允许土壤流失量与合理土壤流失量

 为确定防治农田土壤侵蚀的标准,20世纪中叶美国土壤学家首先提出了“允许土壤流失量”的概念,之后这一概念又延伸应用到流域和区域土壤侵蚀评价。“允许土壤流失量”的概念在全球,包括在中国得到了广泛的应用。随着土壤侵蚀及相关学科的发展,特别是全球变化研究的深入,可持续发展及健康河流理念的提出及水土保持实践中遇到的新挑战,“允许土壤流失量”的科学性和实用性方面存在的缺陷逐渐显现出来。本文在简要介绍“允许土壤流失量”由来的基础上,着重讨论“允许土壤流失量”存在的问题,并提出“合理土壤流失量”的概念及其确定的原则与方法。     

典型亚热带花岗岩地区森林流域岩石风化和土壤形成速率研究

岩石风化和土壤形成是地球表层物质循环的重要环节,了解岩石风化和土壤形成速率对土壤资源可持续利用和流域管理具有重要意义.本研究以位于我国亚热带的皖南花岗岩地区森林流域为例,通过野外监测其主要矿质元素输入输出量,应用流域中元素地球化学质量平衡原理,估算岩石风化和土壤形成速率.研究结果表明,在目前的降雨和酸沉降条件下,我国亚热带森林流域中,花岗岩的平均风化速率为0.696 t hm-2 a-1,土壤平均形成速率为0.598 t hm-2 a-1,所以需要经过2万年以上才能形成1 m厚的土壤.研究发现,大量输入土壤系统的H+由于被土壤风化和阳离子交换所消耗,径流水不至酸化,但是从长远来看,这会带来土壤的酸化.研究还表明根据当前的土壤形成速率,土壤允许流失量标准需要重新制定.     

自然侵蚀量和容许土壤流失量与水土流失治理标准

在总结分析国内有关自然侵蚀量、容许土壤流失量研究成果的基础上,探讨自然侵蚀量与容许土壤流失量的关系,讨论制订水土流失治理标准的思路。认为水土流失治理标准的确定有3个参考值：1）标准值,即一定条件下的容许土壤流失量,是水土流失治理至少要达到的目标,且随着对不同土地利用类型的功能需求与可实施的最佳水土保持措施、以及所在水土流失类型区的侵蚀危害与治理约束条件的不同而不同;2）理想值,即正常自然侵蚀状态下的土壤流失量;3）极端值,即土壤流失量为0,不发生水土流失。水土流失治理应是先控制到现时生态环境与社会经济条件下的容许土壤流失量范围内,逐步达到自然正常侵蚀量或制止水土流失的发生;还应引入环境伦理、环境美学及景观设计等理念,最终实现土地的可持续利用、区域生态系统的健康稳定及人与自然的和谐友好发展。     

Soil loss tolerance values for different physiographic regions of Central India

In India, a single soil loss tolerance ( T ) value of 11.2 Mg/ha is by default used for formulating land restoration strategies for all soil types, climates and vegetation covers. However, this single 'T' value does not represent a true picture of soil loss tolerance under all land uses. The objective of our study was to develop adjusted ' T ' values for Central India using soil infiltration rate, bulk density, total organic carbon, erodibility and soil pH. Soil state was defined using a quantitative model involving different soil functions which were used to convert soil parameters to a 0 to 1 scale. The normalized values were then multiplied by appropriate weighing factors based on relative importance and sensitivity analysis of each indicator. Based on overall assessment, each soil mapping unit was categorized into soil groups I, II or III. A general guideline of USDA – Natural Resource Conservation Service (USDA-NRCS) was followed to calculate soil loss tolerance for each soil group using effective soil depth. Adjusted ' T ' values for Central India ranged from 2.5 to 12.5 Mg/ha compared with a default value of 11.2 Mg/ha. Use of these values for soil mapping units will improve conservation planning and assist with planning the development of sustainable agriculture.     

