Key Physical Factors Affecting Spatial-temporal Variation of Labile Organic Carbon Fractions by Biochar Driven in Mollisols Region of Northeast China

Biochar is widely used to improve soil physical properties and carbon sequestration. However, few studies focuse on the impact of maize stalk biochar on labile organic carbon(LOC) pool and the relationship between physical properties and LOC fractions. A field positioning experiment was performed in Mollisols region of Northeast China to evaluate the influence of maize stalk biochar on the spatial distribution and temporal changes of physical properties and LOC fractions. Maize stalk biochar treatments included C1(1.5 kg·hm^(-2)), C2(3 kg·hm^(-2)), C3(15 kg·hm^(-2)), C4(30 kg·hm^(-2)), and CK(0). The results showed that maize stalk biochar increased soil water contents(SWC) and soil porosity(SP), but reduced bulk density(BD). Maize stalk biochar reduced dissolved organic carbon(DOC) contents in the 0-20 cm soil layer, ranging from 0.25 g·kg^(-1) to 0.31 g·kg^(-1) in harvest period, while increased in the 20-40 cm soil layer. In addition, the application of biochar had a significant impact on the spatial distribution and temporal change of SWC, BD, SP, DOC, hot-water extractable carbon(HWC), acid hydrolyzed organic carbon(AHC Ⅰ, Ⅱ), and readily oxidized organic carbon(ROC). High amounts of maize stalk biochar up-regulated the contents of soil organic carbon SOC, HWC, AHC Ⅰ, AHC Ⅱ, and ROC. In addition, SWC and SP were the key physical factors to affect LOC fractions. In conclusions, maize stalk biochar could improve physical properties, and then influence LOC fractions, and maize stalk biochar could be used as an organic amendment for restoring degraded soils governed by their rates of addition.

Mollisols Properties and Changes in Ukraine and China

Soils are the foundation of civilizations and the basis for human food production.Mollisols in Ukraine and Northeast China are two out of the four major Mollisol regions in the world.The natural areas from which Mollisols developed are the prairies and steppes that experience temperate and freezing conditions.This review paper introduces the general climate,vegetation,and topography of Mollisols regions in Ukraine and Northeast China,analyzes their properties,including soil texture,soil organic matter content,soil bulk density,pH,cation exchange capacity and other chemical properties,and compares the property changes and management practices of Mollisols in relation to sustainable grain production.

Effects of Topography and Land Use Change on Gully Development in Typical Mollisol Region of Northeast China

Due to high intensity agricultural exploitation since the middle of the 20 th century, farmland gullies have become a pervasive form of water erosion in Northeast China. Yet few researches are concentrated on how topography and land use affect long-term gully development in this region. In this study, gully distribution in a village with an area of 24.2 km^2 in the central Mollisols area of Northeast China in different times were compared by Aerial photography(1968), Quickbird image(2009) and field survey, and factors affecting gully development including land use and topography were analyzed. The results showed that the total gully number decreased from 104 to 69, while occupying area rose from 34.8 ha to 78.4 ha from 1968 to 2009. Fundamental gully distribution had been formed by 1968 as most of 2009′s gullies were evolved from 1968′s gullies′ merge and width expansion process, and new gullies those initiated after 1968 occupied only 7% of total gully area in 2009. Gully area increasing ratio in grassland was the highest and that in forestland was the lowest. The threshold catchment area between simple and complex gully development was around 15 ha to 25 ha. This threshold value sets apart catchment areas that will develop simple or complex gullies in areas with similar environmental conditions. Gully control measurements were urgent because if appropriate gully control implements would not be applied, present gully erosion crisis could be doubled within 50 years.

