Biodiversity Conservation in the REDD   总被引：1，自引：0，他引：1  

Gary D Paoli  Philip L Wells  Erik Meijaard  Matthew J Struebig  Andrew J Marshall  Krystof Obidzinski  Aseng Tan  Andjar Rafiastanto  Betsy Yaap  JW Ferry Slik  Alexandra Morel  Balu Perumal  Niels Wielaard  Simon Husson  Laura D'Arcy 《Carbon balance and management》2010,5(1):1-9

Background

Forests occur across diverse biomes, each of which shows a specific composition of plant communities associated with the particular climate regimes. Predicted future climate change will have impacts on the vulnerability and productivity of forests; in some regions higher temperatures will extend the growing season and thus improve forest productivity, while changed annual precipitation patterns may show disadvantageous effects in areas, where water availability is restricted. While adaptation of forests to predicted future climate scenarios has been intensively studied, less attention was paid to mitigation strategies such as the introduction of tree species well adapted to changing environmental conditions.

Results

We simulated the development of managed forest ecosystems in Germany for the time period between 2000 and 2100 under different forest management regimes and climate change scenarios. The management regimes reflect different rotation periods, harvesting intensities and species selection for reforestations. The climate change scenarios were taken from the IPCC's Special Report on Emission Scenarios (SRES). We used the scenarios A1B (rapid and successful economic development) and B1 (high level of environmental and social consciousness combined with a globally coherent approach to a more sustainable development). Our results indicate that the effects of different climate change scenarios on the future productivity and species composition of German forests are minor compared to the effects of forest management.

Conclusions

The inherent natural adaptive capacity of forest ecosystems to changing environmental conditions is limited by the long life time of trees. Planting of adapted species and forest management will reduce the impact of predicted future climate change on forests.  相似文献   

“Convoluted Journeys”: Integrating Nonprofit Organizations and University Science     

Vanessa Crossgrove Fry  Jen Schneider  Sally Sargeant-Hu  Carl Anderson  Erik Olson 《社会与自然资源》2019,32(3):239-254

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Changes in physical properties of a reservoir sandstone as a function of burial depth – The Etive Formation,northern North Sea     

Øyvind Marcussen  Tom Erik MaastNazmul H. Mondol  Jens JahrenKnut Bjørlykke 《Marine and Petroleum Geology》2010

Rock physical properties, like velocity and bulk density, change as a response to compaction processes in sedimentary basins. In this study it is shown that the velocity and density in a well defined lithology, the shallow marine Etive Formation from the northern North Sea increase with depth as a function of mechanical compaction and quartz cementation. Physical properties from well logs combined with experimental compaction and petrographic analysis of core samples shows that mechanical compaction is the dominant process at shallow depth while quartz cementation dominates as temperatures are increased during burial. At shallow depths (<2000–2500 m, 70–80 °C) the log derived velocities and densities show good agreement with results from experimental compaction of loose Etive sand indicating that effective stress control compaction at these depths/temperatures. This indicates that results from experimental compaction can be used to predict reservoir properties at burial depths corresponding to mechanical compaction. A break in the velocity/depth gradient from about 2000 m correlates with the onset of incipient quartz cementation observed from petrographic data. The gradient change is caused by a rapid grain framework stiffening due to only small amounts of quartz cement at grain contacts. At temperatures higher than 70–80 °C (2000–2500 m) the velocities show a strong correlation with quartz cement amounts. Porosity reduction continues after the onset of quartz cementation showing that sandstone diagenesis is insensitive to effective stress at temperatures higher than 70–80 °C. The quartz cement is mainly sourced from dissolution at stylolites reflected by the fact that no general decrease in intergranular volume (IGV) is observed with increasing burial depth. The IGV at the end of mechanical compaction will be important for the subsequent diagenetic development. This study demonstrates that mechanical compaction and quartz cementation is fundamentally different and this needs to be taken into consideration when analyzing a potential reservoir sandstone such as the Etive Formation.  相似文献   

Food partitioning of leaf-eating mangrove crabs (Sesarminae): Experimental and stable isotope (C and N) evidence     

Ditte K. Kristensen  Erik Kristensen  Perrine Mangion 《Estuarine, Coastal and Shelf Science》2010

