Is What You See What You Get? Linking Forest Health to Wood Quality

They say you can’t judge a book by its cover. But can a piece of wood be judged by the tree it was cut from? Researchers from the Forest Products Laboratory (FPL) and the University of Georgia are working to find out.

Loblolly pine is widely planted in the southeastern United States. The plantations are highly productive, generating lumber for construction, and they are managed specifically to address increased population growth. This makes loblolly pine one of the most important tree species in the world in terms of wood use.

These weakened and dead loblolly pine trees show symptoms of southern pine decline.

These weakened and dead loblolly pine trees show symptoms of southern pine decline.

Recently, a phenomenon dubbed ‘southern pine decline’ (SPD) has contributed to high levels of tree mortality and decreased forest productivity. SPD is not entirely understood, but appears to be the result of a combination of physical and biological factors.

The forest industry has suggested that stands with symptoms of SPD have different weight scaling factors than stands not affected, and thus it appears that green moisture content is altered by SPD. Based on this observation, researchers are looking to determine whether trees affected by SPD have different wood density that would negatively affect the overall quality of the wood.

The project will involve studying trees from 14 stands in Alabama and Georgia, seven with SPD symptoms, and seven without. Trees will be selected from each stand, inspected for insect, disease, and fungal activity, and rated on their overall health. Cores (samples of wood) will also be taken from each tree and examined using various methods to determine moisture content and density. The data will then be analyzed to establish a link between wood quality and forest health.

For more details on this study, check out this Research in Progress report. The project is scheduled for completion in 2018.

Spectroscopy Research Challenges a Deadly Tree Fungus

Loblolly pine ranges from Georgia and the Carolinas to Texas but a destructive fungus is threatening this common southern softwood. Fusiform rust, Cronartium quercuum f.sp. fusiforme, is one the most destructive forest diseases in the South. With its complex life cycle, this fungus infects both loblolly and slash pine causing canker formation that frequently kills the infected branch.

The pine infection cycle occurs in Georgia in April and early May. Elongated swelling of the branches is the result of individual attacks on different parts of a tree. Many of the infected trees are unsuitable for later use as forest products, causing millions of dollars to be lost annually. Trees with large galls on the main stem are also unsuitable for many products.

Most of the photos in the above slideshow are by Robert L. Anderson, US Forest Service.

Changes in wood chemistry resulting from fungal decay of Scots pine have been studied directly using spectroscopy, the study of interactions between matter and radiated energy. A 2003 study by Pandey and Pitman exposed Scots pine sapwood to brown rot, selective white rot, and nonselective white rot fungi. In this study, the decay process was followed using Fourier Transform Infrared Spectroscopy (FTIR). After 12 weeks, the wood exposed to the brown rot fungus resulted in progressive increase in lignin content relative to cellulose and hemicellulose, whereas the lignin content of the wood exposed to the selective white rot decreased as decay proceeded. For the wood exposed to the nonselective white rot wood, both occurred.

A recently published FPL study applied both FTIR spectroscopy and Nuclear Magnetic Resonance Spectroscopy (NMR) to determine whether the pathogen caused any structural modifications to the chemical composition of lignin. A new FPL paper, Effect of Fusiform Rust (Cronartium quurcum f.sp. fusiforme) on the Composition of Loblolly Pine Lignin by Roderquita K. Moore, Allisha N. Blood, and Cherrelle I. Esekie discusses the results.