Tree-ring chronologies were developed for Sabina saltuaria and Abies faxoniana in mixed forests in the Qionglai Mountains of the eastern Tibetan Plateau.Climate-growth relationship analysis indicated that the two co-e...Tree-ring chronologies were developed for Sabina saltuaria and Abies faxoniana in mixed forests in the Qionglai Mountains of the eastern Tibetan Plateau.Climate-growth relationship analysis indicated that the two co-exist-ing species reponded similarly to climate factors,although S.saltuaria was more sensitive than A.faxoniana.The strong-est correlation was between S.saltuaria chronology and regional mean temperatures from June to November.Based on this relationship,a regional mean temperature from June to November for the period 1605-2016 was constructed.Reconstruction explained 37.3%of the temperature variance during th period 1961-2016.Six major warm periods and five major cold periods were identified.Spectral analysis detected significant interannual and multi-decadal cycles.Reconstruction also revealed the influence of the Atlantic Multi-decadal Oscillation,confirming its importance on climate change on the eastern Tibetan Plateau.展开更多
Crown width(CW)is one of the most important tree metrics,but obtaining CW data is laborious and timeconsuming,particularly in natural forests.The Deep Learning(DL)algorithm has been proposed as an alternative to tradi...Crown width(CW)is one of the most important tree metrics,but obtaining CW data is laborious and timeconsuming,particularly in natural forests.The Deep Learning(DL)algorithm has been proposed as an alternative to traditional regression,but its performance in predicting CW in natural mixed forests is unclear.The aims of this study were to develop DL models for predicting tree CW of natural spruce-fir-broadleaf mixed forests in northeastern China,to analyse the contribution of tree size,tree species,site quality,stand structure,and competition to tree CW prediction,and to compare DL models with nonlinear mixed effects(NLME)models for their reliability.An amount of total 10,086 individual trees in 192 subplots were employed in this study.The results indicated that all deep neural network(DNN)models were free of overfitting and statistically stable within 10-fold cross-validation,and the best DNN model could explain 69%of the CW variation with no significant heteroskedasticity.In addition to diameter at breast height,stand structure,tree species,and competition showed significant effects on CW.The NLME model(R^(2)=0.63)outperformed the DNN model(R^(2)=0.54)in predicting CW when the six input variables were consistent,but the results were the opposite when the DNN model(R^(2)=0.69)included all 22 input variables.These results demonstrated the great potential of DL in tree CW prediction.展开更多
A total of 900 soil samples were collected from five habitats,including primary coniferous broad-leaved mixed forests,secondary coniferous broad-leaved mixed forests,secondary broad-leaved forests,secondary shrub fore...A total of 900 soil samples were collected from five habitats,including primary coniferous broad-leaved mixed forests,secondary coniferous broad-leaved mixed forests,secondary broad-leaved forests,secondary shrub forests,and cutover lands in spring,summer,and autumn to quantify responses of soil Collembolans(springtails)to the restoration of vegetation of temperate coniferous and broad-leaved mixed forests.The results reveal that the taxonomic composition of Collembolans varied in the different stages of vegetation restoration.Seasonal variations were in regard to their abundance and richness.High similarities existed in Collembola communities at different stages of vegetation restoration,and distribution patterns of Collembola taxa displayed an evenness throughout all habitats.Soil Collembolans tended to gather on litter layers and soil surface;the highest abundance was found in the upper 5 cm soil layer during the initial stages of vegetation recovery.Tomocerus,Proisotoma,and Folsomia genera responded positively to the restoration of vegetation.However,responses of Ceratophysella and Parisotoma genera were negative.In addition,the Onychiuridae family did not respond to the vegetation restoration process.It was concluded that restoration of vegetative cover can increase the abundance of soil Collembolans,but different genera respond differently.展开更多
Estimating stand transpiration of natural forests using traditional methods through up-scaling of sap fl ux density from sample trees based on stand sapwood area only is diffi cult because of the complexity of species...Estimating stand transpiration of natural forests using traditional methods through up-scaling of sap fl ux density from sample trees based on stand sapwood area only is diffi cult because of the complexity of species,ages,and hierarchical structure of natural forests.To improve stand transpiration estimation,we developed an up-scaling method by considering the tree dominance eff ect based on the assumption that individual tree transpiration is aff ected by crown dominance and species,in addition to factors previously considered such as meteorological conditions,sapwood area,and soil moisture.In this study,the meteorological factors,soil moisture,and sap fl ux density of 15 sample trees of diff erent species and dominance in a natural evergreen and deciduous broadleaved mixed forest were simultaneously monitored from March 2012 to February 2014 in the Karst mountain region in southwestern China.After establishing a single tree transpiration model which considers the eff ects of dominance and species,an up-scaling method was explored to estimate stand transpiration.The results show that the transpiration intensity increased exponentially with increasing tree dominance.The contribution to annual stand transpiration from a few dominant trees(5.4%of trees, 28.2% of basal area) was up to 65.0%. The correspondingcontribution was 16.2% from sub-dominant trees(7.6% of trees, 16.2% of basal area) and 22.8% from middleandlower-layer trees (87.0% of trees, 55.6% of basal area).The variation of individual tree transpiration was mainly(97.9%) explained by tree dominance, but very weakly bytree species. The estimated annual stand transpiration was300.2 mm when using the newly developed method whichconsiders tree dominance, 52.5 mm (14.9%) lower than theestimation (352.7 mm) of traditional method which considersonly the sapwood area eff ect, and 8.5 mm (2.7%) lowerthan the estimation (308.6 mm) which considers the eff ectsof both species composition and sapwood area. The maintree characteristics aff ecting stand transpiration are tree size(sapwood area) and dominance. Consideration of tree dominancewill signifi cantly improve stand transpiration estimationand provide a more solid basis for guiding integratedforest-water management at stand scale.展开更多
Tree mortality plays a fundamental role in the dynamics of forest ecosystems,yet it is one of the most difficult phenomena to accurately predict.Various modeling strategies have been developed to improve individual tr...Tree mortality plays a fundamental role in the dynamics of forest ecosystems,yet it is one of the most difficult phenomena to accurately predict.Various modeling strategies have been developed to improve individual tree mortality predictions.One less explored strategy is the use of a multistage modeling approach.Potential improvements from this approach have remained largely unknown.In this study,we developed a novel multistage approach and compared its performance in individual tree mortality predictions with a more conventional approach using an identical individual tree mortality model formulation.Extensive permanent plot data(n=9442)covering the Acadian Region of North America and over multiple decades(1965–2014)were used in this study.Our results indicated that the model behavior with the multistage approach better depicted the observed mortality and showed a notable improvement over the conventional approach.The difference between the observed and predicted numbers of dead trees using the multistage approach was much smaller when compared with the conventional approach.In addition,tree survival probabilities predicted by the multistage approach generally were not significantly different from the observations,whereas the conventional approach consistently underestimated mortality across species and overestimated tree survival probabilities over the large range of DBH in the data.The new multistage approach also predictions of zero mortality in individual plots,a result not possible in conventional models.Finally,the new approach was more tolerant of modeling errors because it based estimates on ranked tree mortality rather than error-prone predicted values.Overall,this new multistage approach deserves to be considered and tested in future studies.展开更多
