Life forms affect beta-diversity patterns of larch forests in China

Beta-diversity reflects the spatial changes in community species composition which helps to understand how communities are assembled and biodiversity is formed and maintained. Larch(Larix) forests, which are coniferous forests widely distributed in the mountainous and plateau areas in North and Southwest China, are critical for maintaining the environmental conditions and species diversity. Few studies of larch forests have examined the beta-diversity and its constituent components(species turnover and nestedness-resultant components). Here, we used 483 larch forest plots to determine the total betadiversity and its components in different life forms(i.e., tree, shrub, and herb) of larch forests in China and to evaluate the main drivers that underlie this beta-diversity. We found that total betadiversity of larch forests was mainly dependent on the species turnover component. In all life forms,total beta-diversity and the species turnover component increased with increasing geographic, elevational, current climatic, and paleoclimatic distances. In contrast, the nestedness-resultant component decreased across these same distances. Geographic and environmental factors explained 20%-25% of total beta-diversity, 18%-27% of species turnover component, and 4%-16% of nestedness-resultant component. Larch forest types significantly affected total beta-diversity and species turnover component. Taken together, our results indicate that life forms affect beta-diversity patterns of larch forests in China, and that beta-diversity is driven by both niche differentiation and dispersal limitation. Our findings help to greatly understand the mechanisms of community assemblies of larch forests in China.

Analysis of radiation diffusion of COVID-19 driven by social attributes

This paper first estimated the infectious capacity of COVID-19 based on the time series evolution data of confirmed cases in multiple countries. Then, a method to infer the cross-regional spread speed of COVID-19 was introduced in this paper, which took the gross domestic product(GDP) of each region as one of the factors that affect the spread speed of COVID-19 and studied the relationship between the GDP and the infection density of each region(China's Mainland, the United States, and EU countries). In addition, the geographic distance between regions was also considered in this method and the effect of geographic distance on the spread speed of COVID-19 was studied. Studies have shown that the probability of mutual infection of these two regions decreases with increasing geographic distance. Therefore, this paper proposed an epidemic disease spread index based on GDP and geographic distance to quantify the spread speed of COVID-19 in a region. The analysis results showed a strong correlation between the epidemic disease spread index in a region and the number of confirmed cases. This finding provides reasonable suggestions for the control of epidemics. Strengthening the control measures in regions with higher epidemic disease spread index can effectively control the spread of epidemics.

Near is more:learning efficiency in research and development innovation among interlocking firms

Research question/issue:This study examines whether geographic proximity produces a proximity preference as interlocking firms observe each other and learn innovative behaviors through information transmission among interlocking directors.Research findings/insights:We study the performance of A-share-listed companies in China from 2007 to 2017 on the basis of resource dependence theory,agglomeration effect theory,and Porter’s competitive theory.When target firms learn about research and development–related innovation behaviors from interlocking firms closer to them,they experience more efficient learning effects and have improved convergent traits.Moreover,this proximity advantage increases the willingness of the target firm to communicate with and learn from interlocking firms closer to them.Highly developed areas and research and development–intensive industries positively affect the learning efficiency of interlocking firms.Theoretical/academic implications:Our conclusion is consistent with resource dependence theory;target firms in highly developed areas are more willing to imitate and study nearby interlocking firms to maintain their peer relations,innovation potential,and competitiveness.Our conclusion is also consistent with competition theory,which states that the exchange of information between target firms in highly research and development–intensive industries and distant interlocking firms increases innovation differentiation,innovation potential,and competitiveness,even when such exchange has a high cost.Practitioner/policy implications:The results support resource dependence theory and peers’effects.The information obtained by interlocking directorates through external social relations guides firm decision-making,and closer distances reveal more obvious effects.

Biotic Homogenization Caused by the Invasion of Solidago canadensis in China

Although studies argue that invasive species can cause biotic differentiation, some cases show that biological invasions actually decrease biodiversity through biotic homogenization. The concept of biotic homogenization through the invasion of a certain serious invasive plant species merit more studies. Hence, we used field surveys to quantitatively compare invasive populations of Solidago canadensis （SC） in China with the control sites （adjacent sites to SC present sites yet without the species） and SC native populations in the USA. We found that plant communities in SC invaded habitats shared similarities with those in SC native ranges. Bray-Curtis similarity clearly showed that the composition of plant communities in SC invaded habitats were similar to those in SC native ranges. Both in the native and introduced range, plant communities with SC present were characterized by SC being dominant, significantly lower species richness, or-diversity and p-diversity, as well as a decrease in the correlation coefficient between geographic distance and floristic similarities. SC favors fertile and moist loam habitat, while it dominated in various habitats in China, where more than 20 different dominants should have occurred. In conclusion, serious invasive species can quickly remodel and homogenize diverse communities by dominating them.

Does distance matter in foreign direct investment sub-national location choice?Evidence from China

Multinational enterprises(MNEs)make investment decisions according to the distance factors at a sub-national level.This paper made estimates using the gravity model with provincial foreign direct investment(FDI)data from 2000 to 2012 and employed three concepts of distance.Our emprical results indicate that geographic distance and cultural distance have significant negative effects on FDI flow,whereas economic distance has a significant positive effect.It suggests that FDI prefers to locate in regions that are geographically and culturally close but economically distant from the home country,which further implies that FDI in China is dominated by vertical FDI.Our findings suggest that Chinese provincial governments should place emphasis on attracting FDI from culturally close countries and provide institutional support to encourage and promote horizontal FDI.

Molecular Genetic Variation in a Clonal Plant Population of Leymus chinensis （Trin.） Tzvel.

Randomly amplified polymorphic DNA （RAPD） analysis was used to investigate the genetic variation among populations, between populations, and within populations, relationships between genetic distance and geographic distance, and the molecular variation and population size. The effects of geographic and genetic distances, as well as of genetic differentiation and population size, on genetic variations of Leymus chinensis （Trin.） Tzvel. are discussed. The present study showed that there was significant RAPD variation between the Baicheng region population and the Daqing region population, with a molecular variance of 6.35% （P 〈 0.04）, and for differentiation among area populations of the Daqing region, with a molecular variance of 8.78% （P 〈 0.002）. A 21.06% RAPD variation among all 16 populations among two regions was found （P 〈 0.001）, as well as 72.59% variation within populations （P 〈 0.001）. Molecular variation within populations was significantly different among 16 populations.