Review and prospect of soil compound erosion

Soil erosion is one of the most serious environmental issues constraining the sustainable development of human society and economies.Soil compound erosion is the result of the alternation or interaction between two or more erosion forces.In recent years,fluctuations and extreme changes in climatic factors(air temperature,precipitation,wind speed,etc.)have led to an increase in the intensity and extent of compound erosion,which is increasingly considered in soil erosion research.First,depending on the involvement of gravity,compound erosion process can be divided into compound erosion with and without gravity.We systematically summarized the research on the mechanisms and processes of alternating or interacting soil erosion forces(wind,water,and freeze-thaw)considering different combinations,combed the characteristics of compound erosion in three typical regions,namely,high-elevation areas,high-latitude areas,and dry and wet transition regions,and reviewed soil compound erosion research methods,such as station observations,simulation experiments,prediction models,and artificial neural networks.The soil erosion model of wind,water,and freeze-thaw interaction is the most significant method for quantifying and predicting compound erosion.Furthermore,it is proposed that there are several issues such as unclear internal mechanisms,lack of comprehensive prediction models,and insufficient scale conversion methods in soil compound erosion research.It is also suggested that future soil compound erosion mechanism research should prioritize the coupling of compound erosion forces and climate change.

Wind tunnel simulation of the effects of freeze–thaw cycles on soil erosion in the Qinghai–Tibet Plateau

Intense freezing and thawing actions occur in the Qinghai-Tibet Plateau because of its high elevation and cold temperature. The plateau＇s unique environment makes it easy to generate wind erosion under dry, windy weather conditions, resulting in the emergence ofdesertification. As a major form of freeze-thaw erosion, freeze-thaw and wind erosion is displayed prominently on the Qinghai-Tibet Plateau. Therefore, in this study, soil samples were collected from the surface of the plateau to undergo freeze-thaw and wind erosion simulation experiments. Results show that wind erosion strength increases with an increasing number of freeze-thaw cycles, water content in the freezing-thawing process, and the difference in freeze-thaw temperatures. Therefore, in the conditions of water participation, the main reason for the freeze-thaw and wind erosion in the Qinghai-Tibet Plateau is the damage to the soil structure by repeated, fierce freeze-thaw actions, and the sand-bearing wind is the main driving force for this process. The research results have theoretical significance for exploring the formation mechanism of freeze-thaw and wind erosion in the Qinghai-Tibet Plateau, and provide a scientific basis for freeze-thaw desertification control in the plateau.

黄土高原水蚀风蚀交错带水分和密度对人工草地土壤呼吸的影响

为研究黄土高原水蚀风蚀交错带不同水分与密度处理的人工苜蓿和沙打旺草地土壤呼吸特征,分析了人工草地土壤呼吸对水分和密度的响应及其与环境因子的关系。结果表明:水分增加能够显著促进黄土高原水蚀风蚀交错带人工草地土壤呼吸速率(P<0.01),土壤呼吸对不同密度处理的响应特征因草地植被类型不同而异,土壤呼吸速率的季节变化对水分增加和密度响应不敏感。土壤水分是土壤呼吸的限制因子,土壤温度与土壤呼吸速率在6-7月份(旱季后期)相关性不明显,8月份后(雨季)相关性增强。土壤呼吸与表层土壤水分和温度有着显著的耦合关系,加水减弱了苜蓿草地土壤呼吸对水分和温度的依赖,而未改变沙打旺草地土壤呼吸对表层土壤水分和温度的依赖。

