Stand Density Effects on Stem Diseases and Mortality in Spruce and Pine Forests

Incoming shortwave global radiation (Q g) and photosynthetically active radiation (PAR; Q pa as a fraction of full daylight, relative irradiance (%Q), were measured at the same time in young stands of Norway spruce (Picea abies (L.) Karst.) and Scots pine (Pinus sylvestris L.). Measurements were made on three levels above ground: 20 cm above ground and 50 and 15 % of stand height. Stands of three heights (75, 150 and 300 cm) were studied during two months. The stands were created by arranging young trees cut from natural stands, in nine quadratic spacings: 0.1, 0.2, 0.3, 0.4, 0.5, 0.7, 1.0, 1.4 and 2.0 m. The leaf area index (L) was estimated. Differences in %Q‐values for Q pa and Qg in the same species and at the same stand height and level of light measurements above ground were significant only in 150 and 300 cm stands. In 75 cm high stands of Scots pine, the %Q was <60% at spacings <0.2 m and in 75 cm high stands of Norway spruce, the %Q was <60% at spacings <0.3 m. Only at 0.1x0.1–0.3x0.3 m, %Q was <20% in Norway spruce stands. In 150 cm stands %Q<20% was measured at spacings <0.7 m in Norway spruce and <0.5 in Scots pine. In 300 cm stands of Norway spruce it was measured up to 1.2 and in Scots pine <1.1 m. Light extinction coefficients, K and Kg for spruce and pine stands were 0.17–0.40 and 0.16–0.31 respectively. Some practical implications of the study are presented. Lack of light (%Q<10%) as a single factor of seriously suppressed growth and development of broad‐leaved plants and suckers by competition in young stands of spruce and pine only occur in dense stands 0.3x0.3 m‐1.1xl.l m (8000–100000 stems/hectare). Competition by light on a regenerated area generally occurs in the level of 50% of tree height (150–300 cm) and higher due to the rapid growth of broad‐leaved trees (sprouts) compared with planted conifers but the light intensity at these levels %Q>10%.

In Lithuania, no studies have determined the relationship between the quality and economic benefits of Norway spruce and Scots pine wood based on age, stand density, and various forest management technologies. This study aims to assess and compare the economic benefits of Norway spruce and Scots pine in stands of different initial densities, depending on different forest management measures. This study calculated different pre-commercial thinning intensities 4 times, 3 times, and 2 times and final thinning profitability by stand volume and wood quality parameters modulus of elasticity and bending strength. Moreover, thinning intensities included three initial stand densities of 3000–3100, 2000–2100, and 1000–1100 trees per hectare, and different thinning regimes when the stand was thinned from below at the age of 8–9, 15, 21, and 35 years. The results showed higher profitability in the pre-commercial thinning of low-intensity with higher frequency − 4 thinning operations over the 40 years. However, the high-thinning intensity − 2 thinning operations over 40 years – applied in young Norway spruce and Scots pine stands will reduce wood quality and profitability in the future. The study found that stand thinning of low intensity tends to improve wood quality and the profitability that depends on it. After assessing the wood quality, it turned out that the 40-year-old Scots pine trees were too young to harvest because of low wood quality. However, the timber from Norway spruce trees could be used profitably if there is a market demand.

Background and Objectives: The aim of this study was to determine the effects of different stand densities on wood density (WD), global modulus of elasticity (MOE), and bending strength (MOR) in 35-year-old Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) H. Karst) stands, representing the hemiboreal forest zone. Materials and Methods: Scots pine and Norway spruce sites, representing different stand densities of 3000–3100; 2000–2100 and 1000–1100 trees per hectare, were chosen. Visually healthy model pine and spruce trees were selected, and diameter at breast height (DBH) was measured for model trees; the competition index was calculated; the MOE and MOR were evaluated by the Standards EN 408:2006 and EN 384:2016, at 12% moisture content; WD and the knot diameter were measured; and the strength class of wood was determined by the Standard EN 338:2009. To predict wood quality characteristics based on stand and tree characteristics, linear regression models were developed. Results and Conclusions: Higher stand density led to a significant change in the main wood properties of both conifer species. The highest mean WD, MOE, and MOR were obtained at the sites with the highest stand density. The MOE and MOR were highly correlated, but relatively weak correlations were found between MOE and MOR with tree DBH and WD. Despite the lower quality of Scots pine wood, the Norway spruce wood from more dense sites corresponded to the strength class of C16, according the strength grading of softwoods. The linear regression models did not perform well in describing the relationship of wood properties with stand and tree characteristics. The models for MOR accounted for the highest variation of 62–65% for both Scots pine and Norway spruce. These relationships can be expected to change with increased stand age or with the inclusion of specific crown parameters.

