Due to the lack of a uniform and accurate defi-nition of‘drought’,several indicators have been introduced based on different variables and methods,and the efficiency of each of these is determined according to their...Due to the lack of a uniform and accurate defi-nition of‘drought’,several indicators have been introduced based on different variables and methods,and the efficiency of each of these is determined according to their relationship with drought.The relationship between two drought indices,SPI(standardized precipitation index)and SPEI(standard-ized precipitation-evapotranspiration index)in different sea-sons was investigated using annual rings of 15 tree samples to determine the effect of drought on the growth of oriental beech(Fagus orientalis Lipsky)in the Hyrcanian forests of northern Iran.The different evapotranspiration calcula-tion methods were evaluated on SPEI efficiency based on Hargreaves-Samani,Thornthwaite,and Penman-Monteith methods using the step-by-step M5 decision tree regression method.The results show that SPEI based on the Penman-Monteith in a three-month time scale(spring)had similar temporal changes and a better relationship with annual tree rings(R^(2)=0.81)at a 0.05 significant level.Abrupt change and a decreasing trend in the time series of annual tree rings are similar to the variation in the SPEI based on the Penman-Monteith method.Factors affecting evapotranspiration,temperature,wind speed,and sunshine hours(used in the Penman-Monteith method),increased but precipitation decreased.Using non-linear modeling methods,SPEI based on Penman-Monteith best illustrated climate changes affecting tree growth.展开更多
Oriental Beech is the most important commercial tree species in northern Iran. In recent years wood production companies interested in felling large beech trees for profit have challenged advocates of close-to-nature ...Oriental Beech is the most important commercial tree species in northern Iran. In recent years wood production companies interested in felling large beech trees for profit have challenged advocates of close-to-nature silviculture who favor conservation. Our study objective was to assess the economic value of over-mature beech trees by relating tree diameter （DBH） to amount of decay. Based on the location of onset of decay, we categorized three types of decay as stump, stem, and crown decay. Trees of greater diameter （age） typically showed greater decay in the stem. Percent of decayed volume, diameter of decayed tissue, and length of decay in tree stems varied between 0.5%-64.3%, 15 cm-75 cm, and 2.0-19.5 m, respectively. With increasing trunk diameter, the propor- tion of truck decay increased. Red heart and dark red heart constituted 25% and 14.3% of sampled trees, respectively. However, we found no correlation between intensity of stem decay and morphological charac- teristics of trees. Seedlings were not abundant around the bases of over-mature trees, suggesting that the trees did not contribute to regeneration of the stand. Beech trees of diameter 〉1 m do not provide valu- able round wood for industries and cause to raise wood production costs. We recommend that these trees 〉1 m DBH should be retained in forest stands because of their low commercial value but high ecological and conservational values such as maintaining biodiversity in forest ecosystems.展开更多
The responses of field-grown Fagus engleriana Seem.seedlings to light and soil nutrient availability were investigated.Two-year-old seedlings were grown for two growing seasons under six treatment conditions,including...The responses of field-grown Fagus engleriana Seem.seedlings to light and soil nutrient availability were investigated.Two-year-old seedlings were grown for two growing seasons under six treatment conditions,including three light levels(L1:1%-2%of full sunlight;L2:18%of full sunlight;L3:100%of full sunlight),with and without fertilizer addition(F1 and F0)for each light level.The results showed that light and nutrients had significant effect on seedling growth as measured in terms of shoot height,stem basal diameter and biomass;the mean increments of shoot height over two growing seasons were significantly less in L1 than in L2 and L3(P<0.001),and in L3 than in L2(P<0.01),but the increments during the first growing season were not significantly different among the treatments;the increments of stem basal diameter and biomass components were significantly less in L1 than in L2 and L3(P<0.001);the increments of stem basal diameter and whole plant biomass were not statistically different between L2 and L3;adding fertilizer did not affect the seedling growth under closed forest canopy,but had effect in the environments with more sunlight.The results suggest that(1)two-year-old F.engleriana seedlings couldsurvive the conditions of closed forest canopy,but their growth might be severely inhibited;(2)the seedlings could grow as well as or even better in small forest gaps than in open sites;and(3)fertile soil might enhance seedling growth in forest gaps and open sites,but not under closed forest canopy.展开更多
The distribution, regeneration and succession of Fagus in China were systematically analyzed incomparison with those in Europe and in northern America. The results showed th8t it was very likely that Chinawas the dist...The distribution, regeneration and succession of Fagus in China were systematically analyzed incomparison with those in Europe and in northern America. The results showed th8t it was very likely that Chinawas the distribution center of Fagus, which originated in eastern Asia, migrated into northern America and then intoEurope. Distribution of Fagus in China is relatively independent with seven species. The main reason for wide distribution of Fagus in Europe, but unitary species, is possibly the influence of the climate in Quaternary Period, andalso related with influence of the ocean climate.展开更多
Background:Higher exportation of harvest residues from forests due to increased demand for woody biomass,has reportedly diminished soil mineral resources and may lead to degraded tree nutrition as well as growth.Howev...Background:Higher exportation of harvest residues from forests due to increased demand for woody biomass,has reportedly diminished soil mineral resources and may lead to degraded tree nutrition as well as growth.However,as nutrients become less available in the soil,the remobilization of nutrients in biomass tissues(plant internal cycling)helps sustain tree nutrition.Our study aims to quantify the impact of Removing Harvest Residues and Litter(RHRL)during five years on tree growth,wood density,and stem wood nutrient concentrations in young beech and oak forest stands.Result:Our study found that,RHRL significantly decreased tree growth ring width by 14%,and wood density by 3%,in beech trees,in near bark rings.RHRL also significantly reduced nutrient concentration in near bark and near pith areas of both studied species.Mg,Na and S were found lower by 44%,76%,and 56%,respectively,in near bark area of beech trees.In near bark area of oak trees,K,Ca,Mg,Na,S,and Fe were lower by 20%,25%,41%,48%,41%,and 16%,respectively.K and Mg concentrations decreased more strongly in near pith area compared to near bark area suggesting internal translocation of these two elements.Conclusion:In beech trees,wood density proved to be an important factor while quantifying the effect of removing harvest residuals on tree growth and biomass.Soil nutrient loss intensified the remobilization of nutrients con-tained in older tree rings(close to the pith)towards newly formed rings(close to bark).In our study,in beech trees,K was found to be the most recycled major nutrient.These results demonstrate the potential of such analysis for providing valuable insight into the effect of RHRL in premature stands on the physiological adaptive strategies of trees and an indication of soil fertility status.展开更多
