Buried Wood Research Articles

The effects of diagenetic aromatization on the carbon and hydrogen isotopic composition of higher plant di- and triterpenoids: Evidence from buried wood

The widely distributed aromatic di- and triterpenoids from higher plants occurring in sediments are formed by diagenetic microbial processes affecting their precursor plant lipids. These compounds and their stable isotopic composition (δ13C and δ2H) have the potential to be used for palaeoenvironmental and palaeoclimatic studies. In the present study, the isotopic composition of di- and triterpenoids aromatized to different extents has been measured to specifically examine the isotopic effects associated with the aromatization reaction. To overcome the possibility of multiple higher plant sources, as is generally the case with sedimentary lipids, the δ13C and δ2H values of aromatized di- and triterpenoids from lipid extracts recovered from conifer and angiosperm buried wood have been determined, allowing an unambiguous substrate/product relationship along the aromatization pathway to be assured. The results show that the δ13C compositions of both di- and triterpenes do not seem to be significantly affected by progressive aromatization, whereas the situation is different for δ2H values. In the case of diterpenoids related to abietic acid, a significant increase of the δ2H values by up to 86‰ with ongoing aromatization was measured. This is in contrast to what is expected for dehydrogenated compounds which should be globally more 2H-depleted than their precursor molecules (e.g., biosynthesized unsaturated fatty acids vs. their saturated precursors). This 2H enrichment of aromatized diterpenoids could indicate that they represent only minor residual intermediates, the majority having been further degraded by processes favoring the degradation of the 1H-containing substrates and having a moderately pronounced 12C/13C selectivity. With triterpenoids, preservation of the δ2H values was observed whatever the nature and extent of the aromatization process considered, which may be related to enzymatic reactions showing a limited influence on the hydrogen stable isotopic composition of the aromatized compounds.

Dynamics of detrital carbon pools following harvesting of a humid eastern Canadian balsam fir boreal forest

Forest management strongly influences the carbon (C) budget of boreal forests and their potential to mitigating greenhouse gas emissions. A better quantification of the net changes of carbon pools with time since harvesting is necessary to guide the development of climate-friendly forest management practices. The objective of this study was to assess the evolution of forest C pools, with a special focus on detrital biomass, in an 80-year post-harvesting chronosequence consisting of 36 very homogenous stem-only harvested plots from a humid boreal balsam fir forest of eastern Canada. Dead wood C stocks comprised of snags, stumps, downed woody debris and buried wood averaged 37 Mg C ha−1 and evolved according to an upward-facing «boomerang» shape pattern throughout the chronosequence (rapid decrease in the first years followed by a constant increase until the end of the time horizon). In contrast, soil C stocks (FH and mineral) averaged 156 Mg C ha−1 and remain constant through time. Stand C sequestration increased rapidly in the early stages up to age 50 when it reached about 250 Mg C ha−1, and then continued to accumulate at a slower rate. The temporal trends observed in C pools suggest that C originating from aboveground dead wood (snags, stumps, downed woody debris) is either leaving the system (respired or leached) or transferred into buried wood, and does not appear to influence the C stocks of the fine fraction of the organic and mineral soil horizons. However, the ultimate fate of dead wood C is still poorly understood and further research is needed in this field. We recommend fixing the length of harvest rotation at a minimum of 50 years for this ecosystem to allow the build-up of its dead wood capital, and to promote dead wood retention on site. We also recommend including buried wood in carbon inventories as this pool represents an important share of the detrital C stock in these humid boreal forests.

Investigation into factors affecting jacking force: a case study

This study investigates the influencing factors affecting jacking loads during slurry pipe-jacking works at four drives in the Shulin district sewer network in Taipei County, Taiwan, with lengths between 73 and 126 m. The main factors affecting jacking loads during tunnelling may include: (a) overcut annulus and volume of injected lubricant; (b) work stoppages; (c) geology; and (d) misalignment. In the four pipe-jacking drives, the jacking forces are represented using the baseline technique. Results show that local variations (increasing or decreasing) of jacking force are ascribed to the varying face resistance due to driving between coarse soil and fine soil governed sand or gravel deposit or driving into and away from a buried wooden log. The increase in jacking loads could also be due to increasing friction resistance resulting from the pipe deviation being greater than a threshold value of 60 mm. Excessive injected volumes of lubricant result in very low pipe frictions incurred during pipe-jacking of the four drives and are reflected through the back-analysed μavg values, which vary from 0·02 to 0·09. Jacking load increases due to either overnight stoppages or short breaks are more pronounced in poorly graded gravel or sand deposit than in clayey gravel or clayey sand deposit.