The feasibility of mangrove leaves as a full diet for sesarmid crabs has been questioned for decades. Since these leaves are nitrogen-poor, sesarmids probably obtain nitrogen from other sources to sustain growth. The aim of this study was to assess the food partitioning of the sesarmid species Neoepisesarma versicolor with emphasis on nitrogen allocation. The preference for animal tissue when crabs were pre-fed diets of different nitrogen content was determined in the laboratory. Furthermore, the possible in situ diet composition of N. versicolor was established from carbon and nitrogen stable isotope signature (δ¹³C and δ¹⁵N) of freshly caught individuals and their potential food sources, using a concentration-dependent mixing model. N. versicolor showed significantly higher feeding preferences for fish meat when pre-fed leaf material without than with access to meat, indicating that this crab species can meet its nitrogen demand by ingesting animal tissue. The stable isotope mixing model based on in situ materials suggests that the diet of N. versicolor consists of ∼60% leaves in terms of biomass, leaving ∼40% for other sources such as animal tissue and benthic microorganisms. The biomass contribution from animal tissues, in form of e.g. other crustaceans and fish carcasses, was found to account for ∼15%. Despite the relative low biomass fraction, animal food sources may contribute with up to half of the nitrogen in the diet of N. versicolor. The quantity of ingested sediment most likely exceeds that of animal tissues. However, due to the low concentration of assimilable microalgae and other microorganism, we propose that sediment associated sources are less important as a nitrogen source for N. versicolor than hitherto presumed.  相似文献   

On the small-scale fractal geometrical structure of a living coral reef barrier     

Damien Sous  Frédéric Bouchette  Erik Doerflinger  Samuel Meulé  Raphael Certain  Gwladys Toulemonde  Benjamin Dubarbier  Bernard Salvat 《地球表面变化过程与地形》2020,45(12):3042-3054

The topographical complexity of coral reefs is of primary importance for a number of hydrodynamical and ecological processes. The present study is based on a series of high-resolution seabottom elevation measurements along the Maupiti Barrier Reef, French Polynesia. Several statistical metrics and spectral analysis are used to characterize the spatial evolution of the coral geometrical structure from the reef crest to the backreef. A consistent fractal-like power law exists in the spectral density of bottom elevation for length scales between 0.1 and 7 m, while at larger scale, the reef structure shows a different pattern. Such a fine characterization of the reef geometrical structure provides key elements to reconstruct the reef history, to improve the representation of reef roughness in hydrodynamical models and to monitor the evolution of coral reef systems in the context of global change. © 2020 John Wiley & Sons, Ltd.  相似文献   

A GCSS Boundary-Layer Cloud Model Intercomparison Study Of The First Astex Lagrangian Experiment     

Christopher S. Bretherton  Steven K. Krueger  Matthew C. Wyant  Peter Bechtold  Erik Van Meijgaard  Bjorn Stevens  Joao Teixeira 《Boundary-Layer Meteorology》1999,93(3):341-380

Three single-column models (all with an explicit liquid water budget and compara-tively high vertical resolution) and three two-dimensional eddy-resolving models (including one with bin-resolved microphysics) are compared with observations from the first ASTEX Lagrangian experiment. This intercomparison was a part of the second GCSS boundary-layer cloud modelling workshop in August 1995.In the air column tracked during the first ASTEX Lagrangian experiment, a shallow subtropical drizzling stratocumulus-capped marine boundary layer deepens after two days into a cumulus capped boundary layer with patchy stratocumulus. The models are forced with time varying boundary conditions at the sea-surface and the capping inversion to simulate the changing environment of the air column.The models all predict the observed deepening and decoupling of the boundary layer quite well, with cumulus cloud evolution and thinning of the overlying stratocumulus. Thus these models all appear capable of predicting transitions between cloud and boundary-layer types with some skill. The models also produce realistic drizzle rates, but there are substantial quantitative differences in the cloud cover and liquid water path between models. The differences between the eddy-resolving model results are nearly as large as between the single column model results. The eddy resolving models give a more detailed picture of the boundary-layer evolution than the single-column models, but are still sensitive to the choice of microphysical and radiative parameterizations, sub-grid-scale turbulence models, and probably model resolution and dimensionality. One important example of the differences seen in these parameterizations is the absorption of solar radiation in a specified cloud layer, which varied by a factor of four between the model radiation parameterizations.  相似文献   

Stability and Grid Dispersion of the P-SV 4th-Order Staggered-Grid Finite-Difference Schemes     

Moczo  Peter  Kristek  Jozef  Bystrický  Erik 《Studia Geophysica et Geodaetica》2000,44(3):381-402

Stability and grid dispersion in the P-SV 4th-order in space, 2nd-order in time, displacement-stress staggered-grid finite-difference scheme is investigated in the case of a homogeneous unbounded medium. All results, however, also apply to the velocity-stress and displacement- velocity-stress finite-difference schemes. Independent stability conditions for the P and S waves are obtained by exact separation of equations for the two types of waves. Since the S-wave group velocity can differ from the actual velocity as much as 5% for the sampling ratio 1/5, commonly used in numerical modelling, the sampling of the minimum S wavelength by 6 grid spacings (with the velocity difference not larger than 2.5%) is recommended. Grid dispersion is strongest for a wave propagating in a direction of a coordinate axis and weakest for a wave propagating along a plane diagonal. Grid dispersion in the 4 ^th -order scheme for the sampling ratios s = 1/5 and s = 1/6 is smaller than grid dispersion in the 2 ^nd -order scheme for s = 1/10 and s = 1/12, respectively.  相似文献   

