cyanobacteria are confined to dewless habitats within a dew desert implications for past and future climate change for lithic microorganisms although covering almost all rock outcrops around the world little is known regarding the factors that govern the spatial distribution of lithic cyanobacteria and lichens this is also the case in the negev desert where cyanobacteria predominate on the rock outcrops of the south facing slopes and lichens on the rock outcrops of the north facing slopes hypothesizing that abiotic conditions determine their distribution radiation temperature rain dew and fog were monitored over a two year period 2008 2010 at cyanobacteria and lichen dwelling habitats within a first order drainage basin in the negev highlands while non significant differences characterized the rain amounts substantial differences in substrate temperatures were recorded which resulted in turn in fundamental differences in the non rainfall water regime while dew condensed at the rock outcrops of the lichen habitat no condensation took place at the cyanobacteria habitat contrary to the common belief cyanobacteria were found to inhabit dewless habitats as a result cyanobacteria solely rely on rain precipitation for growth and can therefore serve as bioindicators for dewless habitats within the dewy negev desert the findings may have important implications regarding earth colonization soil forming processes and geochemical processes following climate warming they may explain lichen expansion and subsequent o2 increase during the mid neoproterozoic providing indirect support for substantial photosynthetic activity and high weathering rates during this era

salt weathering simulations under hot desert conditions agents of enlightenment or perpetuators of preconceptions because of access difficulties and inhospitable environmental conditions our understanding of rock weathering in hot deserts has been strongly influenced by laboratory simulations however a risk exists that results may come to owe more to experimental design than to actual environmental conditions experienced at the atmosphere rock surface interface this was especially true in early salt weathering simulations that seemingly sought to reinforce the orthodoxy of a physically dominated weathering environment driven by extremely high absolute temperatures and large diurnal temperature ranges however improvements in environmental sensors over the last 20 years have established the complexity of desert climates and the importance of microclimatic controls and allowed considerable refinement of experimental design this overview evaluates the implications of recent simulation studies and presents new information on possible fatigue effects of differential thermal expansion of salts and the salt weathering of test blocks under compressive loading in doing so it demonstrates how physical rock properties change during experimentation the importance of short term surface temperature fluctuations distinctions between the weathering of unconfined debris and larger rock surfaces the importance of moisture and salt applications that replicate their availability in deserts the importance of rock thermal properties in controlling their weathering response in environments dominated by radiative heating and cooling and the overall complexity of weathering regimes

weathering of superficial limestone debris in a hot desert environment abstract weathering of superficial limestone debris is described from stone pavements on the hamada de meski in southeast morocco the dominant features are due to surface and subsurface solution mechanical weathering and aeolian action have only a limited effect microfeatures produced by solution include solution facetting microrills solution pits case hardening micropitting or vesicular weathering and possibly surface crazing such microforms are the most likely representatives of a truly arid karst

tree ring recorded hydroclimatic change in tienshan mountains during the past 500 years abstract in central asia tree rings provide one of the best sources of paleoclimatological information however dendroclimatology has not been widely applied in the coniferous forests of central asia tree cores of picea schrenkiana from four sites in the hutubi river basin were developed into a 606 year tree ring width chronology the analyses showed that the tree ring width indices highly correlate with mean april may pdsi in the hutubi river basin mean april may pdsi of the hutubi river was reconstructed using the tree ring data with 41 5 of the variance explained the reconstructed series contains both high and low frequency climate signals our new pdsi reconstruction agrees reasonably well with the dry and wet periods previously estimated from tree rings in western tien shan the results reveal common climatic extremes over much of central asia spatial analysis shows that the pdsi reconstructions have strong common signals for the tien shan the first principal component of pdsi reconstructions in tien shan is significantly correlated with sea surface temperature in the eastern equatorial pacific ocean and atlantic ocean the linkages to the atlantic and pacific oceans suggest the connection of regional moisture variations to the asian monsoon and the westerlies

