Leaching of nitrogen from small forest catchments having different deposition and different stores of nitrogen

This investigation describes storage and leaching dynamics of nitrogen in three small forest catchments of the Swedish Integrated Monitoring Programme (IM). The sites, situated in North and South Sweden, have similar types of boreal forests and acid podsols although some properties of the catchments are very dissimilar. Total nitrogen deposition ranges from 0.2 to 2 g m^?2 yr^?1. Reported measurements include soil stores, tree biomass, soil water and stream water chemistry. The investigated catchments only leach small amounts of nitrogen. NH₄ ⁺ and NO₃ ^? concentrations are commonly low with sudden concentration peaks. Signs of developing nitrogen saturation are clearly visible at one of the sites. These signs are a low C/N ratio, nearly 20, in the upper part of the mineral soil and an unseasonal behaviour of NH₄ ⁺ and NO₃ ^? peaks in the soil solution. Properties of the soil organic matter, which contains huge stores of nitrogen, and the timing of hydrologic events, are crucial for the future leaching losses.     

Effect of acid deposition on forested catchment in the western Tokyo,Japan

Acid deposition and its effect on Andisols were investigated in the forest experimental station, the Rolling Land Laboratory (RLL), located in the Tama Hill region of Central Japan. The annual volume-weighted mean pH value of open bulk precipitation was 4.8 in the period 1990 to 1992. Nitrate deposition at RLL was larger than for sulfate, which was obviously different from results in Japan Environment Agency (JEA) stations or in study areas of Europe and North America. Abundant nitrate deposition was ascribed to the high emissions from a non-point source, mainly cars. Although sulfate concentration in throughfall fluctuated, its concentration in soil solution was kept at a low level. This was attributed to the high sulfate adsorption capacity of the Andisols.     

Hydrochemical budgets of a small forested granitic catchment exposed to acid deposition: The strengbach catchment case study (Vosges massif,France)

Hydrochemical budgets have been obtained for the 3-yr period 1986–89 at Strengbach, a small granitic basin in the Vosges mountains (north-eastern France). Here, the spruce forest shows both yellowing and crown thinning, symptoms of forest decline. Water amount and surface water chemistry were monitored in each ecosystem compartment. Bulk precipitation is acidic. Some pollution episodes occur in winter and early spring, but the annual bulk deposition acidity is rather low. Throughfall however, is much more concentrated, particularly for H⁺ and associated strong acid anions. These inputs come as occult deposits which comprise major ecosystem inputs, as confirmed by the chloride balance for the catchment. Input-output budgets for the catchment indicate a net deficit of base cations, especially calcium. Sulfate also shows a net loss while N budget is well balanced. As the soil exchange capacity is nearly exhausted for base cations, and dominated by H⁺ and Al, the neutralization of incident acid inputs occurs mainly in the weathered bedrock. Silicate weathering processes lead to high losses of cations and of silica. Aluminium hydroxide is precipitated; however, bicarbonate remains very low indicating poorly-buffered surface water.     

Factors influencing atmospheric deposition,stream export,and landscape accumulation of trace metals in forested watersheds

Wet and dry deposition inputs and streamflow output of Cd, Mn, Pb, Zn, and Al were measured intermittently at four deciduous forested watersheds in the southeastern United States between 1976 and 1982. Atmospheric inputs to each site were similar, varying by factors of 1.1 to 2.2 for the different metals. Metal levels in precipitation indicate that these sites are representative of rural, continental areas. Metals in rain exhibit significant temporal and spatial trends, with concentrations generally higher during summer than winter at all sites and generally lowest at the more remote site. The concentrations of Cd and Pb in both wet and dry deposition decreased between the period 1976 to 1977 and 1981 to 1982. Ion ratios and enrichment factors suggest that Mn is largely soil derived in atmospheric samples while Cd, Pb, and Zn are enriched over typical soil levels. Factor analysis indicates that soil components influence both Al and Mn while fine aerosol components influence Cd in wet and dry deposition. Both components influence the behavior of Pb. Dry deposition dominated the input of Mn and Al to each site, while wet deposition was the major input process for the other metals (54 to 85% of total). On an annual basis, deposited Cd, Pb, and Zn are strongly retained in each watershed: 2% of the Pb, 8 to 29% of the Cd, and 8 to 34% of the Zn inputs were transported in stream flow. Deposited Mn and Al are retained to a lesser degree and show a net loss from two sites. Metal export is controlled by stream pH, organic carbon, bedrock geology, and hydrologic characteristics of each site.     

Sulphur and nitrogen input to the Ratanica forested catchment (Carpathian Foothills,southern Poland)

The study covers 1991–1994 concentrations of SO₂ and NO₂ in the air, concentrations of sulphur and nitrogen in bulk precipitation, throughfall and stemflow as well as input of S and N to the Ratanica forested catchment (S. Poland), which is exposed to moderate anthropogenic pollution are presented. There was high input of sulphur (26 kg ha^?1) and nitrogen (24 kg ha^?1) to the catchment, mainly in NH4⁺ (18 kg ha^?1). The significant contribution of NH₄ ⁺ connected with intensive agriculture in surrounding fields has led to eutrophication of the ecosystem.     

