Institute of Soil and Water Conservation,Chinese Academy of Sciences and Ministry of Water Resources
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Effects of wildfire and topography on soil nutrients in a semiarid restored grassland
No full textWildfire and topography each have significant effects on soil biogeochemical cycles, but their interactive effects on soil nutrients remain largely unclear, hindering the precise prediction of the effects of fire on soil biogeochemical cycles in a larger spatial scale. We examined soil nutrient contents from restored grass slopes that had suffered wildfires and adjacent restored grass slopes without any wildfire. Topographic factors included slope aspects (north and south slopes) and positions (upper, middle and lower slopes). Fire significantly increased the contents of soil organic carbon (OC), total nitrogen (TN) (0-10 cm), ammonium (NH4 (+)), and extractable phosphorous (EP), decreased the contents of nitrate (NO3 (-)) and available potassium (AK), and had minimum influence on total phosphorus (TP) content. Slope aspect and position also affected soil nutrients, with higher contents in the north slope than the south slope and at the upper slope than the lower slope. The effects of fire on soil OC, TN, and NO3 (-) were consistent across north and south slopes, but the effects on soil NH4 (+), TP, EP and AK varied with slope aspect. However, the effects of fire on soil nutrients were not influenced by slope position. These results indicate that slope aspect should be considered in predicting the response of soil biogeochemical cycles to fire
Testing association between soil bacterial diversity and soil carbon storage on the Loess Plateau
No full textBacteria are widely distributed and play an important role in soil carbon (C) cycling. The impact of soil bacterial diversity on soil C storage has been well established, yet little is known about the underlying mechanisms and the interactions among them. Here, we examined the association between soil bacterial diversity and soil C storage in relation to vegetation restoration on the Loess Plateau. The dominant phyla among land use types (artificial forest, Af; natural shrubland, Ns; artificial grassland, Ag; natural grassland, Ng; slope cropland, Sc) were Acidobacteria, Actinobacteria, Alphaproteobacteria, and Betaproteobacteria, which transited from Acidobacteriadominant to Actinobacteria-dominant community due to vegetation restoration. Soil C storage and the Shannon diversity index of soil bacterial community (H-Bacteria) showed the orderNs N > Ng > Af > Ag > Sc, whereas no significant differencewas found in Good's coverage (p > .05). Further, a strong relationship was observed between the relative abundance of dominant bacterial groups and soil C storage (p 70% of the variation and suggesting a strong association between soil C storage and soil bacterial diversity. Overall, we propose that further studies are necessary with a focus on the soil bacterial groups with specific functions in relation to soil C storage on the Loess Plateau. (C) 2018 Elsevier B.V. All rights reserved
Magnetic susceptibility characteristics of surface soils in the Xilingele grassland and their implication for soil redistribution in wind-dominated landscapes: A preliminary study
No full textWind erosion processes in the typical temperate Xilingele grassland of North China result in significant regional surface soil fine particle and carbon loss. They increasingly restrict local grass industry sustainable production and grassland ecosystem protection. It is challenging to link wind erosion and deposition at landscape scale using classical field monitoring or the expensive fallout environmental radionuclides tracing techniques. The low-cost but efficient magnetic susceptibility (MS) technique has been successfully demonstrated to have great potential to trace soil water erosion processes and patterns at large spatial and temporal scales. However, so far soil wind erosion research using MS technique has not been reported. This study had a trial to determine the variations of soil magnetic susceptibility on relative flat grassland by a grid soil sampling and to establish the relationship between wind erosion parameters and variations of MS in surface soils. 160 grid sampling sites were spaced at an interval of 400 m across a study transect with 12.8 km long and 1.6 km wide. 319 soil samples were collected from the surface soils (0-1 cm and 1-6 cm layers). Grazing intensity of the sampling sites were investigated, and the samples were measured for mass-specific low-frequency magnetic susceptibility (chi(lf)), absolute frequency dependent magnetic susceptibility (chi(fd)), percentage frequency-dependent magnetic susceptibility (chi(fd)%), soil grain size and organic carbon concentrations. The results showed that the chi(lf), chi(fd) and chi(fd)% values in surface soils ranged from 30.0 to 97.8 x 10(-8) m(3) kg(-1), 1.2 to 6.1 x 10(-8) m(3) kg(-1) and from 3.2 to 8.0%, respectively. The variations of soil chi(lf) values were closely related to grazing intensity, soil grain size and organic carbon concentrations, suggesting that soil erosion processes were very sensitive to soil properties. Moreover, the MS parameters (chi(lf), chi(fd)%) were positively correlated with the soil erosion rates and negatively correlated with the dust deposition rates, indicating that MS parameters could potentially identify the erosion and dust deposition stages of wind dominated erosion processes in semi-arid grassland, respectively. These preliminary experimental results implied that magnetic susceptibility signals in surface soils will hopefully serve as a useful tool in the accuracy assessment of wind dominated erosion and deposition in the temperate grassland regions
How Does Silicon Mediate Plant Water Uptake and Loss Under Water Deficiency?
