Significant loss of soil inorganic carbon at the continental scale.

Widespread soil acidification due to atmospheric acid deposition and agricultural fertilization may greatly accelerate soil carbonate dissolution and CO2 release. However, to date, few studies have addressed these processes. Here, we use meta-analysis and nationwide-survey datasets to investigate changes in soil inorganic carbon (SIC) stocks in China. We observe an overall decrease in SIC stocks in topsoil (0-30 cm) (11.33 g C m-2 yr-1) from the 1980s to the 2010s. Total SIC stocks have decreased by ∼8.99 ± 2.24% (1.37 ± 0.37 Pg C). The average SIC losses across China (0.046 Pg C yr-1) and in cropland (0.016 Pg C yr-1) account for ∼17.6%-24.0% of the terrestrial C sink and 57.1% of the soil organic carbon sink in cropland, respectively. Nitrogen deposition and climate change have profound influences on SIC cycling. We estimate that ∼19.12%-19.47% of SIC stocks will be further lost by 2100. The consumption of SIC may offset a large portion of global efforts aimed at ecosystem carbon sequestration, which emphasizes the importance of achieving a better understanding of the indirect coupling mechanisms of nitrogen and carbon cycling and of effective countermeasures to minimize SIC loss.

Element Geochemistry of Lake Sediments from L07-10 in the "Great Ear" Area of Lop Nur and Its Significance for Climate Variation Change with ICP-OES.

Spectral analysis techniques were applied to geochemical element analysis to provide additional environmental data about evolution of salt lakes and climate change. The elements composition of lake sediments from L07-10 in the "Great Ear" Area of Lop Nur was analyzedby using Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES )and from 14 C carbon dating by using the EN accelerator mass spectrometry (AMS).This paper estimated the climate change in this region since 16.34 ka BP. Results demonstrate that the geochemical characteristics of major elements at all sediment levels can indicate environmental change sensitivity, and element composition is more sensitive to climate change. Overall, climate succession since 16.34 ka BP had been: warm-wet, warm-dry, cold-wet and warm-dry. From 8.09~6.34 ka BP，the climate obviously heated up and was warmer and drier, which is consistent with global and regional climate change estimates from other studies. By about 2 ka BP, the climate becomes warmer and drier and the water carrying capacity of this lake was reduced.

[Study on relationship between alfalfa canopy spectral reflectance and leaf water content].

In the present study, alfalfa canopy reflectance was researched at alfalfa squaring period under different irrigation amount at the hutubi county grassland ecological station. Determining the spectral diagnostic model of alfalfa leaf moisture content was determined by spectrometry. The results showed that (1) The spectral reflectance of alfalfa canopy gradually decreases with the increase in the leaf water content in the near infrared. (2) The spectral inversion model of alfalfa leaf moisture content established by normalized reflectance spectra is superior to the original reflectance spectra, and the prediction model established in the 1,344-1,660 nm band has the lowest average relative error (7.8%). (3) In this study, the spectral diagnostic model of the leaf moisture content is: Y=0.962 - 7.560X1451 + 5.295X1473. The spectral prediction model of the alfalfa leaf moisture content can provide a basis for decision making for scientific irrigation of alfalfa.

[Measuring soil water content by using near infrared spectral characteristics of soil].

Different textured soils (sandy loam, silty clay loam and clay) from Manas County, Xinjiang were researched with indoor spectral reflectance, continuum removal was used to process soil spectra curve, and correlation analysis was made about normalized spectral reflectance and water content for modeling. The results show that different textured soils have reflectance in a order that clay>silty clay loam>sandy loam; the critical points of field capacity in sandy loam, silty clay loam and clay were 20.01%, 24.10% and 30.43% respectively, and water content was inversely proportional to spectral reflectance below such critical points while proportional above the points. Within 1390-1623 nm band, the negative correlation coefficients of soil water content and normalized spectra reflectance show better negative correlation and reaching significant levels, R2 of the model established for soil water content prediction exceeded mostly 0.8, and the average relative error of the model was 10%. The model could accurately reflect the soil moisture content, Its advantages such as accuracy, non-destruction and rapidness provide a new approach to measuring soil water content.

[Analysis of Cd pollution & spatial variability characteristics of typical agricultural soils in suburbs of Urumqi City, Xinjiang].

Cd content in agricultural soils from 4 townships in north suburb and 2 townships in south suburb of Urumqi City was determined with graphite furnace (GF-990) atomic absorption spectrometry, and the spatial variability of Cd content there was analyzed with geo-statistics method. The result indicates that Cd content from the sampling points in north suburb exceeds the stipulated standard and falls into medium or strong spatial variability with nugget value > 75%, which explains a weak self-correlation among those variable spaces under mainly the impact of random factors of external pollution such as local fertilization level, irrigation and cultivation etc. Cd content from the sampling points in north suburb does not exceed the stipulated standard but approaches to the critical warning value with nugget value at 50.2%, which falls into medium self-correlation among those variable spaces. Spatial variability characteristics of Cd distribution in suburban agricultural soils of Urumqi City, Xinjiang were studied in this paper for providing scientific basic data to source analysis and control of Cd pollution in the far mLands there.