Interannual Growth Research Articles

Reprint of “Patterns of shallow seagrass (Posidonia oceanica) growth and flowering along the Tunisian coast”

Shoot density and temporal patterns in leaf and rhizome production and other flowering parameters were assessed using a reconstruction technique (Lepidochronology) in Tunisian Posidonia oceanica meadows. Three meadows were sampled in October 2005 while seven in October 2007. Correlation between lepidochronological parameters and climate data (temperature and rainfall) was investigated. Shoot density in the ten meadows varied from 388±42shootsm−2 at El Kantaoui to 893±109shootsm−2 at Rafraf and showing significant differences between all sites. The meadows growing on hard substrate (Rafraf, Nabeul, Hergla cliff, Mahdia and Djerba) exhibited the highest shoots densities. Annual leaf formation rate showed a statistically significant difference between localities and years, indicating the importance of interannual growth fluctuations. The meadow in Tabarka produced two more leaves per year (8.3±0.7) than Rafraf ones (6.3±0.7). Vertical rhizome elongation rates differed significantly among sites, ranging from higher rates in Tabarka (average 13.72±2.26mmyear−1) to lower rates in El Kantaoui (average 5.01±1.13mmyear−1). The correlation analysis between seagrass growth and climate records showed significant correction between mean rainfall data and vertical rhizome elongation rates. Flowering was most prevalent in 2003. The maximum flowering frequency (FF) and shoot flowering probability (Pf) values were observed in Tabarka. The mean FF and Pf for all studied meadows were respectively estimated to 0.15±0.09 and 0.011±0.009. A large spatial–temporal variation in the flowering frequency occurred among populations and between years in P. oceanica meadows along the Tunisian coast.

Contrasting responses of net primary productivity to inter-annual variability and changes of climate among three forest types in northern China

Aims A lack of explicit information on differential controls on net primary productivity (NPP) across regions and ecosystem types is largely responsible for uncertainties in global trajectories of terrestrial carbon balance with changing environment. The objectives of this study were to determine how NPP of different forest types would respond to inter-annual variability of climate and to examine the responses of NPP to future climate change scenarios across contrasting forest types in northern China. Methods We investigated inter-annual variations of NPP in relation to climate variability across three forest types in northern China, including a boreal forest dominated by Larix gmelinii Rupr., and two temper ate forests dominated by Pinus tabulaeformis Carr. and Quercus wutaishanica Mayr., respectively, and studied the responses of NPP in these forests to predicted changes in climate for the periods 2011–40, 2041–70 and 2070–100 under carbon emission scenar ios A2 and B2 of Intergovernmental Panel on Climate Change. We simulated the responses of NPP to predicted changes in future climate as well as inter-annual variability of the present climate with the Biome-BGC version 4.2 based on site- and species-specific parameters. The modeled forest NPP data were validated against values in literature for similar types of forests and compared with inter-annual growth variations reflected by tree-ring width index (RWI) at the study sites. Important Findings Inter-annual variations in modeled NPP during the period 1960–06 were mostly consistent with the temporal patterns in RWI. There were contrasting responses of modeled NPP among the three forest types to inter-annual variability of the present climate as well as to predicted changes in future climate. The modeled NPP was positively related to annual mean air temperature in the L. gmelinii forest (P < 0.001), but negatively in the P. tabulaeformis forest (P = 0.05) and the Q. wutaishanica forest (P = 0.03), while the relationships of modeled NPP with annual precipitation for the three forest types were all positive. Multiple stepwise regression analyses showed that temperature was a more important constraint of NPP than precipitation in the L. gmelinii forest, whereas precipitation appeared to be a prominent factor limiting the growth in P. tabulaeformis and Q. wutaishanica. Model simulations suggest marked, but differential increases in NPP across the three forest types with predicted changes in future climate.