Mineralogy of Paleocene Petrified Wood from Cherokee Ranch Fossil Forest, Central Colorado, USA

An extensive fossil forest discovered in 2010 on private property in central Colorado, USA, has not previously been described in scientific literature. Horizontal partial logs originated as fluvially transported driftwood. A preliminary study of petrified wood specimens reveals evidence of a complex mineralization sequence that involved multiple episodes of mineral deposition, combined with diagenetic transformation of silica minerals. Specimens from two logs have opalized cell walls. However, minerals filling the cell interiors of these specimens vary. Vessel lumina are filled with chalcedony or crystalline quartz; tracheid lumina may contain opal or chalcedony. Specimens from 5 other logs contain quartz/chalcedony, but relict textures suggest cell walls were originally mineralized with opal that was later converted to microcrystalline silica. Pyrite, calcite, and iron oxides were observed as minor constituents in some specimens, providing additional evidence that fossilization occurred in multiple stages, with temporal and spatial variations in physical and chemical conditions causing episodic precipitation of various minerals within the buried wood. Trace element analyses suggest that Fe is the main source of fossil wood color.

Sorption and thermodynamic properties of wood of Pinus canariensis C. Sm. ex DC. buried in volcanic ash during eruption

The hygroscopicity and thermodynamic properties of Pinus canariensis wood buried in volcanic ash, dating from 1100 BC, were studied and compared with recently felled juvenile and mature wood of the same species. The sorption isotherms were obtained by the saturated salt method at 35 and 50 °C. The isotherms were fitted using the Guggenheim–Anderson–de Boer model. The thermodynamic parameters were determined following the Clausius–Clapeyron integration method. To understand the behaviour of each type of wood, the chemical composition, infrared spectra and X-ray diffractograms were determined for each sample. The mature wood has a higher sugar content and lower extractive content than the juvenile and the buried wood. For both temperatures, the isotherm of the mature wood is above the isotherm of the juvenile wood and this, in turn, is above the isotherm of the buried wood, primarily influenced by the higher cellulose and hemicellulose contents and lower extractives content in the mature wood, resulting in a higher number of accessible –OH groups. Degradation of the buried wood due to high temperatures explains why its isotherms are below the isotherms of the recent wood. The energy involved in the desorption process is greater than in adsorption. Similarly, more energy is involved in the mature wood than in the juvenile wood, and the energy involved in the juvenile wood is greater than in the buried wood.

Patterns of carbon, nitrogen and phosphorus dynamics in decomposing wood blocks in Canadian forests

We measured changes in mass and in carbon (C), nitrogen (N) and phosphorus (P) concentrations and content of surface-placed and buried wood blocks decomposing over 12 years at 21 sites across Canada to evaluate the influence of the environment on C, N, and P dynamics. Carbon decomposition over time was best described using a sigmoidal fit, which was slightly better than a negative exponential function. Decomposition was slow at cold and wetland sites, with less than 15 % of the original C content lost after 12 years for 4 upland and 3 wetland sites. Decomposition rates were faster for buried than for surface blocks, except in wetlands and in a few upland sites that had high annual precipitation. Nitrogen was gained during the early stages of decomposition, followed by a net N loss once an average C:N mass ratio of 165 was reached for all upland surface-placed blocks, and 200 for upland buried blocks. Critical C:N values were weakly correlated with C:N ratios in the surface organic horizon, suggesting an influence of forest floor properties on decomposition dynamics with N release occurring sooner on more fertile sites. Critical values for N and P mineralization were greater than those reported for foliar litters.

