Mean July Temperature Research Articles

Reconstructions of Paleoecological and Paleoclimatic Conditions of the Late Pleistocene and Holocene according to the Results of Chironomid Analysis of Sediments from Medvedevskoe Lake (Karelian Isthmus)

The use of chironomids (Diptera: Chironomidae) as indicators of changes in natural and climatic settings allows one to reconstruct paleoclimatic and paleoenvironmental conditions. Based on the results of lithological and chironomid analyses, the loss on ignition (LOI) values, as well as the results of radiocarbon dating (14C AMS), new data on the paleoclimate in the Karelian Isthmus, in particular the quantitative reconstruction of the mean July temperature (TJuly, °C) in the Late Pleistocene and Holocene and the evolution of the ecosystem of Medvedevskoe Lake have been obtained.

Detecting treeline dynamics in response to climate warming using forest stand maps and Landsat data in a temperate forest

BackgroundTreeline dynamics have inevitable impacts on the forest treeline structure and composition. The present research sought to estimate treeline movement and structural shifts in response to recent warming in Cehennemdere, Turkey. After implementing an atmospheric correction, the geo-shifting of images was performed to match images together for a per pixel trend analysis. We developed a new approach based on the NDVI, LST (land surface temperature) data, air temperature data, and forest stand maps for a 43-year period. The forest treeline border was mapped on the forest stand maps for 1970, 1992, 2002, and 2013 to identify shifts in the treeline altitudes, and then profile statistics were calculated for each period. Twenty sample plots (10 × 10 pixels) were selected to estimate the NDVI and LST shifts across the forest timberline using per-pixel trend analysis and non-parametric Spearman’s correlation analysis. In addition, the spatial and temporal shifts in treeline tree species were computed within the selected plots for four time periods on the forest stand maps to determine the pioneer tree species.ResultsA statistically significant increasing trend in all climate variables was observed, with the highest slope in the monthly average mean July temperature (tau = 0.62, ρ < 0.00). The resultant forest stand maps showed a geographical expansion of the treeline in both the highest altitudes (22 m–45 m) and the lowest altitudes (20 m–105 m) from 1970 to 2013. The per pixel trend analysis indicated an increasing trend in the NDVI and LST values within the selected plots. Moreover, increases in the LST were highly correlated with increases in the NDVI between 1984 and 2017 (r = 0.75, ρ < 0.05). Cedrus libani and Juniperus communis spp. were two pioneer tree species that expanded and grew consistently on open lands, primarily on rocks and soil-covered areas, from 1970 to 2013.ConclusionThe present study illustrated that forest treeline dynamics and treeline structural changes can be detected using two data sources. Additionally, the results will have a significant contribution to and implication for treeline movement studies and forest landscape change investigations attempting to project climate change impacts on tree species in response to climate warming. The results will assist forest managers in establishing some developmental adaptation strategies for forest treeline ecotones.

Current Trends in Climate Change in Yakutia

The spatial distribution patterns of climatic changes in Yakutia are considered. For 26 meteorological stations of Yakutia we calculated the linear trend coefficients of climatic characteristics: air temperature (mean annual, January and July temperatures) and the mean annual amount of atmospheric precipitation from 1966 to 2016. Maps of climate change trends were compiled from linear trend coefficients. A spatial analysis of the zonal (regional) peculiarities of the climate of Yakutia has been carried out. An increase in air temperature was established for the 50-year period under consideration. It was found that the annual values of the air temperature trend are positive and, on average, a characteristic trend change interval is 0.3 to 0.6 °C/10 yr. Most of the meteorological stations recorded trends of air temperature with maximum values in winter and minimum values in summer. It was determined that the values of the trends in annual precipitation show different directions, and positive trends occur on more than 70% of the territory of Yakutia. Their maximum corresponds to the mountain-taiga regions of Southern Yakutia. Negative trends in precipitation with values of up to–15 mm/10 yr. are observed in tundra landscapes. The findings show that different regions of Yakutia respond differently to climate change. The trend of an increase in mean annual temperature is largely due to the rise in temperatures during the winter months. The rise in air temperature in Yakutia may be part of global warming. Over the last 50 years there has been an increase in the amount of precipitation in Yakutia as a whole.