drought reconstructions for the continental united states abstract the development of a 2 lat 3 long grid of summer drought reconstructions for the continental united states estimated from a dense network of annual tree ring chronologies is described the drought metric used is the palmer drought severity index pdsi the number of grid points is 154 and the reconstructions cover the common period 1700 1978 in producing this grid an automated gridpoint regression method called point by point regression was developed and tested in so doing a near optimal global solution was found for its implementation the reconstructions have been thoroughly tested for validity using pdsi data not used in regression modeling in general most of the gridpoint estimates of drought pass the verification tests used in addition the spatial features of drought in the united states have been faithfully recorded in the reconstructions even though the method of reconstruction is not explicitly spatial in its design the drought reconstructions show that the 1930s dust bow

hydroclimatic changes in china and surroundings during the medieval climate anomaly and little ice age spatial patterns and possible mechanisms abstract investigating hydroclimatic changes during key periods such as the medieval climate anomaly mca 1000 1300 ad and the little ice age lia 1400 1900 ad is of fundamental importance for quantifying the responses of precipitation to greenhouse gas induced warming on regional and global scales this study synthesizes the most up to date and comprehensive proxy moisture precipitation records during the past 1000 years in china and surroundings the proxy data collected include 34 records from arid central asia aca and 37 records from monsoonal asia our results demonstrate a pattern of generally coherent regional moisture variations during the mca and lia in mid latitude asia north of 30 n monsoonal northern china north china and northeast china was generally wetter while aca northwest china and central asia was generally drier during the mca than in the lia a west east mode the boundary between wetter northern china and drier aca was roughly consistent with the modern summer monsoon boundary in monsoonal china to the east of 105 e the northern part was generally wetter while the southern part was generally drier during the mca than in the lia a north south mode with a boundary roughly along the huai river at about 34 n these spatial patterns of moisture precipitation variations are also identified by instrumental data during the past 50 years in order to understand the possible mechanisms related to the moisture variations during the mca and lia we investigate the major sst and atmospheric modes e g the el nino southern oscillation enso the atlantic multidecadal oscillation amo and the north atlantic oscillation nao which affect the moisture precipitation variations in the study region using both the instrumental data and the reconstructed time series it is found that the enso may play an important role in determining hydroclimatic variability over china and surroundings on a multi centennial time scale and that the foregoing spatial patterns could be attributed to the la nina like el nino like condition during the mca lia in addition amo and nao may also have their own contributions

weathering and biokarst development on marine terraces northwest morocco weathering features are described from an arid coastal area in northern morocco which are indicative of invasive chasmolithic and endolithic microbial communities active weathering of marine terraces and karst development is associated with endolithic and epilithic algae responsible for boring disintegration of matrix and mineral fabrics solution and biomineralization that undermines the marine carbonate platform evidence of a range of biological weathering agents remains preserved speci cally calci ed laments and sporangial material an abundance of laments and spores representative of a consortium of algae fungi cyanobacteria and lichens is associated with the most denuded outcrops the array of microbes contributes to the formation of the stromatolites to depths of 0 5 m within the limestone substrate the preservation of stromatolites is supported by calci cation of spores and laments with trapping and binding of carbonate held in suspension by vadose waters the pervasive weathering on this sector of coastline has important practical implications for coastal planning and development authorities in morocco copyright 2003 john wiley sons ltd

rock weathering by the lichenlecidea auriculata in an arctic alpine environment scanning electron microscopy reveals that lecidea auriculata penetrates rock surfaces detaching incorporating and expelling flakes of rock measurements on an age sequence of moraine ridges illustrate changes in the extent and intensity of weathering over time a minimum rate of surface lowering 0 0012 mm a 1 is 25 to 50 times faster than weathering due to other processes in the same area the spatial pattern of weathering is influenced by the narrow ecological range of the species surface rocks on dry exposed sites are probably weathering much more rapidly than those in adjacent damp hollows and beneath snowpatches