Arthropod assemblages and decomposition rates were compared in the litter of pure and mixed Quercus(Quercus petraea L.)and Fagus(Fagus orientalis L.)stands.Litter was sampled on a monthly basis for 1 year and stored i...Arthropod assemblages and decomposition rates were compared in the litter of pure and mixed Quercus(Quercus petraea L.)and Fagus(Fagus orientalis L.)stands.Litter was sampled on a monthly basis for 1 year and stored in litterbags of different mesh sizes.The experimental objective was to test the effect of mesh size on litter decomposition,decomposition rates of litter,and diversity of the invertebrate fauna between the two types of stands.Decomposition rates were measured by filling three fiber litterbags of different mesh sizes with pure Quercus litter(3 g)left in the pure Quercus stand,and litterbags with Fagus litter(3 g)were left in the pure Fagus stand.Mixed litter samples were prepared by mixing of equal amounts of each litter in the same litterbag and leaving them in the mixed stand.The residual mass of litter from the pure Quercus stand was significantly lower in fine-and coarse-mesh bags than in the medium-mesh bags in pure the Fagus stand.Carbon and nitrogen levels in the pure Quercus litter were significantly different among the mesh sizes at the end of the incubation period.Macroarthropods from 27 taxa were collected from pitfall traps every month.Their relative numbers differed significantly between the pure and mixed-stand litter samples.Litter-dwelling Isotomidae(Collembola)and Mesostigmata(Acarina),and soil-dwelling Mesostigmata were the most numerous in the mixed stand.It is significant that the abundance of macroarthropods contributed to the mass loss of litter in both the medium and coarse mesh sizes in the mixed stand,but did not significantly affect the mass of litter in the pure stands.In the mixed stand,there was a negative correlation between litter mass loss and total number of microarthropods in all mesh sizes.Mixed-stand litter decomposed more slowly than pure-stand litter.展开更多
Species biological history revealed by genetic indicators can provide guidelines for long-term biodiversity conservation in Natura 2000 network. Fagus sylvatica is the keystone species which regulates in the Mediterra...Species biological history revealed by genetic indicators can provide guidelines for long-term biodiversity conservation in Natura 2000 network. Fagus sylvatica is the keystone species which regulates in the Mediterranean Eco-Region ecosystem structure, function and composition. Six hundred fifty nine F. sylvatica individuals have been sampled across 20 sites of European interest in Southern Italy and analyzed at 5 microsatellite loci. For sites marked by both maximum heterozygosity (Ho) and minimum heterozygote deficit (Fis) (IT9210210, ITA070099, IT9210205 and IT9220075) it is suggested to avoid impacts by adopting very conservative measures. Promoting migration processes (pollen flow and seed flow) would be appropriate where it has been monitored low heterozygosity and high genetic disequilibrium. Margin effect due to dryness should be buffered with appropriate belts of thermophilus broad leaved tree species.展开更多
[Objectives]To understand the species composition and diversity of Fagus longipetiolata community.[Methods]The F.longipetiolata community in Guizhou Province was investigated by typical plot method.[Results]There were...[Objectives]To understand the species composition and diversity of Fagus longipetiolata community.[Methods]The F.longipetiolata community in Guizhou Province was investigated by typical plot method.[Results]There were 107 species of vascular plants belonging to 79 genera and 51 families in Leigong Mountain F.longipetiolata community,including 3 species of pteridophytes belonging to 3 genera and 3 families,104 species of spermatophytes belonging to 76 genera and 48 families,including 3 species of gymnosperms belonging to 3 genera and 3 families,and 101 species of angiosperms belonging to 73 genera and 45 families.The types of Leigong Mountain F.longipetiolata community were divided into 7 formations,and the top 10 important species of each formation were Fagaceae,followed by Lauraceae and Ericaceae.The change trend of tree layer richness index was formation I>formation IV>formation VI>formation III>formation VII>formation II>formation V;the dominance index was formation I>formation IV>formation V>formation VI>formation VII>formation III>formation II;H diversity index was formation V>formation II>formation I>formation III>formation VII>formation VI>formation IV;the evenness index is formation II>formation III>formation VI>formation VII>formation IV>formation I>formation V;the total diversity index of the community,formation I(3.67)was the highest,formation V(2.74)was the lowest,manifested as formation I>formation III>formation VI>formation II>formation IV>formation VII>formation V.[Conclusions]The community stability is closely related to its species composition,and the background species is the basis for the survival of the community;the existence of rare species can further enhance the community diversity index and enhance the community stability.展开更多
Taxonomic uncertainties of rare species often hinder effective prioritization for conservation.One such taxonomic uncertainty is the 90-year-old enigma of Fagus chienii.F.chienii was previously only known from the typ...Taxonomic uncertainties of rare species often hinder effective prioritization for conservation.One such taxonomic uncertainty is the 90-year-old enigma of Fagus chienii.F.chienii was previously only known from the type specimens collected in 1935 in Pingwu County of Sichuan Province,China,and has long been thought to be on the verge of extinction.However,morphological similarities to closely related Fagus species have led many to question the taxonomic status of F.chienii.To clarify this taxonomic uncertainty,we used the newly collected samples to reconstruct a molecular phylogeny of Chinese Fagus species against the phylogenetic backbone of the whole genus using seven nuclear genes.In addition,we examined nine morphological characters to determine whether F.chienii is morphologically distinct from its putatively closest relatives(F.hayatae,F.longipetiolata,and F.lucida).Both morphological and phylogenetic analyses indicated that F.chienii is conspecific with F.hayatae.We recommended that F.chienii should not be treated as a separate species in conservation management.However,conservation strategies such as in situ protection and ex situ germplasm preservation should be adopted to prevent the peculiar“F.chienii”population from extinction.展开更多