In order to ensure the effective analysis and reconstruction of forests,it is key to ensure the quantitative description of their spatial structure.In this paper,a distance model for the optimal stand spatial structur...In order to ensure the effective analysis and reconstruction of forests,it is key to ensure the quantitative description of their spatial structure.In this paper,a distance model for the optimal stand spatial structure based on weighted Voronoi diagrams is proposed.In particular,we provide a novel methodological model for the comprehensive evaluation of the spatial structure of forest stands in natural mixed conifer-broadleaved forests and the formulation of management decision plans.The applicability of the rank evaluation and the optimal solution distance model are compared and assessed for different standard sample plots of natural mixed conifer-broadleaved forests.The effect of crown width on the spatial structure unit of the trees is observed to be higher than that of the diameter at breast height.Moreover,the influence of crown length is greater than that of tree height.There are nine possible spatial structure units determined by the weighted Voronoi diagram for the number of neighboring trees in the central tree,with an average intersection of neighboring crowns reaching 80%.The rank rating of natural forest sample plots is correlated with the optimal solution distance model,and their results are generally consistent for natural forests.However,the rank rating is not able to provide a quantitative assessment.The optimal solution distance model is observed to be more comprehensive than traditional methods for the evaluation of the spatial structure of forest stands.It can effectively reflect the trends in realistic stand spatial structure factors close to or far from the ideal structure point,and accurately assesses the forest spatial structure.The proposed optimal solution distance model improves the integrated evaluation of the spatial structure of forest stands and provides solid theoretical and technical support for sustainable forest management.展开更多
Background:Herbs are an important part of the forest ecosystem,and their diversity and biomass can reflect the restoration of vegetation after forest thinning disturbances.Based on the near-mature secondary coniferous...Background:Herbs are an important part of the forest ecosystem,and their diversity and biomass can reflect the restoration of vegetation after forest thinning disturbances.Based on the near-mature secondary coniferous and broad-leaved mixed forest in Jilin Province Forestry Experimental Zone,this study analyzed seasonal changes of species diversity and biomass of the understory herb layer after different intensities of thinning.Results:The results showed that although the composition of herbaceous species and the ranking of importance values were affected by thinning intensity,they were mainly determined by seasonal changes.Across the entire growing season,the species with the highest importance values in thinning treatments included Carex pilosa,Aegopodium alpestre,Meehania urticifolia,and Filipendula palmata,which dominated the herb layer of the coniferous and broad-leaved mixed forest.The number of species,Margalef index,Shannon-Wiener index and Simpson index all had their highest values in May,and gradually decreased with months.Pielou index was roughly inverted“N”throughout the growing season.Thinning did not increase the species diversity.Thinning can promote the total biomass,above-and below-ground biomass.The number of plants per unit area and coverage were related to the total biomass,above-and below-ground biomass.The average height had a significantly positive correlation with herb biomass in May but not in July.However,it exerted a significantly negative correlation with herb biomass in September.The biomass in the same month increased with increasing thinning intensity.Total herb biomass,above-and below-ground biomass showed positive correlations with Shannon-Winner index,Simpson index and Pielou evenness index in May.Conclusions:Thinning mainly changed the light environment in the forest,which would improve the plant diversity and biomass of herb layer in a short time.And different thinning intensity had different effects on the diversity of understory herb layer.The findings provide theoretical basis and reference for reasonable thinning and tending in coniferous and broad-leaved mixed forests.展开更多
Patterns of woody regeneration in terms of species composition and diversity were studied in mixed deciduous forest (MDF) and deciduous dipterocarp forest (DDF) in Minbyin reserved forest of Lewe Township. A total of ...Patterns of woody regeneration in terms of species composition and diversity were studied in mixed deciduous forest (MDF) and deciduous dipterocarp forest (DDF) in Minbyin reserved forest of Lewe Township. A total of 57 plant species of MDF belonging to 28 families and 342 individuals and 25 plant species of DDF consist of 15 families and 285 individuals were identified. Plant species diversity was quantitatively higher in the MDF (H' = 3.68) compared to the DDF (H' = 2.39). Tectona grandis showed the highest density (30), dominance (4.40 m<sup>2</sup>) and IVI (27.01) of MDF and Dipterocarpus tuberculatus also composed the highest density (109), dominance (9.02 m<sup>2</sup>) and IVI (81.87) in DDF. The smallest diameter class (10 - 20 cm) comprised with 29 species, 103 individuals in MDF and 18 species, 85 individuals in DDF. The size class distribution displayed a reverse J-shaped pattern. The largest numbers of species were concentrated in the smallest height class in both investigated forests because of height and diameter distribution is closely related. The total densities of seedlings and saplings were 1219 and 531 ha<sup>-1</sup> in MDF and 988 and 444 ha<sup>-1</sup> in DDF respectively. Although soil texture of (40 - 50 cm) and (90 - 100 cm) were sandy clay loam in mixed deciduous forest, the other layers of both investigated forests were sandy loam.展开更多
The mortality of trees across diameter class model is a useful tool for predicting changes in stand structure.Mortality data commonly contain a large fraction of zeros and general discrete models thus show more errors...The mortality of trees across diameter class model is a useful tool for predicting changes in stand structure.Mortality data commonly contain a large fraction of zeros and general discrete models thus show more errors.Based on the traditional Poisson model and the negative binomial model,different forms of zero-inflated and hurdle models were applied to spruce-fir mixed forests data to simulate the number of dead trees.By comparing the residuals and Vuong test statistics,the zero-inflated negative binomial model performed best.A random effect was added to improve the model accuracy;however,the mixed-effects zero-inflated model did not show increased advantages.According to the model principle,the zeroinflated negative binomial model was the most suitable,indicating that the"0"events in this study,mainly from the sample"0",i.e.,the zero mortality data,are largely due to the limitations of the experimental design and sample selection.These results also show that the number of dead trees in the diameter class is positively correlated with the number of trees in that class and the mean stand diameter,and inversely related to class size,and slope and aspect of the site.展开更多
Modelling tree height-diameter relationships in complex tropical rain forest ecosystems remains a challenge because of characteristics of multi-species, multi-layers, and indeterminate age composition. Effective model...Modelling tree height-diameter relationships in complex tropical rain forest ecosystems remains a challenge because of characteristics of multi-species, multi-layers, and indeterminate age composition. Effective modelling of such complex systems required innovative techniques to improve prediction of tree heights for use for aboveground biomass estimations. Therefore, in this study, deep learning algorithm (DLA) models based on artificial intelligence were trained for predicting tree heights in a tropical rain forest of Nigeria. The data consisted of 1736 individual trees representing 116 species, and measured from 52 0.25 ha sample plots. A K-means clustering was used to classify the species into three groups based on height-diameter ratios. The DLA models were trained for each species-group in which diameter at beast height, quadratic mean diameter and number of trees per ha were used as input variables. Predictions by the DLA models were compared with those developed by nonlinear least squares (NLS) and nonlinear mixed-effects (NLME) using different evaluation statistics and equivalence test. In addition, the predicted heights by the models were used to estimate aboveground biomass. The results showed that the DLA models with 100 neurons in 6 hidden layers, 100 neurons in 9 hidden layers and 100 neurons in 7 hidden layers for groups 1, 2, and 3, respectively, outperformed the NLS and NLME models. The root mean square error for the DLA models ranged from 1.939 to 3.887 m. The results also showed that using height predicted by the DLA models for aboveground biomass estimation brought about more than 30% reduction in error relative to NLS and NLME. Consequently, minimal errors were created in aboveground biomass estimation compared to those of the classical methods.展开更多
Height-to-diameter ratios(HD)are an important measure of the stability,density and competition of forest stands.It refl ects the vertical growth of the trees,the vulnerability of the forest canopy structure and infl u...Height-to-diameter ratios(HD)are an important measure of the stability,density and competition of forest stands.It refl ects the vertical growth of the trees,the vulnerability of the forest canopy structure and infl uences volumetric production.HD ratios vary according to tree size,availability of resources for growth,stand density and species composition.Data were taken from 210 trees and a regression technique of generalized linear models for the HD ratio applicable for forest structure conservation was developed.The objective of this study was to model the HD ratios of dominant and co-dominant trees of Araucaria angustifolia according to morphometric,dendrometric,annual diameter increment,stand density,and age variables in three sites in southern Brazil.The results show that the HD ratio decreases with increasing age,crown area and basal area,and increases with stand density and annual diameter increment.Accuracy of the developed equations was demonstrated by the values of deviation,Bayesian and Akaike criteria.The results are of interest to forest managers since they make decisions about silvicultural operations.Growth continuity and forest production indicate that any intervention should be directed at younger trees of smaller sizes,and that one of the main management factors for stand stability and growth is the formation of the stand and its capture of light.展开更多
