我国盗版童书的网络市场生存模式探析——基于群落建构过程的生态视角

随着电商平台的快速发展,网络市场成为盗版图书泛滥的重灾之地。儿童阅读市场高歌猛进的同时,盗版童书更是在网络渠道中大肆猖獗。然而,只有了解和掌握其生存模式才能实现治理的针对性和有效性。本文基于群落建构过程的生态视角,分别从选择、漂变、成种、扩散四个基本过程,在与正版童书的比较中对网络市场盗版童书的生存模式进行分阶段的细致考察,为网络盗版治理提供新的思路。

Status of two Coreius species in the Three Gorges Reservoir,China

Dam construction alters natural flow regimes which,in turn,cause significant changes in fish communities during and after impoundment. The construction of the Three Gorges Reservoir,from impoundment of the Changjiang(Yangtze) River,China,may have affected native fish species. Thus,the status of two lotic freshwater fish species,Coreius heterodon and C.guichenoti,were monitored in the Three Gorges Reservoir,including fish abundance,individual composition,growth,condition,and mortality. Data on both species were gathered from upstream,midstream and downstream areas of the reservoir and,where available,from studies published before and after dam construction. Lower abundance,slower growth,a less diversified age structure,poorer fish condition(indicated by hepatosomatic index) and higher mortalities were recorded in sites nearest the dam compared with upstream areas. Furthermore,after final impoundment,individual Coreius species inhabiting the area changed,with young individuals becoming more abundant,while upstream of the reservoir the two Coreius species became smaller at a given age. The results show that the status of the two Coreius species was subject to dramatic changes after impoundment.

Riparian plant community structure and assembly processes differed by variations in riverbank curvatures:implications for restoring habitats along the Three Gorges Reservoir

A meandering riverbank plays a vital role in maintaining natural river ecosystems,providing habitats for riparian vegetation.However,dams have significantly altered riverbank shapes.To restore the riparian ecosystems,it is imperative to understand how different riverbank curvatures influence them.This study aims to uncover the ecological impacts of riverbank curvature on the structure and assembly process of plant communities in the riparian zone of the Yangtze River,regulated by the Three Gorges Dam(TGD)in China.We categorized the riparian zones into four types:cove,lobe,wavy and linear shapes.We documented the composition and diversity of riparian plant communities.Our findings revealed that wavy and cove riverbanks exhibited greater species diversity(with Shannon–Wiener diversity index values 1.5×higher)compared to communities along linear riverbanks.Furthermore,the analysis of functional traits indicated that wavy riverbanks promoted the differentiation of plant functional traits,thus enhancing ecosystem functions,with functional dispersion index(FDis)values 1.3 times higher than those of linear riverbanks.Significant variations in the assembly of riparian communities were also observed among different riverbanks,with standardized effect size(SES)values indicating a higher degree of niche differentiation in cove riverbanks(SES=0.4)compared to linear riverbanks(SES=–0.6).These results highlight the ecological importance of diverse riverbank curvatures in influencing the diversity,structure and assembly of riparian communities along the waterway.In summary,this study underscores the necessity of maintaining or restoring various natural morphological curvatures when rehabilitating riparian communities along rivers impacted by human activities.

Feature Analysis and Modeling of the Network Community Structure

Community structure has an important influence on the structural and dynamic characteristics of the complex systems.So it has attracted a large number of researchers.However,due to its complexity,the mechanism of action of the community structure is still not clear to this day.In this paper,some features of the community structure have been discussed.And a constraint model of the community has been deduced.This model is effective to identify the communities.And especially,it is effective to identify the overlapping nodes between the communities.Then a community detection algorithm,which has linear time complexity,is proposed based on this constraint model,a proposed node similarity model and the Modularity Q.Through some experiments on a series of real-world and synthetic networks,the high performances of the algorithm and the constraint model have been illustrated.

The effects of evolutionary and environmental variance on estimates of phylogenetic diversity in temperate forest plots

Aims Phylogenetic diversity metrics can discern the relative contributions of ecological and evolutionary processes associated with the assembly of plant communities.However,the magnitude of the potential variation associated with phylogenetic methodologies,and its effect on estimates of phylogenetic diversity,remains poorly understood.Here,we assess how sources of variation associated with estimates of phylogenetic diversity can pote ntially affect our understanding of plant community structure for a series of temperate forest plots in China.Methods In total,20 forest plots,comprising of 274 woody species and 581 herbaceous species,were surveyed and sampled along an elevational gradient of 2800 m on Taibai Mountain,China.We used multi-model inference to search for the most parsimonious relationship between estimates of phylogenetic diversity and each of four predictors(i.e.type of phylogenetic reconstruction method,phylogenetic diversity metric,woody or herbaceous growth form and elevation),and their pairwise interactions.Important Findings There was nosignificant difference in patterns of phylogenetic diversity when using synthesis-based vs.molecular-based phylogenetic methods.Results showed that elevation,the type of phylogenetic diversity metric,growth form and their interactions,accounted for>44% of the variance in our estimates of phylogenetic diversity.In general,phylogenetic diversity decreased with increasing elevation;however,the trend was weaker for herbaceous plants than for woody plants.Moreover,the three phylogenetic diversity metrics showed consistent patterns(i.e.clustered)across the elevational gradient for woody plants.For herbaceous plants,the mean pairwise distanee showed a random distribution over the gradient.These results suggest that a better understanding of temperate forest comunity structure can be obtained when estimates of phylogenetic diversity include methodological and environmental sources of variation.

The asymmetric relationships of the distribution of conspecific saplings and adults in forest fragments

Aims With the increase of land-use change,habitat fragmentation has become a major factor affecting plant diversity.Generally,when the adult density is high,the survival rate of conspecific saplings may decline and provide more resources and space for other species to maintain a high local species diversity.Therefore,the spatial relationship of conspecific saplings and adults(SRCSA)can regulate plant diversity.However,very few studies have assessed SRCSA within fragmented forests,and we still largely unknown the relationship between SRCSA and species diversity in fragmented landscapes.Methods We calculated the mean strength of SRCSA using the spatial distribution data of saplings and adults with a log-transformed hierarchical offset-power model on 27 islands in a land-bridge island system.The higher strength of SRCSA reflects a more negative relationship between the density of conspecific saplings and adults on an island(i.e.the looser pattern of SRCSA).We tested the relationships among island attributes(i.e.island area,the distance to the mainland—MD,and the distance to the nearest island—ND),SRCSA and species diversity.Important Findings The strength of SRCSA increased with ND.Meanwhile,the species diversity significantly increased with the strength of SRCSA,and island area and the strength of SRCSA independently explained 26%and 6%of variation of species diversity,respectively,and their interactions explained 8%.Shade-intolerant and low-abundant species showed looser patterns of SRCSA.Our study suggests that SRCSA may have the effect of excluding species with a relatively low abundance in isolated island forests,which illustrates the importance of biotic interactions in maintaining plant diversity in fragmented forests.Our results also emphasize that we should consider forest connectivity when testing the conspecific negative density dependence.