image processing and roughness analysis of exposed bedrock fault planes as a tool for paleoseismological analysis results from the campo felice fault central apennines italy abstract morphologic investigations along the campo felice cf fault central apennines italy have been made in order to develop a procedure for the paleoseismological analysis of bedrock fault scarps the cf fault has been responsible for the formation of an impressive limestone fault scarp geomorphologic work on the cf basin and related fault indicated that the scarp originated from tectonic fault displacements three morphologic units have been distinguished along the fault scarp and defined as morphosome m1 lowest part of the scarp m2 and m3 the uppermost part these units display different karstic features which are the result of their different duration of exposure to weathering micromorphologic analyses focused on the morphosome m1 along which the cf fault plane is exposed for a height ranging between 4 and 7 m these analyses were aimed at defining differently weathered bands located at various heights and parallel to the fault scarp top and base the presence of these bands suggests repeated fault movements the exposed fault surface displays a low grade biokarstic weathering due to the action of epilithic and endolithic organisms the biokarst distribution is however inhomogeneous and conditioned by the presence of nourishing elements moisture and by light intensity an area preferentially affected by the biokarstic processes develops as a band at the bedrock soil contact at the base of the scarp roughness and colour analyses were made to identify uplifted bands which previously formed at the bedrock soil contact the roughness analysis was made using a microroughness meter along 20 cm long horizontal transects repeated each 20 cm of fault height for the entire morphosome m1 at various sites along the scarp the roughness variance data plotted vs the fault height failed to identify differently weathered bands of paleoseismological interest this result is probably due to the complex distribution of biokarst along the investigated fault plane more reliable results have been obtained by areal analysis of the variation of the colour rendering of the rocks exposed along the fault plane at different sites photographic images of large portions of fault surfaces have been processed with standard graphic computer programs the variations of colour indicated the presence of bands at various heights along the fault plane two uplifted bands have been recognised at all the investigated sites suggesting two displacement events e1 and e2 a preliminary chronological framework for these two events the youngest of which affected the cf fault can be derived from the paleoseismological data available for the southernmost branch of the regional fault system that includes the cf fault according to these data e1 may have occurred between 860 and 1300 ad while e2 may have occurred at about 1900 bc work is in progress to define surface exposure ages of different parts of the fault plane by means of in situ produced cosmogenic 36 cl this procedure will give further chronological constraints for the age of e1 and e2 and will also permit to test the validity of the micromorphologic analysis of bedrock fault scarps for paleoseismological aims

a 189 year tree ring record of drought for the dzungarian alatau arid central asia abstract mountain systems are the most important sources of water in arid central asia aca it is therefore essential to understand past cycles of droughts and pluvials and to explore how future cycles might influence the sustainable utilization of regional water resources the palmer drought severity index pdsi is a widely applied measure of dryness that can be reconstructed from tree rings here a schrenk spruce picea schrenkiana fisch et mey tree ring chronology was developed for the dzungarian alatau of aca correlation and response analysis indicated that the pdsi from previous july to current june was the principal factor limiting radial growth the chronology was used to reconstruct the pdsi of the past 189 years for the dzungarian alatau a calibration model for the period from 1950 to 2011 explains 42 6 or 41 7 after adjusting for the loss of degrees of freedom of the actual pdsi variance the reconstructed pdsi might be representative of drought conditions for most of aca because it captures severe drought events in the 1910s and 1940s that were widespread across aca the extreme drought years 1917 and 1945 are especially pronounced a decadal analysis shows that the five periods in which the pdsi trend increased were 1830 1840s 1880 1890s 1920 1930s 1950 1960s 1980 2000s the pdsi declined in the 1850 1870s the 1900 1910s the 1940s and the 1970s the pdsi in aca exhibited a notably long and rapid wetting from 1980 to 2005 but decreased after 2005 in fact there have been three especially dry years 2008 2014 and 2015 in the last 10 years meanwhile there was large power in the 2 1 year 2 9 year 4 1 year 5 5 year 9 5 year and 10 8 year short periods and in the 30 40 year long periods

reconstructed precipitation on a centennial timescale from tree rings in the western tien shan mountains central asia july june precipitation has been reconstructed to 1756 ad for the western tien shan mountains central asia using the picea schrenkiana tree ring width the reconstruction explains 31 of the variation in the observed precipitation from 1933 to 2009 some extremely dry signals in the historical documents are captured precisely in this new reconstruction wet periods occurred during the periods of 1811 1828 1843 1880 1893 1915 1929 1934 and 1983 2002 while the periods 1766 1810 1829 1842 1881 1892 1916 1928 and 1935 1982 were relatively dry power spectral and wavelet analyses demonstrated the existence of significant 32 17 and 2 6 7 4 year cycles of variability an assessment of spatial correlation analysis and the significant correlation coefficients between the reconstructed precipitation series and three precipitation reconstructions indicate that our reconstruction might contain multiple large scale climatic signals in the low frequency domain a wetting trend in the eastern central asia since the 1970s decades was also captured by this reconstruction

