Plant species diversity is one of the most widely used indicators in ecosystem management.The relation of species diversity with the size of the sample plot has not been fully determined for Oriental beech forests(Fag...Plant species diversity is one of the most widely used indicators in ecosystem management.The relation of species diversity with the size of the sample plot has not been fully determined for Oriental beech forests(Fagus orientalis Lipsky),a widespread species in the Hyrcanian region.Assessing the impacts of plot size on species diversity is fundamental for an ecosystem-based approach to forest management.This study determined the relation of species diversity and plot size by investigating species richness and abundance of both canopy and forest floor.Two hundred and fifty-six sample plots of 625 m^(2) each were layout in a grid pattern across 16 ha.Base plots(25 m×25 m)were integrated in different scales to investigate the effect of plot size on species diversity.The total included nine plots of 0.063,0.125,0.188,0.250,0.375,0.500,0.563,0.750 and 1 ha.Ten biodiversity indices were calculated.The results show that species richness in the different plot sizes was less than the actual value.The estimated value of the Simpson species diversity index was not significantly different from actual values for both canopy and forest floor diversity.The coefficient of variation of this index for the 1-ha sample plot showed the lowest amount across different plot sizes.Inverse Hill species diversity was insignificant difference across different plot sizes with an area greater than 0.500 ha.The modified Hill evenness index for the 1-ha sample size was a correct estimation of the 16-ha for both canopy and forest floor;however,the precision estimation was higher for the canopy layer.All plots greater than 0.250-ha provided an accurate estimation of the Camargo evenness index for forest floor species,but was inaccurate across different plot sizes for the canopy layer.The results indicate that the same plot size did not have the same effect across species diversity measurements.Our results show that correct estimation of species diversity measurements is related to the selection of appropriate indicators and plot size to increase the accuracy of the estimate so that the cost and time of biodiversity management may be reduced.展开更多
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 Orient...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.展开更多
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 seed...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.展开更多
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 ...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.展开更多
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 un...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.展开更多
Allocation of biomass and nutrient elements including Nitrogen to above and belowground compartments of beech seedlings （Fagus sylvatica L.） treated by labeled nitrogen fertilizer in the form of 15NH4 and 15NO3 were...Allocation of biomass and nutrient elements including Nitrogen to above and belowground compartments of beech seedlings （Fagus sylvatica L.） treated by labeled nitrogen fertilizer in the form of 15NH4 and 15NO3 were investigated at the end of two successive growing seasons. Pot cultured beech seedlings were grown at a green house on intact soil cores sampled from three adjacent stands including beech, Norway spruce and mixed beech-spruce cultures of Soiling forest, Germany. Comparing biomass allocation and nutrients concentrations of the seedlings between the control and 15N-fertilized treatments revealed no significant effect of N fertilization on nutrients uptake by seedlings over the experiment. The form of N input influenced its movement into plant pools. It was demonstrated that beech seedlings take up nitrogen mainly in the form of nitrate, which is then reduced in the leaves, although the differences between the retention of NO3^--N and NH4^＋-N in plants were not statistically significant. Percent recoveries of 15N in trees were typically greater after 15NO3 than after 15NH4 additions. It was indicated that immobilization of ~SN tracer in fine roots was a slower process comparing other plant compartments such as stem and coarse roots, but a powerful sink for N during the course of study.展开更多
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 use...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.展开更多
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 studie...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.展开更多
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 canopie...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.展开更多
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 ...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.展开更多
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 di...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.展开更多
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...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.展开更多
