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More frequent drought episodes are expected to cause higher mortality in isohydric tree species such as pines, because individuals close their stomata early during drought in order to maintain constant needle water potentials. It has been suggested that trees delay the ensuing carbon starvation by actively storing carbon at the expense of growth ('bet hedging'). Because such a strategy is only adaptive in drought-prone regions, we hypothesise that the degree of carbon 'bet hedging' should differ between ecotypes., We repeatedly measured the allocation of biomass, starch and soluble sugars to needles, stem and roots in seedlings of nine populations of Pinus sylvestris and Pinus nigra along a gradient from Central Europe to the Mediterranean. During two consecutive growing seasons, seedlings grown from seed were exposed to factorial combinations of 4 months of drought (D1, D2) and ambient/elevated CO2 ( aCO2/ eCO2)., Drought-stressed pine seedlings did neither increase starch concentrations, nor change biomass production or experience lower mortality under eCO2 compared to aCO2. By the end of D2, seedlings from drier origin had accumulated more starch but at the same time also more biomass than seedlings from wetter origin., Surprisingly, seedlings acclimatised to dry conditions after D1 so that mortality dropped to zero and drought effects on needle starch ( P. sylvestris) and overall starch ( P. nigra), respectively, disappeared after D2., Synthesis. The absence of a trade-off between carbon storage (starch) and growth (biomass), and the patterns of mortality observed in seedlings growing under combined drought and eCO2 do not support the theory of carbon 'bet hedging' in isohydric Pinus sylvestris and Pinus nigra. Results suggest that reduced growth and acclimatisation minimised seedling mortality in the second year. Acclimatisation might thus enable pine seedlings to resist a moderate increase in summer drought frequency expected in the future. [ABSTRACT FROM AUTHOR]

This article presents a quantitative investigation regarding the composition of wet-heath vegetation in relation to aeration of the ground water and soil in certain communities on the north Hampshire-Berkshire border. The study shows that the cover of several species was closely related to the concentrations of carbon dioxide and hydrogen sulphide in the ground water, particularly Molinia coerulea, that cover decreased as the concentrations of these gases increased. Furthermore, it was concluded that their intercellular space system provided a free path for the oxygen diffusion from shoot to root.

1. Grasslands cover ~30% of the Earth's terrestrial surface and provide many ecosystem services. Many grasslands are heavily managed to maximize these services for human benefit, but the outcome of management is anticipated to be increasingly influenced by various aspects of climate change and elevated atmospheric CO2. The relative importance of global change vs. land management on grasslands is largely unknown. 2. A meta-analysis is used here to examine drivers at both scales primarily targeting services provided by grasslands relating to plant productivity (above- and below-ground biomass) and soil processes (nutrients and soil respiration) in 38 manipulative experiments published in the last decade. We specifically target effects of (i) single and combined land management practices (LMs), (ii) single and combined factors relating to broad-scale climate change and elevated CO2, and (iii) combined management practices and changes to climate and CO2. Collectively, this examines the general efficacy of global change models in predicting changes to grassland functioning. 3. We found that combinations of management practices had approximately double the explanatory power for variation in grassland services compared with individual or interactive effects of factors associated with climate change and CO2. These interacting management practices such as nutrient additions and defoliation predominantly influenced functions associated with productivity or biomass both below and above ground. The effects of interacting factors of climate and CO2 influenced a wider range of ecosystem functions, but the magnitude of these effects was relatively smaller. 4. Interactions between management practices or between climate change/CO2 factors always had higher explanatory power than any factor in isolation indicating that multivariate synergistic models of environmental change can better describe impacts on ecosystem function in plant communities (e.g. relative to univariate climate-based models). Given that the magnitude and direction (positive or negative) of the interactions varied widely, this also implies that the outcomes of these multivariate interactions can vary spatially, temporally or by immediate context (e.g. management prescriptions). 5. Synthesis. Although our work confirms how climate change and CO2 can affect many ecosystembased functional attributes, it suggests that combinations of LMs remain the dominant set of factors in determining the performance of grassland plant communities. Land management may thus be critical for influencing projected responses to future climate change and elevated CO2 in models of grassland function at least for factors relating to primary production. [ABSTRACT FROM AUTHOR]

