Climate Proxy

Local-scale climate reconstruction in arid regions is challenging due to the scarcity of suitably preserved archives. While several well-studied climate proxy datasets exist for southeastern Arabia, including those preserved in speleothems, sedimentary deposits and paleosoils, and occasionally sediment cores collected for pollen analysis, snails have not yet been explored as a potential archive. This study investigates the potential of the terrestrial gastropod Zootecus insularis collected from geoarchaeological sections as new climate archive for arid environments. Isotope analysis was conducted on specimens from Holocene contexts in Oman to reconstruct long-term climate trends. Previously published water temperatures calculated from oxygen isotope data of Melanoides tuberculata, a freshwater gastropod species found in the same geoarchaeological sections as the terrestrial Zootecus shells, were interpolated to the age of the terrestrial snails, allowing for the recalculation of an oxygen isotope signal used to identify wet or dry periods. The resulting dataset showed a strong correlation with existing paleoclimate datasets from speleothems and paleolakes. Additionally, the δ 13 C values of Z. insularis indicated a significant shift towards more negative values over time, which probably suggests a transition from C4 grass-dominated vegetation to mixed C4/ C3 xerophilic vegetation. This integrated approach suggests that snails could provide a valuable new archive for paleoclimate studies in arid regions.

Climate warming and associated aridification have been forecasted for the Mediterranean Basin, which is considered a climate-change hot-spot. Such drying trends could affect the performance and growth of conifers in these drought-prone areas. We evaluate if radial growth and wood density constitute potential proxies of precipitation and drought in a Mediterranean conifer. Location Juniperus thurifera Iberian forests in northern and eastern Spain. We sampled ten stands encompassing the species' distribution area. We related several annually resolved tree-ring variables (earlywood and latewood width, maximum and minimum wood density) to climatic factors (temperature, precipitation, drought index) for the period 1951-2000. We analyzed the spatial and temporal patterns of those associations. Minimum wood density presented the strongest response to climate of all analyzed tree-ring variables. Higher values of the minimum wood density were related to drier spring conditions, particularly in the most xeric sites, confirming that a drought-induced reduction in the radial expansion of tracheids increases earlywood density. Minimum wood density is a biogeographically meaningful proxy of spring water availability and drought stress for Mediterranean conifers.

Climate warming and associated aridification have been forecasted for the Mediterranean Basin, which is considered a climate-change hot-spot. Such drying trends could affect the performance and growth of conifers in these drought-prone areas. We evaluate if radial growth and wood density constitute potential proxies of precipitation and drought in a Mediterranean conifer. Location Juniperus thurifera Iberian forests in northern and eastern Spain. Methods We sampled ten stands encompassing the species' distribution area. We related several annually resolved tree-ring variables (earlywood and latewood width, maximum and minimum wood density) to climatic factors (temperature, precipitation, drought index) for the period 1951-2000. We analyzed the spatial and temporal patterns of those associations. Results Minimum wood density presented the strongest response to climate of all analyzed tree-ring variables. Higher values of the minimum wood density were related to drier spring conditions, particularly in the most xeric sites, confirming that a drought-induced reduction in the radial expansion of tracheids increases earlywood density. Main conclusions Minimum wood density is a biogeographically meaningful proxy of spring water availability and drought stress for Mediterranean conifers.

Por último, destacar que los resultados obtenidos en este trabajo pueden ser muy útiles para entender las respuestas del crecimiento forestal al cambio climático, incluyendo en el mismo una mayor frecuencia y severidad de las sequías, pero también para adaptar las estrategias de gestión apropiadas de los bosques sometidos a un elevado estrés hídrico. La gestión de los bosques mediterráneos bajo condiciones más cálidas y secas debería focalizarse en los principales factores locales que modulan los efectos negativos de la sequía sobre el crecimiento de los bosques en lugares semiáridos y húmedos.

Por último, destacar que los resultados obtenidos en este trabajo pueden ser muy útiles para entender las respuestas del crecimiento forestal al cambio climático, incluyendo en el mismo una mayor frecuencia y severidad de las sequías, pero también para adaptar las estrategias de gestión apropiadas de los bosques sometidos a un elevado estrés hídrico. La gestión de los bosques mediterráneos bajo condiciones más cálidas y secas debería focalizarse en los principales factores locales que modulan los efectos negativos de la sequía sobre el crecimiento de los bosques en lugares semiáridos y húmedos.

Understanding past atmospheric dust variability is necessary to put modern atmospheric dust into historical context and assess the impacts of dust on the climate. In Asia, meteorological data of atmospheric dust is temporally limited, beginning only in the 1950s. High‐resolution ice cores provide the ideal archive for reconstructing preinstrumental atmospheric dust concentrations. Using a ~500 year (1477–1982 A.D.) annually resolved calcium (Ca) dust proxy from a Tibetan Plateau (TP) ice core, we demonstrate the lowest atmospheric dust concentrations in the past ~500 years during the latter twentieth century. Declines in late nineteenth to twentieth century Ca concentrations significantly correspond with regional zonal wind trends from two reanalysis models, suggesting that the Ca record provides a proxy for the westerlies. Twentieth century warming and attendant atmospheric pressure reductions over northern Asia have potentially reduced temperature/pressure gradients resulting in l...

Limoges et al. Arctic Fjord Diatoms and IP 25 antarctica var. borealis, and the pennate Fragilariopsis oceanica, Fossula arctica, and Fragilariopsis reginae-jahniae. This study documents that IP 25 is produced in Young Sound, and that the weak fingerprint of sea ice in the sediment appears to be primarily due to the limited sea-ice diatom biomass.

Limoges et al. Arctic Fjord Diatoms and IP 25 antarctica var. borealis, and the pennate Fragilariopsis oceanica, Fossula arctica, and Fragilariopsis reginae-jahniae. This study documents that IP 25 is produced in Young Sound, and that the weak fingerprint of sea ice in the sediment appears to be primarily due to the limited sea-ice diatom biomass.

