The importance of three centuries of land-use change for the global and regional terrestrial carbon cycle

Large amounts of carbon (C) have been released into the atmosphere over the past centuries. Less than half of this C stays in the atmosphere. The remainder is taken up by the oceans and terrestrial ecosystems. Where does the C come from and where and when does this uptake occur? We address these questions by providing new estimates of regional land-use emissions and natural carbon fluxes for the 1700–2000 period, simultaneously considering multiple anthropogenic (e.g. land and energy demand) and biochemical factors in a geographically explicit manner. The observed historical atmospheric CO₂ concentration profile for the 1700 to 2000 period has been reproduced well. The terrestrial natural biosphere has been a major carbon sink, due to changes in climate, atmospheric CO₂, nitrogen and management. Due to land-use change large amounts of carbon have been emitted into the atmosphere. The net effect was an emission of 35 Pg C into the atmosphere for the 1700 to 2000 period. If land use had remained constant at its distribution in 1700, then the terrestrial C uptake would have increased by 142 Pg C. This overall difference of including or excluding land-use changes (i.e. 177 Pg C) comes to more than half of the historical fossil-fuel related emissions of 308 Pg C. Historically, global land-use emissions were predominantly caused by the expansion of cropland and pasture, while wood harvesting (for timber and fuel wood) only played a minor role. These findings are robust even when changing some of the important drivers like the extent of historical land-use changes. Under varying assumptions, land-use emissions over the past three centuries could have increased up to 20%, but remained significantly lower than from other sources. Combining the regional land-use and natural C fluxes, North America and Europe were net C sources before 1900, but turned into sinks during the twentieth century. Nowadays, these fluxes are a magnitude smaller than energy- and industry-related emissions. Tropical regions were C neutral prior to 1950, but then accelerated deforestation turned these regions into major C sources. The energy- and industry-related emissions are currently increasing in many tropical regions, but are still less than the land-use emissions. Based on the presented relevance of the land-use and natural fluxes for the historical C cycle and the significance of fossil-fuel emissions nowadays, there is a need for an integrated approach for energy, nature and land use in evaluating possible climate change mitigation policies.     

Changing hillslope and fluvial Holocene sediment dynamics in a Belgian loess catchment

Floodplain deposition is an essential part of the Holocene sediment dynamics of many catchments and a thorough dating control of these floodplain deposits is therefore essential to understand the driving forces of these sediment dynamics. In this paper we date floodplain and colluvial deposition in the Belgian Dijle catchment using accelerator mass spectrometric radiocarbon and optical stimulated luminescence dating. Relative mass accumulation curves for the Holocene were constructed for three colluvial sites and 12 alluvial sites. A database was constructed of all available radiocarbon ages of the catchment and this database was analysed using relative sediment mass accumulation rates and cumulative probability functions of ages and site‐specific sedimentation curves. Cumulative probability functions of ages were split into different depositional environments representing stable phases and phases of accelerated clastic deposition. The results indicate that there is an important variation between the different dated sites. After an initial stable early and middle Holocene phase with mainly peat growth in the floodplains, clastic sedimentation rates increased from 4000 BC on. This first phase was more pronounced and started somewhat earlier for colluvial deposits then for alluvial deposits. The main part of the Holocene deposits, both in colluvial and alluvial valleys, was deposited during the last 1 ka. The sedimentation pattern of the individual dated sites and the catchment‐wide pattern indicate that land use changes are responsible for the main variations in the Holocene sediment dynamics of this catchment, while the field data do not provide indications for a climatological influence on the sediment dynamics. Copyright © 2011 John Wiley & Sons, Ltd.     

Incised palaeo-channels of the late Middle Pleistocene Thames: age,origins and implications for fluvial palaeogeography and sea-level reconstruction in the southern North Sea basin

Multidisciplinary investigations of the infills of steeply-incised buried channels on the coast of Essex, England, provide important insights into late Middle Pleistocene climate and sea-level change and have a direct bearing on the differentiation of MIS 11 and MIS 9 in terrestrial records. New data are presented from Rochford and Burnham-on-Crouch where remnants of two substantial palaeo-channels filled with interglacial sediment can be directly related to the terrace stratigraphy of the Thames. The sediments in both channels accumulated in an estuarine environment early in an interglacial when mixed oak forest was becoming established. Lithological evidence suggests that the interglacial beds post-date the brackish-water infill of an older palaeo-channel ascribed to the Hoxnian and correlated with part of MIS 11, and pre-date terrace gravels (Barling Gravel) ascribed to MIS 8. An MIS 9 attribution is supported by molluscan biostratigraphy, palaeo-salinity and amino-acid racemization data. The relative sea-level record in this area thus includes evidence for two major marine transgressions during MIS 11 and MIS 9, with local maxima of >10 m O.D. Both are associated with sediments that show ‘Hoxnian’ palynological affinities. The wider significance of these findings, and of an intermediate phase of pronounced fluvial incision during MIS 10, is discussed.     

Modelling mean annual sediment yield using a distributed approach

In this paper a spatially distributed model for the calculation of sediment delivery to river channels is presented (SEDEM: SEdiment DElivery Model). The model consists of two components: (1) the calculation of a spatial pattern of mean annual soil erosion rates in the catchment using a RUSLE (Revised Soil Erosion Equation) approach; and (2) the routing of the eroded sediment to the river channel network taking into account the transport capacity of each spatial unit. If the amount of routed sediment exceeds the local transport capacity, sediment deposition occurs. An existing dataset on sediment yield for 24 catchments in central Belgium was used to calibrate the transport capacity parameters of the model. A validation of the model results shows that the sediment yield for small and medium sized catchments (10–5000 ha) can be predicted with an average accuracy of 41 per cent. The predicted sediment yield values with SEDEM are significantly more accurate than the predictions using a lumped regression model. Moreover a spatially distributed approach allows simulation of the effect of different land use scenarios and soil conservation techniques. Copyright © 2001 John Wiley & Sons, Ltd.     