No full textIn plants, water deficiency can result from a deficit of water from the soil, an obstacle to the uptake of water or the excess water loss; in these cases, the similar consequence is the limitation of plant growth and crop yield. Silicon (Si) has been widely reported to alleviate the plant water status and water balance under variant stress conditions in both monocot and dicot plants, especially under drought and salt stresses. However, the underlying mechanism is unclear. In addition to the regulation of leaf transpiration, recently, Si application was found to be involved in the adjustment of root hydraulic conductance by up-regulating aquaporin gene expression and concentrating K in the xylem sap. Therefore, this review discusses the potential effects of Si on both leaf transpiration and root water absorption, especially focusing on how Si modulates the root hydraulic conductance. A growing number of studies support the conclusion that Si application improves plant water status by increasing root water uptake, rather than by decreasing their water loss under conditions of water deficiency. The enhancement of plant water uptake by Si is achievable through the activation of osmotic adjustment, improving aquaporin activity and increasing the root/shoot ratio. The underlying mechanisms of the Si on improving plant water uptake under water deficiency conditions are discussed
Life cycle assessment of large-scale and household biogas plants in northwest China
No full textIn northwest China, large-scale (modern) and household biogas production (conventional) plants are the two main methods of biogas fermentation, a promising means of livestock waste disposal and effective agricultural recycling. Differences in the operating mechanisms of the two systems result in differences in their environmental performance. In this study, detailed life cycle assessments of large-scale and household biogas production were conducted to compare their environmental performance in terms of energy use and environmental impact potential per function unit (2136 tonne/yr of manure flowing into the biogas plant). Data were collected over a two-year period (2014-2016). The results showed that the total biogas output from the large-scale digester was 1.88 times that of the household digester. Net energy output did not differ much between the two systems, due to the high energy consumption of the large-scale plant during production. The energy-use efficiency of the large-scale plant was 1.29 times that of the household plant due to the use of co-products. Higher carbon dioxide and volatile organic compound emissions from the burning of biogas in the large-scale plant caused a higher potential for global warming and photochemical oxidation. However, higher ammonia and sulfur dioxide emissions occurred in the household plant, resulting in a higher potential for eutrophication, acidification and human toxicity. In conclusion, the waste of extra biogas for heat in large-scale biogas production, and undeveloped management, emissions through poor air-tightness and lack of technical biogas purification in household biogas production are the main hotspots to improve the environmental performance. (C) 2018 Elsevier Ltd. All rights reserved
不同植被带生态恢复过程土壤团聚体及其稳定性-以黄土高原为例
No full text为分析黄土高原不同植被带植被恢复对土壤团聚体分布特征及其稳定性的影响,以黄土高原从北到南不同纬度梯度分布的3 个典型植被类型区域(草原带、森林草原带和森林带)为研究对象,对不同植被类型和恢复年限下的土壤团聚体分布及其稳定性进行了研究.结果表明:不同植被对土壤团聚体分布及其稳定性影响显著,大于0.25mm 团聚体含量(WR 0.25 )、稳性团聚体平均重量直径(E WMD )、水稳性团聚体几何平均直径(E GMD )和有机质含量(SOM)整体上均表现为:森林带>森林草原带>草原带.不同植被带下不同恢复类型对土壤团聚体及其稳定性影响不一,森林草原带表现为灌木>草地>乔木,森林带则表现为乔木>草地.随植被恢复年限增大,各种恢复类型WR 0.25 、E GMD 、SOM 整体呈逐渐增加趋势,团聚体结构破坏率(PAD)和可蚀性因子(K)呈现相反的变化趋势;分形维数(D)无显著差异.冗余分析表明,植被带对土壤团聚体及其稳定性的影响最大,其次是恢复年限,恢复类型与植被带和恢复年限具有较强的交互作用.本研究有利于加强对区域生态恢复过程机理的认识</p
董志塬区气象干旱特征及其对作物产量的影响
No full text本文利用1955 — 2013 年庆阳市西峰气象站气象数据及1991 — 2013 年西峰区冬小麦、春玉米和马铃 薯产量统计数据，分析了该区域气象干旱特征及其对作物产量的影响。结果表明:( 1) 近 60 年来，董志塬区的降 水量和干燥度年际变化显著，1985 年之后起伏进一步加大。整体上看，降水量呈微弱下降趋势，干燥度表现出微弱 上升趋势; 多年平均降水量为550. 6 mm，多年平均干燥度为 1.81。干燥度最大值出现在1995 年，为 3.22，相应年 份的降水量负距平达到了最大值( －216.9 mm) 。( 2) 前一年8 — 9 月份降水量及干燥度对当年冬小麦产量的影响 都达到了极显著水平( P<0.01) ，表明播种前底墒对冬小麦产量影响很大; 6 — 7 月份干燥度、降水量对春玉米产量 的影响达到了显著水平( P<0.05) ，其中， 7 月份的影响最大; 而在6 月份，干燥度对马铃薯产量的影响达到显著水平，但降水量对其产量的影响却未达到显著水平。粮食产量除了受到气象条件的影响外，品种、管理措施也是影响 其变化的重要方面。 </p
Analyzing the Impacts of Climate Variability and Land Surface Changes on the Annual Water–Energy Balance in the Weihe River Basin of China
No full textEffectiveness and Durability of Polyacrylamide (PAM) and Polysaccharide (Jag C 162) in Reducing Soil Erosion under Simulated Rainfalls
No full textPolymers as a soil amendment is one of the effective measurements to reduce soil erosion. In this study, two polymers, polyacrylamide (PAM) and polysaccharide (Jag C 162), were applied to erosion plots filled with loess soil (tilted at 20 degrees). For each polymer, four concentration levels-0, 10, 30, and 50 kg.ha(-1)-were applied. The treated erosion plots were then subjected to two simulated rainfall events (dry and wet run) to investigate their effectiveness and durability in controlling soil erosion. Both simulated rainfall events were at an intensity of 120 mm.h(-1), and each event lasted for 30 min with 24 h free drainage in between. Results show that both polymers could reduce runoff, effectively control sheet erosion, and promote soil aggregates due to their capability to bind and stabilize soil particles. Such reducing effects were more pronounced on the Jag C 162-treated plots than on the PAM-treated plots. However, during the second (wet) run, there was more reduction of aggregate with size of >0.25 mm and greater increment of soil loss on the Jag C 162-treated plots than on the PAM-treated plots