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In 2007-2010,a comparative study was conducted on the phosphorus characteristics in the rhizosphere soil of Cunninghamia lanceolata, Pinus massoniana and C. lanceolata-P. massoniana mixed plantations in a forest farm in Nanping City of Fujian Province, East China. In the rhizosphere soil of pure C. lanceolata and P. massoniana plantations, the content of available P was higher than that in non-rhizosphere soil. As compared with non-rhizosphere soil, the rhizophere soil in the three plantations had lower pH and O-P content but higher Al-P and Fe-P contents, and its P adsorption capacity was lower while the P desorption rate and desorbed P were in adverse. In the rhizophere soil of pure P. massoniana plantation, the contents of available P, Fe-P, and Al-P, their desorption rates, and desorption capacity were higher, but the O-P content and the adsorbed P were lower, as compared with those in the rhizophere soil of pure C. lanceolata plantation. In the mixed plantation, the P activation in rhizophere soil was further improved, being more obvious under C. lanceolata, which suggested that mixed plantation of C. lanceolata and P. massoniana could promote the phosphorus nutrition of C. lanceolata. [ABSTRACT FROM AUTHOR]

The activity and stoichiometry of soil extracellular enzyme can provide a good indication for changes in soil nutrient availability and microbial demands for nutrients. However, it remains unclear how would nitrogen (N) deposition affect nutrient limitation of microbes in subtropical forest soils. We conducted a 5 years N addition experiment in a subtropical Phyllostachys pubescens forest. The soil nutrients and enzyme activities associated with carbon (C), N, and phosphorus (P) cycles were measured. We also examined the nutrient distribution of microorganisms using enzyme stoichiometry and vector analysis. The results showed that N addition significantly decreased the contents of soil soluble organic C and available P and increased that of available N. Furthermore, N addition significantly decreased β-N-acetyl-glucosaminidase (NAG) activity and NAG/ microbial biomass carbon (MBC), and increased acid phosphatase (ACP) and ACP/MBC. The low and moderate N addition levels significantly increased enzyme C/P, vector length, and vector angle, but significantly decreased enzyme N/P. Results of redundancy analysis showed that the change in soil enzyme activity and enzymatic stoichiometry were mainly driven by soil available P content under N addition. In summary, N addition altered the microbial nutrient acquisition strategy, which increased nutrient allocation to P-acquiring enzyme production but reduced that to N-acquiring enzyme production. Moreover, N addition exacerbated the C and P limitation of soil microorganisms. Appropriate amount of P fertilizer could be applied to improve soil fertility of subtropical P. pubescens forest in the future.

Phosphorus (P) is an important nutrient for plant and microbial growth. Soil P availabi-lity is poor in subtropical areas. Long-term heavy nitrogen (N) deposition might further reduce P availability. The experiment was performed in a Phyllostachys pubescens forest in Daiyun Mountain. The effects of N application on soil basic physical and chemical properties, soil P fractions, microbial biomass, and acid phosphomonoesterase activity were analyzed after three years of N application. The results showed that N application significantly increased NO 3 - -N content and thus soil N availability, while it significantly reduced the percentage of decomposable organic P to total P, with the ratio of carbon (C) to organic P being over 200. The soil microbial biomass C, microbial biomass P, acid phosphomonoesterase, and the ratio of microbial biomass N to microbial biomass P and microbial biomass C to microbial biomass P were increased as the N application rate increased. There was a significant negative correlation between the percentage of decomposable organic P to total P and microbial biomass P. Consequently, N application enhanced soil P limitation and increased microbial P demand.

The subtropical zone in China is one of the regions most affected by nitrogen deposition. Soil dissolved organic matter (DOM) is considered to be an important indicator of soil organic matter. Nitrogen deposition may alter the quality and quantity of soil DOM by changing soil microbial activity. In this study, we explored the effects of nitrogen addition on soil DOM content, its spectral characteristics and microbial extraceller enzyme activity in the Moso bamboo plantations by setting control (CT), low-nitrogen (LN), and high-nitrogen (HN) addition levels for three-year nitrogen addition. The results showed that there was no significant change in soil pH, dissolved organic carbon, dissolved organic nitrogen, and aroma index following nitrogen addition, while the humification index increased significantly, microbial enzyme activities increased first and then decreased with the increases of nitrogen addition. Fourier transform infrared spectroscopy results showed that soil DOM had similar absorption peaks in seven regions, and that the absorption peaks of 1000 to 1260 cm -1 were the strongest, indicating an enhanced amount of polysaccharides, alcohols, carboxyl acids, and esters after nitrogen addition. The results of three-dimensional fluorescence spectroscopy showed that soil DOM structure significantly changed following nitrogen addition, with a decrease in low-molecular substances such as protein-like substances and microbial metabolites and a significant increase in high-molecular substances such as humus-like substances. In general, nitrogen addition made soil nitrogen compatible with microbial requirements. Microorganisms decompose substances that were easily degraded in DOM. The structure of soil DOM was more complex after nitrogen addition. Therefore, short-term nitrogen deposition might be conducive to preserving soil fertility.

