FIRE EFFECTS ON SOIL HETEROGENEITY BENEATH CHAMISE AND REDSHANKS CHAPARRAL

The origin of soil heterogeneity found in Adenostoma fasciculatum and A sparsifolium chaparral was investigated in the Santa Monica Mountains, California. Possibilities were that geologic and genetic processes created inherent variability in surface soils, and/or that chaparral vegetation generated this variability. Fourteen soil properties were assessed under 17 pairs of the two shrub species before (1984) and after (1985) a wildfire. Hypotheses were that, although magnitudes of soil properties may change with fire, the inherent soil patterns would remain, while vegetation-influenced patterns might either be accentuated or obliterated. All but one of the 14 soil properties changed after fire, and 8 of these changed in the same direction for both shrub species. Different magnitudes of change, as well as opposite changes in 5 soil properties, led to an elimination of most spatial heterogeneity after fire. Eleven soil properties showed significant pre-burn differences between shrub species, while only 3 did so after fire. Vegetation influence was responsible for the spatial soil heterogeneity in the mature stand of chaparral, apparently developing over one regeneration period of about 40 years. With the obliteration of fine-scale soil differences during each fire cycle, soil heterogeneity cannot play a role in determining vegetation regeneration patterns. The creation of a more uniform substrate after fire, however, may favor sprouting over seeding strategies in postfire succession. [Key words: chaparral, fire ecology, soil properties, California.]     

Cool,wet conditions late in the Younger Dryas in semi-arid New Mexico

A thick alluvial sequence in central New Mexico contains the Scholle wet meadow deposit that traces upstream to a paleospring. The wet meadow sediments contain an abundant fauna of twenty-one species of freshwater and terrestrial mollusks and ten species of ostracodes. The mollusks and ostracodes are indicative of a local high alluvial water table with spring-supported perennial flow but without standing water. Pollen analysis documents shrub grassland vegetation with sedges, willow, and alder in a riparian community. Stable carbon isotopes from the wet meadow sediments have δ¹³C values ranging from ? 22.8 to ? 23.3‰, indicating that 80% of the organic carbon in the sediment is derived from C₃ species. The wet meadow deposit is AMS dated 10,400 to 9700 ¹⁴C yr BP, corresponding to 12,300 to 11,100 cal yr BP and overlapping in time with the Younger Dryas event (YD). The wet meadow became active about 500 yr after the beginning of the YD and persisted 400 yr after the YD ended. The Scholle wet meadow is the only record of perennial flow and high water table conditions in the Abo Arroyo drainage basin during the past 13 ka.     

China Output of Crude Oil Hits High in 2012

According to news from the China Petroleum and Chemical Industry Federation,the crude oil output in China for 2012 was expected to amount to 207 million tons,likely setting the highest record for domestic oil production. In 2012,crude oil output by the China Natural Petroleum Company (CNPC) climbed again after 17 years to the order of magnitude of 110 million tons,with an actual output of 110.33 million tons.Compared to the 2.79 million tons in the previous year,the figure has increased by 2 million tons for three successive years.The crude oil output produced by the CNPC comes mainly from three areas:the Daqing oilfield in Heilongjiang Province,NE China,which has produced more than 40 million tons for ten successive years;the Changqing oilfield in the Odors Basin in north Shaanxi Province,with an annual output of 22.62 million tons;and the Xinjiang,Tarim and Tuha oilfields in western Xinjiang Province,with a total oil output of 18.39 million tons.The domestic production of crude oil by the CNPC in 2012 was 43.185 million tons,with verified oil/gas reserves exceeding 800 million tons of oil equivalent.Currently,China's output for crude oil has not reached its peak and is increasing consistently.     

Metallic Reserves of Submarine Manganese Nodules to be Estimated and Harnessed Prudently: Evidence from China’s Jiaolong Manned Submersible

Since the discovery of oceanic manganese nodules during the expedition of the British ocean-going ship Challenger from 1872 to 1876,research and development for seabed manganese nodules have never ceased owing to the huge economic inducements. Manganese nodules are the black or dark brown,spherical or massive Mn-bearing ores,deposits of which are found on the sea bottom.The nodules are a mixture of silicate and insoluble potassium permanganates (also with sub-Ti,Fe and Na permanganates) that contain more than 30 kinds of metallic elements,among which those of greatest economic interest are Mn (27-30％),Ni(1.25-1.5％),Cu(1-1.4％),Co(0.2-0.25 ％),Fe,Si,and Al,with minor amounts of Ca,Na,K,Ti,B,H and O.     