Foliar resorption is a principal nutrient conservation mechanism in terrestrial vegetation that could be sensitive to ongoing changes in climate and atmospheric nitrogen(N)deposition.We quantified N resorption in nort...Foliar resorption is a principal nutrient conservation mechanism in terrestrial vegetation that could be sensitive to ongoing changes in climate and atmospheric nitrogen(N)deposition.We quantified N resorption in northern hardwood forests along an elevation gradient of decreasing temperature and increasing soil N availability to evaluate how this critical nutrient cycling process can be expected to respond to global and regional environmental changes.Foliar N resorption proficiency(NRP)increased significantly at lower elevations for both sugar maple and American beech,the dominant species in these forests.Foliar N resorption efficiency(NRE)also decreased with increasing elevation,but only in one year.Both species exhibited strong negative relationships between NRP and soil N availability.Thus,we anticipate that with climate warming and decreasing N inputs,northern hardwood forests can be expected to exhibit stronger N conservation via foliar resorption.Both species also exhibited strong correlations between resorption efficiency of N and C,but resorption of both elements was much greater for beech than sugar maple,suggesting contrasting mechanisms of nutrient conservation between these two widespread species.展开更多
The consequences of climate change continue to threaten European forests,particularly for species located at the edges of their latitudinal and altitudinal ranges.While extensively studied in Central Europe,European b...The consequences of climate change continue to threaten European forests,particularly for species located at the edges of their latitudinal and altitudinal ranges.While extensively studied in Central Europe,European beech forests require further investigation to understand how climate change will affect these ecosystems in Mediterranean areas.Proposed silvicultural options increasingly aim at sustainable management to reduce biotic and abiotic stresses and enhance these forest ecosystems'resistance and resilience mechanisms.Process-based models(PBMs)can help us to simulate such phenomena and capture early stress signals while considering the effect of different management approaches.In this study,we focus on estimating sensitivity of two state-of-the-art PBMs forest models by simulating carbon and water fluxes at the stand level to assess productivity changes and feedback resulting from different climatic forcings as well as different management regimes.We applied the 3D-CMCC-FEM and MEDFATE forest models for carbon(C)and water(H_(2)O)fluxes in two sites of the Italian peninsula,Cansiglio in the north and Mongiana in the south,under managed vs.unmanaged scenarios and under current climate and different climatic scenarios(RCP4.5 and RCP8.5).To ensure confidence in the models’results,we preliminary evaluated their performance in simulating C and H_(2)O flux in three additional beech forests of the FLUXNET network along a latitudinal gradient spanning from Denmark to central Italy.The 3D-CMCC-FEM model achieved R^(2)values of 0.83 and 0.86 with RMSEs of 2.53 and 2.05 for C and H_(2)O fluxes,respectively.MEDFATE showed R^(2)values of 0.76 and 0.69 with RMSEs of 2.54 and 3.01.At the Cansiglio site in northern Italy,both models simulated a general increase in C and H_(2)O fluxes under the RCP8.5 climate scenario compared to the current climate.Still,no benefit in managed plots compared to unmanaged ones,as the site does not have water availability limitations,and thus,competition for water is low.At the Mongiana site in southern Italy,both models predict a decrease in C and H_(2)O fluxes and sensitivity to the different climatic forcing compared to the current climate;and an increase in C and H_(2)O fluxes when considering specific management regimes compared to unmanaged scenarios.Conversely,under unmanaged scenarios plots are simulated to experience first signals of mortality prematurely due to water stress(MEDFATE)and carbon starvation(3D-CMCC-FEM)scenarios.In conclusion,while management interventions may be considered a viable solution for the conservation of beech forests under future climate conditions at moister sites like Cansiglio,in drier sites like Mongiana conservation may not lie in management interventions alone.展开更多
Aims Changes in the structure and composition of forests,whether caused by natural or anthropic events,alter the microenviron-ment,sometimes irreversibly.Since the local environment has a direct impact on basic ecolog...Aims Changes in the structure and composition of forests,whether caused by natural or anthropic events,alter the microenviron-ment,sometimes irreversibly.Since the local environment has a direct impact on basic ecological processes,this has become a key component of research.Mexican beech forests(Fagus grandi-folia subsp.mexicana)in the Sierra Madre Oriental are restricted to sites with specific climate,soils and topography,making them an ideal natural system for ecological research.The objectives of this study were to identify the relationship between the microen-vironment and the tree and shrub structure and composition of Mexican beech forests in the state of Hidalgo,and to compare the floristic similarity of these forests on the country scale using data from seven localities.Methods Specimens were collected for a period of one year at all locali-ties in the state of Hidalgo where beech forests are located.At each locality,five 400 m2 plots were established,and structural attributes(basal area,coverage,density and species richness)and six environmental variables were measured in the plots.The relationship between structure and microenvironment was estimated by simple correlation and canonic correspondence analysis(CCA).in addition,floristic similarity between different beech forest localities in the Sierra Madre Oriental was esti-mated by correspondence analysis(CA).Important Findings Twenty tree species and eight shrub species were identified;at all localities studied F.grandifolia subsp.mexicana dominated the can-opy.The multivariate analysis indicated that(i)in the four localities in the state of Hidalgo,all microenvironmental variables except pH are related to the variation observed in species composition and structure;(ii)the El Gosco locality had both tree and shrub species and microenvironmental factors different from those observed in the Fagus forests at the other localities in the study and(iii)the localities studied in order to draw country-scale comparisons could be divided into three groups by floristic similarity.The first group consisted of the Hidalgo localities,the second of the Veracruz localities,and the third,more different from the others,of the Tamaulipas locality.The results of this study provide the first reference for the relationship between the range of microenvironments and species structure in Mexican beech forests.Microenvironmental conditions in the larger beech forests could be used as a model for designing management and con-servation programs for this plant association.Because of its particular ecological and historical characteristics,this association could serve as an example of biodiversity conservation in Mexico.展开更多
