Origin of the forest steppe and exceptional grassland diversity in Transylvania (central‐eastern Europe)

Abstract

Aim The forest steppe of the Transylvanian Plain is a landscape of exceptionally diverse steppe-like and semi-natural grasslands. Is this vegetation a remnant of a once continuous temperate forest extensively cleared by humans, or has the area, since the last glacial, always been a forest steppe? Understanding the processes that drive temperate grassland formation is important because effective management of this biome is critical to the conservation of the European cultural landscape.Location Lake Stiucii, north-western Romania, central-eastern Europe.Methods We analysed multi-proxy variables (pollen, coprophilous fungi, plant macroremains, macrocharcoal) from a 55,000 year discontinuous sequence (c. 55,000-35,000; 13,000-0 cal. yr bp), integrating models of pollenbased vegetation cover, biome reconstruction, global atmospheric simulations and archaeological records.Results Needleleaf woodland occurred during glacial Marine Isotope Stage (MIS) 3, but contracted at the end of this period. Forest coverage of c. 55% (early Holocene) and 65% (mid-Holocene) prevailed through the Holocene, but Bronze Age humans extensively cleared forests after 3700 cal. yr bp. Forest coverage was most widespread between 8600 and 3700 cal. yr bp, whereas grasses, steppe and xerothermic forbs were most extensive between 11,700 and 8600 cal. yr bp and during the last 3700 cal. yr bp. Cerealia pollen indicate the presence of arable agriculture by c. 7000 cal. yr bp. Main conclusionsWe have provided the first unequivocal evidence for needleleaf woodland during glacial MIS 3 in this region. Extensive forests prevailed prior to 3700 cal. yr bp, challenging the hypothesis that the Transylvanian lowlands were never wooded following the last glaciation. However, these forests were never fully closed either, reflecting dry growing season conditions, recurrent fires and anthropogenic impacts, which have favoured grassland persistence throughout the Holocene. The longevity of natural and semi-natural grasslands in the region may explain their current exceptional biodiversity. This longer-term perspective implies that future climatic warming and associated fire will maintain these grasslands.

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

“…between 2200 and 1300 cal yr BP (Tóth et al, 2015). Our hydroclimate inference is supported by the reconstructions of low lake water level at Lake Ştiucii (Feurdean et al, 2013), and generally low lake levels recorded in central Europe (Magny, 2004), but contrasts with higher water levels at Lake Sfânta Ana (Magyari et al, 2009) and simulated slightly increase in growing season precipitation (Feurdean et al, 2015b). The DWT partly correlates with reconstructions from northern Poland that inferred a dry phase between 2250-25 2100 cal yr BP and wet shifts around 2750-2400 and 2000 cal yr BP (Lamentowicz et al, 2008).…”

“…Our hydroclimate reconstruction agree with the low lake level and simulated high growing 23 season temperature and evapotranspiration for Transylvania before 6500 cal yr BP, but contrasts with the simulated increase in soil moisture conditions, and a decline in growing season temperature and evapotranspiration thereafter (Feurdean et al, 2015b).…”

Oak canopy arthropod communities: which factors shape its structure?

“…In this way, canopy arthropods could be useful to predict the consequences of climate change, disturbances, or the loss of genetic diversity in oak forests. The use of canopy arthropods to examine the dynamics of the forest as well as alterations in vegetation cover by humans can be an efficient tool in time and cost compared to a longerterm perspective that implies information about palaeoecological record, pollen-based vegetation modeling, and biome reconstruction and global climate simulations (i.e., Feurdean et al 2015).…”

Vegetation dynamics and fire history at the southern boundary of the forest vegetation zone in European Russia during the middle and late Holocene

“…Fire, livestock grazing and agriculture have been detected during the late Holocene in a number of studies (Behre 1981;Kalis et al, 2003;Bradley et al, 2013;Kunes et al, 2015) and are suggested to have had a substantial impact on vegetation (Feurdean et al, 2015). These direct human impacts can potentially both demonstrate the human consequences of climate change and complicate interpretation of vegetation change in strictly climatic terms.…”