Rainfall and inflow effects on soil erosion for hillslopes dominated by sheet erosion or rill erosion in the Chinese Mollisol region

Erosion agents and patterns profoundly affect hillslope soil loss characteristics. However, few attempts have been made to analyze the effects of rainfall and inflow on soil erosion for hillslopes dominated by sheet erosion or rill erosion in the Chinese Mollisol region. The objective of this study was to discuss the erosive agent(rainfall or inflow), hillslope erosion pattern(sheet erosion or rill erosion) and slope gradient effects on runoff and soil losses. Two soil pans(2.0 m long, 0.5 m wide and 0.5 m deep) with 5° and 10° slopes were subjected to rainfall(0 and 70 mm h–1) and inflow(0 and 70 mm h–1) experiments. Three experimental combinations of rainfall intensity(RI) and inflow rate(IR) were tested using the same water supply of 70 mm by controllingthe run time. A flat soil surface and a soil bed with a straight initial rill were prepared manually, and represented hillslopes dominated by sheet erosion and rill erosion, respectively. The results showed that soil losses had greater differences among treatments than total runoff. Soil losses decreased in the order of RI70+IR70 > RI70+IR0 > RI0+IR70. Additionally, soil losses for hillslopes dominated by rill erosion were 1.7-2.2 times greater at 5° and 2.5-6.9 times greater at 10° than those for hillslopes dominated by sheet erosion. The loss of <0.25 mm soil particles and aggregates varying from 47.72%-99.60% of the total soil loss played a dominant role in the sediment. Compared with sheet erosion hillslopes, rill erosion hillslopes selectively transported more microaggregates under a relatively stable rill development stage, but rills transported increasinglymore macroaggregates under an active rill development stage. In conclusion, eliminating raindrop impact on relatively gentle hillslopes and preventing rill development on relatively steep hillslopes would be useful measures to decrease soil erosion and soil degradation in the Mollisol region of northeastern China.

The Evolution of Organic Carbon in Chinese Mollisol Under Different Farming Systems: Validation and Prediction by Using Century Model

Soil organic carbon （SOC） is an important indicator of soil degradation process. In this study, the long-term SOC evolution in Chinese mollisol farmland was simulated and predicted by validating, analyzing, processing and assorting concerning data, based on clarifying parameters of Century model need, combined with best use of recorded data of field management, observed data of long-term experiments, climate, soil, and biology, and achieved results from Hailun Agro-Ecological Experimental Station, Chinese Academy of Sciences. The results were showed as follows： Before reclamation, SOC content was around 58.00 g kg^-1, SOC content dropped quickly in early years, and then decreased slowly after reclamation. SOC content was around 34.00 g kg^-1 with a yearly average rate of 8.91‰ decrease before long-term experiments was established. After a long-term experiment, SOC would change under different farming systems. Shift farming system changed as follows： By 20-year model simulation, SOC content decreased from 34.03 to 30.19 g kg^-1, with a yearly average rate of 5.97‰; by 100-year model simulation, SOC content decreased to 24.31 g kg^-1, with a yearly average rate of 3.36‰. Organic farming system changed as follows： By 20-year model simulation, SOC content decreased slowly from 34.03 to 33.39 g kg^-1, with a yearly average rate of 0.95‰, 5‰ less than that of shift farming system; by 100-year model simulation, SOC content decreased to 32.21 g kg^-1, with a yearly average rate of 0.55‰. ＂Petroleum＂ farming system changed as follows： By 20-year model simulation, SOC content decreased from 34.03 to 32.88 g kg^-1, with a yearly average rate of 1.72‰, much more than that of organic farming system; by 100-year model simulation, SOC content decreased to 30.89 g kg^-1, with a yearly average rate of 0.96‰. Combined ＂petroleum＂-organic farming system changed as follows： By 20-year model simulation, SOC content was increased slightly; by 100-year model simulation, SOC content increased from 34.03 to 34.41g kg^-1, with a yearly average rate of 0.11‰. The above results provided an optimal way for maintaining SOC in Chinese mollisol farmland： To increase, as much as possible within agro-ecosystem, soil organic matter returns such as crop stubble, crop litter, crop straw or stalk, and manure, besides applying chemical nitrogen and phosphorous, which increased system productivity and maintained SOC content as well. Also, the results provided a valuable methodology both for a study of CO2 sequestration capacity and for a target fertility determination in Chinese mollisol.