Aims There are different components of carbon(C)pools in a natural forest ecosystem:biomass,soil,litter and woody debris.We asked how these pools changed with elevation in one of China’s ecologically important forest...Aims There are different components of carbon(C)pools in a natural forest ecosystem:biomass,soil,litter and woody debris.We asked how these pools changed with elevation in one of China’s ecologically important forest ecosystem,i.e.beech(Fagus L.,Fagaceae)forests,and what were the underlying driving factors of such variation.Methods The four C pools in nine beech forests were investigated along an elevational gradient(1095–1930 m)on Mt.Fanjingshan in Guizhou Province,Southwest China.Variance partitioning was used to explore the relative effects of stand age,climate and other factors on C storage.In addition,we compared the four C pools to other beech forests in Guizhou Province and worldwide.Important Findings The total C pools of beech forest ecosystems ranged from 190.5 to 504.3 Mg C ha^(–1),mainly attributed to biomass C(accounting for 33.7–73.9%)and soil C(accounting for 23.9–65.5%).No more than 4%of ecosystem C pools were stored in woody debris(0.05–3.1%)and litter(0.2–0.7%).Ecosystem C storage increased significantly with elevation,where both the biomass and woody debris C pools increased with elevation,while those of litter and soil exhibited no such trend.For the Guizhou beech forests,climate and stand age were found to be key drivers of the elevational patterns of ecosystem and biomass C storage,while for beech forests globally,stand age was the most important predictor.Compared to beech forests worldwide,beech forests in Guizhou Province displayed a relatively higher biomass C accumulation rate,which may be explained by a much higher precipitation in this area.The present study provides basic data for understanding the C budgets of Chinese beech forests and their possible roles in regional C cycling and emphasizes the general importance of stand age and climate on C accumulation.展开更多
Deadwood plays a key role for biodiversity in forests.A significant number of beetles from this group are currently listed as endangered in the Red List.In addition to other management recommendations,there have been ...Deadwood plays a key role for biodiversity in forests.A significant number of beetles from this group are currently listed as endangered in the Red List.In addition to other management recommendations,there have been recent efforts to enrich stands with dead wood to promote biodiversity.An important parameter for forestry enterprises is the optimization of these interventions.The study investigated the abundance,species richness,gamma diversity,conservation value and biomass of saproxylic beetles in natural forests using window traps.A total of 89traps were used for saproxylic beetle monitoring,of which 29 were placed on lying logs,30 on snags and 30 as controls in forest stand space.A total of 35,011 beetles were recorded in 564 species(61 families).Notably,20,515 of these belong to saproxylic beetles(59%)in 311 species(55%),with 62 classified as Red-List species(20%).In the group of'all saproxylic beetles',the results indicate that a diversity and y diversity(q=0)remain consistent across various deadwood types,whileβdiversity showed significant differences.Significant differences were found in the Red-List species group,where a diversity and y diversity differed,with higher values observed in snags.Rarefaction based total species richness of site was estimated to be 391 species,including 74 Red-Listed species.Comparing the sample coverage of the studied stand categories showed that all saproxylic species exhibit a pronounced preference for inhabiting areas featuring lying logs.Conversely,Red-List species mainly inhabit snags,withβdiversity being more similar to snags and forest stand space.Notably,both the conservation value(weighted average by conservation status)and beetle biomass are significantly highest in snags,whereas stand space shows the lowest values across all measured saproxylic beetle indices.Furthermore,the use of traps set on the poles in forest stand space resulted in an underestimation of the actual stand richness by 20%-25%.Our results support the conclusion that snags are indispensable features in beech forests,playing a key role in promoting high species diversity,especially among Red-List species,and supporting the biomass of saproxylic beetles.Consequently,it becomes crucial to incorporate a higher percentage of standing deadwood in managed forests or actively create equivalent environments by introducing high stumps.展开更多
In this era of biodiversity loss and climate change,quantifying the impacts of natural disturbance on forest communities is imperative to improve biodiversity conservation efforts.Epiphytic and epixylic lichens are ef...In this era of biodiversity loss and climate change,quantifying the impacts of natural disturbance on forest communities is imperative to improve biodiversity conservation efforts.Epiphytic and epixylic lichens are effective forest quality bioindicators,as they are generally long-lived organisms supported by continuity of specific forest structures and their associated microclimatic features.However,how lichen communities respond to the effects of fluctuating historical disturbances remains unclear.Using a dendrochronological approach,this study investigates how natural disturbance dynamics indirectly influence various lichen community metrics in some of Europe's best-preserved primary mixed-beech forests.Mixed modelling revealed that natural historical disturbance processes have decades-long effects on forest structural attributes,which had both congruent and divergent impacts on lichen community richness and composition.Total species richness indirectly benefited from both historical and recent higher-severity disturbances via increased standing dead tree basal area and canopy openness respectively-likely through the presence of both pioneer and late-successional species associated with these conditions.Red-listed species richness showed a dependence on habitat continuity(old trees),and increased with disturbance-related structures(standing dead trees)whilst simultaneously benefiting from periods without severe disturbance events(old trees and reduced deadwood volume).However,if the disturbance occurred over a century in the past,no substantial effect on forest structure was detected.Therefore,while disturbance-mediated forest structures can promote overall richness,threatened species appear vulnerable to more severe disturbance events-a concern,as disturbances are predicted to intensify with climate change.Additionally,the high number of threatened species found reinforce the critical role of primary forest structural attributes for biodiversity maintenance.Hence,we recommend a landscape-scale conservation approach encompassing forest patches in different successional stages to support diverse lichen communities,and the consideration of long-term disturbance dynamics in forest conservation efforts,as they provide critical insights for safeguarding biodiversity in our changing world.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This work was supported by Iran National Science Foundation(INSF)(grant no.96012844).
