朱书玉 Zhu Shuyu, 杜宁 Du Ning, 冯宗炜 Feng Zongwei, 葛秀丽 Ge Xiuli, 卢鹏林 Lu Penglin, 王伟华 Wang Weihua, 谭向峰 Tan Xiangfeng, 王仁卿 Wang Renqing, 王炜 Wang Wei, 王成栋 Wang Chengdong, 刘月良 Liu Yueliang, 蔡云飞 Cai Yunfei, 王越 Wang Yue, and 郭卫华 Guo Weihua
The Yellow River Delta,one of China′s three major river deltas,has recently been the subject of numerous important research projects.Soil is an important environmental factor in the delta and heavily influences plant physiology and vegetation distribution.In previous studies,soil salinity and moisture have been proven to be main driving forces of terrestrial vegetation succession in the Yellow River Delta.However,vegetation in the Yellow River Delta is prone to retrograde succession and secondary succession resulting from both natural forces and human disturbance.Currently,changing salinity patterns and soil conditions in the Yellow River Delta are causing a deeper penetration of salinity into the soil.This change in soil salinity has been brought on by a rise in sea level and other natural or societal causes such as dredging,shoreline modifications,and so on,and the local vegetation is adapting to these changes out of necessity.Our research looked at the relationships between community diversity and soil conditions as well as analyzing the classification of the coastal meadows in the Yellow River Delta.Gaining an understanding of these relationships will not only enlighten us on the relationships between vegetation and soil;it also has theoretical significance for vegetation conservation and restoration in the Yellow River Delta.Sixty-seven vegetation quadrats were selected in June,2010,and nine soil characteristics were analyzed,including soil moisture content(MC),soil electrical conductivity(EC),soil pH(pH),total carbon(TC),total nitrogen(TN),total phosphorus(TP),available nitrogen(AN),available phosphorus(AP) and available potassium(AK).Vegetative analysis of the quadrants found 52 species,belonging to nineteen families and forty-six genera.The abundance of Compositae,Gramineae and Chenopodiaceae,the three plant families with the largest number of species found during this study,demonstrates their wide range of adaptability.Also,the species of the Chenopodiaceae are mostly salt-tolerant,and some of them are edificators,or environment-forming species,in some communities,so this family is of special importance to the Yellow River Delta vegetation communities.Many past ecological studies confirm the rationality of the wide use of Canonical Correspondence Analysis(CCA) and Two-way Indicator Species Analysis(TWINSPAN) in quantitative vegetation ecology.Canonical Correspondence Analysis was performed to analyze the relationships between the vegetation quadrats and the nine soil factors.The CCA results show the first two axes explained 46.4% of the variance within the species-environmental relationships,and electrical conductivity and moisture content most heavily influenced the community distribution.Using TWINSPAN,we classified the quadrats into seven communities as follows: Community.Aeluropus sinensis,Com.Phragmites australis,Com.Imperata cylindrica+Phragmites australis,Com.Cynanchum chinense,Com.Phragmites australis-Suaeda glauca,Com.Phragmites australis-Suaeda salsa and Com.Suaeda salsa.The seven communities were classified into three groups along the first axis of the CCA: Com.Suaeda salsa,Com.Phragmites australis-Suaeda salsa and other meadow communities.The results indicate the succession series of coastal meadow in the Yellow River Delta develops along the salinity gradient,and may also indicate a transitional role for the Com.Phragmites australis-Suaeda salsa,a role which should be explored in the future studies.The Shannon-Wiener(H′) and Simpson(D) indices were calculated.Correlation analysis shows species diversity had a highly significant negative correlation with EC,AP and AK(P0.01),and a significant positive correlation with pH(P0.05).In this study,the combination of CCA and TWINSPAN performed well since classification increased the effectiveness of ordination,and ordination helped one understand the classification results.These findings helped the authors develop a theoretical basis for vegetation conservation and restoration in the Yellow River Delta.