Pollen, δ15N and δ13C guano-derived record of late Holocene vegetation and climate in the southern Carpathians, Romania

Abstract

Two cores of bat guano were recovered from Topolnița and Gura Ponicovei Caves in the south-west region of Romania and analyzed for δ15N, δ13C and pollen. Deposition of guano began in CE 1537 at Gura Ponicovei and CE 1694 at Topolnița, allowing for the development and interpretation of climate and vegetation records since the Little Ice Age. δ15N values were found to record phases of the North Atlantic Oscillation through the effect of winter precipitation on the local nitrogen cycle. Alternatively, δ13C values are interpreted to correspond with variation in summer precipitation. Both records suggest progressively drier conditions during the termination of the LIA in the region at CE 1870. The transition to landscape openness, with patchy forests of Tilia, Carpinus betulus, and Quercus during this time could be related to the lower water availability at both sites. Wetter conditions inferred from a 3‰ increase in δ15N values between CE 1879 and CE 1970 occurred contemporaneously with a similar trend in European winter precipitation and increased frequency of positive NAO phases during this interval. The δ13C values between CE 1885 and CE 1968 suggest a trend towards a wetter summer climate as well. Although there is at times evidence of forest dynamics being controlled by climate, vegetation appears to be more closely associated with human impact, particularly around Topolnița Cave. The contribution of ruderal pollen indicators from CE 1985 – present is likely related to agricultural practices.