文摘Due to the lack of a uniform and accurate defi-nition of‘drought’,several indicators have been introduced based on different variables and methods,and the efficiency of each of these is determined according to their relationship with drought.The relationship between two drought indices,SPI(standardized precipitation index)and SPEI(standard-ized precipitation-evapotranspiration index)in different sea-sons was investigated using annual rings of 15 tree samples to determine the effect of drought on the growth of oriental beech(Fagus orientalis Lipsky)in the Hyrcanian forests of northern Iran.The different evapotranspiration calcula-tion methods were evaluated on SPEI efficiency based on Hargreaves-Samani,Thornthwaite,and Penman-Monteith methods using the step-by-step M5 decision tree regression method.The results show that SPEI based on the Penman-Monteith in a three-month time scale(spring)had similar temporal changes and a better relationship with annual tree rings(R^(2)=0.81)at a 0.05 significant level.Abrupt change and a decreasing trend in the time series of annual tree rings are similar to the variation in the SPEI based on the Penman-Monteith method.Factors affecting evapotranspiration,temperature,wind speed,and sunshine hours(used in the Penman-Monteith method),increased but precipitation decreased.Using non-linear modeling methods,SPEI based on Penman-Monteith best illustrated climate changes affecting tree growth.
文摘Oriental Beech is the most important commercial tree species in northern Iran. In recent years wood production companies interested in felling large beech trees for profit have challenged advocates of close-to-nature silviculture who favor conservation. Our study objective was to assess the economic value of over-mature beech trees by relating tree diameter （DBH） to amount of decay. Based on the location of onset of decay, we categorized three types of decay as stump, stem, and crown decay. Trees of greater diameter （age） typically showed greater decay in the stem. Percent of decayed volume, diameter of decayed tissue, and length of decay in tree stems varied between 0.5%-64.3%, 15 cm-75 cm, and 2.0-19.5 m, respectively. With increasing trunk diameter, the propor- tion of truck decay increased. Red heart and dark red heart constituted 25% and 14.3% of sampled trees, respectively. However, we found no correlation between intensity of stem decay and morphological charac- teristics of trees. Seedlings were not abundant around the bases of over-mature trees, suggesting that the trees did not contribute to regeneration of the stand. Beech trees of diameter 〉1 m do not provide valu- able round wood for industries and cause to raise wood production costs. We recommend that these trees 〉1 m DBH should be retained in forest stands because of their low commercial value but high ecological and conservational values such as maintaining biodiversity in forest ecosystems.
文摘The responses of field-grown Fagus engleriana Seem.seedlings to light and soil nutrient availability were investigated.Two-year-old seedlings were grown for two growing seasons under six treatment conditions,including three light levels(L1:1%-2%of full sunlight;L2:18%of full sunlight;L3:100%of full sunlight),with and without fertilizer addition(F1 and F0)for each light level.The results showed that light and nutrients had significant effect on seedling growth as measured in terms of shoot height,stem basal diameter and biomass;the mean increments of shoot height over two growing seasons were significantly less in L1 than in L2 and L3(P<0.001),and in L3 than in L2(P<0.01),but the increments during the first growing season were not significantly different among the treatments;the increments of stem basal diameter and biomass components were significantly less in L1 than in L2 and L3(P<0.001);the increments of stem basal diameter and whole plant biomass were not statistically different between L2 and L3;adding fertilizer did not affect the seedling growth under closed forest canopy,but had effect in the environments with more sunlight.The results suggest that(1)two-year-old F.engleriana seedlings couldsurvive the conditions of closed forest canopy,but their growth might be severely inhibited;(2)the seedlings could grow as well as or even better in small forest gaps than in open sites;and(3)fertile soil might enhance seedling growth in forest gaps and open sites,but not under closed forest canopy.
文摘The distribution, regeneration and succession of Fagus in China were systematically analyzed incomparison with those in Europe and in northern America. The results showed th8t it was very likely that Chinawas the distribution center of Fagus, which originated in eastern Asia, migrated into northern America and then intoEurope. Distribution of Fagus in China is relatively independent with seven species. The main reason for wide distribution of Fagus in Europe, but unitary species, is possibly the influence of the climate in Quaternary Period, andalso related with influence of the ocean climate.
基金This work was supported within the XyloDensMap project,INRAE funded by the French Ministry of Agriculture under the convention n°A6.01/2017.
文摘Background:Higher exportation of harvest residues from forests due to increased demand for woody biomass,has reportedly diminished soil mineral resources and may lead to degraded tree nutrition as well as growth.However,as nutrients become less available in the soil,the remobilization of nutrients in biomass tissues(plant internal cycling)helps sustain tree nutrition.Our study aims to quantify the impact of Removing Harvest Residues and Litter(RHRL)during five years on tree growth,wood density,and stem wood nutrient concentrations in young beech and oak forest stands.Result:Our study found that,RHRL significantly decreased tree growth ring width by 14%,and wood density by 3%,in beech trees,in near bark rings.RHRL also significantly reduced nutrient concentration in near bark and near pith areas of both studied species.Mg,Na and S were found lower by 44%,76%,and 56%,respectively,in near bark area of beech trees.In near bark area of oak trees,K,Ca,Mg,Na,S,and Fe were lower by 20%,25%,41%,48%,41%,and 16%,respectively.K and Mg concentrations decreased more strongly in near pith area compared to near bark area suggesting internal translocation of these two elements.Conclusion:In beech trees,wood density proved to be an important factor while quantifying the effect of removing harvest residuals on tree growth and biomass.Soil nutrient loss intensified the remobilization of nutrients con-tained in older tree rings(close to the pith)towards newly formed rings(close to bark).In our study,in beech trees,K was found to be the most recycled major nutrient.These results demonstrate the potential of such analysis for providing valuable insight into the effect of RHRL in premature stands on the physiological adaptive strategies of trees and an indication of soil fertility status.
