The role of closed ecological systems in carbon cycle modelling

Acquiring a mechanistic understanding of the role of the biotic feedbacks on the links between atmospheric CO2 concentrations and temperature is essential for trustworthy climate predictions. Currently, computer based simulations are the only available tool to estimate the global impact of the biotic feedbacks on future atmospheric CO2 and temperatures. Here we propose an alternative and complementary approaches by using materially closed and energetically open analogue/physical models of the carbon cycle. We argue that there is potential in using a materially closed approach to improve our understanding of the magnitude and sign of many biotic feedbacks, and that recent technological advance make this feasible. We also suggest how such systems could be designed and discuss the advantages and limitations of establishing physical models of the global carbon cycle

The movement of ground water, as influenced by geological factors, and its significance

An analysis of ground-water movement based on the individual components of Darcy's Law has been undertaken with reference to aquifers in England&dot; Variations in hydraulic gradient, in the parameters defining the physical and mechanical characteristics of an aquifer, in geological structure and in physical properties of ground water will modify fluid velocities. Although the hydraulic conductivity of porous media can be stated in terms of these parameters, complexities of geology prevent an adequate statement other than under restricted conditions Around a discharging or recharging well, non-steady and steady state flow has been analysed for the determination (in situ) of the formation constants of an aquifer, both real and apparent values being derived. Critical analysis of data in relationship to rate of abstraction, time since discharge commenced or ceased and distance to observation well has been carried out, variations in the formation constants usually occurring in defined trends. The inter-relationship of the formation constants and their importance in hydrological surveys has been discussed. Real variations in transmissibility have been determined and diagrams compiled to indicate regional trends. Analysis of yield-depression curves has led to the assemblage of type and breakaway curves" from which the formation constants of the aquifer can be derived within defined statistical probability levels. Factual data relating to ground-water movement have been analysed and the results presented on a probability basis, wherever possible. This method is considered to be important in hydrogeological studies, Particular emphasis has been placed on ground-water conditions in the Chalk due to its importance as a source of water supply. The significance of fluid movement in relationship to exploitation of ground-water resources and to problems of overdevelopment has been considered. Progressive changes in ground-water chemistry, under both natural and artificial conditions, have been established.<p

DEMOGRAPHY OF A RECOVERY: TRACKING THE REBOUND OF LITTLE BROWN BAT (MYOTIS LUCIFUGUS) POPULATIONS

As the emergence of novel diseases in wildlife becomes more common, a better understanding of the impact of disease on populations and their demographic rates will be critical for their conservation. Populations naturally fluctuate over time as a function of the rates of birth, death, immigration, and emigration, while at the individual level the chances of mortality and reproduction may be influenced by age and physiological condition. Diseases, particularly emerging infectious diseases, can cause immediate and severe changes in demographic rates. While some populations and species may go extinct due to high mortality rates, others may persist in smaller, but stable numbers by evolving, adapting, or demographically responding. Diseases can also have sublethal impacts that may differentially effect individuals, sexes, or ages and may threaten the viability of a population. White-nose syndrome (WNS) is a recently emerged fungal disease that infects hibernating bats in North America. Little brown bat (Myotis lucifugus) populations have declined in some areas by more than 90%, but have stabilized in remnant winter and summer colonies. In this study I investigated the long-term impacts of WNS and changes in demographic rates on little brown bat populations in New England. Age-related demographic rates are often important to understand for conservation and management, but are hard to determine in long-lived species with no clear external indicators of age. In Chapter 1, I investigated whether relative telomere length could be used as a genetic marker of age for little brown and big brown bats (Eptesicus fuscus). I found that in big brown bats, there was a quadratic relationship with chronological age, where middle-aged individuals had the longest telomeres. For little brown bats, individuals with more wing damage due to WNS had shorter telomeres, suggesting an impact of disease on their physiological condition. Finding no relationship of telomere length to chronological age, little brown bats should, for now, continue to be grouped as either juveniles or adults, which may be appropriate as there is little evidence for senescence in Myotis bats. In Chapter 2, I compared yearling (one-year-old) and adult reproductive rates using banding records from an extensive study at one summer maternity colony prior to WNS and from work at eight colonies since WNS emerged. I found that yearling reproductive rates have significantly increased and are now very similar to the observed adult reproductive rate of 0.95, suggesting a shift in life-history related to age of first reproduction. I also found that reproductive phenology has advanced by 6–10 days, most likely driven by warming spring temperatures, but also potentially as a response to WNS. Earlier reproduction could benefit offspring by giving them more time to accumulate fat stores before hibernation, thus increasing the chances of first-winter survival and reproduction as yearlings. Bats with more wing damage due to WNS had later parturition dates, suggesting that the energetic costs of infection delay reproduction for individuals, but are not delaying the overall timing of reproduction at the population level. Long-term survival rates are also important to understand for population modeling. In Chapter 3, I used mark-recapture and colony count data to estimate survival in three different types of population models. I found that survival estimates were similar among models and showed that survival probabilities were lowest immediately after WNS invasion, but have since returned to or surpassed pre-WNS survival probabilities. Juvenile survival was lower than adult survival, but was generally higher than those reported from pre-WNS. I then used these survival estimates and the reproductive rates from Chapter 2 to conduct population viability analyses under different management strategies, which showed colony growth even without additional human intervention. These findings suggest that little brown bat populations in New England have responded to WNS and are beginning to rebound, but some management actions that boost survival could help ensure long-term recovery

