Effect of thinning on flying insect communities using window traps in young douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) forests in the Pacific Northwestern America

Abstract

The response of insects to four thinning intensities (control, light-thin, heavy-thin, or light-thin with gaps) was examined in 40-to 60-year-old Douglas-fir stands on the Willamette National Forest in Oregon, USA. In both 2000 and 2001, flying insect assemblages were collected from window traps placed over the forest floor in the center of each treatment block during two annual intervals: 1 ) June through August (early-season) and 2) August through October (late-season). The seasonal responses by these insects showed statistically significant differences in species richness (F=22.21, P <0.001 ) and mean abundance (F=34.87, P <0.001 ). The greatest numbers of taxa generated via indicator species analysis were in the early season and within the treatment of light-thin with gap (L/ G). In particular, the woodborer beetle, Buprestis (Burprestidae), was strongly associated with UG (Indicator Value = 52.4, P _<0.001 ). Two beetle taxa, Ampedus (Elateridae, IV=84.7, P _<0.001 ) and members of Cermabycidae (IV=58.4, P _<0.001 ), were correlated significantly with early-season, whereas Melanoplus (Acrididae) was associated with late-season (IV=21.3, P >0.05) and I_/G (IV=29.2, P _<0.05). For all thinning treatments, the numbers of species and individuals were higher in the early season than the late season. Non-metric multidimensional scaling showed that Axis 1 (65%) and Axis 2 (27%) explained 92% of the variance. The former was strongly associated with thinning intensity, having higher coefficients of species richness (r=0.645) and species diversity (r=0.583). The multi-response permutation procedures showed a statistically significant difference for thinning intensity (T-statistics= -4.6322, A-statistics=0.0479, P <0.0001 ). These results suggest that heavier thinning can result in more diverse populations of flying insects, including herbivores and predators.

Biodiversity response to intensive biomass production from forest thinning in North American forests – A meta-analysis

“…We found 46 invertebrate responses (effect sizes) from 2 studies; 1 in the northwestern U.S. (Yi, 2007), and another in the upper Midwestern U.S. (Table 1) (Tibbels and Kurta, 2003). Thinned stands reported significantly higher biomass of invertebrates than unthinned stands for 35 of 42 order biomass effect sizes.…”

“…The diversity of arthropod functional groups can be a good measure of overall habitat complexity (Hunter, 2002;Yi, 2007). However, effects of forest thinning on invertebrates are not well understood (Duguay et al, 2000;Schowalter et al, 2003;Yi, 2007).…”

“…Depending on their life history characteristics, invertebrate communities have been shown to respond positively (Yi, 2007), negatively (Niemela et al, 1993), or minimally (Schowalter et al, 2003;Apigian et al, 2006) to forest thinning and other canopyopening disturbances. The research we summarized, including responses for several different types of arthropods (i.e.…”

Dampak Jangka Pendek Penjarangan Hutan Campuran terhadap Keanekaragaman Serangga Terbang di KPH Banten (Short-Term Impact of Thinning of Mixed Forest on the Diversity of Flying Insects in Forest Management Unit of Banten)

“…Penelitian ini memperoleh hasil yang mirip dengan penelitian sebelumnya. Yi (2007) melaporkan bahwa kelimpahan pemangsa lebih tinggi di hutan yang dijarangi daripada hutan yang tidak dijarangi, dan kelimpahan herbivora menurun sesudah penjarangan hutan. Penurunan kerapatan pohon memiliki pengaruh yang kuat terhadap populasi herbivora.…”

Relationship between global warming and species richness of vascular plants

“…Species richness may be evaluated on several different levels, including molecular, species, habitat, or ecosystem (Gentry, 1992;Pimm and Gittleman, 1992;Pimm et al, 1995;Bao et al, 2006;Tripathi et al, 2007;Yi, 2007). It is widely accepted that species is the single most useful unit for assessing such richness, whether carried out locally, nationally, regionally, or globally.…”