Higher climatic sensitivity of Scots pine (Pinus sylvestris L.) subjected to tourist pressure on a hiking trail in the Brodnica Lakeland, NE Poland

Abstract

Climate condtions constitute some of the main factors affecting variation in annual tree-ring growth. However other exogenous processes including geomorphic activity can affect substantially the rate of tree growth. Currently little is known on how human activity such as trampling affects tree growth along hiking trails.We analyzed annual growth variation in 42 Scots pine trees (Pinus sylvestris L.) subjected to what is known as tourist pressure on a heavily used hiking trail in the Brodnica Lakeland located in Northeastern Poland and compared them with 45 pin. trees growing under natural conditions. Specifically, we compared the climate sensitivity of pine trees growing under trampling pressure with a pine reference site using climate variables such as mean, minimum and maximum monthly air temperature and monthly precipitation. Positive and negative pointer years for two sites were designated using the Becker algorithm and compared.Results revealed that Scots pine annual growth at both sites was highly correlated with winter (January, February) and spring (March) air temperatures and February precipitation. However, both the response function analysis and pointer year analysis revealed higher climatic sensitivity of trees subjected to trampling. It was revealed that thermal and pluvial conditions play an important role for Scots pine growth at the trampling site (PRES), especially in June and July when cambium is probably most active. At the same time, these are the months during which tourist activity is the most intense. Tree growth on a hiking trail was positively correlated with higher precipitation and lower maximum air temperature in June and July. This may indicate that pine trees subjected to trampling are threatened by a potential moisture limitation that occurs within and around the studied hiking trail due to an increase in soil compaction. Additionally, the study revealed growth reduction in pine trees subjected to trampling pressure starting from the late 1970s, i.e., right at a time when a strong increase in tourist traffic was noted across the Brodnica Lakeland.The study shows that human impact associated with trampling on hiking trails significantlly affects the growth of Scots pine and should be taken into account in future dendroecological studies.