Sensitivity of FORGRO to climatic change scenarios: A case study on Betula pubescens, Fagus sylvatica and Quercus robur in The Netherlands

The impacts of the climate change predictions of four general circulation models (GFDL, GISS, OSU and UKMO) on net primary production (NPP) ofBetula pubescens, Fagus sylvatica and Quercus robur in The Netherlands were analysed using the process-based model FORGRO. FORGRO is a model suitable to simulate growth of managed mono-species stands. For the GCMs mentioned, both transient and equilibrium 2 × CO₂ scenarios of temperature and precipitation change were evaluated and compared with responses under current climate. It was found that the NPP increases in the transient scenarios, but remains the same or declines in the 2 × CO₂ scenarios. This is because respiration increases more with rising temperature than photosynthesis. During the transient scenarios this effect gradually increases, while in the 2 × CO₂ scenario this effect is operating over the entire simulation period.If water limitation is taken into account, then the NPP of the reference scenario is reduced. In both the transient and 2 × CO₂ scenarios mis water limitation is annulated, resulting in a stronger response of NPP compared to the situation without water limitation. This enhancement of the response is most pronounced in the transient scenario due to the gradual effect of temperature on respiration.Similar results were obtained with a version of FORGRO in which the photosynthesis module of HYBRID (PGEN) is incorporated, although the response in FORGRO-PGEN is usually higher than that of FORGRO. This is because the response of photosynthesis to CO₂ rises with increasing temperature as defined in the PGEN-model, but not according to FORGRO.     

Thermal evolution of the mantle underneath the Mid-German crystalline rise: Evidence from mantle xenoliths from the Rhön area (Central Germany)

Summary A suite of ultramafic xenoliths (spinel peridotites, one olivine-clinopyroxene hornblendite, and one spinel pyroxenite) from Tertiary basalt vents and lava flows of the Rhön area (Central Germany) were investigated petrologically and geochemically. With regard to P-T estimates two distinct groups of peridotite xenoliths can be discriminated: (I) A low- to intermediate-temperature group of spinel lherzolites and wehrlites mainly displaying coarse equant textures yielded temperature estimates in the range of 840–1050 °C at rather variable pressures of 11–24 kbar. The strong variability of the P-T estimates is attributed to mineral chemical disequilibria and different diffusion rates of the elements used for geothermometry and geobarometry. Spinel-pyroxene symplectites within part of these xenoliths point to a former position in the stability field of garnet lherzolite. These xenoliths are variably depleted in the basaltic component by partial melt extraction. They often show an enrichment in LREE and MREE which is due to a later overprinting by cryptic metasomatism. (II) A high-temperature group of xenoliths, which mainly consists of porphyroclastic and subordinate coarse equant spinel lherzolites and harzburgites, experienced temperatures of 1190–1270 °C at 19–26 kbar. The P-T values for these xenoliths fall close to a geothermal gradient of about 90 mW/m² and illustrate intense heating processes in the mantle which were often coupled with ductile deformation caused by lithospheric stretching. The thermal disturbance which led to the reequilibration of these peridotites must have occurred during the Tertiary magmatic event as indicated by the absence of retrograde mineral zoning, missing textural reequilibration, and the presence of partial melting phenomena in clinopyroxene. Unlike sheared xenoliths from other locations, the porphyroclastic high-temperature peridotites from the Rhön are depleted in basaltic component, in HREE, Y, and Sc. An olivine-clinopyroxene hornblendite is classified as some kind of basaltic cumulate which - according to its P-T estimate of about 1150 °C at 9 kbar - originates from hte transition zone between the lower crust and the upper mantle.⁴⁰Ar-³⁹Ar dating of kaersutite from this sample indicates an age of about 25 Ma which is in accordance with the beginning of Tertiary volcanism in the Rhön area. These investigations show that part of the lithospheric mantle underneath the Rhön area experienced a thermal reequilibration during the Tertiary magmatic event while other parts give evidence of an older history, i.e. a cryptic metasomatism and a transition from the garnet- to the spinel-lherzolite field. A possible geotectonic scenario for the transition could be the post-Variscan crustal reequilibration.

