David R. Coyle

Bridging the gap between micro - and macro-scale perspectives on the role of microbial communities in global change ecology

In order to understand the role microbial communities play in mediating ecosystem response to disturbances it is essential to address the methodological and conceptual gap that exists between micro- and macro-scale perspectives in ecology. While there is little doubt microorganisms play a central role in ecosystem functioning and therefore in ecosystem response to global change-induced disturbance, our ability to investigate the exact nature of that role is limited by disciplinary and methodological differences among microbial and ecosystem ecologists. In this paper we present results from an interdisciplinary graduate-level seminar class focused on this topic. Through the medium of case studies in global change ecology (soil respiration, nitrogen cycling, plant species invasion and land use/cover change) we highlight differences in our respective approach to ecology and give examples where disciplinary perspective influences our interpretation of the system under study. Finally, we suggest a model for integrating perspectives that may lead to greater interdisciplinary collaboration and enhanced conceptual and mechanistic modeling of ecosystem response to disturbance.

Production of short-rotation woody crops grown with a range of nutrient and water availability: establishment report and first-year responses.

Coleman, M.D., et. al. 2003. Production of Short-Rotation Woody Crops Grown with a Range of Nutrient and Water Availability: Establishment Report and First-Year Responses. Report. USDA Forest Service, Savannah River, Aiken, SC. 26 pp. Abstract: Many researchers have studied the productivity potential of intensively managed forest plantations. However, we need to learn more about the effects of fundamental growth processes on forest productivity; especially the influence of aboveground and belowground resource acquisition and allocation. This report presents installation, establishment, and first-year results of four tree species (two cottonwood clones, sycamore, sweetgum, and loblolly pine) grown with fertilizer and irrigation treatments. At this early stage of development, irrigation and fertilization were additive only in cottonwood clone ST66 and sweetgum. Leaf area development was directly related to stem growth, but root production was not always consistent with shoot responses, suggesting that allocation of resources varies among treatments. We will evaluate the consequences of these early responses on resource availability in subsequent growing seasons. This information will be used to: (1) optimize fiber and bioenergy production; (2) understand carbon sequestration; and (3) develop innovative applications such as phytoremediation; municipal, industrial, and agricultural wastes management; and protection of soil, air, and water resources.

Prior host feeding experience influences ovipositional but not feeding preference in a polyphagous insect herbivore

Black vine weevils, Otiorhynchus sulcatus (Fabricius) (Coleoptera: Curculionidae), are globally‐distributed polyphagous pests of many horticultural crops. We investigated how adult weevils were affected by host switching and, in particular, how host plant species nutritional and defensive chemistry affected subsequent host plant species selection and oviposition. Adults were fed one of three host plant species, blackcurrant [Ribes nigrum L. (Grossulariaceae)], raspberry [Rubus idaeus L. (Rosaceae)], or strawberry [Fragaria x ananassa Duchesne (Rosaceae)], throughout their pre‐reproductive periods and then subjected to behavioral choice assays with these plants. Foliar chemistry differed significantly among the three host plant species. Compared to raspberry and strawberry foliage, blackcurrant foliage was 13% lower in nitrogen, 3% higher in carbon, and 28% higher in phenolic compounds. Initial host plant species had a significant effect on weevil mortality, with more weevils dying when previously fed blackcurrant (12%) than strawberry (3%) or raspberry (0%) regardless of subsequent host. Initial host plant species also affected oviposition, with weevils laying only ca. two eggs per week when previously fed blackcurrant, compared to those on raspberry or strawberry (ca. 11 and 15 eggs per week, respectively). When given a choice, weevils discriminated among host plant species and tended to oviposit on plants on which they had previously fed, even when the plant was nutritionally inferior for egg production and adult survival. In contrast, feeding behavior was only affected by the current host plant species. Feeding and oviposition were related to leaf chemistry only in blackcurrant, as leaf consumption was negatively correlated with foliar carbon and zinc concentrations, and positively correlated with foliar phosphorus and potassium concentrations.

Cottonwood leaf beetle (Coleoptera: Chrysomelidae) defoliation impact on Populus growth and above-ground volume in a short-rotation woody crop plantation

Abstract 1 The impact of cottonwood leaf beetle Chrysomela scripta F. defoliation on four plantation‐grown Populus clones was examined over three growing seasons. We used a split‐plot design with two treatments: protected (by insecticides) and an unprotected control. Tree height and diameter at 1 m were measured annually and above‐ground volume was calculated. 2 Protected trees of most clones had grown over 2 m taller after three growing seasons. Diameter differences ranged from over 1–4 cm larger on protected trees. Insecticide protection increased above‐ground volume over 20 dm3 in one clone, and at least 4 dm3 in all others. Chrysomela scripta defoliation resulted in a 50–73% loss of above‐ground volume. Defoliation also resulted in increased lateral branching and forked terminals on unprotected trees. 3 Defoliation impact varied among clone. The pure Populus deltoides clone 91 × 04‐03 showed the greatest growth response to chemical protection, whereas clone NM2 (P. nigra × P. maximowiczii) responded the least. 4 Pest control is a key issue in short‐rotation plantation management. Until adequate pest‐resistant clones can be developed and natural enemy complexes better understood, chemical (biorational and organic) and cultural control may be used to reduce impacts of herbivorous pests.

