The Bait-Lamina Test
- General description of the method
- Bait material
- Application areas of the bait-lamina test system
- Comparison of the bait-lamina test with other integrative methods of soil biology
Soil biological investigations are increasingly aimed at the determination not only of characteristic structural parameters of soil ecosystems (e.g. species composition) but also of typical soil functional parameters, like turnover processes.
The integration of functional investigations in soil biological studies facilitates the understanding of processes like dead organic matter decomposition and the meeting of questions related to ecosystem management and soil protection approaches.
Since the effects of pollutants can be demonstrated through the monitoring of selected soil processes, like litter or cellulose decomposition, methods assessing functional parameters are very helpful in soil ecotoxicological studies.
At present the most widely used methods are litter-bag methods and the bait-lamina test. These are so called "integrative methods", since they assess both soil microbial and soil invertebrate activity in the investigated soil layers and do not allow for a differentiation in the role played by different organism groups.
In comparison to the bait lamina test, litter decomposition investigations using litter-bags are very laborious, considering the preparation and the required long exposition periods.
The bait-lamina test system, by terra protecta GmbH, Berlin, Germany consist in perforated PVC-stripes (16 holes) filled with the standard substrate mixture (cellulose, bran flakes, active coal and others- developed in a long process in the field). Through the standardization of the bait-lamina test system it is possible to compare the feeding activity of soil organisms in e.g.
Different ecosystems or under different management tecniques all over the world.
The bait-lamina test system provides in comparison to litter decomposition studies a considerable amount of biometric data, that can easily be treated with statistical tests procedures.
Since 1990, more than 300 investigations presenting results of bait-lamina tests have been published.
General description of the method
Small bait portions (cellulose, bran flakes and active coal) are fixed in holes pierced in PVC strips, that are then exposed to the biological decomposition activity of the soil. Soil invertebrates and soil microorganisms progressively degrade the bait substrate placed in the soil. It is assumed that the disappearence of the bait material is directly associated to the feeding activity of soil invertebrates, even if microbial processes and microbiogenic metabolism may play a minor role.
The general requirement for the bait material is the use of a mixture of natural materials (powdered) that are eaten by soil animals and have enough consistency, elasticity and stability to be placed easily in moist, fine and coarse soil without damage. The bait material mixture, proposed from the terra protectaGmbH, consists of cellulose, bran flakes and active coal. The use of materials from field sites, such as powdered leaves of birch (Betula pendula L.) or different gras species (e.g. Calamagrostig epigaeios L.), has already been employed.
Application areas of the bait-lamina test system
The bait-lamina test has been utilized in several investigations and in very different situations. The most important applications are:
- In ecotoxicological field and laboratory experiments, the bait-lamina test has been used to document the overall effects of chemicals on soil organisms. The pesticide registration authorities in Germany (Biologische Bundesanstalt) is presently examining whether a bait-lamina test is to be included in the registration procedure of new chemicals.
- In forest ecosystems studies the bait-lamina test has been employed to monitor gradients of pollution deposition (e.g. along highways), as well as the impact of pesticides contamination and soil liming. The differences in feeding activity between small experimental sites (litter, grass, ect.) as well as between large cultivation areas could be evaluated by the bait-lamina test.
- In agroecosystems the influence of different cropping systems on the feeding activity of soil arthropods can be investigated by the bati-lamina test. The impact of soil amelioration (fertilizers, manure, ect.), soil cultivation techniques, soil compaction and fungicide application can also be assessed.
- In urban ecosystems studies the bait-lamina has been employed to answer questions related e.g to effects of composts on soil activity, deposition of pollutants along roads and management of polluted sites like sewage farm soils.
- The bait-lamina test can also be utilized in peat ecosystem restoration (renaturalization), research on raw material growth (e.g. Miscanthus), nature conservation (water-meadow landscapes) and in research on global climate change.
To investigate the potential influence of pollutants on soil ecosystems, the effects of chemicals should be evaluated both at the biocenotic level as well as at the level of soil dynamic processes. Besides the determination of the soil arthropods feeding activities, organic matter degradation, soil respiration patterns, enzyme activities, microbial growth and nutrient turnover rates are processes that can be measured and should be selected if an ecological assessment of the impact of chemicals on soil ecosystems is required . The experience gained by now and the standardization of the bait-lamina test system gives soil biologists a method which can be employed in research areas of applied and theoretical field ecology.
Comparison of the bait-lamina test with other integrative methods of soil biology
In comparison to known decomposition-tests (especially cellulose decomposition and litter decomposition in litter-bags) the bait-lamina-test offers following advantages:
- achievement of a high number of biometric evaluable data in a rather short period of time and with low effort.
- no special knowledge concerning test-performance or evaluation is necessary, which means the bait-lamina-test can be conducted by unskilled workers
- there will be no heavy or lasting disturbance of the test-location (soil, vegetation)
- there is a variety of possible modification in the choice of the bait-substrates as well as in the test duration
- in each test not only differences in feeding activity values between two independend investigation sites, but also the vertical distribution patterns of the feeding activity can be assessed.
- the results can be used as screening or reference values for following intensive ecological investigations (e.g. decomposition and mineralisation studies)
- the test-method his highly standardisized and is meets therefore DIN-, ISO-, and GLP-requirements