blue green algae and terrestrial limestone weathering on aldabra atoll an s e m and light microscope study blue green algae have been observed to affect limestone weathering on aldabra atoll indian ocean three different habitats can be identified on the rock surface i e epilithic chasmolithic and endolithic algae in each habitat may affect weathering in various ways samples of blue green algae and rock were taken from various terrestrial and coastal environments on aldabra atoll samples of limestone tablets and calcite crystals after one year in situ were also studied light and s e m microscopy revealed that endolithic boreholes were present on many samples especially those from frequently wetted sites to a maximum depth of 800 m an altered zone of micrite and algal filaments was also discovered in many samples from morphological and petrographical evidence blue green algal influences on weathering on aldabra atoll seem to be very complex and cannot easily be related to small scale landforms

westerlies asia and monsoonal asia spatiotemporal differences in climate change and possible mechanisms on decadal to sub orbital timescales abstract the westerlies dominated climatic regime wdcr in the present interglacial period was proposed because precipitation moisture variations between arid central asia and mid latitude monsoonal asia are out of phase or anti phased on different timescales during the holocene in this study we first review the development of the theoretical framework of the wdcr and then outline the boundary of its core area from the caspian sea in the west to the western hexi corridor in the east with the northern and southern limits coinciding with the domain of arid central asia next we present a synthesis of multiple lines of evidence for the occurrence of the wdcr on multi millennial sub orbital herein to decadal timescales during the holocene finally we examine the possible physical mechanisms responsible for the wdcr we find that external factors insolation changes induced by orbital factors generated the wdcr on a sub orbital timescale whereas a circum global teleconnection silk road pattern was the most significant factor responsible for the wdcr on centennial and decadal timescales the study provides a comprehensive summary of the development of our knowledge of the wdcr over the past several decades together with a tentative theoretical framework for understanding climatic and environmental changes within its region of influence in addition it forms a scientific basis for environmental management and ecological restoration in this arid region in the context of global warming

runoff variations in lake balkhash basin central asia 1779 2015 inferred from tree rings long highly resolved proxies for runoff are in high demand for hydrological forecasts and water management in arid central asia an accurate r2 0 53 reconstruction of october september discharge of the ili river in kazakhstan 1779 2015 is developed from moisture sensitive tree rings of spruce sampled in the tian shan mountains the fivefold extension of the gauged discharge record represents the variability of runoff in the lake balkhash basin for the last 235 years the reconstruction shows a 40 year long interval of low discharge preceded a recent high peak in the first decade of the 2000s followed by a decline to more recent levels of discharge not seen since the start of the gauged record most reconstructed flow extremes 2 occur outside the instrumental record 1936 2015 and predate the start of large dam construction 1969 decadal variability of the ili discharge corresponds well with hydrological records of other eurasian internal drainages modeled with tree rings spectral analysis identifies variance peaks highest near 42 year consistent with main hemispheric oscillations of the eurasian climatic system seasonal comparison of the ili discharge with sea level pressure and geopotential height data suggests periods of high flow likely result from the increased contribution of snow to runoff associated with the interaction of arctic air circulation with the siberian high pressure system and north atlantic oscillation

hydrometeorological reconstructions for northeastern mongolia derived from tree rings 1651 1995 reconstructions of annual prior august current july precipitation and streamflow 345 yr in length 1651 1995 are presented for northeastern mongolia based on tree ring width data these precipitation and streamflow reconstructions account for 54 and 48 of the respective variance in instrumental data over the past 50 years variations in instrumental precipitation and streamflow are within the range of those reconstructed over the length of tree ring records however there appear to be more frequent extended wet periods during the twentieth century multitaper spectral analysis revealed statistically significant peaks at 10 8 and 12 8 yr for the precipitation reconstruction and at 12 8 and 20 3 23 8 yr for the streamflow reconstruction similarly singular spectrum analysis identified spectral modes of variation at 12 and 21 yr for both series these spectra resemble those found for tree ring based precipitation reconstructions in central china as well as the western united states and may reflect solar influences on the climate of mongolia

