人为加速侵蚀对土壤退化的影响

应用人工降雨试验及野外小区观测资料,分析了人为加速侵蚀对土壤退化的影响。结果表明:植被破坏后,由于土壤侵蚀加剧,使土壤表层每年流失0.8cm左右;林草地在开垦的第一二年,土壤养分损失量较大;损失的养分大部分随土壤的流失而流失,使泥沙养分富集,泥沙中速效磷与土壤中速效磷富集化高达1.4～3.41;大量肥沃表土流失使土壤容重增大,土壤孔隙度下降,土壤平均入渗速度较林草地减少60%～70%;夏季土壤表层温度较林地升高10℃左右,使土壤水的损失加快,导致农作物旱情加重,环境质量变差。     

第18届国际土壤学大会综述

1 第18届国际土壤学大会组织系统 本届国际土壤学大会组织系统分4个部门,部门下分设专业委员会,具体组织结构如下：     

福建省侵蚀坡地的可持续利用

福建省25°以下的未开垦利用的侵蚀坡地,通过多年的开发与整治,不仅有效地控制了水土流失,且建立了水果生产基地。然而,在侵蚀坡地,尤其是在中、强度侵蚀坡地上开垦的果园,土壤肥力尚未得到改善,坡地生态系统仍然较脆弱。因此,在侵蚀坡地果园上必须通过套种绿肥（牧草）,以增加园面覆盖和生物归还量,促使土壤肥力的提高和环境条件的改善。研究证明,这是保证侵蚀坡地持续利用的一条根本出路。     

侵蚀对坡地小麦产量的影响

研究侵蚀与产量之间的关系应具备以下两个条件:(1)必须选择一块适宜的耕地,在可行的农业管理条件下测量侵蚀量。(2)必须测量所有可能与加剧侵蚀有关的因素。该研究以土壤流失量与剩余土壤中~(137)Cs含量的关系为依据,在相同的管理条件下估算以前的土壤侵蚀量平均值。这种方法排除了与非常规测量侵蚀量的关系,并且在很大程度上扩大了其适用范围。这份研究报告综合分析了麦地和谷地上壤中NO_3~-、HPO_4~(2-)、K~+、有机质含量、pH值、田间持水量、生育期、土层厚度和土壤侵蚀估算值之间的线性回归关系。该研究指出,在一定条件下侵蚀对生产率的永久性影响为——单位面积上每年流失量常用对数值的0.35%。     

天然降雨对红壤坡地侵蚀的影响

通过气象观测站与标准径流小区的试验观测,全面系统地分析了江西省红壤坡地的天然降雨特征。主要内容包括与土壤流失关系密切的降雨量(P)、降雨强度(I)等降雨特征参数的等级划分和时间分配规律;确定了江西红壤坡地侵蚀性降雨标准;确立了ΣE·I60 为红壤坡地降雨侵蚀力因子R的最佳计算组合,并分析了R值的季度分配、月分配特征以及雨量分配、雨强分配特征。这为探索控制江西红壤坡地水土流失的最佳时段,研究水土流失产生的动力来源以及发生演变的规律具有积极的借鉴意义     

控制坡地水力侵蚀危害的管理措施

根据坡面水力侵蚀由降雨击溅力和径流侵蚀力作用于坡面土壤,从而引起土壤颗粒的剪切破坏分离,被径流携带引起流失的作用机理,从植被覆盖、人工覆盖、消减径流量、减小径流流速、增强土壤抗分散、抗剪切能力等方面入手,采用适宜的生物、工程、耕作及化工产品综合措施,达到防止或减轻坡面侵蚀,保护土地生产力之目的。     

第18届国际土壤学大会的启示意义

简述18届国际土壤学大会的特点,讨论了大会对我国土壤学发展的一些启示意义。     

耕作侵蚀对农田坡地景观影响的研究进展

耕作侵蚀是农田坡地景观一种重要的土壤侵蚀过程.随着农业生产实践的强化,耕作侵蚀对农业环境的不利影响已经引起了全球关注.该文综述了近年来耕作侵蚀对坡地景观地形、土壤质量、土壤碳库及作物产量影响的研究成果,结合中国土壤侵蚀严重的西部地区探讨了耕作侵蚀引起的坡地景观格局、能流、物流变化及其对水体的危害,分析了耕作侵蚀对坡地景观影响的研究中存在的问题并提出了相应的展望.     

