Crowns of trees neighboring a strip road are exposed to greater amounts of sunlight, which may result in the so-called edge effect, leading to enhanced tree growth. The aim of this study was to assess the edge effect after twenty years since the clearing of strip roads in terms of diameter at breast height (DBH), tree height, crown base height, and crown length. Based on the results of earlier measurements, temporal changes in tree diameters at strip roads were also evaluated. The analyses were conducted in a pine stand, where strip roads 3.5 m or 2.5 m wide had been cleared at a stand age of 31 years, and after eight years the width of the narrow strip roads had been increased to 3.5 m. Measurements were taken on trees growing immediately adjacent to strip roads (edge trees) and those approximately 4.5 m from the road axis, as well as those in the middle of the distance between neighboring strip roads (as a reference). Trees growing at the edge of strip roads had statistically significantly larger diameters at breast height than trees growing farther from strip roads. The differences in tree height were slight and statistically non-significant, whereas the crowns of trees growing at the edges of strip roads had lower bases and were longer than the crowns of other trees. Analysis of DBH data recorded from measurements over 20 years showed a gradual reduction in the effect of strip roads on the diameters of trees growing at their edges.

The issue of water and wind erosion of soil remains critically important. Polymeric materials offer a promising solution to this problem. In this study, we prepared and applied an interpolyelectrolyte complex (IPEC) composed of the biopolymers chitosan and sodium carboxymethyl cellulose (Na-CMC) for the structuring of forest sandy soils and the enhancement of the pre-sowing treatment of Scots pine (Pinus sylvestris L.) seeds. A nonstoichiometric IPEC [Chitosan]:[Na-CMC] = [3:7] was synthesized, and its composition was determined using gravimetry, turbidimetry, and rheoviscosimetry methods. Soil surface treatment with IPEC involved the sequential application of a chitosan polycation (0.006% w/w) and Na-CMC polyanion (0.02% w/w) relative to the air-dry soil weight. The prepared IPEC increased soil moisture by 77%, extended water retention time by sixfold, doubled the content of agronomically valuable soil fractions > 0.25 mm, enhanced soil resistance to water erosion by 64% and wind erosion by 81%, and improved the mechanical strength of the soil-polymer crust by 17.5 times. Additionally, IPEC application resulted in slight increases in the content of humus, mobile potassium, mobile phosphorus, ammonium nitrogen, and mineral salts in the soil while maintaining soil solution pH stability and significantly increasing nitrate nitrogen levels. The novel application technologies of biopolymers and IPEC led to a 16-25% improvement in Scots pine seed germination and seedling growth metrics.

The forest regeneration phase in Sweden commonly involves mechanical soil preparation followed by the planting of Scots pine (Pinus sylvestris L.) or Norway spruce (Picea abies (L.) Karst) seedlings. The prepared soil offers planting positions with different properties, including reduced damage by pine weevils (Hylobius abietis L.). Nitrogen fertilization can be applied at the time of planting to aid establishment of the seedlings. In this study, we compared the effects of different planting positions, organic nitrogen fertilization, and different seedling sizes on the early survival and growth of Scots pine and Norway spruce seedlings. The main planting positions were capped mound, hinge, and mineral soil. Seedlings planted close to organic material were categorized as being in low-quality positions, since proximity to organic material increases pine weevil attraction. Higher mortality rates related to pine weevil damage were recorded for the seedlings planted in the low-quality positions, regardless of seedling size or N fertilization. Pine weevil attack rates increased with increasing seedling size. Growth was, in general, lowest in the mineral soil positions. The effect of organic N fertilization on growth was positive for the spruce regardless of the planting position or seedling size, while it depended on the planting position and seedling size for the pine, indicating that the effects of organic N fertilization depend on the seedling species, seedling size, and planting position.

The growth peculiarities of Scots pine ( Pinus sylvestris L.) have been studied by the example of an even-aged pine stand of high density. A long-term research has been conducted on a permanent sample plot. The data has been collected from the stand aged from 37 to 55 years. The characteristics of individual trees and the entire stand during the growth period in the absence of external influences (cutting, windfalls, pest damage, etc.) and after improvement cuttings have been analyzed. The influence of the amount of resource available to a tree on the formation of crowns, root systems and stem wood has been investigated. The size of the available resource has been the square of the dominance area. The root system of the pine trees of the studied stands is compact in size and, despite the high stand density, due to the high content of nutrients in the soil and the absence of moisture deficiency, it sufficiently ensures intensive tree growth corresponding to the conditions of the I quality class. It has been found that under these conditions, the average area of the root system is proportional to the average square of the dominance area. It has been shown that the stem diameter at a height of 1.3 m in the absence of external influences significantly depends on the square of the dominance area. The correlation coefficient of these indicators for the studied stand at the age of 37 is 0.89. The influence of cuttings on annual radial increment has been studied using dendrochronology methods. It has been revealed that in the year following the cutting, it has increased by 1.3-2.0 times, depending on the increase in the square of the dominance area. A method has been proposed for calculating the competition coefficient as a share of the resource required for the free growth of a tree, which is redistributed between its closest neighbours. Long-term observations have shown that with competition coefficients exceeding 0.6-0.7, the stem diameter increment rate decreases significantly, and the trees develop a sparse crown extending less than 40 % of the tree height. This, in turn, leads to growth retardation and a transition to a depressed state. This, in turn, leads to growth retardation and a transition to a depressed state.

