Abstract Background: Microorganisms play a crucial role in litter decomposition in terrestrial ecosystems. However, it remains unclear, which effects of leaf litter and root species on bacterial community composition and diversity after one year's decomposition. Methods: The leaf and fine roots litters of Robinia pseudoacacia , Quercus acutissima , Pinus tabulaeformis and Pinus densiflora , which are the dominant afforestation species in Mount Tai, were analysed using the Nylon litterbag method and Illumina Miseq high-throughput sequencing for the amplification of bacterial 16S rRNA V4-V5. We measured the remaining litter mass and the bacterial community composition and assessed the effects of leaf and root litter species on the bacterial community after one-year decomposition periods. Results: (1) The remaining masses of leaf and fine roots litters of the four plant species were significantly influenced by organ type and species. The remaining mass of fine root litter was smaller than that of leaf litter for broad-leaved species, and the opposite result was found for coniferous species. (2) The observed species Chao1 and phylogenetic diversity values were significantly lower for leaf litters than for fine root litter. The community richness index was positively correlated with the C content, C:N and lignin content and negatively correlated with N:P, N content and P content. The bacterial community structure differed significantly among leaf and root litter decomposition for the four species ( p <0.05). The bacterial community structure in leaf litter was most highly correlated with the initial N content and N:P. The bacterial community structure in fine roots was most highly correlated with the lignin content. (3) The bacterial phyla Bacteroidetes , Acidobacteria and Gemmatimonadetes were significantly affected by litter and species type, and the relative abundances of Firmicutes and Chloroflexi were only affected by litter type. The relative abundances of Acidobacteria , Firmicutes and Chloroflexi in fine root litter were higher than those in leaf litter, while the opposite result was found for Bacteroidetes . The bacterial genera Burkholderia-Paraburkholderia , Sphingomonas and Mucilaginibacter were affected by litter type ( p <0.05). The relative abundance of Burkholderia-Paraburkholderia in fine root litter was higher than that in leaf litter, while the opposite result was found for Bradyrhizobium , Sphingomonas and Mucilaginibacter . Pearson correlation analysis showed that the average relative abundance of the dominant phyla and genera was affected by the initial litter properties, especially for Bacteroides , Acidobacteria , Burkholderia , and Sphingomonas . Conclusions: Litter type, interaction between litter type and species were important than species in shaping the bacterial diversity and community composition in decomposing litter. And this were affected by initial chemical properties of the litter.
Elucidating the influence mechanisms of seed germination and seedling growth is important for revealing the natural regeneration of forest plantations. We collected the seeds from 58-year-old Quercus acutissima Carruth. forest, and the seeds were further divided into three classes: large, medium, and small, and sown under the forest gaps (I, 197.82 m2; II, 91.85 m2, III, understory) to observe seed germination and early seedling growth. Precipitation in the study area and soil moisture content in the forest gaps were also observed during the trial period. The results showed that the precipitation in 2019 was similar to that in 2020; both were significantly lower than the precipitation in 2021. The difference in soil water content between gaps I and II was not significant, and both were significantly lower than III. The order of seedling emergence rate in gaps was II > III > I, but the minimum was almost close to zero in I. Large and medium seeds showed significantly greater emergence rate than small seeds. The seedlings of II had higher seedling height, ground diameter, ground diameter relative growth rate, seedling biomass, root surface area, and root volume than those of III. Large seeds had the highest ground diameter, ground diameter relative growth rate, biomass, root mass ratio, root shoot ratio, and root surface area. Correlation analysis showed that seedling biomass was significantly and positively correlated with root surface area and root volume, and significantly and negatively correlated with specific root length and specific root surface area. The regulation of soil moisture in the gap and the adaptability related to seed size were two key factors influencing the seed germination and early seedling growth of Q. acutissima.
Bioretention is an important technology for ecological control of runoff.The purpose of this study was to investigate the coupling effect of in-situ soil and groundwater level on the hydrological performance of bioretention.VADOSE/W was used to simulate the water transport processes during bioretention under a single rainfall event.The effects of four in-situ soil types and two groundwater levels on the surface ponding, underdrain outflow, exfiltration, and runoff regulation effects of bioretention were studied.Under eight geological situations and the rainfall of 0.17 mm/h (6.0 h), the ponding duration and overflow volume of bioretention were 556-649 min and 24.71-39.61mm/m 2 , respectively; the underdrain outflow peak value and duration were 0.549-0.804mm/min and 380-730 min, respectively; the exfiltration volume per unit area from the bottom and lateral of bioretention were 106.79-396.10mm/m 2 and 50.60-147.45mm/m 2 , respectively; and the runoff reduction rate, runoff peak reduction rate, and runoff delay time of bioretention were 53.46%-96.19%,18.43%-68.08%,and 288-318 min, respectively.These results suggest that bioretention without an underdrain and with a relatively smaller K s (saturated permeability coefficient) of in-situ soil might result in longer ponding times and larger overflow volumes.With an increase in K s of in-situ soil, the underdrain outflow weakens, the exfiltration volume increases, and the runoff control effects improve.Although the groundwater level has little effect on surface ponding, it can cause a stronger underdrain outflow.The shallower groundwater level leads to a larger exfiltration volume when the K s of in-soil is much smaller than that of the planting layer and leads to a reduced runoff regulation effect for bioretention without an underdrain.Therefore, when locating and designing bioretention systems, the in-situ soil type and groundwater level should be comprehensively considered to ensure that the runoff control target is achieved.