Effects of two beet vinasse forms on soil physical properties and soil loss

Two beet vinasse forms (fresh (BV) and composted with a cotton gin crushed compost (CV)) have been applied for 4 years on a Typic Xerofluvent under dryland conditions near to Sevilla city (Guadalquivir River Valley, Andalusia, Spain) and their effect on soil physical, chemical and biological properties and their repercussion on soil loss was studied. BV and CV were applied at rates of 5000, 7500, and 10,000 kg ha^− 1 organic matter ha^− 1, respectively. The application of CV to the soil resulted in improved some soil properties and soil loss decreased. However, when BV was applied soil physical properties deteriorated and soil loss increased. We think that the high amounts of monovalent cations, particularly Na⁺, and of fulvic acids in BV destabilized soil structure. These results show that the addition of soil organic matter not always prevents soil loss, and they suggest the preferential use of composted beet vinasse versus fresh vinasse under dryland conditions.     

土壤容许流失量研究的进展与趋势

概述了国内外土壤容许流失量（Ｔ值）研究的历史、目前研究的现状和未来的发展趋势,对Ｔ值研究的主要内容如成土速度、土壤养分流失、泥沙淤积损失、土壤流失与土地生产力的关系、保护沟道侵蚀的重要性等做了讲述。介绍了Ｔ值的数学表达和不同国家的Ｔ值标准,阐述了进行Ｔ值双值性研究的必要性,并对Ｔ值研究中存在的问题进行了分析。     

施用土壤改良剂对磷素流失的影响研究

以滇池设施农业土壤和坡耕地土壤为研究对象,采用外源施用土壤改良剂（硫酸亚铁FES,硫酸铝ALS,聚丙烯酰胺PAM）和土壤消毒剂（五氯硝基苯PCNB）的办法,在不同解吸时间和解吸类型的条件下,研究了土壤改良剂对土壤解吸过滤液中总磷（TP）和可溶性总磷（TDP）的浓度变化影响。研究显示：无论是在连续解吸（2 ~ 10 h）的长时间情况下,还是在两种解吸类型（2 h强度解吸和6 h连续解吸）的情况下,除PCNB外,FES,ALS和PAM都可以显著降低两种土壤过滤液中TP浓度（p＜0.05）。并且发现FES和PAM在连续解吸情况下,对设施农业土壤过滤液中TDP浓度变化具有显著影响,且在两种解吸类型下,还可以均显著降低两种类型土壤中的TDP浓度。野外田间试验表明：施加改良剂后,径流雨水中TP和TDP值也得到明显降低,FES,ALS和PAM的施用对降低P素流失具有明显的效果。可见,无论从解吸持续时间、解吸类型还是土壤类型方面看,FES和PAM都具有显著的防控P素流失的效果,适宜在滇池流域设施农业和坡耕地等土壤中应用。     

影响土壤氮素径流流失的因素探析

从自然因素和人为因素出发探讨了地形、降雨、土壤理化性质、植被以及施肥、耕作制度等因素对土壤N素流失的影响,并综述了国内外有关研究的最新进展。并认为,基于这些因素相互作用的复杂性,有必要开展以下3方面的内容:一是大量开展多因子交叉实验,定量评价它们之间的关系,这为深入理解土壤N素流失机理和确定流域非点源污染模拟模型参数提供科学依据;二是加强有关土壤N素流失机理的多学科之间的联系,协同攻关建立较完善的理论认识;三是利用微观径流小区开展田间试验,结合遥感和GIS分析等方法,建立宏观大尺度土壤N素流失模型,为环境问题的宏观决策提供支持。     

Temperature tolerance in soil microarthropods: Simulation of forest-fire heating in the laboratory

Forest fires markedly reduce the abundance of surface-dwelling soil animals; animal densities also decline in soil layers underlying the char layer. The aim of the present study was to determine lethal temperatures for different species within the more abundant microarthropod groups in boreal forests, namely Collembola, Protura, Mesostigmata and Oribatida. In the laboratory, forest soil humus containing naturally occurring microarthropods was heated in plastic bags to avoid desiccation. Each sample was heated to one of 11 different temperatures between 20 and 60 °C for 1, 4, or 12 h. At the 1-h exposure, 36 °C was the highest temperature tolerated before significant decreases in numbers were detected. The corresponding temperatures after 4- and 12-h exposures were 34 °C for Oribatida and 30–32 °C for Collembola, Protura and Mesostigmata, respectively. Individual species responded differently, and the most heat-tolerant species within Oribatida was Tectocepheus velatus (40 °C at 4-h exposure) while Friesea mirabilis and Mesaphorura sp. (36 °C at 4-h exposure) were the most tolerant within Collembola. During a forest fire, temperatures higher than those tolerated by the investigated groups and species may well be reached.     