Climate change is projected to increase the frequency and severity of droughts, possibly causing sudden and elevated tree mortality. Better understanding and predictions of boreal forest responses to climate change are needed to efficiently adapt forest management. We used tree-ring width chronologies from the Swedish National Forest Inventory, sampled between 2010 and 2018, and a random forest machine-learning algorithm to identify the tree, stand, and site variables that determine drought damage risk, and to predict their future spatial-temporal evolution. The dataset consisted of 16,455 cores of Norway spruce, Scots pine, and birch trees from all over Sweden. The risk of drought damage was calculated as the probability of growth anomaly occurrence caused by past drought events during 1960-2010. We used the block cross-validation method to compute model predictions for drought damage risk under current climate and climate predicted for 2040-2070 under the RCP.2.6, RCP.4.5, and RCP.8.5 emission scenarios. We found local climatic variables to be the most important predictors, although stand competition also affects drought damage risk. Norway spruce is currently the most susceptible species to drought in southern Sweden. This species currently faces high vulnerability in 28% of the country and future increases in spring temperatures would greatly increase this area to almost half of the total area of Sweden. Warmer annual temperatures will also increase the current forested area where birch suffers from drought, especially in northern and central Sweden. In contrast, for Scots pine, drought damage coincided with cold winter and early-spring temperatures. Consequently, the current area with high drought damage risk would decrease in a future warmer climate for Scots pine. We suggest active selection of tree species, promoting the right species mixtures and thinning to reduce tree competition as promising strategies for adapting boreal forests to future droughts.

Boreal forests are facing profound changes in their growth environment, including warming-induced water deficits, extended growing seasons, accelerated snowmelt, and permafrost thaw. The influence of warming on trees varies regionally, but in most boreal forests studied to date, tree growth has been found to be negatively affected by increasing temperatures. Here, we used a network of Pinus sylvestris tree-ring collections spanning a wide climate gradient the southern end of the boreal forest in Asia to assess their response to climate change for the period 1958-2014. Contrary to findings in other boreal regions, we found that previously negative effects of temperature on tree growth turned positive in the northern portion of the study network after the onset of rapid warming. Trees in the drier portion did not show this reversal in their climatic response during the period of rapid warming. Abundant water availability during the growing season, particularly in the early to mid-growing season (May-July), is key to the reversal of tree sensitivity to climate. Advancement in the onset of growth appears to allow trees to take advantage of snowmelt water, such that tree growth increases with increasing temperatures during the rapidly warming period. The region's monsoonal climate delivers limited precipitation during the early growing season, and thus snowmelt likely covers the water deficit so trees are less stressed from the onset of earlier growth. Our results indicate that the growth response of P. sylvestris to increasing temperatures strongly related to increased early season water availability. Hence, boreal forests with sufficient water available during crucial parts of the growing season might be more able to withstand or even increase growth during periods of rising temperatures. We suspect that other regions of the boreal forest may be affected by similar dynamics.

The relationships between climate (January and July temperatures, annual precipitation, and a relative moisture index) and the number of foci and intensity of the needle cast disease caused by fungi from the genus Lophodermium Chevall. in the Scots pine nurseries and provenance trials in Krasnoyarsk krai have been studied using multivariate statistics methods. It is found that peaks in the disease occurrence are related to the warm and humid weather conditions. Bioclimatic models of the needle cast ranges have been built using the climate variables; the spatial dynamics of the disease occurrence have been projected under various scenarios of climate warming over the 21st century. Model experiments have shown that the needle cast disease would shift northwards into the new regions in Krasnoyarsk krai, where the phytopathogen has not yet been registered in the nurseries. The largest forest areas exposed to needle cast disease are predicted to be at a high risk of outbreaks by 2020 under moderate climate warming. With a significant warming trend by 2080, potential risk areas will be reduced, because the pine expansion into the permafrost zone should be limited by slow thawing of its active layer.