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Karst landforms are widely distributed in southern China. The terrain and soil properties in karst basins are complex, which results in high spatial heterogeneity of the ecological environment and soil organic matter (SOM) in karst watersheds. To investigate the spatial distribution characteristics of SOM in different land uses in the karst plateau basin, a total of 3,816 soil samples were taken from 568 soil profiles. The soil animals and different soil properties were recorded, and the concentration of SOM was tested using the potassium dichromate method in the laboratory. Then, the changes in the SOM content associated with soil animals and the soil properties associated with the different land use types were analyzed. The results showed a large discrepancy in SOM in the karst plateau basin. The average values of SOM in different soil layers were between 9.23 g kg-1 and 59.39 g kg-1. The SOM decreased in the following order: forestland > grassland > barren land > cultivated land > garden land. The SOM in soil in which soil animals are present is generally greater than that in the absence of soil animals, and the SOM partially increases with soil species diversity. Agrotis segetum is the main soil animal species that positively affects the distribution of organic matter in the surface soil layer. The SOM in soil with the phylum Annelida is much greater than that in soils with other animals, and earthworms are the main contributor. The structure of soil animal species is complex, and the change trend of SOM is stable. The major positive factors affecting soil animal diversity are soil thickness, soil humidity and soil structure, and rock outcrops are the main negative factor. In summary, good land use can increase animal diversity and abundance in soil, which promotes soil organic matter accumulation. Moreover, microtopography is an important factor that influences soil organic matter accumulation in karst basins and further affects the restructuring of the spatial distribution of soil organic matter. [ABSTRACT FROM AUTHOR]

Using the grid-based sampling method, 2755 soil profiles consisting of 22,057 soil samples were sampled and analyzed to study the spatial distribution and storage of soil organic carbon (SOC) in the Houzhai River Basin in Guizhou Province, a typical karst region in southwestern China. The results suggest that the total levels of SOC stored in the 0-10, 0-20, 0-30, and 0-100 cm soil layers of the Houzhai River Basin are approximately 1.48 x 108, 2.65 x 108, 3.44 x 108, and 5.39 x 108 kg C, respectively. SOC content and soil bulk density levels were found to vary depending on the land use. In the 0-50 cm soil layer, forest SOC content levels (including arbor forests, arbor--shrub mixed forests, shrubland, and shrub grassland) are generally higher than those of uncultivated land, followed by grassland and cropland (including paddy fields, arid land, sloping cropland, and abandoned cropland), gardens, and orchard. It is believed that land use is a vital factor directly affecting carbon storage patterns in the study area. Soil thickness, rock outcrop, and slope gradients are the main factors in arrangement of land use by local governments and peasants. This study has established a feasible method for assessment of SOC stock in karst mountainous areas. The findings of this study are applicable to other karst mountainous regions globally. [ABSTRACT FROM AUTHOR]

The Plain Forestation Project is an important measure designed to alleviate air pollution in Beijing, the capital of China. Ten commonly cultivated forest types of the Plain Forestation Project were studied at three growth stages of leaves. The particulate matter (PM)2.5 concentrations and forest structures were surveyed to analyze the PM2.5 concentration differences between different forest types, and establish a linear relationship between forest structures and PM2.5 concentration differences. The results suggested that forest ecosystems can block and capture PM2.5 from the air. Forests with luxuriant foliage are most effective in removing PM2.5 from the air. The average PM2.5 mass concentration in the Leaf-on Period (LOP) was the lowest when compared with other periods. The PM2.5 concentrations in the forest usually were higher than the control. Correspondingly, PM2.5 concentration indexes were negative values during daytime, but this results were reversed at night. Forests can reduce the diffusion rate of PM2.5 leading to PM2.5 were detained in the forest during daytime, and play an important role in the adsorption or deposition of particulate matter at night. Forest structure was primary reason of the PM2.5 concentration difference between different forests. The PM2.5 concentration index was positively correlated to canopy density, leaf area index (LAI), and mean diameter at breast height (DBH), and negatively correlated to the average tree height (height), forestland area, grass coverage and height. [ABSTRACT FROM AUTHOR]

