Effects of short-term N addition on soil C fluxes in alpine Sibiraea angustata scrub on the eastern margin of the Qinghai-Tibetan Plateau

Although knowledge of the impact of N enrichment on soil C fluxes is scant, such information is highly critical for estimating the global C budget under elevated N deposition. To quantify the effects of short-term N addition on soil C sequestration in an alpine scrub ecosystem, we conducted a field experiment for Sibiraea angustata scrub on the eastern margin of the Qinghai-Tibetan Plateau in China. We quantified the soil C pool (030 cm) and C fluxes in litterfall, fine root ( 0.05) or reducing R-h (P > 0.05). As a result, the soil C pool (030 cm) increased significantly. In conclusion, these results suggest that fine roots play a dominant role in the C balance of an alpine scrub ecosystem due to large C-inputs to the soil. Moreover, short-term high N enrichment causes sequestration of additional atmospheric CO2, largely because of the stimulation of fine root growth rather than increased inputs of aboveground plant litterfall or reductions in soil CO2 emission

Seasonal variations in the soil amino acid pool and flux following the conversion of a natural forest to a pine plantation on the eastern Tibetan Plateau,China

Although the importance of amino acids to plant nitrogen (N) nutrition in most terrestrial ecosystems is being increasingly recognized, the availability and seasonal variations of soil amino acids in subalpine coniferous forests are poorly understood. Few studies have investigated the differences in the soil amino acid pool and the cycling between forest types caused by land-use changes. In this study, we quantified the concentrations and fluxes of soil amino acids in a dragon spruce plantation and an adjacent natural forest (NF) on the eastern Tibetan Plateau, China. Soil samples from organic and mineral soil horizons were collected in May, July, September, and December of 2015 and March of 2016. The pools and fluxes of soil amino acids in the plantation converted from NF decreased significantly during the growing season and increased during the non-growing season. Meanwhile, greater pools and fluxes of soil amino acids were observed in the organic horizon than in the mineral soil horizon in both forest types. Our results indicate that distinct nutrient economies were likely formed in the plantation compared with the NF because the quality of the input litter decreased in the plantation. In addition, the importance of soil amino acids in the subalpine coniferous forest ecosystem was evaluated based on published literature. The ratios of amino acids to dissolved inorganic N (DIN) in the soils from the two studied forests were generally much lower than the range of ratios reported for other ecosystems. However, the relative high amino acid: DIN ratio in the plantations during the non-growing season suggests that the plants in the plantation may have the potential to modify their strategies for acquiring N due to the changed relative dominance between the DIN and amino acids in the soils. (C) 2016 Elsevier Ltd. All rights reserved

Association between population density and infection rate suggests the importance of social distancing and travel restriction in reducing the COVID-19 pandemic

International audienceCurrently, 2019-nCoV has spread to most countries of the world. Understanding the environmental factors that affect the spreadof the disease COVID-19 infection is critical to stop the spread of the disease. The purpose of this study is to investigate whetherpopulation density is associated with the infection rate of the COVID-19. We collected data from official webpages of cities inChina and in the USA. The data were organized on Excel spreadsheets for statistical analyses. We calculated the morbidity andpopulation density of cities and regions in these two countries. We then examined the relationship between morbidity and otherfactors. Our analysis indicated that the population density in cities in Hubei province where the COVID-19 was severe wasassociated with a higher percentage of morbidity, with an r value of 0.62. Similarly, in the USA, the density of 51 states andterritories is also associated with morbidity from COVID-19 with an r value of 0.55. In contrast, as a control group, there is noassociation between the morbidity and population density in 33 other regions of China, where the COVID-19 epidemic is wellunder control. Interestingly, our study also indicated that these associations were not influenced by the first case of COVID-19.The rate of morbidity and the number of days from the first case in the USA have no association, with an r value of − 0.1288.Population density is positively associated with the percentage of patients with COVID-19 infection in the population. Our datasupport the importance of such as social distancing and travel restriction in the prevention of COVID-19 spread