Interannual growth differences and growth-selective survival in larvae and juveniles of marbled sole Pseudopleuronectes yokohamae

Flatfishes drastically change their habitat, body form, and feeding during metamorphosis; thus, the early juvenile and larval stages are viewed as being critical for early survival. However, to the best of our knowledge, no studies have tested the growth-mortality hypothesis for both larval and juvenile stages of flatfishes. Therefore, we investigated the relationship between growth rate and environmental factors and tested the hypothesis for both larval and juvenile stages of marbled sole Pseudopleuronectes yokohamae in Hakodate Bay, Japan from 2001 to 2003. For both larval and juvenile stages, otolith growth correlated with water temperature. Eye-migrating larvae were defined as survivors of planktonic life (SV pelagic ). Large juveniles captured in late June and July were defined as survivors of shrimp predation (SV juvenile ) . To test the growth-mortality hypothesis, otolith growth was compared between the SV and the original population. During the pelagic larval stage, growth-selective survival was not detected in any of the 3 yr. During the early juvenile stage, fast-growing individuals survived selectively in 2002 but not in 2003. In 2002, population growth of juveniles was slow because water temperatures were low. Thus, juveniles in 2002 required time to exceed the size spectrum that is vulnerable to shrimp predation; consequently, the individuals that grew more rapidly were able to survive selectively. Our results show the importance of the early juvenile stage for the survival of flatfishes.

Water Body Type Influences Climate–Growth Relationships of Freshwater Drum

AbstractClimate–growth relationships of fish are of increasing research interest. However, few studies have attempted to characterize the extent to which climate–growth relationships may diverge across fundamentally different types of environments. The goal of this study was to examine the effects of climate variability (i.e., temperature, precipitation, global climate indices) on the growth of Freshwater Drum Aplodinotus grunniens and determine the extent to which these relationships differ between lotic and lentic habitats. Freshwater Drum were collected from five river and five reservoir environments in Georgia, Alabama, and Mississippi. Tree‐ring techniques were used to standardize annual growth for age (measured using interannual growth increments from otolith sagittae) and growth indices were correlated to annual thermal, hydrologic, and global climate indices. Freshwater Drum expressed distinct and significant climate–growth relationships by water body type. The general pattern observed was that annual drum growth in rivers was significantly correlated to days of year of maximum flow while annual drum growth in reservoirs was significantly correlated to annual variation in number of growing degree‐days (GDD). Furthermore, the strength of growth–GDD correlations for drum increased predictably alongside hydraulic retention time of reservoirs. This study reveals that water body type can govern climate–growth relationships in fish and suggests biologists need to be wary of assuming that patterns documented in one population would be wholly applicable to another.

Temperature modulates intra-plant growth of Salix polaris from a high Arctic site (Svalbard)

Arctic ecosystems are important carbon sinks. Increasing temperatures in these regions might stimulate soil carbon release. Evidence suggests that deciduous shrubs might counteract these carbon losses because they positively respond to increasing temperature, but their role in ecosystem carbon budgets remains uncertain. Many studies dealing with large-scale tundra greening and carbon sequestration in relation to increasing temperature have usually based their estimations on the aboveground components, but very little is known about belowground growth. In this context, annual rings can provide a retrospective insight into intra-plant temperature responses and seasonal growth allocation. This study presents a 70-year-long and annually resolved intra-plant analysis of ring width and missing ring distribution from a comprehensive serial sectioning, including 142 cross-sections and the measurements of 471 radii from ten Salix polaris Wahlenb. dwarf shrubs growing in the high Arctic on Svalbard. Results indicate a high intra-plant and inter-annual growth variation, characterized by a high proportion of partially (13.6 %) and completely (11.2 %) missing rings. The annual growth and the frequency of completely missing rings were evenly distributed inside the plant and mainly controlled by summer temperatures. Radial growth in the belowground parts appeared to be proportionally higher during long and warm summers and lower in cold early growing seasons than in the aboveground parts. The results reveal a diverging allocation between aboveground and belowground growth depending on the climatic conditions. Favorable years promoted root allocation since root radial growth occurs after aboveground growth. The observed belowground responses suggest that shrub carbon allocation might be higher than estimated only from the aboveground compartments.