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Thermische Entwicklung des Mantels unter der Mitteldeutschen Kristallinschwelle abgeleitet aus Mantelxenolithen der Rhön

Zusammenfassung Eine Reihe von ultramafischen Xenolithen (Spinell-Peridotite, ein Olivin-KlinopyroxenHornblendit und ein Spinell-Pyroxenit) aus tertiären Basalten der Rhön wurde petrologisch and geochemisch untersucht. Zwei Gruppen von Peridotiten können hinsichtlich ihrer Äquilibrierungstemperaturen unterschieden werden: (I) Spinell-Lherzolithe and -Wehrlite mit niedrigen und mittleren Temperaturen von 840–1050 °C bei Drucken von 11-24 kbar zeigen zumeist granulare Gefüge. Die große Schwankungsbreite dieser P-T-Abschätzungen ist durch mineralchemische Ungleichgewichte und unterschiedliche Schließungstemperaturen der Geothermometer und Geobarometer bedingt. Spinell-Pyroxen-Symplektite, die in einigen dieser Xenolithe auftreten, weisen auf eine vormalige Position im Stabilitätsfeld von GranatLherzolith hin. Diese Xenolithe sind durch partielle Schmelzextraktion unterschiedlich stark depletiert. Häufig zeigen she eine Anreicherung der leichten and mittleren Seltenerdelemente, was durch eine spätere kryptometasomatische Überprägung bedingt ist. (II) Eine Gruppe hochtemperierter, vorwiegend porphyroklastischer und untergeordnet granularer Spinell-Lherzolithe und -Harzburgite wurde unter Temperaturen von 1190–1270 °C bei Drucken von 19–26 kbar überprägt. Die P-T Werte für diese Xenolithe liegen auf einem geothermischen Gradienten von über 90 mW/m², was auf intensive Aufheizprozesse im Mantel hinweist. Oftmals wurde these Aufheizung von einer duktilen Deformation begleitet, deren Ursache eine Dehnung der Mantellithosphäre war. Aufgrund der fehlenden Gleichgewichtstexturen, der Abwesenheit von retrograden Mineralzonierungen und partieller Schmelzprozesse bei den Klinopyroxenen dieser Xenolithe müssen ihre Deformation and Hochtemperaturüberprägung während des tertiären Magmatismus stattgefunden haben. Die porphyroklastischen, hochtemperierten Xenolithe zeigen die stärkste Abreicherung an basaltischer Komponente, den schweren Seltenerdelementen sowie an Y and Sc. Bei dem Olivin-Klinopyroxen-Hornblendit handelt es sich um ein basaltisches Kumulat, welches aufgrund seiner P-T Abschätzung (um 1150 °C bei 9 kbar) aus dem Übergangsbereich von unterer Kruste zu oberem Mantel stammt. Eine⁴⁰Ar-³⁹Ar Datierung von Kaersutiten dieser Probe weist auf ein Alter von etwa 25 Ma, was in Übereinstimmung mit dem Beginn des tertiären Vulkanismus in dieser Region ist. Diese Untersuchungen verdeutlichen, daß ein Teil des lithosphärischen Mantels unter der Rhön eine thermische Äquilibrierung während des tertiären magmatischen Ereignisses erfuhr. Dagegen zeigen andere Teile noch Relikte einer älteren Geschichte, speziell eine kryptische Metasomatose and den Übergang vom Stabilitätsfeld des Granat-Lherzoliths zum Spinell-Lherzolith. Ein mögliches geotektonisches Szenario für diesen Transfer könnte die postvariscische Krustenreäquilibrierung sein.

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With 7 Figures     

Phanerozoic magmatic activity in the northwestern part of the Trans-European Suture Zone

Summary Indicators of magmatism in the northwestern part of the Trans-European Suture Zone are outlined. The igneous rocks are predominantly mafic and of mantle origin. The changing character of the magma geochemistry of the Permosilesian volcanic series (rhyolitic-andesitic and MORB-type/continental tholeiites), via Uckermark and Rügen to Skåne, is consistent with the changing crustal thickness along the border of Baltica. Some features of Early Palaeozoic volcaniclastic sediments hint at Early Palaeozoic oceanic development (ophiolite association ?) in a suture zone, whereas the Permo-Carboniferous to Eocene volcanic associations are related to rift structures and deep-seated structural elements within the Tornquist-Teisseyre Zone (TTZ).     