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Spatial patterns of soil nutrient (N and P) were examined using geostatistical analysis in three different soil horizons (A, B, C) in a mixed forest in Beijing China. Soil nutrients (total nitrogen or TN, total phosphorous or TP, and available nitrogen or AN) were high near the surface and lower with depth. In general, the spatial correlation in soil nutrient content varied by depth. Soil nutrient content was also strongly influenced by vegetation type and elevation. These results consist of a set of simple statistical models that could provide information for the planning of the forest management and long-time research in this area. [ABSTRACT FROM AUTHOR]

Soil properties are crucial in forest ecological management and rare vegetation protection. In this study, Fanjing Mountain, a typical subtropical forest, was used to investigate and analyze the differences in soil properties and climate change characteristics of Fanjing Mountain in 1982 and 2014. Then redundancy analysis was used to analyze the influence of climate factors on soil properties. The results showed that: 1) Compared to 1982, the soil properties of Fanjian Mountain changed significantly in 2014. The soil texture evolved from a silty loam in 1982 to a silty clay loam in 2014. There was a significant increase in soil clay particles. In addition, the soil showed acidification, weakened cation exchange capacity, and relatively stable soil total nitrogen but significant loss of soil organic matter and total phosphorus nutrients. 2) In the past 32 years, the environmental climate of Fanjing Mountain has shown the characteristics of increasing annual average temperature and annual rainfall, frequent extreme temperature, widening the annual temperature range and decreasing annual relative humidity. 3) Soil type and maximum annual temperature have a highly significant effect on the evolution of soil properties, while annual rainfall and slope orientation significantly affect the evolution. Conclusion: The evolution of soil properties in subtropical forests is dominated by their type differences and climate warming. [ABSTRACT FROM AUTHOR]

Due to human activity and global climate change, the Yellow River Delta, the youngest delta wetland in China, is suffering serious degradation. The study of hydrological connection provides new perspectives and technical support for the protection and restoration of delta wetlands. To quantify the interaction between the hydrological connection and the root–soil complex, the current study took dye-tracing experiments to examine the small-scale hydrological connectivity in soil where Phramites australis grew. The dye coverage was selected as the indicator of hydrological connectivity after preliminary analysis in this study. The main results were that (1) the strength of hydrological connectivity was negatively related to the microaggregates content, but had little to do with other soil physical properties; (2) there was a notable positive correlation between the indexes of thick root (D > 5 mm) and the dye coverage hydrological connectivity, while root biomass had little effect on hydrological connectivity; and (3) the influence of the microaggregate content dominated in the combined effect of the total surface area of the root (D > 5 mm) and the microaggregate content on hydrological connectivity in each soil layer. • Quantifying the effect of root-soil complex on hydrological connectivity. • Abundant thick roots and less microaggregates improve the hydrological connectivity. • Microaggregates dominated in effect of root-soil complex on hydrological connectivity. • Hydrological connectivity of wetland with high water content is more difficult to assess. [ABSTRACT FROM AUTHOR]

Atmospheric particulate matter is a wide-ranging environmental pollutant that can cause serious harm and poses a serious threat to public health. In this study, the near-surface particulate matter removal ability was quantitatively analyzed and compared for different land types under different pollution levels. The results showed that the concentrations of particulate matter 10 μm or less in diameter (PM10) and 2.5 μm or less in diameter (PM2.5) were higher in the morning and lower in the afternoon and that the seasonal variation was autumn > winter > spring > summer at a forest site. The diurnal concentration of particulate matter at a wetland site decreased continuously, with a seasonal variation of winter > autumn > spring > summer. The annual variation in the particulate matter concentration was higher in 2017 than in 2016 at both the forest and wetland sites. Forests remove particulate matter via plant leaves and root absorption, and wetlands rely on the enhancement of the relative air humidity to promote the absorption and accumulation of particles. For different air pollution levels, the deposition flux of PM2.5 increased with the pollution gradient. For the same air quality pollution level, the deposition flux of PM2.5 at the forest site was approximately 1.29 times higher than that at the wetland site. Data concerning PM10 in forests and wetlands are lacking. The results show that the deposition effect of the forest on particulate matter was better than that of the wetland.