Mean July Research Articles

The Effect of Climate Parameters on Mean Growing Stock in Russian Forests

Mean growing stock across different wood species and age groups of forests based on the State Forest Inventory 2013 data were correlated by means of regression analysis with climate variables averaged over 1981–2000. The following species categories were predefined: all species, conifers, hardwoods, softwoods, and others. The following age groups were predefined: all ages, young growth, middle-aged, pre-mature, with old-growth forests. The correlation and regression analyses were performed for each of the 20 age and species groups of forests. Mean annual temperature, difference between mean July and mean January temperatures, and annual precipitation were independent variables. Mean stock positively correlates with the mean annual temperature and humidity, and negatively correlates with the difference between mean July and mean January temperature. The correlation coefficient between the mean stock and mean annual temperature had a pronounced upward trend across the species groups, as follows by their value: other species, conifers, hardwoods, and softwoods. Multiple polynomial regression equations, which included all possible combinations of independent variables and their quadratic effects, were found for each species and age groups. Determination coefficients had the highest values (R2 > 0.7) for all species, hardwood species, and mature and middle-aged forests of all species and hardwood species. Other wood species and all young growth were the least predictable (R2 < 0.5). The regression equations could be used to forecast changes in the mean growing stock under changing climate for forests overall and their groups of different age and species composition.

Seasonal variability of lung function and Asthma Quality of Life Questionnaire Scores in adults with uncontrolled asthma

IntroductionAsthma exacerbations spike in the spring and autumn months, yet the seasonal variation of asthma symptoms and lung function is poorly studied.MethodsSeasonal variation of lung function, rescue medication use and...

Frequency of Persistent Blocking and Ridge Events Related to Precipitation over Eastern China during August and Its Preceding Atmospheric Signals

Abstract Based on a recently developed approach that can recognize both persistent blocking and ridge events effectively, the contributions of the frequency of these persistent events (FOPE) over different regions in Eurasia to precipitation over eastern China were investigated. The results reveal that, the FOPE over the longitudinal range of 110°–130°E, near the Stanovoy Mountains and the Okhotsk Sea, is significantly correlated with precipitation over the middle and lower reaches of the Yangtze River (MLRYR) during summer, particularly in August. The preceding full July (or 1–20 July) mean Balkhash Lake–Caucasus geopotential height index, which measures the combined effect of the Balkhash Lake and Caucasus geopotential height anomalies, is closely related to the August geopotential height anomaly around the Stanovoy Mountains and the Okhotsk Sea, and can therefore reflect the August 110°–130°E FOPE. The predictability based on this preceding atmospheric signal seems to be attributable to slow-varying atmospheric processes on a subseasonal (20-day mean) time scale. On this time scale, the Balkhash Lake and Caucasus geopotential height anomalies occur prior to, and seem to modulate, the geopotential height anomaly around the Stanovoy Mountains and the associated 110°–130°E FOPE through an eastward extension and through exciting a positive–negative–positive pattern in 500-hPa geopotential heights, respectively. As a result of the slow-varying atmospheric processes, this preceding atmospheric signal performs well in predicting the August 110°–130°E FOPE, which also facilitates the prediction of the MLRYR precipitation.

Warm Younger Dryas summers and early late glacial spread of temperate deciduous trees in the Pannonian Basin during the last glacial termination (20-9 kyr cal BP)