Substrate quality and the temperature sensitivity of soil organic matter decomposition

Copyright © 2008 Elsevier. NOTICE: This is the author’s version of a work accepted for publication by Elsevier. Changes resulting from the publishing process, including peer review, editing, corrections, structural formatting and other quality control mechanisms, may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Soil Biology and Biochemistry, 2008, Vol. 40, Issue 7, pp. 1567 – 1574 http://dx.doi.org/10.1016/j.soilbio.2008.01.007Determining the relative temperature sensitivities of the decomposition of the different soil organic matter (SOM) pools is critical for predicting the long-term impacts of climate change on soil carbon (C) storage. Although kinetic theory suggests that the temperature sensitivity of SOM decomposition should increase with substrate recalcitrance, there remains little empirical evidence to support this hypothesis. In the study presented here, sub-samples from a single bulk soil sample were frozen and sequentially defrosted to produce samples of the same soil that had been incubated for different lengths of time, up to a maximum of 124 days. These samples were then placed into an incubation system which allowed CO2 production to be monitored constantly and the response of soil respiration to short-term temperature manipulations to be investigated. The temperature sensitivity of soil CO2 production increased significantly with incubation time suggesting that, as the most labile SOM pool was depleted the temperature sensitivity of SOM decomposition increased. This study is therefore one of the first to provide empirical support for kinetic theory. Further, using a modelling approach, we demonstrate that it is the temperature sensitivity of the decomposition of the more recalcitrant SOM pools that will determine long-term soil-C losses. Therefore, the magnitude of the positive feedback to global warming may have been underestimated in previous modelling studies

Trace element geochemistry of Wallrock alteration in the Pennine Orefield's and Cumberland iron field

The variations in the trace elements Rb, F, Pb, Sr, Mn, Zr, Zn, Cu, Ni and Fe have been studied in limestone wallrocks next to lead - zinc - fluorite - barite mineralization in the Northern Pennine Orefield and Derbyshire Orefield; and next to haematite orebodies in the Cumberland Ironfieldo. Trace element aureoles have also been investigated in sandstones and shales. An analytical technique for the determination of fluorine in limestones was developed using the optical emission spectrograph, and found to give satisfactory results. Standard X-ray fluorescence techniques were employed for the determination of the other trace elements. The petrology, mineralogy and chemistry of certain aureoles have been examined in detail. The heavy metal content of the limestone wallrocks in the majority of cases, illustrates widespread and irregular dispersion patterns. It is suggested that migration of the metals has taken place through fractures developed prior to, or contemporaneously with, the mineralization. Diffusion of the heavy metals has occurred into massive country rocks at certain localities and results in a logarithmic decrease in concentration away from the ore and more restricted aureoles. The width of the dispersion patterns varies next to the veins, but in general a wider aureole is developed in Derbyshire than in the Alston Block. It is concluded that, at the time of emplacement, the Derbyshire veins were at a higher pressure than the veins in the Alston Block, but that variation in the temperature of the ore solutions was not an important parameter controlling the migration of the heavy metals. The alteration of the limestone wallrocks is discussed and suggestions are put forward to explain the possible origin of some of the replacement minerals. Adjacent to the veins, a depletion in strontium is recorded. This is related to the recrystallisation of the calcite which has liberated strontium from the crystal lattice. The strontium content of the Great Limestone and the D(_2) Limestone, the respective sampling horizons in the Alston Block and the Derbyshire area, are considerably different and it is concluded that this reflects either the original aragonite content of the limestones, or differing conditions of deposition in the two areas. Migration by diffusion into massive country rocks has occurred in the Cumberland Ironfield to far greater distances than in the Pennine Orefields; the depletion of strontium is also more extensive. It is suggested that the ore solutions were emplaced at higher temperatures than in the Pennine Orefields. The trace element aureoles in sandstone and shale wallrocks indicate that the heavy metals have been migrated through fractures, as irregular and widespread patterns are observed. A comparative study was conducted on the trace element variations which occur next to the veins which intersect the Whin Sill (quartz- dolerite) in the Alston Block. Contrary to previously reported widespread dispersion aureoles in igneous rocks, a narrow aureole is formed where diffusion has taken place into the wallrocks. A profound chemical change between the unaltered and altered quartz- dolerite has occurred where CO(_2), K(_2)O and H(_2)O are enriched, while Na(_2)O, MgO, total iron and CaO are depleted. The quartz-dolerite has been converted into a carbonate and clay-rich rock called the White Whin. The chemical and mineralogical variations are related to the variations in the trace elements where Rb, Ba, Pb and Zn are concentrated while Cu, Ni, Zr, Sr, V and Cr are depleted next to the veins. A geological and geophysical survey over altered and mineralised quartz-dolerite dykes at Closehouse mine, Lunedale near Middleton-in- Teesdale has produced results, which, it is hoped, will elucidate the complexities of the area

