Social Scale and Collective Computation:Does Information Processing Limit Rate of Growth in Scale?

Collective computation is the process by which groups store and share information to arrive at decisions for collective behavior.How societies engage in effective collective computation depends partly on their scale.Social arrangements and technologies that work for small-and mid-scale societies are inadequate for dealing effectively with the much larger communication loads that societies face during the growth in scale that is a hallmark of the Holocene.An important bottleneck for growth may be the development of systems for persistent recording of information(writing),and perhaps also the abstraction of money for generalizing exchange mechanisms.Building on Shin et al.,we identify a Scale Threshold to be crossed before societies can develop such systems,and an Information Threshold which,once crossed,allows more or less unlimited growth in scale.We introduce several additional articles in this special issue that elaborate or evaluate this Thresholds Model for particular types of societies or times and places in the world.

孢粉多样性能否反映植被多样性?——以中国东北地区为例

建立现代孢粉多样性与植被多样性的关系,是使用地层化石孢粉数据重建过去植被多样性的基础.然而,中国已有的现代孢粉研究很少关注孢粉多样性及其与植被多样性之间的关系.本研究以中国东北地区为例,首次报道了中国孢粉多样性对区域植被多样性的代表性.选取中国东北地区不同植被类型87个样点的现代孢粉与植被调查数据,评估该区域的孢粉及植被多样性,并通过空间格局对比与相关性分析探讨研究区现代孢粉多样性与植被多样性的关系.此外,尝试采用REVEALS(Regional Estimates of Vegetation Abundance from Large Sites)模型,结合花粉产量(PPEs,Pollen Productivity Estimates)与花粉沉降速率(FSP,Fall Speeds of Pollen)数据对孢粉数据进行校正,以减少不同类群花粉产量与传播能力差异对孢粉-植被多样性关系的影响.研究结果表明:中国东北地区孢粉丰富度与植被丰富度的空间变化格局相似,且两者呈显著正相关(r=0.41,p<0.01);但区域孢粉均匀度与植被均匀度的空间变化格局存在明显的差异,两者之间相关性较弱(r=0.21,p>0.05);孢粉数据经校正后,其多样性与植被多样性之间的空间变化格局差异有所降低,相关性有所增加(丰富度:r=0.50,p<0.01;均匀度:r=0.33,p<0.01).总体而言,中国东北地区的孢粉丰富度能够指示植被丰富度的变化,该多样性指标可用于恢复区域植被多样性变化历史.此外,使用经REVEALS模型校正过的化石孢粉数据重建过去的植被多样性,能够有效提升重建结果的可靠性.

Does palynological diversity reflect floristic diversity?A case study from Northeast China

Fossil pollen data can provide important information of past vegetation diversity,on the basis of established relationship between modern palynological and floristic diversity.However,current studies on modern pollen assemblages in China have not examined this relationship yet.Herein,we report a case study from Northeast China,aiming to investigate the representation of modern palynological diversity to regional floristic diversity.A total of 87 sets of modern pollen and vegetation data from various vegetation types were applied to assess modern palynological diversity and floristic diversity in Northeast China,and the relationship between palynological and floristic diversity was studied using spatial pattern comparison and correlation analysis.Moreover,to reduce representation bias related to pollen production and dispersal,we calibrated pollen data using the Regional Estimates of Vegetation Abundance from Large Sites(REVEALS)model with Pollen Productivity Estimates(PPEs)and Fall Speeds of Pollen(FSP).The results show that the spatial variations of palynological and floristic richness among vegetation types are similar,and have a good positive correlation(r=0.41,p<0.01).However,palynological evenness presents a different spatial pattern from floristic evenness,with a weaker positive correlation(r=0.21,p>0.05).The calibration on pollen data using REVEALS model minimized the differences in spatial patterns between palynological and floristic diversity,and improved the correlations between them(richness,r=0.50,p<0.01;evenness,r=0.33,p<0.01).Our study indicates that palynological richness in Northeast China could reflect regional floristic richness in general,and the calibration with REVEALS model is recommended for reconstructing past floristic diversity from pollen data.