氨固定对土壤微生物生物量氮矿化测定的影响

Two soils with relatively high(Soil 1)and low(Soil 2) ammonium fixation capacities were used in this study to examiune the effect of ammonium fixation on the determination of N mineralized from soil microbial biomass.Organism suspension was quantitatively introduced to Soil 1 at various rates.Both fumigation-incubation (FI) and fumigation-extraction (FE) methods were used to treat the soil.The amount of fixed NH4^ increased with increasing rate of organism-N addition.A close correlation was found between the amount of fixed ammonium and th rate of organism-m addition.The net increases of fixed NH4^ -N were equivalent to 38% and 12% of the added organism-N for FI and FE treatments,rspectively,in this specific soil.To provide isotopic evidence,^15N-labelled organism-N was added to Soils 1 and 2 at 121.4 mg N kg^-1.In FI treatment,22 and 3mg N kg^-1 of labelled N were found in the fraction of fixed NH4^ -N in Soile 1 and 2 respectively;while in FE treatment,9 mg N kg^-1 of labelled N was found in the fraction of fixed NH4^ -N in Soil 1 only.There was no labelled N in the fraction of fixed NH4^ -N in Soil 2.In all of the unfumigated (check) soils,there was little or no labelled N in the fixed fractions,probably because the organism-N added was easily mineralized and nitrified.A mean of 0.64 for KN value,the fraction of N mineralized in the killed microbial biomass,as obtained with inclusion of the net increase of fixed NH4^ -N,The corresponding value calculated with exclusion of the net increase of ficed NH4^ -N was 0.46 ,It was concluded that ammonium fixation was a problem in deterination of KN,particularly for soils with a high ammonium fixation capacity, Results also showed that microbial biomass N measurement by FFE method was less affected by ammonium process than that by FI method.     

川中丘陵区人工刨地耕作方式下紫色土坡耕地侵蚀速率的137Cs和210Pbex双核素示踪法研究

Purple soils are widely distributed in the Sichuan Hilly Basin and are highly susceptible to erosion, especially on the cultivated slopes. Quantitative assessment of the erosion rates is, however, difficult due to small size of the plots of the manually-tilled land, the complex land use, and steep hillslopes. 137Cs and 210Pbex (excess 210Pb) tracing techniques were used to investigate the spatial pattern of soil erosion rates associated with slope-land under hoe tillage in Neijiang of the Sichuan Hilly Basin. The 137Cs and 210Pbex inventories at the top of the cultivated slope were extremely low, and the highest inventories were found at the bottom of the cultivated slope. By combining the erosion rates estimates provided by both 137Cs and 210Pbex measurements, the weighted mean net soil loss from the study slope was estimated to be 3100 t km-2 year-1, which was significantly less than 6930 t km-2 year-1 reported for runoff plots on a 10°cultivated slope at the Suining Station of soil Erosion. The spatial pattern of soil erosion rates on the steep agricultural land showed that hoe tillage played an important role in soil redistribution along the slope. Also, traditional farming practices had a significant role in reducing soil loss, leading to a lower net erosion rate for the field.     

利用遥感和GIS研究兴国县土壤侵蚀的变化

The spatial and temporal dynamics of soil erosion in Xingguo County, Jiangxi Province, China were studied using multi-period remote sensing images and GIS. The results indicated that the soil erosion status of the region has been improving, particularly since the 1980s, with the erosion rate showing an evident decline over the past 30 years. The improvement showed not only in the decline of eroded soil area, but also with the reduction in the extent of erosion. The extent of erosion mainly changed by one level, and the change primarily occurred with the severely or moderately eroded soil types. However, in general, soil erosion was still an overriding problem in the region with some areas becoming more serious, especially those with large quantities of granite.     

我国西北风沙土-黄土地区土地利用变化及其对生态建设的意义

China has experienced dramatic land use changes over recent decades, with marked environmental and socio-economic consequences. Hengshan County, located in the aeolian-loessial area of Northwest China, was investigated to illustrate land use changes and their implications for environmental and long-term rural economic development. The farmland in Hengshan County significantly decreased during 1990--2003, whereas forest land and grassland increased. The conversion rates of farmland, orchard land, forest land and construction land varied markedly among different periods: 1990--1995, 1995--2000 and 2000--2003. Conversion of orchard land, grassland and construction land was dominant in 1990--1995, whereas the conversion of farmland to forest land mainly occurred in 2000--2003. The results suggested a profound transition in institutional policy and political economy of land management, including implementation of integrated soil erosion control projects, adoption of a market-oriented economy and the ‘Grain-for-Green’ policy, during this period in China. To achieve long-term sustainable land use in Hengshan County, efforts should aim at increasing off-farm income of rural families as well as establishing land-economizing mechanisms to promote land productivity, in addition to conservation measures.     