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 ch...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.展开更多
The partitioning of nitrogen deposition among forest soil （including forest floor）, leachate and above- and belowground biomass of pot cultured beech seedlings in comparison to non-cultured treatments were investiga...The partitioning of nitrogen deposition among forest soil （including forest floor）, leachate and above- and belowground biomass of pot cultured beech seedlings in comparison to non-cultured treatments were investigated by adding 1.92 g.m^-2 ^15N tracer in throughfall for two successive growing seasons at a greenhouse experiment. Ammonium and nitrate depositions were simulated on four treatments （cultured and non-cultured） and each treatment was labeled with either ^15N-NH4^＋ or ^15N-NO3^-. Total recovery rates of the applied ^15N in the whole system accounted for 74.9% to 67.3% after ^15N-NH4^＋ and 85.3% to 88.1% after ^15N-NO3^-in cultured and non-cultured treatments, respectively. The main sink for both ^15N tracers was the forest soil （including forest floor）, where 34.6% to 33.7% of ^15N-NH4^＋ and 13.1% to 9.0% of ^15N-NO3^-were found in cultured and non-cultured treatments, respectively, suggesting strong immobilization of both N forms by hetero- trophic microorganisms. Nitrogen immobilization by microorganisms in the forest soil （including forest floor） was three times higher when ^15N-NH4^＋ was applied compared to ^15N-NO3^-. The preferential heterotrophic use of ammonium resulted in a two times higher retention of deposited ^15N-NH4^＋ in the forest soil as compared to plants. In contrast, nitrate immobilization in the forest soil was lower compared to plants, although statistically it was not significantly different. In total the immobilization of ammonium in the plant-soil system was about 60% higher than nitrate, indicating the importance of the N-forms deposition for retention in forest ecosystems.展开更多
In this study,using a dendrological and isotopic approaches,we investigated the responses to climate of two pure Fagus sylvatica L.stands(Campobraca and Falode)in the southernmost part of the distribution range in sou...In this study,using a dendrological and isotopic approaches,we investigated the responses to climate of two pure Fagus sylvatica L.stands(Campobraca and Falode)in the southernmost part of the distribution range in southern Italy.Theδ^(13)C data were used for calculating the intrinsic water use efficiency(iWUE)as a proxy of the balance between the water and carbon cycles.The results showed that the iWUE of both stands was sensitive to the amount of precipitation during the summer months(negative,significant effect)and to atmospheric CO_(2)concentration.Growth was sensitive to climate only in the Campo Braca site;the most influential variables were the VPD(vapour pressure deficit)and precipitation of the summer months that had a negative and a positive effect,respectively.The iWUE showed a negative correlation with growth in Campo Braca and a non-significant one in Falode.Water availability was the most influential variable on F.sylvatica growth and physiology.The iWUE increase was mainly driven by atmospheric CO_(2)concentration,and by decreased precipitation,as a response of the trees to drought.Our results highlight the importance of understanding the hydrological changes due to climate change for forecasting/modelling forest responses.CO_(2)increase does not compensate for the effect of adverse climate on F.sylvatica in the forests of southern Italy,while local conditions play an important role in determining tree growth.展开更多
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 ...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.展开更多
Decaying wood is an essential element of forest ecosystems and it affects its other components.The aim of our research was to determine the decomposition rate of deadwood in various humidity and thermal conditions in ...Decaying wood is an essential element of forest ecosystems and it affects its other components.The aim of our research was to determine the decomposition rate of deadwood in various humidity and thermal conditions in the gaps formed in the montane forest stands.The research was carried out in the Babiog orski National Park.The research plots were marked out in the gaps of the stands,which were formed as a result of bark beetle gradation.Control plots were located in undisturbed stands.The research covered wood of two species–spruce and beech in the form of cubes with dimensions of 50 mm×50 mm×22 mm.Wood samples were placed directly on the soil surface and subjected to laboratory analysis after 36 months.A significant influence of the wood species and the study plot type on the physicochemical properties of the tested wood samples was found.Wood characteristics strongly correlated with soil moisture.A significantly higher mass decline of wood samples was recorded on the reference study plots,which were characterized by more stable moisture conditions.Poorer decomposition of wood in the gaps regardless of the species is related to lower moisture.The wood species covered by the study differed in the decomposition rate.Spruce wood samples were characterized by a significantly higher decomposition rate compared to beech wood samples.Our research has confirmed that disturbances that lead to the formation of gaps have a direct impact on the decomposition process of deadwood.展开更多