Soil Nutrient Variance by Slope Position in a Mollisol Farmland Area of Northeast China

In order to generate scientifically-based comparative information to improve fertilization efficiency and reduce nutrient loss, 610 samples of 122 soil profiles were collected at the 0–60 cm depth to compare soil nutrient contents including soil organic matter(SOM), total nitrogen(TN), total phosphorus(TP), available phosphorus(AP), and available potassium(AK) among different slope positions in a Mollisol farmland area of Northeast China. The contents of SOM and TN typically decreased with increased soil depth at back and bottom slope. Soil loss and deposition tended to decrease SOM and TN at the 0–20 cm soil depth on both the back slope and the slope bottom. The TP firstly decreased from 0–20 cm to 30–40 cm, and then not constantly increased at the back slope and the bottom slope. Due to the characteristics of soil nutrients and crop absorption, the contents of both AP and AK were typically the highest at the summit, followed by the slope bottom and the back slope in the 0–20 cm layer. Generally, in order to sustain the high soil productivity and protect the environment, attention should be paid to soil conservation on back slope; in addition, additional N and P fertilizer is necessary on the back slope.

Distribution,Properties,Land Use and Management of Mollisols in South America

Mollisols are common in South America. They cover about 8.87 × 107ha, 1.3 × 107ha and 4.3 × 106ha in Argentina, Uruguay and Southern Brazil respectively, which is 11.5% of the world total. Most of South American Mollisols were developed on Pleistocene and Holocene sediments and lie within the limits of the temperate zone, though the extreme north is bordering subtropical and the extreme south is within a cold-temperate zone. All suborders of Mollisols occur in Argentina, the most extensive being Udolls followed by Ustolls, whereas only Udolls, Aquolls and Albolls occur in Uruguay. Vertisols in Uruguay have many properties similar to Mollisols, and the occurrence of Vertisols is strongly associated with Mollisols. The Pampean Mollisols are a significant component of the global breadbasket of modem times. The main Argentine crops are wheat, corn, sorghum, barmy, soybeans and sunflower, while Mollisols in Uruguay remain mostly dedicated to cattle and sheep grazing though crop production has been increasing very rapidly in the last decade. Throughout South America, research has shown that Mollisols are experiencing losses of soil organic matter and nutrients, and degradation of physical properties after long cropping periods, resulting in soil scientists calling for increased conservation practices to reduce future losses and a deterioration of soil quality, and thus a more sustainable agriculture in the region.

Soil macroaggregates and organic-matter content regulate microbial communities and enzymatic activity in a Chinese Mollisol

The formation and turnover of macroaggregates are critical processes influencing the dynamics and stabilization of soil organic carbon(SOC).Soil aggregate size distribution is directly related to the makeup and activity of microbial communities.We incubated soils managed for>30 years as restored grassland(GL),farmland(FL)and bare fallow(BF)for 60 days using both intact and reduced aggregate size distributions(intact aggregate distribution(IAD)<6 mm;reduced aggregate distribution(RAD)<1 mm),in treatments with added glucose,alanine or inorganic N,to reveal activity and microbial community structure as a function of aggregate size and makeup.Over a 60-day incubation period,the highest phospholipid fatty acid(PLFA)abundance was on day 7 for bacteria and fungi,on day 15 for actinomycete.The majority of the variation in enzymatic activities was likely related to PLFA abundance.GL had higher microbial abundance and enzyme activity.Mechanically reducing macroaggregates(>0.25 mm)by 34.7%in GL soil with no substrate additions increased the abundance of PLFAs(average increase of 15.7%)and activities of β-glucosidase(increase of 17.4%)and N-acetyl-β-glucosaminidase(increase of 7.6%).The addition of C substrates increased PLFA abundance in FL and BF by averages of 18.8 and 33.4%,respectively,but not in GL soil.The results show that the effect of habitat destruction on microorganisms depends on the soil aggregates,due to a release of bioavailable C,and the addition of substrates for soils with limited nutrient availability.The protection of SOC is promoted by larger size soil aggregate structures that are important to different aggregate size classes in affecting soil C stabilization and microbial community structure and activity.