Background:Seed dispersal by scatter-hoarding animals can affect the developmental dynamics of plant communities.However,how animals might participate in plant inter-community competition has rarely been investigated....Background:Seed dispersal by scatter-hoarding animals can affect the developmental dynamics of plant communities.However,how animals might participate in plant inter-community competition has rarely been investigated.Forest community junction is an area where the competition between plant communities is most prominent and animal activity is more frequent.At present,little is known about how scatter-hoarding animals might assist competitions by adjacent plant communities.Thus,for 3 years(2015–2017),we tracked the fate of 2880 tagged seeds(Quercus aliena var.acuteserrata,Pinus tabuliformis,and P.armandii seed)placed near an edge where the forest composition changes from a pine forest to an oak forest in northwestern China.Results:We found that the seed fates differed when Quercus and Pinus seeds entered adjacent stands.In contrast to Pinus seeds,acorns that entered pine forests were characterized by higher caching rates and longer dispersal distances.Pinus seeds had the highest probability of being predated(85%)by rodents,and eleven Q.aliena var.acuteserrata seedlings were established in pine forests,although none survived in the later stages.In addition,rodents exhibited obvious selectivity in terms of the microhabitats for the seed caching sites.Conclusions:Seed fates differed when Quercus and Pinus seeds entered adjacent stands.The predation pressure by rodents on the seeds of Pinus species limited the germination of seeds and seedling establishment in oak forests.The different seed fates after their bidirectional dispersal could affect the differences in natural regeneration between pine and oak forests,and they might increase the recruitment rates for oak at the edge of an adjacent community.Rodent-mediated seed dispersal could potential unintentionally affect the competition between plant communities.展开更多
Due to the influence of human activities such as cultivation and urban construction,the ecosystem of the Yellow River Basin(YRB)is subjected to increased vulnerability and even potential risk of destruction.Ecological...Due to the influence of human activities such as cultivation and urban construction,the ecosystem of the Yellow River Basin(YRB)is subjected to increased vulnerability and even potential risk of destruction.Ecological restoration has led to an increase in vegetation,but excessive afforestation conversely results in low survival rate of trees,water shortages,and biodiversity loss.It is of great significance for achieving sustainable development of forests to reasonable revegetation in the region.At present,the potential distribution pattern of dominant species and their mixed forms in the basin has not been effectively studied.This study simulated the potential distribution of dominant vegetation in the YRB based on Maximum Entropy(Max Ent)and Genetic Algorithm for Rule-Set Prediction(GARP)and explored the impact of human interference on it by employing land use as the environmental filter to distinguish the regions of human activities.We further predicted the potential distribution of typically mixed forests and discussed their human interference.The main results are as follows:(1)Except for Caragana korshinskii,all models had good above performance(0.7<the mean AUC<1).Except for Caragana korshinskii,the area under the curve(AUC)for 90%of the models indicated that Max Ent performed better than GARP,and Max Ent easily lead to over-fitting while GARP predicted a wider range.(2)Except for Nitraria tangutorum,the dominant types of vegetation such as Pinus tabulaeformis,Platycladus orientalis,and Hippophae rhamnoides mainly distributed in southern Gansu,Shaanxi,and south-central Shanxi.Among them,the largest suitable area of Artemisia gmelinii and Stipa bungeana(High suitable area)were approximately 56.7×104 km2(38.8%)and 54.7×104 km2(28.5%)with the area occupied by large-scale cultivation being 17.5×104 km2(39.4%)and 18.9×104 km2(48%),respectively,which indicated human activities caused great damage to the core growth regions of these vegetation.(3)Mean temperature of coldest quarter or month mainly constrained the growth of most vegetation in the YRB in terms of temperature,while precipitation of wettest/driest month is one of the dominant factors.However,some vegetation responded differently to other meteorological factors due to niche differences.(4)Most of the mixed forests were distributed in southern Gansu,Shaanxi,and Shanxi provinces;its middle and high suitable areas were mainly concentrated in Shaanxi and southern and central Shanxi,where the cultivated land had occupied most of them.Therefore,the results showed that the restoration of herbaceous vegetation such as Artemisia gmelinii and Stipa bungeana has a high potential and it is appropriate that the measures for afforestation should be concentrated in the areas like the lower reaches of the Weihe,Jinghe,and Beiluo rivers and Luliang Mountain,where the cultivated land overlaps with the high suitable areas of the corresponding vegetation and the mixed forests with less water consumption and wide distribution,such as Caragana korshinskii-Hippophae rhamnoides,Pinus tabulaeformis-Quercus liaotungensis,and Ostryopsis davidiana-Stipa bungeana-Hippophae rhamnoides.The results of this study can provide effective guidance for mixed forest plantations and vegetation conservation in the YRB.展开更多
Previous research has shown that competition between plants can have differential effects on leaf stoichiometry and non-structural carbohydrate(NSC)in different environments.However,little attention has been given to ...Previous research has shown that competition between plants can have differential effects on leaf stoichiometry and non-structural carbohydrate(NSC)in different environments.However,little attention has been given to understanding these effects on non-photosynthetic organs,particularly of deciduous tree species.Here we assess the impact of competition on below and aboveground biomass,stoichiometry,nutrient composition and NSC in pure and mixed forests of two Larch species,Larix kaempferi and L.olgensis under nitrogen(N)addition.Nitrogen enrichment did not result in stronger intraspecific competition for both species and L.olgensis benefited from the presence of L.kaempferi under different N levels.Stems kept relatively stable C/N compared to roots and branches in response to competition,while N addition imposed stronger impacts on N/P of different organs rather than competition.In contrast to stable C concentrations,starch and soluble sugar concentrations were more easily impacted by competition and the addition of nitrogen.Competition forced L.kaempferi and L.olgensis to allocate more carbon into storage by increasing their starch concentration and starch/soluble sugar of stems under competition.However,no significant differences in stoichiometry and NSC concentration between intra-and interspecific competition were found.NSC and nutrient pools of L.kaempferi stems,branches and coarse roots consistently declined due to competition regardless of N addition.Coarse and fine roots of L.kaempferi accumulated more N when in competition with L.olgensis than with a conspecific neighbor under N addition.Our results show that NSC was more sensitive to competition relative to stoichiometric traits(N and P)of non-photosynthetic organs.展开更多
Introduction:Variation in reproductive phenology among species is an important mechanism for maintaining species coexistence.In mixed forests,the impact of limiting(biotic and abiotic)factors on tree reproductive succ...Introduction:Variation in reproductive phenology among species is an important mechanism for maintaining species coexistence.In mixed forests,the impact of limiting(biotic and abiotic)factors on tree reproductive success regulates the maintenance of species in balanced proportions or the conversion towards monospecific forests.This study offer a significant first approach to the reproductive phenology of mixed forests,assessing flowering,seeding and loss factors on reproductive success in three forest types(pure deciduous Nothofagus pumilio(Np),evergreen Nothofagus betuloides(Nb)and mixed(M)forests),comparing also between two geographical locations(coast and mountain),during one growing season.Results:Flowering falling started early in Np.Seed fall occurred first and more concentrated in Np,while in Nb,it was progressive during autumn.Phenology in M combined both patterns,but with better reproductive performance of both species.Seed production was greater in Nb(42,900,000 ha^(−1))than in Np(710,000 ha^(−1)),while M presented intermediate values(31,900,000 ha^(−1)).Abortion was greatest in Np(19% of female flowers and 10% of immature fruits),while fruit predation was low(7-9%)in all forest types.Empty seed was the main loss factor,but with low net values for each species in M.Regarding geographical location,sea proximity generated a quick starting of the growing season in coast compared to mountain sites.However,we detected forest types×location interactions in flowering and seeding patterns(e.g.in male flower production and in empty and viable seeds),with differences in species response according to location.Conclusions:Both deciduous and evergreen species have reproductive advantages in mixed compared to pure forests.However,mixed were more similar to pure evergreen forests in their reproductive traits and the incidence of the limiting factors.The study of only one growing season does not allow us to conclude whether mixed forests are stable communities,but we contribute to understand the roles of reproductive phenology in mixed forest dynamics.展开更多
