[Objective] The soil nutrient characteristics and influencing factors of surface soil gully erosion for low hilly terrain in the black soil area were studied in order to provide data and theoretical support for the rational use of land resources, accurate management of soil fertility, and restoration of degraded soil in the black soil area. [Methods] Surface soil gully erosion for different types of eroded ditches in Yanshou County, Heilongjiang Province was determined by measuring and analyzing soil samples from the 0—40 cm layer in each part of the erosion gully. [Results] ① The contents of soil organic matter, total nitrogen, total phosphorus, total potassium, available phosphorus, available potassium, and alkali hydrolyzable nitrogen were significantly different (p<0.05) for different erosion gully types compared with the check treatment. As an erosion gully developed, soil organic matter decreased in the 0—40 cm layer, and the contents of total nitrogen, total phosphorus, total potassium, available phosphorus, available potassium, and alkali hydrolyzable nitrogen also decreased. These nutrient contents were significantly different (p<0.05) in different soil layers. Soil nutrient contents decreased with increasing depth. Because of erosion deposition, the contents of soil organic matter, total nitrogen, total potassium, and alkali hydrolyzable nitrogen decreased dramatically at the head of the gully, and at the same time, the contents of soil organic matter, available phosphorus, and available potassium decreased slowly. ② The soil degradation index followed the order of CK>A2>A1>A3 in the 0—40 cm layer as erosion gullies developed, and the soil was gradually degraded. [Conclusion] Soil nutrients had an overall significant negative correlation with bulk density, and soil nutrients were positively correlated with water stable aggregates and clay content. Soil profile differences were the fundamental reason for the variation in soil nutrients. Erosion gully development was the secondary reason for nutrient changes. The contents of soil organic matter, total nitrogen, and total potassium were also affected by positional differences.

[Objective] The effects of erosion on the surface soil of erosion gullies in sloping cropland soils in a black soil area were studied in order to provide theoretical support for the rational utilization of soil resources and regional soil and water conservation work in black soil areas. [Methods] The study was conducted on erosion gullies with different degrees of development in Yanshou County, Harbin City, Heilongjiang Provicne. Particle size distribution and water storage properties of soil on the slope, at the bottom of the gullies and at the head of the gullies were quantitatively described. [Results] ① Soil bulk density, maximum water-storage capacity, maximum water-retention capacity, total storage capacity, dead storage capacity, and maximum effective storage capacity at different depths were significantly different (p<0.05). As soil depth increased, soil bulk density also increased, and water-storage, water-retention, and effective water storage capacity decreased. Each layer had a maximum water-storage capacity of about 90% of its saturated capacity, and the effective water utilization rates were 44.79% and 41.87%, respectively. The development of erosion gullies had a clear influence on effective soil water. ② The infiltration characteristics generally showed that the initial infiltration rate>the 30-minute infiltration rate>the stable infiltration rate. As soil depth increased, the infiltration characteristics of the three indicators decreased between gully A2 and A4 for different erosion degree gullies. In the 20—40 cm layer, the infiltration characteristics of gully A1 to A4 followed the order of CK (control group)> gully A1> gully A4> gully A2> gully A3. Infiltration initially declined and then increased. With the development of the erosion gully, soil infiltration decreased and then increased. ③ The development of erosion gullies was the main reason for the change in clay content. The percentage of clay in the 0—40 cm layer tended to increase first and then decrease. The percentage of sand in the 0—20 cm layer tended to decrease first and then increase, showing a trend toward increased coarseness. ④ The soil degradation index followed the order of gully A1> gully A2> gully A3> gully A4 in the 0—20 cm layer. Soil degradation increased with the development of erosion gullies. Soil degradation was most severe in gully A4. [Conclusion] The differences in soil profiles was the main reason for the differences in physical properties of black soil. Soil water-holding capacity in the 0—20 cm layer was weakened and soil degradation became severe as erosion gullies developed.

东北黑土区作为我国重要的粮食产区,侵蚀沟发育导致土壤地力下降,严重制约了黑土区农业发展.为了分析黑土区侵蚀沟发育对表层土壤酶活性的影响,探究酶活性对侵蚀-沉积作用的响应机制,选取黑龙江省哈尔滨市延寿县双奎河双安村河段不同发育程度的侵蚀沟作为研究对象,测定不同发育程度侵蚀沟沟头、沟中、沟尾段 0～40 cm土层的碱性磷酸酶、脲酶、蔗糖酶、过氧化氢酶活性和土壤理化性质,并进行相关性分析和冗余分析,结果表明:①随着侵蚀发育,土壤酶活性总体呈下降趋势,随着土层加深,土壤酶活性降低;②4 类酶活性和土壤养分指标呈显著正相关、和土壤密度呈显著负相关,有机质含量是影响土壤酶活性最主要的因子;③在侵蚀-沉积作用下,土壤酶活性基本呈现沟头、沟中段随侵蚀发育而下降明显,沟尾段因沉积作用而下降减缓的规律.

