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Tree mixture may increase stand productivity while forest tree density mostly negatively influence the tree growth. However, several research have indicated that the knowledge on the corelation between tree mixture and stand productivity is still limited. In this study, the relationships among tree mixture, stand type (i.e., even-aged versus uneven-aged), density and diameter increment of Kazdağı fir (Abies nordmanniana subsp. equi-trojani [Asch. & Sint. ex Boiss] Coode & Cullen) were examined. The research was conducted within the Ayancık Forest Management Directorate, Sinop Regional Directorate of Forestry. Four different stands were selected; a) uneven-aged fir stand, b) even-aged fir stand, c) unevenaged mixed fir-beech stand, and d) even-aged mixed fir-beech stand. Five-year diameter increment in these four different stand types was determined and compared. Random effects regression analysis was utilized to examine the influence of the mixture and tree density on the diameter increment. Statistical relationships were found among tree mixture, stand density and the diameter increment (p<0.05). Moreover, diameter increment varied among the stand types. [ABSTRACT FROM AUTHOR]

Research Highlights: In mixed stands, competitive and supportive relationships occur between trees, illustrated by their dendrometric characteristics. Background and Objectives: We investigated the effect of species composition on growth and yield in mixed beech–coniferous stands in the Romanian Carpathians. Materials and Methods: We selected sites with similar trophicity levels, as determined by the site mapping method. Under the same site conditions, we generated models to determine, for each species (spruce, fir, and beech), the main parameters of the site index, including mean height, dominant height, standing volume yield, and mean annual volume increment for different compositional species proportions (psp) and categories of proportions (i.e., low psp, between 10 and 50%, and high psp, ranging between 60 and 90%). Results: Overall, up to the age of 100 years, mixed stands with low psp had enhanced tree height growth, characterized by mean values 2.2% higher for spruce and 4.8% higher for fir and beech. Dominant height showed similar values, regardless of psp. Mixed stands in which the psp increased (i.e., psp > 50) were more productive, with the mean yield differences at the age of 100 years ranging from +1.7% (for fir) to +3.8% (for spruce and beech), increasing to +6% at 140 years. Conclusions: When setting management targets, the management of mixed forests should be based on an understanding of the relationship between the site, species ecological requirements, and their yield potential. Mixed stands can influence individual tree growth and stand yield through psp. [ABSTRACT FROM AUTHOR]

Woody debris (WD), including coarse woody debris (CWD) and fine woody debris (FWD), is an essential structural and functional component of forest ecosystems. This study was carried out in Caspian hardwood forest sites. In this study, the volume and composition of WD were inventoried by line intersect sampling and fixed area plot sampling in unmanaged and managed forests on 6 compartments (3 managed and 3 unmanaged). Estimates of the total volume of WD in managed and unmanaged forests ranged from 11.9 m3.ha-1 to 25.82 m3.ha-1, respectively. The results of independent t tests indicated that the amount of CWD in the unmanaged forests was significantly higher than CWD in the managed ones (t22, 0.05 = 2.64, P = 0.015). Also, the results of independent t tests indicated that the amount of FWD in the managed forests was significantly higher than FWD in unmanaged forests (t4, 0.05 = 5.07, P = 0.007). In the unmanaged forests, WD in decay classes 3, 4, and 5 accounted for 77% of the total WD volume, but in the managed forests, WD in decay classes 1 and 2 accounted for 87% of the total WD volume. The results suggest preserving the current unmanaged forests (protected forests) and maintaining the structural and functional integrity of woody debris.

The Loess Plateau in China constitutes an area short of soil nitrogen and organic carbon due to local land degradation induced by various factors (i.e. long term changes of land use, climate conditions, and soil properties). The present study aimed to examine the effects of species and land management by afforestation on tree N acquisition capacity and soil N and C availability in degraded soils of the Loess Plateau area. We quantified root N uptake of inorganic and organic N sources as well as soil N and C availability, both at the tree species (i.e. Robinia pseudoacacia L., Juglans regia L. and Pinus tabulaeformis Carr.) and the land management (i.e. arable vs. monoculture vs. mixed afforested stands) levels. Our results indicated that afforestation improved soil N and organic C availabilities compared to abandoned arable land ( p < 0.05). In particular, the presence of N 2 -fixing R. pseudoacacia enhanced root N concentrations (ca. 3.0 times) and soil NO 3 - (ca. 5.4 times), soil total N (ca. 1.9 times) and organic C (ca. 3.4 times) availabilities, but decreased soil NH 4 + (ca. −33%), microbial biomass carbon (ca. −74%) and nitrogen (ca. −54%) in the mixed stand compared to J. regia monoculture. Under the experimental conditions applied, the afforested trees preferred organic over inorganic N compounds as well as NO 3 − over NH 4 + ; J. regia in monoculture had a highest root amino acids N uptake capacities (i.e. 76.6 ± 7.7 nmol N (g fw) − 1 h −1 for glutamine, 90.3 ± 8.9 nmol N (g fw) − 1 h −1 for arginine) compared to other tree species whereas such high uptake capacities were largely repressed in the mixed stand with R. pseudoacacia . Thus, in the Loess Plateau area, the inter-planting system of J. regia with N 2 -fixing R. pseudoacacia could improve the total soil N and organic C pools as well as plant N cycling compared to traditional arable land use and J. regia monoculture system. This study shows that inter-planting R. pseudoacacia with economic fruit trees can be considered a successful strategy for soil regeneration by afforestation in future land management projects. [ABSTRACT FROM AUTHOR]

