Lie Xiao

Soil Microbial Community Composition During Natural Recovery in the Loess Plateau, China

This study aimed to determine the characteristics of soil microbial community composition and its relationship with soil chemical properties during natural recovery in the Loess Plateau. The soil microbial community composition was analyzed by comparing the soil microbial phospholipid fatty acids (PLFAs) of eight croplands abandoned for 1, 3, 5, 10, 13, 15, 20, and 30 yr in the Dunshan watershed, northern Loess Plateau, China. The results showed that soil organic carbon, total nitrogen, soil microbial biomass carbon, and soil microbial biomass nitrogen significantly increased with the abandonment duration, whereas the metabolic quotient significantly decreased. The Shannon richness and Shannon evenness of PLFAs significantly increased after 10 yr of abandonment. Gram-negative, Gram-positive, bacterial, fungal, and total PLFAs linearly increased with increased abandonment duration. Redundancy analysis showed that the abandonment duration was the most important environmental factor in determining the PLFA microbial community composition. The soil microbial PLFAs changed from anteiso- to iso-, unsaturated to saturated, and short- to long-chain during natural recovery. Therefore, in the Loess Plateau, cropland abandonment for natural recovery resulted in the increase of the soil microbial PLFA biomass and microbial PLFA species and changed the microbial from chemolithotrophic to a more heterotrophic community.

Effect of Different Vegetation Types on the Rhizosphere Soil Microbial Community Structure in the Loess Plateau of China

Abstract The Loess Plateau in China is one of the most eroded areas in the world. Accordingly, vegetation restoration has been implemented in this area over the past two decades to remedy the soil degradation problem. Understanding the microbial community structure is essential for the sustainability of ecosystems and for the reclamation of degraded arable land. This study aimed to determine the effect of different vegetation types on microbial processes and community structure in rhizosphere soils in the Loess Plateau. The six vegetation types were as follows: two natural grassland (Artemisia capillaries and Heteropappus altaicus), two artificial grassland (Astragalus adsurgens and Panicum virgatum), and two artificial shrubland (Caragana korshinskii and Hippophae rhamnoides) species. The microbial community structure and functional diversity were examined by analyzing the phospholipid fatty acids (PLFAs) and community-level physiological profiles. The results showed that rhizosphere soil sampled from the H. altaicus and A. capillaries plots had the highest values of microbial biomass C, average well color development of carbon resources, Gram-negative (G−) bacterial PLFA, bacterial PLFA, total PLFA, Shannon richness, and Shannon evenness, as well as the lowest metabolic quotient. Soil sampled from the H. rhamnoides plots had the highest metabolic quotient and Gram-positive (G+) bacterial PLFA, and soil sampled from the A. adsurgens and A. capillaries plots had the highest fungal PLFA and fungal:bacterial PLFA ratio. Correlation analysis indicated a significant positive relationship among the microbial biomass C, G− bacterial PLFA, bacterial PLFA, and total PLFA. In conclusion, plant species under arid climatic conditions significantly affected the microbial community structure in rhizosphere soil. Among the studied plants, natural grassland species generated the most favorable microbial conditions.

Fractal features of soil profiles under different land use patterns on the Loess Plateau, China

Fractal theory is becoming an increasingly useful tool to describe soil structure dynamics for a better understanding of the performance of soil systems. Changes in land use patterns significantly affect soil physical, chemical and biological properties. However, limited information is available on the fractal characteristics of deep soil layers under different land use patterns. In this study, the fractal dimensions of particle size distribution (PSD) and micro-aggregates in the 0–500 cm soil profile and soil anti-erodibility in the 0–10 cm soil profile for 10 typical land use patterns were investigated in the Zhifanggou Watershed on the Loess Plateau, China. The 10 typical land use patterns were: slope cropland, two terraced croplands, check-dam cropland, woodland, two shrublands, orchard, artificial and natural grasslands. The results showed that the fractal dimensions of PSD and micro-aggregates were all significantly influenced by soil depths, land use patterns and their interaction. The plantations of shrubland, woodland and natural grassland increased the amount of larger micro-aggregates, and decreased the fractal dimensions of micro-aggregates in the 0–40 cm soil profile. And they also improved the aggregate state and aggregate degree and decreased dispersion rate in the 0–10 cm soil profile. The results indicated that fractal theory can be used to characterize soil structure under different land use patterns and fractal dimensions of micro-aggregates were more effective in this regard. The natural grassland may be the best choice for improving soil structure in the study area.

