Effect of canopy gap size and ecological factors on species diversity and beech seedlings in managed beech stands in Hyrcanian forests

We studied the species diversity of the herb layer and ecological factors in harvest-created gaps in beech stands under a single-tree selection system in Northern Iran. To determine diversity, the number of beech seedlings, and other ecological factors, 16 gaps were selected and subplots of 5 m2 were positioned at the centre and at the cardinal points of each gap. Species richness and Simpson diversity index increased with increasing gap area as did numbers of seedlings. With increasing humus layer thickness, species richness declined but the Hill evenness index increased. Species richness increased with increasing light availability. There was no relationship between crown radii of beech trees and diversity indices. Correlations between environmental factors and numbers of individuals of some species in the herb layer were not significant except in a few cases. The results help explain the effects of man-made gaps on the dynamics of managed beech stands and this benefits evaluation of silvicultural operating plans.

Mixed-effects modeling for tree height prediction models of Oriental beech in the Hyrcanian forests

Height–diameter relationships are essential elements of forest assessment and modeling efforts.In this work,two linear and eighteen nonlinear height–diameter equations were evaluated to find a local model for Oriental beech（Fagus orientalis Lipsky） in the Hyrcanian Forest in Iran.The predictive performance of these models was first assessed by different evaluation criteria： adjusted R^2（R^2_（adj））,root mean square error（RMSE）,relative RMSE（%RMSE）,bias,and relative bias（%bias） criteria.The best model was selected for use as the base mixed-effects model.Random parameters for test plots were estimated with different tree selection options.Results show that the Chapman–Richards model had better predictive ability in terms of adj R^2（0.81）,RMSE（3.7 m）,%RMSE（12.9）,bias（0.8）,%Bias（2.79） than the other models.Furthermore,the calibration response,based on a selection of four trees from the sample plots,resulted in a reduction percentage for bias and RMSE of about 1.6–2.7%.Our results indicate that the calibrated model produced the most accurate results.

Spatial correlation of pit and mound topography with canopy gaps in a virgin mixed beech forest, northern Iran

In a reserved forest parcel in a virgin eastern Hyrcanian mixed beech forest,80 ha was surveyed to determine the pit and mound topography,canopy gaps and dead trees.The aim was to investigate the spatial patterns and correlation of pit and mound features with canopy gaps.Seventy-five canopy gaps and 61 pit and mound features were identified.The univariate first order nearest neighbor(R_(CE))and bivariate second order test(Ripley’s K)statistic were applied.R_(CE) statistics highlighted a general aggregation pattern for canopy gaps and pits and mounds,while pits and mounds alone were more clumped.Distances between canopy gaps were 130 m average,whereas distances between pit and mound features and dead trees were 60 and 78 m,respectively.Spatial positive correlation of canopy gaps with pits and mounds were observed with all distances.The result of spatial correlations between canopy gaps with pits and mounds confirmed that windthrows cause micro successions in fallen tree ecosystem-scale correlated with gap phase dynamics in the forest community-scale.

Drought can favour the growth of small in relation to tall trees in mature stands of Norway spruce and European beech

Background: Climate change triggered many studies showing that trends and events of environmental conditions can reduce but also accelerate growth at the stand and individual tree level. However, it is still rather unknown how climate change modifies the growth partitioning between the trees in forest stands.Methods: Based on long-term girth-tape measurements in mature monospecific and mixed-species stands of Norway spruce(Picea abies(L.) Karst.) and European beech(Fagus sylvatica L.) we traced the effect of the severe droughts in 2003 and 2015 from the stand down to the tree level.Results: Stand growth of Norway spruce decreased by about 30% in the once-in-a-century drought 2015, while European beech was much more drought resistant. Water availability generally amplified size-asymmetric growth partitioning. Especially in case of Norway spruce water availability primarily fostered the growth of predominant trees, whereas drought favoured the growth of small trees at the expense of the predominant ones. We could not detect significant differences between mixed and monospecific stands in this regard.Conclusions: The drought-induced reallocation of growth in favour of small trees in case of spruce may result from its isohydric character. We hypothesize that as small trees are shaded, they can benefit from the reduced water consumption of their sun-exposed taller neighbours. In case of beech, as an anisohydric species, tall trees suffer less and smaller trees benefit less under drought. The discussion elaborates the consequences of the water dependent growth allocation for forest monitoring, growth modelling, and silviculture.