Using experimental atmospheric CO enrichment, we tested for tree growth stimulation at the high-elevation treeline, where there is overwhelming evidence that low temperature inhibits growth despite an adequate carbon supply. We exposed Larix decidua (European larch) and Pinus mugo ssp. uncinata (mountain pine) to 9 years of free-air CO enrichment (FACE) in an in situ experiment at treeline in the Swiss Alps (2180 m a.s.l.). Accounting for pre-treatment vigour of individual trees, tree ring increments throughout the experimental period were larger in Larix growing under elevated CO but not in Pinus. The magnitude of the CO response in Larix ring width varied over time, with a significant stimulation occurring in treatment years 3-7 (marginal in year 6). After 9 years of treatment, leaf canopy cover, stem basal area and total new shoot production were overall greater in Larix trees growing under elevated CO, whereas Pinus showed no such cumulative growth response. The Larix ring width response in years 3-7 could have caused the cumulative CO effect on tree size even if no further stimulation occurred, so it remains unclear if responsiveness was sustained over the longer term. Larix ring width was stimulated more by elevated CO in years with relatively high spring temperatures and an early snowmelt date, suggesting that temperatures were less limiting in these years and greater benefit was gained from extra carbon assimilated under elevated CO. The magnitude of CO stimulation was also larger after relatively high temperatures and high solar radiation in the preceding growing season, perhaps reflecting gains due to larger carbon reserves. Synthesis. Contrasting above-ground growth responses of two treeline tree species to elevated CO concentrations suggest that Larix will have a competitive advantage over less responsive species, such as co-occurring Pinus, under future CO concentrations. Stimulation of Larix growth might be especially pronounced in a future warmer climate. [ABSTRACT FROM AUTHOR]

1 The effect of elevated CO2 on species’ performance was investigated in communities composed of five annual weeds that are characteristic of early old field succession in central Europe:Centaurea cyanusL.,Matricaria chamomillaL.,Silene noctifloraL.,Papaver rhoeasL. andLegousia speculum-veneris(L.) Chaix.2 The experiment was based on a simplex design, repeated at two overall levels of initial stand density, to give a wide range of five-species communities across which the initial composition and species abundance varied systematically.3 A multivariate method, based on analysing the differences in relative growth rates (RGRD) between pairs of species, was extended for use with more than two species, in order to assess the relative importance of various determinants of change in stand biomass composition.4 On average,Centaurea(54.6% of final yield) gave the highest yield, followed byMatricaria(22.9%),Silene (16.9%),Legousia(3.1%) andPapaver(2.7%).5 The major determinants of change in community structure were species identity and CO2 level. Elevated CO2 significantly changed community composition towards the previously more poorly performing speciesSilene,LegousiaandPapaver.6 Despite strong effects of intra- and interspecific competition on individual species performance, species’ initial abundance had relatively little impact on the change in community composition. Most cases where such effects were significant involvedSilene: performance ofPapaverwas poorer in communities with higher initial presence ofSileneand higher initial abundances ofCentaureaandMatricariaalways facilitated performance ofSilene.7 These new methods proved a powerful system for identifying the biotic and abiotic factors determining change in biomass composition in multispecies communities.Journal of Ecology(2005)doi: 10.1111/j.1365-2745.2005.00999.x [ABSTRACT FROM AUTHOR]

1 Mathematical proofs show that rate estimates, for example of mortality and recruitment, will decrease with increasing census interval when obtained from censuses of non-homogeneous populations. This census interval effect could be confounding or perhaps even driving conclusions from comparative studies involving such rate estimates.2 We quantify this artefact for tropical forest trees, develop correction methods and re-assess some previously published conclusions about forest dynamics.3 Mortality rates of> 50 species at each of seven sites in Africa, Latin America, Asia and Australia were used as subpopulations to simulate stand-level mortality rates in a heterogeneous population when census intervals varied: all sites showed decreasing stand mortality rates with increasing census interval length.4 Stand-level mortality rates from 14 multicensus long-term forest plots from Africa, Latin America, Asia and Australia also showed that, on average, mortality rates decreased with increasing census interval length.5 Mortality, recruitment or turnover rates with differing census interval lengths can be compared using the mean rate of decline from the 14 long-term plots to standardize estimates to a common census length usingλ corr = λ ×  t0.08, whereλ is the rate andtis time between censuses in years. This simple general correction should reduce the bias associated with census interval variation, where it is unavoidable.6 Re-analysis of published results shows that the pan-tropical increase in stem turnover rates over the late 20th century cannot be attributed to combining data with differing census intervals. In addition, after correction, Old World tropical forests do not have significantly lower turnover rates than New World sites, as previously reported. Our pan-tropical best estimate adjusted stem turnover rate is 1.81 ± 0.16% a−1 (mean ± 95% CI,n = 65).7 As differing census intervals affect comparisons of mortality, recruitment and turnover rates, and can lead to erroneous conclusions, standardized field methods, the calculation of local correction factors at sites where adequate data are available, or the use of our general standardizing formula to take account of sample intervals, are to be recommended.Journal of Ecology(2004) 10.1111/j.0022-0477.2004.00923.x [ABSTRACT FROM AUTHOR]

