[Effects of harvest residue management on soil organic nitrogen fractions in young Cunninghamia lanceolata plantation]. / 采伐剩余物不同处理方式对杉木幼林土壤有机氮组分的影响.

Different treatments of harvest residues will change the quantity and quality of soil organic matter, with direct or indirect effects on the composition and content of soil nutrient. Nitrogen is one of the most important soil nutrients. However, the response of soil organic nitrogen fractions to different harvest residue treatments is still unclear. In this study, harvest residue treatments, including harvest residue removed, residue retained and residue burnt, were set up after clear-cutting a 50-year-old mature Cunninghamia lanceolata forest in Sanming City, Fujian, China. The H2SO4 hydrolysis method was used to determine soil organic nitrogen fractions and their driving factors in the 0-10 cm and 10-20 cm soil layers after 5 years of harvest residue treatments. The results showed that residue retained treatment significantly enhanced the contents of soil organic nitrogen and its liable fractions. In the 0-10 cm soil layer, soil organic nitrogen content under residue retained treatment (3.36 g·kg-1) was 1.5 and 1.3 times as those of residue removed and residue burnt treatments, respectively. Residue retained treatment had the highest contents of labile nitrogen Ⅰ and Ⅱ fractions. In 10-20 cm soil layer, the contents of soil organic nitrogen and labile nitrogen Ⅱ fraction were also significantly higher in residue retained treatment (2.20, 0.73 g·kg-1) than that in residue removed and residue burnt treatments. The labile nitrogen index Ⅱ in residue retained treatment (33.9%) was significantly higher than in residue burnt treatment (26.1%). The contents of total carbon, dissolved organic carbon, dissolved organic nitrogen, microbial biomass under residue retained treatment were the highest in both soil layers. Compared with residue removed treatment, residue retained treatment significantly enhanced the abundance of soil bacteria (Gram-positive bacteria and Gram-negative bacteria) in 0-10 cm soil layer. In 10-20 cm soil layer, residue retained treatment had the highest content of fungi and the lowest content of actinomycetes. Pearson analysis showed that there were significant positive correlations of labile fractions of soil organic nitrogen with total carbon, dissolved organic carbon, dissolved organic nitrogen, microbial biomass carbon, microbial biomass nitrogen, bacteria (Gram-positive bacteria, Gram-negative bacteria), and fungi, and negative correlations with actinomycetes. It was concluded that the retention of harvest residue was beneficial to increase the content of soil organic nitrogen and labile fractions, improve soil biochemical properties and had a positive effect on soil microbial community composition. Retention of harvest residue was an effective management measure to maintain soil fertility and improve forest productivity.

[Effects of harvest residue treatments on soil phosphorus fractions and availability in a young Chinese fir plantation]. / é‡‡ä¼å‰©ä½™ç‰©çš„å¤„ç†æ–¹å¼å¯¹æ‰æœ¨å¹¼æž—åœŸå£¤ç£·ç»„åˆ†åŠå ¶æœ‰æ•ˆæ€§çš„å½±å“.

Forest harvesting changes the quantity and quality of organic matter inputs into soil, and thus would alter soil nutrient content and availability. Phosphorus (P) is a key element affecting plant growth. The effects of harvest residue treatments on soil P fractions and availability had not yet been evaluated. In this study, harvest residue retainment (RR), residue removal (R) and residue burning (RB) treatments were manipulated after clear-cutting in a mature Chinese fir (Cunninghamia lanceolata) plantation at the Sanming Forest Ecosystem and Global Change Research Station in Fujian, China. This study focused on the dynamics of soil P fractions and their driving factors in the 0-10 cm and 10-20 cm soil layers after 4-year residue treatments. The results showed that, in RR treatment, the contents of easily-available P, moderately-available P and non-available P at the 0-10 cm soil layer were all significantly higher than those in R treatment, while the contents of moderately-available P and non-available P at the 10-20 cm soil layer was significantly higher than those in RB treatments. The ratios of soil organic carbon (C) to organic P (C:Po) in both layers were over 200 for all the three treatments, with ratios in RR treatment being significantly lower than those in RB and R treatments, indicating that RR could alleviate P limitation in this ecosystem. Moreover, results of the redundancy analysis showed that changes in P fractions were mainly affected by dissolved organic C, free Fe and noncrystalline amorphous Fe. The results suggested that soil organic P and available P were mainly from the decomposition of plant residues, which supported continuous P supply for plant growth. RR could enhance soil P content, thereby improve soil P availability and mitigate P limitation in Chinese fir plantation.

[Effects of warming and precipitation exclusion on soil N2O fluxes in subtropical forests.] / 增温和隔离降雨对亚热带森林土壤N2O通量的影响.