The assessment of soil loss by water erosion in China

Soil erosion is a major environmental problem in China. Planning for soil erosion control requires accurate soil erosion rate and spatial distribution information. The aim of this article is to present the methods and results of the national soil erosion survey of China completed in 2011. A multi-stage, unequal probability, systematic area sampling method was employed. A total of 32,948 sample units, which were either 0.2–3 km² small catchments or 1 km² grids, were investigated on site. Soil erosion rates were calculated with the Chinese Soil Loss Equation in 10 m by 10 m grids for each sample unit, along with the area of soil loss exceeding the soil loss tolerance and the proportion of area in excess of soil loss tolerance relative to the total land area of the sample units. Maps were created by using a spatial interpolation method at national, river basin, and provincial scales. Results showed that the calculated average soil erosion rate was 5 t ha⁻¹ yr⁻¹ in China, and was 18.2 t ha⁻¹ yr⁻¹ for sloped, cultivated cropland. Intensive soil erosion occurred on cropland, overgrazing grassland, and sparsely forested land. The proportions of soil loss tolerance exceedance areas of sample units were interpolated through the country in 250 m grids. The national average ratio was 13.5%, which represents the area of land in China that requires the implementation of soil conservation practices. These survey results and the maps provide the basic information for national conservation planning and policymaking.     

黄土高原生态环境建设关键性问题的研讨

该文以学习贯彻中央领导“治理水土流失,建设生态农业”的批示为基础,研讨有关的科学技术问题,以生态环境演变为主导,论证了自然侵蚀和人为加速侵蚀的发生发展过程及其调控的基本原理。以生态环境建设系统工程为目标,研讨了治理水土流失,侵蚀环境调控,农田建设,水利建设及防止新的人为加速侵蚀等,提出了应强化研究的关键性和基本规律性的科学技术问题。     

东北典型黑土区农耕土壤团聚体流失特征

通过野外原位模拟降雨试验,研究了东北典型黑土区3种降雨强度(30、60和90 mm h-1)下农耕地坡面侵蚀过程的土壤团聚体流失特征,分析了流失团聚体特征指标(平均重量直径(MWD)、几何平均直径(GMD)、分形维数(D)、平均重量比表面积(MWSSA)、≥1 mm粒级团聚体比例(PA1)、≥2 mm粒级团聚体比例(PA2)、≥0.25 mm粒级团聚体比例(PA0.25))的变化规律。结果表明:降雨强度对典型黑土区农耕地坡面侵蚀有显著影响;次降雨初期侵蚀量占整个降雨过程总侵蚀量的比例随着降雨强度的增加而增大。在30 mm h-1降雨强度下,团聚体流失以0.25 mm粒级团聚体为主,其占团聚体流失总量的90.0%;在60 mm h-1降雨强度下,团聚体流失以0.25和0.5~1 mm粒级团聚体为主,二者占团聚体流失总量的63.7%;而90 mm h-1降雨强度下,团聚体流失以0.25和2~5 mm粒级团聚体为主,二者分别占团聚体流失总量的31.7%和31.2%。PA0.25、PA1、PA2、MWD和GMD与降雨强度和含沙量之间均呈现极显著正相关关系;MWSSA和D与降雨强度和含沙量之间呈现极显著负相关关系。研究结果还表明,PA1、MWD和GMD皆能较好地表征典型黑土区农耕土壤的团聚体流失特征。     

Effects of soil erosion on long-term soil productivity in the black soil region of northeastern China

China's northeastern Black Soil Region, one of the country's most important crop production areas, has been seriously affected by soil erosion. This study evaluated the effects of soil erosion on the long-term productivity of this region. We used a modified productivity index (MPI) model (MPI is a number between 0 and 1, with 1 indicating highest productivity) to assess the current effects of soil erosion on soil productivity, as well as to predict long-term change in productivity. Samples from 21 black soil profiles yielded varying MPI values, although most MPI values were indicative of moderate productivity. Organic matter content and available water capacity impact MPI values in the region, whereas soil clay content and pH were less important. Overall, organic matter content and available water capacity of soil profiles decreased consistently as depth of erosion increased. Modeling indicated that MPI in the region will decrease by 0.0052 for each centimeter of topsoil eroded; this rate represents 1% of the current average MPI for the study area. The model predicts a 9.6% productivity reduction over 100 years and a 48.3% reduction over 500 years.     

