Climate model projections suggest widespread drying in the Mediterranean Basin and wetting in Fennoscandia in the coming decades largely as a consequence of greenhouse gas forcing of climate. To place these and other “Old World” climate projections into historical perspective based on more complete estimates of natural hydroclimatic variability, we have developed the “Old World Drought Atlas” (OWDA), a set of year-to-year maps of tree-ring reconstructed summer wetness and dryness over Europe and the Mediterranean Basin during the Common Era. The OWDA matches historical accounts of severe drought and wetness with a spatial completeness not previously available. In addition, megadroughts reconstructed over north-central Europe in the 11th and mid-15th centuries reinforce other evidence from North America and Asia that droughts were more severe, extensive, and prolonged over Northern Hemisphere land areas before the 20th century, with an inadequate understanding of their causes. The OWDA provides new data to determine the causes of Old World drought and wetness and attribute past climate variability to forced and/or internal variability.
COBISS.SI-ID: 2469769
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 micro-environment. 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
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