Potential forcings of summer temperature variability of the southeastern Tibetan Plateau in the past 12 ka

Investigating potential forcing mechanisms of terrestrial summer temperature changes from the Asian summer monsoon influenced area is of importance to better understand the climate variability in these densely populated regions. The results of spectral and wavelet analyses of the published chironomid reconstructed mean July temperature data from Tiancai Lake on the SE Tibetan Plateau are presented. The evidence of solar forcing of the summer temperature variability from the site on centennial timescales where key solar periodicities (at 855 ± 40, 465 ± 40, 315 ± 40 and 165 ± 40 year) are revealed. By using a band-pass filter, coherent fluctuations were found in the strength of Asian summer monsoon, Northern Hemisphere high latitude climate and high elevation mid-latitude (26°N) terrestrial temperatures with solar sunspot cycles since about 7.6 ka. The two abrupt cooling events detected from the Tiancai Lake record, centered at ∼9.7 and 3.5 ka were examined respectively. Coupled with the paleoclimate modeling results, the early Holocene event (9.7 ka) is possibly linked to an ocean-atmospheric feedback mechanism whereas the latter event (3.5 ka) may be more directly related to external forcing.

Modern pollen assemblages from human-influenced vegetation in northwestern China and their relationship with vegetation and climate

Modern pollen spectra can improve the interpretation of fossil pollen records used to reconstruct past vegetation, climate and human impacts. It is important, therefore, to carefully examine the relationships between modern pollen spectra, vegetation, climate and human activity. Here, we present the results of an analysis of the pollen spectra of 143 surface pollen samples from farmland, wasteland, desert, steppe/meadow, forest and river valley along a transect from Lanzhou to Urumqi, in northwestern China. The modern pollen assemblages are mainly composed of Amaranthaceae, Artemisia, Poaceae, Asteraceae, Ephedra and Nitraria. The results indicate that in general the surface pollen assemblages of different vegetation types reliably represent the modern vegetation in terms of the composition of the main taxa and the dominant types. Farmland is dominated by cereal-type (≥ 15%) and Amaranthaceae (≥ 20%), while the pollen assemblages of wasteland (i.e. the vegetation immediately surrounding farmland) are mainly composed of Amaranthaceae (≥ 25%), Artemisia (≥ 20%), Poaceae (≥ 10%), Asteraceae (≥ 5%) and Cyperaceae (≥ 5%). Amaranthaceae (≥ 45%) and Ephedra (≥ 10%) are the most important taxa in desert, and Cyperaceae (≥ 35%) and Thalictrum (≥ 2%) are the dominant pollen types in steppe/meadow. Forest and river valley samples are characterized by high frequencies of Picea (≥ 10%) and Cyperaceae (≥ 20%). Both constrained and partial canonical ordination techniques (RDA and partial RDA) of the main pollen types and environmental variables show that the modern pollen spectra are primarily controlled by mean annual precipitation (MAP). Cyperaceae, Thalictrum and Brassicaceae are positively correlated with MAP and negatively correlated with mean July temperature (TJuly), while the representation of certain other types, such as Amaranthaceae, Ephedra and Nitraria, is negatively correlated with MAP and positively correlated with TJuly. The Human Influence Index (HII) is significantly correlated with cereal-type pollen, and it can also differentiate human-influenced and natural vegetation. Our results provide a basis for improving the interpretation of fossil pollen records from arid northwestern China and similar regions.

Changes in the geographical distribution of plant species and climatic variables on the West Cornwall peninsula (South West UK).