Influences of mechanized tillage and sowing modes on soil physical properties,soybean yield and economic benefits in mollisols region of Northeast China

Appropriate mechanized straw returning and tillage sowing techniques were effective means to optimize soil physical properties and enhance agricultural productivity,as well as important measures for the conservation and restoration of mollisols region in Northeast China.Under the condition of full-scale maize straw returning,four mechanized tillage and sowing modes were set,including plough tillage and sowing(PTS),combined tillage and sowing(CTS),no-tillage and sowing(NTS),and no-tillage and sowing with straw mulching(NTSM).In 2020 and 2021,the study investigated the effects of different mechanized tillage and sowing modes on soil physical properties,soybean yield and economic benefits.The results showed that during the pod-setting and pod-filling period of soybean,the NTS and NTSM treatments exhibited better effects on deep soil insulation and shallow soil moisture retention,the soil physical structure of PTS and CTS treatments were relatively ideal.Compared with PTS and CTS treatments,NTS and NTSM treatments significantly increased soil gravimetric water content(SWC)by 2.35%to 7.98%in the 5-15 cm soil layer and increased soil temperature(ST)by 3.94%to 10.42%in the 25-35 cm soil layer(p<0.05),significantly increased soil bulk density(SBD)by 2.98%to 6.72%and significantly reduced soil total porosity(STP)by 3.88%to 6.53%in the 5-25 cm soil layer,and significantly reduced soil gas phase ratio by 8.26%to 6.27%at the 15-25 cm soil layers,which caused soil three-phase ratio(STPR)of PTS and CTS treatment in 15-25 cm soil layer were relatively ideal.The soybean yield of NTSM treatment in 2020 was not significantly different from PTS and CTS treatment(p>0.05),the soybean yield of NTSM treatment in 2021 significantly increased by 7.30%and 5.84%over PTS and CTS treatments,respectively.And the average annual profit per unit area of NTSM treatment increased by 12.84%,12.41%and 8.57%compared with PTS,CTS and NTS treatments,respectively.Therefore,it was recommended to combine NTSM technique with PTS or CTS technique in a maize-soybean rotation system in mollisols region.The research results provided reference for the selection of appropriate mechanized tillage and sowing techniques in Northeast China’s mollisols region and had important guiding significance and practical value for the construction of rational plow layers and the implementation of conservation tillage.

Response of erosion reduction effect of typical soil and water conservation measures in cropland to rainfall and slope gradient changes and their applicable range in the Chinese Mollisols Region,Northeast China

Mollisols are rich in organic matter,which makes them suitable for cultivation and for enhancing global food security.Mollisols are experiencing severe soil erosion due to overfarming and a lack of mainte-nance.Thus,suitable soil and water conservation measures(SWCMs)are needed to protect Mollisols.However,how SWCMs respond to changes in slope gradient and rainfall and their effective application area remain ambiguous.Using a long-term field observation dataset,meta-analysis,and statistical test methods,we reveal the typical erosion reduction effect of SWCMs and their responses to changes in slope gradient and rainfall.Next,we calculated a coupling factor,P.S,by slope gradient and rainfall in flood season to determine the effective SWCMs application threshold.Compared with bare land,no-tillage(NT),contour ridge tillage(CT),ridge hedgerows(RH),and terraced fields(TF)had an average erosion reduction coefficient of 91.5%.There was a significant exponential increase in the correlation between P.S and the soil erosion amount in plots with typical measures.According to this correlation and soil loss tolerance(200 t/km^(2)),the upper limits of PS(NT:564 mm;CT:885 mm;RH:1135 mm)were determined and utilized to determine the effective application areas(NT:311.40103 km^(2);CT:320.86103 km^(2);RH:323.72103 km^(2))at the plot scale.In wet years,the applicable area of SWCMs declined toward the low-elevation foothills and flat terrain.All the results are applicable when slope length within 20 m.These results provide a basis for the precise allocation of SWCMs in Mollisols area and promote the scientific utilization of Mollisols resources.