Mountain conifers in the Great Basin of North America have provided some of the longest, continuous, and annually resolved paleoclimate records. Climate-growth relationships at the cellular level, which help understand wood formation processes that underlie dendroclimatic reconstructions, are at present largely unexplored in the Great Basin. We analyzed 42 trees located in the Snake Range (eastern Nevada, USA) at three sites along an elevation gradient. Sampled species included white fir (Abies concolor), Douglas fir (Pseudotsuga menziesii), limber pine (Pinus flexilis), bristlecone pine (Pinus longaeva), and Engelmann spruce (Picea engelmannii). Wood anatomical features were quantified for two consecutive years, 2011 and 2012. Lumen area, cell wall thickness, lumen diameter, and wall-to-cell ratio were measured for the total ring as well as for earlywood and latewood. Mean standardized tracheidograms highlighted differences between 2011 and 2012, in particular concerning lumen area and wall-to-cell ratio. Most annual variation was due to earlywood, rather than latewood. Anatomical parameters of limber pine, the only species that could be tested at both the montane and subalpine sites, varied with elevation. Principal component analysis showed that the main axis of variability was related to dimensional parameters (e.g. lumen area), which reflected differences in water availability.

• Do temperate conifers show mixed tree-ring width and density responses to climate? • We analyze width and density responses to climate in Pyrenean silver fir stands. • Minimum wood density negatively responded to spring precipitation. • Maximum wood density increased as summer temperature and sunshine duration did. • Droughts could reduce hydraulic conductivity and growth by affecting earlywood density.

The long-term radial growth responses to drought and climatic variability of less-studied species such as Abies borisii-regis (Mattf.) remain poorly understood. We tested the hypothesis that severe short-term drought conditions during summer months will impact the radial growth of A. borisii-regis (Mattf.) trees and such impact will have a more pronounced effect on latewood (LW) than earlywood (EW) width. Correlation analysis was employed to investigate the impact of climatic drivers (temperature, precipitation) and drought, using the Standardized Precipitation Evapotranspiration Index (SPEI) calculated at cumulative time scales (1-12 months), on EW, LW and tree-ring width (TRW) in A. borisii-regis (Mattf.) trees from SouthEastern Albania. We found that EW width was positively correlated with precipitation in July and previous September, while the LW width and TRW was enhanced by the current June-July precipitation. Previous autumn and current summer high temperatures constrained the radial growth in A. borisii-regis (Mattf.) trees, particularly the LW and TRW. All the tree-ring widths components showed the highest significant response to drought at short cumulative time scales (<4 months) mainly during July, August and September. The highest impact of drought was observed for the LW width. Under a future reduction of summer precipitation and temperature increase, the A. borisii-regis (Mattf.) may show a decrease in EW formation, causing a decline of radial growth, leading to a reduction in hydraulic conductivity and carbon uptake in these forests.

We lack information regarding the main factors driving growth responses to drought in tree species with different vulnerability against this stressor and considering sites with contrasting climatic conditions. In this paper, we identify the main drivers controlling growth response to a multi-scalar drought index (Standardized Precipitation Index, SPI) in eight tree species (Abies alba, Pinus halepensis, Quercus faginea, Pinus sylvestris, Quercus ilex, Pinus pinea, Pinus nigra, Juniperus thurifera). We sampled forests growing across a pronounced climatic gradient under Mediterranean conditions in northeastern Spain. To summarize the patterns of growth responses to drought, we used principal component analysis (PCA). To determine the main factors affecting growth responses to drought, correlation and regression analyses were carried out using a set of abiotic (climate, topography, soil type) and biotic (Normalized Difference Vegetation Index, Enhanced Vegetation Index, tree-ring width, diameter at breast height) predictors and the PCs loadings as response variables. The PCA analysis detected two patterns of growth responses to drought corresponding to xeric and mesic sites, respectively. The regression analyses indicated that growth responses to drought in xeric forests were mainly driven by the annual precipitation, while in mesic sites the annual water balance was the most important driver. The management of Mediterranean forests under the forecasted warmer and drier conditions should focus on the main local factors modulating the negative impacts of drought on tree growth in xeric and mesic sites. Keywords Dendrochronology Á Drought Á Iberian Peninsula Á Radial growth Á Standardized precipitation index Communicated by A. Weiskittel.

Understanding past atmospheric dust variability is necessary to put modern atmospheric dust into historical context and assess the impacts of dust on the climate. In Asia, meteorological data of atmospheric dust is temporally limited, beginning only in the 1950s. High‐resolution ice cores provide the ideal archive for reconstructing preinstrumental atmospheric dust concentrations. Using a ~500 year (1477–1982 A.D.) annually resolved calcium (Ca) dust proxy from a Tibetan Plateau (TP) ice core, we demonstrate the lowest atmospheric dust concentrations in the past ~500 years during the latter twentieth century. Declines in late nineteenth to twentieth century Ca concentrations significantly correspond with regional zonal wind trends from two reanalysis models, suggesting that the Ca record provides a proxy for the westerlies. Twentieth century warming and attendant atmospheric pressure reductions over northern Asia have potentially reduced temperature/pressure gradients resulting in l...

Understanding past atmospheric dust variability is necessary to put modern atmospheric dust into historical context and assess the impacts of dust on the climate. In Asia, meteorological data of atmospheric dust is temporally limited, beginning only in the 1950s. High-resolution ice cores provide the ideal archive for reconstructing preinstrumental atmospheric dust concentrations. Using a~500 year (1477-1982 A.D.) annually resolved calcium (Ca) dust proxy from a Tibetan Plateau (TP) ice core, we demonstrate the lowest atmospheric dust concentrations in the past~500 years during the latter twentieth century. Declines in late nineteenth to twentieth century Ca concentrations significantly correspond with regional zonal wind trends from two reanalysis models, suggesting that the Ca record provides a proxy for the westerlies. Twentieth century warming and attendant atmospheric pressure reductions over northern Asia have potentially reduced temperature/pressure gradients resulting in lower zonal wind velocities and associated dust entrainment/transport in the past 500 years over the TP.