基金supported by the Scientific Research Projects Coordination Unit of Istanbul University,Project number3122
文摘Arthropod assemblages and decomposition rates were compared in the litter of pure and mixed Quercus(Quercus petraea L.)and Fagus(Fagus orientalis L.)stands.Litter was sampled on a monthly basis for 1 year and stored in litterbags of different mesh sizes.The experimental objective was to test the effect of mesh size on litter decomposition,decomposition rates of litter,and diversity of the invertebrate fauna between the two types of stands.Decomposition rates were measured by filling three fiber litterbags of different mesh sizes with pure Quercus litter(3 g)left in the pure Quercus stand,and litterbags with Fagus litter(3 g)were left in the pure Fagus stand.Mixed litter samples were prepared by mixing of equal amounts of each litter in the same litterbag and leaving them in the mixed stand.The residual mass of litter from the pure Quercus stand was significantly lower in fine-and coarse-mesh bags than in the medium-mesh bags in pure the Fagus stand.Carbon and nitrogen levels in the pure Quercus litter were significantly different among the mesh sizes at the end of the incubation period.Macroarthropods from 27 taxa were collected from pitfall traps every month.Their relative numbers differed significantly between the pure and mixed-stand litter samples.Litter-dwelling Isotomidae(Collembola)and Mesostigmata(Acarina),and soil-dwelling Mesostigmata were the most numerous in the mixed stand.It is significant that the abundance of macroarthropods contributed to the mass loss of litter in both the medium and coarse mesh sizes in the mixed stand,but did not significantly affect the mass of litter in the pure stands.In the mixed stand,there was a negative correlation between litter mass loss and total number of microarthropods in all mesh sizes.Mixed-stand litter decomposed more slowly than pure-stand litter.
文摘Species biological history revealed by genetic indicators can provide guidelines for long-term biodiversity conservation in Natura 2000 network. Fagus sylvatica is the keystone species which regulates in the Mediterranean Eco-Region ecosystem structure, function and composition. Six hundred fifty nine F. sylvatica individuals have been sampled across 20 sites of European interest in Southern Italy and analyzed at 5 microsatellite loci. For sites marked by both maximum heterozygosity (Ho) and minimum heterozygote deficit (Fis) (IT9210210, ITA070099, IT9210205 and IT9220075) it is suggested to avoid impacts by adopting very conservative measures. Promoting migration processes (pollen flow and seed flow) would be appropriate where it has been monitored low heterozygosity and high genetic disequilibrium. Margin effect due to dryness should be buffered with appropriate belts of thermophilus broad leaved tree species.
基金Supported by Benefit Monitoring of Natural Forest Resources Protection Project in Guizhou Province.
文摘[Objectives]To understand the species composition and diversity of Fagus longipetiolata community.[Methods]The F.longipetiolata community in Guizhou Province was investigated by typical plot method.[Results]There were 107 species of vascular plants belonging to 79 genera and 51 families in Leigong Mountain F.longipetiolata community,including 3 species of pteridophytes belonging to 3 genera and 3 families,104 species of spermatophytes belonging to 76 genera and 48 families,including 3 species of gymnosperms belonging to 3 genera and 3 families,and 101 species of angiosperms belonging to 73 genera and 45 families.The types of Leigong Mountain F.longipetiolata community were divided into 7 formations,and the top 10 important species of each formation were Fagaceae,followed by Lauraceae and Ericaceae.The change trend of tree layer richness index was formation I>formation IV>formation VI>formation III>formation VII>formation II>formation V;the dominance index was formation I>formation IV>formation V>formation VI>formation VII>formation III>formation II;H diversity index was formation V>formation II>formation I>formation III>formation VII>formation VI>formation IV;the evenness index is formation II>formation III>formation VI>formation VII>formation IV>formation I>formation V;the total diversity index of the community,formation I(3.67)was the highest,formation V(2.74)was the lowest,manifested as formation I>formation III>formation VI>formation II>formation IV>formation VII>formation V.[Conclusions]The community stability is closely related to its species composition,and the background species is the basis for the survival of the community;the existence of rare species can further enhance the community diversity index and enhance the community stability.
基金supported by grants from the National Natural Science Foundation of China(No.31770236)the Guangxi Key Research and Development Projects(Guike AB21220057)Training Program for Academic and Technical Leaders(leading talents)in Major Disciplines of Jiangxi Province(grant to Zhiyong Zhang,20213BCJ22006)。
文摘Taxonomic uncertainties of rare species often hinder effective prioritization for conservation.One such taxonomic uncertainty is the 90-year-old enigma of Fagus chienii.F.chienii was previously only known from the type specimens collected in 1935 in Pingwu County of Sichuan Province,China,and has long been thought to be on the verge of extinction.However,morphological similarities to closely related Fagus species have led many to question the taxonomic status of F.chienii.To clarify this taxonomic uncertainty,we used the newly collected samples to reconstruct a molecular phylogeny of Chinese Fagus species against the phylogenetic backbone of the whole genus using seven nuclear genes.In addition,we examined nine morphological characters to determine whether F.chienii is morphologically distinct from its putatively closest relatives(F.hayatae,F.longipetiolata,and F.lucida).Both morphological and phylogenetic analyses indicated that F.chienii is conspecific with F.hayatae.We recommended that F.chienii should not be treated as a separate species in conservation management.However,conservation strategies such as in situ protection and ex situ germplasm preservation should be adopted to prevent the peculiar“F.chienii”population from extinction.
基金National Science Foundation supported this research through the Long Term Ecological Research(LTER)Grant to Hubbard Brook(NSF DEB1114804,1637685,and 2224545)by the project grant(NSF DEB,2020397).
文摘Foliar resorption is a principal nutrient conservation mechanism in terrestrial vegetation that could be sensitive to ongoing changes in climate and atmospheric nitrogen(N)deposition.We quantified N resorption in northern hardwood forests along an elevation gradient of decreasing temperature and increasing soil N availability to evaluate how this critical nutrient cycling process can be expected to respond to global and regional environmental changes.Foliar N resorption proficiency(NRP)increased significantly at lower elevations for both sugar maple and American beech,the dominant species in these forests.Foliar N resorption efficiency(NRE)also decreased with increasing elevation,but only in one year.Both species exhibited strong negative relationships between NRP and soil N availability.Thus,we anticipate that with climate warming and decreasing N inputs,northern hardwood forests can be expected to exhibit stronger N conservation via foliar resorption.Both species also exhibited strong correlations between resorption efficiency of N and C,but resorption of both elements was much greater for beech than sugar maple,suggesting contrasting mechanisms of nutrient conservation between these two widespread species.