风蚀水蚀交错区生态经济耦合效应

研究风蚀水蚀交错区退耕还林还草、坡改梯和淤地坝建设等综合土地利用变化的生态经济耦合效应,为保障生态经济协调发展提供一定的理论基础。以位于陕北风蚀水蚀区的府谷县为研究对象,采用生态经济耦合指数分析了土地利用变化的内生效应,通过土地利用结构及景观指数的变化分析土地利用变化的外延效应,从内生和外延两方面定量对比分析陕北风蚀水蚀交错区生态经济耦合效应。研究表明府谷县从2000—2013年实现了耕地向林地和草地的转化,景观类型的丰富程度和均匀程度上升,土壤侵蚀量明显减少,生态经济耦合指数从2000年的215.88 t/万元减少到2013年的130.59 t/万元。生态经济耦合指数敏感性分析表明府谷县梯田和坡耕地的变化对生态经济耦合指数的影响显著大于水浇地与坝地的影响。退耕还林还草、坡改梯和淤地坝建设等政策的执行不仅让府谷县生态环境得到改善,还使其经济耦合内部呈现增益。

裸露地表土壤风蚀及其电场数值模拟

土壤风蚀及电场机理研究是认识其灾害本质,进而实现有效防治的基础。采用颗粒流体动力学方法,建立裸露地表土壤风蚀的气-固耦合模型,并基于水的电离理论,建立了运动土壤颗粒碰撞带电模型。数值计算结果不仅从理论上再现了裸露地表土壤风蚀的发生、发展及达到动态稳定的过程,而且定量分析了土壤风蚀过程颗粒的带电特性及其产生的风蚀电场。在风-颗粒相互耦合作用下,裸露地表土壤颗粒的风蚀过程最终达到动态稳定,土壤风蚀量随高度呈指数规律递减,且贴近地表层风蚀量较大。土壤颗粒在运动中的碰撞使得颗粒发生带电现象,粒径较大颗粒带正电,粒径较小颗粒带负电;由带电土壤颗粒产生的风蚀电场强度随高度减小,且在风蚀过程中逐渐增强,在风蚀达到动态平衡时风蚀电场趋于稳定。本文综合考虑了风-土壤-电场的土壤风蚀过程,这将为建立更加符合实际、较为全面的土壤风蚀模型提供理论基础。

Climate change indirectly enhances sandstorm prevention services by altering ecosystem patterns on the Qinghai-Tibet Plateau

Climate change influences both ecosystems and ecosystem services.The impacts of climate change on ecosystems and ecosystem services have been separately documented.However,it is less well known how ecosystem changes driven by climate change will influence ecosystem services,especially in climate-sensitive regions.Here,we analyzed future climate trends between 2040 and 2100 under four Shared Socioeconomic Pathway(SSP) scenarios(SSP1-2.6,SSP2-4.5,SSP3-7.0,and SSP5-8.5) from the Coupled Model Intercomparison Project 6(CMIP6).We quantified their impacts on ecosystems patterns and on the ecosystem service of sandstorm prevention on the Qinghai-Tibet Plateau(QTP),one of the most climate-sensitive regions in the world,using Random Forest model(RF) and Revised Wind Erosion Equation(RWEQ).Strong warming(0.04℃/yr) and wetting(0.65 mm/yr) trends were projected from 2015 to 2100.Under these trends,there will be increased interspersion in the pattern of grassland and sparse vegetation with meadow and swamp vegetation,although their overall area will remain similar,while the areas of shrub and needleleaved forest classes will increase and move toward higher altitudes.Driven by the changes in ecosystem patterns caused by climate change indirectly,grassland will play an irreplaceable role in providing sandstorm prevention services,and sandstorm prevention services will increase gradually from 2040 to 2100(1.059-1.070 billion tons) on the QTP.However,some areas show a risk of deterioration in the future and these should be the focus of ecological rehabilitation.Our research helps to understand the cascading relationship among climate change,ecosystem patterns and ecosystem services,which provides important spatio-temporal information for future ecosystem service management.

