Similarity between seed rain and neighbouring mature tree communities in an old-growth temperate forest

Seed distribution and deposition patterns around parent trees are strongly aff ected by functional traits and therefore infl uence the development of plant communities.To assess the limitations of seed dispersal and the extent to which diaspore and neighbouring parental traits explain seed rain,we used a 9-year seed data set based on 150 seed traps in a 25-ha area of a temperate forest in the Changbai Mountain.Among 480,598 seeds belonging to 12 families,17 genera,and 26 species were identifi ed,only 54%of the species with mature trees in the community were represented in seeds collected over the 9 years,indicating a limitation in seed dispersal.Understory species were most limited;overstory species were least limited.Species with wind-dispersed seed had the least limitation,while the lowest similarity in species richness was for animal-dispersed species followed by gravity-dispersed species;fl eshy-fruited species had stronger dispersal limitations than dry-fruited species.Generalized linear mixed models showed that relative basal area had a signifi cant positive eff ect on seed abundance in traps,while the contribution of diaspore traits was low for nearly all groups.These results suggest that tree traits had the strongest contribution to seed dispersal and deposition for all functional groups examined here.These fi ndings strengthen the knowledge that tree traits are key in explaining seed deposition patterns,at least at the primary dispersal stage.This improved knowledge of sources of seeds that are dispersed could facilitate greater understanding of seedling and community dynamics in temperate forests.

Local-scale drivers of multi-stemmed tree formation in Acer,in a temperate forest of Northeast China

Acer is an important genus in temperate forests in Northeast China.Individual Acer trees can re-sprout from the root collar and can occur in clonal units,either as a single-stemmed or multi-stemmed tree.However,the factors that induce multiple-stems in Acer remain only partly understood.In this study,we determined the relative importance of abiotic and biotic variables in driving the production of multiple-stems in this genus,within a 25-hm^2experimental forest dynamics plot in Changbaishan(CBS)temperate forest.We used generalized linear mixed models to perform analyses at two levels(community-and specieslevel).We found seven Acer species in total within the plot,where they form a key part of the forest community.Our results show that abiotic factors play a more important role in producing multi-stemmed trees at the community level in CBS.At the species level,the relative importance of different factors varied among species.Shrub species tended to have a higher frequency of multi-stemmed trees under stressful conditions,whereas tree species tended to have more multi-stemmed trees in more suitable habitat.Our results indicate that the relative importance of different factors influencing the frequency of multi-stemmed individuals in Acer differs at the community and species level in the temperate forest.

The effect of tree size,neighborhood competition and environment on tree growth in an old-growth temperate forest

Aims Understanding the controls influencing tree growth is central to forest ecology.Although many factors such as tree size,neighborhood competition and environmental variables,have been proposed as being important in explaining patterns of tree growth,but their relative contributions are still subject to debate.We aimed to examine the relative importance of tree size,local abiotic conditions and the density and identity of neighbors on tree growth in an old-growth temperate forest in northeast china.Methods We used linear mixed models with data from a 25 ha(500×500 m)broad-leaved Korean pine(Pinus koraiensis)mixed forest perma-nent plot to examine the relative importance of these local drivers on tree growth at three organizational levels(community,guild and species).Subplot was included as a random effect to account for spatial autocorrelation in growth of trees located within the same subplot,and species was included as a random effect to account for variation among species in growth.Important Findings Tree size was typically the most important predictor of growth,followed by neighborhood competition and then soil nutrients.The correlation of tree size to growth varied from strongly positive for large trees and medium trees to slightly positive for small trees.The effect of neighbor-hood competition on growth showed weak negative density dependence as indicated by slightly negative effect of total basal area of neighbors and the proportion of conspecific neighbors.Environmental factors influenced growth of very common species,smaller tree-size classes and shade-tolerant species.We concluded that the relative importance of variables driving patterns of tree growth varied greatly among tree size classes,shade tolerance and abundance classes in this temperate for-est.These results provide critical information for future studies of forest dynamics and offer insight into forest management in this region.

Intraspecific trait variation improves the detection of deterministic community assembly processes in early successional forests,but not in late successional forests

Aims Intraspecific trait variation(ITV)has been increasingly recognized to play an important role in understanding the underlying processes influencing community assembly.However,gaps remain in our understanding of how incorporating ITV will influence the relative importance of deterministic(e.g.habitat filtering,limiting similarity)and stochastic processes in driving community assembly at different successional stages.Methods We used data for eight functional traits from 55 woody species in early(24 ha)and late(25 ha)successional temperate forest plot in northeast China.We employed an approximate Bayesian com-putation approach to assess the relative contribution of stochastic processes,habitat filtering and limiting similarity in driving commu-nity structure.We then compared the results with and without intra-specific trait variation to investigate how ITV influences the inferred importance of each process.Important Findings We found that when analyzing interspecific trait variation only(i.e.without ITV),stochastic processes were observed most frequently in driving community composition,followed by habitat filtering and limiting similarity in both forests.However,ITV analyses showed that the relative importance of both deterministic processes(habitat filtering and limiting similarity)increased in early successional for-est,but remained virtually unchanged in late successional forest.Our study reveals the distinctive influence of ITV on the inference of underlying processes in a context of succession and reinforces the need to estimate ITV for making correct inferences about underlying ecological processes.