Environmental quality assessment of the drainage basin of Lake Engure using Scots pine as a bioindicator

Environmental quality assessment of the Lake Engure drainage area, which is the LT(S)ER region of the Latvian National Long-term Ecological Research network (Latvia LTER), was conducted using three bioindication methods based on Scots pine Pinus sylvestris L.: unspecific bioindication by pine needle tip necrosis, ground level ozone assessment by pine needle chlorotic mottling, and chemical analysis of pine bark. Samples were collected from 40 sites of the region in November 2010. Extent of needle tip necroses did not exceed class 4 (maximum possible value 6). The highest value of index of needle damage by ozone was Idam = 1.62 (maximum possible value 6). Multiple regression analysis of variables describing bark chemistry and needle damage in relation to distance from the sea, nearest roads and villages was performed. Pine bark acidity pH(KCl) and concentration of Mg and Fe decreased significantly (βpH(KCl) =-0.672, P < 0.001; βMg =-0.676, P < 0.001; βFe =-0.514, P < 0.001) with distance of sample site from gravel roads. Electric conductivity (EC) of pine bark and the extent of ozone damage of the first year needles I_dam significantly decreased with distance from the sea (βozone =-0.507, P < 0.01; βEC =-0.453, P < 0.01). PCA of the pine bark chemistry data showed dust pollution from gravel roads to be the main factor responsible for the 33% variation of data. No statistically significant correlations were found between different bioindicator characteristics, except between first and second year ozone damage (ρ = 0.589, P = 0.01).