Impacts of Simulated N Deposition on Plants and Mycorrhizae from Spanish Semiarid Mediterranean Shrublands

Nitrogen (N) deposition threatens European Mediterranean ecosystems but investigation and understanding of impacts are limited. We report plant responses from an ongoing field N fertilization experiment conducted in a kermes oak shrubland, where NH4NO3 has been added for 1.5 years at four rates (0, 10, 20, and 50 kg N ha−1 y−1). Two annual plants (Asterolinon linum-stellatum and Limonium echiodes) were negatively affected by N fertilization in terms of density and growth. However, responses were only evident when accounting for between-plot differences in soil NO3 −-N and NH4 +-N. Responses of A. linum-stellatum to simulated N deposition were also dependent on microhabitat, with the most negative effects found in the interspaces between rosemary shrubs. Negative effects were attributed either to increased soil NH4 +-N or to a nutritional (N to P) imbalance. Mycorrhizal infection rates were not altered by N addition in the case of L. echioides, whereas mycorrhizal colonization of A. linum-stellatum roots increased with N in those individuals growing under shrub protection. Living cover of rosemary shrubs was also reduced by simulated N deposition as a consequence of a reduced interannual twig growth. Contrary to annual plants, tissue N content and C:N ratios in rosemary were not affected by simulated N deposition. Overall, our data suggest a high sensitivity of plant communities from moderately polluted semiarid Mediterranean shrublands to N deposition, highlight the role of different forms of inorganic N on plant response to N deposition, and support the importance of conducting similar experiments in other Mediterranean areas spanning a wide range of climatic, soil, and background N deposition conditions.

Environmental heterogeneity and neighbourhood interference modulate the individual response of Juniperus thurifera tree-ring growth to climate

Individual variation of tree-ring growth response to climate and heterogeneity of the local environment are usually neglected in dendrochronological research. Even if there is evidence showing that individual responsiveness to climate may depend on intrinsic traits such as tree age, size or sex, its modulation by the local heterogeneity of extrinsic factors has been less studied. Using an extensive, strictly regular sampling scheme across a 3300ha woodland, we assessed the individual variation of tree-ring growth responses to climate in 100 Juniperus thurifera L. trees. The climatic response was evaluated by bootstrapped correlations of both population- and individual-based tree-ring chronologies with monthly records of precipitation, cloudiness, minimum and maximum temperatures. We studied also the influence of extrinsic abiotic (elevation, slope, heat load, tree location) and biotic (competition from neighbouring trees) factors on the individual growth variation and its climatic response. At a population level, growth was controlled by February–March precipitation, April minimum temperature, and June water stress. A significant proportion of individuals did not respond to those variables, but were sensitive to others not relevant at the population level. Inter-annual growth variation was strongly modulated by competition, whereas trees under lower competition levels, in eastern and warmer areas, were the most responsive to climate. The individual climatic response was, at least partially, modulated by the local heterogeneity of extrinsic factors. By considering environmental heterogeneity and neighbourhood interference we can identify the spectrum of site-dependent climatic responses in a population, which in turn will enable more realistic predictions of tree responses to ongoing climate change.

Patterns of shallow seagrass (Posidonia oceanica) growth and flowering along the Tunisian coast

Shoot density and temporal patterns in leaf and rhizome production and other flowering parameters were assessed using a reconstruction technique (Lepidochronology) in Tunisian Posidonia oceanica meadows. Three meadows were sampled in October 2005 while seven in October 2007. Correlation between lepidochronological parameters and climate data (temperature and rainfall) was investigated. Shoot density in the ten meadows varied from 388±42shootsm−2 at El Kantaoui to 893±109shootsm−2 at Rafraf and showing significant differences between all sites. The meadows growing on hard substrate (Rafraf, Nabeul, Hergla cliff, Mahdia and Djerba) exhibited the highest shoots densities. Annual leaf formation rate showed a statistically significant difference between localities and years, indicating the importance of interannual growth fluctuations. The meadow in Tabarka produced two more leaves per year (8.3±0.7) than Rafraf ones (6.3±0.7). Vertical rhizome elongation rates differed significantly among sites, ranging from higher rates in Tabarka (average 13.72±2.26mmyear−1) to lower rates in El Kantaoui (average 5.01±1.13mmyear−1). The correlation analysis between seagrass growth and climate records showed significant correction between mean rainfall data and vertical rhizome elongation rates. Flowering was most prevalent in 2003. The maximum flowering frequency (FF) and shoot flowering probability (Pf) values were observed in Tabarka. The mean FF and Pf for all studied meadows were respectively estimated to 0.15±0.09 and 0.011±0.009. A large spatial–temporal variation in the flowering frequency occurred among populations and between years in P. oceanica meadows along the Tunisian coast.