The analysis, study and simulation of pure and/or mixed stand structure represent a particularly important problem in the forest management planning process, and respectively in the sustainable potential forest wood's administration, management and exploitation.The stand's structure characterizes the composition, organization and functioning preferably of the tree storey with major implications on other parts of the forestry phytocoenosis and thus on forest ecosystems overall.Silvotechnics interventions are directly related to the stands structure, as a result the complex stand structure - silvotechnics intervention-forestry strategy is defining for the integrated forest management, related to the national forest stock, regardless of the type of ownership and administration.Currently there are possibilities to study, analyze and simulate various types of stands structure, using for this purpose the mathematical modelling, which in the present paper is based on splines and algorithms, for whose implementation we used MATLAB programming environment. In the conducted case study it was examined and analyzed the structure of a stand mixture consisting of spruce and beech species, using mathematical models with cubic splines interpolating the experimental data and using the interpolation results for simulating the corresponding normal probability distribution function. The results led to the conclusions and relevant recommendations to current practical activities (needed silvotechnics interventions) done in these stands. [ABSTRACT FROM AUTHOR]

The work presents analysis of volume and structure of timber resources in mountain mixed forest stands managed according to Swiss irregular cutting system. Research material consist of results of trees measurements on 413 control sample plots located in square net with the length of side 100 m in "Szczawiczne" object in Forest Experimental Station in Krynica. The results include analysis of tree measurements carried out in year 1975 and repeated in following years: 1986, 1994, 2001,2006 and 2011. Calculations were performed for 16 interpretation units created by joining together stands with the same species composition category and phase of stand development with total area of 455,86 ha. The work presents analysis of changes of volume and structure of timber resources in mountain mixed forest stands managed according to Swiss irregular cutting system. The study was conducted in stands of "Szczawiczne" object in Forest Experimental Station in Krynica. Research material consist of results of trees measurements on 413 control sample plots located in square net with the length of side 100 m in "Szczawiczne" object in Forest Experimental Station in Krynica. The results include analysis of tree measurements carried out from year 1975 and repeated in following years: 1986, 1994, 2001, 2006 and 2011. Calculations stand volume were performed for 16 interpretation units created by joining together stands with the same species composition category and the phase of stand development with total area 455,86 ha. On the basic of obtained results following conclusions were formulated. In analyzed stands there were observed significant changes of forest resources favorable from economic as well as natural point of view. The progress of target species such as: fir and beech and regress of forecrop species such: pine, spruce and alder were observed. Mean stand volume in "Szczawiczne" almost doubled from level of 147 to 284 m³ x ha-1. The biggest increase of volume occurred in Silver fir stands the smallest in forecrop stands. In Scots pine stands in terminal phase of development volume decreased. The volume increment doubled in average from the level of 5,92 m³ x ha-1 x year-1 in first period to about 11,93 m³ x ha-1 x year-1 in the last period. In years 2006-2016 Silver fir stands had the biggest volume increment (about 16,04 m³ x ha-1 x year-1). [ABSTRACT FROM AUTHOR]

The aim of this study was to compare increment in mixed stands to the respective pure stands adopting, as an example, mixed stands comprising Norway spruce ( Picea abies [L.] Karst.) and European beech ( Fagus sylvatica L.). Using data from two mixed stand age series, in the Solling and in Harz Mountains, first we investigated whether the growth reduction effect arising from competing trees is dependent on the species of the competitors. We than explored whether increment predictions from the forest growth simulation package TreeGrOSS revealed differences between pure and mixed stands and, if so, what factors play a role and what may cause these increment differences. The analysis was based on a simulated trial series in which the parameters such as percentage mixture, age, site quality class, and stocking level were varied. The results indicate that neighboring Norway spruce restrict the basal area increment of both European beech and Norway spruce more than European beech competitors with the same crown cross-sectional area. In the majority of cases, the simulation produced an increment gain in mixed stands compared with pure stands. The amount of increment gain in a mixed stand depended on the percentage mixture, age, site quality class, and stocking level and could be related to changes in stand structure and their effects on aboveground competition. [ABSTRACT FROM AUTHOR]

