John S. Waterhouse

An improved technique for the batch processing of small wholewood samples to α-cellulose

Abstract We present details of a modified technique for the extraction of α-cellulose from wood samples. The revised technique, based upon the sodium chlorite oxidation method of Green (1963) utilises an ultrasonic bath and small Soxhlet thimbles to prepare α-cellulose from silvers of wholewood. These modifications facilitate the rapid batch processing of small wholewood samples to α-cellulose and yield a material with sufficient homogeneity as required for palaeoclimatic reconstruction.

Signal strength and climate relationships in 13C/12C ratios of tree ring cellulose from oak in southwest Finland

Annual oak (Quercus robur L.) latewood δ13C values are presented for the period 1895–1994 for two sites with different hydrological characteristics in southwest Finland. No appreciable anthropogenic 13C depletion was observed in the time-series. δ13C indices record high-frequency common forcing better than lower-frequency forcing. High-frequency fluctuations in the δ13C indices are highly correlated with climatic variables. Cross correlation analysis of tree ring δ13C indices and climate variables show that there is no significant difference (p < 0.01) in the climate response of tree ring δ13C indices between the two sites. This work demonstrates that significant climate signals are contained in isotopic measurements of trees whose ring-widths contain little or no such information.

Oxygen isotope ratios of oak in east England: implications for reconstructing the isotopic composition of precipitation

Annual latewood δ18O values from oak (Quercus robur L.) are presented for the period 1895–1994 for four trees growing in eastern England. We demonstrate, using the δ18O values of precipitation from Wallingford (1982–1994) and the longer time-series from Groningen (1965–1994), that the δ18O values of winter precipitation had the strongest influence on the δ18O values of tree-ring cellulose. The influence of winter precipitation on the spring/summer formed latewood may be explained by several factors: most soil water is replenished during the winter, water may take several months to penetrate the unsaturated zone, and oaks may sample water from lower in the profile during times of water stress. The δ18O values of oak latewood cellulose were also significantly (P<0.01) correlated with summer relative humidity. Therefore, although precipitation δ18O values may be altered by partial isotopic exchange with xylem water and the influence of stomatal conductance upon evapotranspiration, some of the original δ18O signature remains.

Oxygen and hydrogen isotope ratios in tree rings: how well do models predict observed values?

We have measured annual oxygen and hydrogen isotope ratios in the α-cellulose of the latewood of oak (Quercus robur L.) growing on well-drained ground in Norfolk, UK. We compare the observed values of isotope ratios with those calculated using equations that allow for isotopic fractionation during the transfer of oxygen and hydrogen from source water taken by the tree to cellulose laid down in the cambium. The equations constitute a model in which isotopic fractionation occurs during evaporative enrichment within the leaf and during isotopic change between carbohydrates and water in the trunk during cellulose synthesis. From the relationship between isotope ratios in precipitation and α-cellulose, we deduce that the source water used by the tree comprises a constant mixture of groundwater and precipitation, chiefly from the months of May, June and July of the growth year. By selection of isotopic fractionation factors and the degree of isotope exchange within the trunk, we are able to model the observed annual values of oxygen isotope ratios of α-cellulose to a significant level (r=0.77, P<0.01). When we apply the same model to hydrogen isotope ratios, however, we find that, although we can predict the average value over the time series, we can no longer predict the year-to-year variation. We suggest that this loss of environmental signal in the hydrogen isotopes is caused by differences in the kinetic isotope effects of the biochemical reactions involved in the fixation of hydrogen in different positions of the glucose molecule. Owing to these effects, the hydrogen isotope ratios of cellulose can vary in a way not anticipated in current models and hence may induce non-climatic ‘noise’ in the hydrogen isotope time series.

Spatial variability and temporal trends in water‐use efficiency of European forests

The increasing carbon dioxide (CO2 ) concentration in the atmosphere in combination with climatic changes throughout the last century are likely to have had a profound effect on the physiology of trees: altering the carbon and water fluxes passing through the stomatal pores. However, the magnitude and spatial patterns of such changes in natural forests remain highly uncertain. Here, stable carbon isotope ratios from a network of 35 tree-ring sites located across Europe are investigated to determine the intrinsic water-use efficiency (iWUE), the ratio of photosynthesis to stomatal conductance from 1901 to 2000. The results were compared with simulations of a dynamic vegetation model (LPX-Bern 1.0) that integrates numerous ecosystem and land-atmosphere exchange processes in a theoretical framework. The spatial pattern of tree-ring derived iWUE of the investigated coniferous and deciduous species and the model results agreed significantly with a clear south-to-north gradient, as well as a general increase in iWUE over the 20th century. The magnitude of the iWUE increase was not spatially uniform, with the strongest increase observed and modelled for temperate forests in Central Europe, a region where summer soil-water availability decreased over the last century. We were able to demonstrate that the combined effects of increasing CO2 and climate change leading to soil drying have resulted in an accelerated increase in iWUE. These findings will help to reduce uncertainties in the land surface schemes of global climate models, where vegetation-climate feedbacks are currently still poorly constrained by observational data.