a quantitative scanning electron microscope study of evidence for lichen weathering of limestone mendip hills somerset many saxicolous lichens may cause physical and chemical weathering of limestone substrates but their geomorphological importance has not been fully determined a simple method of producing quantitative descriptions of lichen material and petrographic evidence of weathering using the sem has been developed and tested on samples from the mendip hills england the technique reveals a variable and often sparse distribution of lichen material and associated weathering effects below a thin clearly defined lichen thallus

surface temperature differences between minerals in crystalline rocks implications for granular disaggregation of granites through thermal fatigue thermal expansion differences between minerals within rocks under insolation have previously been assumed to drive breakdown by means of granular disaggregation however there have been no definitive demonstrations of the efficacy of this weathering mechanism different surface temperatures between minerals should magnify thermal expansion differences and thus subject adjacent minerals to repeated stresses that might cause breakdown through fatigue failure this work confirms the existence of surface temperature differences between minerals in granitic rocks under simulated short term temperature fluctuations so as to discriminate their potential for initiating granular disaggregation the influence of colour as a surrogate for albedo and crystal size as a function of thermal mass are specifically identified because of their ease of quantification four rock types with a range of these properties were examined and subjected to repeated short term temperature cycles by radiative heating and cooling under laboratory conditions results show that while albedo is the main control for overall and individual maximum temperatures crystal size is the main factor controlling higher temperature differences between minerals thus stones with large differences of mineral sizes can undergo magnified stresses due to thermal expansion differences

ecological perspectives on rock surface weathering towards a conceptual model a wide range of information is now available on the ecology of rock surface microorganisms including bacteria fungi and algae and lichens and their role in weathering in particular locations external environmental conditions as well as rock characteristics determine the type of rock surface community and thus the style of biological weathering a simple preliminary conceptual model can be drawn which relates biological weathering activity to an environmental stress gradient and which is applicable at a range of scales further research needs carrying out to test and extend this model in order to make some progress towards the important goal of assessing the overall importance of biological weathering to geomorphology

pdsi variations at kongtong mountain china inferred from a 283 year pinus tabulaeformis ring width chronology 1 pinus tabulaeformis ring widths were used to reconstruct mean palmer drought severity indices pdsis from may to july for each of the past 283 years for kongtong mountain china a calibration model for the period from 1940 to 2005 explains 66 4 or 65 9 after adjusting for the loss of the degrees of freedom of the actual pdsi variance the reconstructed kongtong mountain pdsis could be representative of the moisture conditions of the entire loess plateau the reconstruction captures a severe 1927 1930 drought event that was widespread across all of northern china after 11 year moving average the reconstructed kongtong pdsi was found to compare well with other tree ring based temperature reconstructions from both huanglong in the eastern part of the chinese loess plateau and hokkaido japan this result indicates that high temperatures may be a major contributor to the severity of dryness at low frequencies significant 93 33 year and approximate 2 year cycles were observed in the kongtong tree ring chronology

a note on the role of the lichen collema auriforma in solution basin development on a carboniferous limestone substrate a study carried out on carboniferous limestone in the north and west of ireland supports the idea that rock substrate is removed by the direct mechanical action of lichens an experiment in which the lichen collema auriforma was subjected to a number of wetting drying cycles showed using scanning electron microscopy that contraction of the lichen thallus during the drying phase plucked rock fragments from the substrate surface this process could contribute to the formation of karstic features including solution basins

a tree ring based record of annual mass balance changes for the ts tuyuksuyskiy glacier and its linkages to climate change in the tianshan mountains abstract fluctuations in glacier mass and volume are indicative of changes in the climate system they also strongly affect regional climate and hydrology in this paper we explore possible relationships between the radial growth of schrenk spruce picea schrenkiana fisch et mey and the mass balance of the tsentralniy tuyuksuyskiy ts tuyuksuyskiy glacier which is located on the northern slopes of the tianshan mountains in arid central asia we attempt to reconstruct the historical mass balance variability of the ts tuyuksuyskiy glacier using tree ring widths and stable carbon isotope chronologies the reconstruction is able to explain 62 1 of the variance in the annual glacier mass balance record over the 1965 2014 calibration period we also analyzed centennial mass balance variability and its linkages to climate change the ts tuyuksuyskiy glacier has a negative annual mass balance in most years and since 1968 has undergone the most rapid and longest melting process in the past 166 years the mass balance change of the glacier is controlled by the combination of temperature and precipitation conditions this study could be useful for more detailed glaciological hydrological and climatological assessments in this portion of the tianshan mountains

