rates environmental qualities such as litter, noise etc. which allows an average score for each site to be calculated, this quantifies the environmental quality of an area.
Disadvantages - Scoring is subjective, depending on the person who is scorings view (the weather and how busy it is may affect the EQI). To improve this the same person should score each site.
Questionnaires
Advantages - Gives you people’s opinions on an issue. Questions are usually closed this means they are quick with few responses this allows you to put a number on the responses and graphically show the data recorded.
Disadvantages - Often difficult to get enough people to answer questions (especially if weather is bad). Often a particular demographic are happy to answer eg elderly but this does not accurately represent the area.
Photos
Advantages - Visual representation of sites, often gives the reader a better impression of what was being assessed. These can be geo-located onto a base map to show their origin.
Disadvantages - A photo only shows a small area, which may have been chosen specially which means it is not objective.
Noise Levels
Advantages - A decibel counter records urban noise, the average is taken over a minute this gives the average noise level for the area.
Disadvantages - A loud exhaust or rumbling bus could give an unrepresentative value. The time of the day will affect the noise level (peak travel times will be louder)