Observed mid-to-high latitude interchange of atmospheric angular momentum and some implications

The global distribution of atmospheric angular momentum (M) during 1977–1978 and 1982–1983 is examined to identify evidence of prominent short term interchanges of relative atmospheric momentum between mid and high latitude zones, in both hemispheres. Thirty day detrended angular momentum time series, prepared from the NMC gridded zonal wind data are examined in latitude bands. These data exhibit obvious quasi-coherent oscillations with periods near 30 days plus variations with shorter periods. An examination of latitude/altitude cross sections of zonal winds reveals that the oscillations are present almost simultaneously at all altitude levels between 1000 and 50 mb. Cross latitude teleconnections, evident as strong anticorrelated signatures between adjacent latitude bands are observed in the midlatitudes of both hemispheres. Comparison of these signatures with the time integrated flux of angular momentum across the nodal interface confirms that direct eddy transport of momentum is occurring. Transport of momentum from the mid latitude bands results in an increase in the momentum of the higher latitude bands and vice versa. Transport of planetary angular momentum by a Hadley/Ferrel type meridional circulation is specifically ruled out although that process may contribute to seasonal and longer term modulations. The short term oscillations in M can reach magnitudes which dominate the global variation in momentum, as noted in the recent 1982–83 El Niño episode in which the January 1983 momentum peaked at a decadal high. Similar El-Niño like changes in the trans-latitude momentum redistribution are observed in the Southern Hemisphere winters, following the Northern Hemisphere episode. Overall, our results confirm and describe in more detail the long recognized fact that momentum can be selectively redistributed between tropical, temperate, and high latitudes, in patterns indicative of the development and dissipation of interacting regions, described variously in studies of the index cycle, seesaws and teleconnections. In emphasizing the large scale coordination of these interchanges, and moreover their occasional very short time scales, these results will hopefully stimulate studies relating atmospheric behavior in distant regions thereby contributing to improvements in forecasting the circulation process.     

Apparent copper complexation capacity and conditional stability constants in north atlantic waters

Surface water samples were collected in the north Atlantic Ocean in July–August 1983. Their apparent complexation capacity for copper (CC_Cu) was determined on board, using differential pulse anodic stripping voltammetry under clean room conditions. Measurements were carried out by direct titrations as well as after equilibration of copper spikes. CC_Cu and conditional stability constants (K′) were calculated, by means of three different methods, which are compared.On the basis of salinity, temperature, silicate and phosphate concentrations the following surface waters could be distinguished: North Atlantic Drift (I), East Greenland Current (II), Labrador Current (III) and Gulf Stream waters (IV, V). CC_Cu and K′ were found to differ between these waters. The range of values for CC_Cu and their mean values given in parentheses, as calculated from van den Berg plots for waters I–IV are: I, 53–65 (59); II, 47–66 (55); III, 37–53 (45); IV, 20–42 (33) nM Cu. The range and mean values for log K′ are: I, 8.23–8.33 (8.28); II, 7.89–8.11 (7.98); III, 8.40–8.41 (8.41); IV, 7.90–8.21 (8.06).Information on complexation kinetics extracted from the titration curve revealed that k_f^′ is area-specific. The complexation rate constant in the northern part (Area I) is about two times larger than that in the southern area IV, (3.6 ± 0.3) and (2.2 ± 0.2) × 10⁴s⁻¹M⁻¹ Cu, respectively.Preliminary results for deep water samples suggest smaller but still existent CC_Cu and higher K′ than those found for surface waters.     

Characterization of multiple functional groups on kaolinite

Multiple proton functional group conditional binding constants (K′_i) and their concentrations (C_i) are determined from detailed acid/base titration data. The C-K′ information is obtained for kaolinite by assuming that the distribution can be approximated by cumulative independent mono protic groups. Linear programming optimization techniques are used to Fit the data. In addition, the electrode calibration is optimized in the data fit. This adjustment is important for high and low pHs. Discrete concentration dependent pXs of about 3.4, 4.5, 6.7 and 9.8 are determined for a reference kaolinite. These correspond reasonably well to designations made by Wehrli et al. (1990, Aquatic Sciences, Vol. 52, pp. 1–31 ) to A10H2 and AlOH proton reactions at edge and surface sites and to silanol exchange. There is an ionic strength effect for one site. Long and short reaction times and reversibility affect the results.     

