Quantifying Corticolous Arthropods Using Sticky Traps

Summary

We describe a semi-quantitative approach of measuring characteristics of corticolous (bark-dwelling) arthropod communities. We placed commercially manufactured sticky traps on tree boles to estimate abundance, total length (a surrogate to biomass), richness, and Shannon diversity for comparison among tree species.

Abstract

Terrestrial arthropods play an important role in our environment. Quantifying arthropods in a way that allows for a precise index or estimate of density requires a method with high detection probability and a consistent sampling area. We used manufactured sticky traps to compare abundance, total length (a surrogate for biomass), richness, and Shannon diversity of corticolous arthropods among the boles of 5 tree species. Efficacy of this method was adequate to detect variation in corticolous arthropods among tree species and provide a standard error of the mean that was <20% of the mean for all estimates with sample sizes from 7 to 15 individual trees of each species. Our results indicate, even with these moderate sample sizes, the level of precision of arthropod community metrics produced with this approach is adequate to address most ecological questions regarding temporal and spatial variation in corticolous arthropods. Results from this method differ from other quantitative approaches such as chemical knockdown, visual inspection, and funnel traps in that they provide an indication of corticolous arthropod activity over a relatively long-term, better including temporary bole residents, flying arthropods that temporarily land on the tree bole and crawling arthropods that use the tree bole as a travel route from the ground to higher forest foliage. Furthermore, we believe that commercially manufactured sticky traps provide more precise estimates and are logistically simpler than the previously described method of directly applying a sticky material to tree bark or applying a sticky material to tape or other type of backing and applying that to the tree bark.

Introduction

Terrestrial arthropods play an important role in our environment. In addition to being of scientific interest in their own right, arthropods can be both detrimental and beneficial to other trophic levels (i.e., crops, horticultural plants, native vegetation, and food for insectivorous organisms^1,2,3,4). Thus, understanding the factors that influence arthropod community development and abundance is critical to farmers⁵, pest control managers⁶, foresters⁴, plant biologists....

Protocol

1. Placement of a trap on the tree

1. Measure the diameter of a tree at breast height. At breast height in each cardinal direction, for an area the size of the pre-manufactured sticky trap (glue board), use a bark shaver to remove bark until an area the size for the sticky trap is smooth enough to staple the sticky trap onto the tree so that there is no space for arthropods to crawl under the trap. Label the back of the trap using a dark colored permanent marker with the date, trap number, location and other pertinent information.
   1. To trap arthropods, either (a) capture both flying and crawling arthropods, by opening and removing the sides and cove....

Results

Based on the mixed model results, the model that included tree species best explained variation in total arthropod length, abundance, and diversity, neither of independent variables explained substantial variation in richness, although the models that included tree species trapping effort were competitive with the null model (Table 1). In addition, proportion of the tree trapped appears to have no influence on abundance, total length, and Shannon diversity, with only mini.......

Discussion

Although alternative techniques such as suction or sweep nets have been used, most previously published attempts at quantifying arthropods on tree boles used some version of either quantifying arthropods by visually inspecting tree boles in the field, using chemical pesticides to kill arthropods in a specified area then quantifying the recovered arthropods, or placing funnel traps or a sticky substance directly onto the tree^19,23,25

Materials

Name	Company	Catalog Number	Comments
Straight Draw Bark Shaver, 8"	Timber Tuff	TMB-08DS
PRO SERIES Bulk Mouse & Insect Glue Boards	Catchmaster	#60m
Staple gun	Stanley	TR45D