固定态铵的含量及中国某些耕地土壤NH4+的固定能力

Fixed ammonium contents and NH4^ fixation capacities of some representative cultivated solis collected from 16 provinces of China were studied.Results showed that the contents of fixed ammonium in soils ranged from 35 to 573 mg N kg^-1,with an average of 198mg Nkg^-1.The content of fixed ammonium correlated very significantly with mica content for tropical and subtropical soils,whereas this was not the case for soils in the temperate zone.At the end of K-exhausting experiment the fixed ammonium content increased in most soils studied.However,it decreased in smom temperate soils.Generally,fixation of added NH4^ could not be found either before or after K-exhausting experiment for highly weathered soils,including tropical soils and soils derived from granite-gneiss or Quaternary red clays in the subtropic zone,while for most soils in the Yangtze River dalta the NH4^ fixation capacity was rather high and increased significantly in the K-exhausted soils.     

三峡库区坡地表层风化特征研究

Extractability and mobility of Cu and Zn and their relationships with 1） accumulation of Cu and Zn and 2） soil pH were studied in three sandy soils （Wabasso, Ankona, and Winder） from commercial citrus groves in Florida, USA. The soils, with a broad range of Cu and Zn concentrations, were fractionated by a modified procedure of Amacher, while Cu and Zn mobility were evaluated using column leaching. The extractability of Cu and Zn increased with decreasing soil pH. Also with increasing total soil Cu and Zn for extractable Cu in the Wabasso sand a threshold level, where the metal extraction rate increased, was noted at 100 mg kg^-1, whereas for extractable Zn in the Wabasso sand the threshold level was found at 60 mg kg^-1 and in the Ankona sand at 120 mg kg^-1. These results suggested that the release potential of Cu and Zn was greater in the Wabasso sand than in the Ankona sand. The column leaching experiment showed that at total soil Cu or Zn concentrations 〈 100 mg kg^-1 all leachates had low Cu and Zn concentrations. However at total concentrations 〉 200 mg kg^-1 for Cu and 〉 150 mg kg^-1 for Zn with decreasing soil pH, the concentrations of both Cu and Zn in the leachates increased exponentially. Also in these sandy soils soluble Cu and Zn mainly originated from the exchangeable fractions, and pH was a key factor controlling Cu and Zn extractability and mobility.     

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.     

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.     

Exploring soil layers and water tables with ground-penetrating radar

Ground-penetrating radar (GPR) has been used predominantly for environments with low electrical conductivity like freshwater aquifers, glaciers, or dry sandy soils. The objective of the present study was to explore its application for mapping in subsurface agricultural soils to a depth of several meters. For a loamy sand and a clayey site on the North China Plain, clay inclusions in the sand were detected; the thickness, inclination, and continuity of the confining clay and silt layers was assessed; and a local water table was mapped. Direct sampling (soil coring and profiling) in the top meter and independent measurement of the water table were utilized to confirm the findings. Also, effective estimates of the dielectric number for the site with the dielectric number of moist clayey soils depending strongly on frequency were obtained. Thus, important properties of soils, like the arrangement and type of layers and in particular their continuity and inclination, could be explored with moderate efforts for rather large areas to help find optimal locations for the time-consuming and expensive measurements which would be necessary to detail a model of the subsurface.     