Soil Moisture Variability Under Different Land Uses in the Zhifanggou Catchment of the Loess Plateau, China

Soil moisture is an important variable that determines crop growth and vegetation restoration. In the Loess Plateau, China, soil moisture dynamics are dramatically affected by land use patterns. This study investigated seven-year soil moisture dynamics and vertical distribution under seven land use patterns. The soil moisture levels in the 0 to 300cm depth in two croplands, and those in 0 to 600cm depth in two shrublands, a forestland, a grassland, and an abandoned cropland for natural recovery were measured in late April and late October of 2004 to 2010. The soil moisture storage in the 0 to 300cm depth in the Zea mayscropland dramatically exceeded that in the other six land use patterns. The Caragana korshinskii shrubland and Robinia pseudoacaciaforestland exhibited the lowest soil moisture storage in the entire 0 to 600cm depth. The soil moisture storage in the Hippophae rhamnoides, Caragana korshinskii, Robinia pseudoacacia, and Medicago sativalands showed a decreasing tendency, whereas that in the abandoned cropland was almost stable. Rainfall recharged the entire 300cm soil profile in the two croplands. The maximum soil infiltration levels in the Hippophae rhamnoides, Caragana korshinskii, and Robinia pseudoacacialands were 200, 200, and 240cm. The results indicate that planted shrubs and forests deplete soil moisture in the deep soil profile. The construction of terraces and dams can improve precipitation utilization rate, and restoring native grasslands after abandonment may be the best option for vegetation rehabilitation in the Loess Plateau.

Effects of vegetational type and soil depth on soil microbial communities on the Loess Plateau of China

ABSTRACT Soil microbial communities are very sensitive to changes in land use and are often used as indicators of soil fertility. We evaluated the microbial communities in the soils of four types of vegetation (cropland (CP), natural grassland (NG), broadleaf forest (BF) and coniferous forest (CF)) at depths of 0–10 and 10–20 cm on the Loess Plateau in China using phospholipid fatty acid (PLFA) profiling and denaturing gradient gel electrophoresis (DGGE) of DNA amplicons from polymerase chain reactions. The soil microbial communities were affected more by vegetation type than by soil depth. Total organic carbon, total nitrogen, soil-water content, pH, bulk density (BD) and C:N ratio were all significantly associated with the composition of the communities. Total PLFA, bacterial PLFA and fungal PLFA were significantly higher in the BF than the CP. The DGGE analyses showed that NG had the most diverse bacterial and fungal communities. These results confirmed the significant effect of vegetation type on soil microbial communities. BFs and natural grass were better than the CFs for the restoration of vegetation on the Loess Plateau.

Conophylline Promotes the Proliferation of Immortalized Mesenchymal Stem Cells Derived from Fetal Porcine Pancreas (iPMSCs)

Conophylline, is a bis (indole) alkaloid consisting of two pentacyclic aspidosperma skeletons, isolated from Tabernaemontana divaricata, which has been found to induce b-cell differentiation in rat pancreatic acinar carcinoma cells and in cultured rat pancreatic tissue. However, the precise role of conophylline in the growth and survival of immortalized pancreatic mesenchymal stem cells (iPMSCs) derived from fetal porcine pancreas were not understood at present. To determine whether this molecule is involved in controlling the proliferation of iPMSCs, we examined the effects of conophylline on iPMSCs. We found that conophylline can robustly stimulate iPMSCs proliferation, even promote their potential differentiation into islet-like clusters analyzed by cell counting, morphology, RT-PCR and real-time PCR, Western blotting, glucose-stimulated insulin release and insulin content analysis. The effects of conophylline were inhibited by LY294002, which is the inhibitor of the PI3K pathway. These results suggest that conophylline plays a key role in the regulation of cell mass proliferation, maintenance of the undifferentiated state of iPMSCs and also promotes iPMSCs differentiated into insulin-producing cells.

Elevated CO 2 and nitrogen addition have minimal influence on the rhizospheric effects of Bothriochloa ischaemum

The influence of elevated CO2 and nitrogen (N) addition on soil microbial communities and the rhizospheric effects of Bothriochloa ischaemum were investigated. A pot-cultivation experiment was conducted in climate-controlled chambers under two levels of CO2 (400 and 800 μmol mol−1) and three levels of N addition (0, 2.5, and 5 g N m−2 y−1). Soil samples (rhizospheric and bulk soil) were collected for the assessment of soil organic carbon (SOC), total N (TN), total phosphorus (TP), basal respiration (BR), and phospholipid fatty acids (PLFAs) 106 days after treatments were conducted. Elevated CO2 significantly increased total and fungal PLFAs in the rhizosphere when combined with N addition, and N addition significantly increased BR in the rhizosphere and total, bacterial, fungal, Gram-positive (G+), and Gram-negative (G−) PLFAs in both rhizospheric and bulk soil. BR and total, bacterial, G+, and G+/G− PLFAs were significantly higher in rhizospheric than bulk soil, but neither elevated CO2 nor N addition affected the positive rhizospheric effects on bacterial, G+, or G+/G− PLFAs. N addition had a greater effect on soil microbial communities than elevated CO2, and elevated CO2 and N addition had minor contributions to the changes in the magnitude of the rhizospheric effects in B. ischaemum.