Pinus brutia var. pityusa (Steven) Silba (Calabrian pine) is considered a vulnerable species because of reductions in its population sizes linked to habitat decline in recent decades. Global warming alongside the collateral modification of precipitation regimes may markedly affect the distribution ranges of this species. In this dendroecological study, we identified the most influential climatic factors affecting the radial growth of P. brutia on the northern and eastern coasts of the Black Sea among the northern refugia of this species. Chronologies from five sites located on the Crimea Peninsula and the Caucasian coast and exposed to varying climatic conditions were used in this analysis. The study of environmental factors controlling the growth of P. brutia trees in the coastal populations of Crimea and the Caucasus revealed that within the longitudinal transect, which encompasses a specific range of climatic conditions, correlations between climate and the growth of P. brutia under analogous orographic conditions are similar. Aridisation of the dry Crimean climate in 1981-2012 led to an increase in the tree growth response. In the same period, populations of P. brutia trees growing in the subtropical climate of the Black Sea coast exhibited a weakened growth response to the point of disappearance. The northern populations of P. brutia, which are at the climatic limit of the species' distribution, are exposed to a high risk of increasing climate aridisation. Our findings could provide useful information for further research on the effects of climate change on Black Sea coastal forest ecosystems.

X-ray densitometry has proven useful in dendroclimatic research on relatively fast growing, complacent trees in mesic climates. The best dendrochronological materials, however, come from semiarid-site conifers that grow very slowly, have missing rings, are extremely sensitive to climate, and attain advanced ages. This study presents the first evaluation of X-ray densitometry of Douglas-fir, ponderosa pine, and pinyon from four semiarid sites in the eastern San Juan River Basin (northwestern New Mexico and southwestern Colorado). The relationship of climate with intra-annual tree-ring anatomy is anlyzed. Moving slit X-ray densitometry definest earlywood and latewood zones, yielding eight data types for each annual ring: total ring width, earlywood and latewood width, mean ring density, mean earlywood and latewood density, and minimum earlywood and maximum latewood density. response functions using regional averages of monthly mean temperature and total precipitation indicate that climate may strongly influence all eight types of data, depending on species and site conditions. Low moisture stress (cooler, wetter climate) increases total ring width, earlywood and latewood width, and ring, latewood, and maximum latewood density. High moisture stress increases earlywood and minimum earlywood density. The climate response of the density parameters differs from that reported for conifers in more mesic environments, although selected density parameters from a relatively mesic southwestern site are strongly related to climate. Site selection has nevertheless proven to be an important factor in getting the most climatically sensitive densitometric data. This study demonstrates that densitometry is feasible with conifers from semiarid sites. The intra-annual width and density data derived can increase the climate information available from these dry-site trees and should lead to improved seasonal and annual reconstructions of paleoclimate. Practical constraints imposed by current X-ray densitometric techniques may be removed with promising new procedures such as surface image analysis of cell anatomy. Die Röntgendensitometrie hat sich bei dendroklimatologischen Untersuchungen mit relativ schnell wachsenden sog. "complacent" Bäumen auf Standorten mittlerer Feuchtigkeit und Nährstoffversorgung als brauchbar erwiesen. Das beste dendrochronologische Material stammt jedoch von Nadelbäumen auf semi-ariden Standorten, die sehr langsam wachsen, ausfallende Jahrringe aufweisen, extrem klimasensitiv sind und ein hohes Alter erreichen. Die vorliegende Arbeit stellt die röntgendensitometrische Auswertung von Douglasie, Ponderosa-Kiefer und Pinyon-Kiefer von vier semiariden Standorten im östlichen Becken des San Juan dar (nordwestliches New Mexico und südwestliches Colorado). Es wird die Beziehung zwischen dem Klima und der intra-annuellen Jahrringanatomie analysiert. Mit der Röntgendensitometrie werden Frühholzund Spätholzzonen festgelegt und acht Parameter pro Jahrring erhalten: Jahrringbreite, Frühholz-und Spätholzbreite, mittlere Jahrring-, Frühholz-und Spätholzdichte, sowie minimale Frühholzund maximale Spätholzdichte. Response-Funktionen mit Hilfe von regionalen Mittelwerten der monatlichen Mitteltemperaturen und Niederschlagssummen deuten an, daß das Klima sämtliche acht Parameter stark beeinflußt, jedoch in Abhängigkeit von Baumart und Standortsbedingungen. Kühle und feuchte Witterung führte zu einer Zunahme der Breite des gesamten Jahrringes und von Frühholz und Spätholz sowie der Jahrring-, Spätholz-und maximalen Spätholzdichte. Die Reaktion der Dichteparameter auf die Witterung unterscheidet sich von derjenigen, die für Nadelbäume aus einer feuchteren Umgebrung bekannt sind, obwohl ausgewählte Dichtemerkemale von einem relativ feuchten südwestlichen Standort stark mit dem Klima korreliert sind. Die Standortauswahl hat sich als ein wichtige Maßnahme erwiesen, um die in klimatischer Hinsicht sensitivsten densitometrischen Daten zu