This paper focuses on the last glacial termination vegetation and climate reorganization of the Eastern Pannonian Plain via the multi-proxy paleoecological analysis of Kokad mire in Eastern Hungary. Grains size, sediment chemistry and magnetic susceptibility records are compared with the pollen and plant macrofossil records on the basis of which biome and quantitative summer mean temperature reconstructions are provided and discussed with other climate records of the region. Biome assignments indicated (graminoid and forb) tundra vegetation from 19,440 cal yr BP with the local presence of Betula pendula, B. pubescens, B. nana, and Pinus sylvestris. A rapid biome shift to cool coniferous forest took place at 16,200 cal yr BP, and a second biome shift was identified at 14,740 cal yr BP when cool mixed forest developed and persisted into the Early Holocene. The most prominent feature of the record was the early post last glacial maximum (LGM) establishment (17,700 cal yr BP) and expansion (14,700 cal yr BP) of elm (Ulmus) and hazel (Corylus) supporting the phylogeographical evidence for extra-Mediterranean refugia in the Pannonian Basin. The fungal spore record indicated the presence of large grazing mammals locally after the LGM until ∼16,780 cal yr BP. Their disappearance predated the biome shift to cold coniferous forest and the final increase of forest fires. Pollen based summer temperature reconstruction suggested relatively warm summers (∼14.5 °C) by 19,440 cal yr BP, and buffered July mean temperature fluctuations throughout the last glacial termination in this region with < 1 °C decrease in summer mean temperatures during the Younger Dryas stadial, and ∼2.2 °C warming in the Early Holocene. Our comprehensive summary of the basin’s Late Pleniglacial (24,000–14,600 cal yr BP) and late glacial paleoenvironmental and paleoclimate records showed a partially wooded landscape with higher woody cover in Western Hungary. Several loess and lake archives confirmed that in this region of Europe the warming after Heinrich event 1 (around 16,200 cal yr BP) had similar amplitude to the late glacial warming.

Using species attributes to characterize late‐glacial and early‐Holocene environments at Kråkenes, western Norway

AbstractAimWe aim to use species attributes such as distributions and indicator values to reconstruct past biomes, environment, and temperatures from detailed plant‐macrofossil data covering the late glacial to the early Holocene (ca. 14–9 ka).LocationKråkenes, western Norway.MethodsWe applied attributes for present‐day geographical distribution, optimal July and January temperatures, and Ellenberg indicator values for plants in the macrofossil data‐set. We used assemblage weighted means (AWM) to reconstruct past biomes, changes in light (L), nitrogen (N), moisture (F), and soil reaction (R), and temperatures. We compared the temperature reconstructions with previous chironomid‐inferred temperatures.ResultsAfter the start of the Holocene around 11.5 ka, the Arctic‐montane biome, which was stable during the late‐glacial period, shifted successively into the Boreo‐arctic montane, Wide‐boreal, Boreo‐montane, Boreo‐temperate, and Wide‐temperate biomes by ca. 9.0 ka. Circumpolar and Eurasian floristic elements characteristic of the late‐glacial decreased and the Eurosiberian element became prominent. Light demand (L), soil moisture (F), nitrogen (N), and soil reaction (R) show different, but complementary responses. Light‐demanding plants decreased with time. Soil moisture was relatively stable until it increased during organic soil development during the early Holocene. Soil nitrogen increased during the early Holocene. Soil reaction (pH) decreased during the Allerød, but increased during the Younger Dryas. It decreased markedly after the start of the Holocene, reaching low but stable levels in the early Holocene. Mean July and January temperatures show similar patterns to the chironomid‐inferred mean July temperature trends at Kråkenes, but chironomids show larger fluctuations and interesting differences in timing.ConclusionAssigning attributes to macrofossil species is a useful new approach in palaeoecology. It can demonstrate changes in biomes, ecological conditions, and temperatures. The late‐glacial to early‐Holocene transition may form an analogue for changes observed in the modern arctic and in mountains, with melting glaciers, permafrost thaw, and shrub encroachment into tundra.

Complexities in interpreting chironomid-based temperature reconstructions over the Holocene from a lake in Western Ireland

Investigation of Holocene climate variability remains challenging. This is largely due to chronological uncertainties and complexities associated with proxies and their relationship with climatic drivers. Pertinent questions still exist regarding the Holocene climate in Ireland, particularly in the early Holocene. We present a mean July air temperature reconstruction based on fossil chironomidae (non-biting midge flies), along with an assessment of chironomid functional traits from five guilds (based on their feeding habits) from Lough Nakeeroge, a small glacial lake in western Ireland. These records span the early to late Holocene (c. 10,000–1500 cal yr BP). The chironomid record is supplemented with pollen data to determine landscape vegetation dynamics, and compared to climate model simulations of the same period. As reliable models are essential for robust analysis of long-term climate change, we critically assess the value of the chironomid transfer function and explore the use of chironomid functional traits to infer past climate variability. While this study demonstrates the complexities of chironomid-based temperature reconstruction in Irish lakes, it endeavours to i) disentangle a complicated Holocene climate history through the exploration of other long-term Holocene records from the island; and ii) improve our understanding of environmental responses to climate variability in Ireland. The findings of this study suggest that the interpretation of chironomid-based temperature transfer functions can be challenging. However, our results demonstrate the influence of climate on the functioning of lake ecosystems over the Holocene, with the promising performance of the collector-filterer feeding guild as a palaeothermometer.

