Weed Community Characteristics And Its Association With Environmental Factors In Citrus Dominant Industrial Belt In China

Citrus is one of the most important fruits in China and the indispensable economically crop in the agricultural system.Weed control is a key aspect for citrus production in citrus orchards.The variety of weeds with complex and diverse vegetation that adversely affect citrus production.Currently,this study systematically investigated the occurrence of weeds in citrus orchards in Citrus dominant Industrial Belt in China citrus production area.1.A total of 66 families and 227 species of weeds were found through investigated weeds structure and species diversity in the citrus producing areas of the Citrus dominant Industrial Belt in China.Most of them were dicotyledonous plants of the angiosperm phylum.These weeds were mainly perennial herbaceous life and growth forms,and a few vines and tree seedlings.2.Based on the weed importance value results,20 dominant weed species were identified in the citrus production areas of the Citrus dominant Industrial Belt in China.Among them,Digitaria sanguinalis was the highest importance value overall,as well as it was the first one in Hunan,Jiangxi,Yunnan and Zhejiang provinces.But in Sichuan province,Alternanthera philoxeroides has the highest importance value.The species diversity and richness analysis results showed that Zhejiang province has the highest species diversity and richness,Hunan province has the lowest species diversity,Yunnan province has the lowest species richness and Hubei province has the highest species evenness.3.According to TWINSPAN classification method,the weed communities in the citrus producing areas of the Citrus dominant Industrial Belt in China were divided into 15 clusters.Furthermore,they were divided into 5 communities based on the species composition and biological characteristics of different clusters.The different communities and clusters were well separated in the DCA ordination diagram.Transitional communities(II)and Chenzhou hill communities(IV)were distributed horizontally along DCA ordination axis 1,indicating that DCA ordination axis 1 might reflect changes in environmental factors such as topography;Yunnan communities(V),communities II and moisture-loving communities(III)were distributed vertically along DCA ordination axis 2,indicating that DCA axis 2 might be influenced by factors such as latitude and altitude.Moreover,The CCA ordination results indicated that the weed community structure in the citrus production area of the Citrus dominant Industrial Belt in China was mainly influenced by precipitation,temperature,elevation,latitude and longitude.4.The niche widths of 20 dominant weeds in the citrus producing areas of the Citrus dominant Industrial Belt in China,such as Digitaria sanguinalis and Eleusine indica,varied widely.And the overall niche overlap values were low,which indicated that the weeds had little competition for resource use in the producing areas,and the dominant weeds were often distributed regionally and patchily.In addition,the interspecific affinity results showed that the weed communities in the production area were negatively associated.And the association between dominant weed species was also mainly negative.Moreover,the degree of interspecific association was low,and the species had more mutual exclusion and competition than cooperation.These results suggested that the community were in an unstable primary successional stage.The study clarified the weeds community structure and species diversity in citrus orchards of the production area.Additionally,the research analyzed the relationships between the dominant weed species in citrus orchards of the production area from the perspectives of ecological niche and interspecific affinity.And clarified the correlation between enviromentor and weed community in the citrus production areas of the Citrus dominant Industrial Belt in China.These results are important for guiding weeds scientific control in citrus orchards.