Effect of Short-Term Low-Nitrogen Addition on Carbon, Nitrogen and Phosphorus of Vegetation-Soil in Alpine Meadow

As one of the nitrogen (N) limitation ecosystems, alpine meadows have significant effects on their structure and function. However, research on the response and linkage of vegetation-soil to short-term low-level N deposition with rhizosphere processes is scant. We conducted a four level N addition (0, 20, 40, and 80 kg N ha−1 y−1) field experiment in an alpine meadow on the Qinghai-Tibetan Plateau (QTP) from July 2014 to August 2016. We analyzed the community characteristics, vegetation (shoots and roots), total carbon (TC), nutrients, soil (rhizosphere and bulk) properties, and the linkage between vegetation and soil under different N addition rates. Our results showed that (i) N addition significantly increased and decreased the concentration of soil nitrate nitrogen (NO3−-N) and ammonium nitrogen, and the soil pH, respectively; (ii) there were significant correlations between soil (rhizosphere and bulk) NO3−-N and total nitrogen (TN), and root TN, and there was no strong correlation between plant and soil TC, TN and total phosphorus, and their stoichiometry under different N addition rates. The results suggest that short-term low-N addition affected the plant community, vegetation, and soil TC, TN, TP, and their stoichiometry insignificantly, and that the correlation between plant and soil TC, TN, and TP, and their stoichiometry were insignificant

Nitrogen and Phosphorus Distribution and Relationship in Soils and Plants under Different Aged Chinese Fir Plantation

As essential nutrients for plant growth and development, the balance of nitrogen (N) and phosphorus (P) between soils and plants is a key component to ecosystem stability. In this study, we examined the distribution of nutrients in the soils and different organs of Chinese fir (Cunninghamia lanceolata) in Hunan Province, southern China. Additionally, we investigated the nutrient concentrations in soil layers (0–80 cm depth) and in plant organs, and the total biomass of 10-, 20-, and 30-year-old plantations. The results suggested that the nutrients in the soil were aggregated in the surface layer. The highest and lowest values of N concentrations in 0–80 cm soil layers and P concentrations in 0–40 cm soil layers were both in 30-year-old plantations and 20-year-old plantations, respectively. Nitrogen in the organs of Chinese fir in all plantations and P concentrations in the organs of 20- and 30-year-old trees decreased in the following order: leaves, fine roots, coarse roots, and stems. Total biomass (N and P pools of four organs) increased consistently with stand age increase, and N and P pools were the highest in leaves and stems, respectively. There were significant, positive correlations between N and P in the soil (0–80 cm), and organs, respectively, and also between N concentrations of fine roots and that of 0–10 and 10–20 cm soil, respectively. In Chinese fir plantations, concentrations of nutrients in specific tree organs and the soil were correlated positively, which can only partially explain the balance of nutrients within the plant–soil ecosystem. This study suggested that incorrect harvesting patterns may effectively deprive the forest ecosystem of valuable nutrients that would ordinarily have been returned to the soil

Quantitative Analysis of Sulfur Dioxide Emissions in the Yangtze River Economic Belt from 1997 to 2017, China