Paleoclimate reconstruction and mire development in the Eastern Great Hungarian Plain for the last 20,000 years

We present the reconstruction of mire vegetation changes and fire history recorded in a continuous sediment profile that spans the last 20,000 cal yr BP from the Late Pleniglacial to Holocene in North-eastern Hungary. We also aimed to reveal past climate changes by using ecological requirements of specific aquatic plants as summer temperature indicators. Our results suggest the formation of a mesotrophic mire around 20,000 cal yr BP with brown moss, Betula sp. and Selaginella selaginoides cover beside the occurrence of Phragmites australis, Typha latifolia and T. angustifolia suggesting base-rich fen and tundra-like wet-ground habitats on the lakeshore. This community shifted to reed dominated swamp at c. 18,300 cal yr BP with inferred min. July temperatures of 12–15.7 °C. pinus sp., Betula nana, B. pendula/pubescens, Hippuris vulgaris and P. australis dominated until 16,600 cal yr BP pointing to shallow muddy stagnant water and colder climatic conditions than in the preceding interval. The most warmth-demanding species, T. latifolia and T. angustifolia indicated July mean temperatures >14–15.7 °C soon after the LGM. The formation of biogenic carbonate also started at an early stage; major accumulation occurred between 15,200 and 10,000 cal yr BP. In the Early Holocene, environmental indicator species (e.g., Phragmites australis and T. latifolia) pointed to warmer and shallower conditions, while the late Holocene was characterized by strong eutrophication and reed swamp dominance on the lakeshore. Elevated macrocharcoal concentration, wood fragments and remains of Typha species suggested frequent local fires and dry mire surface conditions during the last 1700 years.

Expanding the Swiss‐Norwegian chironomid training set with Polish data

The Swiss‐Norwegian training model established in 2011 has been used across Europe to infer past mean July air temperatures using Chironomidae subfossils. It combines reference sites from Norway and the Swiss Alps but lacks representative localities from the central European plains belt. This gap complicates reconstructions from temperate European latitudes, and thus, a Polish training set (TS) was developed. Data from 102 lakes, mainly from Pomerania and the Masurian Lakelands, as well as the Polish Plain, the Sudetes, and the Carpathian Mountains were included. After selecting and merging suitable chironomid taxa, the Swiss‐Norwegian‐Polish TS includes 357 lakes and 134 chironomid morphotypes, and it has a mean July air temperature range of 3.5 to 20.0 °C. The weighted averaging‐partial least squares (WA‐PLS) and artificial neural network (ANN) transfer function based on the extended TS performs well: R2jack = 0.91/0.95 and root mean squared error of prediction (RMSEP) = 1.39 °C/1.34 °C, respectively. The transfer function applied to the Żabieniec Lake sequence (central Poland) reveals higher summer temperatures (2.5–4.0 °C) for the Lateglacial and for the Holocene (1.0 °C) compared to the Swiss‐Norwegian model. The reconstruction based on the Swiss‐Norwegian TS shows an increasing trend from the Bølling‐Allerød Interstadial to the Meghalayan period, whereas the new model reconstruction shows no increasing trend when using WA‐PLS and a slightly decreasing trend when using ANN. Summer temperatures in the Lateglacial in Żabieniec inferred using the Swiss‐Norwegian TS are consistent with other temperature reconstructions for 50–55°N in Europe, while those based on the Swiss‐Norwegian‐Polish TS (SNP TS) show closer affinity to more western sites than the eastern European ones. Despite being uncommon, the application of ANN can be a good equivalent of the WA‐PLS technique especially in situations where the available database is limited to fewer than a few hundred variables.

