Integrating climatic change and forests: Economic and ecologic assessments

Effective policies for dealing with anticipated climatic changes must reflect the two-way interactions between climate, forests and society. Considerable analysis has focused on one aspect of forests - timber production - at a local and regional scale, but no fully integrated global studies have been conducted. The appropriate ecological and economic models appear to be available to do so. Nontimber aspects of forests dominate the social values provided by many forests, especially remote or unmanaged lands where the impacts of climatic change are apt to be most significant. Policy questions related to these issues and lands are much less well understood. Policy options related to afforestation are well studied, but other ways the forest sector can help ameliorate climatic change merit more extensive analysis. Promising possibilities include carbon taxes to influence the management of extant forests, and materials policies to lengthen the life of wood products or to encourage the substitution of CO₂-fixing wood products for ones manufactured from less benign materials.     

Phase equilibria in the system K2O-FeO-MgO-Al2O3-SiO2-H2O-CO2 and the stability limit of stilpnomelane in metamorphosed Precambrian iron-formations

The phase relations of Al- and Fe-bearing silicates in the system K₂O-FeO-MgO-Al₂O₃-SiO₂-H₂O-CO₂, in the presence of quartz and magnetite, are discussed on the basis of mineralogic and petrologic data from Precambrian iron-formations and blueschist facies meta-ironstone from the Franciscan Formation, California. These relations allow an estimation of the physiochemical conditions during low-grade metamorphism of iron-formations. Petrologic data together with available experimental and predicted thermodynamic data on the associated minerals place the upper stability limit of stilpnomelane in iron-formations at about 430–470° C and 5–6 kilobars. Fe-end member stilpnomelane can persist to a maximum temperature of 500° C and pressures up to 6–7 kilobars, although it is unlikely to occur in metamorphosed iron-formations. In iron-formation occurrences the stilpnomelane stability field is bordered by four equilibrium reactions with the assemblages stilpnomelane-zussmanite-chlorite-minnesotaite, stilpnomelane-zussmanite-chlorite-grunerite, stilpnomelane-biotite-chlorite-grunerite, and stilpnomelane-biotite-almandine-grunerite. The stability field is reduced by increasing X(CO₂) and X _Mg ^Stil , and is also a function of a(K ⁺)/ a(H ⁺) in the metamorphic fluid. If the value of a(K ⁺)/ a(H ⁺) is smaller than that defined by the above assemblages, stilpnomelane decomposes to chlorite, but if larger, it is replaced by biotite. At pressures less than 4 kilobars, the zussmanite field is restricted to a very high value of a(K ⁺)/a(H ⁺) (> 5.0 in log units at 1.0 kilobar) where iron-formation assemblages are not stable.     

The Queens' flare: Its structure and development; precursors,pre-flare brightenings,and aftermaths

We continue previous research on the limb flare of 30 April, 1980, 20:20 UT, observed in X-rays by several instruments aboard the Solar Maximum Mission (SMM). It is shown quantitatively that the flare originated in an emerging magnetically confined kernel (diameter ～ 20″) which existed for about ten to fifteen minutes, and from which energetic electrons streamed, in at least two injections, into a previously existing complicated magnetic loop system thus forming a less bright but extended and long-lived tongue. The tongue had a length of ～ 35 000 km and lasted ～ 90 min in X-rays (～ 10 keV); at lower energies (～ 0.7 keV) it was larger (～ 80 000 km) and lasted longer. The total number of energetic electrons (≈ 10³⁷) initially present in the kernel is of the same order as the number present in the tongue after the kernel's decline. This gives evidence that the energetic electrons in the tongue originated mainly in the kernel. The electron number densities in the kernel and tongue at maximum brightness were ～ 4.5 × 10¹¹ and ～ 1 × 10¹¹ cm^#X2212;3, respectively. During the first eight minutes of its existence the tongue was hotter than the kernel, but it cooled off gradually. Its decline in intensity and temperature was exponential; energy was lost by radiation and by conduction through the footpoints of the loop system. These footpoints have a cross-section of only ～ 3 × 10⁶ km². This small value, as well as photographs in a Civ UV emission line, suggests a highly filamentary structure of the system; this is further supported by the finding that the tongue had a ‘filling factor’ of ～ 10^#X2212;2. Several faint X-ray brightenings (? 0.005 of the flare's maximum intensity) were observed at various locations along the solar limb for several hours before and after the flare. At ～ 30 min before the flare's onset a faint (? 0.02) flare precursor occurred, coinciding in place and shape with the flare. First the kernel precursor was brightest but the tongue precursor increased continuously in brightness and was the brightest part of the precursor some 10–15 min after the first visibility of the kernel precursor, until the start of the main flare. This suggests (weak) continuous electron acceleration in the tongue during a period of at least 30 min. The main flare was caused by strong emergence of magnetic field followed by two consecutive field line reconnections and accelerations in a small loop system, causing footpoint heating. Subsequently plasma streamed (convectively) into a pre-existing system of larger loops, forming the tongue.     