Recent climate change has had a major impact on biodiversity and has altered the geographical distribution of vascular plant species. This trend is visible globally; however, more local and regional scale research is needed to improve understanding of the patterns of change and to develop appropriate conservation strategies that can minimise cultural, health, and economic losses at finer scales. Here we describe a method to manually geo-reference botanical records from a historical herbarium to track changes in the geographical distributions of plant species in West Cornwall (South West England) using both historical (pre-1900) and contemporary (post-1900) distribution records. We also assess the use of Ellenberg and climate indicator values as markers of responses to climate and environmental change. Using these techniques we detect a loss in 19 plant species, with 6 species losing more than 50% of their previous range. Statistical analysis showed that Ellenberg (light, moisture, nitrogen) and climate indicator values (mean January temperature, mean July temperature and mean precipitation) could be used as environmental change indicators. Significantly higher percentages of area lost were detected in species with lower January temperatures, July temperatures, light, and nitrogen values, as well as higher annual precipitation and moisture values. This study highlights the importance of historical records in examining the changes in plant species’ geographical distributions. We present a method for manual geo-referencing of such records, and demonstrate how using Ellenberg and climate indicator values as environmental and climate change indicators can contribute towards directing appropriate conservation strategies.

滇西北石卡雪山2个针叶树种森林上限径向生长对温度和降水的响应

PDF HTML阅读 XML下载 导出引用 引用提醒 滇西北石卡雪山2个针叶树种森林上限径向生长对温度和降水的响应 DOI: 10.5846/stxb201703260521 作者: 作者单位: 西南林业大学国家高原湿地研究中心,西南林业大学国家高原湿地研究中心,西南林业大学国家高原湿地研究中心,西南林业大学国家高原湿地研究中心,西南林业大学国家高原湿地研究中心,西南林业大学国家高原湿地研究中心 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（31600395）；云南省教育厅科学研究基金项目（2015Z136，2017YJS094）；云南省高原湿地科学创新团队（2012HC007）；西南林业大学科技创新基金项目（C16057） Radial growth response of two conifers to temperature and precipitation at upper forest limits in Shika Snow Mountain, Northwestern Yunnan Plateau Author: Affiliation: National Plateau Wetlands Research Center,Southwest Forestry University,National Plateau Wetlands Research Center,Southwest Forestry University,National Plateau Wetlands Research Center,Southwest Forestry University,National Plateau Wetlands Research Center,Southwest Forestry University,,National Plateau Wetlands Research Center,Southwest Forestry University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:基于树木年轮学的理论和方法，建立滇西北高原石卡雪山森林上限丽江云杉（Picea likiangensis）和高山松（Pinus densata）差值年表，运用响应函数研究其与气候因子的关系，进而阐明影响滇西北高原针叶树种径向生长的主要气候因子，并利用冗余分析（RDA）进一步分析并验证树木生长与温度和降水的关系。研究结果表明：石卡雪山森林上限针叶树种径向生长主要受温度影响，温度和降水对树木生长有滞后效应，2个树种对气候响应存在差异。具体表现为（1）丽江云杉径向生长受温度和降水的共同作用，与上年10月平均最低温呈显著负相关，与上年11月平均最高温以及当年7月温度呈显著正相关，上年8月和当年5月降水抑制其生长；（2）高山松径向生长与上年10月平均温和平均最高温、11月平均温呈显著正相关，与当年7月平均温和平均最高温呈显著负相关，与降水未达到显著相关水平；（3）冗余分析与响应函数分析结果基本一致，进一步证明该方法能够有效量化树木径向生长与气候因子的关系。能够为气候变化背景下的滇西北高原森林生态系统管理与保护提供理论依据。 Abstract:The Northwestern Yunnan Plateau, located in the southeastern edge of the Tibet Plateau, is a region sensitive to global climate change. Multiple tree species form the upper treeline on different snow mountains within the region, making the mountains ideal sites for dendrochronological studies. However, climate-growth relationships in the Shika Snow Mountain (one of the typical snow mountains in the region) are unclear, and improved understanding of tree growth response to climate change in Shika is fundamental to predicting growth under future climate change. To detect growth response of multiple species to climate change, we developed residual chronologies of Picea likiangensis and Pinus densata at upper distributional limits in Shika Snow Mountain, Northwestern Yunnan Plateau, using dendrochronology. We used response function to study relationships between residual chronologies and climatic factors, aiming to elucidate the main climatic factors affecting radial growth of conifers in the Northwestern Yunnan Plateau. To further analyze and verify the relationships between radial growth and temperature and precipitation, redundancy analysis was applied. Results showed that temperature was the main factor influencing conifer growth at the upper forest limits in the Shika Snow Mountain; temperature and precipitation have a lag effect on tree radial growth and the two conifers responded differently to climatic factors. Specifically:(1) The radial growth of P. likiangensis was affected by temperature and precipitation, showing a significantly negative correlation with mean minimum temperature of the previous October, and a significantly positive correlation with mean maximum temperature of the previous November and temperature of the current July. Precipitation of the previous August and current May inhibited growth of P. likiangensis. (2) The radial growth of P. densata was significantly and positively correlated with mean temperature and maximum temperature of the previous October and mean temperature of the previous November, and showed a significantly negative correlation with mean temperature and maximum temperature of the current July. However, no significant correlation was detected between growth and precipitation. (3) The redundancy analysis presented similar results as the response function analysis, further indicating that the method can effectively quantify the relationship between tree radial growth and climatic factors. This study provides a theoretical basis for the management and protection of forest ecosystems in the Northwestern Yunnan Plateau faced with climate change. 参考文献 相似文献 引证文献