Effect of livestock grazing and human uses on herbaceous species diversity in oriental beech(Fagus orientalis Lipsky) forests, Guilan, Masal, northern Iran

Plant diversity plays key ecological roles in forest ecosystems, including influencing succession, resilience and nutrient cycling. This study was conducted to investigate the effect of livestock grazing and human uses on herbaceous species diversity. We surveyed 50 ha of protected area and 50 ha of unprotected area to evaluate herbaceous species diversity in oriental beech （Fagus orientalis Lipsky） forests in northern Iran. We calculated and compared three indices each of diversity and evenness, and species richness between the two areas. Herbaceous cover was higher in the unprotected area while leaf litter depth and tree canopy cover were higher in the protected area. The diversity indices, H （Shan- non-Wiener index ）, N~ （McArthur index）, N2 （Hill＇s index）, EQ （Modified Nee index）, E,ar （Smith-Wilson index）, E5 （modified index of Hill） and R=S （species richness） and species richness R=S were greater in the protected area than in the unprotected area, suggesting that protection from grazing results in increased numbers of plants and species. The effect of land protection on plant diversity was more pronounced for evenness than for species richness and the positive correlation between diversity and evenness indices was higher than that between diversity and richness.

Forest structure and woody plant species composition after a wildfire in beech forests in the north of Iran

Beech （Fagus orientalis Lipsky） forest covers about 565,000 ha of land in Guilan province, north of Iran and forms a major carbon pool. It is an important economic, soil protection and recreation resource. We studied long-term effects of fire on the structure and composition 37 years after fire occurrence in these forests. To do this research, we selected 85 ha burned and 85 ha unburned beech forests）. The results indicated that the fire had not changed the overall uneven-aged structure, but it changed forest composition from pure stands to mixed stands that now include species such as Carpinus betulus, Acer cappadocicum and Alnus subcordata. The density of trees and regeneration was significantly increased, while the density of shrubs significantly decreased. The main reasons for increased tree regeneration were attributed to （1） reduction of litter depth, and （2） increase in available light from opening of the canopy and reduction in shrub competition. It is apparent that the forest is on a path to return to its natural state before the fire after 37 years.

Natural regeneration of oriental beech(Fagus orientalis Lipsky)trees in canopy gaps and under closed canopy in a forest in northern Iran

For developing nature-based silvicultural practices in a beech forest to promote, abundance, height, vitality, and preferred growth form, regenerated trees growing in gaps were compared with those under closed canopies. A systematic 50 ×50 m grid was plotted in a beech stand in the Kheyrud Experimental Forest for selecting trees to measure variables in gaps and under closed canopies. Abundance and mean height of regenerated beech trees were significantly higher in closed canopies than in canopy gaps. Beech seedlings with excurrent growth were significantly taller within regeneration patches under closed canopy. Moreover, regenerated trees with high vitality were more abundant in closed canopy areas than in gaps. Thus, beech regeneration should improve under closed canopies; hence, gaps in a near natural forest should be created only after adequate regeneration and appropriate growth under the parent tree in a closed canopy area is ensured. The results of this research have profound implications for the sustainable management of the forest and for ensuring sustainable beech regeneration. The presence of a closed canopy cover likely will reduce potential stresses on oriental beech regeneration.

Study of the Single Shear Performance of a Joint with a New Beech and Self-Tapping Screw Composite Dowel

A new beech and self-tapping screw composite dowel is proposed and studied,its performance being compared with that of beech dowels and self-tapping screws alone.The single shear performance of components connected by composite dowels was tested.Results show that the dowels are a good choice for components requiring high stiffness.Screws remain a good choice for components requiring excellent seismic performance.Combination group presents similar maximum load stiffness to those of composite dowels,but other ductility parameters are superior for composite dowels.The best connection mode was provided by two composite dowels.Based on connecting two points,structural elements with two composite dowels showed much better load bearing ability than when joined by two beech dowels or by two self-tapping screws separately.The structural element with two composite dowels not only presented better initial stiffness,but also exhibited a better ductility coeffi-cient and less energy consumption.So,the composite dowels can be used for beam column connection,dowel laminated timber,and restoration or enhancement of ancient buildings.

