Laboratory Exercise - Sampling
Purpose: To demonstrate the tools available for sampling to detect and quantify nematode populations. To test the reliability and precision of sampling procedures.
1. Demonstration of sampling tools and their use. a. Oakfield 2.5 cm diam soil tube - varying lengths and designs, including automatic bagging and foot attachments. b. Veihmeyer sampling tube. c. Auger d. Gasoline powered auger. e. Shovel.
2. Reliability of population estimates. a. Work in pairs. b. Use the 30 cm x 2.5 cm diam soil tube to sample 2 rows of beans. Remove 10 cores of soil from the root zone of the plants as a composite sample. c. Take a composite sample of 10 cores of soil to represent the whole bean field. d. Clearly label your samples and store in an insulated box. e. Class will work together to extract nematodes from soil samples by elutriation and sugar-centrifugation. (Use a standardized quantity of soil). f. Each group will identify and count the predominant species of plant-parasitic nematode in their samples (I hope there is a predominant species, otherwise we will select a microbivorous species). g. Determine the spatial pattern of the selected species in the field from abundance in 2-row samples. h. Determine the reliability of a single composite sample from the field on the basis of the range and variance of individual sample estimates.
3. Sampling nematodes associated with plant tissue. a. Select from the tools provided to obtain a sample of the feeder roots of a tree, a shrub, and a grass. b. Gently wash the roots from the soil and examine the root surface under the microscope for the presence of nematodes. c. Stain the roots in acid-fuchsin/lactic acid and examine them for nematodes on the surface and inside the tissues. What are the problems associated with woody tissues?
4. Water and benthic sampling. a. Obtain a water sample from Putah Creek. Sieve the nematodes from the water and concentrate into a jar in the field. Remember that these nematodes may be active swimmers - does that restrict the techniques you might use? b. Obtain a sample of the bottom deposits from Putah Creek using an improvised dredge. Place the sample in plastic containers. c. Extract nematodes from the benthic sample by Decanting and Sieving. You may need to devise an additional step if the sample is not clear enough for analysis. d. Identify the nematodes in the water and benthic samples at least to Order using the approach suggested by Dr Maggenti.
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