我国一些土壤中较难提取的固定态铵

Ninety-three soil samples and 19 sedimentary rock samples collected from 21 provinces of China were analyzed for their contents of fixed ammonium and total N by Kjeldahl-HF method. Results showed that amount of difficultly extractable fixed ammonium (the fixed ammonium that is not determinable by Kjeldahl procedures commonly used for soils) in soils ranged from 0 to 202 mg kg^-1. It was generally more than 50 mg kg^-1 in soils in Changji and Turpan districts, Xinjiang, accounting for 3.2%~36.8% with an average of 13.9% of the total N. For some Orthents derived from purple shale and purple sandstone in Sichuan and Hunan provinces and Chao soils derived from secondary loess in Henan Province and Ningxia Autonomous Region it was generally around 30 mg kg^-1, accounting for 4%~7% of the total soil N, and for most of the rest of soils studied, with the exception of some subsoils, no or trace difficultly extractable fixed ammonium could be detected. It was suggested that the difficultly extractable fixed ammonium was originated from parent rock, and for slightly weathered soils derived from parent materials rich in this form of N the Kjeldahl method might give underestimation of total soil N.     

Estimation of Sand Transportation Rate for Fixed and Semi- Fixed Dunes Using Meteorological Wind Data

Taibus County, Inner Mongolia, China, lies in a farming-pastoral ecotone, where severe wind erosion and various aeolian sand hazards are prevalent and fixed and semi-fixed sand dunes occur frequently. This study was conducted to investigate the relationships between sand transportation rate and wind speed for the fixed and semi-fixed sand dunes based on field measurements. The annual quantity of soil erosion by wind was estimated using meteorological wind data. The results indicated that the sand transportation rate in Taibus County in 2000 was 57.38 kg cm-1 year-1 for the semi-fixed dunes and 4.56 kg cm-1 year-1 for the fixed dunes. The total duration of erosive winds covered 12.5% of the time of the year, and spring posed the highest potential of sand transportation. Wind with low speed (≤ 17 m s-1) and high frequency plays a dominant role in sand transportation, while strong wind (≥ 17 m s-1) with low frequency significantly enhanced the sand transportation. Erosive wind speed, directions, and frequency were three crucial dynamic factors influencing sand hazards in the farming-pastoral ecotone. The dominant factors intensifying sand and dust storms in Taibus County might be related to the favorable wind condition in combination with the durable drought, which led to land desertification and vegetation degradation.     

辽西北地区风力侵蚀过程分析

辽西北地区土壤沙漠化形成的主要原因是土壤风蚀,为了定量评价辽西北沙化土壤在风力作用下的侵蚀状况,研究采用埋钎法,观测风速与土壤剥蚀深度及堆积厚度的关系。研究得出固定沙丘和流动沙丘的土壤剥蚀深度均随着风速的加大而增加;流动沙丘和固定沙丘,随着风速的加大,背风坡的坡中与坡脚的土壤堆积厚度均有不同程度的增加,而由于风力的剥蚀作用,坡顶的堆积厚度与风速呈负相关;一年内观测到的流动沙丘,半流动沙丘,固定沙丘的平均风蚀强度分别为167.9,57.8,4.2 mm/d。     

民勤县固定与半固定沙丘粒度特征分析

沉积物粒度特征可以反映沉积物形成的沉积环境、沉积过程和搬运营力、搬运过程等信息。以民勤县西北部半固定与固定沙丘为研究对象,运用粒度分析方法,对其表层沉积物进行了系统采样分析。结果表明,半固定、固定沙丘的粒度组成均以细沙为主,极细沙次之,二者粒级级配相似,含量却有不同。半固定沙丘平均粒径为2.69Φ,中等分选近对称中等峰度分布;固定沙丘平均粒径为2.66Φ,中等分选近对称尖窄峰度分布。半固定、固定沙丘平均粒径与偏度存在二次多项式关系（R2=0.404 1）;峰度与平均粒径、标准离差、偏度呈不显著线性正相关关系（0.550,0.496,0.356）;标准离差与平均粒径、偏度之间无相关性。     

高寒沙区人工沙棘对风沙危害的生态响应

[目的]沙棘(Hippophae rhamnoides)是高寒沙区典型的优良治沙物种,其风沙危害的抗逆性研究对沙棘生态适应性机理及高寒沙区生物治沙工作具有重大的探究与指导意义。[方法]对不同类型沙丘不同林龄的人工沙棘林进行了样方调查和风沙活动监测。[结果]沙棘群落特征与地表风蚀强度变化具有时空同步性。轻度风蚀与中轻度沙埋现象有助于沙棘的生长与群落的发展,固定与半固定沙丘人工沙棘的株高冠幅均为流动型沙丘沙棘的3~6倍;沙棘各生长指标与株下蚀积深度具有显著的二次函数拟合关系,8年生沙棘生长的最佳沙埋深度在30—40cm。2008—2016年,各沙丘沙棘群落特征与局地输沙率、粗糙度、蚀积深度等风沙活动特征分别表现出显著的指数递减、多函数递增和二次函数先增后加减的变化规律。[结论]高寒沙区沙棘对风沙危害的响应特征反映了沙棘良好的风沙适应能力,也指示沙棘造林技术需要注重立地条件选取、造林结构改进与多物种配置,保障沙棘的稳定生长势态与良好的生态修复效益。     