Growth responses of West-Mediterranean Pinus nigra to climate change are modulated by competition and productivity: Past trends and future perspectives

Positive and negative effects of climate change on forest growth have been observed in different parts of the world. However, much is still unknown about how forest structure and productivity might affect climate–growth relationships in the future. We examined the effects of climate, site quality, and competition on tree basal area growth of black pine ( Pinus nigra Arn.) between 1964 and 2005 in 21 sites in the Iberian Peninsula. We used a new approach to simultaneously account for climate–growth relationships, inter-annual growth variability, and stand structural changes, by fitting a linear mixed effects model (LMEM) for basal area increments (BAI) using climate data, tree-ring chronologies, and repeated forest inventory data. This approach showed the potential to improve our understanding of climate effects on tree growth and to include climate in empirical forest growth models. We used the LMEM to make projections of BAI growth under two CO 2 emission scenarios and two global circulation models (GCM). The main climate drivers for growth were precipitation from previous autumn to summer and winter temperature with a positive effect, and temperature in spring–summer which had a negative effect. Tree response to climate was modulated by stand conditions, tree competition, and productivity. The more productive stands showed greater ability to either maintain or increase growth at warmer spring–summer temperatures under different levels of autumn–summer precipitation. Growth projections showed important regional differences. In general, growth under future climate is predicted to decrease although moderate growth increases might be expected in the northern region for highly and moderately productive stands.

¿Valen los medicamentos lo que cuestan?

Drugs constantly jeopardize the balance among Bioethical Principles governing Healthcare. Their correct use implies more than a correct clinical diagnosis and an academic prescription and demands thorough coordination among all healthcare levels (Regulatory Agencies, the State, the Pharmaceutical Industry and professionals) and the necessary incentive for the research and development process to provide true therapeutic innovations. The interannual growth of Pharmaceutical Expenditure in the public sector in the last few years has greatly exceeded growth in the consumer price index and the gross domestic product. The economic problem of drugs utilization therefore centers on their opportunity cost and on their impact on the sustainability of the system overall. Cost-utility, as an accepted principle for the incorporation and use of new technologies is not always taken into account in prioritization, decision-making and interventions.

Detection of high-wind events using tree-ring data

Windstorms are common events in midlatitude west coast climates yet little is known about their long-term history and influence on regional forests. In this paper, we present a procedure that detects the timing and frequency of these high-wind events (HWEs) along the Pacific Northwest coast of North America using crossdated tree-ring measurements and detrended tree-ring chronologies derived from windsnapped trees. Our results show that abrupt changes in ring width patterns closely match dates of known HWEs and can serve as a nonclimatic basis for crossdating. Experimentation with different growth suppression and release criteria revealed that either a 50% decrease or a 50% increase in radial growth relative to the mean index value provided the best criterion for detecting windstorm-related growth anomalies. Comparing these results with the known occurrence of windstorms during the past century successfully identified all known major wind events during the study period. Low correlations between tree growth and climatic variables further imply that HWEs are the principal cause of interannual growth variations. Accordingly, we discuss the application of our procedure toward the development of a multicentury reconstruction of HWEs, a long-term analysis of decadal climate variability and HWEs, and the ecological role of HWEs in Pacific Northwest and other west coast forests.

Climatic control of intra- and inter-annual wood-formation dynamics of Scots pine in northern Finland

Boreal forests are highly sensitive to climate and human impacts and therefore suitable as biological indicator for environmental changes. In this context, our study was aimed at getting deeper insight into the climate-dependence of the onset, intensity and end of wood formation of Scots pine during the growing season. We monitored the intra-annual growth dynamics of, on average, 42-year-old Scots pine trees over five consecutive years, 2000–2004, at two sites located 80 and 300 km south of the tree line in northern Finland. For that purpose, the cambium of the trees was weekly wounded with a pin and the resulting wound tissue, microscopically detectable in transverse thin-sections through the newly built wood, was taken as a time marker. During this 5-year study period, the intra-annual wood formation at the southern site was mainly positively associated with summer temperature. However, at the northern site such an association was either entirely missing or negative. At both sites, two thirds of the radial growth was produced within only 4 weeks from mid-June to mid-July, independent of whether the growing season started earlier or later. Moreover, we measured the widths of all tree rings from bark to pith (inter-annual growth) of the same study trees and assembled them to 51-year long tree-ring site chronologies. Since 1999, these two site chronologies – after having run fairly parallel over the preceding decades – were running in divergent directions thus corroborating our results derived from the intra-annual climate/growth analysis. Whereas the chronology of the southern site follows the average temperature of May and July very closely from 1961 up to 2004, the chronology of the northern site follows the July temperature, but only up to 1998, and from 1999 to 2004 is running just opposite to the distinctly rising July temperature. During the same period, there was – unlike in the years before – nearly no snow cover in May at the northern site, whereas at the southern site there was no change of the normally existing slight snow cover in May. This deviating weather situation may have led to a temperature-induced, temporary drought stress for the Scots pines at the northern site.