spatial distribution of adult trees in a forest community is determined by patterns of both seed dispersal and seedling recruitment.the objectives of our study were to understand the processes of seed dispersal and se...spatial distribution of adult trees in a forest community is determined by patterns of both seed dispersal and seedling recruitment.the objectives of our study were to understand the processes of seed dispersal and seedling recruitment of dominant tree species in a temperate forest of northeastern China and to identify the factors constraining seed dispersal and seedling establishment at different stages of forest succession.Methods During three summer and autumn sessions between 2006 and 2008,altogether 113080 seeds from 22 different tree species were collected in three large field plots representing different for-est types in the Changbai mountain region of northeastern China.the spatial distribution of seed abundance was analyzed using a syrjala test.regeneration success of nine major tree species was assessed using variables defining‘limitations’in‘seeds’and‘seed-ling establishment’.Important Findings We found that seed production fluctuated between years and varied greatly with forest types.Four tree species,Acer spp.,Fraxinus man-dshurica,Tilia amurensis and Betula spp.,had the greatest seed pro-duction and the widest range of seed dispersal,whereas Quercus mongolica showed the most sustained seed production pattern.the spatial patterns of seed abundance differed significantly among forest types and years.the tree species investigated in this study differed in the degree of seed limitation,as well as in limitation of seedling establishment.there were both negative and positive correlations between seed density and seedling density,depending on site and parental tree density.seeds of 16 tree species were found in the Populus davidiana-Betula platyphylla forest(PbF)plot,11 in the conifer and broad-leaved mixed forest(CbF)plot but only 8 in the broad-leaved-Korean pine mixed forest(bKF)plot.the number of seed-contributing species was not only greater in the secondary forests(CbF and PbF plots)than in the primary forest(bKF plot)but was also more variable during the 3 years of assessment.results from the correlations between seed density and seedling occurrence and that between parental tree density or seed weight and dispersal limitation confirm our intuitive expectations,i.e.heavy seeds had greater dispersal limitation but higher establishment success than light seeds.展开更多
Background: Understanding the role of species identity in interactions among individuals is crucial for assessing the productivity and stability of mixed forests over time. However, there is limited knowledge concerni...Background: Understanding the role of species identity in interactions among individuals is crucial for assessing the productivity and stability of mixed forests over time. However, there is limited knowledge concerning the variation in competitive effect and response of different species along climatic gradients. In this study, we investigated the importance of climate, tree size, and competition on the growth of three tree species: spruce(Picea abies), fir(Abies alba), and beech(Fagus sylvatica), and examined their competitive response and effect along a climatic gradient.Methods: We selected 39 plots distributed across the European mountains with records of the position and growth of 5,759 individuals. For each target species, models relating tree growth to tree size, climate and competition were proposed. Competition was modelled using a neighbourhood competition index that considered the effects of inter-and intraspecific competition on target trees. Competitive responses and effects were related to climate.Likelihood methods and information theory were used to select the best model.Results: Our findings revealed that competition had a greater impact on target species growth than tree size or climate. Climate did influence the competitive effects of neighbouring species, but it did not affect the target species? response to competition. The strength of competitive effects varied along the gradient, contingent on the identity of the interacting species. When the target species exhibited an intermediate competitive effect relative to neighbouring species, both higher inter-than intraspecific competitive effects and competition reduction occurred along the gradient. Notably, species competitive effects were most pronounced when the target species' growth was at its peak and weakest when growing conditions were far from their maximum.Conclusions: Climate modulates the effects of competition from neighbouring trees on the target tree and not the susceptibility of the target tree to competition. The modelling approach should be useful in future research to expand our knowledge of how competition modulates forest communities across environmental gradients.展开更多
Aims Despite the growing interest in the topic of functional ecology,there are still forest regions that have not been examined,as most work has been done in the tropics.unresolved issues include the strength of a gro...Aims Despite the growing interest in the topic of functional ecology,there are still forest regions that have not been examined,as most work has been done in the tropics.unresolved issues include the strength of a growth-mortality trade-off in trees(originally identified for seedlings)and the nature of the association between plant traits and vital rates,if any.our objectives were to examine whether(i)ecological strategies in south american mixed forests are organ-ized along the fast competitor×slow stress-tolerator and height gradients as the main strategy axes depicted in the overall trait and vital rate correlation structure,and(ii)a tentative path model we proposed can explain the patterns of covariation among traits and vital rates.Methods We studied a different habitat(subtropical mixed conifer-hardwood forests)and region(brazilian atlantic Forest)from the majority of related studies in forests,carried out in the Neotropical region.Data on total height,stem slenderness,crown depth,wood density,specific leaf area,leaf and seed length,seed dispersal mode,annual mortality,diameter relative growth rate and relative growth rate under favorable conditions were measured in southern brazil for 66 tree species.Data were subjected to principal components analysis and path analysis.restricted data on saplings and treelets were analyzed through correlation.Important Findingsstudied traits were reduced to four principal components.Principal components analysis produced axes that fit the resource acquisition versus resource-conservation and the height-mortality trade-offs,although the former was split into two distinct axes.seed size and seed dispersal mode appeared independently of these axes.a path model showed that leaf length and specific leaf area caused direct changes in trunk slenderness and,indirectly through growth,affected mortality.Expected trade-offs between growth and survivorship and between wood density and stem slenderness trade-offs were not found.this may result from the lack of extreme pioneers and over-representation of slow-growing hardwood species found in atlantic subtropical forests of south america.this suggests that the fastest growing species in the region do not grow so fast as to compromise wood density and survivorship,but grow fast enough to benefit from increased size.relationships between traits and vital rates seem to be mediated by the assembly process of regional floras,and the relative importance of traits like SLA and wood density may vary between floristic regions.展开更多
Introduction:Following oil sands mining in Alberta,Canada,the main land management goal is to establish a functioning boreal forest ecosystem,including the understory plant community.One of the challenges with restori...Introduction:Following oil sands mining in Alberta,Canada,the main land management goal is to establish a functioning boreal forest ecosystem,including the understory plant community.One of the challenges with restoring the understory is the presence of non-native species that compete with desirable native species for resources.In a greenhouse experiment,we studied the growth of two native understory species(Galium boreale and Vicia americana)and a non-native invasive species(Matricaria perforata)grown with either intra-or interspecific neighbors across three common land reclamation soils and a nitrogen fertilizer treatment.Results:When grown by itself,V.americana aboveground biomass did not differ among soil or fertilizer treatments,likely due to its ability to fix nitrogen.Growth of M.perforata was directly related to soil nitrogen,and it had the greatest increase in biomass with fertilization.Growth and biomass of G.boreale was less than the other species,and it had the highest mortality in the nitrogen-poor soil.When grown together,the proportional biomass of M.perforata and V.americana varied with soil treatment such that M.perforata was dominant in the high-nitrogen forest floormineral mix treatment while V.americana was dominant in the low-nitrogen peat-mineral mix.Conclusions:Operationally,care should be taken when applying fertilizer to reclamation areas,as it may have an unwanted positive effect on growth for undesirable non-native plants at the expense of native species.In terms of seed mixtures,V.americana may be a good option for low inorganic nitrogen resource soils and G.boreale for high nitrogen resource soils.展开更多
基金This study was supported by the National Key Research and Development Program of China(No.2018YFA0605601)Hong Kong Research Grants Council(No.106220169)+1 种基金the National Natural Science Foundation of China(Nos.41671042,42077417,42105155,and 42201083)the National Geographic Society(No.EC-95776R-22).
