Lori G. Eckhardt

Ecology of root-feeding beetles and their associated fungi on longleaf pine in Georgia.

ABSTRACT Root-feeding beetles, particularly of the curculionid subfamilies Scolytinae and Molytinae, are known to be effective vectors of Ophiostomatoid fungi. Infestation by these insects and subsequent infection by the Ophiostomatoid fungi may play an important role in accelerating symptom progression in pine declines. To examine the relationship between beetles and fungi in longleaf pine stands, root-feeding curculionids were collected in pitfall traps baited with ethanol and turpentine for 62 wk, and Ophiostomatoid fungi were isolated from their body surfaces. The most abundant root-feeding beetles captured were Hylastes tenuis, H. salebrosus, Pachyhbius picivorus, Hylobius pales, and Dendroctonus terebrans. The number of insects captured peaked in spring and fall, although peaks for different insect taxa did not coincide. The most frequently isolated fungi were Grosmannia huntii, Leptographium procerum, L. terebrantis, and L. serpens. Other Ophiostomatoid fungi recovered included Ophiostoma spp. and Pesotum spp. Insect infestation data suggest that Hylastes spp. share an ecological niche, as do Hb. pales and P. picivorus, because the ratios of their fungal symbionts were similar. The fungi associated with D. terebrans suggest that it did not share habitat with the other principle vectors.

Near infrared spectroscopy calibration for wood chemistry: which chemometric technique is best for prediction and interpretation?

This paper addresses the precision in factor loadings during partial least squares (PLS) and principal components regression (PCR) of wood chemistry content from near infrared reflectance (NIR) spectra. The precision of the loadings is considered important because these estimates are often utilized to interpret chemometric models or selection of meaningful wavenumbers. Standard laboratory chemistry methods were employed on a mixed genus/species hardwood sample set. PLS and PCR, before and after 1st derivative pretreatment, was utilized for model building and loadings investigation. As demonstrated by others, PLS was found to provide better predictive diagnostics. However, PCR exhibited a more precise estimate of loading peaks which makes PCR better for interpretation. Application of the 1st derivative appeared to assist in improving both PCR and PLS loading precision, but due to the small sample size, the two chemometric methods could not be compared statistically. This work is important because to date most research works have committed to PLS because it yields better predictive performance. But this research suggests there is a tradeoff between better prediction and model interpretation. Future work is needed to compare PLS and PCR for a suite of spectral pretreatment techniques.

Variation in virulence among four root-inhabiting Ophiostomatoid fungi on Pinus taeda L., P. palustris Mill, and P. elliottii Engelm. seedlings

Abstract Ophiostomatoid fungi have been implicated in root disease of pines in the southeastern United States. To understand more about their virulence, inoculation studies were conducted on loblolly (Pinus taeda), longleaf (Pinus palustris), and slash pine (Pinus elliotii). One-year-old bareroot seedlings, after being planted and established for 11 weeks, were wound-inoculated with one of four prominent North American ophiostomatoid fungal species. After three months, a darkened lesion, extending from the point of inoculation was observed for all species. Grosmannia huntii (L. huntii) caused the greatest lesion and occlusion length in loblolly pine and slash pine. Leptographium procerum and L. terebrantis caused similar lesion and occlusion lengths and were the least virulent among the fungi tested. These studies indicate clear virulence differences among the four North American fungi. Grosmannia huntii, previously not known to be pathogenic, was observed causing significant damage compared with other well-known Leptographium species. Finally, lesion and tissue occlusion lengths were significantly smaller in longleaf pine for all fungal species when compared to loblolly and slash pine.

