No abstract

Microorganisms play a substantial role in the aquatic nitrogen cycle. However, the community structures and metabolic potential of microbiota inhabiting subtropical aquaculture ponds are still poorly understood. In the present study, we investigated the community structure of pond microbiota by amplicons sequencing using the MiSeq sequencing platform and predicted their potential metabolic characteristics. A total of 614 dominant operational taxonomic units (OTUs) were detected from 27 samples, of which 61 were dominant in more than half of the samples. Many of the taxa observed in this study have known roles in nitrification and denitrification. In addition, most genes related to nitrogen metabolism were detected using a predictive metagenome approach, and a complementary pattern in which ponds had different genes in the same metabolic pathway emerged. These results provide basic information for the management of microbiota to control the nitrogen balance in pond water.

The Qinghai-Tibetan Plateau (QTP) is the most expansive area of alpine grasslands worldwide, which have been grazed for thousands of years. Distinct environmental conditions render QTP grasslands vulnerable to disturbances. Intensified grazing in the area has led to its degradation in recent decades. However, the effects of grazing on grassland production, soil carbon, and nitrogen contents, their relationships and the factors influencing the grasslands of QTP have yet to be determined. In this study, we evaluated the effect of grazing by using a hierarchical meta-analysis, and explored relation of response variables by structural equation modeling. In all, grazing significantly decreased the aboveground biomass (−38%), total biomass (TB) (−14%), litter (−63%), soil organic carbon (SOC) (−20%), and total nitrogen (TN) (−15%). The root shoot ratio was increased (75%). Grazing intensity exerted significant effects, and mean annual temperature and altitude influenced the responses to a certain degree. Specifically, the response of the root shoot ratio, which can affect the responses of SOC and TN, was significantly higher in the QTP grasslands. Our findings elucidated the response patterns, specialties, relationships, and factors influencing the QTP grasslands, which need to be considered in the development of processbased models and the sustainable use of alpine grasslands on QTP in the future.