花岗岩侵蚀坡地重建植被的几个关键问题

本文在试验研究和调查基础上，对花岗岩坡地潜在不稳定特征和生态系统的恢复能力及临界点进行了讨论；重点对生植被过程中的地带性规律和植被演替规律问题进行了分析，提出了人工植被群落的发育过程必须与土壤肥力恢复程度相适应，注重草被生长，避免造成“空中绿化”。人工群落的配置以引进种与乡土树种结合，进行多层次混交为宜，着眼于建立地带性森林生态系统。     

中国滇池流域土地利用方式对土壤侵蚀和养分状况的影响

Soil erosion and loss of soil nutrients have been a crucial environment threat in Southwest China. The land use and its impact on soil qualities continue to be highlighted. The present study was conducted to compare soil erosion under four land use types(i.e.,forestland, abandoned farmland, tillage, and grassland) and their effects on soil organic carbon(SOC), total nitrogen(TN) and total phosphorus(TP) in the Shuanglong catchment of the Dianchi Lake watershed, China. There were large variations in the erosion rate and the nutrient distributions across the four land use types. The erosion rates estimated by137 Cs averaged 2 133 t km-2year-1under tillage and abandoned farmland over the erosion rate of non-cultivated sites, and the grasslands showed a net deposition. For all sites, the nutrient contents basically decreased with the soil depth. Compared with tillage and abandoned farmland, grassland had the highest SOC and TN contents within 0–40 cm soil layer, followed by forestland. The significant correlations between137 Cs, SOC and TN were observed. The nutrient loss caused by erosion in tillage was the highest. These results suggested that grassland and forestland would be beneficial for SOC and TN sequestration over a long-term period because of their ability to reduce the loss of nutrients by soil erosion. Our study demonstrated that reduction of nutrient loss in the red soil area could be made through well-managed vegetation restoration measures.     

中国亚热带地区土地退化的分布及评价－以福建省东溪流域为例

Some alternative mehods for estimating soil erosion rates rapily were used to elucidate the relationship between the land use types and land degradation.The ^137Cs content,magnetic susceptibility,aggregate stability,and soil properties were studied in the Dongxi River Basin, a mountainous area of ewstern Fujian, A plot of ^137Cs inventory(Y) against slope angle(X) shows a strong inverse log-log relationship(r=-0.83), indicating that muh more soil erosion occurs on steeper slopes.Average soil loss(in thickness of top soil per year) in the past 30 years for arable slope crest,arable slopes and tea plantation slopes are 1.6,10.4 and 8.0 mm year^-1 respectively,The surface layer enrichment factor of magnetic susceptibility(Y) in soil aslo shows an inverse log-log relationship (r=-0.63), indicating a similar tendency with the realtionship between the ^137Cs inventory(Y) against slope angle (X).The Physical and chemical properties of soils among different land use types show different degraded characteristics at different significant levles.     

利用137Cs估算土壤侵蚀速率的定量模型

A quantitative model was developed to relate the amount of ^137Cs loss from the soil profile to the rate of soil erosion,According th mass balance model,the depth distribution pattern of ^137Cs in the soil profile ,the radioactive decay of ^137Cs,sampling year and the difference of ^137Cs fallout amount among years were taken into consideration.By introducing typical depth distribution functions of ^137Cs into the model ,detailed equations for the model were got for different soil,The model shows that the rate of soil erosion is mainly controlled by the depth distrbution pattern of ^137Cs ,the year of sampling,and the percentage reduction in total ^137Cs,The relationship between the rate of soil loss and ^137Cs depletion i neither linear nor logarithmic,The depth distribution pattern of ^137Cs is a major factor for estimating the rate of soil loss,Soil erosion rate is directly related with the fraction of ^137Cs content near the soil surface. The influences of the radioactive decay of ^137Cs,sampling year and ^137Cs input fraction are not large compared with others.     