Non-destructive prediction of the properties of forest biomass for chemical and bioenergy applications using near infrared spectroscopy

Forest biomass will play a key role as a feedstock for bioproducts as the bioeconomy develops. Rapid assessment of this heterogeneous resource will help determine its suitability as feedstock for specific applications, aid in feedstock improvement programmes and enable better process control that will optimise the biorefinery process. In this study, near infrared spectroscopy coupled with partial least-squares regression was used to predict important chemical and thermal reactivity properties of biomass made up of needles, twigs, branches, bark and wood of Pinus taeda (loblolly pine). Models developed with the raw spectra for property prediction used between three and eight factors to yield R2 values ranging from a low of 0.34 for higher heat values to a high of 0.92 for volatile matter. Pretreating the raw spectra with first derivatives improved the fit statistics for all properties (i.e. min 0.57, max 0.92; with two or three factors). The best-performing models were for extractives, lignin, glucose, cellulose, volatile matter and fixed carbon (R2 ≥ 0.80, residual predictive deviation/ratio of performance to deviation ≥1.5). This study provided the capacity to predict multiple chemical and thermal/energy traits from a single spectrum across an array of materials that differ considerably in chemistry type and distribution. Models developed should be able to rapidly predict the studied properties of similar biomass types. This will be useful in rapidly allocating feedstocks that optimise biomass conversion technologies.

Identifying Plant Part Composition of Forest Logging Residue Using Infrared Spectral Data and Linear Discriminant Analysis

As new markets, technologies and economies evolve in the low carbon bioeconomy, forest logging residue, a largely untapped renewable resource will play a vital role. The feedstock can however be variable depending on plant species and plant part component. This heterogeneity can influence the physical, chemical and thermochemical properties of the material, and thus the final yield and quality of products. Although it is challenging to control compositional variability of a batch of feedstock, it is feasible to monitor this heterogeneity and make the necessary changes in process parameters. Such a system will be a first step towards optimization, quality assurance and cost-effectiveness of processes in the emerging biofuel/chemical industry. The objective of this study was therefore to qualitatively classify forest logging residue made up of different plant parts using both near infrared spectroscopy (NIRS) and Fourier transform infrared spectroscopy (FTIRS) together with linear discriminant analysis (LDA). Forest logging residue harvested from several Pinus taeda (loblolly pine) plantations in Alabama, USA, were classified into three plant part components: clean wood, wood and bark and slash (i.e., limbs and foliage). Five-fold cross-validated linear discriminant functions had classification accuracies of over 96% for both NIRS and FTIRS based models. An extra factor/principal component (PC) was however needed to achieve this in FTIRS modeling. Analysis of factor loadings of both NIR and FTIR spectra showed that, the statistically different amount of cellulose in the three plant part components of logging residue contributed to their initial separation. This study demonstrated that NIR or FTIR spectroscopy coupled with PCA and LDA has the potential to be used as a high throughput tool in classifying the plant part makeup of a batch of forest logging residue feedstock. Thus, NIR/FTIR could be employed as a tool to rapidly probe/monitor the variability of forest biomass so that the appropriate online adjustments to parameters can be made in time to ensure process optimization and product quality.

The pathogenicity and virulence of four Ophiostomatoid fungi on young Longleaf pine trees

Abstract In southeastern USA, insect vectors transfer pathogenic ophiostomatoid fungi that cause disease in southern pines. During 2007 and 2008, potted longleaf pines (P. palustris Mill.), of similar ages ranging in height from 58 to 198 cm, were inoculated with the following fungi to assess their pathogenicity (and virulence): Grosmannia huntii, Leptographium procerum, L. serpens and L. terebrantis. Seventeen weeks after inoculation, L. terebrantis, L. serpens and G. huntii were found to cause significantly larger lesions and more sapwood discolouration than wounded uninoculated controls. Leptographium terebrantis caused significantly more sapwood discolouration than all other fungi. Despite significant sapwood occlusion after fungal inoculation, no reductions in needle water potentials were observed between treatments. All fungal species were successfully re-isolated from longleaf pine trees.