Late Tertiary Petrified Wood from Nevada, USA: Evidence of Multiple Silicification Pathways

Late Tertiary fossil woods from the state of Nevada provide an opportunity for observing the mineralization sequences that cause buried wood to become permineralized. Oligocene and Miocene caldera basins contain abundant petrified wood that ranges in composition from incipient silicification to complete permineralization. Examination of specimens from 21 localities reveals that the petrifaction sequence can follow multiple pathways. Fossil wood specimens from a single stratum may have different mineralization; silicification may vary even within a single specimen. Despite these variations, several trends are evident. Features in Nevada specimens suggest that two fundamental processes are involved: early mineralization of cell walls, and later silica deposition in lumina, vessels, and rot pockets from groundwater that permeated these open spaces. The process of open-space filling may be analogous to the genesis of geodes and veins, where multiple episodes of hydrothermal precipitation may produce opal, chalcedony, and quartz as deposits within a single cavity. Silica polymorphs may coexist as primary precipitates, or they may originate from solid-state transformation of a single parent material. Relic lepisphere textures observed in some chalcedony wood specimens are evidence of opal→chalcedony transition. In Nevada, specimens that contain crystalline quartz, this mineral appears to have been formed by direct precipitation in open spaces, not from recrystallization of chalcedony. Opal-A has seldom been reported in fossil wood, but this amorphous material is fairly common in Nevada specimens.

Comparative 230Th/U and 14C Dating of a Buried Stump Layer (Western Siberia)

Abstract Dating of late Pleistocene sediments remains a challenge in Quaternary chronology, due to the inherent limitations of the 14C and OSL methods. The 230Th/U radioisotope method is theoretically applicable to wood remnants contained within Pleistocene sediments, but few results have been pub-lished to date and in some cases, the age data are ambiguous. This paper tests the use of 230Th/U da-ting of fossil wood remnants dated earlier by radiocarbon method. We analyzed a buried larch trunk from a well-known stump layer in the Lipovka outcrop, located on the Tobol River bank in Western Siberia. The stump layer is preserved in situ. We determined the specific activities of U and Th iso-topes in samples of both modern pine and fossil larch and proposed a model for the incorporation and distribution of U and Th in the buried wood during aging. Complications related with the recognition of geochemical closed systems with respect to U did not allow obtaining completely reliable 230Th/U age. Despite this the 230Th/U age obtained for the uppermost heartwood sample and 14C ages of the same larch trunk and other wood and vegetation remnants gave consistent results. These age data in combination with previously obtained pollen data testify the stump layer formation during the late cooling stage of the Karganian time (MIS-3, Middle Valdai).

Imaging tropical peatlands in Indonesia using ground-penetrating radar (GPR) and electrical resistivity imaging (ERI): implications for carbon stock estimates and peat soil characterization

Abstract. Current estimates of carbon (C) storage in peatland systems worldwide indicate that tropical peatlands comprise about 15% of the global peat carbon pool. Such estimates are uncertain due to data gaps regarding organic peat soil thickness, volume and C content. We combined a set of indirect geophysical methods (ground-penetrating radar, GPR, and electrical resistivity imaging, ERI) with direct observations using core sampling and C analysis to determine how geophysical imaging may enhance traditional coring methods for estimating peat thickness and C storage in a tropical peatland system in West Kalimantan, Indonesia. Both GPR and ERI methods demonstrated their capability to estimate peat thickness in tropical peat soils at a spatial resolution not feasible with traditional coring methods. GPR is able to capture peat thickness variability at centimeter-scale vertical resolution, although peat thickness determination was difficult for peat columns exceeding 5 m in the areas studied, due to signal attenuation associated with thick clay-rich transitional horizons at the peat–mineral soil interface. ERI methods were more successful for imaging deeper peatlands with thick organomineral layers between peat and underlying mineral soil. Results obtained using GPR methods indicate less than 3% variation in peat thickness (when compared to coring methods) over low peat–mineral soil interface gradients (i.e., below 0.02°) and show substantial impacts in C storage estimates (i.e., up to 37 MgC ha−1 even for transects showing a difference between GPR and coring estimates of 0.07 m in average peat thickness). The geophysical data also provide information on peat matrix attributes such as thickness of organomineral horizons between peat and underlying substrate, the presence of buried wood, buttressed trees or tip-up pools and soil type. The use of GPR and ERI methods to image peat profiles at high resolution can be used to further constrain quantification of peat C pools and inform responsible peatland management in Indonesia and elsewhere in the tropics.