Abstract Background: Robinia pseudoacacia is a widely planted pioneer tree species in reforestations on barren mountains in northern China. Because of its nitrogen-fixing ability, it can play a positive role in soil and forest restoration. After clear-cutting of planted stands, R. pseudoacacia stands become coppice plantations. The impacts of shifting from seedling to coppice plantations on soil bacterial community and soil properties have not been well described. This study aims to quantify how soil properties and bacterial community composition vary between planted seedling versus coppice stands. Methods : Three 20×20 m plots were randomly selected in each seedling and coppice stand. The bulk soil and rhizosphere soil were sampled in the nine above-mentioned sample plots in the summer of 2017. Bulk soil was sampled at 10 cm from the soil surface using a soil auger. Rhizosphere soil samples were collected by brush. The soil samples were transported to the laboratory for chemical analysis and bacterial community composition and diversity was obtanied through DNA extraction, 16S rRNA gene amplification and high throughput sequencing. Results : The results showed that, compared to seedling plantations, soil quality decreased significantly in coppice stands, but without affecting soil exchangeable Mg 2+ and K + . Total carbon (C) and nitrogen (N) were lower in the rhizosphere than in bulk soil, whereas nutrient availability showed an opposite trend. The conversion from seedling to coppice plantations was also related to significant differences in soil bacterial community structure and to the reduction of soil bacterial α-diversity. Principal component analysis (PCA) showed that, bacterial community composition was similar in both bulk and rhizosphere soils in second generation coppice plantations. Specially, the conversion from seedling to coppice increased the relative abundance of Proteobacteria and Rhizobium , but reduced that of Actinobacteria , which may result in a decline of soil nutrient availability. Mantel tests revealed that C, N, Soil organic matter (SOM), nitrate nitrogen (NO 3 - -N) and available phosphorus positively correlated with bacterial community composition, while a variation partition analysis (VPA) showed that NO 3 - -N explained a relatively greater proportion of bacterial distribution (15.12%), compared with C and SOM. Surprinsingly, N showed no relationship with bacterial community composition, which may be related to nitrogen transportation. Conclusions : The conversion from seedling to coppice stands reduced soil quality and led to spatial-temporal homogenization of the soil bacterial community structure in both the rhizosphere and bulk soils. Such imbalance in microbial structure can accelerate the decline of R. pseudoacacia . This may affect the role of R. pseudoacacia coppice stands in soil and forest restoration of barren lands in mountain areas.
Abstract Background Robinia pseudoacacia is a widely planted pioneer tree species in reforestations on barren mountains in northern China. Because of its nitrogen-fixing ability, it can play a positive role in soil and forest restoration. After clear-cutting of planted stands, R. pseudoacacia stands become coppice plantations. The impacts of shifting from seedling to coppice stands on soil bacterial community and soil properties have not been well described. This study aims to quantify how soil properties and bacterial community composition vary between planted seedling versus coppice stands. Methods Nine 20 m × 20 m plots were randomly selected in seedling and coppice stands. The bulk soil and rhizosphere soil were sampled in summer 2017. Bulk soil was sampled at 10 cm from the soil surface using a soil auger. Rhizosphere soil samples were collected using a brush. The soil samples were transported to the laboratory for chemical analysis, and bacterial community composition and diversity was obtained through DNA extraction, 16S rRNA gene amplification and high-throughput sequencing. Results The results showed that, compared to seedling plantations, soil quality decreased significantly in coppice stands, but without affecting soil exchangeable Mg 2+ and K + . Total carbon (C) and nitrogen (N) were lower in the rhizosphere than in bulk soil, whereas nutrient availability showed an opposite trend. The conversion from seedling to coppice plantations was also related to significant differences in soil bacterial community structure and to the reduction of soil bacterial α-diversity. Principal component analysis (PCA) showed that bacterial community composition was similar in both bulk and rhizosphere soils in second-generation coppice plantations. Specially, the conversion from seedling to coppice stands increased the relative abundance of Proteobacteria and Rhizobium , but reduced that of Actinobacteria , which may result in a decline of soil nutrient availability. Mantel tests revealed that C, N, soil organic matter (SOM), nitrate nitrogen (NO 3 − -N) and available phosphorus positively correlated with bacterial community composition, while a variation partition analysis (VPA) showed that NO 3 − -N explained a relatively greater proportion of bacterial distribution (15.12%), compared with C and SOM. Surprisingly, N showed no relationship with bacterial community composition, which may be related to nitrogen transportation. Conclusions The conversion from seedling to coppice stands reduced soil quality and led to spatial-temporal homogenization of the soil bacterial community structure in both the rhizosphere and bulk soils. Such imbalance in microbial structure can accelerate the decline of R. pseudoacacia . This may affect the role of R. pseudoacacia coppice stands in soil and forest restoration of barren lands in mountain areas.