Trees are able to adapt to changing environmental conditions through modifications in their crown morphology and branch architecture.In light-limited environments,tree structures are mainly optimised to increase light...Trees are able to adapt to changing environmental conditions through modifications in their crown morphology and branch architecture.In light-limited environments,tree structures are mainly optimised to increase light interception.This might have side effects on other properties such as the hydraulic system that determines water conduction and tree reactions to drought events.Given the increasing exposure of forest ecosystems to drought stress it is thus crucial to investigate possible correlations between the crown morphology and branch architecture and drought responses.Our study aimed to compare different crown archetypes and branch characteristics of European beech(Fagus sylvatica L.)in their reaction to drought,which was assessed by measuring tree-ring widths of increment cores sampled at breast height.Using Terrestrial Laser Scanning and Quantitative Structure Models,we explored various crown morphological and branch architectural characteristics of 67 beech trees and identified three species-specific crown archetypes.The crown archetypes and branch variables were contrasted with growth responses using linear mixed models.While productivity levels differed,the negative impact of drought stress on radial growth was consistent across all crown archetypes.Nevertheless,certain branch architectural variables were important predictors for radial growth in drought situations.Specifically,long water conduction paths and many branching nodes along those paths were positively influencing growth.Our results indicate that trees showing these characteristics might have a competitive edge regarding drought-affected radial growth compared to others.They could be promoted through thinning measures,which would allow improving the adaption of existing beech forests in situ to climate change and drought stress.展开更多
In Central Europe,anthropogenic coniferous monocultures have been subject to conversion to more diverse mixed forests since the 1990s,however,they are still abundant across many forest landscapes.Artificial and natura...In Central Europe,anthropogenic coniferous monocultures have been subject to conversion to more diverse mixed forests since the 1990s,however,they are still abundant across many forest landscapes.Artificial and natural tree regeneration both play a key role during conversion by determining the species composition and structure of the future forests.Many abiotic and biotic factors can potentially influence the regeneration process and its specific combinations or interactions may be different among tree species and its developmental stages.Here,we aimed to identify and quantify the effect of the most important drivers on the density of the most abundant regenerating tree species(i.e.,Norway spruce and European beech),as well as on species and structural diversity of the tree regeneration.We studied tree regeneration in four former monospecific coniferous stand types(i.e.,Norway spruce,Scots pine,European larch,and Douglas fir)in Southwest Germany that have been under conversion to mixed forests since the 1990s.We sampled tree regeneration in four growth height classes together with a variety of potentially influencing factors on 108 sampling plots and applied multivariate analyses.We identified light availability in the understorey,stand structural attributes,browsing pressure,and diaspore source abundance as the most important factors for the density and diversity of tree regeneration.Particularly,we revealed speciesspecific differences in drivers of regeneration density.While spruce profited from increasing light availability and decreasing stand basal area,beech benefited either from a minor reduction or more strikingly from an increase in overstorey density.Increasing diaspore source abundance positively and a high browsing pressure negatively affected both species equally.Our results suggest that humus and topsoil properties were modified during conversion,probably due to changes in tree species composition and silvicultural activities.The species and structural diversity of the tree regeneration benefitted from increasing light availability,decreasing stand basal area,and a low to moderate browsing pressure.We conclude that forest managers may carefully equilibrate among the regulation of overstorey cover,stand basal area,and browsing pressure to fulfil the objectives of forest conversion,i.e.,establishing and safeguarding a diverse tree regeneration to promote the development of mature mixed forests in the future.展开更多
基金funded by Gorgan University of Agricultural Sciences and Natural Resources(grant number 9318124503).