Roof of the World

First Joint meeting of the Geological Society of China （GSC） and the Geological Society of America （GSA） Brought together by the GSA International Section Chengdu, China in 17-19 June 2013. The abstracts are available online and can be downloaded for free.     

Oxygen and Ethene Biostimulation for a Persistent Dilute Vinyl Chloride Plume

Contamination of groundwater with chlorinated ethenes is common and represents a threat to drinking water sources. Standard anaerobic bioremediation methods for the highly chlorinated ethenes PCE and TCE are not always effective in promoting complete degradation. In these cases, the target contaminants are degraded to the daughter products DCE and/or vinyl chloride. This creates an additional health risk, as vinyl chloride is even more toxic and carcinogenic than its precursors. New treatment modalities are needed to deal with this widespread environmental problem. We describe successful bioremediation of a large, migrating, dilute vinyl chloride plume in Massachusetts with an aerobic biostimulation treatment approach utilizing both oxygen and ethene. Initial microcosm studies showed that adding ethene under aerobic conditions stimulated the rapid degradation of VC in site groundwater. Deployment of a full‐scale treatment system resulted in plume migration cutoff and nearly complete elimination of above‐standard VC concentrations.     

Diagenesis in Okavango fan and adjacent dune deposits with implications for the record of palaeo-environmental change in Makgadikgadi–Okavango–Zambezi basin, northern Botswana

This work considers the spatial distribution and ages of western MOZ basin siliclastic sediments prior to providing insights into the diagenesis of degraded dune and alluvial fan sands. Previously published and new TL/OSL ages imply that extensive over-washing of dune sands took place at least 100 ka ago while ages on Okavango floodplains imply that the fan was formed ca. 40 ka and has since undergone periods of higher and lower flood regimes. Sediment analyses indicate that both dune and fan sands contain a diagenetic matrix of clay-enhanced amorphous silica (CEAS) which bonds weakly formed aggregates. The time of formation of diagenetic matrix products is inconclusive but may have been accelerated during or shortly after events dated using OSL/TL techniques. Hence earlier dune over-washing may have led to greater porewater of an acidic to near neutral nature which in turn promoted smectite formation and silicic acid precipitation > 100 000 years ago. The relatively abundant CEAS matrix in floodplain sands implies more recent semi-continuous flood events again of an acidic-near neutral nature leading to the formation of smectite. In this case the floodplain sediments are dated as having been deposited around 40 and 11 ka, when porewater content may have accelerated clay formation and silica dissolution. The dual nature of the CEAS in the islands reflects a changing environment from smectite-dominated flooding events to sepiolite-dominated desiccation events. Flooding may also correspond to TL/OSL ages over the past 40 000 years which contributed to accelerated CEAS formation. The sepiolite is associated with a Ca-rich matrix implying desiccation which may relate to drying events over the 40 000 year period or to riparian tree root pumping and selective salt accumulation. This work shows that sedimentation in incipient rifts is complex and rarely explained totally in terms of primary depositional events. The implications of different stages of sand diagenesis may be significant in enhancing palaeo-environmental interpretations in semi-arid fluvial environments.     

Deciphering the pulsations of G 29-38 with optical time series spectroscopy

We present optical time series spectroscopy of the pulsating white dwarf star G 29-38 taken at the Very Large Telescope (VLT). By measuring the variations in brightness, Doppler shift and line shape of each spectrum, we explore the physics of pulsation and measure the spherical degree (ℓ) of each stellar pulsation mode. We measure the physical motion of the g modes correlated with the brightness variations for three of the eight pulsation modes in this data set. The varying line shape reveals the spherical degree of the pulsations, an important quantity for properly modelling the interior of the star with asteroseismology. Performing fits to the Hβ, Hγ and Hδ lines, we quantify the changing shape of the line and compare them to models and previous time series spectroscopy of G 29-38. These VLT data confirm several ℓ identifications and add four new values, including an additional ℓ= 2 and a possible ℓ= 4. In total, from both sets of spectroscopy of G 29-38, eleven modes now have known spherical degrees.