The sensitivity of diatom taxa from Yakutian lakes (north-eastern Siberia) to electrical conductivity and other environmental variables

Relative abundances of 157 diatom taxa from Yakutian lake surface-sediments were investigated for their potential to indicate certain environmental conditions. Data from 206 sites from Arctic, sub-Arctic and boreal environments were included. Redundancy analyses were performed to assess the explanatory power of mean July temperature (T-July), conductivity, pH, dissolved silica concentration, phosphate concentration, lake depth and vegetation type on diatom species composition. Boosted regression tree analyses were performed to infer the most relevant environmental variables for abundances of individual taxa and weighted average regression was applied to infer their respective optimum and tolerance. Electrical conductivity was best indicated by diatom taxa. In contrast, only few taxa were indicative of Si and water depth. Few taxa were related to specific pH values. Although T-July, explained the highest proportion of variance in the diatom spectra and was, after conductivity, the second-most selected splitting variable, we a priori decided not to present indicator taxa because of the poorly understood relationship between diatom occurrences and T-July. In total, 92 diatom taxa were reliable indicators of a certain vegetation type or a combination of several types. The high numbers of indicative species for open vegetation sites and for forested sites suggest that the principal turnover is the transition from forest-tundra to northern taiga. Overall, our results reveal that preference ranges of diatom taxa for environmental variables are mostly broad, and the use of indicator taxa for the purposes of environmental reconstruction or environmental monitoring is therefore restricted to marked rather than subtle environmental transitions.

Thermal acclimation of photosynthesis and respiration of southern and northern white spruce seed sources tested along a regional climatic gradient indicates limited potential to cope with temperature warming.

Background and AimsKnowledge of thermal acclimation of physiological processes of boreal tree species is necessary to determine their ability to adapt to predicted global warming and reduce the uncertainty around the anticipated feedbacks of forest ecosystems and global carbon cycle to climate change. The objective of this work was to examine the extent of thermal acclimation of net photosynthesis (An) and dark respiration (Rd) of two distant white spruce (Picea glauca) seed sources (from south and north of the commerial forest zone in Québec) in response to latitudinal and seasonal variations in growing conditions.MethodsThe temperature responses of An, its biochemical and biophysical limitations, and Rd were measured in 1-year-old needles of seedlings from the seed sources growing in eight forest plantations along a regional thermal gradient of 5.5 °C in Québec, Canada.Key ResultsThe average optimum temperature (Topt) for An was 19 ± 1.2 °C and was similar among seed sources and plantation sites along the thermal gradient. Net photosynthesis at Topt (Aopt) varied significantly among plantation sites and was quadratically related to the mean July temperature (MJT) of plantation sites. Topt for mesophyll conductance, maximum electron transport rate and maximum rate of carboxylation were 28, 22 and 30 °C, respectively. Basal respiration rate (Rd at 10 °C) was linearly and negatively associated with MJT. Q10 of Rd (the rate of change in Rd with a 10 °C increase in temperature) did not show any significant relationship with MJT and averaged 1.5 ± 0.1. The two seed sources were similar in their thermal responses to latitudinal and seasonal variations in growing conditions.ConclusionsThe results showed moderate thermal acclimation of respiration and no evidence for thermal acclimation of photosynthesis or local genetic adaptation for traits related to thermal acclimation. Therefore, growth of local white spruces may decline in future climates.