Woody debris (WD), including coarse woody debris (CWD) and fine woody debris (FWD), is an essential structural and functional component of forest ecosystems. This study was carried out in Caspian hardwood forest sites. In this study, the volume and composition of WD were inventoried by line intersect sampling and fixed area plot sampling in unmanaged and managed forests on 6 compartments (3 managed and 3 unmanaged). Estimates of the total volume of WD in managed and unmanaged forests ranged from 11.9 m³.ha-1 to 25.82 m³.ha-1, respectively. The results of independent t tests indicated that the amount of CWD in the unmanaged forests was significantly higher than CWD in the managed ones (t22, 0.05 = 2.64, P = 0.015). Also, the results of independent t tests indicated that the amount of FWD in the managed forests was significantly higher than FWD in unmanaged forests (t4, 0.05 = 5.07, P = 0.007). In the unmanaged forests, WD in decay classes 3, 4, and 5 accounted for 77% of the total WD volume, but in the managed forests, WD in decay classes 1 and 2 accounted for 87% of the total WD volume. The results suggest preserving the current unmanaged forests (protected forests) and maintaining the structural and functional integrity of woody debris. [ABSTRACT FROM AUTHOR]

• Context: Light availability in forest understory is essential for many processes; it is, therefore, a valuable information regarding forest management. However, its estimation is often difficult and direct measurements are tedious. Models can be used to compute understory light, but they often require a lot of field data to accurately predict light distribution, particularly in the case of heterogeneous canopies. • Aims: The influence of the precision level of crown description was studied with a model (MμSLIM) that can be used with both detailed and coarse parameterization with the aim of reducing field data requirements to a minimum. • Methods: We analyzed the deterioration of the prediction quality of light distribution to the reduction of inputs by comparing simulations to transmitted light measurements in forests of increasing complexity in three different locations. • Results: With a full set of parameters to describe the tree crown (i.e., crown extension in at least eight directions, crown height and length), the model accurately simulated the light distribution. Simplifying crown description by a geometric shape with a mean radius of crown extension led to deteriorated but acceptable light distributions. Allometric relationships used to calculate crown extension from trunk diameter at breast height seriously reduced light distribution accuracy. [ABSTRACT FROM AUTHOR]

We conducted dendroecological analyses in 80-year-long tree ring chronologies to detect neighborhood effects (competition intensity, species identity) on the δC signature of tree rings and radial stem increment of Fagus sylvatica trees growing either in monospecific or mixed patches of a temperate forest. We hypothesized that tree ring δC is a more sensitive indicator of neighborhood effects and the impact of climate variability on growth than is ring width. We found a closer correlation of summer precipitation to δC than to ring width. While the ring width showed a decline over the test period (1926-2005), the mean curve of δC increased until the mid of the 1970s, remained high until about 1990, and markedly decreased thereafter. Possible explanations related to ontogeny and environmental change ('age effect' due to canopy closure; elevated atmospheric SO concentrations in the 1960s-1980s) are discussed. Beech target trees surrounded by many allospecific trees had a significantly lower mean δC in the period 1926-1975 than beech with predominantly or exclusively conspecific neighborhood, possibly indicating a more favorable water supply of beech in diverse stands. Contrary to expectation, trees subject to more intense competition by neighboring trees (measured by Hegyi's competition index) had lower δC values in their tree rings, which is thought to reflect denser canopies being linked to increased shading. We conclude that tree ring δC time series represent combined archives of climate variability, stand history and neighborhood effects on tree physiology and growth that may add valuable information to that obtained from conventional tree ring analysis. [ABSTRACT FROM AUTHOR]

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The deadwood (DW) of the forest is in the following two forms: standing (snag) and fallen (log). The DW categories and decay stage are important functional and structural components of forest ecosystems. We used a field-based assessment to quantify how the relative contribution of deadwood to total above-ground carbon stock changes across a silvicultural method and stand altitude gradient in mixed broadleaves stands. The characteristics of DW and carbon stock in selection-cutting managed stands (Sc), shelter-wood managed stands (Sh) and protected stands (Pr) were examined in three altitude ranges (low, <600; medium, 600–1200; and high, >1200 m a.s.l.) in a mixed broadleaves high forest. The results showed that with increasing altitude, the volume of DW increased. The volume of DW in Pr stands was about three times higher than Sh stands and twice higher than Sc stands. The volume of the standing DW was greater than that of the fallen DW in all stands. The highest volume ratio of fallen DW to standing DW was found in the medium altitude in the Sc stand. The amount of carbon stock by DW in the Sh, Sc, and Pr stands was 1.53–2.22, 2.29–3.19, and 5.03–6.80 t ha−1, respectively. The DW share of C-stock of above ground biomass was 4%–4.6% in Sh stand, 4.3%–4.8% in Sc stand, and 7.4%–7.9% in the Pr stand. Deadwood assessment and management, in terms of volume, type, species composition, diameter distribution, spatial allocation and decay stage, is one of the new challenges for a proper sustainable forest management. [ABSTRACT FROM AUTHOR]