[Characteristics of anion and cation in rhizosphere soil of saline grassland in North China under different nitrogen addition levels]. / ä¸åŒæ°´å¹³æ°®æ·»åŠ ä¸‹åŽåŒ—ç›æ¸åŒ–è‰åœ°æ ¹é™ åœŸå£¤é˜´é˜³ç¦»å­ç‰¹å¾.

We investigated the effects and mechanisms of nitrogen additions (0, 1, 2, 4, 8, 16, 24, 32 g N·m-2·a-1) on contents of anion and cation in rhizosphere soil, bulk soil, and mixed rhizosphere and bulk soil in the heavily salinized grassland in the agro-pastoral ecotone of North China. The results showed that pH of rhizosphere, mixed and bulk soils decreased significantly with the increases of nitrogen addition levels. Moreover, pH of three soil types under the 32 g N·m-2·a-1 treatment decreased by 1.2, 0.9, and 0.6, respectively, while pH of rhizosphere soil decreased by 0.44 compared with the bulk soil. Na+ content of rhizosphere, mixed and bulk soils significantly decreased, while the NO3- content significantly increased. The proportion of Na+ content in total soluble salt content in rhizosphere soil decreased by 14% and that in bulk soil decreased by 12% after the 32 g N·m-2·a-1 addition. NO3- content increased by 29% in rhizosphere soil and by 26% in bulk soil. There was significant negative correlation between pH and NO3- content, and significant positive correlation between pH and Na+ content. The total soluble salt content of rhizosphere soil under the 32 g N·m-2·a-1 treatment was significantly reduced by 31.5%. Collectedly, nitrogen deposition could reduce soil pH and total soluble salt content of rhizosphere soil and alleviate saline-alkali stress.

Effects of precipitation change and nitrogen addition on soil net N mineralization in a saline-alkaline grassland of Northern Shanxi Province, China.

To explore the responses of soil net nitrogen (N) mineralization rate to precipitation varia-tion and nitrogen deposition in salinized grassland, we set precipitation manipulation and nitrogen addition experiments in the typical agro-pastoral ecotone saline-alkaline grassland of Northern Shanxi Province, China. The in situ soil net N mineralization rate was determined by top-cover buried PVC cylinder from May to September in 2019. The results showed that there were seasonal dynamics in soil net N mineralization rate. Soil net N mineralization rate was not affected by increase/decrease precipitation (±50%), nitrogen addition (10 g·m-2·a-1) or the combination of nitrogen addition and increase 50% precipitation treatments. The combination of nitrogen addition and 50% reduction of precipitation significantly improved soil net nitrification rate and net N mine-ralization rate by 10.8 and 8.6 times, respectively. Soil net nitrogen mineralization rate was positively related to soil water content, and negatively related to soil pH. The effects of nitrogen addition on soil nitrogen mineralization rate were dependent on precipitation conditions. Soil water content and pH were important factors regulating soil net nitrogen mineralization rate in the saline-alkaline grassland of Northern Shanxi Province. Therefore, to roundly assess the response model of soil N mine-ralization process to global change, it is necessary to consider the interaction of precipitation changes and nitrogen addition, and the soil physical and chemical properties of salinized grassland.

[Short-term Effects of Different Grazing Intensities on Greenhouse Gas Fluxes in Semi-arid Grassland].

Grazing is one of the most important ways for managing grassland in northern China. Different studies have focused on the effects of grazing on the structure and function of ecosystems. Grazing affects the structure and function of soil via biological and physical processes, such as animal trampling, feeding, and excretion, which further affects N2O emissions. However, there is less research on greenhouse gases (GHGs) emissions by grazing intensities in semi-arid grassland ecosystems in northern China. In this study, four different grazing intensities were considered in the semi-arid grassland ecosystem of the typical agro-pastoral ecotone in northern China (Youyu, Shanxi). The influence of different grazing intensities on GHG fluxes was studied by measuring GHGs fluxes in the growing season with an opaque static chamber. The results showed that ① Grazing had no effect on CO2 and N2O fluxes during the first year of grazing treatment. ② However, grazing decreased soil water content (P<0.05), moderate grazing intensity decreased microbial biomass carbon (P<0.05), and moderate and heavy grazing intensities reduced microbial biomass nitrogen (P<0.05). ③ Significant positive correlations between CO2 flux and soil temperature and soil moisture were observed. The correlation between temperature and CO2 emissions was increased by grazing. ④ There was a significant positive correlation between soil temperature, soluble nitrogen, soil microbial biomass nitrogen, CO2 flux, and N2O flux. Our results indicated that GHG, regulated by soil microorganisms, was affected by soil temperature and moisture.

[Cardiac and renal arteriolar pathological changes in the autopsied elderly hypertensive patients with left ventricular hypertrophy.].

OBJECTIVE: To determine the cardiac and renal arteriolar pathological changes in autopsied elderly hypertensive patients with left ventricular hypertrophy (LVH). METHODS: Autopsy samples from 25 essential hypertension (EH) patients with LVH aged over 60 years and age-matched 8 controls were analyzed. LVH was further divided into three degrees from I to III according to left ventricular free wall thickness in EH patients. Quantitative measurements of arteriolar morphometric parameters in heart and kidney were performed under light microscope with computer image analysis post HE and Masson staining. The lesion index and plasma albumen infiltration of arteriole were evaluated by the semiquantitative method. RESULTS: The inner diameter (ID) and luminal cross-sectional area (LCSA) were significantly decreased while wall thickness (WT), wall cross-sectional area (WCSA), ratio of WCSA to LCSA (WCSA/LCSA) and ratio of WT to ID (WT/ID) were significantly increased in EH patients in proportion to LVH degree. Both cardiac and renal arterioles WCSA/LCSA and WT/ID were significantly decreased with increasing outer diameters (OD). Under the same OD rang, the pathological changes were more significant in the renal arterioles compared to those in the cardiac arterioles (P < 0.05). The arteriolar lesion index and the plasma albumen infiltration index of cardiac and renal arterioles in EH group were significantly higher than those in the control group (P < 0.01) and the arteriolar lesion index and the plasma albumen infiltration of arteriole in the renal tissue were significantly higher than those in the cardiac tissue (P < 0.01). CONCLUSION: Concentric remodeling occurs in the cardiac and renal arterioles of EH patients in proportion to LVH degree and renal arterioles lesions were significantly severer than that of cardiac arterioles in EH patients with LVH.