Effects of thinning on stand structure and tree stability in an afforested oriental beech(Fagus orientalis Lipsky) stand in northeast Turkey

We studied relationships between stand structure and stand stability according to thinning intensity in an afforested oriental beech stand. Various thinning intensities were applied in sample stands. We sampled eight plots in stands that were lightly thinned, eight plots in heavily thinned stands and eight plots in unthinned stands as a control. Height and diameter distributions of the stands were measured to assess stand structure. We quantified individual tree stability and collective stability. Heavy thinning during the first thinning operation damaged the storied structure of the stand in thicket stage and affected collective structuring ability. While most control plots had multi-storied stands, after light and heavy thinning two-storied structure became more common.Large gaps occurred in the canopy after heavy thinning. On average, nine tree collectives were formed per sampling plot in the untreated stand, seven collectives after thinning in 2008 and four collectives after thinning in 2009. Stable trees accounted for 17 % of trees in control plots, 24 % in lightly thinned plots, and 15 % in heavily thinned plots. Collective stability values were 83 % in control plots, 82 % in lightly thinned plots and 36 % in heavily thinned plots. We conclude that it is necessary to retain collective structuring capacity during thinning operations for sustaining stand stability.

Distribution of stem decay in the beech trees of the Azerbaijan and its impact on the output of commercial wood

To determine the distribution of stem decay in the beech stands of Azerbaijan, we sought to identify the species, number, and height of attachment of fruiting bodies;the extent of decay in tree trunks growing under different conditions;and its influence on the trees’ commercial wood. The research was conducted on three farms representing the most common forest types of the Greater Caucasus within Azerbaijan. Examination of the presence of fruiting bodies in the tree trunk revealed that stem decay is the most common infection in beech (Fagus orientalis) stands, especially in fresh, moist areas, with less infection under dry growing conditions. In this work, the length, diameter, and volume of decay were studied by infecting the trunks of 93 model trees affected with mushrooms in 1–4 m cuttings. Our results showed that as the age of the stand increased, extent, diameter, and volume of decay increased significantly: the extent of decay from 1.47 to 6.43 m;the diameter of the decay from 8.15 to 32.7 cm;and the volume of decay from 2.5 to 13.2%. The relationship between age and the specified indicators is presented graphically. Using data obtained from the same sample of trees, we determined the expected and actual yield of commercial wood by age class. We determined that stem decay in beech stands leads to a decrease in the yield of commercial wood on average from 25.1% in the middle-aged to 14.8% in overmature plantations, respectively, with an estimated yield of 40.8–62.7%. Here we present mathematical models of the output of commercial wood from the infected part of the stands by age classes with the use of average data on the extent of decay in model trees.

Residual tree damage along skidding trails in beech stands in Greece

We studied the damage caused to unfelled trees during skidding operations in four beech stands of northern and central Greece that were managed under differing harvesting systems.After timber was harvested we recorded and analyzed all damage to a width of 2 m along both sides of the skid trails.The percentage of damaged residual trees was 17–28 %.Higher numbers of saplings were uprooted or destroyed in parts of the stands with high natural regeneration.Most damaged trees suffered 1.33–1.90 wounds that were inflicted up to a height of 1 m above ground level.At all sites mean wound sizes were large,89–1190 cm2,and caused elevated risk of future fungal infection.The damage caused by skidding during timber harvesting can be minimized by better planning the harvest operations,and training forest workers in reduced impact logging.

Long-term effect of fire on herbaceous species diversity in oriental beech (Fagus orientalis Lipsky) forests in northern Iran

We studied the long-term impacts of natural burning on herbaceous species diversity 37 years after a fire occurred in the Roudbar forests of Guilan Province, northern Iran. Numerous studies have examined short-term changes in understory vegetation following wildfire; however, very few long-term studies are available or changes inferred from retrospective studies based on chro- nosequences. For this study, 170 ha of forest （85 ha, burned areas; 85 ha, unburned areas） were surveyed. Because the 1000 m2 plots were too large for detailed measurements of herbaceous species, we determined a sub-sample size according to the Whittaker＇s nested plot sampling protocol and minimal areas method. Hence, sub-plots of 32 m2 were used for herbaceous species measurements, which consisted of percent cover of each species based on the Domin criterion. We measured plant diversity （Shannon-Wiener index）, spe- cies richness （Margalef＇s index）, and evenness （Smith-Wilson index）. Mean percent cover, together with diversity, richness and even- ness, increased markedly in burned areas compared to unburned controls. This suggests that the biodiversity of these forests could be restored within 37 years after fire. However, the abundance of invasive species such as Rubus fruticosus and Bromus benekenii increased significantly in burned areas, but these could be controlled by relevant silvicultural operations.

