Effects of Topographical and Edaphic Factors on the Distribution of Plant Communities in two Subtropical Karst Forests,Southwestern China

Relationships between topography,soil properties and the distribution of plant communities on two different rocky hillsides are examined in two subtropical karst forests in the Maolan National Natural Reserve,southwestern China.Surveys of two 1-ha permanent plots at each forest,and measurements of four topographic and thirteen edaphic factors on the slopes were performed.Twoway Indicator Species Analysis(TWINSPAN) and Detrended Canonical Correspondence Analysis(DCCA) were used for the classification of plant communities and for vegetation ordination with environmental variables.One hundred 10m×10m quadrats in each plot were classified into four plant community types.A clear altitudinal gradient suggested that elevation was important in community differentiation.The topography and soil explained 51.06% and 54.69% of the variability of the distribution of plant species in the two forest plots,respectively,indicating both topographic factors(eg.elevation,slope and rock-bareness rate) and edaphic factors(e.g.total P,K and exchangeable Ca) were the important drivers of the distribution of woody plant species in subtropical karst forest.However,our results suggested that topographical factors were more important than edaphic ones in affecting local plant distribution on steep slopes with extensive rock outcrops,while edaphic factors were more influential on gentle slope and relatively thick soil over rock in subtropical karst forest.Understanding relationships between vegetation and environmental factors in karst forest ecosystems would enable us to apply these findings in vegetation management strategies and restoration of forest communities.

A Review for the Influential Factors in E-WOM Research

Although substantial literature is available on customer reviews or e-WOM （electronic word of mouth）, the topic is still under development and offers potential opportunities for further research. Since the topic is still at the stage of development, a review of the literature on customer reviews with the objective of summarizing existing findings will initial further studies on the growth of e-WOM technologies. This paper reviews the literature on e-WOM using a suitable classification scheme to identify the gap between theory and practice. Aiming to provide useful insights into the anatomy of e-WOM literature and be a good source for anyone who is interested in e-WOM, nine categories of findings are ultimately presented based on dependent-independent-variable relationship, along with a comprehensive list of reference. The paper ends up with discussions on future directions for research.

A two-step robust adaptive filtering algorithm for GNSS kinematic precise point positioning

In kinematic navigation and positioning,abnormal observations and kinematic model disturbances are one of the key factors affecting the stability and reliability of positioning performance.Generally,robust adaptive filtering algorithm is used to reduce the influence of them on positioning results.However,it is difficult to accurately identify and separate the influence of abnormal observations and kinematic model disturbances on positioning results,especially in the application of kinematic Precise Point Positioning(PPP).This has always been a key factor limiting the performance of conventional robust adaptive filtering algorithms.To address this problem,this paper proposes a two-step robust adaptive filtering algorithm,which includes two filtering steps:without considering the kinematic model information,the first step of filtering only detects the abnormal observations.Based on the filtering results of the first step,the second step makes further detection on the kinematic model disturbances and conducts adaptive processing.Theoretical analysis and experiment results indicate that the two-step robust adaptive filtering algorithm can further enhance the robustness of the filtering against the influence of abnormal observations and kinematic model disturbances on the positioning results.Ultimately,improvement of the stability and reliability of kinematic PPP is significant.