非表层剖面层次土壤生产力评价研究

研究了盆栽条件下4个非表层土壤剖面层次(AB,Ab,Bk,Bg)土壤在3种肥料处理下对“京绿2号”小白菜根系发育和养分水分吸收的影响,并评价了其生长障碍因子。结果表明,各处理出苗无明显差异;施加尿素和磷二铵有利于干物质积累量增加,且磷二铵的效应更显著;施磷二铵处理的根冠比明显低于不施肥处理和施尿素处理;施加尿素和磷二铵后作物含N量增加;施加磷二铵后各土壤剖面层次土壤中的植株P浓度明显提高。综合分析表明,正常情况下只要补充N肥和P肥,作物耕层以下的各土壤剖面层次对作物生长并无明显的阻碍作用,且通过适当的耕作和灌溉,可使非耕层土壤生产力状况得到改善。     

The challenge of soil loss control and vegetation restoration in the karst area of southwestern China

Soil loss, both from surface soil loss and subsurface soil leakage, in the karst regions of southwestern China is a serious environmental problem that threatens sustainability in that region. The surface soil loss has been extensively studied, and many studies have been conducted to investigate the causes, impacts and mechanisms involved, but the study of subsurface soil leakage has received little attention due to the difficulties in studying the natural conditions. There is no consensus on the overall proportions between surface soil loss and subsurface soil leakage. To control soil loss, improve ecological restoration, and help locals out of poverty, the Chinese government carried out a series of ecological restoration projects in the karst regions of southwestern China starting in the 1980s. As a result, the intensity and areal extent of soil loss continues to decrease and the ecological situation is steadily improving. However, because of the fragile ecosystem in the karst regions, the soil loss control is a long-term task, and the soil loss in some karst regions continues to be a problem. Subsequently, we put forward some suggestions for the policy makers relative to conservation of soil loss and vegetation restoration. These suggestions include: (1) government, private organizations and individuals are encouraged to raise funds for soil loss control and vegetation restoration; (2) nature reserves should be established to increase biodiversity; (3) engineering projects such as small reservoirs, ponds, and flow diversion channels should be constructed in marginal karst regions.     

A comparison of mineral-magnetic and distributed RUSLE modeling in the assessment of soil loss on a southeastern U.S. cropland

As geospatial technologies increasingly figure into resource management activities, there is a corresponding need to provide commensurately detailed high resolution spatial data. This study addresses the capacity of rapidly and cheaply acquired mineral-magnetic data to provide detailed spatially distributed assessments of long-term cumulative soil loss from agricultural fields. Model output from a simple distributed implementation of the Revised Universal Soil Loss Equation (RUSLE) and from a field-data-oriented soil magnetism-based erosion model are compared for a small Alabama (USA) farm lot. An undisturbed reference soil toposequence is used as input to the magnetism model, in contrast with earlier studies that relied on a single reference soil profile. Results from this procedure, while likely to be more dependable, proved primarily to further emphasize spatial patterns noted in prior studies. In addition, the use of a toposequence decreased the area over which RUSLE and magnetism models were in agreement. RUSLE underpredicted denudation relative to magnetism-model results over upper slopes, and overpredicted it on lower slopes. The locations of former access roads may explain underprediction on the upper slopes. The differences between the two method outcomes are discussed with regard to the potential for spatial variability in parent materials, the efficacies of non-fluvial soil redistribution processes, and the availability of detailed land use records for the 100+ years of agricultural activities at the site.     