Soil P fraction, microbial biomass P (MBP), and activities of acid phosphomonoesterase (ACP) and phosphodiesterase (PD) were analyzed under evergreen broad-leaved forest, mixed forest and coniferous forest in Daiyun Mountains. The results showed that labile-P comprised only 1.0%-4.5% of soil total phosphorus (TP). The ratio of soil carbon to organic phosphorus (C:Po) was >200, indicating phosphorus limitation across the three vegetation types. Organic phosphorus (Po) was a significant fraction of soil P, which accounted for 44.8%-47.1% and 28.6%-30.6% of TP in A and B horizons, respectively. Results from the redundancy analysis showed that the changes in P fractions were mainly driven by PD in the A horizon and by ACP in the B horizon. Moreover, the activities of PD and ACP had a significant negative correlation with Po. The results suggested that phosphorus deficiency occurred in the three vegetation types, and that PD and ACP could play major roles in the depletion of soil Po in response to phosphorus limitation in subtropical forests.

Esophageal cancer (EC) is one of the most common cancers in China. The purpose of this study was to investigate the updated incidence rates and risk factors of EC in Nan'ao Island, where the EC incidence rate was chronically the highest in southern China. To calculate the annual incidence rate, data on 338 EC cases from Nan'ao Cancer Registry system diagnosed during 2005-2011 were collected. A case-control study was conducted to explore the EC risk factors. One hundred twenty-five alive EC patients diagnosed during 2005-2011 and 250 controls were enrolled into the case-control study. A pre-test questionnaire on demography, dietary factors, drinking water treatment, and behavioral factors was applied to collect information of all participants. The average EC incidence rates during 2005-2011 were 66.09/105, 94.62/105, 36.83/105 for both genders, males and females, respectively, in Nan'ao Island. The EC incidence rate in males was 2.40- to 4.55-fold higher than that in females in the period from 2006 to 2011 (P < 0.05). Considering the onset age, males tend to be much younger than females and reached peak incidence rate at a younger age (P < 0.05). Drinking water treatment by filter (odds ratio [OR] = 0.28, 95% confidence interval [95% CI] = 0.13-0.58) and fruit consumption (OR = 0.55, 95% CI = 0.32-0.94) reduced the risk for EC. On the contrary, the pickled vegetables consumption (OR = 2.64, 95% CI = 1.46-4.76) and liquor drinking (OR = 2.32, 95% CI = 1.21-4.44) increased the risk for EC. These results may be of importance for future research on EC etiology and prevention strategies., (© 2016 International Society for Diseases of the Esophagus.)

In 2007-2010, a comparative study was conducted on the phosphorus characteristics in the rhizosphere soil of Cunninghamia lanceolata, Pinus massoniana and C. lanceolata-P. massoniana mixed plantations in a forest farm in Nanping City of Fujian Province, East China. In the rhizosphere soil of pure C. lanceolata and P. massoniana plantations, the content of available P was higher than that in non-rhizosphere soil. As compared with non-rhizosphere soil, the rhizophere soil in the three plantations had lower pH and O-P content but higher Al-P and Fe-P contents, and its P adsorption capacity was lower while the P desorption rate and desorbed P were in adverse. In the rhizophere soil of pure P. massoniana plantation, the contents of available P, Fe-P, and Al-P, their desorption rates, and desorption capacity were higher, but the O-P content and the adsorbed P were lower, as compared with those in the rhizophere soil of pure C. lanceolata plantation. In the mixed plantation, the P activation in rhizophere soil was further improved, being more obvious under C. lanceolata, which suggested that mixed plantation of C. lanceolata and P. massoniana could promote the phosphorus nutrition of C. lanceolata.