Non-destructive estimation of potato leaf chlorophyll from canopy hyperspectral reflectance using the inverted PROSAIL model

Optimizing nitrogen (N) fertilization in crop production by in-season measurements of crop N status may improve fertilizer N use efficiency. Hyperspectral measurements may be used to assess crop N status by estimating leaf chlorophyll content. This study evaluated the ability of the PROSAIL canopy-level reflectance model to predict leaf chlorophyll content. Trials were conducted with two potato cultivars under different N fertility rates (0–300 kg N ha⁻¹). Canopy reflectance, leaf area index (LAI) and leaf chlorophyll and N contents were measured. The PROSAIL model was able to predict leaf chlorophyll content with reasonable accuracy later in the growing season. The low estimation accuracy earlier in the growing season could be due to model sensitivity to non-homogenous canopy architecture and soil background interference before full canopy closure. Canopy chlorophyll content (leaf chlorophyll content × LAI) was predicted less accurately than leaf chlrophyll content due to the low estimation accuracy of LAI for values higher than 4.5.     

Evolution of metamorphic volatiles during exhumation of microdiamond-bearing granulites in the Western Gneiss Region, Norway

Fluid inclusions in garnet, kyanite and quartz from microdiamond-bearing granulites in the Western Gneiss Region, Norway, document a conspicuous fluid evolution as the rocks were exhumed following Caledonian high- and ultrahigh-pressure (HP–UHP) metamorphism. The most important of the various fluid mixtures and daughter minerals in these rocks are: (N₂ + CO₂ + magnesian calcite), (N₂ + CO₂ + CH₄ + graphite + magnesian calcite), (N₂ + CH₄), (N₂ + CH₄ + H₂O), (CO₂) and (H₂O + NaCl + CaCl₂ + nahcolite). Rutile also occurs in the N₂ + CO₂ inclusions as a product of titanium diffusion from the garnet host into the fluid inclusions. Volatiles composed of N₂ + CO₂ + magnesian calcite characterise the ambient metamorphic environment between HP–UHP (peak) and early retrograde metamorphism. During progressive decompression, the mole fraction of N₂ increased in the fluid mixtures; as amphibolite-facies conditions were reached, CH₄ and later, H₂O, appeared in the fluids, concomitant with the disappearance of CO₂ and magnesian calcite. Graphite is ubiquitous in the host lithologies and fluid inclusions. Thermodynamic modelling of the metamorphic volatiles in a graphite-buffered C-O-H system demonstrates that the observed metamorphic volatile evolution was attainable only if the f _O2 increased from c. −3.5 (±0.3) to −0.8 (±0.3) log units relative to the FMQ oxygen buffer. External introduction of oxidising aqueous solutions along a system of interconnected ductile shear zones adequately explains the dramatic increase in the f _O2. The oxidising fluids introduced during exhumation were likely derived from dehydration of oceanic crust and continental sediments previously subducted during an extended period of continental collision in conjunction with the Caledonian orogeny. Received: 15 December 1997 / Accepted: 25 May 1998     

Proximity and complexity in the emergence of high technology industry: The oxbridge comparison

This paper examines similarities and differences in the emergence of high-tech enterprise and the growth of associated industry in Cambridgeshire and Oxfordshire since the 1960s. These cases are viewed as instances of a generic phenomenon: the emergence and growth of the science-based ‘innovative milieu’. A conceptual scheme drawn from complexity studies is used to introduce explanatory coherence into the apparently scattered and disconnected factors relevant to the genesis of high-tech milieux.     

Relative stress variations as determined by b-values from earthquakes in circum-pacific subduction zones

Assuming a relation of “b” to stress state, the possibility of globe-wide stress variation and transmission was investigated. The NOAA earthquake data file served to determine the temporal change in “b” of log N = a − bM from 1963 to 1975.Periods of six to eight years are observed in the b-values (stress pattern) for most circum-Pacific areas (South America, Tonga, Kermadec, New Hebrides, Kamchatka and Eastern Aleutians).In the Kurils, fore- and aftershock sequences of large earthquakes seem to mask any characteristic global pattern that might exist. These sequences exhibit low b-values (high stress) through the time of foreshocks and early stages of aftershocks, followed by rapid increase in b-values (decrease in stress).Use of a worldwide earthquake data file clearly yields less resolution of the temporal “b” variation than the use of local network studies published by other authors.Incidental to the study, 1124 earthquakes of the NOAA data file yield the M_s − m_b relations: M_s = 1.16m_b − 0.835 for 4.5 m_b 6 and: log₁₀M_s = 0.1432m_b − 0.0629 form_b > 6 with correlative coefficients of 0.994 and 0.992 respectively.     

