Documentation:Open Case Studies/SOIL/Soil Fauna and Rangelands

Case specific learning outcomes

With the help of a series of guiding questions and the interaction with instructors and your group members, you will be able to:

1. Interpret the results of the long-term cattle grazing experiment.
2. Describe your learning in written format (as individual students) and orally (as a working team).
3. Characterize the soil quality of rangeland soils, with an emphasis on soil biological properties.

Background

Soil fauna play important roles in soil development, soil fertility maintenance, and the decomposition of organic matter in grassland habitat. Decomposition and nutrient recycling are essential soil processes to maintain a healthy and sustainable grassland ecosystem. Soil fauna influence bacterial and fungal biomass via grazing, liberating immobilized nutrients, and stimulating further fungal and bacterial activity, as well as, enhancing plant growth. These organisms may also be useful as bioindicators of soil quality.

The diversity and abundance of soil organisms is influenced not only by available food resources, but also by changes to physical and chemical properties in the soil. Grazing can influence chemical, physical, and biological properties of the soil. There has been little research on soil fauna of grasslands in Canada and almost no research to date on soil fauna in grasslands of southern interior of British Columbia (BC). Furthermore, there is limited research on the impacts of grazing on soil organisms. The purpose of this preliminary survey was to examine possible relationships between soil mesofauna and grazing.

Before the 1970s, the traditional grazing system on rangelands in the southern interior of BC consisted of extended periods of fall and spring grazing without any rest, which resulted in deterioration of the rangeland ecosystems. Seasonal-suitability grazing systems were consequently established in late 1970s to improve rangeland conditions. These systems employ grazing only in late spring or fall on bunchgrass rangelands at middle and higher elevations. To date, the effects of various grazing systems on vegetation changes and animal production have been well documented, while less attention has been given to impacts of grazing on the soil.

The study site was located on the Lac du Bois Grassland Provincial Park (50°45’N and 120°25’W) northwest of Kamloops, BC. Soil of the study site is a Dark Brown Chernozem (soil series – McQueen) loam developed on glacial till. The elevation within the study site is 600-850 m above sea level. The climate is semiarid with an average annual precipitation of 270 mm . Canadian climate normals 1971-2000. Kamloops airport meteorological records, http://www.climate.weatheroffice.ec.gc.ca/climate_normals/. The study sites are located within the Bunchgrass biogeoclimatic zone where dominant vegetation consists of bluebunch wheatgrass (Pseudoroegneria spicata (Pursh) Scribn. & Smith) and big sagebrush (Artemisia tridentata Nutt.).

The grazing experiment, established in 1978, consists of two pastures (replicates). Each pasture is covering an area of 65 ha. The following grazing systems are present on these two pastures:

1. Fall only each year,
2. Spring only each year, and
3. Fall and spring (FS) the same year.

Within each grazing treatment there were two exclosures (25 x 50 m) established to prohibit livestock grazing. All grazing treatments were grazed at 0.6 animal unit months (AUM) per ha-1 (corresponding to 45-50% use of available forage). The fall and spring (FS) grazing treatment had half as many animals (cows and calves) in fall and again in spring as the other two treatments grazed only once per year. The spring grazing period was from mid-April to mid-May, while fall grazing occurred from mid-September to mid-October.

Soil sampling was done 20 years after the experiment was established - in August and October 1998.

Sampling and Analysis

Five soil cores (5 cm in diameter) were collected only from the FS treatment and ungrazed exclosures during late August and early October 1998. Two sampling units were randomly selected within grazed and ungrazed areas. Cores were collected at 0 to 4 and 4 to 8 cm depths. All samples were extracted for one week using a high-gradient extractor and collected in 0.6% picric acid. Samples are stored in 70% ethanol alcohol until examination under a dissecting microscope. All fauna were sorted, counted and identified to the following levels (i) mites to suborder, (ii) springtails to family, and (iii) all remaining fauna to the lowest possible level.