Evidence of abrupt climate change at 9.3 ka and 8.2 ka in the central Canadian Arctic: Connection to the North Atlantic and Atlantic Meridional Overturning Circulation

This study presents the results of a multi-proxy analysis of a Holocene lacustrine sediment sequence recovered from a small tundra lake in the central Canadian Arctic and links climatic variations there to the North Atlantic. Chironomid and pollen-based reconstructions of mean July air temperature (MJAT) document notable deviations at 9.3 ka and 8.2 ka. Chironomid-inferred July air temperature is depressed by 1.4 °C at 9.3 ka and 1.7 °C at 8.2 ka relative to the long-term chironomid-inferred Holocene average of 9.4 °C. These cooling events also correspond to an increase in Gramineae (Poaceae) and a decrease in Betula pollen, reflecting a decrease in the density of dwarf birch cover. Concurrent, abrupt increases in several diatom taxa, including aerophilic epiphytes, and Sphagnum indicate an expansion of moss habitats as a result of wetter conditions. The expression and timing of the cooling evidenced at TK2 during the early Holocene is consistent with abrupt climate events identified in the North Atlantic and coincides with intervals of North Atlantic cooling and weakened Atlantic Meridional Overturning Circulation (AMOC). This research, which improves our understanding of the spatial extent and magnitude of the 9.3 ka and 8.2 ka events in the central Canadian Arctic, serves as a benchmark for coupled-ocean atmosphere climate models simulating the response of the climate system to abrupt climate events and provides insight in marine-atmosphere teleconnections in the circum-North Atlantic region.

Arctic climate shifts drive rapid ecosystem responses across the West Greenland landscape

Prediction of high latitude response to climate change is hampered by poor understanding of the role of nonlinear changes in ecosystem forcing and response. While the effects of nonlinear climate change are often delayed or dampened by internal ecosystem dynamics, recent warming events in the Arctic have driven rapid environmental response, raising questions of how terrestrial and freshwater systems in this region may shift in response to abrupt climate change. We quantified environmental responses to recent abrupt climate change in West Greenland using long-term monitoring and paleoecological reconstructions. Using >40 years of weather data, we found that after 1994, mean June air temperatures shifted 2.2 °C higher and mean winter precipitation doubled from 21 to 40 mm; since 2006, mean July air temperatures shifted 1.1 °C higher. Nonlinear environmental responses occurred with or shortly after these abrupt climate shifts, including increasing ice sheet discharge, increasing dust, advancing plant phenology, and in lakes, earlier ice out and greater diversity of algal functional traits. Our analyses reveal rapid environmental responses to nonlinear climate shifts, underscoring the highly responsive nature of Arctic ecosystems to abrupt transitions.

Reconstruction of June–July Temperatures Based on a 233 Year Tree-Ring of Picea jezoensis var. microsperma

In this study, ring-width chronology of Picea jezoensis var. microsperma from the Changbai Mountain (CBM) area, Northeast China, was constructed. Growth/climate responses suggested that mean maximum temperature (Tmax) was the limiting factor affecting radial growth of PJ trees in the study region. According to the correlation analysis between the ring-width index and meteorological data, a June–July mean maximum temperature (Tmax6–7) series between 1772 and 2004 was reconstructed by using the standard chronology. For the calibration period (1959–2004), the explained variance of the reconstruction was 41.6%. During the last 233 years, there were 36 warm years and 34 cold years, accounting for 15.5% and 14.7% of the total reconstruction years, respectively. Cold periods occurred in 1899–1913, 1955–1970, and 1975–1989, while warm periods occurred in 1881–1888. The reconstructed temperature series corresponded to the historical disaster records of extreme climatic events (e.g., drought and flood disasters) in this area. Comparisons with other temperature reconstructions from surrounding areas and spatial correlation analysis between the gridded temperature data and reconstruction series indicated that the regional climatic variations were well captured by the reconstruction. In addition, multi-taper method spectral analysis indicated the existence of significant periodicities in the reconstructed series. The significant spatial correlations between the reconstructed temperature series and the El Niño–Southern Oscillation (ENSO), solar activity, and Pacific Decadal Oscillation (PDO) suggested that the temperature in the CBM area indicated both local-regional climate signals and global-scale climate changes.

