A systematic compilation of temperature (n = 10) and moisture sensitive (n = 4) proxy records of the Northern Balkan - Carpathian (NBC) region with annual resolution for the past millennium is presented and evaluated. The proxy-climate relationship is re-evaluated using a uniform climatological dataset providing a longer calibration. The originally determined response seasons were in the most part verified. Spectral constraints were established by combining wavelet coherence analysis and band filtering, thus, the signal-to-noise ratio was successfully improved in certain cases, either by separating the temperature/moisture sensitive frequencies in complex signals, and/or by extracting “focus” bands. In the case of winter temperature, the earliest available dates in the natural proxy records were 1774 AD, for spring and summer they were 1732 AD and 1040 AD respectively, while for hydroclimate this date was 1497 AD. Although only one record was available for winter, it showed a pronounced similarity to winter temperature reconstructions from adjacent areas outside the NBC. Spring thermal proxies were comprised of grape-vine phenology data from the Western NBC margin, these being in quite good agreement with each other, for instance, in the case of the characteristic mutual decadal pattern the mild springs of the 1750s. In addition, a common long-term cooling trend was observed, starting in the mid18th century and ending at the turn of the 20th century. The comparison of summer temperature records indicated that proxies of the same origin/source tend to show a stronger mutual variation than those located close to each other, but of different types. This serves as a warning in the interpretation of climate field reconstructions from multiproxy networks. The studied summer proxies show a remarkably strong linear relationship with nearby records outside the NBC, weakening as their distance increases. The two most persistent multi-decadal cold summer periods (~1780 - 1840 & 1430 - 1500 AD) were decisively mirrored in the proxies. The longest and most recent reconstruction from the North Slovakian Tatras shows a unique warming (after ~1900 AD) reflected neither within, nor outside the NBC, casting doubt on its reliability. In general, weaker coherence was observed between the hydroclimate proxies, drawing attention to a general phenomenon: the range of the spatial representativity of hydroclimate proxies is usually smaller. Therefore, their network should be further developed. One of a few shared regional summer drought periods occurred in the 1750s, being most pronounced in the Central and Southeastern NBC. Moreover, this was reflected in the neighbouring South Moravian drought history, too.
COBISS.SI-ID: 4352678
Forest mortality is globally present, and pedunculate oak (Quercus robur) forests in Europe are no exception at all. The aim of this study was to tackle the issue of oak floodplain forests response to water level, temperature and precipitation changes due to the altered climate conditions. We examined interannual and interseasonal scales using dendroecological analysis. The goal was to review the growth from the perspective of forest management practice, including specific recommendations for forest managers. The most important environmental variable in the growth of pedunculate oak forests in Serbia (Srem region) in the last 60 years was the Sava River water level. Due to the decrease in the water level and temperature increase in the last 30 years, a general decline in growth was observed. The months that displayed the most significant correlation between the growth, water level and temperature were April, May, June, July and August, while May was the most significant month as far as precipitation influence is concerned. Responses of the various tree groups due to different age and sites (flooded vs. non-flooded, virgin vs. managed forests) were observed, although all tree groups displayed fundamentally the same response to variations in environmental conditions. The “Stara Vratična” virgin forest was considered to be without future owing to the growth decline and lack of regeneration.
COBISS.SI-ID: 4316326
The first regional chronology of black pine (Pinus nigra Arnold) from Albania, its response to climate and a 428-year long reconstruction of June–July temperatures for the 1583–2010 period are presented. Samples were collected at five locations from the north to the south of Albania. We constructed a 552-year long Pinus nigra chronology with sufficient sample depth for potential climate reconstruction from 1583 to 2010 (428 years). Response to precipitation was significant only for July of the current year (0.23), while a clear temperature response to the May–August period was identified, with July having by far the highest correlation (−0.47). When combined, June–July temperatures had the highest correlation of all tested combinations (r = −0.63), explaining almost 40% of the tree-ring width variability. The test of the climate signal temporal stability using a 31-year running correlation highlighted the very stable relationship between tree-ring indices and June–July temperatures. The spatial extent of the regional Pinus nigra chronology tested, using a field correlation function, showed very high spatial correlation over a large part of the Balkan Peninsula and even southern Italy. Based on high explained variance between tree-ring indices and June–July temperatures and significant values of reduction of error (RE) and coefficient of efficiency statistics (CE; 0.62 and 0.25 in the calibration period), a linear model was developed, with June–July temperatures reconstructed for the 1583–2010 period. Our reconstruction and identified extreme years were compared with various temperature, drought and precipitation reconstructions from nearby regions, as well as data from documentary archives. We confirmed a high degree of similarity of our reconstruction with other reconstructions and documentary data.
COBISS.SI-ID: 4010406
We analysed two groups of Quercus robur trees, growing at nearby plots with different micro-location condition (W-wet and D-dry) in the floodplain Krakovo forest, Slovenia. In the study we compared the growth response of two different tree groups to environmental variables, the potential signal stored in earlywood (EW) structure and the potential difference of the information stored in carbon isotope discrimination of EW and latewood (LW). For that purpose, EW and LW widths and carbon isotope discrimination for the period 1970–2008 AD were measured. EW and LW widths were measured on stained microscopic slides and chronologies were standardised using the ARSTAN program. α-cellulose was extracted from pooled EW and LW samples and homogenized samples were further analysed using an elemental analyser and IRMS. We discovered that W oaks grew significantly better over the whole analysed period. The difference between D and W oaks was significant in all analysed variables with the exception of stable carbon isotope discrimination in latewood. In W oaks, latewood widths correlated with summer (June to August) climatic variables, while carbon isotope discrimination was more connected to River Krka flow during the summer. EW discrimination correlated with summer and autumn River Krka flow of the previous year, while latewood discrimination correlated with flow during the current year. In the case of D oaks, the environmental signal appears to be vague, probably due to less favourable growth conditions resulting in markedly reduced increments. Our study revealed important differences in responses to environmental factors between the two oak groups of different physiological conditions that are preconditioned by environmental stress. Environmental information stored in tree-ring features may vary, even within the same forest stand, and largely depends on the microenvironment. Our analysis confirmed our assumptions that separate EW and LW analysis of widths and carbon isotope discrimination provides complementary information in Q. robur dendroecology.
COBISS.SI-ID: 4235430
The increasing carbon dioxide (CO2) concentration in the atmosphere in combination with climatic changes throughout the last century are likely to have had a profound effect on the physiology of trees: altering the carbon and water fluxes passing through the stomatal pores. However, the magnitude and spatial patterns of such changes in natural forests remain highly uncertain. Here, stable carbon isotope ratios from a network of 35 tree-ring sites located across Europe are investigated to determine the intrinsic water-use efficiency (iWUE), the ratio of photosynthesis to stomatal conductance from 1901–2000. The results were compared with simulations of a dynamic vegetation model (LPX-Bern 1.0) that integrates numerous ecosystem and land–atmosphere exchange processes in a theoretical framework. The spatial pattern of tree-ring derived iWUE of the investigated coniferous and deciduous species and the model results agreed significantly with a clear south-to-north gradient, as well as a general increase in iWUE over the 20th century. The magnitude of the iWUE increase was not spatially uniform, with the strongest increase observed and modelled for temperate forests in Central Europe, a region where summer soil-water availability decreased over the last century. We were able to demonstrate that the combined effects of increasing CO2 and climate change leading to soil drying have resulted in an accelerated increase of iWUE. These findings will help to reduce uncertainties in the land surface schemes of global climate models, where vegetation–climate feedbacks are currently still poorly constrained by observational data.
COBISS.SI-ID: 3932326