Rangeland Management Practices

One of the primary objectives of the rangeland management is to protect and improve rangeland resources such as vegetation, soil, water, and wildlife. To accomplish this, various management practices are employed. They include:

1. Grazing management
   • Number and distribution of animals
   • Seasonal grazing
   • Fixed animal species grazing
2. Vegetation management
   • Weed control (by chemical, biological, or mechanical means)
   • Seeding of rangelands by either native or introduced plant species
   • Fertilization of rangelands

All of the management practices mentioned above can either improve or degrade rangeland soils and they should be applied according to recommendations developed for a particular region. Rangeland management should be designed in such way that it prevents or reduces soil degradation, specifically, erosion and compaction.

Week One

Learning Objective

• Identify and discuss the soil formation factors focusing on the soil type present on the study sites north of Kamloops, BC.
• Identify the mayor types of soil mesofauna.

Student Tasks

1. Review background information on soil formation, and classification, focusing on the Chernozemic soil order and specific soil at the study site. (i.e., the McQueen soil)
2. Discuss the mayor types of soil mesofauna
3. Share individual learning with group members (ongoing for weeks 1-4).

NOTE: Before next week’s session, your team should research any gaps in knowledge regarding the guiding questions for today’s session.

Guiding Questions

1. What are key properties of Chernozems?
2. What soil properties are of an importance for management considerations on McQueen soil?
3. What is soil mesofauna?
4. What are the key roles of soil mesofauna?

Key References

1. Soils of the Ashcroft Map Area by Young, G., Fenger, M.A., and Luttmerding, H.A. 1992. (MOE technical report no. 23 / BC soil survey report no. 26). [this book is available at http://www.llbc.leg.bc.ca/public/pubdocs/bcdocs/104459/bc26_report.pdf
2. Canadian System of Soil Classification by Agriculture Canada Expert Committee. 1998. (3rd edition) available at http://sis.agr.gc.ca/cansis/publications/manuals/1998-cssc-ed3/cssc3_manual.pdf
3. van Ryswyk, A.L., McLean, A., and Marchand, L.S. 1966. The climate, native vegetation, and soils of some grasslands at different elevations in British Columbia. Can. J. Plant Sci. 46:35-50 [a copy of this manuscript will be sent to you]
4. Brady N.C., and R.R. Weil. 2010. Elements of the nature and properties of soils (3rd ed.). Pearson Education (Prentice Hall), Upper Saddle River, NJ. 624 pp. [chapter no. 10]
5. The Soil Biology Primer, on-line version http://soils.usda.gov/sqi/concepts/soil_biology/biology.html
6. Behan-Pelletier, V.M., Kanashiro, D. 2010. Acari in Grassland Soils of Canada. In: Arthropods of Canadian Grasslands Vol. 1: Ecological Interactions in Grassland Habitats. Shorthouse, J.D., Floate, K.D., eds. Biological Survey of Canada, pp. 137−166.
7. Herrick, J.E., Brown, J.R., Tugel, A.J., Shaver, P.L., Havstam, K.M. 2002. Application of soil quality monitoring and management: paradigms from rangeland ecology. Agron. J. 94:3−11.
8. Behan-Pelletier V.M. 1999. Oribatid mite biodiversity in agroecosystems: role for bioindication. Agriculture, Ecosystems & Environment. 74(1-3): 411-423

NOTE: It might be useful that you view section on Chernozemic soils presented on the following web site http://soilweb.landfood.ubc.ca/classification/chernozem/

Week Two

Learning Objective

• Evaluate the extent of grazing impacts on soil mesofauna.

Student Tasks

1. Review the soil data on mesofauna collected at the Lac du Bois Range (see the attachments). These data were collected as a part of the project funded by the Beef Cattle Industry Development Fund and the Matching Investment Initiative of Agriculture and Agri-Food Canada.
2. Review background information on management practices carried out on the study sites.
3. Gain basic understanding of soil quality concept.