Impacts of drought and predicted effects of climate change on fish growth in temperate Australian lakes

AbstractClimate change is expected to negatively impact many freshwater environments due to reductions in stream‐flow and increases in temperature. These conditions, however, can already be found today in areas experiencing significant drought; current observations of species' responses to droughts can be used to make predictions about their future responses to climate change. Using otolith analysis, we recreated golden perch (Macquaria ambigua) growth chronologies from two temperate lake populations in southeastern Australia over a 15‐year period pre‐ and during a supraseasonal drought. We related interannual growth variation to landscape‐scale changes in temperature and hydrological regimes: fish growth declined as water levels in the lakes dropped during the drought, but this effect was offset by increased growth in warmer years. We hypothesize that golden perch are responding to fluctuations in food availability and intraspecific competition related to water level and to an optimization of physiological growth conditions related to increases in growing season length. Based on our analyses, we made predictions of future growth under a number of climate change scenarios that incorporate forecast deviations in stream‐flows and air temperature. Despite climatic models predicting significant declines in future water availability, fish growth may increase due to a disproportionate lengthening of the growing season. As the two lakes are at the limit of the southerly range of golden perch, our results are consistent with previous findings of climate‐change driven latitudinal range shifts in a poleward direction. We discuss assumptions concerning the constancy of ecological interactions into the future that warrant further study. Our research provides a novel application of biochronological analysis that could be used elsewhere to further our knowledge of species responses to changing environments.

Influence of Climate on the Growth of Hybrid Poplar in Michigan

This study examined the influence of climate on cumulative and interannual growth patterns of 18 full-sib families of hybrid poplars (Populus × smithii Boivin) derived from different geographical locations (state counties) of natural stands of aspen parents (trembling aspen (Populus tremuloides Michx.) and bigtooth aspen (Populus grandidentata Michx.)). The hybrids were subsequently planted in 1982 in southern mid-Michigan at Michigan State University (MSU) Sandhill Research Area. Cumulative measures of hybrid poplar productivity (diameter, height, basal area, and stem volume) in 2009 (28 years since plantation establishment) were related via correlation analysis to geographical distances and climatic variables (temperature and precipitation) between parental county locations and between parental locations and the plantation site. Tree-ring analysis methods (dendrochronology) were also used to quantify the influence of climate (i.e., mean temperature and total precipitation at monthly and 3-month seasonal scales) on interannual basal area growth rates of hybrid poplars. Analyses of cumulative measures of growth indicated a maternal effect: full-sib families had higher productivity if they had a maternal parent originating from a state county that was close to or had higher temperature (annual and summer) and summer precipitation than corresponding parameters of the planting site. Principal component analysis indicated that 17 of the 18 full-sib families shared a large amount of common growth variation. Dendrochronological analyses of interannual growth-climate relationships indicated that growth was mainly affected by the degree of late summer to fall moisture stress in both the current and previous growth season, and the degree of winter harshness.