Peter William Francis     

Erik W. Klemetti  Anita L. Grunder 《Bulletin of Volcanology》2000,62(2):143-145

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Magmatic processes revealed by textural and compositional trends in Merapi dome lavas     

J. E. Hammer  K. V. Cashman  B. Voight 《Journal of Volcanology and Geothermal Research》2000,100(1-4)

Syn-eruptive degassing of volcanoes may lead to syn-eruptive crystallization of groundmass phases. We have investigated this process using textural and compositional analysis of dome material from Merapi volcano, Central Java, Indonesia. Samples included dome lavas from the 1986–88, 1992–93, 1994 and 1995 effusive periods as well as pyroclastic material deposited by the November 1994 dome collapse. With total crystallinities commonly in excess of 70% (phenocrysts+microlites), the liquids present in Merapi andesites are highly evolved (rhyolitic) at the time of eruption. Feldspar microlites in dome rocks consist of plagioclase cores (Ab₆₃An₂₉Or₈) surrounded by alkali feldspar rims (Ab₅₃An₅Or₄₂), compositional pairs which are not in equilibrium. A change in the phase relations of the ternary feldspar system caused by degassing best explains the observed transition in feldspar composition. A small proportion of highly vesicular airfall tephra grains from the 1994 collapse have less evolved glass compositions than typical dome material and contain rimless plagioclase microlites, suggesting that the 1994 collapse event incorporated less-degassed, partially liquid magma in addition to fully solidified dome rock.As decompression drives volatile exsolution, rates of degassing and resultant microlite crystallization may be governed by magma ascent rate. Microlite crystallinity is nearly identical among the 1995 dome samples, an indication that similar microlite growth conditions (P_H2O and temperature) were achieved throughout this extrusive period. However, microlite number density varied by more than a factor of four in these samples, and generally increased with distance from the vent. Low vent-ward microlite number densities and greater microlite concentrations down-flow probably reflect progressively decreasing rates of undercooling at the time of crystal nucleation during extrusion of the 1995 dome. Comparison between dome extrusion episodes indicates a correlation between lava effusion rate and microlite number density, suggesting that extrusion slowed during 1995. Crystal textures and compositions in the 1992–93 and 1994 domes share the range exhibited by the 1995 dome, suggesting that transitions in crystallization conditions (i.e., rates of undercooling determined by effusion rate) are cyclic.  相似文献   

Mixed Integer-Real Valued Adjustment (IRA) Problems: GPS Initial Cycle Ambiguity Resolution by Means of the LLL Algorithm   总被引：4，自引：0，他引：4  

Erik W. Grafarend 《GPS Solutions》2000,4(2):31-44

In order to achieve to GPS solutions of first-order accuracy and integrity, carrier phase observations as well as pseudorange observations have to be adjusted with respect to a linear/linearized model. Here the problem of mixed integer-real valued parameter adjustment (IRA) is met. Indeed, integer cycle ambiguity unknowns have to be estimated and tested. At first we review the three concepts to deal with IRA: (i) DDD or triple difference observations are produced by a properly chosen difference operator and choice of basis, namely being free of integer-valued unknowns (ii) The real-valued unknown parameters are eliminated by a Gauss elimination step while the remaining integer-valued unknown parameters (initial cycle ambiguities) are determined by Quadratic Programming and (iii) a RA substitute model is firstly implemented (real-valued estimates of initial cycle ambiguities) and secondly a minimum distance map is designed which operates on the real-valued approximation of integers with respect to the integer data in a lattice. This is the place where the integer Gram-Schmidt orthogonalization by means of the LLL algorithm (modified LLL algorithm) is applied being illustrated by four examples. In particular, we prove that in general it is impossible to transform an oblique base of a lattice to an orthogonal base by Gram-Schmidt orthogonalization where its matrix enties are integer. The volume preserving Gram-Schmidt orthogonalization operator constraint to integer entries produces “almost orthogonal” bases which, in turn, can be used to produce the integer-valued unknown parameters (initial cycle ambiguities) from the LLL algorithm (modified LLL algorithm). Systematic errors generated by “almost orthogonal” lattice bases are quantified by A. K. Lenstra et al. (1982) as well as M. Pohst (1987). The solution point of Integer Least Squares generated by the LLL algorithm is = (L')⁻¹[L'◯] ∈ ℤ ^m where L is the lower triangular Gram-Schmidt matrix rounded to nearest integers, [L], and = [L'◯] are the nearest integers of L'◯, ◯ being the real valued approximation of z ∈ ℤ ^m , the m-dimensional lattice space Λ. Indeed due to “almost orthogonality” of the integer Gram-Schmidt procedure, the solution point is only suboptimal, only close to “least squares.” ? 2000 John Wiley & Sons, Inc.  相似文献