Characterization of dissolved organic matter distribution in forestland and farmland of mollisol based on untargeted metabolomics

●Characterization of mollisol soil DOM by untargeted metabolomics is possible.●The polarity of the extractants determines the polarity of the extracted DOM.●Land use patterns affect the biological functions and co-network interaction of DOM.Mollisol soil is a major contributor to food production.Clarification of the molecular characteristics of dissolved organic matter(DOM)will contribute to the overall understanding and management of mollisol soil.However,the complexity of DOM poses a challenge to understanding its molecular characteristics.In this study,we investigated the molecular characteristics of DOM(<1000 Da)in mollisol soils with different soil use patterns(forestland and dryland)based on untargeted metabolomics.Here,we confirmed the feasibility of untargeted metabolomics for the molecular characterization of DOM in mollisol soils.DOM in forestland is mainly derived from plant metabolites,and DOM can perform more biological functions.However,DOM in dryland has complex composition and has powerful co-occurrence network interactions due to human activities.Water has better extraction efficiency for polar DOM,while organic reagents can efficiently extract lipid-like DOM,but the polarity of the extractant has less influence on the DOM than the soil physicochemical properties.Meanwhile,14-dihydroxyzeatin screened based on metabolomics can be used as a potential indicator for corn land.Therefore,untargeted metabolomics can be an effective method to characterize the DOM molecules of mollisol soil,which provides new insights for management of mollisol soil and sustainable agricultural development.

增温和秸秆还田对黑土农田土壤氮素有效性和N_2O通量的影响

土壤氮转化速率决定着土壤供氮能力,除受到温度的影响,还受到底物有效性的影响。然而,在农田生态系统中,关于土壤氮素有效性和N_2O通量对气候变暖和秸秆还田耦合的响应研究仍不足。本研究在东北黑土区进行增温和秸秆还田试验,采用离子交换树脂膜和静态暗箱法,原位监测0~20 cm土层土壤铵态氮、硝态氮有效性和氧化亚氮(N_2O)通量,探究增温和秸秆还田对农田黑土氮转化的影响。结果表明:增温、秸秆还田没有显著影响土壤氮有效性,但其在不同时期存在显著差异。秸秆还田显著增加了N_2O通量,且7月增温和秸秆还田处理对N_2O通量具有显著交互作用。在不增温条件下,秸秆还田使N_2O显著提升了109%;在增温条件下,秸秆还田使N_2O显著下降了2%。增温、秸秆还田和取样月份对N_2O通量也具有显著交互作用。研究结果有利于评估全球气候变暖背景下秸秆还田对农田生态系统氮周转的调控作用,对研究黑土氮循环过程具有重要参考价值。

