[Impacts of freeze-thaw process on soil microbial nutrient limitation in slope farmlands of the Chinese Mollisol region].

Understanding the impacts of freeze-thaw action on soil microbial nutrient limitation can provide important support for sustainable utilization of black soil resources. We analyzed the impacts of freeze-thaw action on soil microbial nutrient limitation on a slope farmland located in a typical thick Mollisol region of Keshan County, Heilongjiang Province. We examined the responses of soil microbial nutrient limitation to soil erosion rates through measuring soil nutrient, soil microbial biomass, and soil enzyme activities before and after freeze-thaw under natural conditions, and estimated the soil erosion rates by Cs tracing technology.

Compound erosion effect of snowmelt, wind, and rainfall on sloping farmlands of Chinese typical Mollisol region.

Research on the processes and mechanisms of compound soil erosion by multiple forces can provide scientific guidance for precisely controlling cropland soil erosion. Based on the seasonal alternation of freezing-thawing, snowmelt, wind, and rainfall erosion forces on sloping farmlands under natural conditions from November to next October of each year, we used a set of indoor simulation experiments of multi-force superimpositions to analyze the compound soil erosion processes of snowmelt (1 and 2 L·min), wind (12 m·s), and rainfall (100 mm·h). We further discussed the erosion effects of multi-force superimpositions.

[Impacts of upslope inflow and soil pipe collapse on slope water erosion in the typical Chinese Mollisol region].

Understanding the effects of upslope runoff and soil pipe collapse on slope water erosion can provide scien-tific basis for preventing Mollisol degradation caused by soil erosion. We conducted an experiment to investigate the effects of upslope inflow rate and soil pipe collapse on slope water erosion and to quantify the contribution of soil pipe erosion to slope soil erosion. The experiment included three inflow rates (30, 40, and 50 L·min) and three near-surface soil hydrological conditions (without soil pipe: NP; with soil pipe but no pipe flow: PF; with pipe flow: PF).

[Effects of elevated CO concentration, warming, and winter wheat planting on soil enzyme activities].

Understanding the responses of soil enzyme activities to elevated CO concentration and warming can provide a scientific basis for nutrient management of croplands under global climate change. We conducted a pot expe-riment with climate chamber to examine the effects of elevated CO concentration and warming and winter wheat growth on soil enzyme activities. There were four climate scenarios: control (CK, 400 μmol·mol CO concentration+normal ambient temperature), and CO concentration elevation (ECO, 800 μmol·mol CO concentration+normal ambient temperature), elevated temperature (ET, 400 μmol·mol + temperature increased 4 ℃), and elevated CO concentration and temperature (ECO+T, 800 μmol·mol CO concentration + temperature increased 4 ℃).

[Effects of soil erosion and deposition on the spatial distribution of soil microbial quantity in Mollisol area of Northeast China.].

Revealing the responses of soil microbial community to soil erosion can provide guidance for agricultural ecosystem management. We investigated the impacts of soil erosion intensity on soil microbial quantity at the Binzhou River Basin, a typical thin layer Mollisol area in Bin County of Heilongjiang Province, using Cs tracer. The results showed that there were seasonal variations in soil microbial quantity.

[Impacts of seepage flow and soil thaw depth on hillslope snowmelt erosion in Chinese Mollisol region].

Snowmelt erosion is an important way of soil loss in Chinese Mollisol region. However, little is known about the effects of seepage flow and soil thaw depth on hillslope snowmelt runoff erosion. An indoor simulated experiment was conducted to analyze the impacts of seepage flow and soil thaw depth on hillslope snowmelt erosion.

[Effects of near-surface soil water conditions on agricultural non-point source pollutant transport].

Agricultural non-point source pollution is one of severe problems for water environment of agricultural area in China. The effects of near-surface soil water conditions on agricultural non-point source pollutant (AGNSP) transport during soil erosion processes, especially antecedent soil moisture was saturated, was developed by using artificial simulation rainfall experiment. The results showed that antecedent soil water content had great impact on AGNSP transport during soil erosive processes.

Effects of near-surface hydraulic gradients on nitrate and phosphorus losses in surface runoff.

Phosphorous (P) and nitrogen (N) in runoff from agricultural fields are key components of nonpoint-source pollution and can accelerate eutrophication of surface waters. A laboratory study was designed to evaluate effects of near-surface hydraulic gradients on P and N losses in surface runoff from soil pans at 5% slope under simulated rainfall. Experimental treatments included three rates of fertilizer input (control [no fertilizer input], low [40 kg P ha(-1), 100 kg N ha(-1)], and high [80 kg P ha(-1), 200 kg N ha(-1)]) and four near-surface hydraulic gradients (free drainage [FD], saturation [Sa], artesian seepage without rain [Sp], and artesian seepage with rain [Sp + R]).