| Silicon is the second most abundant element in the earth’s crust after oxygen,and it is essential for plant growth and improved stress tolerance.Most existing studies have focused on the effects of exogenous silicon application on plant(i.e.,crop)growth,but there is a lack of understanding of plant silicon content differences and their environmental influences,which directly limits the direct application of silicon in practical production activities.Are these differences in silicon content within trees for woody plants.Are these differences dependent on the soil properties of the forest.These questions need to be answered.Based on the Tree Species Comparative Test Forest of European Investment Bank loan project Shandong Ecological Afforestation,the study selectes 15 common tree species in the hilly area of central Shandong(including 10 tree species and 5 shrub species).The comparison of silicon content in leaves and branches of tree species and the analysis of soil characteristics of each species are used to elucidate the differences in silicon content in tree species and its correlation with habitat soil,to provide a theoretical basis for an in-depth understanding of the interrelationship between afforestation tree species and standing soil,and to provide a theoretical basis for forest soil management in the hilly areas of central Shandong Province.This study found that:(1)There are significant differences in silicon content in 15 tree species,which 12 species have significantly greater leaf silicon content than branch silicon content,and leaf silicon content and branch silicon content have a significant positive correlation(P<0.05).There is no significant correlation between the content of silicon in tree species and the content of available silicon and water-soluble silicon in soil(P>0.05).It shows that the silica content in tree species is influenced by species characteristics,with tree species having higher silica content and shrub species having lower silica content.(2)Silica content in soils of different tree species is related to soil properties.The available and water-soluble silicon contents in the soils of the 15 tree species differed significantly,with Juglans regia soils having significantly higher available and water-soluble silicon contents than the rest of the tree species(P<0.05),while Gleditsia sinensis is low.Correlation analysis shows that available and water-soluble silicon content in soil are significantly positively correlated with total soil organic carbon,total nitrogen,nitrate nitrogen,and sucrase activity(P<0.01),but negatively correlated with p H(P<0.05).Thus,soil physicochemical properties can significantly affect the amount of silicon in the soil.(3)Soil available and water-soluble silicon contents are affected by the specific bacterial community in the soil.The soil of 15 tree species are grouped into 4 groups based on available and water-soluble silicon content.The predicted functional analysis of the soil bacterial community for each group shows that chemo-energetic heterotrophic and aerobic heterotrophic bacteria together accounted for 62.36% to 63.96% of the whole bacterial community,while silica-functional bacteria(Bacillus,Pseudomonas,Burkholderia,Enterobacter)in soil are significantly correlated with soil available and water-soluble silica.Therefore,on the one hand,the formation of available and water-soluble silicon in soil depend on the decomposition of silica-containing minerals by silicolytic bacteria.On the other hand,they depend on the interaction of soil silicolytic bacteria and other functional bacteria to decompose the litter residues in soil.(4)Soil bacteria communities are affected by tree species,soil physical and chemical properties and enzyme activities.Soil bacterial communities play an important role decomposition and nutrient cycling in soil.Soil bacterial communities are affected by a combination of physicochemical properties such as tree silicon content,soil available silica,water-soluble silica,total nitrogen,total phosphorus total organic carbon,p H and soil enzyme activity.In summary,there are significant differences in silicon content in trees between species.The silica content in tree species is higher,while the silica content in shrub species is lower.The silica content of trees is not affected by the content of available silicon and water-soluble silicon in the soil.The available and water-soluble silicon content of soils are influenced by soil properties such as total organic carbon,total nitrogen,p H,soil characteristics and by specific functional bacterial communities. |
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