降雨、汇流和坡度对黑土浅沟坡面侵蚀影响的试验研究

[目的]为研究降雨、汇流和坡度对浅沟侵蚀的影响,实施精确的水土保持措施。[方法]通过室内模拟降雨和汇流试验,设计2个降雨强度(50,100 mm/h)和2个坡度(3°,7°),并在4种降雨强度和坡度组合下设置5个依次增加的汇流强度(15,30,45,60,75 L/min),分析降雨、汇流和坡度及其交互作用对浅沟坡面侵蚀的影响,明确浅沟侵蚀对坡面侵蚀的贡献。[结果](1)坡度和汇流强度对浅沟坡面侵蚀的影响均大于降雨强度。当降雨强度由50 mm/h增加到100 mm/h时,3°和7°对应的坡面侵蚀量分别增加52.3%~81.8%和29.4%~88.4%;而当坡度从3°增大到7°,50,100 mm/h降雨强度对应的坡面侵蚀量分别增加114.3%~395.5%和130.0%~320.9%;当汇流强度由15 L/min增加至75 L/min,坡面侵蚀量增加4.6~13.5倍。同时,汇流强度的增加加剧坡度对坡面侵蚀的作用,而减弱降雨强度对坡面侵蚀的影响。(2)降雨、汇流、坡度双因子和三因子交互作用对浅沟坡面侵蚀的影响以汇流强度-坡度交互作用和降雨强度-汇流强度-坡度三者的交互作用的影响最大,其次为降雨强度-汇流强度交互作用,而以降雨强度-坡度的交互作用的影响最小。(3)不同试验条件下,浅沟侵蚀量占坡面侵蚀量的比例平均在85%以上,且其比例随汇流强度和坡度的增加呈增大趋势。(4)坡面侵蚀速率与水流流速、径流剪切力和水流功率之间均表现为极显著正相关,与阻力系数之间呈显著负相关;且坡面侵蚀速率与水流功率相关关系最优。[结论]研究结果为基于侵蚀动力因子和地形因子及其交互作用的浅沟侵蚀预测模型开发、浅沟侵蚀贡献分离和浅沟侵蚀机理研究提供了科学依据。

东北黑土区侵蚀农田土壤质量指数构建及其空间分异

侵蚀的空间异质性会改变土壤性质,导致土壤质量在空间分布上的差异。为明确中国东北侵蚀农田黑土土壤性质在不同空间位置上的分布规律,该研究基于纬度变化,从寒温带到中温带跨区选择了4个丘陵区(从北到南依次为九三、克山、海伦、宾县)的农田黑土坡面作为试验对象,划分了坡面位置(坡顶、坡上、坡中、坡下和坡底)和土壤深度(0~20 cm和>20~40 cm),分析了不同空间位置对侵蚀农田黑土土壤物理、化学和生物特征对不同空间位置的响应规律,并基于最小数据集(minimum data set,TDS)构建土壤质量指数(soil quality index,SQI-TDS),对侵蚀农田黑土土壤质量进行综合比较。研究表明,4个丘陵区黑土土壤性质在不同区域、坡位和土壤深度下的存在明显的空间变异(P<0.05)。全氮和有机碳含量随纬度升高而增加,且随坡位降低而逐渐减小,在坡底处增加。平均重量直径在九三最高,克山次之,海伦和宾县较小。土壤细颗粒在坡底沉积促进了新的团聚体形成,以致团聚体稳定性在坡面位置上表现为随坡位的降低呈先减小后增加的“V”型变化。SQI-MDS均值从北至南整体呈降低趋势,其中宾县的土壤质量指数最低,较其他3个地区显著降低22.66%~26.52%。在不同坡位上,SQI-MDS表现为以坡底、坡顶、坡上、坡中和坡下次序降低。该研究量化了东北侵蚀农田黑土土壤综合质量,结果可为侵蚀农田黑土修复和可持续发展提供科学依据。