Reinvestigation of the structure of a tetracyclic terpenoid from geological samples: A novel marker for fungi involved in the degradation of buried wood?

A tetracyclic compound tentatively assigned as A-nor-friedel-8-en-10-one was recently reported by Bakar et al. (2011) [Bakar, N.A., Tay, K.S., Omar, N.Y.M.J., Abas, M.R.B., Simoneit, B.R.T., 2011. Applied Geochemistry 26, 1433–1445] from a Malaysian lake sediment. It was postulated to derive from friedelin via a sequence of diagenetic transformations involving the unprecedented removal of ring A and several hypothetical intermediates. We considered that this structural assignment needed to be reassessed, notably because we could detect the compound in wood samples devoid of friedelin-related triterpenes. Firm identification was also needed since the compound is becoming used as a proxy in recent publications and its occurrence interpreted in terms of palaeoenvironmental reconstruction. In the course of archaeometric studies of ancient buried wood, the presence of the compound as a predominant constituent of the lipid extract of a buried alder wood sample gave us the opportunity to firmly establish its structure. We report here its unambiguous identification using 1D and 2D nuclear magnetic resonance (NMR) spectroscopy after its isolation. Based on its structure, geochemical distribution and stable carbon isotopic composition, it appears that the compound likely does not derive from triterpenoids biosynthesized by higher plants, but might derive from a precursor terpenoid synthesized by microorganisms (bacteria, fungi) living within the buried wood, and possibly involved in the degradation of plant organic matter (wood, notably).

Contrasting diagenetic pathways of higher plant triterpenoids in buried wood as a function of tree species

Terpenoid biomarkers with high chemotaxonomic value, which can be used for the identification of an angiosperm input to sedimentary organic matter are desirable for studies devoted to the reconstitution of past environmental change. There is also a need, in the framework of archaeometric investigations, for reliable biomarkers to allow wood species determination from archaeological remains. In this context, we report the analysis of the triterpene content of buried wood and bark from oak, alder and birch, and comparison with that of the corresponding fresh material. Identification of new biomarkers led us to elucidate the diagenetic transformations undergone by triterpenoids in buried wood. A large set of triterpenoid biomarkers characterized by the presence of an oxygenated functionality in ring A at C-2 only could be exclusively evidenced in buried oak wood. An overall diagenetic pathway leading from the predominant polyfunctionalized triterpenoids in fresh oak wood (oxygenated functionalities at C-2/C-3/C-19/C-23/C-24/C-28) via numerous C-2 and C-2,C-3 functionalized intermediates to C-2 oxygenated aromatic triterpenoids is proposed. The evolution of the triterpenoid assemblage with respect to the level of diagenetic alteration could be followed. In contrast, the predominant triterpenoids in fresh alder and birch are common C-3 functionalized compounds. Their degradation follows the classical degradation/aromatization pathways reported for C-3 oxygenated triterpenes, ring A degradation appearing to represent only a minor process. In addition, the formation of phenolic triterpenoids, which have only been reported from brown coal, was observed.

Triterpenoids functionalized at C-2 as diagenetic transformation products of 2,3-dioxygenated triterpenoids from higher plants in buried wood

Several oleanane-related triterpenoids bearing a unique C-2 oxygenated functionality have been identified as the predominant triterpenoids from a 4900 year old oak wood sample buried in a freshwater sediment. They likely represent specific molecular tools that can be used as markers to reconstruct past vegetation assemblages, or to recognise severely altered oak wood at archaeological sites.

Iron speciation in iron-rich wood by Mössbauer spectroscopy

Several iron-rich wood samples were investigated using Mössbauer spectroscopy to obtain information on the chemical state of the iron species contained in them. The Mössbauer spectrum of Japanese cedar (Cryptomeria japonica D. Don) wood containing iron species that originated from rusted nails exhibited a symmetrical doublet from a high-spin Fe(III) species, which is expected to be γ-FeOOH (lepidocrocite). Mössbauer absorption attributable to high-spin Fe(III) was observed for ancient buried wood samples of both Japanese cedar and Japanese cypress (Chamaecyparis obtusa Endlicher). Moreover, Mössbauer measurement indicated that the ancient buried Japanese cedar also possessed high-spin Fe(II) species.