How do soil fauna and soil microbiota respond to beech forest growth?

The dynamics and performance of soil biota during forest rotation were studied in monoculture beech stands forming a chronosequence of four different age-classes(30,62,111,153 yr).Biomass was monitored in major groups of microflora,microfauna,mesofauna,and macrofauna.Resource availability(litter layer,soil organic mater),biomass of the two dominant decomposer groups(microflora,earthworms)as well as the biomass of mesofauna and microfauna were found to remain quite stable during forest succession.Nevertheless,the marked increase of the biomasses of primary decomposers(fungi,saprophagous macroinvertebrates)in the 62-year-old stand,followed by an increase of the biomasses of macropredators in the 111-year-old stand,indicate substantial changes of several components of edaphic communities during forest development.However,constant values of soil respiration suggest that the overall performance of the soil food web does not change during beech forest succession.Thus,the decomposer system of lowland managed beech forests on calcareous soils seems to be very stable over time.We suggest that earthworm activity might have masked impacts of forest development on other soil biota and led to an astounding stability of decomposer assemblages during beech forest rotation.

Drought events influence nutrient canopy exchanges and green leaf partitioning during senescence in a deciduous forest

The increase in the frequency and intensity of drought events expected in the coming decades in Western Europe may disturb forest biogeochemical cycles and create nutrient deficiencies in trees.One possible origin of nutrient deficiency is the disturbance of the partitioning of the green leaf pool during the leaf senescence period between resorption,foliar leaching and senesced leaves.However,the effects of drought events on this partitioning and the consequences for the maintenance of tree nutrition are poorly documented.An experiment in a beech forest in Meuse(France)was conducted to assess the effect of drought events on nutrient canopy exchanges and on the partitioning of the green leaf pool during the leaf senescence period.The aim was to identify potential nutritional consequences of droughts for trees.Monitoring nutrient dynamics,including resorption,chemistry of green and senesced leaves,foliar absorption and leaching in mature beech stands from 2012 to 2019 allowed us to compare the nutrient exchanges for three nondry and three dry years(i.e.,with an intense drought event during the growing season).During dry years,we observed a decrease by almost a third of the potassium(K)partitioning to resorption(i.e.resorption efficiency),thus reducing the K reserve in trees for the next growing season.This result suggests that with the increased drought frequency and intensity expected for the coming decades,there will be a risk of potassium deficiency in trees,as already observed in a rainfall exclusion experiment on the same study site.Reduced foliar leaching and higher parititioning to the senesced leaves for K and phosphorus(P)were also observed.In addition,a slight increase in nitrogen(N)resorption efficiency occurred during dry years which is more likely to improve tree nutrition.The calcium(Ca)negative resorption decreased,with no apparent consequence in our study site.Our results show that nutrient exchanges in the canopy and the partitioning of the green leaf pool can be modified by drought events,and may have consequences on tree nutrition.

Old coppice versus high forest:the impact of beech forest management on plant species diversity in central Apennines(italy)

Aims Silvicultural management plays a major role in shaping understory diversity through its action on stand structure.in many parts of Europe,recent socioeconomic changes have led to the progressive abandonment of coppicing in favor of high forest(HF)management.in order to examine how this change impacts understory species,we compared old coppice-with-standards and HF stands in terms of structural features and understory richness and composition,also taking into account the diagnostic species pool of the habitat.Since the management systems for coppices and HFs differ in cutting regime,we expect that they would cause different changes in floristic composition and richness.Methods The study area was the Montagne della Duchessa massif,in central italy.Structural differences and floristic richness were compared,and the diagnostic species diversity was analyzed using rarefaction curves and Rényi diversity profiles.Differences in understory com-position were analyzed through indicator species analysis.Important Findings Our results showed that,though the old coppices have a slightly higher number of understory species in general,the HF stands have greater mean species richness in both understory and diagnostic species,the latter being more evenly distributed inside the com-munity.These finding were related to the cut regime,which favor a constant canopy cover over time and thus the maintenance of more stable microclimatic conditions,promoting the higher abundance and evenness of shade-tolerant and vernal species.Conversely,the dense canopy of the old coppice appears to affect the understory richness by reducing the presence of light-demanding species,but still without a complete recolonization of the shade-tolerant spe-cies.Overall,our findings provide the first insights supporting that,in a Mediterranean montane context,old coppice conversion to HF could over time improve the species diversity in these habitats and help maintain good conservation status of the typical mature beech forests.