The effect of fractionated Tagetes oil volatiles on aphid reproduction

The biological activity of essential oil volatiles from Tagetes minuta L. (Mexican marigold) against three aphid species was investigated in a series of laboratory experiments. The aphid species (Homoptera: Aphididae) studied were: Acyrthosiphon pisum (Harris) (pea aphid), Myzus persicae (Sulzer) (peach‐potato aphid), and Aulacorthum solani (Kaltenbach) (glasshouse and potato aphid). Tagetes minuta oil volatiles significantly reduced aphid reproduction (up to 100% after 5 days of exposure). The effect depended on the quantity of essential oil used, and varied with the aphid species tested. Pea aphids were the most susceptible. Tagetes minuta oil was fractionated by vacuum distillation. Fractions and three pure compounds (limonene, (Z)‐ocimene, and β‐caryophyllene) were tested using the same experimental technique. The chemical composition of the volatiles was investigated by headspace–solid phase microextraction–gas chromatography mass spectrometry (HS‐SPME‐GCMS), and the main constituents of the oil were identified. Overall, applied in equal quantity, fractions predominantly containing sesquiterpenes and oxygenated monoterpenoids were more effective in restricting aphid population growth than fractions predominantly containing monoterpenes. When tested as a pure compound, the sesquiterpene β‐caryophyllene produced a greater effect than the monoterpenes limonene and ocimene. The study demonstrates that T. minuta oil volatiles have potential for aphid control.

Gas-Chromatographic Analyses of the Subcaudal Gland Secretion of the European Badger (Meles meles) Part I: Chemical Differences Related to Individual Parameters

In many species, chemical signals are important in the context of intraspecific communication. European badgers (Meles meles) use the secretion of their subcaudal gland to mark both the environment and conspecifics. In this paper, we investigated the chemical composition of subcaudal gland secretions and how it varies among individuals according to group membership, season, sex, age, body condition, and reproductive status. We analyzed 66 samples by gas chromatography using a mass-spectrometer as detector. We found 110 different components, of which 21 were present in every profile. The chemical composition of the secretions proved to be highly individual-specific, but no single peak was found to be typical for one of the investigated categories (season, sex, etc.). Analyses of the relative area (% area) that every peak contributed to the overall profile area showed that, in general, group members have more similar profiles than do badgers from different groups. Composition varied over seasons and between sexes and was influenced by age, body condition, and reproductive status. We, therefore, conclude that the secretion not only encodes group membership and individuality as previously assumed, but might also convey information about fitness-related parameters.

Gas-chromatographic analyses of the subcaudal gland secretion of the European badger (Meles meles) part II: time-related variation in the individual-specific composition.

Individuality in body odors has been described in a variety of species, but studies on time-related variation in individual scent are scarce. Here, we use GC-MS to investigate how chemical composition of subcaudal gland secretions of European badgers (Meles meles) varies over days, seasons, and from year to year, and how secretions change with the length of time for which they are exposed to the environment. Samples were divided into subsamples—one was frozen immediately and the remaining ones frozen after 2, 6, 12, 24, and 48 hr, respectively—and many individual-specific characteristics of the scent-profiles remained stable over time. However, two components were negatively correlated with time, thus providing the possibility to determine the age of scent marks. The low variation found in scent profiles of samples collected from the same individual three days apart showed that the individual-specific scent is a true characteristic of the respective badger, and that trapping and subsequent sampling have little effect on the composition of subcaudal gland secretions. Long-term variation (i.e., over one year) in individual subcaudal scent profiles is not continuous, but periods of relative stability are followed by periods of rapid change, that can be related to badger biology. Annual variation between samples collected from the same individuals in winter 1998 and winter 1999, and in spring 1998 and spring 1999 was lower than seasonal variation. Therefore, the results of this study indicate the potential of an individual-specific scent signature in the subcaudal gland secretions of badgers evidencing that individual recognition is of high importance in this species.

Reliability of nitrogen dioxide passive diffusion tubes for ambient measurement: in situ properties of the triethanolamine absorbent.

Factors concerning NO2 uptake by the absorbent triethanolamine (TEA) in NO2 diffusion tubes are examined. Although the nominal freezing point of TEA is 17.9-21.2 degrees C, we show that, for a range of aqueous TEA solutions (0-20%, H2O), no freezing occurs even at -10 degrees C. Therefore NO2 collection efficiency is unlikely to be impaired by low temperature exposure. The recovery of TEA from the meshes of exposed samplers is determined as approximately 98%, even after 42 days, showing that the stability in situ of TEA is unaffected by long-term exposure. A model of a diffusion tube sampling array for simultaneous exposures, with a 0.1 m sampler spacing, shows that NO2 uptake by individual samplers is not affected by the presence of neighbouring tubes in the array. This is confirmed by sampler precision at two Cambridge sites. Four sampler preparation methods are compared for differences in NO2 uptake of exposed samplers. All methods employ TEA as absorbent, transferred by either dipping meshes in a TEA-acetone solution or pipetting aliquots of a TEA-H2O solution onto the meshes. For samplers prepared by three of the methods, no difference in NO2 uptake is found, but for samplers prepared using a 50% v/v TEA-H2O solution, a mean reduction of 18% is found. Students t-tests show that the difference is highly significant (P < or = 0.001). Reasons for the difference are discussed.

Volatile components in dorsal gland secretions of the collared peccary, Tayassu tajacu (Tayassuidae, Mammalia)

Secretions of the dorsal gland of free-ranging adult male and female collared peccaries (Tayassu tajacu) were analyzed by gas chromatography-mass spectrometry. Both sexes contain (2E,6E,10E)-geranylgeraniol; squalene (allE isomer); and the following isomers of springene, a diterpene homolog of β-farnesene: (3E,6E,10E)-α-springene, (3Z,6E,10E)-α-springene, and (6E,10E)-β-springene. A diterpene alcohol and an additional isomer each of squalene and springene also were observed. Straight- and branched-chain esters abound in the secretions of females, but they were not detected in males.