[Illumina Miseq sequencing-based fungal community of rhizosphere soils along root orders of poplar plantation]. / åŸºäºŽé«˜é€šé‡æµ‹åºçš„æ¨æ ‘äººå·¥æž—æ ¹é™ åœŸå£¤çœŸèŒç¾¤è½ç»“æž„.

The study on microbial community composition in rhizosphere soils surrounding different order roots is of great significance for understanding the interactions between roots and microbes. Using Illumina Miseq sequencing technology, this study analyzed the differences of fungal community structure in bulk soils and rhizosphere soils surrounding different root orders of poplar (Populus × euramericana 'Neva') tree. The microbial species annotation showed that 128, 124, 130 and 101 fungal genera were classified in the rhizosphere soils around 1-2 order roots (R1), 3 order roots (R2), 4-5 order roots (R3) and in the bulk soils (NR), respectively. The differences of present fungal genera indicated a selectivity mechanism driving fungal community assembly in poplar rhizosphere soils. There were seven fungal genera with more than 1% of relative abundance in rhizosphere soils. Trichoderma was the dominant fungal genus in R1. Trichosporon and Aspergillus were the dominant fungal genera in R2 and R3, respectively. Alpha (α) diversity indices showed that the fungal diversity was significantly different among root orders. Specifically, the diversity of soil fungal community in the rhizosphere soils around lower order roots was significantly higher than that of higher order roots (P＜0.05). Beta (ß) diversity indices showed that the dissimilarity of fungal community composition increased along with the root orders. All these results implied the different composition and structure of fungal community are closely related with the function of fine root orders.

[Seasonal dynamics of quantitative and morphological traits of poplar fine roots and their differences between successive rotation plantations].

Based on the fine root samples of the first and second generations of poplar (Populus x euramericana ' Neva'), this study examined the response of quantitative and morphological traits of fine roots of different orders and the difference between generations. The results showed that, the quantitative traits of fine roots, such as root length, root surface area and root biomass, presented obvious seasonal variation, and the fine root traits had obvious difference among root orders. The quantitative traits of lower-order fine roots showed significant seasonal difference, and the fine root biomass increased in the growing season and then decreased significantly. The specific root length (SRL) of higher-order roots also showed significant change with season, while the root length density (RLD) and root tissue density (RTD) changed a little. The successive rotation resulted in the significant increase of root length, root biomass, SRL and RLD of 1-2 orders in the growing season. The quantitative traits of first order root significantly positively correlated with soil temperature and moisture, and significantly negatively correlated with the soil organic matter and soil available nitrogen content. However, the quantitative traits of second order root only showed significant correlation with soil nutrient content. The seasonal dynamics of poplar fine roots and the difference between successive rotation plantations implied carbon investment change of poplar to roots. Soil nutrient deficiency induced more carbon investment into roots, and this carbon allocation pattern might affect the aboveground productivity of poplar plantation.

[Ionic homeostasis of Populus ×euramericanna 'Neva' influenced by irrigation with magne-tized brackish water.] / 磁化微咸水灌溉对欧美杨I-107离子稳态的影响.

The research aimed to study the characteristic of ionic homeostasis of annual seedlings of Populus ×euramericanna under irrigation with non-magnetized and magnetized 0 or 4.0 g·L-1 NaCl solution for 30 days in the growing season. The ion contents of K+, Na+, Ca2+ and Mg2+ in the lea-ves and roots were measured by atomic absorption spectrophotometry (AAS). The ion homeostasis coefficient (K) and the ion selective transport coefficient (SXi,Na) from root system to leaves were analyzed. Compared with the unsalted treatment, the ion contents of Na+ and Ca2+, SK,Na and SMg,Na increased in leaves and roots under NaCl stress, while the K+ and Mg2+ ion content, the ratio of K+/Na+ and SCa,Na decreased. Compared with the non-magnetized NaCl solution (NM), the magnetized NaCl solution (M) made leaves and roots maintain lower content of Na+ but higher content of K+ and the K+/Na+. Compared with the NM, the content of Ca2+ decreased while that of Mg2+ increased in the M. In M, K was higher than that in NM, and there was significant increase in the leaves than that in the roots. The ratios of SK,Na and SMg,Na in leaves and roots in M were higher than those in NM, while the ratio of SCa,Na was lower. The magnetized NaCl solution decreased Na+ content, increased K+, Ca2+ and Mg2+ content, and maintained higher K+/Na+, which was beneficial for the physiological metabolism of the whole plant. So, the magnetic effect could promote the re-establishment of ionic homeostasis by ions selective absorption and transportation under NaCl stress.