Abstract Background: Robinia pseudoacacia is a widely planted pioneer tree species in reforestations on barren mountains in northern China. Because of its nitrogen-fixing ability, it can play a positive role in soil and forest restoration. After clear-cutting of planted stands, R. pseudoacacia stands become coppice plantations. The impacts of shifting from seedling to coppice plantations on soil bacterial community and soil properties have not been well described. This study aims to quantify how soil properties and bacterial community composition vary between planted seedling versus coppice stands. Methods: Three 20 × 20 m plots were randomly selected in each seedling and coppice stand. The bulk soil and rhizosphere soil were sampled in the nine above-mentioned sample plots in the summer of 2017. Bulk soil was sampled at 10 cm from the soil surface using a soil auger. Rhizosphere soil samples were collected by brush. The soil samples were transported to the laboratory for chemical analysis and bacterial community composition and diversity was obtanied through DNA extraction, 16S rRNA gene amplification and high throughput sequencing. Results: The results showed that, compared to seedling plantations, soil quality decreased significantly in coppice stands, but without affecting soil exchangeable Mg 2+ and K 2+ . Total carbon (C) and nitrogen (N) were lower in the rhizosphere than in bulk soil, whereas nutrient availability showed an opposite trend. The conversion from seedling to coppice plantations was also related to significant differences in soil bacterial community structure and to the reduction of soil bacterial α-diversity. Principal component analysis (PCA) showed that, bacterial community composition was similar in both bulk and rhizosphere soils in second generation coppice plantations. Specially, the conversion from seedling to coppice increased the relative abundance of Proteobacteria and Rhizobium , but reduced that of Actinobacteria , which may result in a decline of soil nutrient availability. Mantel tests revealed that C, N, Soil organic matter (SOM), nitrate nitrogen (NO 3 − -N) and available phosphorus positively correlated with bacterial community composition, while a variation partition analysis (VPA) showed that NO 3 − -N explained a relatively greater proportion of bacterial distribution (15.12%), compared with C and SOM. Surprinsingly, N showed no relationship with bacterial community composition, which may be related to nitrogen transportation. Conclusions: The conversion from seedling to coppice stands reduced soil quality and led to spatial-temporal homogenization of the soil bacterial community structure in both the rhizosphere and bulk soils. Such imbalance in microbial structure can accelerate the decline of R. pseudoacacia . This may affect the role of R. pseudoacacia coppice stands in soil and forest restoration of barren lands in mountain areas.
Aims Microorganisms play a crucial role in the litter decomposition process in terrestrial ecosystems.Understanding the independent and interactive relationship between fine root decomposition and bacteria community related to substrate characteristics can help to predict the consequences of changes on ecosystem function.Therefore, the aim of this study was to identify fine roots' influences on rhizosphere microbial structure and diversity. MethodsThe decomposition of root litters of four dominant tree species of Mount Taishan (Robinia pseudoacacia (RP), Quercus acutissima (QA), Pinus tabulaeformis (PT) and Pinus densiflora (PD)) was tested in a Yaoxiang Forest Farm.Using Illumina high-throughput sequencing of 16S rRNA genes, bacterial community composition was determined.Composition, diversity and relative abundance of bacteria were calculated for per fine root litter.Important findings (1) Fine root litter decomposition differed significantly among different root types.There was no difference in decomposition rate between broad-leaved species and conifer species.In all species, fine roots of RP and QA were more strongly decomposed than that of PT and PD, and these differences were significant (RP > QA > PT > PD).(2) The number of observed species, operational taxonomic units, Ace index and phylogenetic diversity in broad-leaved species were significantly lower than that in coniferous species.Bacterial
Abstract The aim of this study was to establish the relationships between height and diameter (DBH) of Quercus acutissima in a broadleaved-conifer mixed forests in Mountain Tai in China. Based on the data of Q. acutissima from a 0.6 hm2 permanent forest plot, the relationships between height and DBH were simulated with six empirical models, including Linear, Power, Chapman-Richards, Logistic, Korf and Weibull models, to select the optimization model. There is no significant difference in the predictive power of each growth model. The fitting and test results of each model in this study show that these six model forms have good prediction effects. The results showed that the logistic fitting effect is the best model for Q. acutissima . The Logistic model can be applied to the simulation of tree height and diameter of coniferous and broad-leaved mixed forests in this area.