基于稀土氧化物示踪法探究冻融循环对黑土团聚体周转的影响

为区分土壤团聚体形成和破碎过程,阐明冻融循环对黑土土壤结构的影响,本文利用稀土氧化物(REOs)示踪技术,通过室内模拟试验,探究不同初始含水量(50%田间持水量(T50)vs.100%田间持水量(T100))和冻融循环次数(0次、3次、6次、12次和20次)对团聚体粒径分布、平均质量直径(MWD)以及团聚体周转过程的影响。结果表明:同一初始含水量下,随着冻融循环次数的增加,MWD、>0.25mm和<0.053mm团聚体含量显著降低,0.25~0.053mm团聚体含量显著增加(P<0.05)。6次冻融循环后,T50处理下的MWD显著高于T100处理(P<0.05),5~2mm和<0.25mm团聚体含量无显著差异。除5~2mm团聚体外,冻融循环处理下,相邻粒级团聚体之间周转更为激烈。在同一冻融循环次数下,5~2 mm团聚体向0.25~0.053 mm团聚体的破碎量在T100处理下显著高于T50处理(P<0.05)。冻融循环促进了>0.25 mm团聚体的破碎和<0.053mm团聚体的团聚,表现为0.25~0.053mm团聚体的累积。冻融循环过程中,MWD与各粒径团聚体相对形成量呈显著正相关,与其相对破碎量呈显著负相关(P<0.05)。随着冻融循环次数的增加,各粒径团聚体周转时间显著增加(P<0.05)。同一冻融循环次数下,>0.25mm团聚体的周转时间高于<0.25mm团聚体,T100处理下的团聚体周转时间显著高于T50处理(P<0.05)。综上所述,冻融循环次数和土壤初始含水量通过影响团聚体形成和破碎过程改变土壤结构的稳定性。本研究结果可为进一步探究冻融循环下黑土土壤结构变化提供理论依据。

黑土物理特性变化及改善途径

东北黑土区位于世界四大黑土区之一,因其高肥力和有机质含量而闻名。作为我国主要的粮食生产基地之一,在保障国家粮食安全方面具有重要地位。然而,随着东北黑土地的开垦,养分的失调导致了黑土物理特性的变化和功能的退化,从而使得黑土肥力下降,威胁着该地区的粮食安全和生态安全。黑土物理特性发生变化,主要体现在黑土层土壤容重增加,孔隙度降低,水稳性团聚体减少,田间持水量下降等。采用合理的耕作方式和施肥制度能在不同程度上改善土壤物理特性,从而遏制土壤肥力的不断下降。本文总结了自黑土开垦以来土壤容重、水稳性团聚体、田间持水量和饱和导水率的变化,分析了耕作和有机物料等对土壤物理特性的重要调节作用,讨论了不同保护途径如何通过改善土壤物理特性达到提升土壤肥力的目的,最后从制定合理的耕作体系和有机培肥机制,优化作物种植模式等展望了未来黑土重点研究的方向。

一种改进的黑土农田风蚀集沙仪

风蚀监测可反映风沙运动规律,集沙仪是风蚀监测的必备仪器,而以往研究大多在沙漠或沙地开展,较少涉及黑土农田。本研究基于BSNE(Big Spring Number Eight)集沙仪,将采沙盒底部阻风结构中的18目孔径筛网改进为逆向百叶窗式的阻风挡板,采用模拟试验对比分析BSNE集沙仪和改进后rBSNE(Revised Spring Number Eight)集沙仪的保沙和集沙能力,并将其应用于野外黑土农田风蚀监测。研究结果表明:与BSNE集沙仪相比,rBSNE集沙仪降低了小粒级颗粒的损失率,当风速低于20 m·s^(-1)时,对<0.25 mm粒径的土壤颗粒的损失率显著降低74.3%~87.1%;当风速达到20 m·s^(-1)时,对所有试验粒径的土壤颗粒的损失率显著降低46.9%~74.3%。与BSNE集沙仪相比,rBSNE集沙仪有助于对小粒级颗粒的收集,当风速低于20 m·s^(-1)时,对粒径为<0.5 mm的集沙量显著增加了9.0%~44.0%;当风速达到20 m·s^(-1)时,对所有试验粒径的集沙量均显著增加7.3%~34.4%。野外监测结果显示风蚀输沙量随高度增加呈指数函数递减趋势,说明rBSNE集沙仪可应用于黑土农田风蚀的监测。