The effects of depth, size, location, and season of artificial logging damage on increment and decay of Norway spruce ( Picea abies (L.) Karst.) and Scots pine ( Pinus sylvestris L.) trees were studied in long-term experiments in central Finland. Damage types applied were root damage, root collar damage, increment borer hole, and stem damage. In root collar and stem damages, two sizes (100 or 400 cm2) and depths (shallow or deep) were applied. Five to 20 years after damaging, the damages did not result in a decrease in radial, height, or volume increment. In Norway spruce, the frequency of decay in the root collar and stem damages was high. From large and deep damages, decay spread faster than from smaller and shallow ones. In Scots pine, a lower proportion of trees were decayed compared with Norway spruce. Increment coring resulted in decay in most of the trees, but the decay spread slowly. The effect of compass direction or the month of damaging was negligible. The most common decay fungus in Norway spruce was Stereum sanguinolentum (Alb. &amp; Schwein. Fr.:) Fr. In Scots pine, only nondecay fungi were isolated. In general, logging damages decreased sawlog production through the rejection of butt logs containing decay or discoloration.

Butt rot incidence in the northernmost distribution area of Heterobasidion in Finland

Dissolved organic carbon and nitrogen leaching from Scots pine, Norway spruce and silver birch stands in southern Sweden

A process-based ecosystem model was used to assess the impacts of changing climate on net photosynthesis and total stem wood growth in relation to water availability in two unmanaged Norway spruce (Picea abies) dominant stands with a mixture of Scots pine (Pinus sylvestris) and birch (Betula sp.). The mixed stands were grown over a 100-year rotation (2000-99) in southern and northern Finland with initial species shares of 50, 25 and 25% for Norway spruce, Scots pine and birch, respectively. In addition, pure Norway spruce, Scots pine and birch stands were used as a comparison to identify whether species' response is different in mixed and pure stands. Soil type and moisture conditions (moderate drought) were expected to be the same at the beginning of the simulations irrespective of site location. Regardless of tree species, both annual net canopy photosynthesis (P(nc)) and total stem wood growth (V(s)) were, on average, lower on the southern site under the changing climate compared with the current climate (difference increasing toward the end of the rotation); the opposite was the case for the northern site. Regarding the stand water budget, evapotranspiration (E(T)) was higher under the changing climate regardless of site location. Transpiration and evaporation from the canopy affected water depletion the most. Norway spruce and birch accounted for most of the water depletion in mixed stands on both sites regardless of climatic condition. The annual soil water deficit (W(d)) was higher on the southern site under the changing climate. On the northern site, the situation was the opposite. According to our results, the growth of pure Norway spruce stands in southern Finland could be even lower than the growth of Norway spruce in mixed stands under the changing climate. The opposite was found for pure Scots pine and birch stands due to lower water depletion. This indicates that in the future the management should be properly adapted to climate change in order to sustain the productivity of mixed stands dominated by Norway spruce.

