The damage caused by wind in middle-aged Scots pine stands on permanent thinning experimental plots

In July 2002, the very strong hurricane appeared in northern Poland, which caused destruction of forest cover of area more than 10,000 ha. The permanent thinning research plot in a 53-year-old pine stand located in Myszyniec forest district (150 km north of Warsaw) was lying on the edge of damaged area. The following treatments were tested on this plot: 1) control plot (without thinning); 2) schematic cut in 20-year-old stand, selective thinning to 40 years, then thinning from below; 3) schematic cut in 20-year-old stand, then selective thinning; 4) selective thinning in young stand (20–40 years), then thinning from below and 5) selective thinning all the time. A significant part of this plot was completely destroyed and in the other part of the plot, some trees survived. A small part of the plot resisted the wind attack. An analysis of the amount of destroyed trees (measured by basal area) showed no differences between particular silvicultural treatments. The level of damage differed between particular parts of the plot. Another plot located in Ostrów Mazowiecka forest district (100 km NE of Warsaw) with the same thinning treatments was touched by heavy wind in July 2011 when the stand was 62 years old. Unlike the hurricane of 2002, this storm did not destroy the experimental plot which was located outside the zone of heaviest calamity. Therefore, damage on this plot had point and group character. Although on particular measurement units, share of broken or fallen trees did not exceed 10% of total basal area, it can be observed that the lowest level of damage was noticed on plots with selective thinning in young age and thinning from below in older stand.

The Impact of Air Pollution on the Growth of Scots Pine Stands in Poland on the Basis of Dendrochronological Analyses

The aim of this study was to evaluate Scots pine stand degradation caused by the pollutants emitted from Zakłądy Azotowe Puławy, one of the biggest polluters of the environment in Poland for over 25 years (1966–1990). To assess the pollution stress in trees, we chose the dendrochronological analysis We outlined three directions for our research: (i) the spatio-temporal distribution of the growth response of trees to the stress associated with air pollution; (ii) the direct and indirect effects of air pollution which may have influenced the growth response of trees; and (iii) the role of local factors, both environmental and technological, in shaping the growth response of trees. Eight Scots pine stands were selected for study, seven plots located in different damage zones and a reference plot in an undamaged stand. We found that pollutant emission caused disturbances of incremental dynamics and long-term strong reduction of growth. A significant decrease in growth was observed for the majority of investigated trees (75%) from 1966 (start of factory) to the end of the 1990s. The zone of destruction extended primarily in easterly and southern directions, from the pollution source, associated with the prevailing winds of the region. At the end of the 1990s, the decreasing trend stopped and the wider tree-rings could be observed. This situation was related to a radical reduction in ammonia emissions and an improvement in environmental conditions. However, the growth of damaged trees due to the weakened health condition is lower than the growth of Scots pine on the reference plot and trees are more sensitive to stressful climatic conditions, especially to drought.

A methodological approach for the assessment of basic crown parameters in Scots pine stands

Among other measurement techniques applied for the assessment of leaf area index, direct methods are still valued as the most accurate measures and often implemented as calibration tools. Even though more attention has been given to indirect measurements of tree crown properties in forest ecosystems over the last decades, the present study was designed to discuss the direct (destructive) and indirect (non-destructive) methods used for the assessment of crown measures in the stands defoliated from 20 to 90%. The stands with similar stand characteristics and representing relatively wide range of defoliation served as an appropriate target for the assessment of foliage mass variations. Overall, this study showed that the foliage mass or its surface area and defoliation at the stand level can be determined by the conventional methods used for the assessment of defoliation in forest monitoring programme as well as the PAR transmission methods. The findings showed that needle surface area decreased with the increase of tree defoliation; however, the changes of branch and stem surface areas were insignificant. Otherwise, the branch and shoot area contribute significantly to the total vegetation surface area at least in Scots pine stands. This study also strengthened the idea that the indirect measurement of vegetation area index underestimated vegetation area index at least in Scots pine stands defoliated less than 60%. The multivariate regression models were developed using tree diameter at breast height and tree crown defoliation ranges to estimate needle surface area. Keywords: Pinus sylvestris, crown defoliation, needle area index, regression model