川中丘陵区土壤侵蚀对土壤特性和作物产量的影响

Roles of tillage erosion and water erosion in the development of within-field spatial variation of surface soil properties and soil degradation and their contributions to the reduction of crop yields were studied on three linear slopes in the Sichuan Basin, southwestern China. Tillage erosion was found to be the dominant erosion process at upper slope positions of each linear slope and on the whole short slope (20 m). On the long slope (110 m) and medium slope (40 m), water erosion was the dominant erosion process. Soil organic matter and soil nutrients in the tillage layer were significantly related to slope length and ¹³⁷Cs inventories on the long slope; however, there was no significant correlation among them on the short slope, suggesting that water erosion lowered soil quality by transporting SOM and surface soil nutrients selectively from the upper to lower slope positions, while tillage erosion transported soil materials unselectively. On the medium slope, SOM, total N, and available N in the tillage layer were correlated with slope length and the other properties were distributed evenly on the slope, indicating that water erosion on this slope was still the dominant soil redistribution process. Similar patterns were found for the responses of grain yield, aboveground biomass, and harvest index for slopes. These results indicated that tillage erosion was a major cause for soil degradation and grain yield reduction on the linear slopes because it resulted in displacement of the tillage layer soil required for maintaining soil quality and plant growth.     

Impacts of soil erosion on organic carbon and nutrient dynamics in an alpine grassland soil

The impact of soil erosion on the nutrient dynamics in alpine grassland soils is still an essential problem. Selecting a grass-covered hillslope in eastern Tibet Plateau, the cesium-137 (¹³⁷Cs) technique was used to determine the impacts of soil erosion on soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), and total potassium (TK). The ¹³⁷Cs data revealed that there were distinct soil redistribution patterns in different hillslope positions because of the influences of slope runoff, plant coverage and grazing activity. For the upper slope, soil erosion first decreased downward, followed by soil deposition in its lower part. In contrast, for middle and toe slopes, there was an increasing soil erosion along a downslope transect. Across the lower slope, soil erosion showed an irregular variation. Influenced by the selective transport of water erosion, SOC, TN and TP storage decreased with increasing soil erosion in upper, middle and toe slopes. In contrast, SOC, TN and TP storage varied little with soil erosion in the lower slope. On the whole hillslope, TK storage also varied little with soil erosion due to the large amount of potassium elements derived from soil parent materials. Particularly noteworthy was the greatest storage of SOC, TN and TP in the lower slope where most obvious net soil erosion occurred, which is closely related to the humus accumulation combined with gravel separation as well as weathering and pedogenesis of parent rocks induced by soil freeze-thaw.     

137Cs示踪分析东北黑土坡耕地土壤侵蚀对有机碳组分的影响

研究土壤侵蚀对有机碳不同组分流失的影响,可为科学评估土壤侵蚀在碳循环中的作用和探明农田有机碳变化机制提供理论依据.该研究以典型黑土区一凸型耕地坡面为研究对象,基于137Cs示踪技术,分析了坡面土壤侵蚀特征及强度分布,定量分析了坡面有机碳组分的变化幅度及侵蚀强度与有机碳组分间的关系.结果表明:研究坡面年均侵蚀速率为380...     

~(137)Cs示踪采煤沉陷坡土壤侵蚀及其对土壤养分的影响

为更好地理解矿区土壤退化机理,该文利用137Cs技术研究了焦作矿区具有15a沉陷历史的采煤沉陷坡土壤侵蚀特征及其对土壤养分的影响。沉陷坡137Cs含量从坡顶到下坡逐渐降低,及至坡脚急剧增大且表现出最高的值。基于137Cs本底(1 645 Bq/m2),沉陷坡坡顶至下坡表现为土壤侵蚀,而坡脚为土壤沉积。沉陷坡土壤侵蚀高达3.75 kg/(m2·a),属于中度侵蚀。沉陷坡土壤黏粒含量沿下坡方向增加,表明水蚀的分选性搬运。与对照区相比,沉陷坡侵蚀区土壤总有机碳(total organic carbon,TOC)、水溶性有机碳(water-soluble organic carbon,WSOC)、全氮、碱解氮、全磷、有效磷含量均出现了显著降低(P0.05);沉积区除WSOC显著降低(P0.05)外,其他养分含量变化不明显(P0.05)。在沉陷坡的侵蚀区,TOC与WSOC含量沿下坡方向逐渐减小,表现出与137Cs一致的分布格局;其他养分含量的坡面变化与137Cs分布不一致。相较于对照区,WSOC/TOC与碳氮比、碳磷比在沉陷坡侵蚀强烈的坡位分别出现了显著增大与降低(P0.05)。研究结果表明:1)焦作矿区自采煤沉陷坡形成以来发生了较严重的水蚀;2)侵蚀引起的土壤再分配影响沉陷坡土壤碳、氮、磷动态,其中,土壤再分配对土壤碳动态的影响最强;3)在土壤侵蚀作用下,采煤沉陷坡侵蚀强烈的坡位土壤有效态碳、氮、磷养分潜在的侵蚀风险大。采煤沉陷坡土壤侵蚀及其对土壤养分的不利影响应引起矿粮复合区土地整治的关注。     