COMBINED USE OF OPEN-AIR AND INDOOR FUMIGATION SYSTEMS TO STUDY EFFECTS OF SO-2 ON LEACHING PROCESSES IN SCOTS PINE LITTER

Both an open-air fumigation system and a laboratory-based system were used to expose decomposing Scots pine (Pinus sylvestris L.) needles to controlled concentrations of SO2 (arithmetric mean less-than-or-equal-to 48 nl litre-1) during a period, in total, of 301 days. The experimental design involved reciprocal litter transplants from 'clean' to 'polluted' air and vice versa, using the two fumigation systems. The objectives were (1) to observe the effects of SO2 on leachate and litter chemistry, (2) to assess whether pollution-induced changes are reversible in clean air, and (3) to test the suitability of small-scale fumigation chambers (litter microcosms) compared with open-air systems in soil studies.Through the formation of SO4(2-) ions, dry-deposited SO2 exhibited a marked capacity to remove 'base' cations (Ca2+, Mg2+ and K+) from decomposing pine needles, and also to acidify litter leachates (as indicated by proton fluxes from the litter). When litter was transferred from polluted air (48 nl litre-1 SO2, in the open-air system) to either clean or polluted air in the laboratory, the effects of prior exposure to SO2 on leachate composition were still evident even after 86 days: the role of base cation depletion within the litter, caused by SO42- -induced leaching, is discussed.Data for SO42- fluxes in leachates collected from the small-scale chambers indicated that dry deposition velocities for SO2 were not anomalously high within this fumigation system. It is therefore concluded that microcosm studies can provide information complementary to the open-air fumigation approach in soils research.</p

The Cast Structure of High-Speed Steel

The cause and effects of the formation of coarse cellular carbides in high-speed steels are reviewed and attention is drawn to possible methods of investigating the problem and perhaps eliminating it

Rapid turnover of hyphae of mycorrhizal fungi determined by AMS microanalysis of C-14

Processes in the soil remain among the least well-characterized components of the carbon cycle. Arbuscular mycorrhizal (AM) fungi are ubiquitous root symbionts in many terrestrial ecosystems and account for a large fraction of photosynthate in a wide range of ecosystems; they therefore play a key role in the terrestrial carbon cycle. A large part of the fungal mycelium is outside the root ( the extraradical mycelium, ERM) and, because of the dispersed growth pattern and the small diameter of the hyphae (<5 micrometers), exceptionally difficult to study quantitatively. Critically, the longevity of these. ne hyphae has never been measured, although it is assumed to be short. To quantify carbon turnover in these hyphae, we exposed mycorrhizal plants to fossil ("carbon-14 - dead") carbon dioxide and collected samples of ERM hyphae ( up to 116 micrograms) over the following 29 days. Analyses of their carbon-14 content by accelerator mass spectrometry (AMS) showed that most ERM hyphae of AM fungi live, on average, 5 to 6 days. This high turnover rate reveals a large and rapid mycorrhizal pathway of carbon in the soil carbon cycle