文摘Plant species diversity is one of the most widely used indicators in ecosystem management.The relation of species diversity with the size of the sample plot has not been fully determined for Oriental beech forests(Fagus orientalis Lipsky),a widespread species in the Hyrcanian region.Assessing the impacts of plot size on species diversity is fundamental for an ecosystem-based approach to forest management.This study determined the relation of species diversity and plot size by investigating species richness and abundance of both canopy and forest floor.Two hundred and fifty-six sample plots of 625 m^(2) each were layout in a grid pattern across 16 ha.Base plots(25 m×25 m)were integrated in different scales to investigate the effect of plot size on species diversity.The total included nine plots of 0.063,0.125,0.188,0.250,0.375,0.500,0.563,0.750 and 1 ha.Ten biodiversity indices were calculated.The results show that species richness in the different plot sizes was less than the actual value.The estimated value of the Simpson species diversity index was not significantly different from actual values for both canopy and forest floor diversity.The coefficient of variation of this index for the 1-ha sample plot showed the lowest amount across different plot sizes.Inverse Hill species diversity was insignificant difference across different plot sizes with an area greater than 0.500 ha.The modified Hill evenness index for the 1-ha sample size was a correct estimation of the 16-ha for both canopy and forest floor;however,the precision estimation was higher for the canopy layer.All plots greater than 0.250-ha provided an accurate estimation of the Camargo evenness index for forest floor species,but was inaccurate across different plot sizes for the canopy layer.The results indicate that the same plot size did not have the same effect across species diversity measurements.Our results show that correct estimation of species diversity measurements is related to the selection of appropriate indicators and plot size to increase the accuracy of the estimate so that the cost and time of biodiversity management may be reduced.
基金This research received no specific grant from any funding agency in the public,commercial,or not-for-profit sectors
文摘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.
文摘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.
基金supported by Gorgan University of Agricultural Sciences and Natural Resources
文摘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.
基金European UnionAward Number 281116ERA02S+9 种基金Recipient:Hans PretzschProject Title:“Management of mixedspecies stands.Options for a low-risk forest management(REFORM)”Bayerisches Staatsministerium fur Ernahrung,Landwirtschaft und Forsten (Bavarian State Ministry for Nutrition,Agriculture,and Forestry)Award Number W07 7831–22209-2013Recipient:Hans PretzschProject Title:“Long-term experimental plots for forest growth and yield research”Deutsche Forschungsgemeinschaft (German Science Foundation)Award Number PR 292/12–1Recipient:Hans PretzschProject Title:“Tree and stand-level growth reactions on drought in mixed versus pure forests of Norway spruce and European beech”
文摘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.
基金supported by Institut für Bodenkunde und Waldernhrung,Georg-August-Universitt,Gttingen,Germany.
文摘Allocation of biomass and nutrient elements including Nitrogen to above and belowground compartments of beech seedlings （Fagus sylvatica L.） treated by labeled nitrogen fertilizer in the form of 15NH4 and 15NO3 were investigated at the end of two successive growing seasons. Pot cultured beech seedlings were grown at a green house on intact soil cores sampled from three adjacent stands including beech, Norway spruce and mixed beech-spruce cultures of Soiling forest, Germany. Comparing biomass allocation and nutrients concentrations of the seedlings between the control and 15N-fertilized treatments revealed no significant effect of N fertilization on nutrients uptake by seedlings over the experiment. The form of N input influenced its movement into plant pools. It was demonstrated that beech seedlings take up nitrogen mainly in the form of nitrate, which is then reduced in the leaves, although the differences between the retention of NO3^--N and NH4^＋-N in plants were not statistically significant. Percent recoveries of 15N in trees were typically greater after 15NO3 than after 15NH4 additions. It was indicated that immobilization of ~SN tracer in fine roots was a slower process comparing other plant compartments such as stem and coarse roots, but a powerful sink for N during the course of study.
文摘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.
文摘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.
文摘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.
基金supported by Karadeniz Technical University Research Fund,Project number 2010.113.001.11
文摘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.
基金‘‘Azerbaijan University of Architecture and Construction’’ and Ministry of Ecology and Natural Resources
文摘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.
文摘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.
文摘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.