公路软土路基就地固化设计方案与处理效果分析

软土路基含水量高,压缩性较大,容易导致道路下沉,故软土路基处理是施工的重难点。分析了惠州市某公路施工的特征及要求,探讨了具体的设计方案及处理效果。结果表明,采用就地固化进行处理,施工过程更简单,缩短了工期,降低了固化成本,测试结果与预期偏差不大,提升了施工质量及工作效率,避免了环境污染问题,实现了绿色施工。

冻融作用对黑土坡面融雪、风力和降雨侵蚀的影响研究

[目的]研究冻融作用对东北黑土区坡面土壤侵蚀的影响,可加深对黑土坡面侵蚀过程机理的认识,并为区域侵蚀治理提供重要科学依据。[方法]以东北黑土区单一侵蚀营力驱动的融雪、风力和降雨侵蚀为对照,通过设计冻融-融雪、冻融-风力、冻融-降雨双侵蚀营力叠加的模拟试验,分析冻融作用对坡面融雪、风力和降雨侵蚀的影响。试验处理包括1次冻融作用、2个融雪径流量(1,2 L/min)、1个风速(12 m/s),1个降雨强度(100 mm/h)和1个坡度(3°)。[结果](1)冻融作用显著增加坡面融雪、风力和降雨侵蚀量(p<0.05)。与无冻融作用相比,1次冻融作用使坡面融雪侵蚀在1,2 L/min融雪径流下分别增加2042.9%和777.9%,使风蚀量和降雨侵蚀量分别增加118.0%和74.9%。(2)冻融作用对坡面水蚀(融雪和降雨侵蚀)过程的影响大于对径流过程的影响,且加剧坡面侵蚀过程,使坡面侵蚀活跃期历时增长和侵蚀强度增加;冻融作用也使风力侵蚀的输沙高度增加30%,各高度风蚀输沙量均增加50%以上。(3)冻融作用降低土壤抗侵蚀能力,其使表层土壤密度、土壤抗剪强度、土壤硬度分别显著减小2.5%,22.6%,15.0%。同时,冻融作用使水蚀过程中的坡面水流流速平均增加13.6%~25.0%,水流剪切力平均增加2.3%~81.9%,而阻力系数减小1.6%~20.6%,进而加剧坡面侵蚀过程。[结论]冻融作用改变侵蚀动力与阻力关系,加剧坡面融雪、风力和降雨侵蚀过程。

东北黑土区土壤侵蚀自然驱动因子时空分布特征

[目的]东北黑土区复合营力带来的土壤侵蚀作用明显,研究东北黑土区不同典型区间的土壤复合侵蚀自然驱动因子年内交替叠加情况,对于区域内土壤侵蚀治理具备现实意义。[方法]针对东北黑土区11个典型区域,利用气象及遥感等数据,通过分析对比不同区域水、风、冻、融作用自然驱动因子时空分布特征,阐明了各因子交替与叠加特点。[结果]在时间上,东北黑土区年内水力、风力、冻融、融雪作用驱动因子叠加交替出现,春季风力、冻融、融雪作用最为复杂,夏季以水力作用为主,秋季水力、风力、冻融复合作用有限,冬季风力、冻结作用明显。在空间上,水力驱动作用由东南向西北逐渐减小,风力作用由西南向东北逐渐减小,冻融作用由西南向东北逐渐减小,融雪作用呈现由西北向东南逐渐减小的趋势。根据侵蚀驱动因子分异特征将全区划分为水力、水力—融雪、水力—风力—冻融、水力—风力—融雪、水力—冻融—融雪侵蚀作用区。[结论]各营力表现出明显的时、空作用分异特点,根据自然驱动因子年内交替叠加情况得出了复合侵蚀驱动因子年内时空分布特征,为不同区域针对性土壤侵蚀治理、深化研究区复合侵蚀防控提供参考。