UTILITY OF GROUND BEETLES (COLEOPTERA: CARABIDAE) AS INDICATOR SPECIES FOR MONITORING BIODIVERSITY EFFECTS FROM VARIABLE RETENTION HARVESTING PRACTICES BC FOREST SCIENCE PROGRAM PROJECT NUMBER: Y061029 2005/06 FINAL REPORT January 2006 BY Isobel A. Pearsall Pearsall Ecological Consulting, 99 Machleary Street, Nanaimo, B.C. V9R 2G3 Email: [email protected] Contract report to: W.J. Beese, Cascadia Forest Products 4th Floor, 65 Front Street, Nanaimo, BC V9R 5H9 TABLE OF CONTENTS Table of Contents .............................................................................................................. 2 Executive Summary.......................................................................................................... 3 Introduction....................................................................................................................... 5 Objectives........................................................................................................................... 7 Materials and Methods..................................................................................................... 7 Study sites ....................................................................................................................... 7 Method of trapping ....................................................................................................... 10 Sampling design............................................................................................................ 10 Data collection .............................................................................................................. 13 Data Analysis...................................................................................................................13 Trap catches .................................................................................................................. 13 Description of carabid species .................................................................................. 13 Patterns of abundance ............................................................................................... 13 Statistical analysis..................................................................................................... 14 By-Catch data................................................................................................................ 16 Results .............................................................................................................................. 17 Ground vegetation and stand differences among sites.................................................. 17 Trap catches .................................................................................................................. 17 Description of carabid species .................................................................................. 17 Patterns of abundance ............................................................................................... 30 Statistical analysis..................................................................................................... 41 Discussion......................................................................................................................... 77 Conclusions...................................................................................................................... 86 Acknowledgements ......................................................................................................... 87 References........................................................................................................................ 88 Appendix One: Site Characteristics 2005..................................................................... 92 Appendix Two: Photographs of Sites............................................................................ 94 Appendix Three: New species discovered during 2005 ............................................. 108 Appendix Four: Analysis of by-catch.......................................................................... 109 2 EXECUTIVE SUMMARY • During 2005, I began a detailed examination of the effect of patch size on carabid communities in both experimental and operational forest blocks in West Island Timberlands 2nd growth and old growth. In particular, I was interested in comparing how well patches of different size retain original forest communities of beetles, as well as to examine edge effects, the potential “lifeboating” of patches, and how the size of patches affects composition of beetle communities within the cut matrices. I was also interested in determining whether the results were consistent among old growth and 2nd growth sites. • A total of three group retention sites (G1, G2, G3) were chosen in 2nd growth forest, and two group retention sites (G4 & G5) were chosen in old growth forest in West Island Timberlands. Site G1 contained large patches whereas those in site G2 were small. Both small and large patches were found in site G3. Site G4 had small patches and site G5 had two large patches. Traps were also set in 2nd growth forest located adjacent to site G2 as our 2nd growth control site (S1). We also set traps in the Klanawa group size VRAM site, which consisted of 5 treatments: old growth control (O), small patches (Sm), medium size patches (M), large patches (L) and clearcut ( C). All four 2nd growth sites were in the CWHxm and all old growth sites were in the CWHvm1. All sites had been harvested in 2003/2004 except for the VRAM site which was harvested in 2005. All 3 VRAM treatments (small patches, medium patches and large patches) had the same retention level of 24.3%. All the other sites had similar retention levels around 18-25% with the exception of site G5, where retention levels were 39.9%. • 3 years post-harvest, the patches were able to retain forest specialists in all of the group retention sites. Carabid beetles showed a response to patch size in group retention sites, with higher catches per trap of forest specialists in larger patches than in smaller patches. This response was seen in both old growth and 2nd growth sites. I have been able to produce species-patch area curves for the most abundant species, showing a clear response in terms of increased abundance to increasing patch size by forest specialists. However, retention of forest specialists was generally better in old growth patches than 2nd growth patches, and small patches of 2nd growth sites were particularly poor at retaining species such as S. angusticollis, Z. matthewsii, and P. crenicollis. • Carabid beetles showed edge responses, and several species built up at or close to the edge of patches. This may be associated with a general unwillingness by forest specialists to venture further out into the matrix. However, some of the generalist species also built up at the edges, which suggests that this may be related to the change in vegetation or microclimate at this location. 3 • The 2nd growth sites had generally greater species richness and diversity than the old growth sites, and control sites in both forest types generally had lower species richness and diversity than the group retention sites, probably because of influx of new species associated with new habitats and forest edges that were provided by group retention harvesting. Diversity was generally greater in small patch sites than sites with larger patches, except in the VRAM site, where diversity indices were very similar among the group retention treatments. Higher diversity in the small patch sites may be associated with the greater amount of edge, and greater size of matrix tracts, which may influence forest specialists in a negative fashion, and allow for greater abundance of forest generalists. • Seasonal patterns of abundance showed general peaks of abundance in May and September in most sites, for both total carabids pooled and for Scaphinotus angusticollis, the most commonly captured beetle. These months coincide with reproductive periods, and generally, both activity and abundance are greatest at this time. • Our results show a strong response by carabid beetles to forest edges and patch sizes. Whether this is a result of the microclimate or prey base of small patches being less ideal than larger patches, or an isolation effect, remains to be determined. Another factor that may be important to consider is the effect of patch shape, as my study only examined the factors of patch size and age. Further work in Port McNeil and in West Vancouver Island over 2006 will allow for a further opportunity to examine these responses in different variants. 4 INTRODUCTION The adaptive management program of Cascadia Forest Products (formerly Weyerhaeuser) was designed to examine the effectiveness of variable retention systems and stewardship zoning in maintaining forest attributes that may be necessary for sustaining biodiversity and ecological functions. To aid in this process, it has been necessary to determine whether there may be indicator organisms that may be useful to assess ecosystem health. Such indicator organisms would ideally be individual species, groups of species or structures that perform critical ecosystem functions or are particularly sensitive to disturbance. Specific details of the utility of carabids in this regard were outlined in the initial project proposal (Pearsall 2000). During the first year of this pilot study, 2001, work was carried out in Northern Vancouver Island to gather baseline information about carabid species abundance and