Crustal structure of northeastern Tibet inferred from receiver function analysis

Sponsored by National Science & Technology Committee, the cooperation between China Academy of Geoscience and Institute of Geophysics and Tectonics, University Joseph, France conducted a lithospherical experiment using 40 Minititan 3-component and 13 CEIS 1-component seismometers along the road from Gonghe to Yushu in Qinghai Province during 5 months after June, 1998. The interested area is on the north of Bangong- Nujiang fault, the east of Qaidam basin, the south of Center Qilian fault and the west of Longmenshan fault. And the profile across most tectonic parts of Eastern Tibet such as Southern Qilian, Eastern Kunlun fault, Bayan Har terrane, Jinshajiang suture (Figure 1), which is the first seismological profile across Eastern Tibet (Qinghai-Tibet) and will be beneficial on the comparison with the results of its center parts, especially on the understanding of the effect of the thousands-kilometer-faraway collision between Eurasia Plate and Indian Plate on the uplifting of south and north part of Eastern Kunlun fault, and on the thickening of crust and the feature of deep structure of Qilian mountain on the north of Tibet Plateau.     

Excess protactinium in phosphate nodules from a coastal upwelling zone

Measurements of²³¹Pa/²³⁵U and²³⁰Th/²³⁴U activity ratios have been made for a suite of Quaternary age phosphate nodules from the upwelling zone off Peru and Chile. Many of these samples contain more²³¹Pa than would be predicted based on closed-system²³⁰Th/²³⁴U ages unlike samples from non-upwelling environments which have been shown to have concordant²³¹Pa and²³⁰Th ages. Peru/Chile phosphate nodules apparently pick up²³¹Pa preferentially to²³⁰Th. This is most likely a result of prior fractionation of protactinium and thorium in the open ocean. Highly productive coastal upwelling zones may be added to the growing list of localities where fractionation between thorium and protactinium isotopes has been observed in marine sediments.     

The formulation of an effective demulsifier for oil spill emulsions

The formation of stable sea water-in-crude oil emulsions after an oil spill was first reported after the Torrey Canyon wreck in 1967. The problem of handling this stable water (65%)-in-oil (35%) emulsion rather than oil is evidenced in the additional expensive on-site storage requirement as well as the handling difficulty with the viscous semi-solid emulsion. This paper details the results of an R&D program that has established the mechanism for the formation of this emulsion. This insight enabled a specific effective chemical demulsifier to be formulated. A treatment technique was devised that entails injecting the demulsifier into the oil spill emulsion as it is skimmed from the water surface. The emulsion is then rapidly separated into water-free oil and a clean-water phase that can be decanted back into the sea. Full-scale tests were successfully conducted by JBF Scientific Corp. using two types of commercial JBF DIP skimmers in a small concrete lined pond.     

Mineralogy of Erromango lavas (New Hebrides): Evidence of an early stage of fractionation in island arc basalts

The orogenic volcanic rocks of Erromango island are divided into a Quaternary theoleiitic group and an older Pliocene one showing calc-alkalic affinity. The microprobe mineralogy of these lavas agrees with this geochemical distinction and indicates a marked iron enrichment trend in the recent tholeiitic lavas, whereas titanomagnetite occurs as early formed phenocrysts (Al, Cr, Mg-rich) only in Pliocene basalts. Some Ni and Mg-rich olivine phenocrysts (Fo88) and unusual chemically zoned clinopyroxene megacrysts are described from Pliocene basic lavas and interpreted as deep-fractionated minerals. The large compositional range of these latter (diopside core to augite rim, through salite intermediate zone) leads us to discuss the physical conditions and the corresponding cation substitutions prevailing during their formation. Diopside cores crystallized at depths of about 20 km from a relatively ‘primitive’ melt. The formation of salite is considered to be the result of concomitant fractionation of Mg-rich phases and increase of f_O2. An early stage of fractionation of Cr-bearing diopside + Ni-bearing olivine would account for the typical Cr and Ni depletion of Erromango lavas.     

A Note on Second Species Solutions Generated from p–q Resonant Orbits

The first image under the flow of the restricted three-body problem of the p—q resonant strips — that appear in the study of the p—q resonant orbits — do not have, in general, intersection with the strip. In this paper we show some particular situations in which the above intersections exist for some very simple p—q resonant orbits which, at the same time, are periodic second species solutions.This revised version was published online in October 2005 with corrections to the Cover Date.     

Three-Dimensional p–q Resonant Orbits Close to Second Species Solutions

The purpose of this paper is to study, for small values of , the three-dimensional p–q resonant orbits that are close to periodic second species solutions (SSS) of the restricted three-body problem. The work is based on an analytic study of the in- and out-maps. These maps are associated to follow, under the flow of the problem, initial conditions on a sphere of radius around the small primary, and consider the images of those initial points on the same sphere. The out-map is associated to follow the flow forward in time and the in-map backwards. For both mappings we give analytical expressions in powers of the mass parameter. Once these expressions are obtained, we proceed to the study of the matching equations between both, obtaining initial conditions of orbits that will be 'periodic' with an error of the order ^1–, for some (1/3,1/2). Since, as 0, the inner solution and the outer solution will collide with the small primary, these orbits will be close to SSS.