神府煤田风沙区采煤塌陷对风蚀的影响

[目的]探究神府煤田风沙区采煤塌陷对风沙活动的影响,为矿区防治风蚀危害和植被恢复提供科学依据。[方法]以塌陷区扰动地表为研究对象,通过野外定位观测,研究塌陷1~2a沙丘典型位置及不同的地表破损率对风蚀/风积量影响。[结果]塌陷1a、塌陷2a和对照(非塌陷)沙丘不同典型位置的风蚀/风积深度分别达到-28.2,-45.6和-2.8cm,其整体的风蚀概率达60%以上,90%以上和10%以下。地表破损率越大,其地表风积过程越显著,且随着地表破损率的减小,风沙运动状态逐渐由风积填缝过程转化为风蚀过程,其风蚀/风积深度(Q)与地表破损率(V)呈多项式函数关系。[结论]采煤塌陷有效地促进了风沙运动,改变了局部的风蚀/风积深度,可能引起固定半固定沙丘重新活化。     

A wind tunnel experiment to investigate the effect of polyvinyl acetate,biochar, and bentonite on wind erosion control

Due to the heavy costs of wind erosion control measures, the correct selection of technical methods is indispensable for a sustainable land management in arid and semiarid regions. Thus, the main goal of this research was to investigate the feasibility of using the clay minerals (i.e., bentonite), polyvinyl acetate and palm biochar for reducing the wind erosion in deserts surrounding the cities. The treatments were sprayed uniformly onto the containers (5 × 35 × 105 cm, 0.37 m²) with sand (collected from sand dunes surrounding Isfahan city, central Iran) in 3 replicates. The experiments were conducted in a wind tunnel with sequential repetitions after 1, 10, and 20 weeks. Among the studied treatments, the bentonite planters demonstrated to be the most effective soil erosion control measure by reducing soil loss and improving sand ablation. On the contrary, the palm biochar had less influence on the soil erosion control and only a slight effect on the threshold speed. For the future, further studies are required to select the best and most relevant soil erosion control measures under field conditions considering all the environmental aspects in arid regions of Iran.     

甘肃省武威市风力侵蚀分区治理规划及措施

[目的] 分析甘肃省武威市风力侵蚀空间动态变化特征,确定风力侵蚀可治理区划及其防治对策,为该市风蚀水土保持工作和生态环境建设提供科学参考。[方法] 基于多源地理信息数据,应用遥感、地理信息系统(ArcGIS)等技术手段,使用修正土壤风蚀方程(RWEQ)计算武威市2000-2020年5期风蚀模数,获得区域风蚀的面积分布和变化特征。结合重点建设工程分布等空间要素叠加分析方法,提出该市风力侵蚀可治理区域划分原则,并将该原则应用于划分武威市风力侵蚀可治理区。[结果] 修正土壤风蚀方程(RWEQ)能较好地估算武威市多年风力侵蚀模数,其多年风力侵蚀模数为5 788.98[t/(km²·a)],多年平均土壤风蚀总量1.92×10⁸ t;研究区风力侵蚀在时间上呈现总体下降,偶有上升趋势,且风力侵蚀强度等级明显减弱;在空间上具有明显的空间异质性,主要分布在民勤县、凉州区、古浪县;依据多要素叠加风蚀分区治理方案,武威市可治理风力侵蚀面积共2 872.66 km²,其中民勤县1 468.48 km²,凉州区708.75 km²,古浪县695.43 km²。[结论] 风力侵蚀分区治理是武威市风蚀水土保持的重点工作,根据风蚀分区治理划分结果,针对不同行政区划,民勤县北部坡度较低的平坦戈壁沙漠地区是其重点关注区域,治理措施应以风沙防治和植被恢复为主,并需要注意控制人为工程建设扰动的影响,明确区域管理范围;凉州区应注意采取工程措施和生物措施结合的方式进行治理;古浪县应以封育措施和对天然植被进行保护为主。同时,在戈壁沙漠地区需特别注意大型光伏电站建设等施工扰动的风沙防治和生态恢复。     

