Forest ecosystem development in European nemoreal-boreal forest (NE Poland) over the last 2200 years: Impact of human activity and climate change

Long-term ecological studies can provide useful information on forest ecosystem resilience against past climatic change and human caused disturbances. Here, we present a high-resolution 2200-year-long record of forest development in north-eastern Poland, Suwalki region, using paleobotanical proxies (pollen, plant macrofossils, and charcoal). We show that the pollen abundance of deciduous trees was higher than that of coniferous trees, indicating a near pristine state until 900 AD and a semi-natural forest state until 1500 AD. After 1500 AD, the proportion of coniferous tree taxa surpassed that of deciduous trees and have since remained the dominant forest component. The 17th century experienced massive deforestation coupled with a new phase of human colonization in the area that led to the continued and significant decline of deciduous tree cover, for example, Carpinus, Quercus, and Tilia. Cooling associated with the Little Ice Age may have played a role in Picea's expansion in this area after 1450 AD. Despite significant climatic shifts associated with the warmer Roman Period or Medieval Climate Anomaly and colder Migration Period, as well as a more sustained human impact, Quercus remained a stable forest component until 1500 AD. The stability of Quercus is an important aspect for forest management strategies as future projections suggest warmer conditions and increased frequency of climate extremes will impact forest composition and structure. Our long-term data suggest that forests in the Suwalki region should contain more abundant deciduous tree species, that is, Quercus, whereas conifer cover should be reduced. We also show clear regional differences in the forest development in the Suwalki region, highlighting the importance of local hydrology, geomorphology, and degrees of human activity on the forest composition.

Automated summary

Long-term ecological studies can provide valuable insights into the resilience of forest ecosystems against past climate change and human disturbances. In this study, a 2200-year-long record of forest development in north-eastern Poland was analyzed using paleobotanical proxies. The findings reveal that the forest remained in a near pristine state until 900 AD, followed by a semi-natural state until 1500 AD. After 1500 AD, coniferous trees became the dominant forest component. The 17th century witnessed massive deforestation and continued human impact, leading to a significant decline in deciduous tree cover. Despite climatic shifts and sustained human activities, Quercus remained a stable forest component until 1500 AD. The study emphasizes the importance of Quercus stability for forest management strategies, as future climate changes are expected to impact forest composition and structure. The results suggest the need for increased abundance of deciduous tree species and reduced conifer cover in the Suwalki region. The study also highlights regional differences in forest development, indicating the influence of local hydrology, geomorphology, and human activity on forest composition.