Patch size of forest openings and arthropod populations

Abstract

Five sizes of canopy openings (0.016 ha to 10 ha) were established in the Southern Appalachian Mountains in early 1982 to examine the initial patterns of plant and arthropod establishment across a size range of forest disturbances. Vegetation standing crop after the first growing season was considerably higher in large than small openings in apparent response to greater resource release (e.g., sunlight) in larger openings. Woody stump and root sprouts were the dominant mode of revegetation in each patch size. Forest dominants such as Quercus rubra, Q. prinus and Carya spp. were less important as sprouters in openings than several minor forest components (e.g., Robinia pseudo-acacia, Acer rubrum, Halesia carolina and Cornus florida). Arthropod abundance and community composition varied across the size range of forest openings. Arthropods from the surrounding forest readily utilized the smallest canopy openings (0.016 ha). All feeding guilds were well represented in these small openings and herbivore biomass and load (mg of herbivores/g of foliage) were much higher than in larger patches. In contrast, arthropod abundance and species richness were significantly lower in mid-size than smaller patches. The relatively sparse cover and high sunlight in mid-size openings may have promoted surface heat buildups or soil surface/litter moisture deficits which restricted arthropod entry from the surrounding forest. Arthropod abundance and species richness were higher in large than mid-size patches. The greater vegetation cover in larger openings may have minimized the deleterious effects on arthropod populations. However, the absence of population increases among these arthropod species maintained herbivore loads at very low levels in large patches. Our results suggest that arthropod abundance and diversity in sprout-dominated forest openings are highly dependent on the extent of environmental differences between patch and surrounding forest.

Habitat and Annual Variation in Arthropod Abundance Affects Blue TitCyanistes caeruleusReproduction

“…This suggests that the productivity of arthropod populations is much higher in the habitat with the less disturbed structure. This is a case of a more general rule concerning forest ecosystems that undisturbed, less fragmented woodlands are inhabited by richer and relatively stable insect communities (Shure & Phillips 1991, Didham et al 1996, Jokimäki et al 1998, Nour et al 1998, Wesołowski & Rowiński 2006.…”

Herbivorous Insect Response to Group Selection Cutting in a Southeastern Bottomland Hardwood Forest

“…The percent area covered by vegetation in young gaps was about the same regardless of gap size (T. Champlin, personal communication), so the amount of vegetation, at least in young gaps, increased with increasing Shure and Phillips (1991) used vacuum sampling to effectively measure differences in insect abundance between gaps of different size (0.016 Ð10 ha), but they also found relatively little difference in herbivore (Homoptera and Hemiptera) abundance within the range of gap sizes considered in this study. Our trapping procedure may also explain the difference between adult and larval Lepidoptera response to gap creation.…”

“…Predicting the response of herbivorous insects to such complicated and dynamic environments is difÞcult and quickly confounded by factors such as gap size and age. Large gaps, for example, receive more sunlight than small gaps (Shure and Wilson 1993), creating differences in soil moisture and plant growth (Shure and Phillips 1991). The plant communities present in gaps of differing age and stage of succession should be quite different, with unknown implications to the insect community.…”

Young Stand Thinning and Diversity Study: Response of Songbird Community One Decade Post-Treatment

“…Hermit Warbler and Golden-crowned Kinglet forage for insects primarily in conifer canopies (Ingold and Gallati, 1997;Pearson, 1997), so may be influenced by a flush of crown growth in response to thinning (Davis and others, 2007). Crown development around the edges of gaps in the LG stands may have been particularly productive (Tappeiner and others, 2002), and availability of insect prey may have consequently increased in these habitats (Shure and Phillips, 1991). The combination of crown development and relatively continuous canopy cover in the LT treatment likely provides the most suitable habitat of the three thinning treatments for Golden-crowned Kinglets.…”