Peter Becker-Heidmann

Carbon in tropical wetlands

Abstract About half of the worlds wetlands area is found in the tropics. The importance of wetlands to the global carbon cycle, water balance, wildlife, biodiversity and human food production is much greater than their proportional surface area on Earth (7%) would suggest. High net primary production of organic matter produced by retarded decomposition make natural tropical wetlands an important sink for carbon. About 250 Gt carbon are conserved in tropical wetlands. Tropical wetlands are also a significant source for atmospheric methane. Wetland rice agriculture alone contributes 5 to 20% to the global methane budget. Rice, the stable food for about half of mankind, is grown on tropical wetlands. Small differences in climate, water and nutrient regimes, and land use can drastically change the delicate balance of tropical wetlands.

Twenty-Five Years of Radiocarbon Dating Soils: Paradigm of Erring and Learning

Soil organic matter sequesters close to three times the carbon existing totally in the living biomass and nearly the same for the total carbon in the atmosphere. Models, such as Jenkinsons or Partons Century model, help to define soil organic matter fractions of different functions, based on residence time/14C age. Rejuvenation of soil carbon was felt to be the principal impediment to absolute soil dating, in addition to the ambiguity of the initiation point of soil formation and soil age. Recent studies, for example, of Becker-Heidmann (1989), indicate that a soil 14C age of >1000 yr cannot have >0.1% rejuvenation in the total soil organic matter compartments/fractions to be possible and sustainable. Always problematic in earlier observations were age vs. depth increases, in 14C profile curves showing an inflection of reduced age in the deepest samples, i.e., from the rim of the organic matter containing epipedon. We attribute this phenomenon, in mollic horizons, to earthworm casts in the terminal part of the escape tube. Becker-Heidmann (1989) has shown, in thin layer soil profile dating, a highly significant correlation between the highest 14C ages and the highest clay content. Thus, optimization of soil dating is, to a lesser degree, related to the applied extracting solvent system than to soil texture fractions. Such observations allow us to mitigate error ranges inherent in dating dynamic soil systems.

Bomb-carbon, 14C-dating and 13C — Measurements as tracers of organic matter dynamics as well as of morphogenetic and turbation processes

Abstract Organic matter dynamics can be traced by the thermonuclear-bomb-test induced rise of natural C-14, the “bomb-C”, in the whole photosynthesis - nutrition - organic decomposition chain. Layerwise C-14 dated soil profiles from 1965–1980 and past 1980 are evaluated for bomb-C depth penetration. The problem of soil rejuvenation or aging by Bomb-C or fossil fuel-C in conjunction with nutrient pool transfer and enhancement of organic matter production is described. C-dynamics is reflected also by D 14 C and δ 13 C levels in thin layerwise sampled soil profiles of different climates. These measurements can contribute to clarify the C-dynamics in morphogenetic processes, such as our examples of peloturbation and bioturbation.

Thin layer delta (super 13) C and D (super 14) C monitoring of "lessive" soil profiles.

The natural /sup 14/C and /sup 13/C content organic matter and their dependence on depth for two Alfisols are presented. This soil type which covers a large area of the earths surface is characterized by clay migration processes (Lessive). The samples were taken as successive horizontal layers of 2cm depth from an area of ca 1m/sup 2/ size as deep as the C content allows /sup 14/C analysis. The minima of the D/sup 14/C distribution decrease with depth, while the maxima increase in the upper, leached horizon (A/sub 1/) due to bomb /sup 14/C and decrease in the lower, clay illuviated (B/sub t/). delta/sup 13/C indicates proceeding decomposition in A/sub 1/ and protection of carbon, probably due to the formation of clay humus complexes in B/sub t/. delta/sup 13/C values were also used for age correction of the /sup 14/C data due to isotopic fractionation. The D/sup 14/C and delta/sup 13/C depth distributions are characterized by sharp peaks at the boundaries of the horizons, probably caused by the influence of textural changes on the transport of C with percolating water.

Studies of soil organic matter dynamics using natural carbon isotopes

In continuation of previous investigations, the depth distributions of the natural abundances of 13C and 14C isotopes were studied in two paddy soil profiles of the Philippines and Taiwan. The depth distributions show the regularity and depth of puddling. Further, the soils can be clearly distinguished with regard to their rate of decomposition and metabolism of organic matter and of the vertical translocation of metabolites. In addition, long-term fixation of organic matter by clay could be detected within a clay-enrichment zone in the subsoil. At the horizon boundaries in one soil, continual rejuvenation of soil organic matter was found, due to pore discontinuities impeding the percolation of organic substances.