This thesis is an investigation of climate effects on radial growth of red pine (Pinus resinosa Ait) in northern Ontario over multiple spatio-temporal scales. In the context of climate change, these investigations provide insight about species survival, growth and range shift potential. In this thesis I investigate these three aspects of red pine dynamics using tree-ring width (TRW) data from 54 sites across northern Ontario. I first identified leading edge populations (16 No.) of red pine using climate data in hierarchical cluster analysis (HCA). I used various combinations of climatic variables as predictors in HCA, and evaluated their performance based on the compactness of formed clusters. These analyses reveal that leading edge populations of red pine in northern Ontario can be determined using three monthly climatic variables: mean minimum temperature (Tmin), mean maximum temperature (Tmax) and climate moisture index (CMI). I performed correlation and response function analyses to identify climatic controls on growth in these leading edge red pine populations. My results show that the effect of seasonal climate during prior summer was significant for growth in leading edge populations. Specifically, growth response was positive to prior summer precipitation (Prec) and negative to prior summer Tmax. This combined effect suggests the potential role of drought in controlling red pine northern range limit. My results question the validity of studies that predict large scale range shift potential of red pine under warming scenarios. My growthclimate analyses for the remaining red pine populations reveal a complex growth response of red pine in northern Ontario. In general, I observed four main results: (i) red pine populations in northwestern Ontario are more sensitive to climate than populations in northeastern Ontario, (ii) the growth-limiting effect of Prec is more significant than Tmax, (iii) growthclimate iii relationships follow a longitudinal gradient, and (iv) a shift in climatic controls of red pine temperature during first half of the 20 th century to precipitation during recent decades. I also investigated age effects on red pine growthclimate relationships in an old-growth red pine forest at Wolf Lake Forest Reserve in northern Ontario. My analyses reveal that growth response to climate in young red pines is different from old red pines. Winter season Tmin positively influences growth in young red pine trees, whereas summer Prec (specifically July) positively influences growth in old red pine trees. I finally conclude that climate effects on red pine growth vary across space and time, and such variations must be considered in any decision-making process. iv AUTHOR'S DECLARATION I hereby declare that I am the sole author of this thesis. This is a true copy of the thesis, including any required final revisions, as accepted by my examiners. I understand that my thesis may be made electronically available to the public. v PREFACE This thesis was written in manuscript format with the intent of publishing individual chapters as original research papers in peer reviewed journals. I tried my best to avoid any redundancy. However, some repetition was unavoidable considering each chapter (Chapter 2-4) as an individual manuscript. For this thesis, I took the lead in conceptualizing research ideas, developing research design, conducting fieldwork, preparing samples, recording/collecting data, analyzing data and producing manuscripts, including figures, tables, appendices, for all chapters in this thesis. However, I could not have accomplished these milestones without highly valuable guidance and support from my research

Growth-climate relationships of trees are species-specific and can vary over space and time. Here, we study red pine (Pinus resinosa Ait.) by analyzing tree-ring width data from 37 sites across northern Ontario, Canada for the period 1901-2010. We performed response function and moving response function analyses using seasonal data of three climatic variables: precipitation, minimum temperature and maximum temperature. Our analyses show considerable spatial and temporal variability in red pine growth response to climate during the 20th century. In general, red pine growth responses to climate were more significant in northwestern Ontario than in northeastern Ontario. Overall, precipitation was the most significant predictor of red pine growth, with seasonal variations across sites. Unlike many other studies, we did not find any significant growth response to current year summer temperature. Instead, at many sites in northwestern Ontario, red pine had a significant negative growth response to prior summer temperatures. The results of canonical correspondence analysis show that red pine growth response to climate follows a longitudinal gradient. Temporal stability analyses revealed that growth-climate response of red pine at any site was not stable during the 20th century. We observed a general shift from significant growth response to seasonal temperature during the first half of the 20th century to significant growth response to seasonal (except for spring) precipitation during recent decades. The spatial and temporal variability of red pine growth response to climate detected in our study should be considered in future plans for forest management of this species and can also be used for better understanding forest ecological dynamics at the regional scale for conservation purposes.

RED PINE (PINUS RESINOSA AIT) DYNAMICS UNDER CHANGING CLIMATE IN NORTHERN ONTARIO, CANADA Muhammad Waseem Ashiq Advisor: Dr. Madhur Anand University of Guelph, 2015 Advisory Committee: Dr. Andrew. M. Gordon Dr. Roger Suffling This thesis is an investigation of climate effects on radial growth of red pine (Pinus resinosa Ait) in northern Ontario over multiple spatio-temporal scales. In the context of climate change, these investigations provide insight about species survival, growth and range shift potential. In this thesis I investigate these three aspects of red pine dynamics using tree-ring width (TRW) data from 54 sites across northern Ontario. I first identified leading edge populations (16 No.) of red pine using climate data in hierarchical cluster analysis (HCA). I used various combinations of climatic variables as predictors in HCA, and evaluated their performance based on the compactness of formed clusters. These analyses reveal that leading edge populations of red pine in n...

Growth-climate relationships of trees are species-specific and can vary over space and time. Here, we study red pine (Pinus resinosa Ait.) by analyzing tree-ring width data from 37 sites across northern Ontario, Canada for the period 1901-2010. We performed response function and moving response function analyses using seasonal data of three climatic variables: precipitation, minimum temperature and maximum temperature. Our analyses show considerable spatial and temporal variability in red pine growth response to climate during the 20th century. In general, red pine growth responses to climate were more significant in northwestern Ontario than in northeastern Ontario. Overall, precipitation was the most significant predictor of red pine growth, with seasonal variations across sites. Unlike many other studies, we did not find any significant growth response to current year summer temperature. Instead, at many sites in northwestern Ontario, red pine had a significant negative growth response to prior summer temperatures. The results of canonical correspondence analysis show that red pine growth response to climate follows a longitudinal gradient. Temporal stability analyses revealed that growth-climate response of red pine at any site was not stable during the 20th century. We observed a general shift from significant growth response to seasonal temperature during the first half of the 20th century to significant growth response to seasonal (except for spring) precipitation during recent decades. The spatial and temporal variability of red pine growth response to climate detected in our study should be considered in future plans for forest management of this species and can also be used for better understanding forest ecological dynamics at the regional scale for conservation purposes.

Developing long-term chronologies of tree-ring anatomical features to evaluate climatic relationships within species might serve as an annual proxy to explore and elucidate the climatic drivers affecting xylem differentiation. Pinus leucodermis response to climate was examined by analyzing vertical xylem resin ducts in wood growing at high elevation in the Apennines of peninsular Southern Italy. Early-and latewood tree-ring resin duct chronologies, spanning the 1804-2010 time period, were constructed. We analyzed the relationships between resin duct chronologies and climate over the last century using correlation and response function analyses. Overall, results showed that ring width and resin duct relationships differed between early-and latewood, which indicated conditions affecting growth were not associated with resin duct production. Results also revealed differential responses to climate between early-and latewood resin duct chronologies. A notable observation was a positive and stable relationship between latewood resin duct number chronology and July maximum temperature throughout the twentieth century. This result suggested resin ducts might be a suitable proxy to evaluate P. leucodermis response to climate in the study area.