Large turbulent elements in supergiant photospheres

During the cool phase of the super-supergiant HR 8752, which happened around 1973, when the star's spectral type was K2...K5 Ia⁺, the most probable vertical extent of the main turbulent elements in the star's photosphere was about 6 times the density scale height, which is about half the stellar radius. In early-type photospheres (class Ia) it is about 10 times the atmospheric density scale height (about 0.25 of the stellar radius), while in less extreme (luminosity class Ib) medium-type supergiants the most probable vertical extent of the elements is approx. 8 times the density scale height (0.05R). Large turbulent elements are apparently a common feature in supergiant photospheres; the more extreme the supergiant the larger the relative size of the eddies.     

Ancient geochemical cycling in the Earth as inferred from Fe isotope studies of banded iron formations from the Transvaal Craton

Variations in the isotopic composition of Fe in Late Archean to Early Proterozoic Banded Iron Formations (BIFs) from the Transvaal Supergroup, South Africa, span nearly the entire range yet measured on Earth, from –2.5 to +1.0‰ in ⁵⁶Fe/⁵⁴Fe ratios relative to the bulk Earth. With a current state-of-the-art precision of ±0.05‰ for the ⁵⁶Fe/⁵⁴Fe ratio, this range is 70 times analytical error, demonstrating that significant Fe isotope variations can be preserved in ancient rocks. Significant variation in Fe isotope compositions of rocks and minerals appears to be restricted to chemically precipitated sediments, and the range measured for BIFs stands in marked contrast to the isotopic homogeneity of igneous rocks, which have δ⁵⁶Fe=0.00±0.05‰, as well as the majority of modern loess, aerosols, riverine loads, marine sediments, and Proterozoic shales. The Fe isotope compositions of hematite, magnetite, Fe carbonate, and pyrite measured in BIFs appears to reflect a combination of (1) mineral-specific equilibrium isotope fractionation, (2) variations in the isotope compositions of the fluids from which they were precipitated, and (3) the effects of metabolic processing of Fe by bacteria. For minerals that may have been in isotopic equilibrium during initial precipitation or early diagenesis, the relative order of δ⁵⁶Fe values appears to decrease in the order magnetite > siderite > ankerite, similar to that estimated from spectroscopic data, although the measured isotopic differences are much smaller than those predicted at low temperature. In combination with on-going experimental determinations of equilibrium Fe isotope fractionation factors, the data for BIF minerals place additional constraints on the equilibrium Fe isotope fractionation factors for the system Fe(III)–Fe(II)–hematite–magnetite–Fe carbonate. δ⁵⁶Fe values for pyrite are the lowest yet measured for natural minerals, and stand in marked contrast to the high δ⁵⁶Fe values that are predicted from spectroscopic data. Some samples contain hematite and magnetite and have positive δ⁵⁶Fe values; these seem best explained through production of high ⁵⁶Fe/⁵⁴Fe reservoirs by photosynthetic Fe oxidation. It is not yet clear if the low δ⁵⁶Fe values measured for some oxides, as well as Fe carbonates, reflect biologic processes, or inorganic precipitation from low-δ⁵⁶Fe ferrous-Fe-rich fluids. However, the present results demonstrate the great potential for Fe isotopes in tracing the geochemical cycling of Fe, and highlight the need for an extensive experimental program for determining equilibrium Fe isotope fractionation factors for minerals and fluids that are pertinent to sedimentary environments.     

Geographic prospects for large-scale African mammal wildlife conservation

This work assesses current geographic prospects for large-scale conservation of Africa’s mammals on the basis of statistics on wildlife habitat, elephant numbers, political stability and potential for environmental tourism and concludes that these prospects depend on events in a small number of eastern and southern African (core) countries, geographically grouped into a ‘safari-belt’ between South-Africa and Kenya. Additional countries with good potential are connected to this belt. African countries need more global scientific support for their conservation efforts, particularly with respect to ongoing trans-boundary conservation efforts.     

