Blue intensity as a temperature proxy in the eastern United States: A pilot study from a southern disjunct population of Picea rubens (Sarg.)

Annual surface air temperatures across the eastern United States (US) have increased by more than 1 °C within the last century, with the recent decades marked by an unprecedented warming trend. Tree-rings have long been used as a proxy for climate reconstruction, but few truly temperature-sensitive trees have been documented for the eastern US, much less the Appalachian Mountains in the Southeast. Here, we measure blue intensity (BI) and ring width (RWI) in red spruce growing at the southernmost latitudinal range margin of the species on the North Carolina-Tennessee border to test the efficacy of using either metric as a temperature proxy in the eastern US. The BI and RWI chronologies spanned 1883–2008 and had an interseries correlations of 0.42 and 0.54, respectively, but time series were trimmed to the period 1950–2008 due to low sample depth. We discovered strong, positive, and stable correlations between both current-year early fall (September–October) T_max (r = 0.62; p < 0.001) and T_mean (r = 0.51; p < 0.001) and ΔBI during the period 1950–2008, but found no significant relationships between temperature and RWI. We show BI metrics measured in red spruce to be a promising temperature proxy for the southern Appalachian Mountain region. Future research should focus on testing [1] the efficacy of using BI on red spruce collected from across the species range, and [2] the potential for using BI as a temperature proxy in other conifers distributed in the eastern US.     

Growth pattern of Picea rubens prior to canopy recruitment

A majority (72%) of Picea rubens Sarg. (red spruce) trees in an old-growth spruce-fir forest in the Great Smoky Mountains underwent episodes of radial growth suppression and release before they reached the forest canopy. Prior to canopy recruitment, trees experienced an average of 1.43 and a maximum of 7 suppression periods with an average ring width of 0.257 mm. Duration of suppression periods ranged from 4 to 79 years with an average of 19.05 years, which was significantly shorter than the average duration of release periods (29.00 years). Mean ring width in a suppression period was negatively correlated with duration of the suppression period. The opposite was true for release periods. The severity of suppression had no significant effect on mean ring width in subsequent release periods. Greater suppression was observed in the recent growth pattern of current non-canopy trees than in the historical growth pattern reconstructed from current canopy trees. Growth releases prior to canopy recruitment, triggered by small gaps or neighboring gaps, displayed a continuous pattern over the last two centuries and had consistent frequency in recent decades. By contrast, canopy recruitment resulting from large-gap disturbances was discontinuous over the last two centuries, and less frequent after 1850.     

Universal fractionation of lignin–carbohydrate complexes (LCCs) from lignocellulosic biomass: an example using spruce wood

It is of both theoretical and practical importance to develop a universally applicable approach for the fractionation and sensitive lignin characterization of lignin–carbohydrate complexes (LCCs) from all types of lignocellulosic biomass, both natively and after various types of processing. In the present study, a previously reported fractionation approach that is applicable for eucalyptus (hardwood) and flax (non‐wood) was further improved by introducing an additional step of barium hydroxide precipitation to isolate the mannan‐enriched LCC (glucomannan‐lignin, GML), in order to suit softwood species as well. Spruce wood was used as the softwood sample. As indicated by the recovery yield and composition analysis, all of the lignin was recovered in three LCC fractions: a glucan‐enriched fraction (glucan‐lignin, GL), a mannan‐enriched fraction (GML) and a xylan‐enriched fraction (xylan‐lignin, XL). All of the LCCs had high molecular masses and were insoluble or barely soluble in a dioxane/water solution. Carbohydrate and lignin signals were observed in ¹H NMR, ¹³C CP‐MAS NMR and normal‐ or high‐sensitivity 2D HSQC NMR analyses. The carbohydrate and lignin constituents in each LCC fraction are therefore believed to be chemically bonded rather than physically mixed with one another. The three LCC fractions were found to be distinctly different from each other in terms of their lignin structures, as revealed by highly sensitive analyses by thioacidolysis‐GC, thioacidolysis‐SEC and pyrolysis‐GC.     

Recognition and avoidance of insecticide-treated Scots Pine (Pinus sylvestris) by Hylobius abietis (Coleoptera: Curculionidae): implications for pest management strategies

Abstract 1 The feeding preferences of Hylobius abietis (L.) were studied in a series of choice and no‐choice trials for insecticide‐treated food, time‐to‐death studies and arena trials. 2 Treatment of Scots Pine twigs with a pyrethroid insecticide, lambda‐cyhalothrin, was compared with twigs treated with imidacloprid, a neonicotinoid. 3 Clear avoidance of insecticide‐treated food sources, with strong evidence of selection for untreated food sources, was shown. 4 In addition, it took up to 3 weeks for H. abietis to die from insecticide poisoning when fed on treated food and, during this time, it was potentially capable of finding new untreated food sources.     

Variable growth and reproduction response of the spruce shoot aphid, Cinara pilicornis, to increasing ozone concentrations

Spruce shoot aphid, Cinara pilicornis Hartig (Homoptera: Lachnidae), is an aphid species that has shown enhanced performance on trees exposed to SO₂ or mixtures of air pollutants, whereas results with ozone have been contradictory. Using a 4-week chamber fumigation experiment, we tested how different population dynamic parameters of aphids are affected by ozone (O₃). Mean relative growth rate (MRGR), development time and reproduction rate of C. pilicornis were determined using 7h day-time O₃ concentrations of 0, 40, 80 and 160 ppb. Development period from birth to reproductive stage was fastest at 80 ppb during early shoot elongation, while reproduction and intrinsic rate of population increase was not significantly affected by ozone concentration. There was a significant negative correlation between ozone concentration and the MRGR of first instar nymphs in the third fumigation week. In feeding test performed on seedlings after fumigation, the MRGR was reduced on shoots which had been exposed to 80 ppb O₃. The results suggest that elevated O₃ concentration during early shoot elongation period may stimulate population development of C. pilicornis, but on maturing shoots, high O₃ concentration has a negative effect on aphid performance. This might be due to accelerated ageing of O₃ exposed shoots.