Surface and subsurface palaeoseismic records at the ancient Roman city of Baelo Claudia and the Bolonia Bay area, Cádiz (south Spain)

Abstract The Roman archaeological site of Baelo Claudia (Cádiz, south Spain) is located within the Gibraltar Arch, a region with no significant recent or historical seismicity. However, previous studies have emphasized the occurrence of repeated strong archaeoseismic damage (intensity≥IX MSK) at Baelo Claudia tentatively bracketed in this study around ad 40–60 and ad 260–290. A multidisciplinary study has been carried out including the detailed mapping of surface deformation and building damage, surface geology and geomorphology, collection of structural data, and an extensive ground penetrating radar (GPR) survey. The obtained data are not conclusive when considered separately, but evident links between archaeoseismic damage, structural and GPR data indicate that the destruction of the city was linked to seismic shaking. The analysis of the pattern and orientation of deformation clearly indicates SW–NE directed compression due to ground shaking. This analysis also focuses on localized landslides and liquefaction processes, which appear to be coeval with the earthquakes, but the poor geotechnical parameters of the clayey substratum were determinant to amplify the observed level of destruction. The application of the present Spanish seismic code (NCSE-02) indicates that intensity VIII MSK (0.24–0.26 g) can be reached in this zone for 500 year return periods.

Hamburg radiocarbon thin layer soils database.

We report here the remainder of the Hamburg University dates on thin soil layers (HAM 1652-3129).

Tsunami deposits in the western Mediterranean: remains of the 1522 Almerı́a earthquake?

Abstract Shallow drilling in the lagoon of the Cabo de Gata area proved sedimentary evidence for a palaeo-tsunami along that part of the Spanish Mediterranean coast. Several coarse-grained intervals form fining-up and thinning-up sequences that are interpreted as tsunamites. Inland-extending sand sheets are used to identify tsunamigenic inundations. Other indicative features found are erosive bases, rip-up clasts, broken shells of bivalves and benthic/planktic foraminifera. The coarse-grained intervals consist of up to three sequences separated from each other by a silty mud drape. These intervals are interpreted as deposits of a tsunami train and correspond to three individual waves. Radiocarbon dating reveals evidence that these layers can be ascribed to deposition during the 1522 Almerı́a earthquake. The 1522 Almerı́a earthquake (M>6.5) affected large areas in the western Mediterranean and caused more than 1000 casualties. The epicentral area was offshore in the Gulf of Almerı́a (southern Spain) along the Carboneras Fault Zone and seismic shaking triggered submarine slides in the Gulf of Almerı́a, which may have caused tsunami waves. We have also found another intercalation of tsunamites downhole, which are interpreted as either an expression of repeated earthquake activity or tsunami-like waves induced by submarine slides triggered by seismic shaking in the Gulf of Almerı́a. Our evidence suggests a definite tsunami potential and hazard for offshore active and seismogenic faults in the western Mediterranean region.

Radiocarbon dating of soils; database contribution by Bonn and Hamburg.

We present a compilation of 14 C soil dates measured at the University of Hamburg through 1984 (HAM-1597).

Overview of the greenhouse effect : global change syndrome; general outlook

Abstract Accumulation of cosmic dust and planetesimals was most likely the mechanism that created our planet. Due to dominance of hydrogen, the extruded gases produced a primordial reducing atmosphere, enriched with methane and ammonia. Then, after a slow start, continued oxidation with oxygen, released from photolysis of water, and the later development of life from photosynthesis caused the atmosphere to become dominated by CO 2 , water vapor and N. The two former components were able to trap IR radiation and to produce a warming greenhouse effect of 33°C, shifting the surface temperature to +15°C. Oxygen from photosynthesis (at present yearly ca 330 bil t from terrestrial photosynthesis) was used over at least 2 billion years, for sustaining respiration of the various facets of life and for iron oxidation in marine and terrestrial sediments. During the last billion years oxygen began to enrich in the atmosphere, parallel to reducing CO 2 concentration, due to its consumption by photosynthesis, chemical weathering and the carbonate precipitating pumping effect of the oceans. CO 2 replenishment occurs via volcanism and release from subduction zones. The faster biochemical cycle of smaller pool size (organic matter production, respiration, humification, kerogene formation, and biotic-abiotic-photochemical organic matter turnover) and over longer geological periods especially the slow but very large geochemical cycle (exchange of carbon between atmosphere, ocean, biosphere, and sediments), are decisive for CO 2 concentration and its contribution to temperature. Some features of the biochemical cycle against the background of climate changes, including those due to Pangaea/Gondwana shifting, are discussed. Life is on a carbon trip. Wasteful consumption of fossil C based fuel, due to rising living standard and population explosion in conjunction with increasing release of greenhouse active (radiatively active) gases – which are fingerprinted – threatens to exert climate changes detrimental to our life conditions and civilization. Arguments to characterize the situation are assessed, also those expressing potential advantages of increasing CO 2 concentration for crop yields and expansion of the farmland area, doomed to shrinking at the present level of population explosion. The need for a change from the carbon trip to a mixed carbon – hydrogen trip is evident.