文摘Tree-ring chronologies were developed for Sabina saltuaria and Abies faxoniana in mixed forests in the Qionglai Mountains of the eastern Tibetan Plateau.Climate-growth relationship analysis indicated that the two co-exist-ing species reponded similarly to climate factors,although S.saltuaria was more sensitive than A.faxoniana.The strong-est correlation was between S.saltuaria chronology and regional mean temperatures from June to November.Based on this relationship,a regional mean temperature from June to November for the period 1605-2016 was constructed.Reconstruction explained 37.3%of the temperature variance during th period 1961-2016.Six major warm periods and five major cold periods were identified.Spectral analysis detected significant interannual and multi-decadal cycles.Reconstruction also revealed the influence of the Atlantic Multi-decadal Oscillation,confirming its importance on climate change on the eastern Tibetan Plateau.
基金funded by National Natural Science Foundation of China(Grant No.31870623)National Key R&D Program of China(Grant No.2022YFD2200501).
文摘Crown width(CW)is one of the most important tree metrics,but obtaining CW data is laborious and timeconsuming,particularly in natural forests.The Deep Learning(DL)algorithm has been proposed as an alternative to traditional regression,but its performance in predicting CW in natural mixed forests is unclear.The aims of this study were to develop DL models for predicting tree CW of natural spruce-fir-broadleaf mixed forests in northeastern China,to analyse the contribution of tree size,tree species,site quality,stand structure,and competition to tree CW prediction,and to compare DL models with nonlinear mixed effects(NLME)models for their reliability.An amount of total 10,086 individual trees in 192 subplots were employed in this study.The results indicated that all deep neural network(DNN)models were free of overfitting and statistically stable within 10-fold cross-validation,and the best DNN model could explain 69%of the CW variation with no significant heteroskedasticity.In addition to diameter at breast height,stand structure,tree species,and competition showed significant effects on CW.The NLME model(R^(2)=0.63)outperformed the DNN model(R^(2)=0.54)in predicting CW when the six input variables were consistent,but the results were the opposite when the DNN model(R^(2)=0.69)included all 22 input variables.These results demonstrated the great potential of DL in tree CW prediction.
基金We express our sincere thanks to Dr.Ernest Bernard(University of Tennessee,Knoxville,USA)for his kind help.At the same time,we would like to thank Dr.Xiaoqiang Li,Dr.Zhenghai Wang,Huiying Han,Hongyue Li,Wenli Xue,Yumei Guo,and Xinchang Kou for their help with field work and laboratory analyses。
文摘A total of 900 soil samples were collected from five habitats,including primary coniferous broad-leaved mixed forests,secondary coniferous broad-leaved mixed forests,secondary broad-leaved forests,secondary shrub forests,and cutover lands in spring,summer,and autumn to quantify responses of soil Collembolans(springtails)to the restoration of vegetation of temperate coniferous and broad-leaved mixed forests.The results reveal that the taxonomic composition of Collembolans varied in the different stages of vegetation restoration.Seasonal variations were in regard to their abundance and richness.High similarities existed in Collembola communities at different stages of vegetation restoration,and distribution patterns of Collembola taxa displayed an evenness throughout all habitats.Soil Collembolans tended to gather on litter layers and soil surface;the highest abundance was found in the upper 5 cm soil layer during the initial stages of vegetation recovery.Tomocerus,Proisotoma,and Folsomia genera responded positively to the restoration of vegetation.However,responses of Ceratophysella and Parisotoma genera were negative.In addition,the Onychiuridae family did not respond to the vegetation restoration process.It was concluded that restoration of vegetative cover can increase the abundance of soil Collembolans,but different genera respond differently.
文摘Estimating stand transpiration of natural forests using traditional methods through up-scaling of sap fl ux density from sample trees based on stand sapwood area only is diffi cult because of the complexity of species,ages,and hierarchical structure of natural forests.To improve stand transpiration estimation,we developed an up-scaling method by considering the tree dominance eff ect based on the assumption that individual tree transpiration is aff ected by crown dominance and species,in addition to factors previously considered such as meteorological conditions,sapwood area,and soil moisture.In this study,the meteorological factors,soil moisture,and sap fl ux density of 15 sample trees of diff erent species and dominance in a natural evergreen and deciduous broadleaved mixed forest were simultaneously monitored from March 2012 to February 2014 in the Karst mountain region in southwestern China.After establishing a single tree transpiration model which considers the eff ects of dominance and species,an up-scaling method was explored to estimate stand transpiration.The results show that the transpiration intensity increased exponentially with increasing tree dominance.The contribution to annual stand transpiration from a few dominant trees(5.4%of trees, 28.2% of basal area) was up to 65.0%. The correspondingcontribution was 16.2% from sub-dominant trees(7.6% of trees, 16.2% of basal area) and 22.8% from middleandlower-layer trees (87.0% of trees, 55.6% of basal area).The variation of individual tree transpiration was mainly(97.9%) explained by tree dominance, but very weakly bytree species. The estimated annual stand transpiration was300.2 mm when using the newly developed method whichconsiders tree dominance, 52.5 mm (14.9%) lower than theestimation (352.7 mm) of traditional method which considersonly the sapwood area eff ect, and 8.5 mm (2.7%) lowerthan the estimation (308.6 mm) which considers the eff ectsof both species composition and sapwood area. The maintree characteristics aff ecting stand transpiration are tree size(sapwood area) and dominance. Consideration of tree dominancewill signifi cantly improve stand transpiration estimationand provide a more solid basis for guiding integratedforest-water management at stand scale.
基金provided by National Science Foundation Center for Advanced Forestry Systems(CAFSAward#1915078)RII Track-2FEC(Award#1920908)。
文摘Tree mortality plays a fundamental role in the dynamics of forest ecosystems,yet it is one of the most difficult phenomena to accurately predict.Various modeling strategies have been developed to improve individual tree mortality predictions.One less explored strategy is the use of a multistage modeling approach.Potential improvements from this approach have remained largely unknown.In this study,we developed a novel multistage approach and compared its performance in individual tree mortality predictions with a more conventional approach using an identical individual tree mortality model formulation.Extensive permanent plot data(n=9442)covering the Acadian Region of North America and over multiple decades(1965–2014)were used in this study.Our results indicated that the model behavior with the multistage approach better depicted the observed mortality and showed a notable improvement over the conventional approach.The difference between the observed and predicted numbers of dead trees using the multistage approach was much smaller when compared with the conventional approach.In addition,tree survival probabilities predicted by the multistage approach generally were not significantly different from the observations,whereas the conventional approach consistently underestimated mortality across species and overestimated tree survival probabilities over the large range of DBH in the data.The new multistage approach also predictions of zero mortality in individual plots,a result not possible in conventional models.Finally,the new approach was more tolerant of modeling errors because it based estimates on ranked tree mortality rather than error-prone predicted values.Overall,this new multistage approach deserves to be considered and tested in future studies.