The soil particle size distribution (PSD) is a fundamental physical property that can affect soil nutrients, soil structure characterization and soil hydraulic properties. However, the effect of plant expansion on soil PSD is not clear. Therefore, in this study, fractal theory was applied to quantitatively describe the PSD. On Mount Tai, artificial afforestation with Robinia pseudoacacia is helpful in restoring ecosystems and improving soil quality. However, clonal spread allows R. pseudoacacia to easily escape cultivation, leading to the formation of mixed forests. Therefore, exploring the effect of R. pseudoacacia expansion on soil PSD is important. The results show that 1) R. pseudoacacia expansion increased the clay and silt contents and reduced the sand content; 2) R. pseudoacacia expansion significantly reduced the capacity dimension, entropy dimension, and correlation dimension and increased the width and asymmetry of the singularity spectra but was unrelated to the entropy dimension/capacity dimension; and 3) the capacity dimension was significantly positively correlated with the sand content and significantly negatively correlated with the silt and clay contents, but the asymmetry of the soil PSD was inconsistent with the capacity dimension. In summary, R. pseudoacacia can reduce the heterogeneity of the PSD by increasing the distribution range and density of the PSD. Our results provide important insight into the effect of plant expansion on soil PSD.
Abstract Background: Robinia pseudoacacia is a widely planted pioneer tree species in reforestations on barren mountains in northern China. Because of its nitrogen-fixing ability, it can play a positive role in soil and forest restoration. After clear-cutting of planted stands, R. pseudoacacia stands become coppice plantations. The impacts of shifting from seedling to coppice stands on soil bacterial community and soil properties have not been well described. This study aims to quantify how soil properties and bacterial community composition vary between planted seedling versus coppice stands. Methods : Nine 20×20 m plots were randomly selected in seedling and coppice stands. The bulk soil and rhizosphere soil were sampled in summer 2017. Bulk soil was sampled at 10 cm from the soil surface using a soil auger. Rhizosphere soil samples were collected using a brush. The soil samples were transported to the laboratory for chemical analysis, and bacterial community composition and diversity was obtained through DNA extraction, 16S rRNA gene amplification and high-throughput sequencing. Results : The results showed that, compared to seedling plantations, soil quality decreased significantly in coppice stands, but without affecting soil exchangeable Mg 2+ and K + . Total carbon (C) and nitrogen (N) were lower in the rhizosphere than in bulk soil, whereas nutrient availability showed an opposite trend. The conversion from seedling to coppice plantations was also related to significant differences in soil bacterial community structure and to the reduction of soil bacterial α-diversity. Principal component analysis (PCA) showed that bacterial community composition was similar in both bulk and rhizosphere soils in second generation coppice plantations. Specially, the conversion from seedling to coppice stands increased the relative abundance of Proteobacteria and Rhizobium , but reduced that of Actinobacteria , which may result in a decline of soil nutrient availability. Mantel tests revealed that C, N, Soil organic matter (SOM), nitrate nitrogen (NO 3 - -N) and available phosphorus positively correlated with bacterial community composition, while a variation partition analysis (VPA) showed that NO 3 - -N explained a relatively greater proportion of bacterial distribution (15.12%), compared with C and SOM. Surprisingly, N showed no relationship with bacterial community composition, which may be related to nitrogen transportation. Conclusions : The conversion from seedling to coppice stands reduced soil quality and led to spatial-temporal homogenization of the soil bacterial community structure in both the rhizosphere and bulk soils. Such imbalance in microbial structure can accelerate the decline of R. pseudoacacia . This may affect the role of R. pseudoacacia coppice stands in soil and forest restoration of barren lands in mountain areas.
'/%3e%3cuse xlink:href='%23a' transform='rotate(23.036 .093 25.536)'/%3e%3cuse xlink:href='%23a' transform='rotate(45.87 1.273 16.18)'/%3e%3cuse xlink:href='%23a' transform='rotate(69.945 .996 12.078)'/%3e%3cuse xlink:href='%23a' transform='rotate(20.66 -19.689 31.932)'/%3e%3c/svg%3e)