[目的]阐明侵蚀作用对黑土区坡耕地侵蚀沟土壤结构及抗蚀性的影响机制,为黑土区坡耕地侵蚀沟道演变提供基础数据和理论支撑.[方法]以哈尔滨市延寿县不同发育程度侵蚀沟为研究对象,对切沟的沟头、沟坡和沟底土壤进行系统采样,采用常规方法测定土壤的结构及抗蚀性特征.[结果](1)各沟道间 WSA(10～0.25 mm 水稳性团聚体含量)、MWD(水稳性团聚体平均重量直径)、GMD(水稳性团聚体几何平均直径)、分形维数均差异性显著(p<0.05).随着侵蚀沟发育,MWD,GMD,分形维数在 0-20 cm土层均呈[CK(对照)>A1(稳定沟)>A2(半稳定沟前期)>A3(半稳定沟后期)>A4(发展沟)],为递减趋势;随着土层加深,大颗粒水稳性团聚体含量下降,结构恶化.(2)各沟道间分散系数、<0.05 mm分散率差异性显著(p<0.05).二者在 0-40 cm 土层总体呈递增趋势;主成分分析表明 0-20 cm与 20-40 cm土层的抗蚀性综合得分表现为CK>A1>A2>A3>A4.[结论]侵蚀沟发育是造成黑土土壤结构与抗蚀性差异的主要原因,0-40 cm土层中土壤结构趋于恶化,土壤抗蚀性减弱,可蚀性增强.

侵蚀沟造成了东北黑土区坡耕地大量的土壤流失,开展有关黑土区坡耕地侵蚀沟的研究对于土壤流失防治、耕地保护以及生态恢复具有重要意义.目前,在黑土区坡耕地侵蚀沟的发生发展的影响因素、预测、防治措施等方面进行了相关的研究.本文对当前的研究进行了深入的讨论和总结,指出当前对黑土区侵蚀沟分级分类缺乏细致标准的分类依据,对黑土区侵蚀沟影响因子的研究不够全面,对侵蚀沟治理的经济、生态效益以及各种治理措施的效果差异缺乏有效的定量评价.针对现有研究不足,提出了开展黑土区侵蚀沟分类分级体系的标准化,加强土壤、植物、工程措施和耕作措施等因子对侵蚀沟影响研究以及进行侵蚀沟治理措施效果的定量评价将是今后研究重点.

Poincare section is an important method for analyzing nonlinear systems. Choosing a suitable plane as the Poincare section is the key to using the Poincare section to analyze a nonlinear system. At present, it is still a difficult problem to select a suitable Poincare section when analyzing a nonlinear system. This is caused by two reasons. On the one hand, the classical method for selecting a partial Poincare section only applies to analyze a part of the nonlinear system orbit, whether the selected plane is a suitable Poincare section is affected by the different initial points. On the other hand, according to the actual situation, different researchers have different needs for Poincare section. In order to solve this problem, a new method named Projection Time Domain method is put forward in this paper. This method can help us not only directly reflect the intersection between the nonlinear system orbit and the selected plane, but also accurately adjust the direction and position of the selected plane in real time. It can be used to quickly find a plane which fully intersects the nonlinear system orbit or an arbitrary plane as a Poincare section. In this paper, the complete definition of Projection Time Domain method is given firstly. Then, the principle of Projection Time Domain method is theoretically analyzed in detail. At the same time, the rules for determining whether the selected plane is a suitable Poincare section in the time domain are also studied. Finally, it is introduced how to quantify the direction and position of the selected plane in the phase space. The simulation experiments are conducted with three typical three-dimensional and four-dimensional nonlinear systems by using this new method. The experimental results consistent with the theoretical analysis, which demonstrate the effectiveness and practicability of this method.

Extracting characteristic signal from a continuous signal can effectively reduce the difficulty of analyzing the running states of a single-variable nonlinear system. Whether the extracted characteristic signal can accurately reflect the running states of the system is very important. In this paper, a method called automatic sampling method (ASM) for extracting characteristic signals is investigated. The complete definition is described, the effectiveness is proved theoretically, and the general formulas of the extracted characteristic signals are derived for the first time. Furthermore, typical Chuaʼs circuit is used to accomplish a lot of experimental research on the aspect of frequency domain. The experimental results show that ASM is feasible and practical, and can automatically generate a characteristic signal with the change of the original signal.