Exploring the distribution and evolution of soil nutrients, it is needed to maintain quality of land and ensure food production. Based on geostatistical theory, 1,054 soil sites were selected from the surface (0-20 cm) of the typical black soil area in Northeast China. The spatial structure of soil pH, alkali-hydrolyzed N, effective P, and available K was investigated using Kriging and spatial statistics. The soils in the study area are acidic, alkali-hydrolyzed N, effective P, and available K content at moderate to high levels. Coefficients of variation for various nutrients ranged from 5 to 80%, all showing moderate variation. The pH, alkali-hydrolyzed N, effective P, and available K increased from South to North, the value of soil nutrients near the city were high. The results provide reference values for future work targeted at improving food security and reducing the effect on the environment.
Ecological vulnerability is the focus of research on global environmental impact, regional sustainable development, ecological civilization, and green development. There are eight deserts and four sandy lands in northern China. The ecological environment is sensitive to climate change and human activities. It is of great significance to carry out long-term sequential ecological vulnerability assessments. Therefore, taking northern China as the research area, this paper selects 13 data indicators such as climate, topography, and soil based on the ecological sensitivity-ecological recovery-ecological pressure model (SPR) and uses the spatial principal component analysis method (SPCA) to quantitatively evaluate the spatial and temporal differentiation characteristics and driving forces of ecological vulnerability in this area from 1980 to 2020. The results showed that areas with extreme, severe, and moderate vulnerability dominated northern China, accounting for 74.58% of the total area. The analysis revealed a decrease in ecological vulnerability from west to east and north to south. Meanwhile, from the perspective of timing, the overall level of ecological vulnerability showed an upward trend before 2000, and the overall level of ecological vulnerability continued to decline after 2000, and the quality of the ecological environment improved. During the study period, areas in northern China with severe vulnerability and slight vulnerability showed a change of 15.53% and -14.01%, respectively. The main reason for the change in ecological vulnerability is the frequent transformation between forest land, grassland, water, and cultivated land. In addition, the study found a spatial autocorrelation of ecological vulnerability of northern China and a significantly positive correlation. After 2000, the spatial aggregation of vulnerability was high-high cluster, which was mainly distributed in northwest China. The study’s findings will provide a robust scientific basis for ecosystem management and sustainable development.
China is a huge agricultural country with rich straw resources. However, the problem to be solved urgently is to find means to use crop straw effectively and reasonably. To study the influence of no-tillage straw mulching measures on soil compactness and soil organic matter, taking the black soil straw mulching no-tillage test field in Gaojia Village, Lishu County, Jilin Province as the research object, the characteristics of soil compactness and organic matter in different tillage layers under different cover years of no-till straw are discussed. The results show the following: (1) in the 0–50 cm tillage layer, the highest treatment method of soil organic matter is NT1 (no-tillage corn stover mulching for one year), with an average value of 2.62%, and the soil organic matter content of NT1 treatment increased by 57.46% compared with RT (ridge tillage). (2) The compactness of surface soil (0–20 cm) no-tillage soil is higher than RT, with an increase of more than 6.87%, and the compactness of deep soil (20–50 cm) no-tillage soil is lower than RT, with a decrease of more than 23.48%. (3) No-tillage can improve the agglomeration structure of the surface soil, increase the moisture content of the surface soil, reduce the volume of the surface soil, and improve the organic matter content of the surface soil, thus increasing the firmness of the surface soil. This study can provide a theoretical basis for promoting the comprehensive utilization of straw resources and developing eco-agriculture.
Soil total carbon (STC) and total nitrogen (TN) play important roles in providing essential nutrients for vegetation growth, improving soil structural properties, dissipating organic pollutants, and reflecting the fertility of black soils. Based on 1,057 soil samples collected 0 to 20 cm below the surface, geostatistical analysis was used to explore the spatial distribution and factors influencing STC, TN, and C/N ratios in the study area, which is a typical black soil area in northeast China measuring 83,439.04 km2. The soil sampling points were based on randomness and accessibility, spaced 1.25 km apart. The average STC and TN contents and C/N ratios in typical black soil areas of northeast China were 19.25 and 1.88 g kg–1 and 10.07, respectively, and the STC and TN were significantly higher than the national averages (13.26 and 1.32 g kg–1, respectively). The spatial distribution showed a decreasing trend from northeast to southwest, and the nucleation density of STC and TN was highest in the central part and decreased to the north and south. The STC and TN contents and C/N ratio were highest in clayey soil and were 46.11 and 4.23 g kg–1 and 11.39, respectively. The sandy soils had the lowest STC, TN, and C/N ratios. The distribution of STC and TN content is governed by multiple factors, such as human activities, soil type, climate, topography, soil acidity and alkalinity, and land use changes. This study provides the benchmark needed for the development and conservation of China's black soil resources.
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