Soil heterotrophic respiration in response to rising temperature and moisture along an altitudinal gradient in a subtropical forest ecosystem, Southwest China.

Globally, one-third of the terrestrial carbon (C) is stored in tropical soils. The warming predicted for this century is expected to increase microbial decomposition in soil and escalate climate change potential by releasing more carbon dioxide (CO2) into the atmosphere. Understanding the response of soils to warming is a key challenge in predicting future climate change trajectories. Here we examined the combined effect of soil temperature (Ts) and soil water content (VWC) on soil heterotrophic respiration (Rsh) and its temperature sensitivity across different altitudes (2400, 1900, and 1450 m ASL) in the Ailaoshan subtropical forest ecosystem, Southwest China. Along the elevation gradient, soil C stocks in the top 10 cm soil layer increased significantly from 10.7 g/ kg at 1480 m ASL to 283.1 g/ kg at 2480 m ASL. Soil cores from various elevations were translocated to the same, and lower elevations and Rsh from those cores were measured every month from February 2010 to January 2014. Temperature sensitivity (Q10) of Rsh for the period was highest at the highest (H) elevation (Q10 = 5.3), decreased significantly towards the middle (M, Q10 = 3.1) and low (L, Q10 = 1.2) elevation. Q10 at M and L elevation did not differ between the place of origin and translocated cores. For the cores within each elevation, Q10 did not vary across the years. Our models suggest that Rsh increased significantly in response to an increase in Ts at each elevation under an intermediate VWC. Hence, the rate of emission was higher in lower elevations due to a higher Ts range. Our findings highlight that the predicted warming over the 21st century will have the greatest impact of Ts on Rsh, especially on the soils at the highest elevations, and will lead towards positive feedback to the climate system.

Evaluation of forest structure, biomass and carbon sequestration in subtropical pristine forests of SW China.

Very old natural forests comprising the species of Fagaceae (Lithocarpus xylocarpus, Castanopsis wattii, Lithocarpus hancei) have been prevailing since years in the Ailaoshan Mountain Nature Reserve (AMNR) SW China. Within these forest trees, density is quite variable. We studied the forest structure, stand dynamics and carbon density at two different sites to know the main factors which drives carbon sequestration process in old forests by considering the following questions: How much is the carbon density in these forest trees of different DBH (diameter at breast height)? How much carbon potential possessed by dominant species of these forests? How vegetation carbon is distributed in these forests? Which species shows high carbon sequestration? What are the physiochemical properties of soil in these forests? Five-year (2005-2010) tree growth data from permanently established plots in the AMNR was analysed for species composition, density, stem diameter (DBH), height and carbon (C) density both in aboveground and belowground vegetation biomass. Our study indicated that among two comparative sites, overall 54 species of 16 different families were present. The stem density, height, C density and soil properties varied significantly with time among the sites showing uneven distribution across the forests. Among the dominant species, L. xylocarpus represents 30% of the total carbon on site 1 while C. wattii represents 50% of the total carbon on site 2. The average C density ranged from 176.35 to 243.97 t C ha-1. The study emphasized that there is generous degree to expand the carbon stocking in this AMNR through scientific management gearing towards conservation of old trees and planting of potentially high carbon sequestering species on good site quality areas.

Study on distribution of drug-resistant genotypes of multiple drug resistant bacteria insercond class and below hospitals of three big areas / 国际检验医学杂志

Objective To analyze the distribution of common drug-resistance genotypes of multi-drug resistant bacteria (MDRB) in second class and below hospitals in 3 big areas of Chongqing City for perfecting the bacterial drug resistance surveillance network in local area.Methods In 7206 detected strains of MDRB, the re-cultured pure colonies of top five bacteria in the bacterial strains numer were taken and performed the common drug resistant genotyping detection and comparative analysis by PCR technique and sequencing.Results Acinetobacter spp.was dominated by the genotypes carrying TEM,SUL and GyrA genes,Klebsiella pneumoniae was dominated by the genotypes carrying SHV,GyrA genes,Escherichia coli was dominated by the genotypes carrying TEM,CTX-M,SUL,GyrA,aac (3) Ⅱ genes,Pseudomonas aeruginosa was dominated by genotypes carrying SUL,GyrA genes,Staphylococcus was dominated by genotypes carrying GyrA,aac (6 ′)-aph ′′ genes;among the five strains of MDRB,the majority were the strains with multiple expression of two kinds or four kinds of common drug-resistance genes,in which the detection rate of Escherichia coli multiple expression was highest,reaching 92.74%,the detection rate of Staphylococcus multiple expression was lower.The detection rates of common drug resistant genotypes carried by MDRB had statistical difference among various areas and various years (P<0.05);in the comparison with the gene sequences of corresponding bacteria in NCBI Blastn database,the sequencing results of 7 common drug resistant genotypes carried by 5 kinds of MDRB were basically consistent.Conclusion The common drug-resistant genotypes carried by MDRB detected in the second class and below hospitals of Chongqing City and their distribution are basically consistent with the monitoring levels in the local tertiary hospitals and whole nation.Therefore the antibacterial surveillance of infection pathogenic bacteria should be strengthened in these hospitals,and medication should be rationally used so as to delay the development of pathogenic bacterial drug resistance in local area.