Optimization of Japanese beech hydrolysis treated with batch hot-compressed water by response surface methodology

In the present work,the combined effects of temperature and reaction time on hydrolysis of Japanese beech as treated by batch hot-compressed water were investigated by response surface methodology.A two-factor and three-level full factorial design was used for experimental design.The statistical models were established to configure the relationship between process conditions(temperature and reaction time)and water-soluble,saccharides from hemicelluloses(including arabinose,galactose,mannose,rhamnose,xylose and xylooligosaccharides)as well as decomposition compounds(5-HMF,furfural and organic acids).As a result of multiple response numerical optimization by applying desirability function method,the optimal hydrolysis conditions were obtained to be temperature of 200℃and reaction time of 3 min.At this optimum point,water-soluble,saccharides from hemicelluloses,5-HMF,furfural and organic acids were 31.5%,19.5%,0.28%,0.70%,and 0.59%,respectively.

Community structure of Lumbricidae in beech woodland of the Bieszczady National Park, Southeast Poland

As ecosystem engineers,earthworms play a key role in the soil environment.However,due to increasing anthropogenic pressure,soil organisms,including earthworms,are being threatened by habitat loss.In this study,we undertook a qualitative and quantitative investigation of earthworms of the family Lumbricidae in four types of Carpathian beech woodland(Fagetum carpaticum),characterized by their understory vegetation(I,F.c.festucetosum drymejae;Ⅱ,F.c.typicum;Ⅲ,F.c.lunarietosum;and IV,F.c.allietosum),in the Bieszczady National Park(Eastern Carpathians,Southeast Poland).At each investigated site,soil monoliths(25 cm×25 cm×25 cm)were examined by hand sorting.Earthworms were expelled from deep soil layers using a weak formalin solution(0.4%).Depending on the phytocoenosis,7 species of Lumbricidae were identified at each of the sites I,Ⅱ,andⅢand 10 at site IV.Site IV(F.c.allietosum)differed significantly(P<0.05)from the other three sites with respect to earthworm biomass(59.71±39.53 g m^(-2))and the Shannon-Wiener diversity index(0.52±0.12).Although present three decades ago,the deep-burrowing species Octodrilus transpadanus and the litter-dwelling species Dendrobaena octaedra were not found at site IV in the present study.We suspect that these two species may have been displaced by the invasive Lumbricus terrestris,which was not found at the same site in the 1980s.Such observations warrant further investigation to verify the predicted effects of an invasive earthworm,including the potential effects on soils and other fauna and flora,which have been documented in numerous countries.

Solubilization and Fractionation of Japanese Beech Wood with LiCl and DMSO

The solubility of beech wood cell wall in 8%lithium chloride/dimethyl sulfoxide(LiCl/DMSO)was investigated with an ethylenediamine(EDA)pretreatment without ball milling.EDA pretreatment of the wood cell wall was found to be an efficient method for the solubilization of the majority of the wood cell wall while avoiding the destructive effects of milling on the structure of the wood cell wall components.The yield of the final insoluble fraction was only approximately 31.6%based on the original Wiley wood sample after two EDA pretreatments and the dissolving processes.The solubility of lignocellulosic material in 8%LiCl/DMSO increased with decreasing lignin content after an EDA pretreatment.The yield of the insoluble fraction decreased from 62.9%to 9.2%with a decrease of lignin content from 28.0%to 14.1%.When the lignin content of lignocellulosic material was relatively low(approximately 10.5%),it could be dissolved in 8%LiCl/DMSO after an EDA pretreatment.The EDA pretreatment of wood meal had a much greater effect on polysaccharides than on the lignin in wood cell wall.