the weathering effects of the lichen lecidea aff sarcogynoides koerb on magaliesberg quartzite the effect of the weathering processes generated by lecidea aff sarcogynoides koerb on the substrate was studied by means of a scanning electron microscope the elements present in the substrate magaliesberg quartzite and in the lichen thallus were determined by x ray fluorescence spectrometry for the purpose of comparison the elements present were mostly similar although a few were present in the thallus which were not observed in the quartzite it is possible that those elements present in the lichen thallus which were not present in the substrate may have been extracted from the atmosphere the occurrence of small hollows weathering pits in which the early stages of plant development occurs and the disintegration of the rock indicate that lecidea aff sarcogynoides koerb contributes to the chemical weathering processes by chelation and mechanically by the penetration and expansion of hyphae a model is proposed in which a possible mechanism for these weathering processes is suggested

rapid salt weathering in the coastal namib desert implications for landscape development data on the rate and style of breakdown on naturally occurring rock types are important to improving geomorphological understanding of landscape development in arid environments two years exposure of rock blocks cut from an english limestone bath stone as well as locally relevant namibian rocks karibib marble and damara granite within four distinctive microenvironments in and around a coastal salt pan environment reveals high rates of breakdown in the bath stone blocks observable breakdown in the marble blocks and weight gains and strength increases in the granite blocks breakdown is associated with high conductivities and large amounts of halite and gypsum within the surface sediments frequency of wetting and drying appears to be a major control on the resultant breakdown rates these findings can be compared with recent data from further inland in the namib desert which suggest very slow rates of breakdown of similar blocks of damara granite and karibib marble even where salts are readily available high rates of rock breakdown within coastal salt pans appear to contribute to dust production and the effective flattening of relief along the coastal strip

increased eurasian tropical temperature amplitude difference in recent centuries implications for the asian monsoon 1 a warmer eurasian continent and stronger land sea temperature gradient between eurasia and the tropical oceans contribute to an intensified summer monsoon we evaluate changes in the temperature difference between eurasia and the tropics over 250 years using proxies of eurasian surface air temperatures tree rings and tropical sea surface temperatures indo pacific corals these records show low frequency correspondence with each other over this interval and with other temperature and precipitation sensitive proxies from the asian monsoon regime greater warming is estimated for eurasia amplitude 1 70 0 28 c 1801 20 vs 1976 95 relative to the tropics 0 61 0 29 c 1806 25 vs 1937 56 the amplitude change from the 18th to 20th centuries is thus estimated to be about three times 1 5 6 greater over eurasia than the tropics this change may have contributed to an intensified asian monsoon system over recent centuries and to a decoupling of the monsoon and el nino southern oscillation in recent decades

tree ring based drought reconstruction for the central tien shan area in northwest china 1 a robust ring width chronology developed from two sites of picea schrenkiana in the central tien shan area of northwest china was employed to study regional drought variability our analyses demonstrate both temperature and precipitation have significant effects on tree growth thus both should be considered for climate reconstruction regional drought history 1675 2002 a d was therefore reconstructed by calibrating with the palmer drought severity index pdsi our reconstruction not only captured well those extreme drought events recorded in local historical archives but also revealed the long term pattern of drought variability especially the trend of increasing moisture during the 20th century multi taper method spectral analysis indicates the existence of some low and high frequency cycles 146 171 11 5 10 6 9 7 6 1 3 9 3 4 3 2 2 4 and 2 1 yr overall our study indicates the feasibility of combining tree rings and the pdsi to reconstruct large scale drought patterns over this area