Empirical NLTE analyses of solar spectral lines

A method is suggested for empirical NLTE analyses of solar spectral lines. Special depthdependent departure coefficients (x) are introduced and the formulas are given for further application. From test calculations it is shown that the separation of the departure coefficients for the upper and the lower level from each other and from the uncertainties in several input parameters (oscillator strength times abundance, turbulent velocities and damping constant) is greatly facilitated when spectral lines are analysed on the disk, around the limb, as well as in the flash spectrum. Therefore it is necesssary that all accessible line data are used, from accurate line profiles to equivalent widths or integrated intensities. To reduce the number of independent variables the analysis should include many multiplets between a few spectroscopic terms.We discuss the advantages of translating the departure coefficients into a set of temperatures. Some published LTE and NLTE analyses are compared in terms of these temperatures. The results do not show inexplicable contradictions. For several atomic spectra the departures from LTE seem large enough to be established quantitatively by the detailed method suggested in this paper.     

Isotope mixing models require individual isotopic tracer content for correct quantification of sediment source contributions

The use of isotopic tracers for sediment source apportionment is gaining interest with recent introduction of compound‐specific stable isotope tracers. The method relies on linear mixing of source isotopic tracers, and deconvolution of a sediment mixture initially quantifies the contribution of sources to the mixture's tracer signature. Therefore, a correction to obtain real sediment source proportions is subsequently required. As far as we are aware, all published studies to date have used total isotopic tracer content or a proxy (e.g., soil carbon content) for this post‐unmixing correction. However, as the relationship between the isotopic tracer mixture and the source mixture is different for each isotopic tracer, post‐unmixing corrections cannot be carried out with one single factor. This contribution presents an isotopic tracer model structure—the concentration‐dependent isotope mixing model (CD‐IMM)—to overcome this limitation. Herein, we aim to clarify why the “conventional” approach to converting isotopic tracer proportions to source proportions using a single factor is wrong. In an initial mathematical assessment, error incurred by not using CD‐IMM (NCD‐IMM) in unmixing two sources with two isotopic tracers showed a complex relation as a function of relative tracer contents. Next, three artificial mixtures with different proportions of three soil sources were prepared and deconvoluted using ¹³C of fatty acids using CD‐IMM and NCD‐IMM. Using NCD‐IMM affected both accuracy (mean average error increased up to a threefold compared with the CD‐IMM output) and precision (interquartile range was up to 2.5 times larger). Finally, as an illustrative example, the proportional source contribution reported in a published study was recalculated using CD‐IMM. This resulted in changes in estimated source proportions and associated uncertainties. Content of isotopic tracers is seldom reported in published work concerning use of isotopic tracers for sediment source partitioning. The magnitude of errors made by miscalculation in former studies is therefore difficult to assess. With this contribution, we hope the community will acknowledge the limitations of prior approaches and use a CD‐IMM in future studies.     

Using hourly measurements to explore the role of secondary inorganic aerosol in PM2.5 during haze and fog in Hangzhou,China

This paper explores the role of the secondary inorganic aerosol （SIA） species ammonium,NH4＋,nitrate,NO3-,and sulfate,SO24-,during haze and fog events using hourly mass concentrations of PM2.5 measured at a suburban site in Hangzhou,China.A total of 546 samples were collected between 1 April and 8 May 2012.The samples were analyzed and classified as clear,haze or fog depending on visibility and relative humidity （RH）.The contribution of SIA species to PM2.5 mass increased to ～50％ during haze and fog.The mass contribution of nitrate to PM2.5 increased from 11％ during clear to 20％ during haze episodes.Nitrate mass exceeded sulfate mass during haze,while near equal concentrations were observed during fog episodes.The role of RH on the correlation between concentrations of SIA and visibility was examined,with optimal correlation at 60％-70％ RH.The total acidity during clear,haze and fog periods was 42.38,48.38 and 45.51 nmol m-3,respectively,indicating that sulfate,nitrate and chloride were not neutralized by ammonium during any period.The nitrate to sulfate molar ratio,as a function of the ammonium to sulfate molar ratio,indicated that nitrate formation during fog started at a higher ammonium to sulfate molar ratio compared to clear and haze periods.During haze and fog,the nitrate oxidation ratio increased by a factor of 1.6-1.7,while the sulfur oxidation ratio increased by a factor of 1.2-1.5,indicating that both gaseous NO2 and SO2 were involved in the reduced visibility.