Activated Carbons Derived from High-Temperature Pyrolysis of Lignocellulosic Biomass

Biomass pyrolysis to produce biofuel and hydrogen yields large amounts of charred byproducts with low commercial value. A study was conducted to evaluate their potential for being converted into higher value activated carbons by a low-cost process. Six chars derived from various lignocellulosic precursors were activated in CO2 at 800 °C to 30–35% weight loss, and their surface area and porosity were characterized by nitrogen adsorption at 77 K. It was found that, in similar activation conditions, the surface area of the activated carbons correlates with the activation energy of the oxidation reaction by CO2, which in turn varies inversely with the carbon yield after thermolysis in nitrogen at 1000 °C. Since lignin is the most thermally-stable component of lignocellulosic biomass, these results demonstrate, indirectly, that robust, lignin-rich vegetal precursors are to be preferred to produce higher quality activated carbons. The chars derived from white pine (pinus strobus) and chestnut oak (quercus prinus) were converted to activated carbons with the highest surface area (900–1100 m2/g) and largest mesopores volume (0.85–1.06 cm3/g). These activated carbons have properties similar to those of commercially-available activated carbons used successfully for removal of pollutants from aqueous solutions.

Infectivity and Inoculum Production of Phytophthora ramorum on Roots of Eastern United States Oak Species

Little is known about colonization of roots of trees by Phytophthora ramorum. We examined zoospore concentration and exposure time needed to infect six Quercus (oak) species and the inoculum produced from their roots. Sprouted acorns, exposed to zoospores (3,000/ml) for different times and transplanted to potting soil, were susceptible to infection within 1 h of exposure but root weights were not impacted after 4 weeks (P = 0.952). Roots of Quercus prinus seedlings, inoculated with sporangia, had 0.6 to 3.2% colonization of the total root mass after 5 months. Neither root lesions nor obvious root sloughing were observed. Inoculum threshold levels were tested by exposing radicles to varying zoospore concentrations for 24 h. Results showed that radicle infection occurred even at 1 zoospore/ml. To test inoculum production, roots were inoculated with sporangia and transplanted into pots. Periodically, samples of runoff were collected and plated on selective medium. Afterward, root segments were plated to calculate percent colonization. After 16 and 35 days, root colonization and inoculum production from oak was lower than that of Viburnum tinus, a positive control. This study shows that P. ramorum is able to infect sprouted oak acorns and produce secondary inoculum, which may be important epidemiologically.

Reconstructing the competitive dynamics of mixed-oak neighborhoods

The disparity between the potential for latent oak dominance within a stand and their region-wide decline in importance value raises questions about the competitiveness of oaks in early stand dynamics. We reconstructed tree height growth dynamics in mixed-species neighborhoods to determine if currently dominant oaks were ever shorter than their competitors and at what age currently subordinate oaks fell behind. In 23–36 year old mixed-oak stands in two physiographic provinces of Pennsylvania, we identified dominant and subordinate northern red oaks ( Quercus rubra L.) and chestnut oaks ( Quercus prinus L.) competing with adjacent non-oaks (red maple ( Acer rubrum L.), sweet birch ( Betula lenta L.), and black cherry ( Prunus serotina Ehrh.)) of equal crown class. In each stand, we randomly selected 20 tree neighborhoods and collected stem cross sections every metre from the base to the tip of each tree. In the Allegheny Plateau province, dominant northern red oaks never averaged more than 2 m shorter than their competitors, while by age 20, subordinate oaks were commonly more than 2 m behind. Dominant chestnut oaks in the Ridge and Valley province were never more than 1 m shorter than their competitors; subordinate oaks, however, were generally always at least a metre behind. In both regions, growth dynamics of currently subordinate trees were indistinguishable from those of currently dominant trees during their first decade. Because oaks that were considerably behind at age 15 were likely to be subordinate by age 30, the window of opportunity for release to prevent oaks from becoming permanently overtopped and unable to recover may thus be relatively early (age 10–20).

Prediction and measurement of thermally induced cambial tissue necrosis in tree stems

A model for fire-induced heating in tree stems is linked to a recently reported model for tissue necrosis. The combined model produces cambial tissue necrosis predictions in a tree stem as a function of heating rate, heating time, tree species, and stem diameter. Model accuracy is evaluated by comparison with experimental measurements in two hardwood and two softwood species: red maple (Acer rubrum), chestnut oak (Quercus prinus), ponderosa pine (Pinus ponderosa), and Douglas-fir (Pseudotsuga menziesii). Results are promising, and indicate that the model predicts stem mortality/survival correctly in ~75–80% of the test cases. A limited sensitivity analysis of model kill depth predictions suggests that the model is more sensitive to required input data for some species than for others, and that the certainty in predicting vascular cambium necrosis decreases as stem diameter decreases.

Linking surface-fire behavior, stem heating, and tissue necrosis

Data from 69 experimental, small-plot fires are used to describe relationships among fire intensity, bark-surface heat flux, and depth of necrosis in stem tissue for red maple (Acer rubrum L.) and chestnut oak (Quercus prinus L.). A tetrazolium staining technique was used to determine the depth of necrosis in tree boles subjected to fires with intensities of 20 to 2000 kW/m. Over a range of bark moistures (28%–83%) and bole diameters (3–20 cm), depth of necrosis appears to be primarily a function of fire intensity, flame residence time at the stem, and the corresponding time-integrated heat flux at the bark surface. Our results, along with known relations between bole diameter and bark thickness, and improved models of fire behavior and heat transfer, may be useful for estimating tree mortality resulting from prescribed fires.