The rotation of Italy: Preliminary palaeomagnetic data from the Umbrian sequence,Northern Apennines

A preliminary collection of 43 palaeomagnetic samples (10 sites) from the miogeosynclinal and supposedly autochthonous Umbrian sequence in the Northern Apennines, Italy, was analysed by means of alternating magnetic fields and thermal demagnetization studies. The older group of samples, taken from the upper part of the Calcari Diasprini (Malm), the Fucoid Marls (Albian/Cenomanian) and from the basal part of the Scaglia Bianca (Early Late Cretaceous), all showed normal polarity directions and resulted in a mean site direction:D = 290.5°,I = +51.5°,α₉₅ = 11°,k = 74,N = 4.The younger group of samples, taken throughout the Scaglia Rossa sequence (Latest Cretaceous/Middle Eocene) showed normal and reversed polarity directions. In contrast to the older group, the magnetic analysis of these samples resulted in a considerably less dense grouping of site mean directions. This presumably is due to inaccuracies introduced with the very large bedding tilt corrections that had to be applied to the samples of some sites. A tentative mean site direction for these Scaglia Rossa samples was computed as:D = 351°,I = +52.5°,α₉₅ = 23.5°,k = 11.5,N = 5.Despite the low precision of the Scaglia Rossa result, the significant deviation between this Latest Cretaceous/Early Tertiary direction and the Late Jurassic/Early Late Cretaceous direction indicates a counterclockwise rotation of more than forty degrees. This rotation can be dated as Late Cretaceous.How far these data from the Northern Apennines apply to other parts of the Italian Peninsula has yet to be established. The timing of this rotation is not at variance with the data from other parts of Mediterranean Europe (Southern Alps, Iberian Peninsula) and from Africa. However, taking into account the preliminary nature of the results, the amount of rotation of the Northern Apennines seems to surpass the rotation angle which is deduced from the palaeomagnetic data for Africa.     

Aragonite dissolution on the Bermuda pedestal: Its depth and geochemical significance

The depth distribution of pteropod and planktonic foram tests, and fine-grained (<62 μm) aragonite, high-Mg calcite (12 mode mol.% MgCO₃), and low-Mg calcite has been determined for surface sediments of an area of the eastern slope of the Bermuda pedestal. Over the range 1800–3000 m, fine-grained aragonite and fine-grained high-Mg calcite gradually disappear relative to fine-grained low-Mg calcite, and pteropods gradually disappear relative to planktonic forams. This is interpreted as preferential dissolution of aragonite (and high-Mg calcite) relative to low-Mg calcite over this depth range. Coarse aragonitic debris derived from shallow-water organisms living on the Bermuda platform does not show consistent disappearance over the same depth zone. Chemical analyses of bottom water samples taken at the same time as some of the sediment samples indicate that the degree of saturation with respect to aragonite Ω_A over the zone of aragonite disappearance ranges from 0.55 to 0.85; i.e. major dissolution occurs only at Ω_A values distinctly less than one. These results lend credence to the hypothesis that CaCO₃ dissolution in the oceans, both as aragonite and as calcite, takes place mainly as a response to complex chemical kinetic phenomena and not as a result of the simple attainment of undersaturation (thermodynamic hypothesis) or the resuspension of bottom sediment (hydrodynamic hypothesis).     

Assessment of δ13C and C/N ratios in bulk organic matter as palaeosalinity indicators in Holocene and Lateglacial isolation basin sediments,northwest Scotland

Carbon isotopes (δ¹³C) and C/N ratios from bulk organic matter have recently been used as alternative proxies for relative sea‐level (RSL) reconstruction where there are problems associated with conventional biological indictors. A previous study on a single isolation basin (Upper Loch nan Eala) in northwest Scotland has shown a clear relationship between δ¹³C, C/N ratios and palaeosalinity from Younger Dryas and Holocene aged sediments. In this paper we present results of δ¹³C and C/N ratio analyses from other isolation basins in northwest Scotland over the Holocene and the Lateglacial period in order to validate this technique. The results from the Holocene sequences support the earlier findings that this technique can be used to identify RSL change from isolation basins over the Holocene in this region. The relationship between δ¹³C, C/N ratios and RSL change is not apparent in sediments of Lateglacial age. Other environmental variables such as atmospheric CO₂ concentration, poor vegetation development and temperature influence δ¹³C values during this period. Copyright © 2007 John Wiley & Sons, Ltd.     

Volcanic ash clouds affecting Northern Europe: the long view

The volcanic ash or ‘tephra’ cloud resulting from the relatively small (volume and VEI) eruption of the Icelandic volcano Eyjafjallajökull in 2010 caused major air travel disruption, at substantial global economic cost. On several occasions in the past few centuries, Icelandic eruptions have created ash and/or sulphur dioxide clouds which were detected over Europe (e.g. Hekla in 1947, Askja in 1875, and Laki in 1783). However, these historical observations do not represent a complete record of events serious enough to disrupt aviation in Europe. The only feasible evidence for this is within the geological tephra record. Ash layers are preserved in bogs and lakes where tephra deposited from the atmosphere is incorporated in the peat/mud. In this article we: 1, introduce the analysis of the Northern European sedimentary tephra record; 2, discuss our findings and modelling results; 3, highlight how these were misinterpreted by the popular media; and 4, use this experience to outline several existing problems with current tephra studies and suggest agendas for future research.     

Perimagmatische und apomagmatische Lagerstätten

Ohne Zusammenfassung