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SWEEP Report #47

Effect of Woodlot Borders and Crop Residue on the Distribution of Invertebrates in Agroecosystems

Researchers: 
P. Neave (with V. Thomas), Department of Zoology, University of Guelph, Guelph, Ont.

Executive Summary

Evaluation Summary (Tech. Transfer Report Summaries)

View / Download Final Report  [666 KB pdf]

Associated SWEEP/LSP Research

 

 

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Completed: May, 1992

Key Words:

soil life, insects, cryptozoic fauna, arthropods, earthworms, crop residue, invertebrates, richness, abundance, occurrence, evenness, woodlot

Executive Summary

This study examined the relationships among distance from woodlots in agricultural fields, crop residue, and the abundance and diversity of soil invertebrates. Two sites were used in southern Ontario. Each site had one field with crop residue over the winter of 1990, and one field without crop residue. Populations of cryptozoic (soil surface) fauna, foliage fauna, and earthworms were measured.

The abundance and richness of cryptozoic invertebrates declined significantly with increasing distance into the fields. The decline in abundance was dependent on date; the greatest decline with increasing distance into the field was in late fall. These declines suggest that cryptozoic invertebrates were present at distances further out into the field, despite their comprising few taxa, and that many of the invertebrates are dependent on the woodlots for winter shelter. Crop residue on the field over winter significantly increased cryptozoic abundance and richness at all distances from the woodlot in some fields, suggesting that crop residue promoted invertebrate persistence in these fields.

The numbers and richness of Carabidae (carabid beetles) increased significantly with increasing distance into the fields in late July and August, particularly in the corn cropping systems. The crop residue appeared to have little effect on carabid distribution.

Evenness of the cryptozoic community increased significantly with increasing distance into the fields. Species dominance therefore appears greater in the woodlot than in the field. Crop residue cover on some fields significantly decreased evenness at all distances from the woodlot.

Earthworm number and mass increased significantly with increasing distance into the fields, possibly because of increased competition from other macro-decomposers which were more abundant near the woodlot.

 

Evaluation Summary

(From Technology Transfer Report Summaries - A. Hayes, L. Cruickshank, Co-Chairs)

The objectives of this report were to examine the effect of distance from a woodlot and crop residue cover on invertebrate abundance and diversity in agricultural fields. There were 2 crop residue (over winter) treatments at each of 2 sites: (1) Mount Forest - silage corn (no residue) and barley with the straw left (residue cover) and (2) Fergus - chisel plowed soybean stubble (no residue) and unplowed soybean residue (residue). Three groups of invertebrates were sampled in 4-5 transects/residue treatment at intervals up to 50 m into the field from the woodlots. The three groups were the cryptozoic invertebrates (live on the soil surface such as spiders, sow bugs, millipedes and slugs), foliage arthropods (found on crop and weed plants such as syrphid flies and ladybird beetles) and earthworms. The roles played by these organisms in agroecosystems include residue decomposition, pest control and nutrient cycling. Invertebrates were sampled using pitfall traps for cryptozoic invertebrates, plastic bags and intercept traps for foliage invertebrates and formalin/hand sorting for earthworms.

Richness (number of taxa in a sample), occurrence (number of taxa found in all samples), abundance (total number of individuals found) and evenness (equatability of distribution of abundance among the taxa) were used to determine the influence of the treatments on the invertebrate populations. The abundance and richness of cryptozoic invertebrates declined significantly with increasing distance into the fields. The decline in abundance was dependent on date with the greatest decline occurring with increasing distance into the fields in late fall. Crop residue on the field over winter significantly increased cryptozoic abundance and richness at all distances from the woodlot in some fields, suggesting the crop residue promoted invertebrate persistence in these fields.

The numbers and richness of Carabidae (carabid beetles) increased significantly with increasing distance into the fields in late July and August, particularly in the corn cropping systems. The crop residue appeared to have little effect on carabid distribution.

Evenness of the cryptozoic community increased significantly with increasing distance into the fields. Species dominance, therefore appears to be greater in the woodlot than in the field. Crop residue cover on some fields significantly decreased evenness at all distances from the woodlot.

Earthworm number and mass increased significantly with increasing distance into the fields, possibly because of increased competition from other macro-decomposers which were more abundant near the woodlot.

This study appears to suggest that large fields may have taxa-poor centres, with several dominant taxa being present in relatively large numbers for part of the year. This is not the ideal situation, as it probably interferes with the natural predator control of pests and with decomposition and nutrient cycling.

Comments:

Interpretation of some of the data was speculative. The results would be more meaningful if there had been more replications of each treatment, particularly since there were different crop residues at each site and different tillage conditions in the no residue treatments as well as different past histories for the sites.

Associated SWEEP/LSP Research:

  • SWEEP Report #30 - The Response of Soil Microflora and Fauna to Spring Plowing of Zerotill and Pasture Soils

  • LSP7016 - Response of the Soil Microflora and Fauna to Spring Plowing of Zerotill and Pasture Soils

Future Research: ( ) indicates reviewers suggestion for priority, A - high, C - low.

(A) There is a lack of information available on soil fauna in agroecosystems. We need to develop sampling protocols and to develop a database of information on soil life as indicators of soil quality.

 

 

 

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Created: 05-28-1996
Last Revised: Thursday, May 19, 2011 03:29:00 PM