Examining CO2 and N2O pollution and reduction from forestry application of pure and mixture forest.

Greenhouse gases (GHGs) carbon dioxide (CO2) and nitrous oxide (N2O), contribute significantly to global warming, and they have increased substantially over the years. Reforestation is considered as an important forestry application for carbon sequestration and GHGs emission reduction, however, it remains unknown whether reforestation may instead produce too much CO2 and N2O contibuting to GHGs pollution. This study was performed to characterize and examine the CO2 and N2O emissions and their controlling factors in different species and types of pure and mixture forest used for reforestation. Five soil layers from pure forest Platycladus orientalis (PO), Robinia pseudoacacia (RP), and their mixed forest P-R in the Taihang mountains of central China were sampled and incubated aerobically for 11 days. The P-R soil showed lower CO2 and N2O production potentials than those of the PO soils (P < 0.01). The average reduction rate of cumulative CO2 and N2O was 31.63% and 14.07%, respectively. If the mixed planting pattern is implemented for reforestation, the annual CO2 reduction amounts of China's plantation can be achieved at 8.79 million tonnes. With the increase of soil depths, cumulative CO2 production in PO and RP soils decreased, whereas CO2 and N2O production in P-R soil did not show similar pattern. Soil particle size fraction was the main factor influencing GHGs emissions, and the clay fraction showed negative correlation with cumulative CO2 and N2O production. In summary, compared with PO pure artificial forests, the mixture plantation mode can not only reduce GHGs pollution but also improve soil fertility, which is conducive to sustainable management of artificial forests.

mRNA expression and DNA methylation in three key genes involved in caste differentiation in female honeybees (Apis mellifera).

In honeybee (Apis mellifera) colonies, queens and workers are alternative forms of the adult female honeybee that develop from genetically identical zygotes but that depend on differential nourishment. Queens and workers display distinct morphologies, anatomies and behavior, better known as caste differentiation. Despite some basic insights, the exact mechanism responsible for this phenomenon, especially at the molecular level, remains unclear although some progress has been achieved. In this study, we examined mRNA levels of the TOR (target of rapamycin) and Dnmt3 (DNA methyltransferase 3) genes, closely related to caste differentiation in honeybees. We also investigated mRNA expression of the S6K (similar to RPS6-p70-protein kinase) gene linked closely to organismal growth and development in queen and worker larvae (1-day and 3-day old). Last, we investigated the methylation status of these three genes in corresponding castes. We found no difference in mRNA expression for the three genes between 1st instar queen and worker larvae; however, 3rd instar queen larvae had a higher level of TOR mRNA than worker larvae. Methylation levels of all three genes were lower in queen larvae than worker larvae but the differences were not statistically significant. These findings provide basic data for broadening our understanding of caste differentiation in female honeybees.