Large-scale experimental landscapes reveal distinctive effects of patch shape and connectivity on arthropod communities

The size, shape, and isolation of habitat patches can affect organism behavior and population dynamics, but little is known about the relative role of shape and connectivity in affecting ecological communities at large spatial scales. Using six sampling sessions from July 2001 until August 2002, we collected 33,685 arthropods throughout seven 12-ha experimental landscapes consisting of clear-cut patches surrounded by a matrix of mature pine forest. Patches were explicitly designed to manipulate connectivity (via habitat corridors) independently of area and edge effects. We found that patch shape, rather than connectivity, affected ground-dwelling arthropod richness and beta diversity (i.e. turnover of genera among patches). Arthropod communities contained fewer genera and exhibited less turnover in high-edge connected and high-edge unconnected patches relative to low-edge unconnected patches of similar area. Connectivity, rather than patch shape, affected the evenness of ground-dwelling arthropod communities; regardless of patch shape, high-edge connected patches had lower evenness than low- or high-edge unconnected patches. Among the most abundant arthropod orders, increased richness in low-edge unconnected patches was largely due to increased richness of Coleoptera, whereas Hymenoptera played an important role in the lower evenness in connected patches and patterns of turnover. These findings suggest that anthropogenic habitat alteration can have distinct effects on ground-dwelling arthropod communities that arise due to changes in shape and connectivity. Moreover, this work suggests that corridors, which are common conservation tools that change both patch shape and connectivity, can have multiple effects on arthropod communities via different mechanisms, and each effect may alter components of community structure.

Laboratory and field evaluations of two Bacillus thuringiensis formulations, Novodor and Raven, for control of cottonwood leaf beetle (Coleoptera: Chrysomelidae).

Abstract Laboratory and field experiments were conducted to determine the efficacy of two Bacillus thuringiensis Berliner formulations, Novodor and Raven, for controlling cottonwood leaf beetle, Chrysomela scripta F. (Coleoptera: Chrysomelidae). In laboratory bioassays, larvae or adults were added to petri dishes containing Populus × euramericana Guinier ‘Eugenei’ foliage that had been treated with distilled water (control) or one of the commercial Bt formulations at either high or low label rates. Survival was recorded on a 24-h basis, and leaf area consumed was measured at the conclusion of all trials. Significant differences from the control in mortality and leaf area consumption resulted in the Novodor and Raven treatments for all life stages tested; however, adults were better able to withstand the effects of B. thuringiensis toxins than were the immatures. Early- and late instar C. scripta populations were monitored in the field (1998 and 1999) after treatment with either water or various concentrations of one of the commercial Bt formulations. Significant mortality resulted with all concentrations and for all life stages tested compared with the control (tap water). The commercial formulations also were tested under plantation conditions as part of a long-term defoliation study. Both Novodor and Raven reduced cottonwood leaf beetle defoliation damage after a single application, giving high efficacy for control of cottonwood leaf beetle under the conditions and concentrations evaluated.

Effects of clone, silvicultural, and miticide treatments on cottonwood leafcurl mite (Acari: Eriophyidae) damage in plantation Populus

Abstract Aculops lobuliferus (Keifer) is a little known pest of plantation Populus spp., which is capable of causing substantial damage. This is the first documented occurrence of A. lobuliferus in South Carolina. Previous anecdotal data indicated clonal variation in Populus susceptibility to A. lobuliferus damage. A damage rating scale was created to monitor mite damage in 2000–2001 in a short-rotation woody crop plantation; damage descriptions and seasonal phenology also were recorded. Foliar damage and terminal mortality were monitored on two Populus deltoides Bartr. clones, ST66 and S7C15, receiving one of three silvicultural treatments (irrigated [I], fertilized [F], or I+F) or no treatment (control). In 2001, early season foliar damage ratings were significantly higher on clone S7C15; however, damage on clone ST66 was greater after miticide treatments later in the year. Terminal mortality did not differ between clones. Silvicultural treatment significantly affected foliar damage levels in both clones. Trees receiving I+F and F treatments had higher damage ratings than did trees receiving irrigation alone or the control at times. Clone S7C15 trees receiving fertilizer had significantly less terminal mortality than their nonfertilized counterparts. Application of a commercially available miticide significantly reduced A. lobuliferus damage levels. This study demonstrates that A. lobuliferus damage levels can be influenced by Populus clone and silvicultural treatment. Foliar and terminal damage levels observed in this study indicate the potential for substantial economic impact of A. lobuliferus on plantation Populus. Although an effective control method may be to select and plant resistant Populus clones, chemical control remains a viable option.