The impact of hair coat color on physiological variables, reproductive performance and milk yield of Holstein cows in a hot environment

Vulnerable animals to heat stress have been described as ones with dark or black hides due to increasing absorption of solar radiation. The effect of coat color in pluriparous contemporary Holstein cows in a hot environment (mean annual temperature 24.6 °C), on body surface temperature (infrared thermography), physiological and hematological variables as well as milk yield and reproductive performance was assessed using 178 Holstein pluriparous cows (74 predominantly white and 104 predominantly black). Data were collected in the morning and afternoon in July (mean temperature-humidity index 82 units). Body condition score at mid-lactation (128 ± 32 days in milk at the start of the experiment) was higher (P < 0.01) in predominantly white than in black cows (3.3 vs. 3.2). Respiration rate did not differ between groups (72 ± 23 vs. 73 ± 20 breaths/min for white and black cows, respectively, sampling time combined). In contrast, rectal temperature of black cows was 0.1 °C higher (P ≤ 0.01) than white cows, regardless of sampling time. The only significant hematologic change was a slight increase in mean corpuscular volume in black cows (54.7 fL, P < 0.01) compared to white cows (53.8 fL), but it remained within the reference range. Differences due to coat color did not alter body surface temperatures at any time of the day. Conception rates, services per conception, calving intervals and fetal losses were not associated with hair coat color, but cows with predominantly white coat produced 394 kg more (P < 0.01) fat-corrected milk in 305 days compared to cows with predominantly black coat. It was concluded that in this hot-arid environment with cows housed in facilities with extensive cooling, black hair coat moderately reduces 305-d milk yield without affecting milk composition, body surface temperature, and reproductive performance.

Inconsistencies between observed, reconstructed, and simulated precipitation indices for England since the year 1650 CE

Abstract. The scarcity of long instrumental records, uncertainty in reconstructions, and insufficient skill in model simulations hamper assessing how regional precipitation changed over past centuries. Here, we use standardized precipitation data to compare a regional climate simulation, reconstructions, and long observational records of seasonal (March to July) mean precipitation in England and Wales over the past 350 years. The Standardized Precipitation Index is a valuable tool for assessing agreement between the different sources of information, as it allows for a comparison of the temporal evolution of percentiles of the precipitation distributions. These evolutions are not consistent among reconstructions, a regional simulation, and instrumental observations for severe and extreme dry and wet conditions. The lack of consistency between the different data sets may be due to the dominance of internal climate variability over the impact of natural exogenous forcing conditions on multi-decadal timescales. The disagreement between sources of information reduces our confidence in inferences about the origins of hydroclimate variability for small regions. However, it is encouraging that there is still some agreement between a regional simulation and observations. Our results emphasize the complexity of hydroclimate changes during the recent centuries and stress the necessity of a thorough understanding of the processes affecting forced and unforced precipitation variability.

Chironomid-based temperature reconstruction for the Eemian Interglacial (MIS 5e) at Sokli, northeast Finland

The Last Interglacial (Eemian, MIS 5e) can be considered a test-bed for climate dynamics under a warmer-than-present climate. In this study we present a chironomid record from the high latitude Sokli site (N Finland), where a long continuous sediment sequence from the last interglacial has been preserved from glacial erosion. The chironomid-analysis shows a diverse fauna, with dominance of warm-water indicators and shifts in assemblage composition that can be attributed to temperature, lake depth, productivity and habitat availability. Quantitative mean July paleotemperature estimates based on the chironomid data indicate overall mean July air temperatures up to 1 °C warmer than present. Two cooling events can be discerned, the Tunturi event, dated to about 127.5 ka BP, in the lower part of the sequence, and the Värriö event, dated to about 119 ka BP, associated with the beginning of a cooling trend in the upper part of the record. Warm conditions already at the onset of the interglacial contrast with a recent chironomid-based last interglacial temperature reconstruction from Denmark, which suggests a late onset of Eemian warming. The relatively small increase in inferred temperatures compared to present day temperatures at Sokli differs from other high latitude Eemian sites, and likely reflects the influence of the Atlantic Meridional Overturning Circulation in maintaining already elevated temperatures in Fennoscandia during interglacials.