Key Message Earlywood and latewood widths differently respond to the climate in boreal and Mediterranean Scots pine forests. The response is constrained by allometric relationships. Abstract Measurements of earlywood (EW) and latewood (LW) width can be used to assess how tree growth responds to the climate in different biomes. Through tree-ring analyses, we quantified and analysed EW and LW width in six Scots pine (Pinus sylvestris) forests situated in the boreal and Mediterranean biomes. We aimed to answer: (i) how coupled are EW and LW width in Scots pine boreal and Mediterranean European forests, and (ii) how do they respond to climate and atmospheric patterns. Using allometric approaches to assess the EW-LW coupling and correlations with climate variables and indices we found that EW and LW width in Scots pine responds to different climate variables depending on biome and site. We identified two groups of sites with slow-growing trees producing dense wood with more LW in boreal sites vs. fast-growing trees producing more conductive wood with a higher EW proportion in Mediterranean sites. In these sites, spring-to-summer drought was the main constraint of EW and LW production. In boreal sites, wet springs and warm summers improved EW and LW width, respectively. We also found a high coupling between EW and LW width in cold, dry Mediterranean sites. LW width was very responsive to climate and atmospheric patterns in warm, dry Mediterranean sites. The most consistent response to atmospheric patterns was a negative correlation between EW and the January North Atlantic Oscillation index in Mediterranean sites. Mediterranean Scots pine forests where LW width is not very dependent on EW width are potential sites for using LW variables as proxies of drought during the growing season.

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We inferred climate change through the Pleistocene-Holocene transition from δ 13 C and δD values of bat guano deposited from 14.5 to 6.5 ka (calendar ka) in Bat Cave, Grand Canyon, Arizona. The δ 13 C and δD values generally covaried, indicating that regional late Pleistocene climate was relatively cool and wet, and early Holocene climate gradually became warmer with increased summer precipitation until ca. 9 ka, at which time the onset of modern North American Monsoon-like conditions occurred. During the Younger Dryas event, δ 13 C values decreased, whereas δD values increased, indicating a cool and possibly drier period. We also observed a distinct isotopic anomaly during the 8.2 ka event, at which time both δ 13 C and δD values decreased. The δ 13 C values abruptly increased at 8.0 ka, suggesting a rapid change in atmospheric circulation and greater infl uence from convective storms originating from the south. Deposits of bat guano represent a largely untapped source of paleoenvironmental information that can provide continuous and long-term continental archives of environmental change.

X -ray densitometry has proven useful in dendroclimatic research on relatively fast growing, complacent trees in mesic climates. The best dendrochronological materials, however, come from semiarid -site conifers that grow very slowly, have missing rings, are extremely sensitive to climate, and attain advanced ages. This study presents the first evaluation of X -ray densitometry of Douglas -fir, ponderosa pine, and pinyon from four semiarid sites in the eastern San Juan River Basin (northwestern New Mexico and southwestern Colorado). The relationship of climate with intraannual tree -ring anatomy is anlyzed. Moving slit X -ray densitometry definest earlywood and latewood zones, yielding eight data types for each annual ring: total ring width, earlywood and latewood width, mean ring density, mean earlywood and latewood density, and minimum earlywood and maximum latewood density. response functions using regional averages of monthly mean temperature and total precipitation indicate tha...

Limoges et al. Arctic Fjord Diatoms and IP 25 antarctica var. borealis, and the pennate Fragilariopsis oceanica, Fossula arctica, and Fragilariopsis reginae-jahniae. This study documents that IP 25 is produced in Young Sound, and that the weak fingerprint of sea ice in the sediment appears to be primarily due to the limited sea-ice diatom biomass.

We inferred climate change through the Pleistocene-Holocene transition from δ 13 C and δD values of bat guano deposited from 14.5 to 6.5 ka (calendar ka) in Bat Cave, Grand Canyon, Arizona. The δ 13 C and δD values generally covaried, indicating that regional late Pleistocene climate was relatively cool and wet, and early Holocene climate gradually became warmer with increased summer precipitation until ca. 9 ka, at which time the onset of modern North American Monsoon-like conditions occurred. During the Younger Dryas event, δ 13 C values decreased, whereas δD values increased, indicating a cool and possibly drier period. We also observed a distinct isotopic anomaly during the 8.2 ka event, at which time both δ 13 C and δD values decreased. The δ 13 C values abruptly increased at 8.0 ka, suggesting a rapid change in atmospheric circulation and greater infl uence from convective storms originating from the south. Deposits of bat guano represent a largely untapped source of paleoenvironmental information that can provide continuous and long-term continental archives of environmental change.

s u m m a r y 18 O/ 16 O, D/H, tritium and carbon isotopes were analysed together with the main geochemical parameters of selected wells of groundwaters in the Emilia-Romagna region. The isotope data collected in a threeyear monitoring program of surface waters allowed a subdivision of the studied region within the main feeding areas of the Po and Apennine Rivers. The isotopic investigation demonstrated the existence of palaeowaters hosted in deep aquifers in the plains and their overexploitation, which induced land subsidence phenomena. Groundwater stable isotopes have been utilized as a proxy for temperature and have shown significant atmospheric temperature variations over the past 30,000 years.