Constraining the age of the last interglacial–glacial transition in the Hudson Bay lowlands (Canada) using U–Th dating of buried wood

Paleoecological investigations of organic-rich sediments and radiometric dating of fossil wood fragments were undertaken to constrain the age of an extensive pre-Holocene nonglacial sediment sequence exposed along the Nottaway River in the southeastern sector of the Hudson Bay Lowlands, a key region for the study of the dynamics of the Laurentide ice sheet (LIS). Pollen and macrofossil analyses indicate that these sediments were deposited under climate conditions similar to those of today, whereas radiocarbon dating of a wood log yielded an age beyond the effective limit of this method. U and Th isotopic analysis on 9 fossil and 1 modern wood samples showed that the fossil wood fragments were subject to a significant episode of U uptake during burial. Despite mechanical cleaning of the wood outer surfaces, non-authigenic 230Th was found in most wood samples. Correction for this detrital contamination was made using 232Th as an index and assuming typical crustal Th/U ratio. Plotting of the data within a 3-D isochron indicates that the presence of non-authigenic 230Th is not the only factor affecting the U–Th system, thereby showing evidence for a complex pattern of U uptake and/or intermittent open system behavior. This U mobility, however, appears to have been limited, as indicated by the relatively narrow range of corrected 230Th/U ages and the cluster of U–Th data between the 100–120 ka isochrons in the U-series evolution diagram. Taken together, our paleoecological and U–Th results tend to suggest that the apparent calculated corrected 230Th/U ages may be considered as a reliable geochronological constraint that assigns the Nottaway River sediments to the end of the last interglacial (marine isotopic stage 5e). The high degree of compaction of the fine-grained deposits enclosing the fossil wood appear to be one of the main factor that limited hydraulic gradients and associated isotopic fluxes through the unit. The stratigraphic context indicates that the overconsolidated nature of the wood-bearing deposit is associated with ice advance in the region. Accordingly, the minimum age limit provided by the corrected 230Th/U ages (i.e., ∼100 ka) may also be interpreted as a coarse constraint on the timing and extent of the eastern sector of the LIS at the onset of the last glacial cycle.

Radiocarbon ages by accelerator mass spectrometry of buried wood materials from Kisogawa volcanic mudflow deposits at Yaotsu-chou, Gifu prefecture

Radiocarbon ages by accelerator mass spectrometry of buried wood materials from Kisogawa volcanic mudflow deposits at Yaotsu-chou, Gifu prefecture

Effects of burial of Quercus spp. wood aged 5910 ± 250 BP on sorption and thermodynamic properties

The hygroscopicity and thermodynamic properties of buried Quercus spp. wood aged 5910 ± 250 BP were studied and compared with wood of the same genus from recently felled trees. This was done by calculating the 35 °C and 50 °C sorption isotherms and fitting them in accordance with the GAB model. The thermodynamic parameters were obtained from the isotherms using the integration method of the Clausius–Clapeyron equation. Infrared spectra (FTIR) and X-ray diffractograms, respectively, were used to determine possible chemical modifications and changes in the crystalline structure of the cell wall. The long period of time the wood was buried caused a decrease in the crystallinity index of the cellulose and a subsequent increase of amorphous zones with new areas of access for –OH groups. As a result, the equilibrium moisture contents of the buried wood are higher than in the recent wood, in both adsorption and desorption. In terms of the thermodynamic properties, the heat involved is greater in the buried wood than in the recent wood.