tree ring based drought reconstruction at the northwestern margin of monsoon region of china since 1862 a tree ring width chronology developed from three sites of pinus tabulaeformis at the northwestern margin of the monsoon region of china was employed to study regional drought variability the drought reconstruction spanning 1862 2007 was developed by calibrating tree ring data with the palmer drought severity index pdsi an index indicating regional moisture conditions the reconstruction accounted for 43 3 of actual pdsi variance during their common period 1948 2005 droughts lasting over four years were found in 1877 1885 1889 1893 1925 1932 and 2004 2007 among which the droughts epochs in 1877 1885 and 1925 1932 were the two most severe and long lasting in the study area since 1862 there was an aridity aggravation trend since the mid 1970s in the reconstructed series which was consistent with the global temperature rise in records since 1975 this study indicated the feasibility of combining tree rings and the pdsi to reconstruct large scale drought patterns over this area and the pdsi reconstructed by tree ring may be a good proxy for the adjacent desert evolution

volcanic hotspots of the central and southern andes as seen from space by aster and modvolc between the years 2000 and 2010

limestone weathering in contemporary arid environments a case study from southern tunisia weathering features are described from a meteorologically arid area in southern tunisia active weathering is concentrated in topographic lows pits and pans that concentrate available moisture and are associated with endolithic and epilithic algae responsible for algal boring plucking and etching of the limestone substrate deposits of gypsum have concentrated through evaporation within hollows and occur as isolated patches of tabular crystals indicating an additional weathering agent characteristic of arid environments the active development of a complex microkarst and associated salt weathering are combining to destroy linear karstic features such as rillenkarren widespread case hardening and in places patches of iron and manganese rich rock varnishes the complexity of active and inherited weathering features belies the perceived simplicity and lack of weathering opportunities associated with aridity instead it focuses on the need to consider the nature of microclimatic conditions at the rock air interface especially when seeking to define desert weathering environments it also highlights the difficulties of interpreting polygenetic landforms and the importance of microscale studies for identifying the impact of contemporary climatic conditions

seismic slip history of the pizzalto fault central apennines italy using in situ produced 36cl cosmic ray exposure dating and rare earth element concentrations morphological and geological observations reveal that most apenninic faults are highly segmented and that the majority of the fault segments are less than 10 km long although these faults have undergone numerous paleoseismological investigations quantitative data remain crucially lacking for a large number of fault segments because such data are essential to understanding how these faults have ruptured and interacted in the past and how they might behave in the future we investigated the holocene seismic history of the pizzalto normal fault a 13 km long fault segment belonging to the pizzalto rotella aremogna fault system in the apennines we collected 44 samples from the pizzalto fault plane exhumed during the holocene and analyzed the 36cl and rare earth element ree contents together the 36cl and ree concentrations show that at least six events have exhumed 4 4 m of the fault scarp between 3 and 1 ka with slip per event values ranging from 0 3 to 1 2 m no major events have been detected over the last 1 kyr the rotella aremogna pizzalto fault system has a clustered earthquake behavior with a mean recurrence time of 1 2 kyr and a low to moderate probability ranging from 4 to 26 of earthquake occurrence over the next 50 years

endolithic microorganisms in the antarctic cold desert in the frigid desert of the antarctic dry valleys there are no visible life forms on the surface of the soil or rocks yet in certain rock types a narrow subsurface zone has a favorable microclimate and is colonized by microorganisms dominant are lichens of unusual organization they survive not by physiological adaptation to lower temperatures but by changing their mode of growth being able to grow between the crystals of porous rocks their activity results in mobilization of iron compounds and in rock weatherning with a characteristic pattern of exfoliation this simple ecosystem lacks both higher consumers and predators

a tree ring based precipitation reconstruction for the baluntai region on the southern slope of the central tien shan mountains china since a d 1464 abstract july june precipitation has been reconstructed back to a d 1464 for the baluntai region on the southern slope of the central tien shan mountains china using the picea schrenkiana tree ring width the reconstruction explains the variance of 51 in the observed precipitation from 1959 to 2005 by employing a 21 year moving average to the reconstruction nine periods with above average reconstructed precipitation comprised 1474 1503 1550 1577 1588 1619 1658 1713 1790 1812 1833 1867 1890 1907 1923 1944 and 1988 1995 eight periods with below average reconstruction consisted of 1504 1549 1578 1587 1620 1657 1714 1789 1813 1832 1868 1889 1908 1922 and 1945 1987 the wet dry periods of the reconstructed precipitation correspond well with other reconstructions some droughts in the historical documents are also precisely captured in the reconstruction precipitation variations for the southern slope of the central tien shan mountains are roughly synchronous with that of the northern slope in the recent 300 year power spectral and wavelet analysis demonstrated the existence of significant 100 y 60 y 50 y 16 y 10 y and 2 y cycles of variability