羊啃食动力学模拟与内蒙古西部气候变化适应

将定性分析、民主参与式评估和定量数值模拟方法结合起来,对阿拉善气候变化适应问题进行了简要评估并重点分析了土地退化、放牧和草原管理策略之间的关系。阿拉善主要的适应政策是禁牧和生态移民。禁牧后荒漠草原植被得到恢复,但移民增加了绿洲压力,过度开垦又造成周边土地沙化;过度抽取地下水致使水位下降并伴随咸水入侵和地表盐碱化。禁牧的另一个副作用是造成草原鼠害加重及火灾风险增加,生物多样性也呈现先升后降趋势。一些灌木因缺乏啃食出现退化迹象等,说明一定程度的啃食有利于维持草原生态平衡。因此,动物是草原生态系统不可或缺的成员之一。我们用一个包含动物啃食等的森林生态动力模式模拟了啃食动力学,结果表明,有限的放牧有利于草场更新并能充分利用草原资源;过度放牧导致草场退化并伴随羊群死亡。因此,需要将圈养和限制性放牧结合起来,制定可持续性适应政策。     

Effects of a fully submerged boulder within a boulder array on the mean and turbulent flow fields: Implications to bedload transport

The objective of this coupled experimental and numerical study is to provide insight into the mean and turbulent flow fields within an array of fully submerged, isolated, immobile boulders. Our study showed that the velocity defect law performed well for describing the mean flow around the boulder within the array. A prerequisite, however, was to accurately estimate the spatial variability of u* around the boulder, which was achieved via the boundary characteristics method. The u* exhibited considerable spatial variability within the array and form roughness was shown to be up to 2 times larger than the skin roughness in the boulder near-wake region. Because the boulders bear a significant amount of the flow shear, the available bed shear stress for entrainment of the mobile sediment, ?? _ols , near the boulders was roughly 50% lower than the ambient ?? _ols . The ?? _ols variability induced by the boulders could lead to a threefold overestimation of the sediment transport rate.     

First health and pollution study on harbor seals (Phoca vitulina) living in the German Elbe estuary

The Elbe is one of the major rivers releasing pollutants into the coastal areas of the German North Sea. Its estuary represents the habitat of a small population of harbor seals (Phoca vitulina). Only little is known about the health status and contamination levels of these seals. Therefore, a first-ever seal catch was organized next to the islands of Neuwerk and Scharhörn in the region of the Hamburg Wadden Sea National Park. The investigations included a broad set of health parameters and the analysis of metals and organic pollutants in blood samples. Compared to animals of other Wadden Sea areas, the seals showed higher γ-globulin levels, suggesting higher concentrations of pathogens in this near-urban area, elevated concentrations for several metals in particular for V, Sn, Pb, and Sr, and comparable ranges for chlorinated organic contaminants, except for elevated levels of hexachlorobenzene, which indicates characteristic inputs from the Elbe.     

Quantitative relationship between water-depth and sub-fossil ostracod assemblages in Lake Donggi Cona,Qinghai Province,China

A calibration data set of 51 surface sediment samples from Lake Donggi Cona on the northeastern Tibetan Plateau was investigated to study the relationship between sub-fossil ostracod assemblages and water depth. Samples were collected over a depth range from 0.6 to 80 m. A total of 16 ostracod species was identified from the lake with about half of the species restricted to the Tibetan Plateau and its adjacent mountain ranges and poorly known in terms of ecological preferences, and the other half displaying a mainly Holarctic distribution. Living macrophytes and macroalgae were recorded in Lake Donggi Cona down to a depth of about 30 m, and bivalve (Pisidium cf. zugmayeri) and gastropod (Gyraulus, Radix) shells were found down to depths of 43 and 48 m, respectively. The ostracod-water-depth relationship was assessed by multivariate statistical analysis and ostracod-based transfer functions for water depth were constructed. Weighted averaging partial least squares (WA-PLS) regression provided the best model with a coefficient of determination r ² of 0.91 between measured and ostracod-inferred water depth, a root mean square error of prediction of 8% and a maximum bias of 10.6% of the gradient length, as assessed by leave-one-out cross-validation. Our results show the potential of ostracods as palaeo-depth indicators in appropriate settings. However, transfer-function applications using fossil ostracod assemblages for palaeo-depth estimations require a thorough understanding of the palaeolimnological conditions of lakes and therefore detailed multi-proxy analysis to avoid misinterpretation of ostracod-based inferences.