Performance of the invasive weevil Polydrusus sericeus is influenced by atmospheric CO 2 and host species

1 Natural forest systems constitute a major portion of the worlds land area, and are subject to the potentially negative effects of both global climate change and invasion by exotic insects. A suite of invasive weevils has become established in the northern hardwood forests of North America. How these insects will respond to increasing CO2 or O3 is unknown. 2 The present study examined the effects of elevated atmospheric CO2 and O3 on the invasive weevil Polydrusus sericeus Schaller at the Aspen Free Air CO2 Enrichment (FACE) site near Rhinelander, Wisconsin. A performance assay was conducted in the laboratory during the summer of 2007 using mated pairs of P. sericeus fed a combination of aspen, birch and maple foliage. We recorded leaf area consumption, oviposition and adult longevity. We also conducted visual abundance surveys in the field from 2004 to 2007 on aspen and birch at Aspen FACE. 3 Elevated CO2, but not O3, significantly affected P. sericeus performance. Female, but not male, longevity was reduced under elevated CO2. Polydrusus sericeus also produced fewer eggs under elevated CO2 conditions compared with ambient conditions. Adult P. sericeus strongly preferred birch over both aspen and maple, regardless of fumigation treatment. 4 The effects of elevated CO2 on P. sericeus populations at Aspen FACE were minimal, and varied among years and host tree species. Polydrusus sericeus abundance was significantly greater on birch than aspen. Over the long term, elevated CO2 may reduce adult female longevity and fecundity of P. sericeus. Further studies are needed to evaluate how this information may scale to ecosystem impacts.

Cottonwood Leaf Beetle (Coleoptera: Chrysomelidae) Larval Performance on Eight Populus Clones

Abstract The cottonwood leaf beetle, Chrysomela scripta F., is the most serious defoliator of young plantation-grown Populus in the eastern United States, yet there is a paucity of data on larval feeding performance across Populus clones used in tree breeding. Field experiments were conducted in 1998 and 1999 to determine the overall feeding performance of larval C. scripta on 8 Populus selections from a pedigree family. Using a randomized complete block design, entire trees were enclosed in mesh cages, and female C. scripta were allowed to oviposit in sleeve cages on each tree. Larval cohorts were culled to 10 upon hatch and allowed to develop to pupation within each sleeve cage. Larval survival, pupal weight, adult emergence, and total mortality were recorded as performance parameters. Significant but inconsistent performance differences were found among clones, suggesting that some clones were less suitable for C. scripta larval development in some insect generations. Larval performance was generally poorer on clones with higher P. trichocarpa parentage. C. scripta performance was significantly poorer in 1999 and showed a decline throughout the 1999 growing season, but it is not clear whether this was caused by conditions of the host plants, weather patterns, or changes made in the source of insects for infestation. Clones with foliar characteristics detrimental to larval C. scripta performance could be used for plantings or in developing C. scripta-resistant hybrid Populus selections for short-rotation woody crop systems.

The Ecology, Behavior, and Biological Control Potential of Hymenopteran Parasitoids of Woodwasps (Hymenoptera: Siricidae) in North America

ABSTRACT Native and exotic siricid wasps (Hymenoptera: Siricidae) can be ecologically and/or economically important woodboring insects in forests worldwide. In particular, Sirex noctilio (F.), a Eurasian species that recently has been introduced to North America, has caused pine tree (Pinus spp.) mortality in its non-native range in the southern hemisphere. Native siricid wasps are known to have a rich complex of hymenopteran parasitoids that may provide some biological control pressure on S. noctilio as it continues to expand its range in North America. We reviewed ecological information about the hymenopteran parasitoids of siricids in North America north of Mexico, including their distribution, life cycle, seasonal phenology, and impacts on native siricid hosts with some potential efficacy as biological control agents for S. noctilio. Literature review indicated that in the hymenopteran families Stephanidae, Ibaliidae, and Ichneumonidae, there are five genera and 26 species and subspecies of native parasitoids documented from 16 native siricids reported from 110 tree host species. Among parasitoids that attack the siricid subfamily Siricinae, Ibalia leucospoides ensiger (Norton), Rhyssa persuasoria (L.), and Megarhyssa nortoni (Cresson) were associated with the greatest number of siricid and tree species. These three species, along with R. lineolata (Kirby), are the most widely distributed Siricinae parasitoid species in the eastern and western forests of North America. Depending upon certain abiotic and biotic factors, we hypothesize that these four parasitoid species may contribute to the biological control of S. noctilio. Major gaps exist regarding parasitoid ecology, including their taxonomy, distribution range, exact siricid and tree hosts, interactions with hosts, phenology, and chemoecology in forest stands. As S. noctilio continues to expand its distribution in North America, a better understanding of the biology of these parasitoids may be needed in coniferdominated landscapes.