天然浮石混凝土耐久性能研究进展

浮石是一种由岩浆急速冷凝而成的多孔隙轻质岩石,以其为骨料制成的天然浮石混凝土具有质轻、隔音、保温等优点。通过对天然浮石混凝土及普通混凝土在风沙吹蚀、冻融、盐类侵蚀及多因素耦合状态下破坏形态的对比及相关参数的量化分析,对天然浮石混凝土的耐久性进行了评述,可为其在轻质墙板领域的研发及应用提供参考。

NaOH改善粉煤灰混凝土微结构及抗风蚀-冻融耐久性能

为改善水工混凝土风蚀-冻融耐久性能,提高固废粉煤灰的利用率,选择NaOH碱性激发剂制备加碱粉煤灰混凝土。通过红外光谱试验、核磁共振试验、室内冻融和风蚀-冻融试验研究常温养护下加碱粉煤灰混凝土反应产物、孔隙特征及抗冻、抗风蚀-冻融耐久性劣化规律。结果表明:常温掺加质量分数为5%的NaOH有利于激发粉煤灰活性,提高其对水泥的替代率;加碱后红外光谱中粉煤灰玻璃体的特征峰消失,出现了N-A-S-H凝胶的典型特征峰且凝胶聚合度更高;核磁共振中相应的T2谱起始弛豫时间和谱面积均减小,孔结构更优;粉煤灰替代率为40%,NaOH质量分数为5%时混凝土的孔隙结构优于粉煤灰替代率为20%的普通混凝土。以相对动弹性模量为指标,建立加碱粉煤灰混凝土耐久性指标的优化残差-马尔可夫(Markov)模型并对其服役寿命进行预测,相对误差在5%左右,证实了常温条件外加碱性激发剂有助于提高粉煤灰在胶凝材料中的使用率,改善混凝土的抗风蚀-冻融耐久性能,为风蚀严寒区绿色水工混凝土的开发、推广提供理论支撑。

半干旱区植被风沙动力过程耦合研究:Ⅱ.模拟

以我国北方半干旱区典型自然条件为模型输入参数,对生物量和风蚀量的动态变化和空间分布进行了模拟。模拟的主要影响因素有降水量、气温、土壤类型和风况等。模拟结果表明:生物量随着降水量的增加和气温的升高而增大,风蚀量随着大风日数和风速的增加而增大。随着半干旱区降水和气温的季节变化,生物量在初春最低、夏末最高;风蚀量则在春季最大、夏季最小。生物量和风蚀量有明显的相互影响,生物量的增加能够有效降低风蚀量。在不受其他因素影响时,生物量与降水量在空间上的分布呈现出一致性,在考虑气温因素后生物量的重心向气温较高处偏移。小幅度的地形变化对生物总量和风蚀总量的大小影响不大,但明显改变了它们的空间分布格局。

黄河内蒙古段支流“十大孔兑”侵蚀产沙的时空变化及其成因

"十大孔兑"来沙造成黄河干流强烈淤积。为了通过流域治理来减轻泥沙灾害,研究"十大孔兑"侵蚀产沙过程具有重要意义。基于1960—2005年的河流输沙量、径流量和降雨量资料,运用统计方法进行了研究。结果表明:"十大孔兑"输沙量高度集中于几个大水大沙年份,其余年份对46年总输沙量的贡献很小。最大1年、最大3年、最大5年和最大10年的累积输沙量分别占到46年总输沙量的21.26%、37.18%、47.92%和69.29%。1960—1991年和1992—2005年两个时段相比,后一时段输沙量年均值减少了37%。这一差异可以用暴雨特征的差异和下垫面(如植被)的变化来解释。1991年以后,年降水量无明显变化,但最大1日降雨量在p<0.10的水平上呈现减小的趋势。虽然20世纪90年代西柳沟并未大规模实施水土保持治理,但由于农村富余劳动力转移,对土地的压力减轻,对植被的破坏大大减弱,使得植被逐渐恢复,NDVI呈增大趋势,因而侵蚀产沙减弱。"十大孔兑"产沙模数具有明显的空间分异特征,从西向东增大,在西柳沟达到最大值,然后再减小。流域自然地理因素具有明显的变化,从西向东,沙尘暴频率减小,降雨量增大。沙丘类型也发生了变化,由以流动沙丘为主变为以半固定沙丘为主,进入河道风沙的输沙强度减小。另一方面,水力驱动的侵蚀和泥沙输移从西向东增强。上述两种作用叠加的结果,在区域中部西柳沟附近出现了侵蚀产沙的峰值区。