Climate‐growth analysis for a Mexican dry forest tree shows strong impact of sea surface temperatures and predicts future growth declines

AbstractTropical forests will experience relatively large changes in temperature and rainfall towards the end of this century. Little is known about how tropical trees will respond to these changes. We used tree rings to establish climate‐growth relations of a pioneer tree, Mimosa acantholoba, occurring in tropical dry secondary forests in southern Mexico. The role of large‐scale climatic drivers in determining interannual growth variation was studied by correlating growth to sea surface temperature anomalies (SSTA) of the Atlantic and Pacific Oceans, including the El Niño‐Southern Oscillation (ENSO). Annual growth varied eightfold over 1970–2007, and was correlated with wet season rainfall (r=0.75). Temperature, cloud cover and solar variation did not affect growth, although these climate variables correlated with growth due to their relations with rainfall. Strong positive correlations between growth and SSTA occurred in the North tropical Atlantic during the first half of the year, and in the Pacific during the second half of the year. The Pacific influence corresponded closely to ENSO‐like influences with negative effects of high SSTA in the eastern Pacific Niño3.4 region on growth due to decreases in rainfall. During El Niño years growth was reduced by 37%. We estimated how growth would be affected by the predicted trend of decreasing rainfall in Central America towards the end of this century. Using rainfall predictions of two sets of climate models, we estimated that growth at the end of this century will be reduced by 12% under a medium (A1B) and 21% under a high (A2) emission scenario. These results suggest that climate change may have repercussions for the carbon sequestration capacity of tropical dry forests in the region.

Dendrochronological investigation of wood extractives

X-ray microdensitometry was applied to a set of Scots pinewood (i.e. low extractive content). Earlywood and latewood properties were determined as minimum and maximum densities of each tree ring and the potential influence of acetone-soluble extractives (i.e. non-structural and secondary constituents of wood) was estimated using tree-ring statistics. The occurrence of extractives in different portions of wood was determined using dendrochronological methods, by comparing the densities of unextracted and extracted wood. It was not only found that unextracted samples exhibited inflated earlywood and latewood density values, but the growth trends were also altered. Extractives flattened the inter-annual growth variability, both in earlywood and latewood, and influenced the estimation of intra-annual radial growth variations. Characterizing the varying amount of extractives is of inter-disciplinary importance. The results in this study describe their occurrence and show that the radial variations in extractives could be highly detailed by simply using densitometry-based dendrochronology.

OXYGEN ISOTOPE COMPOSITION OF BIVALVE SEASONAL GROWTH INCREMENTS AND AMBIENT WATER IN THE RIVERS RHINE AND MEUSE

Abstract The application of oxygen isotope ratios (δ18O) from freshwater bivalves as a proxy for river discharge conditions in the Rhine and Meuse rivers is investigated. We compared a dataset of water temperature and water δ18O values with a selection of recent shell δ18O records for two species of the genus Unio in order to establish: (1) whether differences between the rivers in water δ18O values, reflecting river discharge conditions, are recorded in unionid shells; and (2) to what extent ecological parameters influence the accuracy of bivalve shell δ18O values as proxies of seasonal, water oxygen isotope conditions in these rivers. The results show that shells from the two rivers differ significantly in δ18O values, reflecting different source waters for these two rivers. The seasonal shell δ18O records show truncated sinusoidal patterns with narrow peaks and wide troughs, caused by temperature fractionation and winter growth cessation. Interannual growth rate reconstructions show an ontogenetic grow...

Validation of annual growth rings in freshwater mussel shells using cross dating

We examined the usefulness of dendrochronological cross-dating methods for studying long-term, interannual growth patterns in freshwater mussels, including validation of annual shell ring formation. Using 13 species from three rivers, we measured increment widths between putative annual rings on shell thin sections and then removed age-related variation by standardizing measurement time series using cubic splines. Initially, cross dating was a valuable quality control technique allowing us to correct interpretive and measurement errors in 16% of specimens. For all species, growth varied among years but was highly synchronous among individuals. Standardized measurement time series of 94% of individuals were significantly correlated with species master chronologies, and mean interseries correlations ranged from 0.37 to 0.96. Growth was also synchronous among species, even from different rivers, and growth was negatively correlated with mean annual streamflow for most species except Quadrula pustulosa from a regulated dam tailrace. Highly synchronous growth and the strong relationship to streamflow showed that large-scale environmental signals generated non-age-related variation in mussel growth giving strong support for annual formation of the growth increments we measured. Cross dating can be a valuable technique for studying freshwater mussel growth providing quality control, validation of annual rings, and reconstruction of long-term growth histories.