Using plot soil loss distribution for soil conservation design

Soil conservation design is generally based on the estimation of average annual soil loss but it should be developed taking into account storms of a given return period. However, use of frequency analysis in soil erosion studies is relatively limited. In this paper, an investigation on statistical distribution of soil loss measurements was firstly carried out using a relatively high number of simultaneously operating plots of different lengths, λ (11, 22, 33 and 44 m) at the experimental station of Sparacia (southern Italy). Using a simple normalization technique, the analysis showed that the probability distribution of the normalized soil loss is independent of both the scale length λ and the temporal scale, which are completely represented by the mean soil loss calculated for a given event using all replicated data collected in plots having the same length. Then, a comparison between the frequency distribution of soil loss and rainfall erosivity index of the USLE was carried out. An estimating criterion of the annual soil loss of a given return period was also developed. By this criterion, the frequency distribution of the rainfall erosivity factor can be used to design soil conservation practices.     

Pollution-induced tolerance of soil bacterial communities in meadow and forest ecosystems polluted with heavy metals

Pollution-induced community tolerance (PICT) allows finding a cause–effect relationship between pollution and adverse changes in a community. In our previous study we found that functional diversity of bacterial communities decreased significantly with increasing metal concentration, in both forest humus and meadow topsoil. Thus, the aim of the present study was to test whether tolerance of soil bacterial communities had increased as an effect of long-term metal pollution. Bacterial tolerance was tested with the use of the Biolog^® ECO plates in soils originating from the most polluted and the least polluted sites from three forest and five meadow transects located near smelters in Avonmouth (England), Clydach (Wales), and Głogów and Olkusz (Poland). We found that tolerance of bacterial communities was significantly increased in polluted meadow soils when compared to control meadow soils. On the contrary, no increase in tolerance was detected in polluted forest humus.     

Carbon loss by sclerotia of Sclerotium rolfsii under the influence of soil pH,temperature and matric potential and its effect on sclerotial germination and virulence

Germinability and virulence of sclerotia of Sclerotium rolfsii were assessed after 50 days of exposure of ¹⁴C-labeled sclerotia to soil at 0, −5 and −15 kPa and pH 6.9, or to soil at 15, 25 or 30 °C, pH 5 or 8 and −1 kPa. Evolution of ¹⁴CO₂ accounted for the greatest share of endogenous carbon loss from sclerotia under all soil conditions, except in water-saturated soil (0 kPa), in which sclerotial exudates contributed the major share of carbon loss. Total evolution of ¹⁴CO₂ from sclerotia in soil at −15 kPa (42.4% of total ¹⁴C) and at −5 kPa (38%) was significantly higher than at 0 kPa (23.8%). Evolution of ¹⁴CO₂ in soil at 25 or 30 °C was more rapid than at 15 °C with regardless of pH. Loss of endogenous carbon by sclerotia was the greater after 50 days of exposure to soil at 0 kPa, or at 25 or 30 °C and pH 8, than at other soil conditions. Sclerotia exposed to water-saturated soil (0 kPa) showed a more rapid decline in nutrient independent germinability, viability and virulence, than to those exposed to −5 or −15 kPa. Sclerotia became dependent on nutrient for germination and lost viability and virulence within 30–40 days in soil at 25 or 30 °C, pH 8. However, more than 60% of sclerotia retained viability in soil at 15 °C regardless of pH, even after 50 days. Radish shoot growth was increased significantly by the sclerotia that had been exposed to soil at 0 kPa, or to soil at 25 or 30 °C and pH 8 for 50 days. In conclusion, carbon loss by sclerotia during incubation on soil at different pH levels, temperatures and water potentials was inversely correlated with sclerotial ability to infect radish seedlings. The relationship between carbon loss by sclerotia and radish shoot length was positive.     

湖南省水土流失治理探究

本文通过调查研究, 分析了湖南省水土流失现状、危害和发展趋势, 以及水土流失原因。全省水土流失的县市从50年代的34个增加到87个;年入洞庭湖泥沙量增加34.2%。 30多年来洞庭湖泥沙淤积总量达40亿m³, 直接危害农、林、牧、渔等业的生产。 指出: ①加强植被建设,改造坡耕地;②推广小流域综合治理;③户包或联户承包治理;④开展多渠道集资, 增加水土保持经费;⑤完善治理和管理政策, 加强水土保持方针、政策等的宣传。