基金the Institute Research Centre for Ecological and Forestry Applications (CREAF) of Barcelona that supported the research by the Spanish “Ministerio de Ciencia e Innovacio'n”(MCIN/AEI/ 10.13039/501100011033) (grant agreement No. PID 2021-126679OBI00)partially supported by MIUR Project (PRIN 2020) between WATER and carbon cycles during droug“Unraveling interactionsht and their impact on water resources and forest and grassland ecosySTEMs in the Mediterranean climate (WATERSTEM)”(Project number: 20202WF53Z),“WAFER”at CNR (Consiglio Nazionale delle Ricerche)+3 种基金Priwitzer et al. (2014) (cod. 2020E52THS)-Research Projects of National Relevance funded by the Italian Ministry of University and Research entitled: “Multi-scale observations to predict Forest response to pollution and climate change”(MULTIFOR, project number: 2020E52THS)funding by the project OptForEU Horizon Europe research and innovation programme under grant agreement No. 101060554the project funded under the National Recovery and Resilience Plan (NRRP), Mission 4 Component 2 Investment 1.4-Call for tender No. 3138 of December 16, 2021, rectified by Decree n.3175 of December 18, 2021 of Italian Ministry of UniversityResearch funded by the European UnionationEU under award Number: Project code CN_00000033–Next Gener, Concession Decree No. 1034 of June 17, 2022 adopted by the Italian Ministry of University and Research, CUP B83C22002930006, Project title“National Biodiversity Future Centre-NBFC”
文摘The consequences of climate change continue to threaten European forests,particularly for species located at the edges of their latitudinal and altitudinal ranges.While extensively studied in Central Europe,European beech forests require further investigation to understand how climate change will affect these ecosystems in Mediterranean areas.Proposed silvicultural options increasingly aim at sustainable management to reduce biotic and abiotic stresses and enhance these forest ecosystems'resistance and resilience mechanisms.Process-based models(PBMs)can help us to simulate such phenomena and capture early stress signals while considering the effect of different management approaches.In this study,we focus on estimating sensitivity of two state-of-the-art PBMs forest models by simulating carbon and water fluxes at the stand level to assess productivity changes and feedback resulting from different climatic forcings as well as different management regimes.We applied the 3D-CMCC-FEM and MEDFATE forest models for carbon(C)and water(H_(2)O)fluxes in two sites of the Italian peninsula,Cansiglio in the north and Mongiana in the south,under managed vs.unmanaged scenarios and under current climate and different climatic scenarios(RCP4.5 and RCP8.5).To ensure confidence in the models’results,we preliminary evaluated their performance in simulating C and H_(2)O flux in three additional beech forests of the FLUXNET network along a latitudinal gradient spanning from Denmark to central Italy.The 3D-CMCC-FEM model achieved R^(2)values of 0.83 and 0.86 with RMSEs of 2.53 and 2.05 for C and H_(2)O fluxes,respectively.MEDFATE showed R^(2)values of 0.76 and 0.69 with RMSEs of 2.54 and 3.01.At the Cansiglio site in northern Italy,both models simulated a general increase in C and H_(2)O fluxes under the RCP8.5 climate scenario compared to the current climate.Still,no benefit in managed plots compared to unmanaged ones,as the site does not have water availability limitations,and thus,competition for water is low.At the Mongiana site in southern Italy,both models predict a decrease in C and H_(2)O fluxes and sensitivity to the different climatic forcing compared to the current climate;and an increase in C and H_(2)O fluxes when considering specific management regimes compared to unmanaged scenarios.Conversely,under unmanaged scenarios plots are simulated to experience first signals of mortality prematurely due to water stress(MEDFATE)and carbon starvation(3D-CMCC-FEM)scenarios.In conclusion,while management interventions may be considered a viable solution for the conservation of beech forests under future climate conditions at moister sites like Cansiglio,in drier sites like Mongiana conservation may not lie in management interventions alone.
文摘Aims Changes in the structure and composition of forests,whether caused by natural or anthropic events,alter the microenviron-ment,sometimes irreversibly.Since the local environment has a direct impact on basic ecological processes,this has become a key component of research.Mexican beech forests(Fagus grandi-folia subsp.mexicana)in the Sierra Madre Oriental are restricted to sites with specific climate,soils and topography,making them an ideal natural system for ecological research.The objectives of this study were to identify the relationship between the microen-vironment and the tree and shrub structure and composition of Mexican beech forests in the state of Hidalgo,and to compare the floristic similarity of these forests on the country scale using data from seven localities.Methods Specimens were collected for a period of one year at all locali-ties in the state of Hidalgo where beech forests are located.At each locality,five 400 m2 plots were established,and structural attributes(basal area,coverage,density and species richness)and six environmental variables were measured in the plots.The relationship between structure and microenvironment was estimated by simple correlation and canonic correspondence analysis(CCA).in addition,floristic similarity between different beech forest localities in the Sierra Madre Oriental was esti-mated by correspondence analysis(CA).Important Findings Twenty tree species and eight shrub species were identified;at all localities studied F.grandifolia subsp.mexicana dominated the can-opy.The multivariate analysis indicated that(i)in the four localities in the state of Hidalgo,all microenvironmental variables except pH are related to the variation observed in species composition and structure;(ii)the El Gosco locality had both tree and shrub species and microenvironmental factors different from those observed in the Fagus forests at the other localities in the study and(iii)the localities studied in order to draw country-scale comparisons could be divided into three groups by floristic similarity.The first group consisted of the Hidalgo localities,the second of the Veracruz localities,and the third,more different from the others,of the Tamaulipas locality.The results of this study provide the first reference for the relationship between the range of microenvironments and species structure in Mexican beech forests.Microenvironmental conditions in the larger beech forests could be used as a model for designing management and con-servation programs for this plant association.Because of its particular ecological and historical characteristics,this association could serve as an example of biodiversity conservation in Mexico.