The selection of tree species is one factor to consider if we want to mitigate carbon dioxide emissions to the atmosphere through forest management. The objectives of this study were to estimate the differences in soil organic carbon (SOC) stocks under Norway spruce (Picea abies (L.) Karst.) and Scots pine (Pinus sylvestris L.) forests and to examine causes of differences in the accumulation of carbon in the forest soil. Large-scale inventory data was used to quantify variations in SOC stock in relation to stand type and the accumulation of carbon for spruce and pine stands was analysed by simulation. Based on field data, the national mean SOC stock was 9.2 kg m in spruce dominated stands and 5.7 kg m in pine dominated stands. For both species, the SOC stock, measured in the field inventory, increased significantly with increasing temperature, although at different rates. The SOC stock was larger for spruce under all temperature conditions, but the difference between species diminished with increasing temperature. The simulations indicated that the build-up of SOC over several rotations was 22% higher in spruce stands than in pine stands under similar environmental conditions. The main difference was found to be the greater input of harvest residues for spruce. Further, the simulations showed that ground vegetation contributed considerably more to the litter production under pine than under spruce. On sites where both Scots pine and Norway spruce are considered suitable, the latter should be selected if the aim of the forest management policy is to maximize the accumulation of SOC in the forest. Further, spruce is more favourable for SOC accumulation in areas with cold temperatures and on sites with low productivity.–2–2

In forests, the growth and productivity of individual trees and stands as a whole are regulated by stand density among other factors, because access to vital resources is limited by competition between trees. On 18 experimental plots of Scots pine (Pinus sylvestris L.) planted with a density of 500–128,000 trees/ha in the south taiga (Middle Siberia), interactions between stand density, tree- and stand-scale productivity, and tree-ring parameters were investigated. Tree-scale productivity variables, tree-ring width, and latewood width had stable negative allometric relationships with stand density (R2 &gt; 0.75), except for tree height (insignificant for inventory surveys at ages of 20 and 25 years; R2 &gt; 0.4 at the age of 35 years), while positive allometry was registered for stand productivity variables (R2 &gt; 0.7) and the all-time average latewood ratio (R2 = 0.5 with planting density). Tree-ring parameters aside from the age trends correlate (p &lt; 0.05) between the plots and demonstrate common responses to moderate moisture deficit. Although, its seasonality apparently depends on the resource base and intensity changes with stand density. February–June precipitation is more important for pine growth in dense stands, July–August conditions affect the latewood ratio stronger in sparse stands, and medium-density stands are more resistant to winter frosts.

Variations in fine root biomass of trees and understory in 16 stands throughout Finland were examined and relationships to site and stand characteristics determined. Norway spruce fine root biomass varied between 184 and 370 g m(-2), and that of Scots pine ranged between 149 and 386 g m(-2). In northern Finland, understory roots and rhizomes (< 2 mm diameter) accounted for up to 50% of the stand total fine root biomass. Therefore, the fine root biomass of trees plus understory was larger in northern Finland in stands of both tree species, resulting in a negative relationship between fine root biomass and the temperature sum and a positive relationship between fine root biomass and the carbon:nitrogen ratio of the soil organic layer. The foliage:fine root ratio varied between 2.1 and 6.4 for Norway spruce and between 0.8 and 2.2 for Scots pine. The ratio decreased for both Norway spruce and Scots pine from south to north, as well as from fertile to more infertile site types. The foliage:fine root ratio of Norway spruce was related to basal area and stem surface area. The strong positive correlations of these three parameters with fine root nitrogen concentration implies that more fine roots are needed to maintain a certain amount of foliage when nutrient availability is low. No significant relationships were found between stand parameters and fine root biomass at the stand level, but the relationships considerably improved when both fine root biomass and stand parameters were calculated for the mean tree in the stand. When the northern and southern sites were analyzed separately, fine root biomass per tree of both species was significantly correlated with basal area and stem surface area per tree. Basal area, stem surface area and stand density can be estimated accurately and easily. Thus, our results may have value in predicting fine root biomass at the tree and stand level in boreal Norway spruce and Scots pine forests.

Forest ecosystems are often defined by their dominant foundation tree species, which dictate forest structure and ecosystem processes. In southern Sweden, concerns are being raised because production stands of a foundation tree species, Scots pine (Pinus sylvestris), are being converted to Norway spruce (Picea abies) stands. Such conversions may lead to biodiversity loss, though the specific nature and extent of such losses remain unknown. Here, we assess the potential biodiversity impacts by contrasting the bird communities of 55- and 80-year-old Scots pine and Norway spruce production stands. We also determine the extent to which these production stands capture the available species pool by surveying conifer-dominated reserves. Our results indicate that Scots pine and Norway spruce production forests support overlapping but nevertheless distinct bird communities, though only few recordings were made of the species unique to either stand type. Among the production stands, the 80-year spruce stands had the highest average bird species richness, and largest total number of species recorded. We suggest that the higher diversity can be explained by a higher proportion of broadleaves and higher volumes of dead wood. Although the bird diversity found in the reserves was lower than expected, they benefit gamma diversity at landscape scales as they collectively supported a higher diversity of bird species than the production forests. In summary, the conversion of Scots pine to Norway spruce is likely to increase the homogeneity of the bird communities in this region.