基金funded by National Key Research and development project(2022YFD2201001)。
文摘In order to ensure the effective analysis and reconstruction of forests,it is key to ensure the quantitative description of their spatial structure.In this paper,a distance model for the optimal stand spatial structure based on weighted Voronoi diagrams is proposed.In particular,we provide a novel methodological model for the comprehensive evaluation of the spatial structure of forest stands in natural mixed conifer-broadleaved forests and the formulation of management decision plans.The applicability of the rank evaluation and the optimal solution distance model are compared and assessed for different standard sample plots of natural mixed conifer-broadleaved forests.The effect of crown width on the spatial structure unit of the trees is observed to be higher than that of the diameter at breast height.Moreover,the influence of crown length is greater than that of tree height.There are nine possible spatial structure units determined by the weighted Voronoi diagram for the number of neighboring trees in the central tree,with an average intersection of neighboring crowns reaching 80%.The rank rating of natural forest sample plots is correlated with the optimal solution distance model,and their results are generally consistent for natural forests.However,the rank rating is not able to provide a quantitative assessment.The optimal solution distance model is observed to be more comprehensive than traditional methods for the evaluation of the spatial structure of forest stands.It can effectively reflect the trends in realistic stand spatial structure factors close to or far from the ideal structure point,and accurately assesses the forest spatial structure.The proposed optimal solution distance model improves the integrated evaluation of the spatial structure of forest stands and provides solid theoretical and technical support for sustainable forest management.
基金financially supported by a grant from the National Key Research and Development Program of China(2017YFC0504102)the Science and Technology Program of Jilin Provincial Education Department(JJKH20180349KJ).
文摘Background:Herbs are an important part of the forest ecosystem,and their diversity and biomass can reflect the restoration of vegetation after forest thinning disturbances.Based on the near-mature secondary coniferous and broad-leaved mixed forest in Jilin Province Forestry Experimental Zone,this study analyzed seasonal changes of species diversity and biomass of the understory herb layer after different intensities of thinning.Results:The results showed that although the composition of herbaceous species and the ranking of importance values were affected by thinning intensity,they were mainly determined by seasonal changes.Across the entire growing season,the species with the highest importance values in thinning treatments included Carex pilosa,Aegopodium alpestre,Meehania urticifolia,and Filipendula palmata,which dominated the herb layer of the coniferous and broad-leaved mixed forest.The number of species,Margalef index,Shannon-Wiener index and Simpson index all had their highest values in May,and gradually decreased with months.Pielou index was roughly inverted“N”throughout the growing season.Thinning did not increase the species diversity.Thinning can promote the total biomass,above-and below-ground biomass.The number of plants per unit area and coverage were related to the total biomass,above-and below-ground biomass.The average height had a significantly positive correlation with herb biomass in May but not in July.However,it exerted a significantly negative correlation with herb biomass in September.The biomass in the same month increased with increasing thinning intensity.Total herb biomass,above-and below-ground biomass showed positive correlations with Shannon-Winner index,Simpson index and Pielou evenness index in May.Conclusions:Thinning mainly changed the light environment in the forest,which would improve the plant diversity and biomass of herb layer in a short time.And different thinning intensity had different effects on the diversity of understory herb layer.The findings provide theoretical basis and reference for reasonable thinning and tending in coniferous and broad-leaved mixed forests.
文摘Patterns of woody regeneration in terms of species composition and diversity were studied in mixed deciduous forest (MDF) and deciduous dipterocarp forest (DDF) in Minbyin reserved forest of Lewe Township. A total of 57 plant species of MDF belonging to 28 families and 342 individuals and 25 plant species of DDF consist of 15 families and 285 individuals were identified. Plant species diversity was quantitatively higher in the MDF (H' = 3.68) compared to the DDF (H' = 2.39). Tectona grandis showed the highest density (30), dominance (4.40 m<sup>2</sup>) and IVI (27.01) of MDF and Dipterocarpus tuberculatus also composed the highest density (109), dominance (9.02 m<sup>2</sup>) and IVI (81.87) in DDF. The smallest diameter class (10 - 20 cm) comprised with 29 species, 103 individuals in MDF and 18 species, 85 individuals in DDF. The size class distribution displayed a reverse J-shaped pattern. The largest numbers of species were concentrated in the smallest height class in both investigated forests because of height and diameter distribution is closely related. The total densities of seedlings and saplings were 1219 and 531 ha<sup>-1</sup> in MDF and 988 and 444 ha<sup>-1</sup> in DDF respectively. Although soil texture of (40 - 50 cm) and (90 - 100 cm) were sandy clay loam in mixed deciduous forest, the other layers of both investigated forests were sandy loam.
基金supported by the "948" Project of the State Forestry Administration of China(No.2013-4-66)
文摘The mortality of trees across diameter class model is a useful tool for predicting changes in stand structure.Mortality data commonly contain a large fraction of zeros and general discrete models thus show more errors.Based on the traditional Poisson model and the negative binomial model,different forms of zero-inflated and hurdle models were applied to spruce-fir mixed forests data to simulate the number of dead trees.By comparing the residuals and Vuong test statistics,the zero-inflated negative binomial model performed best.A random effect was added to improve the model accuracy;however,the mixed-effects zero-inflated model did not show increased advantages.According to the model principle,the zeroinflated negative binomial model was the most suitable,indicating that the"0"events in this study,mainly from the sample"0",i.e.,the zero mortality data,are largely due to the limitations of the experimental design and sample selection.These results also show that the number of dead trees in the diameter class is positively correlated with the number of trees in that class and the mean stand diameter,and inversely related to class size,and slope and aspect of the site.
文摘Modelling tree height-diameter relationships in complex tropical rain forest ecosystems remains a challenge because of characteristics of multi-species, multi-layers, and indeterminate age composition. Effective modelling of such complex systems required innovative techniques to improve prediction of tree heights for use for aboveground biomass estimations. Therefore, in this study, deep learning algorithm (DLA) models based on artificial intelligence were trained for predicting tree heights in a tropical rain forest of Nigeria. The data consisted of 1736 individual trees representing 116 species, and measured from 52 0.25 ha sample plots. A K-means clustering was used to classify the species into three groups based on height-diameter ratios. The DLA models were trained for each species-group in which diameter at beast height, quadratic mean diameter and number of trees per ha were used as input variables. Predictions by the DLA models were compared with those developed by nonlinear least squares (NLS) and nonlinear mixed-effects (NLME) using different evaluation statistics and equivalence test. In addition, the predicted heights by the models were used to estimate aboveground biomass. The results showed that the DLA models with 100 neurons in 6 hidden layers, 100 neurons in 9 hidden layers and 100 neurons in 7 hidden layers for groups 1, 2, and 3, respectively, outperformed the NLS and NLME models. The root mean square error for the DLA models ranged from 1.939 to 3.887 m. The results also showed that using height predicted by the DLA models for aboveground biomass estimation brought about more than 30% reduction in error relative to NLS and NLME. Consequently, minimal errors were created in aboveground biomass estimation compared to those of the classical methods.
基金The FAPESC(Foundation for Research Support of the Santa Catarina State),Case Number 2017TR639.
文摘Height-to-diameter ratios(HD)are an important measure of the stability,density and competition of forest stands.It refl ects the vertical growth of the trees,the vulnerability of the forest canopy structure and infl uences volumetric production.HD ratios vary according to tree size,availability of resources for growth,stand density and species composition.Data were taken from 210 trees and a regression technique of generalized linear models for the HD ratio applicable for forest structure conservation was developed.The objective of this study was to model the HD ratios of dominant and co-dominant trees of Araucaria angustifolia according to morphometric,dendrometric,annual diameter increment,stand density,and age variables in three sites in southern Brazil.The results show that the HD ratio decreases with increasing age,crown area and basal area,and increases with stand density and annual diameter increment.Accuracy of the developed equations was demonstrated by the values of deviation,Bayesian and Akaike criteria.The results are of interest to forest managers since they make decisions about silvicultural operations.Growth continuity and forest production indicate that any intervention should be directed at younger trees of smaller sizes,and that one of the main management factors for stand stability and growth is the formation of the stand and its capture of light.