In order to explore how soil warming and precipitation exclusion influence soil N2O fluxes, we used related functional genes as markers, and four treatments were set up, i.e. , control (CT), soil warming (W, 5 ℃ above the ambient temperature of the control), 50% precipitation reduction (P), soil warming plus 50% precipitation reduction (WP). The results showed that precipitation exclusion reduced soil ammonium nitrogen concentration significantly. Soil warming decreased soil N2O flux and soil denitrification potential significantly. Soil microbial biomass nitrogen (MBN) in warming treatment (W) and precipitation exclusion treatment (P) was significantly lower than that in the control. The amoA gene abundance of AOA was negatively correlated with MBN and ammonium nitrogen contents, but neither soil nitrification potential nor soil N2O flux was correlated with the amoA gene abundance of AOA. Path analysis showed that the denitrification potential affected soil N2O flux directly, while microbial biomass phosphorus (MBP) and warming affected soil N2O flux indirectly through their direct effects on denitrification potential. Temperature might be the main driver of N2O flux in subtropical forest soils. Global warming would reduce N2O emissions from subtropical forest soils.

Vitamin D Deficiency Increases the Risk of Gestational Diabetes Mellitus: A Meta-Analysis of Observational Studies.

The results investigating the relationship between vitamin D levels and gestational diabetes mellitus (GDM) are inconsistent. Thus, we focused on evaluating the association of vitamin D deficiency with GDM by conducting a meta-analysis of observed studies. A systematic literature search was conducted via PubMed, MEDLINE, and Cochrane library to identify eligible studies before August 2015. The meta-analysis of 20 studies including 9209 participants showed that women with vitamin D deficiency experienced a significantly increased risk for developing GDM (odds ratio (OR) = 1.53; 95% confidence intervals (CI), 1.33, 1.75) with a little heterogeneity (I² = 16.20%, p = 0.252). A noteworthy decrease of 4.93 nmol/L (95% CI, -6.73, -3.14) in serum 25(OH)D was demonstrated in the participants with GDM, and moderate heterogeneity was observed (I² = 61.40%, p = 0.001). Subgroup analysis with study design showed that there were obvious heterogeneities in nested case-control studies (I² > 52.5%, p < 0.07). Sensitivity analysis showed that exclusion of any single study did not materially alter the overall combined effect. In summary, the evidence from this meta-analysis indicates a consistent association between vitamin D deficiency and an increased risk of GDM. However, well-designed randomized controlled trials are needed to elicit the clear effect of vitamin D supplementation on prevention of GDM.

[Decomposition dynamics of leaf litter in logging residue of a secondary Castanopsis carlesii plantation and its chemical composition changes].

A field experiment was conducted to understand the decomposition rates and chemical composition changes of leaf litter in logging residues of a 35-year-old secondary Castanopsis carlesii plantation over a period of one year. Mass loss rate of leaf litter showed an exponential decrease with time from May 2012 to April 2013, with a total 80% loss of initial dry mass. Net potassium (K) release was observed during this period, with only 5% of initial K remained. Nitrogen ( N) featured a pattern of accumulation at the early stage and release later, while phosphorus (P) exhibited a sequence of release, accumulation, and release. The remaining of N and P were 19% and 16% of their initial mass, respectively. The release rate was highest for K and the lowest for N. Decomposition of lignin indicated a trend of release-accumulation-release from May 2012 to October 2012, with no further significant change from November 2012 to the end of the experiment. The concentration of cellulose nearly unchanged during the experiment. The N/P rate increased with decomposition, ranging from 18.6 to 21.1. The lignin/N rate fluctuated greatly at the early stage and then almost stabilized thereafter.

[Root decomposition characteristics of Castanopsis carlesii stand in Wanmulin Natural Reserve of Fujian Province].

By using litter-bag method, the root decomposition characteristics of Castanopsis carlesii stand in Jian'ou Wanmulin Natural Reserve of Fujian Province were studied over two years. Three classes of roots, i.e., 0-1 mm, 1-2 mm, and 2-4 mm in diameter, were tested. During the 2-year period of decomposition, all classes roots showed a bi-phase pattern, being decomposed faster in prophase and slower in anaphase. The leaching loss of extractable substances in roots made root decomposition faster in prophase, while the increase of the acid-insoluble substances concentration in roots restrained the decomposition in anaphase. In the first year, the decomposition rate of all classes roots was controlled by the initial concentrations of their extractive substances and N; while in the second year, the decomposition rate was controlled by the initial C/N and the initial concentrations of acid-insoluble substances, N and P of the roots. During decomposition, all classes roots showed an increasing N concentration and a decreasing P concentration, and the N showed an enrichment-release pattern, while the P showed a direct release pattern.

[Humoral immune response and in vitro neutralizing antibody assay on co-delivery of protein HPV16L1 virus-like particle with HPV16L1 gene].

OBJECTIVE: To compare humoral immune response by co-inoculating mice with antigen HPV16L1 virus-like particle (VLP) and HPV16L1 recombinant plasmids and then observing the neutralizing antibody activity in vitro. METHODS: C57BL/6 mice were injected intramuscularly/subcutaneously with pcDNA-L1 plasmids plus HPV16L1 VLP. Serum IgG levels were detected by ELISA, antibody neutralizing protective activities were determined by hemagglutination inhibition and HPV16L1 VLP binding inhibition assay. RESULTS: Serum antibody titers and neutralizing antibody activities were increased in HPV16L1 plasmids plus HPV16L1 VLP proteins in co-immunized mice when compared with controls. CONCLUSION: Co-inoculation of the HPV16L1 VLP protein can enhance production of neutralizing antibody activities against aimed antigen, which should be a more promising strategy for effective HPV16 prophylactic vaccine development.