Comparison of the Responses of Soil Fungal Community to Straw, Inorganic Fertilizer, and Compost in a Farmland in the Loess Plateau

Determining the response of soil fungi in sensitive ecosystems to external environmental disturbances is an important, yet little-known, topic in microbial ecology. In this study, we evaluated the impact of traditional fertilization management practices on the composition, co-occurrence pattern, and functional groups of fungal communities in loessial soil.

Effect of Wheat Straw Biochar on Thermophysical Properties of Loessial Soil

Soil thermophysical properties are the key factors affecting the internal heat balance of soil. In this paper, biochars (BC300, BC500 and BC700) were produced with wheat straw at the temperatures of 300, 500 and 700°, respectively. The effects of biochar amendment at the rates of 0%, 1%, 3%, and 5% on the thermophysical properties (thermal conductivity, heat capacity, and thermal diffusivity) of a loessial soil were investigated with and without water content respectively. Although the bulk density of soil significantly decreased with biochar amendment, due to enhancing soil porosity and organic matter content, the thermophysical properties of soil did not change largely with biochar amendment rate and pyrolysis temperature. Water content exhibited significant effects on the thermophysical properties of soils added with biochars, where the thermal conductivity and heat capacity of soil were linearly proportional to water content, the thermal diffusivity initially increased and then decreased with the increase of water content. In the meanwhile, there was no significant correlation between the biochar amendment rate or pyrolysis temperature and thermophysical properties. The results show that water content should be mainly concerned as a factor when the internal heat balance of loess soil is evaluated, even though the soil is amended with biochar.

Rebuilding soil organic C stocks in degraded grassland by grazing exclusion: a linked decline in soil inorganic C

Background Our study evaluated how soil organic carbon (SOC) and soil inorganic carbon (SIC) recovered over time in deep loessial soil as overgrazed grassland was fenced and restored. Methods The study was conducted in the Yunwu Mountain Nature Reserve in the Ningxia Autonomous Region of China. In it we compared soil data from three grazed grassland (G) sites, three sites that were fenced for 15 years (F15), and three sites that were fenced for 30 years (F30) as a so-called ‘space for time series’. Results and Discussion We compared SOC accumulation in soil up to 200 cm below the surface in G, F15, and F30 plots. An increase in SOC correlated with a decrease in soil pH, and decreased soil bulk density. However, SOC sequestration in fenced plots was largely offset by a decrease in SIC, which was closely correlated (r = 0.713, p = 0.001) with SOC-driven soil pH decline. We observed no significant increase in soil total carbon in the F15 or F30 sites after comparing them to G. Conclusions Our data indicate that fencing causes the slow diffusion processes to intensify the soil property changes from increased litter return, and this slow diffusion process is still active 30 years after fencing at 100–200 cm soil depths in the studied deep loessial soil. These findings are likely applicable to similar sites.

Significance of substrate soil moisture content for rockfall hazard assessment

Rockfall modelling is an important tool for hazard analysis in steep terrain. Calibrating terrain parameters ensures that the model results more accurately represent the site-specific hazard. Parameterizing rockfall models is challenging because rockfall runout is highly sensitive to initial conditions, rock shape, size and material properties, terrain morphology, and terrain material properties. This contribution examines the mechanics of terrain impact scarring due to rockfall on the Port Hills of Christchurch, New Zealand. We use field-scale testing and laboratory direct shear testing to quantify how the changing moisture content of the loessial soils can influence its strength from soft to hard, and vice versa. We calibrate the three-dimensional rockfall model RAMMS by back-analysing several well-documented rockfall events that occurred at a site with dry loessial soil conditions. We then test the calibrated “dry” model at a site where the loessial soil conditions were assessed to be wet. The calibrated dry model over-predicts the runout distance when wet loessial soil conditions are assumed. We hypothesize that this is because both the shear strength and stiffness of wet loess are reduced relative to the dry loess, resulting in a higher damping effect on boulder dynamics. For both realistic and conservative rockfall modelling, the maximum credible hazard is usually assumed; for rockfall on loess slopes, the maximum credible hazard occurs during dry soil conditions.