A multi-proxy view of exceptionally early postglacial development of riparian woodlands with Ulmus in the Dniester River valley, western Ukraine

This article presents the first multi-proxy study of palaeoecosystem changes during the Late Weichselian and Early Holocene in western Ukraine. The site is a former oxbow lake situated in the Dniester River valley (western Ukraine). We hypothesised that this area may have been one of the nuclei for the Holocene expansion of elm (Ulmus), a primary arboreal taxon in riparian woodlands, in the Central and Eastern European lowlands. Our study was undertaken on a profile encompassing the period ca. 12,900–9880cal. BP. We applied selected palaeobotanical, palaeozoological and geochemical analyses. During the Younger Dryas the area was dominated by well-developed Pinussylvestris-Betula woodlands. Drier habitats were overgrown by Juniperus shrublands and steppe communities. Patches of tundra with Betulanana were also present. Ulmus started to spread on the lower river terraces before ca. 11,840cal. BP i.e., during the late Younger Dryas, which suggests this area as a nucleus for its Holocene expansion. A chironomid-based reconstructed mean July temperature (MJT) of 15–17°C is suggested during the Younger Dryas. The main Ulmus expansion started ca. 11,160cal. BP and its optimum in local woodlands lasted until ca. 10,340cal. BP, when Pinussylvestris rapidly expanded. The reconstructed MJT varied between 18 and 21°C during the Ulmus optimum; however, it rapidly declined to 16°C around ca. 10,800cal. BP. Fire activity increased before ca. 10,870cal. BP, concurrent with the climate warming at the Younger Dryas-Holocene transition, but did not affect the population of Ulmus, a taxon intolerant of fires. Wildfires probably affected patches of steppe vegetation and Pinussylvestris-Betula woodlands occupying higher elevations of the valley and watersheds. However, changes in the fire activity may have stimulated Ulmus retreat at ca. 10,340cal. BP.

Growth response of Abies georgei to climate increases with elevation in the central Hengduan Mountains, southwestern China

Climatic harshness is expected to increase at higher elevations; however, elevational trends of tree radial growth response of high-elevation forests to climate change need to be investigated at different locations because of existing local variability in site-specific climatic conditions. We developed tree-ring width chronologies of Yunnan fir (Abies georgei) along elevation gradients at two sites in the central Hengduan Mountains (HM). High-elevation forests of A. georgei showed growth synchronicity and common growth signals along elevation gradients, indicating a common climatic forcing, although tree radial growth rates decreased with increasing elevation. Radial growth of Yunnan fir showed positive correlations with summer temperatures and February precipitation and moisture availability, but were negatively correlated with spring temperatures. The strongest positive relationship indicated summer (July) mean and minimum temperatures are the most important growth determining climatic factors for tree radial growth in the cold environment of HM, and this relationship revealed a clear elevational trend with stronger correlations at higher altitudes. In contrast, tree radial growth was negatively correlated with June precipitation and moisture availability. The whole study period 1954–2015 was split in two sub-periods of equal length. Comparing the early sub-period (1954–1984) to the later sub-period (1985–2015), tree growth response to the summer temperatures strongly increased, while it became weaker to June precipitation and moisture availability. High-elevation Yunnan fir forests in the HM currently benefit from elevated growing season temperatures under humid summer conditions. However, increasing temperatures may induce drought stress on tree radial growth if the observed decreasing trend in humidity and precipitation continues.