Several models of the effects of silviculture, radial growth, and tree age on wood density have been developed, but they have rarely considered the roles of diverse seed origins and climate. We developed a model to test the effects of radial growth, tree age, climate, and seedsource origins on wood density in 21 diverse populations of jack pine in a common garden in Petawawa, Ontario, Canada over the last 24 years using a linear mixed-effects model. Although we found significant differences in wood density among diverse seed origins, there were no differences between seed origins having the same ring age and ring width, indicating an indirect effect on wood density of seed-source origin via radial growth. High variation in wood density among trees within the same population and between populations indicated high genetic control of wood density. The climate effect was significant on wood density in all populations, but smaller when radial growth was controlled. Climate effect did not differ significantly among populations. Precipitation in July negatively affected latewood density, whereas precipitation in May in the current year and September of the previous year negatively affected earlywood density. We concluded that a single model of jack pine wood density and radial growth could be used, either controlling for climate effects or not, as the relationship between wood density and radial growth is preserved among the diverse populations, and the climate effect controlling for radial growth in the model was only slight.

In contrast to most high elevation areas, plant growth at Mediterranean mountains is exposed to a summer drought period, which represents an additional climatic constraint to low temperatures. Although arboreal and shrubby conifers coexist at high altitudes, most dendroecological studies have focused on climatic responses of tree species, whereas those of shrubby species remain mostly unexplored. We built tree-ring width chronologies for two conifer species, a shrub (Juniperus sabina) and a tree (Pinus sylvestris), coexisting at three high-altitude localities of the Iberian System mountains, eastern Spain. We analyzed their climate-growth relationships for the period 1950-2009 using correlation analyses and multiple regressions. Coexisting species responded to year-to-year climatic variability in different ways. Radial growth in junipers and pines responded positively to April and May temperatures, respectively. Summer drought constrained growth in both cases, although its impact was stronger on junipers than on pines. Our findings suggest that junipers respond earlier than pines to spring temperatures due to their prostrate morphology which may enhance a fast warming of their cambial meristems after snowmelt. The higher dependence of J. sabina on summer rainfall as compared with co-occurring pines confirms that drought stress negatively impacts secondary growth in Mediterranean mountains. This sensitivity to water availability may be caused by the juniper shallow root systems, which mainly use superficial soil water. The climatic signal registered in J. sabina allows studying the response of other similar shrubby woody species growing in Mediterranean alpine areas to the ongoing climate warming, which could also reduce water availability.

Stable isotopes of faeces contain information related to the animals feeding ecology. The use of stable isotope values from subfossil faeces as a palaeoenvironmental indicator depends on how faithfully the animal records their local environment. Here we present insectivorous bat guano dC and dN values from a precipitation gradient across the southern United States and northern Mexico to compare with local vegetation and climate. We find dC values to be an excellent predictor of expected C4/CAM vegetation, indicating that the bats are non-selective in their diet. Moreover, we find bat guano d C values to be strongly correlated with summer precipitation amount and winter precipitation ratio. We also find evidence for a significant relationship with mean annual temperature. In general, we do not find dN values to be related to any parameters along the climatic gradient we examined. Additionally, we measured dC and dN values of bulk guano deposited annually from 1968 to 1987 in a varved...

Due to its advantages in terms of much longer cover period and less demanding measurements, wood anatomy of Picea obovata Ledeb. was offered as spatiotemporal proxy record for tracheid differentiation kinetics. In this study, external and internal regulation of earlywood-to-latewood transition and properties of latewood were considered. The values and interrelations between cell number, tree ring width, maximal and mean radial cell diameter, maximal cell wall thickness and position of the transition to thick-walled tracheids were investigated within site and along the altitudinal gradient. Correlations with moving 21-day climatic series were used to estimate high-resolutional external influences. Relationships between tree ring traits are spatially stable and close within one stage of differentiation and between cells production and expansion. Relationships between sites differ in upper and lower parts of the gradient. Most of traits respond to the primary limiting factors near summer solstice; however, maximal cell wall thickness responds positively to the temperatures at the +10°C threshold. Altitudinal anatomical patterns revealed interaction of intrinsic and external factors in the regulation of tracheid differentiation. Timing of climatic response highlighted role of photoperiod as a trigger in the earlywood-to-latewood transition, and crucial role of the growth season ending for latewood development.

We inferred climate change through the Pleistocene-Holocene transition from δ 13 C and δD values of bat guano deposited from 14.5 to 6.5 ka (calendar ka) in Bat Cave, Grand Canyon, Arizona. The δ 13 C and δD values generally covaried, indicating that regional late Pleistocene climate was relatively cool and wet, and early Holocene climate gradually became warmer with increased summer precipitation until ca. 9 ka, at which time the onset of modern North American Monsoon-like conditions occurred. During the Younger Dryas event, δ 13 C values decreased, whereas δD values increased, indicating a cool and possibly drier period. We also observed a distinct isotopic anomaly during the 8.2 ka event, at which time both δ 13 C and δD values decreased. The δ 13 C values abruptly increased at 8.0 ka, suggesting a rapid change in atmospheric circulation and greater infl uence from convective storms originating from the south. Deposits of bat guano represent a largely untapped source of paleoenvironmental information that can provide continuous and long-term continental archives of environmental change.

The inter- and intra-annual variability in radial growth reflects responses to climatic variability and water shortage, especially in areas subjected to seasonal drought. However, it is unknown how this variability is related to forest productivity, which can be assessed by measuring changes in canopy greenness and cover through remote sensing products as the Normalized Difference Vegetation Index (NDVI). We combine xylogenesis with measurements of inter-annual changes in seasonal wood production (earlywood width, adjusted latewood width) and NDVI to improve the understanding of climate and drought impacts on growth and forest productivity in a Pinus teocote stand located in northern Mexico. Cambial dynamics accelerated in March and a high production of radially enlarging and thickening tracheids were observed from April to October and from June to October, respectively. Tracheid maturation was very active in October when latewood production peaked. Wet conditions in winter-spring a...