Soil Redistribution investigations by combined use of soil 137Cs and selected chemical properties

Abstract

To improve the methods of application of phosphorus or supply of soil P to Azolla (A. microphylld), basal application, split application, inoculation of P-enriched Azolla, and soil disturbance were compared. Soil disturbance did not increase the floodwater P content. Phosphorus was applied to inoculum production plots to enrich Azolla with P. Thus, phosphorus-enriched Azolla could multiply 5–7 times after inoculation until it became P deficient. Trials on the methods of enrichment of Azolla with P showed that the best method was to broadcast twice 4.33 kg P (10 kg P₂O₅/ha) at 2-day intervals and to harvest Azolla 3 days after P application. Addition of P once or twice 2 weeks after the inoculation of P-enriched Azolla further increased the biomass production. Efficiency of P application was analyzed in terms of N gain in relation to the amount of P applied. This ratio in the P-enriched Azolla treatment was higher than the economically sound ratio -5-, and higher than or equal to that in the standard split application.     

紫色丘陵区小流域土壤侵蚀产沙空间分布的 137Cs法初步研究

该文通过紫色丘陵区响水滩小流域不同土地利用类型、不同坡度和坡长、不同地貌部位土壤剖面中 ¹³⁷Cs含量的测定与分析，对其侵蚀空间分布进行了估算。研究结果表明：该流域 ¹³⁷Cs含量的背景值为1870 Bq/m²；流域内坡耕地、林地的年平均侵蚀强度分别为4468、1759 t/(km²·a)；土壤侵蚀量与坡长、坡度均指数相关；丘顶、丘坡和鞍部的年平均侵蚀强度分别为2125、4676、3625 t/(km²·a)。结果表明土地利用类型、坡长和坡度、地貌部位对土壤侵蚀量影响很大，坡耕地是该流域泥沙的主要来源。     

东北黑土坡耕地土壤化学计量特征变化对侵蚀的响应

[目的] 探究土壤侵蚀对土壤养分含量及其化学计量比的影响,对于加深认识黑土区坡耕地质量退化过程及防控具有重要意义。[方法] 选择典型黑土区克山县开垦100多年的直形坡和开垦50多年的凸形坡为研究对象,根据¹³⁷Cs示踪技术估算坡耕地土壤侵蚀速率,定量分析土壤侵蚀与土壤有机碳(SOC)、全氮(TN)、全磷(TP)含量及生态化学计量比的关系。[结果] (1)利用¹³⁷Cs示踪法得到坡面整体的年平均侵蚀速率为4 428.56 t/(km²·a),直形坡和凸形坡侵蚀速率平均值分别为3 284.53,5 884.59 t/(km²·a),侵蚀总量分别为3.21×10⁵,2.94×10⁵ t/km²。(2)坡面整体碳氮比(C/N)与SOC呈极显著正相关(p<0.01),碳磷比(C/P)与SOC呈极显著正相关(p＜0.01),氮磷比(N/P)与TP呈极显著负相关(p＜0.01)。直形坡SOC、TN、C/N、C/P和N/P均极显著小于凸形坡养分含量和化学计量比值(p＜0.01),TP含量大于凸形坡TP含量(p＜0.01)。(3)坡面土壤侵蚀空间分布特征与土壤有机碳、全氮及全磷的空间分布具有一致性。坡面土壤侵蚀量与SOC、TN、TP、C/P均呈极显著负相关(p<0.01),与C/N呈显著负相关(p<0.05),与N/P呈负相关但相关性不显著(p>0.05)。[结论] 土壤侵蚀导致坡面土壤SOC、TN和TP在坡面再分布,影响土壤养分化学计量比,造成坡面养分流失严重。