Summary 1 The decomposition rate of litter mixtures can depend on interactions between compounds in the component species, i.e. in litter chemistry. Differences in litter N concentration are likely to lead to positive interaction (i.e. faster than expected decomposition) and differences in phenolic concentrations to a negative interaction. These interactions may become less positive (or more negative) when the litter is produced under elevated atmospheric CO2 concentrations. 2 We measured respiration rates of litter from two contrasting species pairs, produced under ambient and elevated CO2 . 3 As expected, mixtures of Calamagrostis epigejos and Vicia lathyroides , which differed strongly in litter N concentration, decomposed faster than expected, but the interaction disappeared under elevated CO2 . 4 Despite the large difference in litter N concentration between Sphagnum recurvum and Carex rostrata , no interaction was observed in the ambient CO2 litter mixtures, and under elevated CO2 , there was an unexpected positive interaction. 5 Interactions in litter mixtures can therefore change under elevated CO2 , albeit not in a predictable manner, which would require correct prediction of species-specific litter chemistry and its response to elevated CO2 . [ABSTRACT FROM AUTHOR]

Examines the validity of a pH-drift technique for calculating free carbon dioxide and bicarbonate compensation points for a range of freshwater macrophytes and photoplankters. Variation in the free carbon dioxide point of Hippuris vulgaris; Seasonal changes in bicarbonate compensation points; Overlap in the uptake abilities of macrophytes and phytoplankters.

The article presents a study on the association between alkaline phosphatase activity and freshwater bacteria and algal populations. The study involves a survey on the Windermere North and South Basins and Esthwaite Water at the south end of the lake, and the establishment on the association between the bacteria and phytoplankton. It was found out that the carbon dioxide produced by the bacterial populations related with the algae could be responsible for the initiation or simulation of an algal bloom in the natural environment.

The article discusses some comparative studies on photosynthesis, respiration and water relations of 10 arid zone and two semi-arid zone plants under winter and late summer climatic conditions. Data on carbon dioxide exchange and water relations were obtained for eight arid and two semi-arid zone native plant species of Western Australia. In late summer, all species showed a positive carbon dioxide balance which indicates that there is sufficient soil water in deeper soil layers. All the species tested possess a high heat resistance and are well suited to their natural environment.

The article presents a study on the biomass cycle of tropical rain forests. It mentions that since rain forests are climax communities, it can be expected that the rates of production and decomposition of organic matter are equal. The rate of soil respiration including the cycle of carbon dioxide can be used to measure the net productivity of rain forests. Plastic cylinders containing potassium hydroxide were used to absorb carbon dioxide in the area. The experiment was carried out from March 12 to 16, 1969 at Tjibodas, Java. It found that decomposition of organic matter is faster in tropical rain forests. It also recommends a longer period for the experiment. An overview of the results of the study is provided.

The article presents a study which assesses the interaction of the daily compensation period (DCP) of mosses and lichens and the ecological ranges of tree species in Japan. It states that some of the species were not able to reach the compensation point due to the negative level of carbon dioxide on cloudy and rainy days. It reveals that mosses and lichens require two and four hours to reach the compensation point. It concludes that the species could not grow below their ordinary habitats because their vitality may be impaired.

The article examines the seasonal fluctuations in the oxygen and carbon dioxide concentrations in beech litter in connection to the salt uptake of beech mycorrhizas. To estimate the oxygen and carbon dioxide concentrations in the litter layer of beech woods in which mycorrhizal roots are abundant, a method was developed in conjunction with experiments studying the uptake of phosphate by excised mycorrhizal roots of Fagus sylvatica. The two types of experiments conducted included an examination of the effect of oxygen concentration on the uptake of phosphorus and its distribution between fungus and host and the determination of the distribution of phosphorus between the fungus and host.

The article presents a discussion about the rain forest of Southern Nigeria based from the ecological studies conducted on the said region. The article explores the climate, topography, ecology, and botany of the rain forest through the various studies and includes details regarding environmental aspects such as the carbon dioxide concentration of the environment, light, temperature and humidity, and soils. The article ends with a summary which states that in the area concerned, primary forest will be established again on abandoned land after cultivation.

The article presents a study regarding atmospheric environmental conditions of the rain forest in southern Nigeria. Carbon dioxide concentration in the tropical rain forest undergrowth and temperate woods was not observed to exceed 0-06% by volume. There are no significant differences between the concentrations in primary and secondary forests. Data from the thermohygrograph records of the temperature and humidity conditions in the tree tops and undergrowth are presented. Discussion regarding the possible effects of Nigeria's environmental conditions on the life of undergrowth plants is also presented.

The article a simple modification of the polymer membrane electrode which has proved to be convenient for measurements of the partial pressure of carbon dioxide in the soil. The system is not suitable for following short-term fluctuations in carbon dioxide pressure and has the disadvantage that a considerable volume of carbon dioxide is lost from the soil. The device used consists of a Pyrex test tube with a hole blown in the side near the base and covered with 0-005-inch thick polytetrafluoroethylene adhesive-backed tape.