Climatic Conditions of Steppe and Tundra Formations in the Altai Highland Depressions

«Вестник Санкт-Петербургского университета. Науки о Земле» — научно-теоретический рецензируемый журнал, обобщающий результаты исследований в области геологии, гидрогеологии и геохимии, петрологии и экологии, ландшафтного планирования и геоморфологии, экономической и социальной географии.

Environmental changes of the last 1000 years on Prince of Wales Island, Nunavut, Canada

ABSTRACTA pollen record from a lake sediment core from southeastern Prince of Wales Island, Nunavut, Canada (SW08; 72.3177, −97.2678, 104 m a.s.l) provides the first high-resolution July temperature reconstruction for the last 1,000 years for the central Canadian Arctic Archipelago. The vegetation underwent marked transitions during the Little Ice Age (LIA; 1500–1800 CE) and Medieval Climate Anomaly (MCA; 1090–1250 CE), which was primarily observed in the proportion of Cyperaceae, Poaceae, and Salix pollen. Cyperaceae pollen was highest in the samples corresponding to the MCA, whereas Poaceae increased during the LIA. In the last 30 years, Salix and Betula pollen increased. The mean July temperature reconstruction showed a long-term cooling from 1080–1915 CE with a sustained cold period from 1800–1915 CE prior to twentieth-century warming. A synthesis of paleoclimate records from across the Arctic demonstrates that pollen-based reconstructions record both high and low frequency climate variability, when sampling resolution is sufficient, and can improve regional climate reconstructions.

Changes in Sensitivity of Tree-Ring Widths to Climate in a Tropical Moist Forest Tree in Bangladesh

Tree growth in the tropics is strongly influenced by climate. However, reported tree growth responses to climate are largely inconsistent, varying with geographic location, forest type, and tree species. It is thus important to study the growth responses of tropical trees in sites and species that are under-represented so far. Bangladesh, a country influenced by the Asian monsoon climate, is understudied in terms of tree growth response to climate. In the present study, we developed a 121-year-long regional ring-width index chronology of Chukrasia tabularis A. Juss. sampled in two moist forest sites in Bangladesh to investigate tree growth responses to climate in monsoon South Asia. Standard dendrochronological methods were used to produce the ring-width chronologies. The climate sensitivity of C. tabularis was assessed through bootstrap correlation analysis and the stationarity and consistency of climate–growth relationships was evaluated using moving correlation functions and comparing the regression slopes of two sub-periods (1950–1985 and 1986–2015). Tree growth was negatively correlated with the mean, minimum, and maximum temperatures, particularly during the early growing season (March). Likewise, precipitation negatively influenced tree growth in the later growing season (October). Besides, radial growth of Chukrasia sharply ceased in years following strong and moderate El Niño events. In parallel with a significant positive trend in local temperatures, tree growth sensitivity to early growing season (March–April) mean temperatures and July minimum temperatures increased in recent decades. Tree growth sensitivity to October precipitation and April vapor pressure deficit also increased. Overall, climate–growth relationships were stronger during the period 1986–2015 than during 1950–1985. Changes in climate sensitivity might be linked to a warming trend that induced an increase in the dry season length during recent decades. With a further predicted temperature increase at our study sites, our results suggest that radial growth of C. tabularis will further decline in response to climate warming.

The Little Ice Age signature in a 700-year high-resolution chironomid record of summer temperatures in the Central Eastern Alps

Despite the fact that the Little Ice Age (LIA) is well documented for the European Alps, substantial uncertainties concerning the regional spatio-temporal patterns of temperature changes associated with the LIA still exist, especially for their eastern sector. Here we present a high-resolution (4–10 years) 700-year long mean July air temperature reconstruction based on subfossil chironomid assemblages from a remote lake in the Austrian Eastern Alps to gain further insights into the LIA climatic deterioration in the region. The record provides evidence for a prolonged period of predominantly cooler conditions during AD 1530–1920, broadly equivalent to the climatically defined LIA in Europe. The main LIA phase appears to have consisted of two cold time intervals divided by slightly warmer episodes in the second half of the 1600s. The most severe cooling occurred during the eighteenth century. The LIA temperature minimum about 1.5 °C below the long-term mean recorded in the mid-1780 s coincides with the strongest volcanic signal found in the Greenland ice cores over the past 700 years and may be, at least in part, a manifestation of cooling that followed the long-lasting AD 1783–1784 Laki eruption. A continuous warming trend is evident since ca AD 1890 (1.1 °C in 120 years). The chironomid-inferred temperatures show a clear correlation with the instrumental data and reveal a close agreement with paleotemperature evidence from regional high-elevation tree-ring chronologies. A considerable amount of the variability in the temperature record may be linked to changes in the North Atlantic Oscillation.