Correlation between infection by ophiostomatoid fungi and the presence of subterranean termites in loblolly pine (Pinus taeda L.) roots

Observations of subterranean termites feeding in pine sapwood containing ophiostomatoid fungi prompted the present study aiming to investigate the effect of infection by Leptographium fungi on the probability of encountering subterranean termites in loblolly pine (Pinus taeda L.) roots. Root samples were collected from 2350 loblolly pine trees in Alabama, Texas, Louisiana and Mississippi using hand tools. The presence or absence of subterranean termites in the roots was recorded. Samples were plated on malt extract agar and cycloheximide‐streptomycin malt agar and incubated to determine which, if any, fungal species were present. The presence of Leptographium procerum, Leptographium terebrantis or both was significantly associated with an increased presence of subterranean termites in loblolly pine roots. The results obtained in the present study indicate that complex ecological interactions may exist between ophiostomatoid fungi, as carried by root‐feeding bark beetles, and subterranean termites.

A new Ophiostoma species from loblolly pine roots in the southeastern United States.

During the course of a survey of fungi in loblolly pine (Pinus taeda) roots in Georgia, USA, a species of Ophiostoma morphologically similar to O. pluriannulatum, was isolated. Morphological characteristics and DNA sequence comparisons were used to identify the fungus. The isolates produced perithecia with unusually long necks similar to those of O. pluriannulatum but they had few or no annuli. DNA sequences for the ribosomal internal transcribed spacer regions 1 and 2 were identical to those of O. pluriannulatum. Sequence data of the β-tubulin gene region revealed the absence of intron 4 and presence of intron 5, distinguishing the isolates from O. pluriannulatum, which has intron 4 but not intron 5. Phylogenetic analyses of the β-tubulin sequences showed that the isolates from loblolly pine roots grouped together in a lineage distinct from O. multiannulatum and O. subannulatum, both of which lack intron 4 and have intron 5. The fungus is consequently described as O. sparsiannulatum sp. nov., a novel taxon in the O. pluriannulatum complex.

Multivariate modeling of acoustomechanical response of 14-year-old suppressed loblolly pine ( Pinus taeda) to variation in wood chemistry, microfibril angle and density

The polymeric angle and concentration within the S2 layer of the softwood fiber cell wall are very critical for molecular and microscopic properties that influence strength, stiffness and acoustic velocity of wood at the macroscopic level. The main objective of this study was to elucidate the effect of cellulose, hemicellulose, lignin, microfibril angle and density on acoustic velocity and material mechanical properties of 14-year-old suppressed loblolly pine. Cellulose, hemicellulose and density are consistently the most important drivers of strength, stiffness and velocity. Cellulose and lignin are the highest and lowest contributor to velocity, respectively, with lignin acting as a sound wave dispersant, while cellulose is the most important conductor of sound wave at the molecular level, while hemicellulose acts as a special coupling agent between these components. The polymeric constituents are thus important drivers of sound wave propagation at the molecular level, while density played a subsequent role at the macroscale.

The effect of thinning and clear-cut on changes in the relative abundance of root-feeding beetle (Coleoptera: Curculionidae) in Pinus taeda plantations in central Alabama and Georgia.

BACKGROUND Root-feeding beetles, particularly Hylastes spp., Hylobius pales Herbst and Pachylobius picivorus Germar, increase in abundance in stressed forest stands and vector Grosmannia and Leptographium spp. fungi, which contribute to southern pine decline (SPD) in the southeastern United States. This study examined changes in the relative abundance of root-feeding beetles in response to mechanical thinning and clear-cut of even-age loblolly pine (Pinus taeda L.) stands in central Alabama and Georgia every 2 weeks during a 30 month study in 2009-2012. RESULTS The most abundant bark beetles were Hylastes salebrosus Eichhoff, H. porculus Erichson and H. tenuis Eichhoff. The relative abundance of the Hylastes spp. significantly increased after thinning treatments at all five sites. An initial decrease in Hylastes spp. occurred in response to clear-cut in some plots, but they typically recovered 2 months later and were stable for the remainder of the study. CONCLUSION This study reports on the relative abundance responses of pathogen-vectoring root-feeding beetles to a thinning and clear-cut treatment in P. taeda stands. Thinning treatments conducted during the summer and winter may increase the relative abundance of Hylastes spp., vectors of Leptographium and Grosmannia spp., which are known to contribute to SPD by triggering plants to release defensive volatile compounds.