Detecting changes in industrial pollution by analyzing heavy metal concentrations in tree-ring wood from Romanian conifer forests.

The impact of air pollution on forests, especially in urban areas, has been increasingly discussed recently. Many pollutants, including heavy metals, are released into the atmosphere from various sources, such as mining, non-ferrous metal processing plants, and fossil fuel combustion. These pollutants can adversely affect not only tree growth but also other species, including humans. This study compared the concentrations of several elements in tree-ring wood from two conifer species (Silver fir, Abies alba; Norway spruce, Picea abies) growing in polluted and unpolluted areas. Two regions in northern Romania (Bicaz and Tarnița) that were subjected to historical pollution changes were selected. Two chemical analyses were used: inductively coupled plasma mass spectrometry (ICP-MS) and X-ray fluorescence spectrometry (XRF). The silver fir trees from the intensively polluted area in the Tarnița region were negatively impacted by industrial pollution: the Mn concentrations were, on average, three times higher in polluted areas than in unpolluted areas (ca. 30 vs. 10 mg kg-1). This finding was consistent for both ICP-MS and XRF analyses. However, in Norway spruce, this difference was found only in the XRF data, which detected Mn concentrations seven times higher in trees from polluted areas than those from unpolluted areas (ca. 700 vs. 100 mg kg-1). In the Tarnița region, Norway spruce accumulated more heavy metals than silver fir, but the most pronounced differences between polluted and unpolluted areas were found in silver fir. The two analytical methods are commonly used to determine metal concentrations in wood, and they complement each other, with ICP-MS having a low detection limit for some elements and XRF having higher detection limits and better accuracy. Each method has its advantages and disadvantages, and the optimal method depends on many factors, such as the type of heavy metal analyzed, its concentration in wood, sample type, cost, analysis time, and sample preparation.

Forest vulnerability to extreme climatic events in Romanian Scots pine forests.

In the last years, large-scale mass forest withering and dieback have been reported for Scots pine (Pinus sylvestris) across eastern Europe, particularly in Romania. In these regions, the climate models forecast an increase in intensity and frequency of extreme climate events such as drought. Taking into account these aspects, the exact identification of the influences of drought on the loss of radial growth and vitality in Scots pine stands becomes mandatory. To achieve this aim, we developed the first country-wide Scots pine dendrochronological network in Romania consisting of 34 chronologies of basal area increment (BAI), and including 1401 individual tree-ring width series. Romanian Scots pine forests were severely impacted by the 2000 and 2012 droughts. The high temperatures and low precipitation from April to August were the main climatic causes of radial-growth reduction and large-scale withering in some areas. By mapping post-drought growth resilience, we identified locations where resilience was low and could identify foci of future forest dieback and high tree mortality. The projected appearance of similar prolonged and severe droughts in the future will lead to the damage or local extinction of some Scots pine forests in Romania, regardless of their age, composition or spatial location. The elaboration of adaptive forest management strategies to the impact of climate changes, specifically designed for the Scots pine stands, is not possible without knowing and understanding these aspects.