基金the National Natural Science Foundation of China(No.31470644).
文摘Background:Seed dispersal by scatter-hoarding animals can affect the developmental dynamics of plant communities.However,how animals might participate in plant inter-community competition has rarely been investigated.Forest community junction is an area where the competition between plant communities is most prominent and animal activity is more frequent.At present,little is known about how scatter-hoarding animals might assist competitions by adjacent plant communities.Thus,for 3 years(2015–2017),we tracked the fate of 2880 tagged seeds(Quercus aliena var.acuteserrata,Pinus tabuliformis,and P.armandii seed)placed near an edge where the forest composition changes from a pine forest to an oak forest in northwestern China.Results:We found that the seed fates differed when Quercus and Pinus seeds entered adjacent stands.In contrast to Pinus seeds,acorns that entered pine forests were characterized by higher caching rates and longer dispersal distances.Pinus seeds had the highest probability of being predated(85%)by rodents,and eleven Q.aliena var.acuteserrata seedlings were established in pine forests,although none survived in the later stages.In addition,rodents exhibited obvious selectivity in terms of the microhabitats for the seed caching sites.Conclusions:Seed fates differed when Quercus and Pinus seeds entered adjacent stands.The predation pressure by rodents on the seeds of Pinus species limited the germination of seeds and seedling establishment in oak forests.The different seed fates after their bidirectional dispersal could affect the differences in natural regeneration between pine and oak forests,and they might increase the recruitment rates for oak at the edge of an adjacent community.Rodent-mediated seed dispersal could potential unintentionally affect the competition between plant communities.
基金performed in the framework of the National Science Fund for Distinguished Young Scholars(31700370)。
文摘Due to the influence of human activities such as cultivation and urban construction,the ecosystem of the Yellow River Basin(YRB)is subjected to increased vulnerability and even potential risk of destruction.Ecological restoration has led to an increase in vegetation,but excessive afforestation conversely results in low survival rate of trees,water shortages,and biodiversity loss.It is of great significance for achieving sustainable development of forests to reasonable revegetation in the region.At present,the potential distribution pattern of dominant species and their mixed forms in the basin has not been effectively studied.This study simulated the potential distribution of dominant vegetation in the YRB based on Maximum Entropy(Max Ent)and Genetic Algorithm for Rule-Set Prediction(GARP)and explored the impact of human interference on it by employing land use as the environmental filter to distinguish the regions of human activities.We further predicted the potential distribution of typically mixed forests and discussed their human interference.The main results are as follows:(1)Except for Caragana korshinskii,all models had good above performance(0.7<the mean AUC<1).Except for Caragana korshinskii,the area under the curve(AUC)for 90%of the models indicated that Max Ent performed better than GARP,and Max Ent easily lead to over-fitting while GARP predicted a wider range.(2)Except for Nitraria tangutorum,the dominant types of vegetation such as Pinus tabulaeformis,Platycladus orientalis,and Hippophae rhamnoides mainly distributed in southern Gansu,Shaanxi,and south-central Shanxi.Among them,the largest suitable area of Artemisia gmelinii and Stipa bungeana(High suitable area)were approximately 56.7×104 km2(38.8%)and 54.7×104 km2(28.5%)with the area occupied by large-scale cultivation being 17.5×104 km2(39.4%)and 18.9×104 km2(48%),respectively,which indicated human activities caused great damage to the core growth regions of these vegetation.(3)Mean temperature of coldest quarter or month mainly constrained the growth of most vegetation in the YRB in terms of temperature,while precipitation of wettest/driest month is one of the dominant factors.However,some vegetation responded differently to other meteorological factors due to niche differences.(4)Most of the mixed forests were distributed in southern Gansu,Shaanxi,and Shanxi provinces;its middle and high suitable areas were mainly concentrated in Shaanxi and southern and central Shanxi,where the cultivated land had occupied most of them.Therefore,the results showed that the restoration of herbaceous vegetation such as Artemisia gmelinii and Stipa bungeana has a high potential and it is appropriate that the measures for afforestation should be concentrated in the areas like the lower reaches of the Weihe,Jinghe,and Beiluo rivers and Luliang Mountain,where the cultivated land overlaps with the high suitable areas of the corresponding vegetation and the mixed forests with less water consumption and wide distribution,such as Caragana korshinskii-Hippophae rhamnoides,Pinus tabulaeformis-Quercus liaotungensis,and Ostryopsis davidiana-Stipa bungeana-Hippophae rhamnoides.The results of this study can provide effective guidance for mixed forest plantations and vegetation conservation in the YRB.
基金supported by Zhejiang Provincial Natural Science Foundation of China(LQ18C030003,LQ18C160004)Starting Research Fund from Hangzhou Normal University(2018QDL006)。
文摘Previous research has shown that competition between plants can have differential effects on leaf stoichiometry and non-structural carbohydrate(NSC)in different environments.However,little attention has been given to understanding these effects on non-photosynthetic organs,particularly of deciduous tree species.Here we assess the impact of competition on below and aboveground biomass,stoichiometry,nutrient composition and NSC in pure and mixed forests of two Larch species,Larix kaempferi and L.olgensis under nitrogen(N)addition.Nitrogen enrichment did not result in stronger intraspecific competition for both species and L.olgensis benefited from the presence of L.kaempferi under different N levels.Stems kept relatively stable C/N compared to roots and branches in response to competition,while N addition imposed stronger impacts on N/P of different organs rather than competition.In contrast to stable C concentrations,starch and soluble sugar concentrations were more easily impacted by competition and the addition of nitrogen.Competition forced L.kaempferi and L.olgensis to allocate more carbon into storage by increasing their starch concentration and starch/soluble sugar of stems under competition.However,no significant differences in stoichiometry and NSC concentration between intra-and interspecific competition were found.NSC and nutrient pools of L.kaempferi stems,branches and coarse roots consistently declined due to competition regardless of N addition.Coarse and fine roots of L.kaempferi accumulated more N when in competition with L.olgensis than with a conspecific neighbor under N addition.Our results show that NSC was more sensitive to competition relative to stoichiometric traits(N and P)of non-photosynthetic organs.
文摘Introduction:Variation in reproductive phenology among species is an important mechanism for maintaining species coexistence.In mixed forests,the impact of limiting(biotic and abiotic)factors on tree reproductive success regulates the maintenance of species in balanced proportions or the conversion towards monospecific forests.This study offer a significant first approach to the reproductive phenology of mixed forests,assessing flowering,seeding and loss factors on reproductive success in three forest types(pure deciduous Nothofagus pumilio(Np),evergreen Nothofagus betuloides(Nb)and mixed(M)forests),comparing also between two geographical locations(coast and mountain),during one growing season.Results:Flowering falling started early in Np.Seed fall occurred first and more concentrated in Np,while in Nb,it was progressive during autumn.Phenology in M combined both patterns,but with better reproductive performance of both species.Seed production was greater in Nb(42,900,000 ha^(−1))than in Np(710,000 ha^(−1)),while M presented intermediate values(31,900,000 ha^(−1)).Abortion was greatest in Np(19% of female flowers and 10% of immature fruits),while fruit predation was low(7-9%)in all forest types.Empty seed was the main loss factor,but with low net values for each species in M.Regarding geographical location,sea proximity generated a quick starting of the growing season in coast compared to mountain sites.However,we detected forest types×location interactions in flowering and seeding patterns(e.g.in male flower production and in empty and viable seeds),with differences in species response according to location.Conclusions:Both deciduous and evergreen species have reproductive advantages in mixed compared to pure forests.However,mixed were more similar to pure evergreen forests in their reproductive traits and the incidence of the limiting factors.The study of only one growing season does not allow us to conclude whether mixed forests are stable communities,but we contribute to understand the roles of reproductive phenology in mixed forest dynamics.