基金supported by ibw, Goet-tingen University, Germany
文摘The partitioning of nitrogen deposition among forest soil （including forest floor）, leachate and above- and belowground biomass of pot cultured beech seedlings in comparison to non-cultured treatments were investigated by adding 1.92 g.m^-2 ^15N tracer in throughfall for two successive growing seasons at a greenhouse experiment. Ammonium and nitrate depositions were simulated on four treatments （cultured and non-cultured） and each treatment was labeled with either ^15N-NH4^＋ or ^15N-NO3^-. Total recovery rates of the applied ^15N in the whole system accounted for 74.9% to 67.3% after ^15N-NH4^＋ and 85.3% to 88.1% after ^15N-NO3^-in cultured and non-cultured treatments, respectively. The main sink for both ^15N tracers was the forest soil （including forest floor）, where 34.6% to 33.7% of ^15N-NH4^＋ and 13.1% to 9.0% of ^15N-NO3^-were found in cultured and non-cultured treatments, respectively, suggesting strong immobilization of both N forms by hetero- trophic microorganisms. Nitrogen immobilization by microorganisms in the forest soil （including forest floor） was three times higher when ^15N-NH4^＋ was applied compared to ^15N-NO3^-. The preferential heterotrophic use of ammonium resulted in a two times higher retention of deposited ^15N-NH4^＋ in the forest soil as compared to plants. In contrast, nitrate immobilization in the forest soil was lower compared to plants, although statistically it was not significantly different. In total the immobilization of ammonium in the plant-soil system was about 60% higher than nitrate, indicating the importance of the N-forms deposition for retention in forest ecosystems.
文摘In this study,using a dendrological and isotopic approaches,we investigated the responses to climate of two pure Fagus sylvatica L.stands(Campobraca and Falode)in the southernmost part of the distribution range in southern Italy.Theδ^(13)C data were used for calculating the intrinsic water use efficiency(iWUE)as a proxy of the balance between the water and carbon cycles.The results showed that the iWUE of both stands was sensitive to the amount of precipitation during the summer months(negative,significant effect)and to atmospheric CO_(2)concentration.Growth was sensitive to climate only in the Campo Braca site;the most influential variables were the VPD(vapour pressure deficit)and precipitation of the summer months that had a negative and a positive effect,respectively.The iWUE showed a negative correlation with growth in Campo Braca and a non-significant one in Falode.Water availability was the most influential variable on F.sylvatica growth and physiology.The iWUE increase was mainly driven by atmospheric CO_(2)concentration,and by decreased precipitation,as a response of the trees to drought.Our results highlight the importance of understanding the hydrological changes due to climate change for forecasting/modelling forest responses.CO_(2)increase does not compensate for the effect of adverse climate on F.sylvatica in the forests of southern Italy,while local conditions play an important role in determining tree growth.
基金supported by the Lorraine University of Excellence via the DEEPSURF project(ANR 70315-IDEX-04-LUE)。
文摘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.
基金financed by the National Science Centre,Poland:decision no.DEC 2020/39/B/NZ9/00372 and decision no.DEC-2021/43/O/NZ9/00066。
文摘Decaying wood is an essential element of forest ecosystems and it affects its other components.The aim of our research was to determine the decomposition rate of deadwood in various humidity and thermal conditions in the gaps formed in the montane forest stands.The research was carried out in the Babiog orski National Park.The research plots were marked out in the gaps of the stands,which were formed as a result of bark beetle gradation.Control plots were located in undisturbed stands.The research covered wood of two species–spruce and beech in the form of cubes with dimensions of 50 mm×50 mm×22 mm.Wood samples were placed directly on the soil surface and subjected to laboratory analysis after 36 months.A significant influence of the wood species and the study plot type on the physicochemical properties of the tested wood samples was found.Wood characteristics strongly correlated with soil moisture.A significantly higher mass decline of wood samples was recorded on the reference study plots,which were characterized by more stable moisture conditions.Poorer decomposition of wood in the gaps regardless of the species is related to lower moisture.The wood species covered by the study differed in the decomposition rate.Spruce wood samples were characterized by a significantly higher decomposition rate compared to beech wood samples.Our research has confirmed that disturbances that lead to the formation of gaps have a direct impact on the decomposition process of deadwood.
