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.

中国森林生物多样性监测网络:二十年群落构建机制探索的回顾与展望

中国森林生物多样性监测网络(CForBio)目前已经沿纬度梯度从寒温带到热带布设23个大型森林动态样地,监测1,893种木本植物,代表我国木本植物种类的近1/6。CForBio的主要目标之一是研究森林群落的构建机制。本文综述了近20年来CForBio在群落构建机制探索方面取得的进展,包括生物多样性时空格局、生境过滤、生物相互作用、局域扩散和区域因素以及利用新技术取得的新认知等。CForBio研究发现:(1)生境过滤和扩散限制共同决定种–面积关系及β多样性等多样性格局,但二者的相对作用在不同样地及不同尺度存在差异;(2)生境过滤对局域群落构建的作用广泛存在,但很难量化其对群落构建的重要性;(3)同种负密度制约在不同气候带样地普遍存在,负密度制约的强度主要由植物菌根类型介导,并随植物生活史类型、功能性状及环境变化而变化;(4)扩散限制在局域群落构建中发挥关键作用,而区域因素如区域地质历史、区域物种库大小等塑造不同生物地理区群落之间的生物多样性差异;(5)宏观和微观两个方面的新技术促进群落构建机制的研究。在宏观方面,遥感技术以低成本使大范围、多尺度的连续群落生物多样性监测和时空比较研究成为可能;另一方面,叶绿体基因技术和代谢组学等微观技术能促进推导群落构建的分子机制。同时,本文还总结了以往研究的不足,并展望了基于森林动态样地开展群落构建机制研究的未来发展,特别强调了:(1)关注群落构建研究中的尺度问题;(2)深入开展多维度(物种、功能和系统发育)、多营养级生物互作相关的研究;(3)拓展全球变化对群落构建影响的研究;(4)融合观测–实验–模型多种手段开展群落构建机制的研究;(5)连结“群落构建理论研究”和“森林管理实践”。总之,中国森林生物多样性监测网络的长期监测和联网研究是森林群落构建机制研究的重要基础,也是推动群落构建理论、解决森林管理难题的重要平台。

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.