基金National Special Research Program for Forestry Welfare of China(201004002)the 12th five-year National Science and Technology plan of China(2012BAC01B03)+1 种基金the Program for New Century Excellent Talents in University of the Ministry of Education of China(NCET-12-0781)the Program of the Co-Construction with Beijing Municipal Government of China(2012).
文摘spatial distribution of adult trees in a forest community is determined by patterns of both seed dispersal and seedling recruitment.the objectives of our study were to understand the processes of seed dispersal and seedling recruitment of dominant tree species in a temperate forest of northeastern China and to identify the factors constraining seed dispersal and seedling establishment at different stages of forest succession.Methods During three summer and autumn sessions between 2006 and 2008,altogether 113080 seeds from 22 different tree species were collected in three large field plots representing different for-est types in the Changbai mountain region of northeastern China.the spatial distribution of seed abundance was analyzed using a syrjala test.regeneration success of nine major tree species was assessed using variables defining‘limitations’in‘seeds’and‘seed-ling establishment’.Important Findings We found that seed production fluctuated between years and varied greatly with forest types.Four tree species,Acer spp.,Fraxinus man-dshurica,Tilia amurensis and Betula spp.,had the greatest seed pro-duction and the widest range of seed dispersal,whereas Quercus mongolica showed the most sustained seed production pattern.the spatial patterns of seed abundance differed significantly among forest types and years.the tree species investigated in this study differed in the degree of seed limitation,as well as in limitation of seedling establishment.there were both negative and positive correlations between seed density and seedling density,depending on site and parental tree density.seeds of 16 tree species were found in the Populus davidiana-Betula platyphylla forest(PbF)plot,11 in the conifer and broad-leaved mixed forest(CbF)plot but only 8 in the broad-leaved-Korean pine mixed forest(bKF)plot.the number of seed-contributing species was not only greater in the secondary forests(CbF and PbF plots)than in the primary forest(bKF plot)but was also more variable during the 3 years of assessment.results from the correlations between seed density and seedling occurrence and that between parental tree density or seed weight and dispersal limitation confirm our intuitive expectations,i.e.heavy seeds had greater dispersal limitation but higher establishment success than light seeds.
基金This publication is based upon work from COST Action CLIMO(CA15226) supported by COST (European Cooperation in Science and Technology)the UMBRACLIM project (PID2019-111781RB-I00)funded by the Spanish Ministry for Science and Innovation. Teresa Valor was contracted with a grant“Juan de la Cierva-Formaci on”(FJC2018-036673-I). Z.S. received funds from the grant no. APVV-20-0365 and from project TreeAdapt supported by the MPRV SR. Aitor Ameztegui is supported by a Serra-Húnter fellowship by the Generalitat de Catalunya。
文摘Background: Understanding the role of species identity in interactions among individuals is crucial for assessing the productivity and stability of mixed forests over time. However, there is limited knowledge concerning the variation in competitive effect and response of different species along climatic gradients. In this study, we investigated the importance of climate, tree size, and competition on the growth of three tree species: spruce(Picea abies), fir(Abies alba), and beech(Fagus sylvatica), and examined their competitive response and effect along a climatic gradient.Methods: We selected 39 plots distributed across the European mountains with records of the position and growth of 5,759 individuals. For each target species, models relating tree growth to tree size, climate and competition were proposed. Competition was modelled using a neighbourhood competition index that considered the effects of inter-and intraspecific competition on target trees. Competitive responses and effects were related to climate.Likelihood methods and information theory were used to select the best model.Results: Our findings revealed that competition had a greater impact on target species growth than tree size or climate. Climate did influence the competitive effects of neighbouring species, but it did not affect the target species? response to competition. The strength of competitive effects varied along the gradient, contingent on the identity of the interacting species. When the target species exhibited an intermediate competitive effect relative to neighbouring species, both higher inter-than intraspecific competitive effects and competition reduction occurred along the gradient. Notably, species competitive effects were most pronounced when the target species' growth was at its peak and weakest when growing conditions were far from their maximum.Conclusions: Climate modulates the effects of competition from neighbouring trees on the target tree and not the susceptibility of the target tree to competition. The modelling approach should be useful in future research to expand our knowledge of how competition modulates forest communities across environmental gradients.
基金Funding was provided by the Conselho Nacional de Desenvolvimento Científico e Tecnológico(CNPq)through the grant‘PELD-Bioma Araucária e suas Transições’and by Energética Barra Grande(BAESA).
文摘Aims Despite the growing interest in the topic of functional ecology,there are still forest regions that have not been examined,as most work has been done in the tropics.unresolved issues include the strength of a growth-mortality trade-off in trees(originally identified for seedlings)and the nature of the association between plant traits and vital rates,if any.our objectives were to examine whether(i)ecological strategies in south american mixed forests are organ-ized along the fast competitor×slow stress-tolerator and height gradients as the main strategy axes depicted in the overall trait and vital rate correlation structure,and(ii)a tentative path model we proposed can explain the patterns of covariation among traits and vital rates.Methods We studied a different habitat(subtropical mixed conifer-hardwood forests)and region(brazilian atlantic Forest)from the majority of related studies in forests,carried out in the Neotropical region.Data on total height,stem slenderness,crown depth,wood density,specific leaf area,leaf and seed length,seed dispersal mode,annual mortality,diameter relative growth rate and relative growth rate under favorable conditions were measured in southern brazil for 66 tree species.Data were subjected to principal components analysis and path analysis.restricted data on saplings and treelets were analyzed through correlation.Important Findingsstudied traits were reduced to four principal components.Principal components analysis produced axes that fit the resource acquisition versus resource-conservation and the height-mortality trade-offs,although the former was split into two distinct axes.seed size and seed dispersal mode appeared independently of these axes.a path model showed that leaf length and specific leaf area caused direct changes in trunk slenderness and,indirectly through growth,affected mortality.Expected trade-offs between growth and survivorship and between wood density and stem slenderness trade-offs were not found.this may result from the lack of extreme pioneers and over-representation of slow-growing hardwood species found in atlantic subtropical forests of south america.this suggests that the fastest growing species in the region do not grow so fast as to compromise wood density and survivorship,but grow fast enough to benefit from increased size.relationships between traits and vital rates seem to be mediated by the assembly process of regional floras,and the relative importance of traits like SLA and wood density may vary between floristic regions.
基金This study was funded by Canadian Natural Resources Limited.
文摘Introduction:Following oil sands mining in Alberta,Canada,the main land management goal is to establish a functioning boreal forest ecosystem,including the understory plant community.One of the challenges with restoring the understory is the presence of non-native species that compete with desirable native species for resources.In a greenhouse experiment,we studied the growth of two native understory species(Galium boreale and Vicia americana)and a non-native invasive species(Matricaria perforata)grown with either intra-or interspecific neighbors across three common land reclamation soils and a nitrogen fertilizer treatment.Results:When grown by itself,V.americana aboveground biomass did not differ among soil or fertilizer treatments,likely due to its ability to fix nitrogen.Growth of M.perforata was directly related to soil nitrogen,and it had the greatest increase in biomass with fertilization.Growth and biomass of G.boreale was less than the other species,and it had the highest mortality in the nitrogen-poor soil.When grown together,the proportional biomass of M.perforata and V.americana varied with soil treatment such that M.perforata was dominant in the high-nitrogen forest floormineral mix treatment while V.americana was dominant in the low-nitrogen peat-mineral mix.Conclusions:Operationally,care should be taken when applying fertilizer to reclamation areas,as it may have an unwanted positive effect on growth for undesirable non-native plants at the expense of native species.In terms of seed mixtures,V.americana may be a good option for low inorganic nitrogen resource soils and G.boreale for high nitrogen resource soils.