宁夏中部干旱带砂田抗风蚀性能研究

利用风洞模拟实验,研究了净风和挟沙风对砂田土壤风蚀的影响.结果表明:在净风吹蚀下,原状砂田的风蚀速率(0.37 gm-2 min-1)分别是农田和荒地的1/4和1/5,风蚀速率随风速的增加呈指数函数递增,其中砂田的递增速度低于农田或荒地;翻耕后的砂田在常见风速下的风蚀速率与农田和荒地相近(分别为1.67 g m-2 min-1、1.75 gm-2 min-1和1.83 gm-2 min-1),但在大风日则低于农田和荒地(分别为3.61 gm-2 min-1、58.83 g m-2 min-1和13.92 gm-2 min-1).挟砂田沙的风沙流吹蚀导致农田和翻耕砂田的风蚀速率增加,原状砂田则出现轻微的风积现象;挟农田土的风沙流吹蚀使原状砂田、翻耕砂田和荒地产生显著的风积,农田则出现更强烈的风蚀;挟沙风吹蚀下的风蚀(积)速率与风速的关系呈二次曲线函数.砂田的粗糙度明显高于农田(分别为0.023 cm和0.002 cm),且随着风速的增加,其间的差值越大;砂田和农田在不同风速条件下的风速廓线均可用指数函数表述.农田和荒地在压砂利用后,其抗风蚀和减尘性能显著增强.     

天然灌草植被防治土壤风蚀机理

通过对毛乌素沙地不同下垫面上风速、地表粗糙度、临界起沙风速、风沙流结构的观测,发现植被覆盖可以有效防止地表风蚀。植被盖度为40％的固定沙地近地表0．2m高度平均风速比流动沙地降低43％,侵蚀风的持续时数降低85％,临界起沙风速提高70％,地表粗糙度提高180倍;当风沙流速度相同时,20％覆盖度的半同定沙地较流动沙地可平均降低输沙62．33％;而植被盖度为40％的同定沙地较流动沙地可平均降低输沙93．07％。实验证明,单株植物同样可以降低风速。疏透结构和透风结构的单株沙蒿分别可以使植株后0．5m高度的风速较植株前方平沙地同高度的风速下降59．4％和19．8％。     

Threshold wind velocity as an index of soil susceptibility to wind erosion under variable climatic conditions

Wind erosion starts when the threshold wind velocity (µ_t) is exceeded. We evaluated the sensitivity of µ_t to determine the wind erosion susceptibility of soils under variable climatic conditions. Three years field data were used to calculate µ_t by means of the equation µ_t = ū ‐ σ Φ⁻¹ (γ), where ū is the mean wind speed (m s⁻¹), σ the ū standard deviation (m s⁻¹), γ the saltation activity and Φ the standard normal distribution function of γ. Saltation activity was measured with a piezoelectric sensor (Sensit). Results showed that ū of the whole studied period (3·41 m s⁻¹) was lower than µ_t (7·53 m s⁻¹), therefore, wind erosion was produced mainly by wind gusts. The µ_t values ordered in the sequence: Winter (6·10 m s⁻¹) < Spring (8·22 m s⁻¹) = Summer (8·28 m s⁻¹) < Autumn (26·48 m s⁻¹). Higher µ_t values were related to higher air humidity and lower wind speeds and temperatures. The µ_t values did not agree with the erosion amounts of each season, which ordered as follows: Summer (12·88 t ha⁻¹) > Spring (3·11 t ha⁻¹) = Winter (0·17 t ha⁻¹) = Autumn (no erosion). Low µ_t and erosion amounts of Winter were produced by a scarce number of gusts during eroding storms. We concluded that µ_t is useful as an index of soil susceptibility to wind erosion of different climatic periods. The use of a unique µ_t value in wind erosion prediction models can lead to erroneous wind erosion calculations. Copyright © 2008 John Wiley & Sons, Ltd.