Episodic deposition of Illinois Valley Peoria silt in association with Lake Michigan Lobe fluctuations during the last glacial maximum

AbstractThe chronology and cause of millennial depositional oscillations within last glacial loess of the Central Lowlands of the United States are uncertain. Here, we present a new age model that indicates the Peoria Silt along the Illinois River Valley accumulated episodically from ~28,500 to 16,000 cal yr BP, as the Lake Michigan Lobe margin fluctuated within northeastern Illinois. The age model indicates accelerated loess deposition coincident with regional glacial advances during the local last glacial maximum. A weakly developed paleosol, the Jules Geosol, represents a period of significantly slower deposition, from 23,700 to 22,000 cal yr BP. A gastropod assemblage-based reconstruction of mean July temperature shows temperatures 6–10°C cooler than modern during Peoria Silt deposition. Stable oxygen and carbon isotope values (δ18O and δ13C) of gastropod carbonate do not vary significantly across the pedostratigraphic boundary of the Jules Geosol, suggesting slower loess accumulation was a result of reduced glacial sediment supply rather than direct climatic factors. However, a decrease in δ18O values occurred between 26,000 and 24,000 cal yr BP, synchronous with the Lake Michigan Lobe’s southernmost advance. This δ18O decrease suggests a coupling of regional summer hydroclimate and ice lobe position during the late glacial period.

Reconstruction of palaeoecological and palaeoclimatic conditions of the Holocene in the south of the Taimyr according to an analysis of lake sediments

A sediment core from Khatanga-12 Lake (Taimyr Peninsula, Krasnoyarsk krai) has been studied. The 131.5-cm-long core covers ca. 7100 years of sedimentation. Chironomid analysis, a qualitative reconstruction of the paleoenvironment in the region, and a quantitative reconstruction of variations of the mean July air temperature and in the water depth of the lake have been performed using Northern Russia chironomid-inferred mean July temperature models (Nazarova et al., 2008, 2011, 2015). Khatanga-12 Lake was formed during the Middle Holocene warming as a result of thermokarst processes. The development of the lake ecosystem at different stages of its development was influenced by climatic and cryolithogenic factors. The Middle Holocene warming, which occurred around 7100–6250 cal. years BP, activated thermokarst processes and resulted in the formation of the lake basin. Later, between 6250 and 4500 cal. years BP, a period of cooling took place, as is proved by chironomid analysis. The bottom sediments of the lake during this period were formed by erosion processes on the lake shores. The reconstructed conditions were close to the modern after 2500 cal. years BP.

Predicting microalgae growth and phosphorus removal in cold region waste stabilization ponds using a stochastic modelling approach.

A stochastic ecological model with an integrated equilibrium temperature model was developed to predict microalgae growth and phosphorus removal in cold region waste stabilization ponds (WSPs). The model utilized a Monte Carlo simulation to account for parameter uncertainty. The equilibrium temperature model was parameterized using field data collected from two WSPs in Nunavut, Canada, from 2012 to 2014. The equilibrium temperature model provided good agreement with field data on a daily time step. The full model was run using historic (1956-2005) temperature and solar radiation data from five communities (Baker Lake, Cambridge Bay, Coral Harbour, Hall Beach, Resolute) in Nunavut, Canada. The communities represented a range of geographical locations and environmental conditions. Logistic regression on pooled model outputs showed that mean July temperature and mean treatment season temperature (June 1-September 15, ice-free period) provided the best predictors for microalgae growth. They had a predictive success rate of 93 and 88%, respectively. The modelled threshold (50% probability from the Monte Carlo simulation) for microalgae growth was 8.7 and 5.6°C for the July temperature and mean treatment season temperature, respectively. The logistic regression was applied to each community (except Sanikiluaq) in Nunavut using historic climate data and a probability of microalgae growth was calculated. Based on the model results, soluble phosphorus concentrations consistent with secondary treatment could be achieved if WSP depth is less than 2m. The model demonstrated a robust method to predict whether a microalgae bloom will occur under a range of model parameters.

