A key need of the global change research community is to be able to synthesize the data collected by scientists from a wide range of disciplines and use it to make predictions about our future environment. In an agricultural and forestry context, this will allow predictions of yields under elevated atmospheric CO2 levels and/or changed climate using data from studies of both the direct effects of global change on plant growth and physiology and indirect effects on soil fertility, water resources, pests and diseases.

A conference held at the University of Reading, UK in September 1999, and organized under the auspices of Focus 3 (Global Change Impact on Agriculture, Forestry and Soils; http://mwnta.nmw.ac.uk/GCTEFocus3) of the IGBP Core Project “Global Change and Terrestrial Ecosystems” addressed many of these issues.

Caecal contents of 3-month-old rabbits were analysed and used as inoculi of cultures supplied with plant proteins (gluten, gliadin, zein), mucin, casein, ribonucleic acid (RNA) and glucose. The caecal digesta contained dry matter, total N, protein, trichloroacetic acid (TCA)-soluble N and NH3-N at 234, 10·2, 42·6, 3·2 and 0·27 mg/g (on average), respectively. One g of the caecal digesta contained 180 μmol of glycine equivalents of amino acids in TCA-soluble fraction. Because ninhydrin reaction was almost three times greater after HCl hydrolysis, peptides rather than amino acids were the primary component in this fraction. Urea concentration was only 2·3 μg N/g.

Net production of volatile fatty acids (VFA) in cultures with casein and mucin was higher than in cultures with gluten, gliadin, zein and RNA. Zein was the least fermentable substrate tested. Acetate was the principal fermentation end-product, followed mostly by butyrate and propionate. Branched-chain VFA proportions in VFA produced in cultures with casein, gluten, gliadin and zein were higher than in those supplied with glucose, mucin and RNA. In the former cultures, branched-chain VFA accounted for 10·2–17·7 molar % in the total VFA. In cultures supplied with proteins, there was a significant correlation between methane and VFA production, and between VFA and ammonia. The highest concentration of ammonia was found in cultures with casein. Production of methane was increased on glucose and nitrogenous substrates containing a carbohydrate moiety (mucin, RNA). It can be concluded that the caecal contents of rabbits are rich in nitrogenous compounds. The caecal fermentation of nitrogenous substrates supplies nutrients both for caecal microorganisms (branched-chain VFA, NH3) and for the host (VFA).

The concentration of n-alkanes in the cuticular wax of plants can be used to estimate the composition of the diet selected by free-ranging animals. The aims of this study were to characterize the n-alkane profiles of developing leaves and evaluate the degree of chemical discrimination between six browsed broadleaf tree species: European ash (Fraxinus excelsior L.), flowering ash (Fraxinus ornus L.), hornbeam (Carpinus betulus L.), hazel (Corylus avellana L.), mountain ash (Sorbus aucuparia L.) and beech (Fagus sylvatica L). The effect of the stage of development was examined by considering five different vegetative stages: dormant bud (DB), late bud (LB), young leaf (YL), mature leaf (ML) and senescing leaf (SL). Five samples per each vegetative stage and species, gathered in a mixed woodland of the Italian Eastern Alps between February and October, were analysed for their n-alkane concentrations (C23–C36).

The residual coefficient of variation was 15·5% on average for the individual n-alkanes considered. There were noticeable differences in individual and total n-alkanes content between species. In particular, C27 was the predominant n-alkane in beech and C33 was found in high proportions in the two species of Fraxinus; hazel and flowering ash had a higher total n-alkanes content than the overall mean, while the lowest values were found in hornbeam and beech. The n-alkane profile also underwent important changes during the vegetative development, with different extent and direction according to the species. In the three successive leaf stages, a tendency for a progressive increase in the longest chain homologues was observed. In any case, the young leaf stage differed most from the contiguous stages.

Canonical discriminant analysis indicated that the n-alkane profile of buds and leaves were mathematically distinguishable and the chemical differences between species were persistent over the plant vegetative development.

Analyses were made on birth weight of 2706 kids (six genetic groups) under confinement conditions in the arid zone of northern Mexico, to study the effect of air temperature (mean annual temperature = 21·1 °C) during gestation on this trait. The relationship of environmental temperature at kidding and survival of kids was also studied. Birth weight was significantly negatively related to mean dry bulb air temperature during gestation (reduction of 40±3 g for 1 °C increase in mean air temperature during gestation; r = −0·22; P < 0·01), although temperature only explained 5% of the variance of kid birth weight. Mean minimum temperatures (< 4 °C) 5 days after birth significantly reduced kid survival (83% v. 89–93% for kids born when temperatures were above 4 °C; P < 0·01). Air temperatures between 30 and 41 °C during the perinatal period did not affect (P > 0·05) survival rate. These results suggest that newborn kids seem to be relatively resistant to high air temperature, but are fairly susceptible to cold stress. Also, birth weight of kids from goats exposed to high air temperature during pregnancy was marginally reduced, although this was of limited economic significance.

Thirty-two pregnant ewes (Saudi breeds) selected during 1998 and 1999, were studied throughout the whole gestational length and around parturition. Concentrations (mean±S.E.) of plasma progesterone (3·9±0·28 ng/ml), oestradiol-17β (20·5±2·33 pg/ml) and cortisol (4·8±0·58 ng/ml) remained fairly constant throughout the early stages of pregnancy. Characteristic changes in these steroids were evident during the prepartal period involving a steady decrease in plasma progesterone beginning 8 days before parturition; a remarkably consistent increase in oestradiol-17β 4–6 days prior to delivery, peaking in excess of 250 pg/ml at the birth day; and a fivefold increase to 23·7±2·12 ng/ml in plasma cortisol 2 days preceding delivery, showing a large increase during the day of lambing. The timing of the marked reduction in the platelet count and the coagulation screening tests including prothrombin time (PT), activated partial thromboplastin time (APTT) and thrombin time (TT), during the prepartal period, were significantly correlated with the temporal changes in the circulating steroid hormone concentrations. The results suggest that the characteristic prepartal hormonal changes might provide the basis for shifting the fairly balanced coagulable state throughout gestational periods to a mild to moderate degree of hypercoagulability during parturition which is needed to limit the possible intra- and post-partum uterine haemorrhage.

This group, which is concerned with the applications of mathematics to agricultural science, was formed in 1970 and has since met at approximately yearly intervals in London for one-day meetings. The thirty-second meeting of the group, chaired by Professor D. Scholefield of the Institute of Grassland and Environmental Research, North Wyke, was held in the Kohn Centre at the Royal Society, 6 Carlton House Terrace, London on Friday, 14 April 2000 when the following papers were read.