[Characteristics of phosphate-solubilizing microbial community in the soil of poplar plantations under successive-planting and rotation.] / æ¨æ ‘äººå·¥æž—è¿žä½œä¸Žè½®ä½œå¯¹åœŸå£¤è§£ç£·å¾®ç”Ÿç‰©ç±»ç¾¤çš„å½±å“.

The metagenome sequencing was used to compare the difference of six soil samples, the rhizosphere soil of the first and the second rotation poplar plantations (RSP1, RSP2), the bulk soil of the first and the second rotation poplar plantations (BSP1, BSP2), the soil of rotated peanut field (RPS) and the abandoned land soil (ALS) after poplar clear cutting, in phosphate-solubili-zing microbial community and abundance of phosphatase gene (PG) in a poplar plantation. The results showed that microorganisms from nine genera were related to phosphorus cycle with Bacillus and Pseudomonas being the dominant. The abundance of PSMs was highest in ALS, followed by RPS, RSP2 and BSP2, RSP1 and BSP1, respectively. There was a significant difference of PSMs among the six soil samples. After poplar clear cutting, the abundance of Bacillus and Pseudomonas in RPS and ALS increased significantly, whereas that of Arthrobacter, Bradyrhizobium and Streptomyces decreased. However, in the rhizosphere soil of poplar plantations, an opposite pattern appeared when comparing RSP2 to RSP1. Bacillus and Pseudomonas were more abundant in rhizosphere soils than in bulk soil, while Arthrobacter, Bradyrhizobium and Streptomyces were higher. The abundance of PG presented the regularity of RSP1 and BSP1 > ALS > RSP2 and BSP2 > RPS. Rhizosphere had a more significant effect in the successive rotation poplar plantations than in the second rotation plantation. An even lower phosphatase gene's abundance was shown in rhizosphere soil than in bulk soil. The number of PSMs was negatively correlated with the content of phenolic acids but positively correlated with pH value.

[Seasonal dynamics of carbon and nitrogen in fine roots and their differences between successive rotation poplar plantations].

In this study, poplar fine roots in two successive rotation plantations were sampled over seasons. Root samples were grouped from first to five orders to examine the seasonal dynamics of carbon and nitrogen contents of poplar fine roots with orders, and compared their differences between two successive rotation plantations, and finally to find the relationships between the fine root growth and the productivity decline of successive rotation poplar plantations. The results showed that non-structure carbohydrates (NSC) content increased significantly with root orders, while nitrogen content decreased. The contents of total carbon and NSC were significantly related to total nitrogen content. Root orders explained 98.2% variance of carbon and nitrogen contents of poplar fine roots, and the difference between rotations only explained 1.7% of variance. Poplar fine roots consisted of more carbon and less nitrogen with root orders, and the seasonal changes in contents of total carbon, total nitrogen and NSC showed significant difference between rotations, while.that of the C:N ratio didn' t show significant difference. Root order and season showed interaction effect on carbon and nitrogen dynamic. The C:N ratio was about 20:1 in lower order roots, and more than 30:1 in higher order roots. The C:N ratio in summer and autumn was significantly less than those in other seasons, while NSC content was the highest in November. This study indicated that the allocation of carbon and nitrogen in fine roots was closely correlated with fine root orders. Both NSC content and C:N ratio were of greatly important ecological significance in fine root turnover and growth regulation.

[Effects of exogenous phenolic acid on soil nutrient availability and enzyme activities in a poplar plantation].

By using ion exchange resin membrane as a plant root simulator, this paper studied the variations of soil nutrient availability and enzyme activities in a poplar plantation after applying phenolic acid. The exogenous phenolic acid had significant effects on the soil nutrient availability and enzyme activities, and the effects were concentration- and time dependent. With increasing phenolic acid concentration, the extraction mass of soil NH4+ -N and NO3- -N decreased significantly. At high concentration phenolic acid, soil PO4(3-) and Mn2+ availability increased significantly while soil K+ and Fe3+ availability was in adverse, and soil urease and phosphatase activities had a significant decrease while soil catalase and polyphenol oxidase activities increased significantly. With the elongation of incubation time, the availability of soil NH4+-N, PO4(3-), and Mn2+ increased gradually, while that of soil NO3- -N, K+, Fe3+, and Zn2+ decreased significantly. The correlation analysis showed that the availability of soil NO3- -N, K , Fe2+, and Mn2+ had close correlations with the activities of soil urease, polyphenol oxidase, and phosphatase.