Tree growth and its climate signal along latitudinal and altitudinal gradients: comparison of tree rings between Finland and the Tibetan Plateau

Abstract. Latitudinal and altitudinal gradients can be utilized to forecast the impact of climate change on forests. To improve the understanding of how these gradients impact forest dynamics, we tested two hypotheses: (1) the change of the tree growth–climate relationship is similar along both latitudinal and altitudinal gradients, and (2) the time periods during which climate affects growth the most occur later towards higher latitudes and altitudes. To address this, we utilized tree-ring data from a latitudinal gradient in Finland and from two altitudinal gradients on the Tibetan Plateau. We analysed the latitudinal and altitudinal growth patterns in tree rings and investigated the growth–climate relationship of trees by correlating ring-width index chronologies with climate variables, calculating with flexible time windows, and using daily-resolution climate data. High latitude and altitude plots showed higher correlations between tree-ring chronologies and growing season temperature. However, the effects of winter temperature showed contrasting patterns for the gradients. The timing of the highest correlation with temperatures during the growing season at southern sites was approximately 1 month ahead of that at northern sites in the latitudinal gradient. In one out of two altitudinal gradients, the timing for the strongest negative correlation with temperature at low-altitude sites was ahead of treeline sites during the growing season, possibly due to differences in moisture limitation. Mean values and the standard deviation of tree-ring width increased with increasing mean July temperatures on both types of gradients. Our results showed similarities of tree growth responses to increasing seasonal temperature between latitudinal and altitudinal gradients. However, differences in climate–growth relationships were also found between gradients due to differences in other factors such as moisture conditions. Changes in the timing of the most critical climate variables demonstrated the necessity for the use of daily-resolution climate data in environmental gradient studies.

Summer temperature variability inferred from subfossil chironomid assemblages from the south-east margin of the Qinghai–Tibetan Plateau for the last 5000 years

We present a quantitative mean July temperature record spanning the last c. 5000 years from an alpine lake in south-western China. The reconstruction is based on the application of an established chironomid-based inference model using 100 lakes from the region. The reconstructed summer temperature changes are within 2.4°C of modern throughout the record. The results suggest that the summer temperature changes in south-east margin of the Qinghai–Tibetan plateau (QTP) predominantly responds to Asian Summer Monsoon influence, forced by summer insolation until c. 3200 cal. BP. Four cooling events, each separated by c. 500 years (between 3200 and 1600 cal. BP), were observed and these may correspond to the 500-year quasi-periodic solar fluctuation. The most recent cooling period, that is, ‘the Little Ice Age’, appears robust in the Heihai Lake record, providing further evidence that a hemisphere-wide forcing mechanism is possible for this climate event.

Was there an abrupt cold climatic event in the middle Eemian? Pollen record from a palaeolake at the Hieronimowo site, NE Poland

Seventy samples of lacustrine sediments from a palaeolake at the Hieronimowo site, NE Poland were investigated by pollen analysis method. The obtained results indicate that the examined sequence spans the whole Eemian Interglacial (MIS 5e), the beginning of the Early Vistulian (Weichselian; MIS 5d) and some undefined period of the Plenivistulian (Middle Weichselian; MIS 2-4). The specific feature of the studied profile is the great thickness of deposits representing the hornbeam phase of the Eemian Interglacial (E5 R PAZ), which was the younger part of the climatic optimum of this interglacial, and the very well developed pollen record of this phase, that is absent in other profiles in NE Poland. Due to this, our study allowed, for the first time in NE Poland, the detailed reconstruction of changes in the vegetation and in the mean January and July temperature during the middle part of the Eemian Interglacial. This reconstruction unequivocally rules out the existence of an abrupt short-lasting cold event at that time. Only a gradual slight increase in temperature was apparent during the older part of the hornbeam phase (to >21 °C for July, and to >0 °C for January) and gradual decrease during its younger part (to >17 °C for July, and to > -5 °C and <-2 °C for January). So during the warmest part of the hornbeam phase, reconstructed temperatures for July were similar as in older part of the Eemian optimum (hazel phase, E4 R PAZ), however they were approximately 2 °C higher for January.