基金supported by the National Key Research and Development Program of China(grant no.2017YFA0605101)Ministry of Science and Technology of China(grant no.2015FY210200)National Natural Science Foundation of China(grant nos.31700374,31621091).
文摘Aims There are different components of carbon(C)pools in a natural forest ecosystem:biomass,soil,litter and woody debris.We asked how these pools changed with elevation in one of China’s ecologically important forest ecosystem,i.e.beech(Fagus L.,Fagaceae)forests,and what were the underlying driving factors of such variation.Methods The four C pools in nine beech forests were investigated along an elevational gradient(1095–1930 m)on Mt.Fanjingshan in Guizhou Province,Southwest China.Variance partitioning was used to explore the relative effects of stand age,climate and other factors on C storage.In addition,we compared the four C pools to other beech forests in Guizhou Province and worldwide.Important Findings The total C pools of beech forest ecosystems ranged from 190.5 to 504.3 Mg C ha^(–1),mainly attributed to biomass C(accounting for 33.7–73.9%)and soil C(accounting for 23.9–65.5%).No more than 4%of ecosystem C pools were stored in woody debris(0.05–3.1%)and litter(0.2–0.7%).Ecosystem C storage increased significantly with elevation,where both the biomass and woody debris C pools increased with elevation,while those of litter and soil exhibited no such trend.For the Guizhou beech forests,climate and stand age were found to be key drivers of the elevational patterns of ecosystem and biomass C storage,while for beech forests globally,stand age was the most important predictor.Compared to beech forests worldwide,beech forests in Guizhou Province displayed a relatively higher biomass C accumulation rate,which may be explained by a much higher precipitation in this area.The present study provides basic data for understanding the C budgets of Chinese beech forests and their possible roles in regional C cycling and emphasizes the general importance of stand age and climate on C accumulation.
基金supported by the Ministry of Agriculture of the Czech Republic(Grant No.QK23020008)。
文摘Deadwood plays a key role for biodiversity in forests.A significant number of beetles from this group are currently listed as endangered in the Red List.In addition to other management recommendations,there have been recent efforts to enrich stands with dead wood to promote biodiversity.An important parameter for forestry enterprises is the optimization of these interventions.The study investigated the abundance,species richness,gamma diversity,conservation value and biomass of saproxylic beetles in natural forests using window traps.A total of 89traps were used for saproxylic beetle monitoring,of which 29 were placed on lying logs,30 on snags and 30 as controls in forest stand space.A total of 35,011 beetles were recorded in 564 species(61 families).Notably,20,515 of these belong to saproxylic beetles(59%)in 311 species(55%),with 62 classified as Red-List species(20%).In the group of'all saproxylic beetles',the results indicate that a diversity and y diversity(q=0)remain consistent across various deadwood types,whileβdiversity showed significant differences.Significant differences were found in the Red-List species group,where a diversity and y diversity differed,with higher values observed in snags.Rarefaction based total species richness of site was estimated to be 391 species,including 74 Red-Listed species.Comparing the sample coverage of the studied stand categories showed that all saproxylic species exhibit a pronounced preference for inhabiting areas featuring lying logs.Conversely,Red-List species mainly inhabit snags,withβdiversity being more similar to snags and forest stand space.Notably,both the conservation value(weighted average by conservation status)and beetle biomass are significantly highest in snags,whereas stand space shows the lowest values across all measured saproxylic beetle indices.Furthermore,the use of traps set on the poles in forest stand space resulted in an underestimation of the actual stand richness by 20%-25%.Our results support the conclusion that snags are indispensable features in beech forests,playing a key role in promoting high species diversity,especially among Red-List species,and supporting the biomass of saproxylic beetles.Consequently,it becomes crucial to incorporate a higher percentage of standing deadwood in managed forests or actively create equivalent environments by introducing high stumps.
基金supported by the Czech Science Foundation(grant no.GACR 22-31322S)the Czech University of Life Sciences Prague(grant no.IGA A_19_22)+3 种基金supported by the Operational Programme Integrated Infrastructure(OPII)funded by the ERDF(ITMS313011T721)Specific research PrF UHK 2114/2022 for the financial supportthe financial support of the Rita-Levi Montalcini(2019)programmefunded by the Italian Ministry of University。
文摘In this era of biodiversity loss and climate change,quantifying the impacts of natural disturbance on forest communities is imperative to improve biodiversity conservation efforts.Epiphytic and epixylic lichens are effective forest quality bioindicators,as they are generally long-lived organisms supported by continuity of specific forest structures and their associated microclimatic features.However,how lichen communities respond to the effects of fluctuating historical disturbances remains unclear.Using a dendrochronological approach,this study investigates how natural disturbance dynamics indirectly influence various lichen community metrics in some of Europe's best-preserved primary mixed-beech forests.Mixed modelling revealed that natural historical disturbance processes have decades-long effects on forest structural attributes,which had both congruent and divergent impacts on lichen community richness and composition.Total species richness indirectly benefited from both historical and recent higher-severity disturbances via increased standing dead tree basal area and canopy openness respectively-likely through the presence of both pioneer and late-successional species associated with these conditions.Red-listed species richness showed a dependence on habitat continuity(old trees),and increased with disturbance-related structures(standing dead trees)whilst simultaneously benefiting from periods without severe disturbance events(old trees and reduced deadwood volume).However,if the disturbance occurred over a century in the past,no substantial effect on forest structure was detected.Therefore,while disturbance-mediated forest structures can promote overall richness,threatened species appear vulnerable to more severe disturbance events-a concern,as disturbances are predicted to intensify with climate change.Additionally,the high number of threatened species found reinforce the critical role of primary forest structural attributes for biodiversity maintenance.Hence,we recommend a landscape-scale conservation approach encompassing forest patches in different successional stages to support diverse lichen communities,and the consideration of long-term disturbance dynamics in forest conservation efforts,as they provide critical insights for safeguarding biodiversity in our changing world.
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.