基金funding received from the Project“Hochaufgeloste Quanti fizierung des N ahrstoffentzuges bei verschiedenen Ernteszenarien der Buche”through the GFH Freiburg,which assisted with laser scanningsupported by the German Federal Ministry of Food and Agriculture and the Federal Ministry for the Environment,Nature Conservation,Nuclear Safety and Consumer Protection(grant:2219WK60C4)。
文摘Trees are able to adapt to changing environmental conditions through modifications in their crown morphology and branch architecture.In light-limited environments,tree structures are mainly optimised to increase light interception.This might have side effects on other properties such as the hydraulic system that determines water conduction and tree reactions to drought events.Given the increasing exposure of forest ecosystems to drought stress it is thus crucial to investigate possible correlations between the crown morphology and branch architecture and drought responses.Our study aimed to compare different crown archetypes and branch characteristics of European beech(Fagus sylvatica L.)in their reaction to drought,which was assessed by measuring tree-ring widths of increment cores sampled at breast height.Using Terrestrial Laser Scanning and Quantitative Structure Models,we explored various crown morphological and branch architectural characteristics of 67 beech trees and identified three species-specific crown archetypes.The crown archetypes and branch variables were contrasted with growth responses using linear mixed models.While productivity levels differed,the negative impact of drought stress on radial growth was consistent across all crown archetypes.Nevertheless,certain branch architectural variables were important predictors for radial growth in drought situations.Specifically,long water conduction paths and many branching nodes along those paths were positively influencing growth.Our results indicate that trees showing these characteristics might have a competitive edge regarding drought-affected radial growth compared to others.They could be promoted through thinning measures,which would allow improving the adaption of existing beech forests in situ to climate change and drought stress.
基金funded by the Bavarian Ministry for Food,Agriculture and Forestry (Grant No.F053)support by the Open Access Publication Funds/transformative agreements of the Gottingen University
文摘In Central Europe,anthropogenic coniferous monocultures have been subject to conversion to more diverse mixed forests since the 1990s,however,they are still abundant across many forest landscapes.Artificial and natural tree regeneration both play a key role during conversion by determining the species composition and structure of the future forests.Many abiotic and biotic factors can potentially influence the regeneration process and its specific combinations or interactions may be different among tree species and its developmental stages.Here,we aimed to identify and quantify the effect of the most important drivers on the density of the most abundant regenerating tree species(i.e.,Norway spruce and European beech),as well as on species and structural diversity of the tree regeneration.We studied tree regeneration in four former monospecific coniferous stand types(i.e.,Norway spruce,Scots pine,European larch,and Douglas fir)in Southwest Germany that have been under conversion to mixed forests since the 1990s.We sampled tree regeneration in four growth height classes together with a variety of potentially influencing factors on 108 sampling plots and applied multivariate analyses.We identified light availability in the understorey,stand structural attributes,browsing pressure,and diaspore source abundance as the most important factors for the density and diversity of tree regeneration.Particularly,we revealed speciesspecific differences in drivers of regeneration density.While spruce profited from increasing light availability and decreasing stand basal area,beech benefited either from a minor reduction or more strikingly from an increase in overstorey density.Increasing diaspore source abundance positively and a high browsing pressure negatively affected both species equally.Our results suggest that humus and topsoil properties were modified during conversion,probably due to changes in tree species composition and silvicultural activities.The species and structural diversity of the tree regeneration benefitted from increasing light availability,decreasing stand basal area,and a low to moderate browsing pressure.We conclude that forest managers may carefully equilibrate among the regulation of overstorey cover,stand basal area,and browsing pressure to fulfil the objectives of forest conversion,i.e.,establishing and safeguarding a diverse tree regeneration to promote the development of mature mixed forests in the future.