NOTE: Before next week’s session, your team should research any gaps in knowledge regarding the guiding questions for today’s session.

Guiding Questions

1. Based on the data that you received, what can you infer about the effects of grazing on various groups of soil organisms?
2. Which group of soil organisms is the most useful to reflect impacts of grazing on grasslands?

Key References

1. Battigelli, J.P., G.S. McIntyre, K. Broersma, and M. Krzic. 2003. Impact of cattle grazing on prostigmatid mite densities in grassland soils of southern interior British Columbia. Canadian Journal of Soil Science 83:533-535.
2. Linden, D.R., P.F. Hendrix, D.C. Coleman, and P.C.J. van Vliet. 1994. Faunal indicators of soil quality. pp.91-106 In: J.W. Doran, D.C. Coleman, D.F. Bezdicek and B.A. Stewart (ed.) Defining soil quality for a sustainable environment. Proceedings of a symposium sponsored by Divisions S-3, S-6 and S-2 of the Soil Science Society of North America, Division A-5 of the American Society of Agronomy and the North Central Region Committee on Soil Organic Matter (NCR-59), November 1992, Minneapolis, MN. SSSA Spec. Publ. No. 35, Madison, WI.
3. Pankhurst, C.E., B.G. Hawke, H.J. McDonald, C.A. Kirby, J.C. Buckerfield, P. Michelson, K.A. O’Brien, V.V.S.R. Gupta, and B.E. Doube. 1995. Evaluations of soil biological properties as potential bioindicators of soil health. Aust. J. Exp. Agric. 35:1015-1028.

Week Three

Learning Objective

• Identify soil biology quality indicators that could be used to monitor the sustainability of management practices at the Lac du Bois Range.

Student Tasks

1. Develop a soil quality framework for the Lac du Bois range focusing on soil biological properties / attributes
2. Preparation for group presentations.

NOTE: Before next week’s session, your team should research any gaps in knowledge regarding the guiding questions for today’s session. Start preparing for the group presentation and please consult guidelines given in the course syllabus.

Guiding Questions

1. What are potential effects of the soil organic matter on the soil biological properties in general and mesofauna in particular of the site in southern interior of BC?
2. List some soil quality indicators, with emphasis on biological properties that could be used to monitor the sustainability of the management of the Lac du Bois Range.

Key References

1. Linden, D.R., P.F. Hendrix, D.C. Coleman, and P.C.J. van Vliet. 1994. Faunal indicators of soil quality. pp.91-106 In: J.W. Doran, D.C. Coleman, D.F. Bezdicek and B.A. Stewart (ed.) Defining soil quality for a sustainable environment. Proceedings of a symposium sponsored by Divisions S-3, S-6 and S-2 of the Soil Science Society of North America, Division A-5 of the American Society of Agronomy and the North Central Region Committee on Soil Organic Matter (NCR-59), November 1992, Minneapolis, MN. SSSA Spec. Publ. No. 35, Madison, WI.
2. Paoletti, M.G., M.R. Favretto, B.R. Stinner, F.F. Purrington and J.E. Bater. 1991. Invertebrates as bioindicators of soil use. Agriculture, Ecosystems and Environment 34:341-362.
3. Six J, Bossuyt H, Degryze S, Denef K. 2004. A history of research on the link between (micro) aggregates, soil biota, and soil organic matter dynamics. Soil and Tillage Research 79: 7–31.

Week Four

Group presentations and synthesis

Each group will present results of their work on this month’s case (please remember that your presentation should be max 20 minutes long) and along with the instructors compare and contrast the methods of diagnosis and interpretations of soil biological quality in the three case studies:

1. Soil mesofauna on long-term soil productivity (LTSP) study sites
2. Effects of variable retention on soil microorganisms
3. Effects of long-term cattle grazing on abundance and diversity of soil mesofauna in southern interior of BC

The presentations will be evaluated on the basis of content, structure, and delivery.

One of the signs of successful presentation is how well the presentation engages other groups into discussion.