Dead Wood is Buried and Preserved in a Labrador Boreal Forest

Large amounts (36.4 Mg ha−1 or 179 m3 ha−1) of buried dead wood were found in overmature (146–204-year-old) black spruce (Picea mariana (Mill.) B.S.P.) forests in the high boreal region of eastern Canada. Amounts of this size indicate that burial reduces rates of wood decay producing an important component of long-term carbon (C) storage. Radiocarbon-derived ages of black spruce stems buried near the bottom of the organic soil horizon at three old-growth sites were up to 515 years old. Together with information on current stand age, this suggests that the stems have been dead for more than 250 years. Most aboveground dead wood decays or becomes fragmented within about 70 years of tree death in these forests. The presence of old yet well-preserved buried wood suggests that decay rates are greatly reduced when downed dead wood is quickly overgrown by moss. Thus, the nature and type of ground-layer vegetation influences the accumulation of organic matter in these forests. This process of dead wood burial and the resultant addition to a large and long-enduring belowground C pool should be considered when estimating dead wood abundance for habitat or forest C accounting and cycling.

Sorption and thermodynamic properties of buried juvenile Pinus sylvestris L. wood aged 1,170 ± 40 BP

The hygroscopicity and thermodynamic properties of buried juvenile Pinus sylvestris L. wood with an age of 1,170 ± 40 BP were compared with the corresponding values of juvenile wood of the same species from recently cut trees. The 35 and 50°C isotherms were plotted following the saturated salts method and subsequently fitted in accordance with the GAB model. The isotherms were then compared by means of the hysteresis coefficients. X-ray diffractograms were used to analyse the crystal structure of the cellulose. The effect of time on the buried wood caused hemicelluloses degradation and a decrease in the crystallinity index and the crystallite length, resulting in an increase in the proportion of amorphous zones. Because of this, the equilibrium moisture contents of the buried wood are higher than of the recent wood, both in adsorption and desorption. In terms of the thermodynamic properties, the heat involved is greater in the buried wood than in the recent wood.

Holocene ages and inland source of wood blocks that emerged onto the seafloor during the 2007 Chuetsu-oki, central Japan, earthquake

Abstract At least 300 tons of subrounded to well-rounded wood blocks emerged onto the seafloor at a water depth of 70–100 m during the 2007 M w 6.6 Chuetsu-oki, central Japan, earthquake. Radiocarbon dating and taxonomic identification of eight of those wood blocks suggest that they were transported from inland during the middle to late Holocene, buried by subsequent sedimentation, and brought up onto the seafloor in 2007, most likely by submarine liquefaction induced by strong shaking. In particular, all eight blocks gave ages older than 2500 cal yr BP, implying the possibility that the 2007 earthquake was the first earthquake during the last two millennia to have caused shaking strong enough to induce submarine liquefaction in the 2007 meizoseismal area. However, we cannot rule out the possibility of multiple large earthquakes after approximately 2 ka, if the buried wood sources cannot be emptied by a single earthquake. Further studies are required to examine paleoseismic implications of the emergence of these wood blocks in 2007.

The use of a high-resolution 3D Chirp sub-bottom profiler for the reconstruction of the shallow water archaeological site of the Grace Dieu (1439), River Hamble, UK

The remains of Henry V's flagship, the Grace Dieu, currently lie buried within the inter-tidal sediments of the River Hamble (S. England). Previous archaeological investigations have been hindered by difficult excavation conditions resulting in a poor understanding of the dimensions, shape and degradation state of the hull's deeper structure. This study therefore aimed to image, characterize and reconstruct the buried remains of this vessel using a high-resolution 3D acoustic sub-bottom Chirp system with RTK-GPS positioning capability. The accurate navigation and high-resolution data that were acquired enabled the construction of a full 3D image of the site that not only identified the remains of the wooden hull, but also features buried within it. In addition, the degradation state of these buried wooden remains were investigated by calculating reflection coefficients while a hypothetical larger reconstruction of the Grace Dieu's hull was achieved, through the use of the ShipShape ship design software package. The results of this project demonstrate that (i) acoustic data can be used to successfully image buried wooden shipwrecks, (ii) artefacts are buried within the hull of the Grace Dieu, (iii) there is variation in the degradation state of the buried timbers, as calculated from the acoustic data, with the shell of the vessel being moderately well preserved, and (iv) the Grace Dieu was a very large ship for its time (possibly over 60 m long and 16 m wide). The outcomes of this research not only have considerable implications for the management and monitoring of submerged and buried archaeological sites but also for planning intrusive surveys, should they be required.