Variability in short root morphology of the three main tree species of Europe's boreal forest (Norway spruce (Picea abies L. Karst.), Scots pine (Pinus sylvestris L.) and silver birch (Betula pendula Roth)) was investigated in four stands along a latitudinal gradient from northern Finland to southern Estonia. Silver birch and Scots pine were present in three stands and Norway spruce was present in all stands. For three fertile Norway spruce stands, fine root biomass and number of root tips per stand area or unit basal area were assessed from north to south. Principal component analysis indicated that short root morphology was significantly affected by tree species and site, which together explained 34.7% of the total variability. The range of variation in mean specific root area (SRA) was 51-74, 60-70 and 84-124 m(2) kg(-1) for Norway spruce, Scots pine and silver birch, respectively, and the corresponding ranges for specific root length were 37-47, 40-48 and 87-97 m g(-1). The range of variation in root tissue density of Norway spruce, Scots pine and silver birch was 113-182, 127-158 and 81-156 kg m(-3), respectively. Sensitivity of short root morphology to site conditions decreased in the order: Norway spruce > silver birch > Scots pine. Short root SRA increased with site fertility in all species. In Norway spruce, fine root biomass and number of root tips per m(2) decreased from north to south. The differences in morphological parameters among sites were significant but smaller than the site differences in fine root biomass and number of root tips.

Key messageTree structure equations derived from pipe model theory (PMT) are well-suited to estimate biomass allocation in Scots pine (Pinus sylvestrisL.) and Norway spruce (Picea abies[L.] Karst.). However, age dependence of parameters should be accounted for when applying the equations.ContextPipe model theory-based (PMT-based) structure equations have been incorporated in many process-based models. However, more data concerning old-growth trees is needed to test the reliability and generality of the structure equations.AimsThis study (1) tested the age independence of the PMT-based structure equations and (2) provided general information about the stability of tree structure with age.MethodsA total of 162 Scots pine and 163 Norway spruce trees in four age groups were analysed to test the age effect on the parameters of structure equations using a linear mixed model. Biomass of stem, branch and foliage was estimated from destructive measurements, and with other tree dimensions, they were used to present the tree growth patterns.Results(1) Stem biomass proportion increased with age, while branch and foliage biomass proportion decreased; biomass allocation and most tree variables became steady after maturing. (2) PMT-based structure equations were well-suited to Scots pine and Norway spruce in all age groups; however, age dependence was detected in the parameters of these equations, except for the branch-related equations in Scots pine and stem form coefficient below the crown base in both species.ConclusionOur study (1) provides information applicable to predictions of growth and biomass allocation in old boreal stands and (2) suggests taking age effect into account when structure equations are implemented in forest growth models.

SummarySpecimens of Heterobasidion annosum were collected in 104 different stands in 43 regions of Poland. Pure cultures originating from 439 collections were identified in mating tests. Three intersterility groups, P, S and F, of H. annosum were found. Their occurrence in Poland was connected with the natural distribution of the main hosts: Pinus sylvestris, Picea abies and Abies alba, respectively. P was the most common intersterility group of H. annosum in Poland, causing mortality in Scots pine plantations and root rot in older stands. It was also isolated from Betula pendula, P. abies, Larix decidua, Fagus sylvatica and Carpinus betulus. The S group was present in the southern and north‐eastern parts of the country, causing root and butt rot mostly in spruce stands. The F group occurred in the south of Poland, in the mountains, highlands and lowland up to the northern border of the distribution of fir. It was found only on stumps, old dead trees and logs. There was no evidence of damage caused by the F group on A. alba trees.

Variation in annual carbon fluxes affecting the SOC pool in hemiboreal coniferous forests in Estonia