An intractable climate archive — Sclerochronological and shell oxygen isotope analyses of the Pacific geoduck, Panopea abrupta (bivalve mollusk) from Protection Island (Washington State, USA)

Annual growth increment patterns of cardinal teeth (CT) of Panopea abrupta (Conrad) can reportedly provide information about past climate variations. However, little is known about the intra-annual timing and rate of shell growth necessary to interpret such records. In addition, it remains unclear whether actual temperatures can be reliably inferred from δ 18O values of geoduck {goo'e-duk} shells. This study compared high-resolution environmental records (hourly to monthly resolved temperature, bi-weekly to monthly δ 18O water and salinity data) with temperatures reconstructed from oxygen isotope values of the outer shell layer ( Tδ 18O OSL) and cardinal tooth portions ( Tδ 18O CT) of different contemporaneous specimens alive at the same locality. Results indicate that shell growth mainly occurred between March/April and November/December with a maximum during May–August. This finding must be considered when comparing the “annual” growth increment width chronologies to environmental parameters. In addition, intra-annual δ 18O shell values require the calculation of weighted averages instead of arithmetic means. During ontogeny, the duration of the growing season remained nearly unchanged; an important finding for paleoclimate studies based on inter-annual growth patterns. Seasonal shell growth was strongly correlated with temperature ( R = 0.93, R 2 = 0.86, p < 0.0001). Presumably due to individual differences in the exchange rate between the extrapallial fluid (EPF) and the ambient water, the outer shell layer of some specimens formed out of oxygen isotopic equilibrium, particularly during summer (high growth rates, increased 18O depletion of the EPF). This resulted in a Tδ 18O OSL difference of up to 2 °C among different specimens. In addition, a bias was observed in different specimens toward daytime or nighttime temperatures, particularly during summer. Such a bias may be related to individual differences in the physiological activity at ultradian time-scales or to elevated predation pressure. More importantly, CT portions (= inner shell layer) formed in isotopic disequilibrium with the ambient water. Typically, reconstructed temperatures differed by more than 3–4 °C from actual water temperatures. Within specimens, Tδ 18O OSL and Tδ 18O CT were offset by ca. 2 °C. Some Tδ 18O CT also exhibited unexplained inter-annual trends, so that Tδ 18O CT among specimens varied by up to 4 °C. Given the δ 18O shell inconsistency between and among shells, a small seasonal temperature amplitude barely exceeding 4 °C and the error bars of T δ 18O of geoducks at this setting on the order of ± 2 °C (error bars of the paleothermometry equation + variable δ 18O water values + precision error of the mass spectrometer), the geochemical record of a single P. abrupta may not serve as a suitable paleoclimate archive. A reliable approximation to paleotemperatures may only be achieved by exclusively sampling the outer shell layer of multiple contemporaneous specimens, so that the Tδ 18O OSL variance among shells can be quantified.

Potential effects of climate change on the growth of lodgepole pine across diameter size classes and ecological regions

We examined 65 lodgepole pine ( Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) sites in Alberta using a dendrochronological approach in order to examine the relationships between climate and growth of lodgepole pine across elevational ecoregions and diameter size classes. The 4 elevational ecoregions sampled included the Boreal Highlands (BH: 13 sites); the Foothills (FH: 36 sites); a grouping of the montane and subalpine zones of the southern Rocky Mountains (RM: 12 sites); and the montane zone of the Cypress Hills (CH: 4 sites). The first diameter size class was comprised of the three largest (top) diameter trees at each site. The tree list of each plot was ranked, then divided into three groups of equal basal area and the tree at the midpoint of each group (small, medium, and large) was selected for the other three size classes. Annual growth in basal area of lodgepole pine was generally sensitive to heat and moisture stress in late summer of the previous year, the degree of winter harshness, and the timing of the start of the growing season. Growth was inhibited by low temperature in all winter months at the most northern BH sites which had the coldest winters, but this effect was interrupted in some of the midwinter months in the more southerly sites in the RM, and we postulated this was due to the damaging influences of Chinook winds. Interannual growth patterns were strongly correlated between top diameter trees and the other classes, and trees of all diameter classes generally responded to climate in the same way, which indicated that it is sufficient to sample only the largest diameter trees in a stand to provide insight into growth–climate relationships. The forecasted growth estimates indicate that future climate warming will negatively impact the productivity of lodgepole pine in the FH, the heart of lodgepole distribution and productivity in Alberta.