12 millennia of climatic and human induced vegetation changes in the Lower San Valley near Jarosław (SE Poland) in the light of pollen analysis

Veg e ta tion changes in the Lower San Val ley near Jaros³aw are re con structed from the Youn ger Dryas to the pres ent time on the ba sis of palynological anal y sis of the peat core. The pol len pro file came from a an old riverbed and was sup ple mented by ra dio car bon datings. The Youn ger Dryas and early Preboreal veg e ta tion was char ac ter ised by a high pro por tion of for est com mu ni ties with pine (Pinus sylvestris and P. cembra) and birch (Betula), while patches of open area were dom i nated by the steppe with Ar te mi sia. Cli ma tic ame lio ra tion dur ing the Preboreal chronozone led to the rapid spread of elm (Ulmus), which was prob a bly a dom i nant taxon on the low est ter races of the val ley. Terrestrialization of the wa ter body ex ist ing in the palaeomeaner and the sub se quent be gin ning of peat ac cu mu la tion caused a de - te ri o ra tion in pol len pres er va tion. Hence, the in ter pre ta tion of the pro file sec tion span ning the pe riod be tween the Bo - real and Subatlantic chronozones was se ri ously dis turbed due to se lec tive cor ro sion and the overrepresentation of Pinus sylvestris type and Filicales monolete sporomorphs. Be tween ca. 336 and 1152 AD fluc tu a tions in wood land cover were re corded. Im por tant com po nents in those for ests, de spite the dom i na tion of Pinus sylvestris, were Quercus, Carpinus betulus, Fagus sylvatica and Abies alba. The first pol len grains of ce re als (Cerealia type) were found be fore ca. 1605–1414 BC and may be at trib uted to the ag ri cul tural ac tiv ity of the Neo lithic and/or early Bronze tribes. Pe ri - ods of strong de for es ta tion caused by hu mans were prob a bly re lated to the time when the Tarnobrzeska Group of the Lusatian Cul ture and the Przeworska Cul ture were ac tive. The first groups of Slavs did not sig nif i cantly in flu ence the en vi ron ment, but the sub se quent de vel op ment of those groups led to more vis i ble de for es ta tion, which was trig gered af ter the es tab lish ment of Jaros³aw in the 11th cen tury AD.