limestone weathering in eastern australia part 2 surface micromorphology study results from long term microerosion meter mem studies indicate that microenvironments are characterized by different erosion rates a complementary study carried out on the same sites examines the microscale morphology in each environment optical and scanning electron microscopy were used to identify a range of features thought to reflect different processes under subaerial conditions micromorphology is dominated by biological weathering features owing to the presence of microflora sites permanently covered by soil or stream water have only dissolution etch features though stream sites may exhibit microfractures sites with periodic exposure exhibit both dissolution and biological etch features the natural environment is more accurately reflected by allowing some microflora colonization of mem sites rather than preventing colonization by artificial means

palaeoenvironmental change and glacier fluctuations in the high tian shan mountains during the last millennium based on sediments from lake ala kol kyrgyzstan abstract a suite of limnological proxies measured in clastic sediments of the glacier fed lake ala kol ne kyrgyzstan document palaeoenvironmental change and glacier fluctuations in the central tian shan over the last millennium rock magnetic and geochemical data provide supporting evidence for three glacier expansion episodes occurring in 1200 1400 ce 1500 1850 ce and 1900 1950 ce and glacier retreat periods during 1000 1200 ce and the intervening periods the maximal glacier extent as inferred from high lf si inc coh ca inc coh and low arm30 arm is recorded between 1500 and 1850 ce and corresponds to cold and wet conditions during the little ice age in the high central tian shan periods of glacier waxing and waning recorded at lake ala kol present a close correspondence to ice accumulation rate in the northern tibetan plateau suggesting that precipitation changes are the main driver of glacier fluctuations in central tian shan during the last millennium although temperature may have exerted a more complex influence on centennial timescales

methods for measuring rock surface weathering and erosion a critical review studies of rates processes and modes of rock surface and near surface deterioration and also hardening are central to rock weathering and building stone research conservation and management there is a need to measure and monitor weathering at the rock atmosphere interface to facilitate understanding of climatic environmental and lithological controls on the evolution and development of surface weathering features this paper reviews long established and recently developed field and laboratory methods used by geomorphologists to monitor and measure the impact of weathering and erosion on physical and mechanical properties of exposed rock surfaces and their immediate subsurface key advances are highlighted their application to multi scalar understanding and modelling of rock surface weathering in different contexts is discussed and potential future advances to provide new insights into rock weathering durability and materials conservation are identified in highlighting key advantages and disadvantages of a wide range of methods to the broader earth science community the paper aims to contribute to further innovative thinking across disciplines to develop new methods for measuring and monitoring rock weathering

use of tree rings as indicator for groundwater level drawdown caused by tunnel excavation in zhongliang mountains chongqing southwest china tunnel excavation causes geological hydrological environmental and social changes the effects of groundwater level changes caused by tunnelling on tree growth have been poorly understood dendrochronology was used to evaluate the impact of groundwater level drawdown on tree growth tree cores of masson pines were collected from the areas affected by tunnel construction in the zhongliang mountains of chongqing in south western china to study the effects of tunnel excavation on the growth rate of trees by comparing with tree cores collected from unaffected areas excavation and early operation of the first tunnel in the zhongliang mountains from 1968 to 1984 caused a groundwater table drawdown in both karst aquifer and non karst aquifer the lowered groundwater table significantly reduced the growth rate of pine trees and the low growth rate remained for 15 years the effect was experienced up to at least 1 km from the tunnel axis the decline in tree growth was higher in karst than in non karst areas though the effects on the trees of the karst areas were lagging the high precipitation in 1998 contributed to groundwater recovery after which the tree growth recovered moderately but not to the original level groundwater leakage of the recently excavated tunnels did not affect pine trees heavily probably because the pines had adapted to the new hydrogeological conditions and new strategies in tunnel inflow management were adopted in the recently excavated tunnels the use of tree growth rate as an indicator of groundwater table change in tunnelling areas offers a new option to study environmental impacts and the extent of tunnelling effects