In trees, wood anatomy is a more precise and informative measure of hydraulic responses to drought than radial growth. Tree populations located near the equatorial-range edge of their distribution (rear edge) are used to monitor responses to changes in hydroclimate; however, few studies have assessed the wood anatomy of these populations. We measured tracheid lumen diameter (LD) and cell wall thickness (CWT) in a rear-edge Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) population. We also evaluated the formation of intra-annual density fluctuations (IADFs), characterized by earlywood (EW) tracheids with narrow lumens. We expected that EW LD would be particularly sensitive to hydroclimate variability. We found that EW LD was directly related to precipitation during the previous year’s late winter and the current year’s spring. Wet conditions were associated with wider EW tracheids and improved growth. These correlations peaked when considering cumulative precipitation from Januar...

Research Highlights: This study emphasized the importance of multi-parameter analyses along ecological gradients for a more holistic understanding of the complex mechanism of tree-ring formation. Background and Objectives: The analysis of climatic signals from cell anatomical features measured along series of tree-rings provides mechanistic details on how environmental drivers rule tree-ring formation. However, the processes of cell development might not be independent, limiting the interpretation of the cell-based climatic signal. In this study, we investigated the variability, intercorrelations and climatic drivers of wood anatomical parameters, resulting from consequent cell developmental processes. Materials and Methods: The study was performed on thin cross-sections from wood cores sampled at ~1.3 m stem height from mature trees of Pinus sylvestris L. growing at five sampling sites along an ecological gradient from cold and wet to hot and dry within continental Southern Siberia...

An 86 cm thick sequence of bat guano layers in the Kolatarika Cave in Kurdistan province in the west of Iran was analysed. The sequence was radiocarbon dated and covers an age of approximately 4060 years. The results of geochemical data, statistical studies, along with the investigation, analysis and explanation of historical sources indicate the presence of warm and dry climate conditions between ca 2100 BC and 800 CE. These were contemporaneous with the occurrence of periods of drought and famine during the Achaemenid and Sassanid empires, and might have been was one of the causes of their 'collapse. The existence of humid climate conditions between 800 and 1450 AD was contemporaneous with the period of Medieval Climate Anomaly and the historically documented prosperity of farms and agriculture during the Seljuk dynasties, the Samanids, and the rise of rainfall and river floods during the period of the Abbasid caliphate. The presence of cold and humid climate conditions between ca 1600 and 1750 AD was consistent with the so-called Little Ice Age and the Maunder Minimum. After this period, the climate of this area changed to warm and dry which was contemporaneous with the occurrence of famine and subsequent droughts of the late Safavid and Qajar dynasties in Iran.

Leaves from 24 South African vegetation sites, including 3 Fynbos sites, exhibiting high levels of endemism, were assessed by both LMA (Leaf Margin Analysis) and CLAMP (Climate Leaf Multivariate Program) to determine the effect of endemism on these palaeoclimate proxies. We examined whether existing calibrations using either locally recorded climate data or globally gridded climate data are appropriate for South Africa, or whether new calibrations specific to the region provide more accurate results. The results suggest that calibrations using gridded data yield slightly cooler estimates using LMA when the percentage of entire margined species is over 25. Overall, however, the differences are small and both gridded and local climate station calibration data can be used with equal accuracy. Xeric sites differ from mesic sites regarding the relationship between leaf margin proportion (LMP) and MAT, but with the exception of Fynbos sites, the differences are small when the percentage of entire margined species is b 65. Fynbos sites plot up to 8°C cooler for a given leaf margin percentage (LMP) than do other sites. LMA was also sensitive to the number of taxa scored and in general should not be attempted on less than 15 leaf morphotypes per site. For CLAMP, the African non-Fynbos sites plotted within the parameters characterized by the existing PHYSG3BRC data set, indicating that they had a leaf physiognomic response to climate consistent with that of the rest of the world. However, the African non-Fynbos sites did fill a previously unoccupied void within that space, indicating the existence of a regional variance from the global pattern. This suggests that endemism per se does not prevent CLAMP from yielding reliable climate predictions. The inclusion of African non-Fynbos sites into the calibration improved the ability of CLAMP to predict Fynbos site climate, although this remained poor for non-coastal xeromorphic Fynbos vegetation. The addition of the African non-Fynbos vegetation did not degrade significantly the PHYSG3BRC calibration, particularly regarding key climatic variables such as enthalpy. Enthalpy appears to be a particularly robust variable with which to test climate model performance against CLAMP palaeoclimate predictions.

Key message Based on the first dendroclimatological analyses of the thermo-Mediterranean tree Pyrus bourgaeana, the positive relationship between the growth and climate (i.e., precipitation) has strengthened in recent decades. Abstract The combined effect of climate change and habitat destruction and fragmentation threatens many plant populations and even entire communities in Mediterranean ecosystems. The Iberian pear, Pyrus bourgaeana Decne, a characteristic species of Mediterranean ecosystems, is threatened by both habitat and climate changes. We ask whether and how the growth of mature P. bourgaeana in the thermo-Mediterranean zone (i.e., altitude \700 m) has been affected by long-term climate changes during the last century in a fragmented landscape. Dendrochronological methods were used to find growth-climate relationships. We made the first dendroclimatological analyses and constructed a first 103-year tree-ring chronology of this species. The tree-ring series revealed large growth variability. We found a clear, strong relationship between tree growth and climate, with annual precipitation being the most important climate factor enhancing radial growth. Our results also showed that warm autumns and winters positively affect growth. There was no temporal stability in the relationship between tree growth and climate. The most general trend was in the relationship between annual precipitation and tree growth: the decrease of rainfall in the last decades of the twentieth century was associated with a constant increase of the correlation coefficient. Water accumulated in the soil in autumn and winter proved to be a key factor augmenting tree growth in the following vegetation period. The climate-growth relationship in P. bourgaeana has strengthened in recent decades apparently due to decreased precipitation levels.