Economic development is responsible for excessive sulfur dioxide (SO2) emissions, environmental pressure increases, and human and environmental risks. This study used spatial autocorrelation, the Environmental Kuznets Curve (EKC), and the Logarithmic Mean Divisia Index model to study the spatiotemporal variation characteristics and influencing factors of SO2 emissions in the Yangtze River Economic Belt (YREB) from 1997 to 2017. Our results show that the total SO2 emissions in the YREB rose from 513.14 × 104 t to 974.00 × 104 t before dropping to 321.97 × 104 t. The SO2 emissions from 11 provinces first increased and then decreased, each with different turning points. For example, the emission trends changed in Yunnan in 2011 and in Anhui in 2015, while the other nine provinces saw their emission trends change during 2005–2006. Furthermore, the SO2 emissions in the YREB showed a significant agglomeration phenomenon, with a Moran index of approximately 0.233–0.987. Moreover, the EKC of SO2 emissions and per capita GDP in the YREB was N-shaped. The EKCs of eight of the 11 provinces were N-shaped (Shanghai, Zhejiang, Anhui, Jiangxi, Sichuan, Guizhou, Hunan, and Chongqing) and those of the other three were inverted U-shaped (Jiangsu, Yunnan, and Hubei). Thus, economic development can both promote and inhibit the emission of SO2. Finally, during the study period, the technical effect (approximately −1387.97 × 104–130.24 × 104 t) contributed the most, followed by the economic (approximately 27.81 × 104–1255.59 × 104 t), structural (approximately −56.45 × 104–343.90 × 104 t), and population effects (approximately 4.25 × 104–39.70 × 104 t). Technology was the dominant factor in SO2 emissions reduction, while economic growth played a major role in promoting SO2 emissions. Therefore, to promote SO2 emission reduction, technological innovations and advances should be the primary point of focus

Dominant Fungal Communities Aggregate in the Shallow Rhizosphere Soil of <i>Anabasis aphylla</i>

Rhizosphere soil microorganisms are significant factors affecting plant growth, especially that of saline–alkali tolerant plants in the desert ecosystem. We performed high-throughput sequencing in order to identifying the fungal community structures and their relationships to the physicochemical properties of different soil layers for the desert plant, Anabasis aphylla, in its natural environment. The number of unique operational taxonomic units (OTUs) found in the bulk soil of the 0–20 cm layer contributed to the biggest percentage (24.13%) of the overall amount of unique OTUs. Despite the fact that there was a rather large variety of fungi in the bulk soil of A. aphylla, the number of dominating fungi, which included Ascomycota, Microascus, and Arachnomyces, was found to be in quite high abundance in the rhizosphere soil. In the 20–40 cm layer of rhizosphere soil, the phylum Ascomycota accounted for 84.78% of the total phyla identified, whereas the species Microascus and Arachnomyces accounted for 24.72% and 37.18%, respectively, of the total species identified. In terms of the soil physicochemical properties, electric conductivity was the primary environmental component influencing the dominant fungi. The findings of this research enhance our comprehension of dominant fungi distributions and relevant environmental factors affecting the saline–alkali tolerant desert plant, A. aphylla. The results also provide a theoretical basis to help elucidate fungi adaptation mechanisms to the saline–alkali environment and methods for their isolation and screening

Dominant Fungal Communities Aggregate in the Shallow Rhizosphere Soil of Anabasis aphylla

Rhizosphere soil microorganisms are significant factors affecting plant growth, especially that of saline&ndash;alkali tolerant plants in the desert ecosystem. We performed high-throughput sequencing in order to identifying the fungal community structures and their relationships to the physicochemical properties of different soil layers for the desert plant, Anabasis aphylla, in its natural environment. The number of unique operational taxonomic units (OTUs) found in the bulk soil of the 0&ndash;20 cm layer contributed to the biggest percentage (24.13%) of the overall amount of unique OTUs. Despite the fact that there was a rather large variety of fungi in the bulk soil of A. aphylla, the number of dominating fungi, which included Ascomycota, Microascus, and Arachnomyces, was found to be in quite high abundance in the rhizosphere soil. In the 20&ndash;40 cm layer of rhizosphere soil, the phylum Ascomycota accounted for 84.78% of the total phyla identified, whereas the species Microascus and Arachnomyces accounted for 24.72% and 37.18%, respectively, of the total species identified. In terms of the soil physicochemical properties, electric conductivity was the primary environmental component influencing the dominant fungi. The findings of this research enhance our comprehension of dominant fungi distributions and relevant environmental factors affecting the saline&ndash;alkali tolerant desert plant, A. aphylla. The results also provide a theoretical basis to help elucidate fungi adaptation mechanisms to the saline&ndash;alkali environment and methods for their isolation and screening