How warm? How wet? Hydroclimate reconstruction of the past 7500 years in northern Carpathians, Romania

As natural and anthropogenic ecosystems are dependent on the local water availability, understanding past changes in hydroclimate represents a priority in research concerning past climate variability. Here, we used testate amoebae (TA) and chironomid analysis on a radiocarbon dated complex of small pond and peat bog sediment profiles from an ombrotrophic bog (Tăul Muced, northern Carpathians, Romania) to quantitatively determine major hydrological changes and July air temperature over the last 7500years.Wet mire surface conditions with a pH between 2.3 and 4.5 were inferred for the periods 4500–2700 and 1300–400calyrBP by the occurrence of Archerella flavum, Amphitrema wrightianum and Hyalosphenia papilio. Dry phases in mire surface conditions and a pH between 2.5 and 5 were inferred for 7550–4500, 2750–1300 and 0calyrBP–present by the dominance of Nebela militaris, Difflugia pulex and Phryganella acropodia. The quantitative reconstruction of mean July temperature based on the chironomid communities suggests low summer temperatures for the periods 6550–5600, 4500–3150 and 1550–600calyrBP, while periods of slightly higher summer temperatures were observed for 5600–4500, 3150–1550 and 100calyrBP–present. There is a generally good agreement between drier phases of the peat surface conditions with higher July temperature, suggesting that temperature may have been a controlling factor for water table fluctuation.Our quantitative reconstructions, among the first for central eastern Europe, show a relatively good agreement with other palaeohydrological studies from central eastern Europe, but contrast with others estimates from north-west Europe. Another important aspect of our study is that it provides valuable information on changes in local hydrology and the potential effect of the mean summer temperature over these changes.

Summer temperature regimes in southcentral Alaska streams: watershed drivers of variation and potential implications for Pacific salmon

Climate is changing fastest in high-latitude regions, focusing our research on understanding rates and drivers of changing temperature regimes in southcentral Alaska streams and implications for salmon populations. We collected continuous water and air temperature data during open-water periods from 2008 to 2012 in 48 nonglacial salmon streams across the Cook Inlet basin spanning a range of watershed characteristics. The most important predictors of maximum temperatures, expressed as mean July temperature, maximum weekly average temperature, and maximum weekly maximum temperature (MWMT), were mean elevation and wetland cover, while thermal sensitivity (slope of the stream–air temperature relationship) was best explained by mean elevation and area. Although maximum stream temperatures varied widely between years and across sites (8.4 to 23.7 °C), MWMT at most sites exceeded established criterion for spawning and incubation (13 °C), above which chronic and sublethal effects become likely, every year of the study, which suggests salmon are already experiencing thermal stress. Projections of MWMT over the next ∼50 years suggest these criteria will be exceeded at more sites and by increasing margins.

Climate change risks, extinction debt, and conservation implications for a threatened freshwater fish: Carmine shiner (Notropis percobromus)

Climate change is affecting many freshwater species, particularly fishes. Predictions of future climate change suggest large and deleterious effects on species with narrow dispersal abilities due to limited hydrological connectivity. In turn, this creates the potential for population isolation in thermally unsuitable habitats, leading to physiological stress, species declines or possible extirpation. The current extent of many freshwater fish species' spatio-temporal distribution patterns and their sensitivity to thermal impacts from climate change − critical information for conservation planning − are often unknown. Carmine shiner (Notropis percobromus) is an ecologically important species listed as threatened or imperilled nationally (Canada) and regionally (South Dakota, United States) due to its restricted range and sensitivity to water quality and temperature. This research aimed to determine the current distribution and spatio-temporal variability in projected suitable habitat for Carmine shiner using niche-based modeling approaches (MaxEnt, BIOCLIM, and DOMAIN models). Statistically downscaled, bias-corrected Global Circulation Models (GCMs) data was used to model the distribution of Carmine shiner in central North America for the period of 2041–2060 (2050s). Maximum mean July temperature and temperature variability were the main factors in determining Carmine shiner distribution. Patterns of projected habitat change by the 2050s suggest the spatial extent of the current distribution of Carmine shiner would shift north, with >50% of the current distribution changing with future projections based on two Representative Concentrations Pathways for CO2 emissions. Whereas the southern extent of the distribution would become unsuitable for Carmine shiner, suitable habitats are predicted to become available further north, if accessible. Importantly, the majority of habitat gains for Carmine shiner would be in areas currently inaccessible due to dispersal limitations, suggesting current populations may face an extinction debt within the next half century. These results provide evidence that Carmine shiner may be highly vulnerable to a warming climate and suggest that management actions - such as assisted migration - may be needed to mitigate impacts from climate change and ensure the long-term persistence of the species.