Key message Based on the first dendroclimatological analyses of the thermo-Mediterranean tree Pyrus bourgaeana, the positive relationship between the growth and climate (i.e., precipitation) has strengthened in recent decades. Abstract The combined effect of climate change and habitat destruction and fragmentation threatens many plant populations and even entire communities in Mediterranean ecosystems. The Iberian pear, Pyrus bourgaeana Decne, a characteristic species of Mediterranean ecosystems, is threatened by both habitat and climate changes. We ask whether and how the growth of mature P. bourgaeana in the thermo-Mediterranean zone (i.e., altitude \700 m) has been affected by long-term climate changes during the last century in a fragmented landscape. Dendrochronological methods were used to find growth-climate relationships. We made the first dendroclimatological analyses and constructed a first 103-year tree-ring chronology of this species. The tree-ring series revealed large growth variability. We found a clear, strong relationship between tree growth and climate, with annual precipitation being the most important climate factor enhancing radial growth. Our results also showed that warm autumns and winters positively affect growth. There was no temporal stability in the relationship between tree growth and climate. The most general trend was in the relationship between annual precipitation and tree growth: the decrease of rainfall in the last decades of the twentieth century was associated with a constant increase of the correlation coefficient. Water accumulated in the soil in autumn and winter proved to be a key factor augmenting tree growth in the following vegetation period. The climate-growth relationship in P. bourgaeana has strengthened in recent decades apparently due to decreased precipitation levels.

Few studies have attributed δ15N values of guano to a factor other than diet. A δ15N record obtained from a 1.5-m core of bat guano deposit from Zidită Cave (western Romania) provides a record of anthropogenic and climatic influence on the regional nitrogen pool. Nitrogen content is nearly constant (%N > 9) for over 1 m of the core, indicating limited diagenesis. The δ15N and δ13C time series are compared and the δ15N is also interpreted in light of previously published pollen assemblage from the same core. Using these comparisons the influence of anthropogenic activity and water availability is interpreted. Although some δ15N variation can be attributed to major changes in anthropogenic activities, additional variation implies an alternative control. The correlation between δ15N and δ13C values is significant (p < 0.01), but not strong, suggesting that both variables are influenced by water availability, known to be a primary control of δ13C values within C3 ecosystems. Drier periods indicated by higher δ13C values correspond with lower δ15N values and vice-versa for wetter conditions. The instrumental climate record (precipitation amount) for the past 50 years nearby the cave supports this relationship. From 1000 to 1800 CE, the δ15N values fluctuated between 11.5 and 14‰, then decreased in two abrupt steps, at 1800 and 1947 CE. The most significant decrease occurred after 1947 CE when values fell from 12.5 to below 7‰, suggesting the N-cycle transitioned towards a more conservative state. The correlations between δ15N and δ13C, and the instrumental precipitation record, along with the apparent negligible effect of diet on long term δ15N variation indicate that the δ15N values of guano can be used as an integrator of the local N-cycle.

The δ 13 C values of 23 unevenly spaced guano samples from a 17-cm long clay sediment profile in Gaura cu Muscă Cave (GM), in SW Romania, made it possible to preliminarily characterize the Medieval Warm Period summer hydroclimate regime. The beginning of the sequence (AD 990) was rather wet for more than a century, before becoming progressively drier. After a brief, yet distinct wet period around AD 1170, drier conditions, with a possible shift from C 3 to a mixed C 3 -dominated/C 4 type vegetation (2 ‰ lower δ 13 C values), prevailed for almost half a century before the climate became colder and wetter at the onset of the Little Ice Age, when bats left the cave. The guano-inferred wet and dry intervals from the GM Cave are mirrored by changes in the color and amount of clay accumulated in the cave. They also agree well with reconstructions based on pollen and charcoal from peat bogs and δ 13 C and δ 18 O on speleothems from other Romanian sites. Overall, these results indicate that the δ 13 C of bat guano can provide a sensitive record of the short term coupling between local/regional climate and the 30 plant-insect-bat-guano system. Bird MI, Boobyer EM, Bryant C, Lewis HA,

Geographically structured tree-ring networks are needed to fully understand the spatiotemporal variability in climatic sensitiveness of trees and to study their future responses to global warming. We aim to identify the spatially constrained structure of radial-growth patterns of the Spanish juniper (Juniperus thurifera L.) and to assess whether their climate-growth responses were unstable during the late twentieth century. Tree-ring width chronologies were built for 13 J. thurifera stands in Spain using dendrochronological methods and related to monthly climatic data. Sites were grouped according to their growth patterns using hierarchical cluster analysis. The relationships among geographical, climatic and stand features and their influence on radial growth were evaluated using redundancy analysis. The climate-growth relationships and their temporal stability were assessed using Pearson's and moving bootstrapped correlations, respectively. Stands formed three geographical groups according to their highfrequency growth variation: North West and Centre, North East and South East. We found that J. thurifera radialgrowth patterns depended on geographical and climatic factors, but not on the stand structure, and responded to a northwest-southeast gradient of decreasing rainfall and influence of Atlantic Westerlies and Mediterranean cyclonic activity. The positive response to June precipitation was unstable during the late twentieth century and started earlier in populations from western mesic sites than in eastern xeric sites. This pattern may be related to either decreasing water availability in western than in eastern sites or the resilience of J. thurifera growth from xeric sites in response to the increasing summer aridity.

We inferred climate change through the Pleistocene-Holocene transition from δ 13 C and δD values of bat guano deposited from 14.5 to 6.5 ka (calendar ka) in Bat Cave, Grand Canyon, Arizona. The δ 13 C and δD values generally covaried, indicating that regional late Pleistocene climate was relatively cool and wet, and early Holocene climate gradually became warmer with increased summer precipitation until ca. 9 ka, at which time the onset of modern North American Monsoon-like conditions occurred. During the Younger Dryas event, δ 13 C values decreased, whereas δD values increased, indicating a cool and possibly drier period. We also observed a distinct isotopic anomaly during the 8.2 ka event, at which time both δ 13 C and δD values decreased. The δ 13 C values abruptly increased at 8.0 ka, suggesting a rapid change in atmospheric circulation and greater infl uence from convective storms originating from the south. Deposits of bat guano represent a largely untapped source of paleoenvironmental information that can provide continuous and long-term continental archives of environmental change.