Persist or take advantage of global warming: A development of Early Holocene riparian forest and oxbow lake ecosystems in Central Europe

In this study, we focus on the environmental changes recorded in the San River valley (Stubno–Nakło site, south-eastern Poland) at the beginning of the Holocene. This multi-proxy study for the first time in the region of the northern foreland of the Western Carpathians included quantitative thermal reconstruction based on Chironomidae and high-stratigraphic resolution of 14C AMS dating. We hypothesised that (i) climate events during the Early Holocene contributed to ecosystem turnovers via stimulating disturbances related to the river's fluvial activity and (ii) woodland and oxbow lake ecosystems became more resilient to flood disturbances along with the advance of forest succession on the floodplain. The results revealed that the response of ecosystems on the Early Holocene warming was strongly linked with the decrease in fluvial activity of the river. The reconstruction of the mean July temperature based on Chironomidae revealed the exceptionally high rate of warming during the period of ca. 11,490–11,460 cal. BP (at least 1 °C per decade) up to values > 2 °C than modern ones. During this period, the lake trophy and productivity started to increase with a simultaneous spread of Betula woodlands on the alluvial plain. The “Preboreal oscillation” cooling was dated at ca. 11,450–11,250 cal. BP. At that time, an increased climate instability led to a higher rate of extremal events such as flood at ca. 11,400–11,330 cal. BP, which probably led to the disruption of the Betula population. The development of riparian woodlands, initiated by the expansion of Ulmus from ca. 11,100 cal. BP, and further spread of Quercus and Fraxinus excelsior on the alluvial plain and lower river terraces increased plant transpiration and therefore limited the river runoff and its fluvial activity. This, together with the expansion of reed belt communities, probably limited the impact of floods on the oxbow lake. However, ca. 10,010–9880 cal. BP traces of higher fluvial activity, but of lower impact, were recorded.

Ecosystem Responses to Climate-Related Changes in a Mediterranean Alpine Environment Over the Last ~ 180 Years

The effect of recent climatic warming is significant in the Mediterranean region, especially in high-mountain areas. This study uses multiple sedimentary proxies from Rio Seco Lake, a remote alpine lake in the Sierra Nevada, southeastern Spain, to reconstruct recent environmental and ecological changes in the lake and catchment. Two main climatic periods can be distinguished during the past 180 years: Period One (1820 to ~ 1920s) characterized by colder and wetter conditions than the more recent Period Two (~ 1920s to the present), characterized by warmer and drier conditions. Independent proxies such as subfossil chironomid assemblages, n-alkane indices, pollen data and/or spectrally inferred chlorophyll-a concentrations indicate a longer ice-cover period, colder water temperature and more pronounced accumulation of snow in the catchment during Period One than in Period Two, likely producing water stress for catchment plant growth because of the low rate of ice melting in Period One. As temperature increases and precipitation decreases from the 1920s onwards, a wider development of wetland plants is observed, which is associated with the longer warm season that contributed to snow and ice melting in the catchment. This continuing temperature rise and precipitation decrease over the past 60-years by ~ 0.24°C per decade and –0.92 mm/y, respectively, lead to an important increase in chlorophyll-a and changes in lake biotic assemblages. Major chironomid community structure changes to warmer water taxa were recorded, resulting in a 2°C increase in mean July air temperature inferred by chironomids from ~ 1950 onwards. An inferred increase in primary production for the past few decades is consistent with higher temperatures, while wider development of wetland plants is associated with longer warm season. The coherence between independent environmental proxies, each associated with distinct mechanistic linkages to climatic shifts, strengthens our interpretations of a recent warming trend and an intensification of summer drought in this high-mountain area leading to distinct changes in the lake and its catchment. The impact of this climate change on the summits of Sierra Nevada and its influence transcends its geographical limits because these systems provide ecosystem services to a vast area.