Measurements of atmospheric deposition and internal circulation of base cations to a forested catchment area

The dry deposition of base cations to a Norway spruce stand was estimated by multiplying the ratio of the ion deposition to the sodium deposition on a surrogate surface with the dry deposition of sodium on the forest stand. The method can in principle only be applied to species that are present only in particles, but the method gives reasonable results when tested on ions that are also dry deposited in other forms (SO ₄ ^2– . NO ₃ ^– and NH ₄ ⁺ ). The atmospheric input and especially the dry deposition of base cations is an important replacement for the loss of base cations from the soil by run-off. The calculated internal circulation of K⁺ and Ca²⁺ showed maxima synchronously with rainfall maxima and constitute 71% and 53%, respectively, of the net throughfall deposition. The internal circulation of Ca²⁺ was almost equal to the SO₂ uptake.     

Sulphate deposition to a small upland catchment at suikerbosrand,South Africa

Water, Air, & Soil Pollution - In 1992, a study was initiated by the Water Research Commission of South Africa, to investigate the relationship between atmospheric deposition and water quality...     

Contribution of dissolved organic nitrogen deposition to nitrogen saturation in a forested mountainous watershed in Tsukui, Central Japan

Nitrogen (N) budget was estimated with dissolved inorganic N (DIN) and dissolved organic N (DON) in a forested mountainous watershed in Tsukui, Kanagawa Prefecture, about 50 km west of Tokyo in Central Japan. The forest vegetation in the watershed was dominant by Konara oak (Quercus serrata) and Korean hornbeam (Carpinus tschonoskii), and Japanese cedar (Cryptomeria japonica). Nitrate (NO₃ ^?) concentration in the watershed streamwater was averagely high (98.0 ±± 19 (±± SD, n = 36) μmol L^?1) during 2001–2003. There was no seasonal and annual changes in the stream NO^? ₃ concentration even though the highest N uptake rate presumably occurred during the spring of plant growing season, a fact indicating that N availability was in excess of biotic demands. The DON deposition rates (DON input rates) in open area and forest area were estimated as one of the main N sources, accounting for about 32% of total dissolved N (TDN). It was estimated that a part of the DON input rate contributed to the excessive stream NO^? ₃ output rate under the condition of the rapid mineralization and nitrification rates, which annual DON deposition rates were positively correlated with the stream NO₃ ^? output rates. The DON retention rate in the DON budget had a potential capacity, which contributed to the excessive stream NO^? ₃ output rate without other N contributions (e.g. forest floor N or soil N).     

亚热带农业小流域水体氮素及其稳定同位素分布特征

为控制流域氮素养分流失、改善流域水体环境,以亚热带典型农业小流域脱甲河为研究对象,对表层水体铵态氮(NH_4~+-N)、硝态氮(NO_3--N)浓度和水体硝态氮δ~(15)N(δ~(15)N-NO_3-)、沉积物有机质δ~(15)N(δ~(15)N-Org)浓度进行了连续试验观测,分析氮素浓度及其稳定同位素值的时空特征,探讨影响氮素分布的环境因子及水体NO_3-和沉积物有机质氮素的可能来源。结果表明:水体NO_3--N浓度明显高于NH_4~+-N,均值分别为1.62 mg·L~(-1)和0.90mg·L~(-1),并且分别在6月、8月及冬季较高;城镇区和农田区水体NH_4~+-N浓度与其他类型区差异显著(P0.05),并且显著高于其他水体;NO_3--N浓度在城镇区、农田区及山间林地区较高,水库区较低。支流NH_4~+-N浓度高于干流,均表现为冬季春季夏季秋季;干流、支流NO_3--N浓度分别表现为冬季夏季秋季春季、秋季冬季夏季春季。源头和出口处水体均表现为NO_3--N浓度高于NH_4~+-N,源头处氮素浓度低于出口处。水体δ~(15)N-NO_3-及底泥δ~(15)N-Org值分布范围分别为-19.87‰~8.11‰和-0.69‰~6.51‰,水体δ~(15)N-NO_3-最高值在Ⅲ级河段,最低值出现于Ⅳ级河段,各级河段间水体δ~(15)N-NO_3-11月差异较小,而1、2月差异明显;河流底泥δ~(15)N-Org最高值也位于Ⅲ级河段,而最低值则在Ⅰ级河段,Ⅲ、Ⅳ级河段δ~(15)N-Org值随时间变化趋势较为一致,Ⅰ、Ⅱ级河段δ~(15)N-Org最小值出现于1月。总之,脱甲河水体存在氮素污染现象且以外源输入为主,水体氮素来源主要为土壤有机质、人工合成肥料及陆源有机质,开展流域氮素分布及来源研究对认识流域尺度氮污染物的源解析具有一定科学意义。     

Application of catchment scale sediment delivery model INCA-Sed to four small study catchments in Finland

The novel catchment scale erosion and sediment delivery model INCA-Sed was applied to four small study catchments in Finland. Three of these, the Mustajoki, Haarajoki and Luhdanjoki, are headwater catchments located in central Finland. The associated rivers have differing morphological characteristics varying from a ditch to a small river. Soil textures in the area are derived from moraine deposits and are largely sand and gravel. The Mustajoki and Haarajoki catchments are forested and only 10% of the area is under cultivation. In the Luhdanjoki catchment agricultural fields cover 40% of the area. The fourth study site, the Savijoki catchment, represents an intensively cultivated area in south-western Finland. Cultivated fields cover 40% of the catchment area, and they are located on clay soils along the river. The INCA-Sed model was able to capture both the correct magnitude and seasonal behaviour of suspended sediment concentrations in the rivers, as well as the correct magnitude of the sediment load derived from different land use classes. Small differences in river morphology and soil textures between the catchments have a significant influence on suspended sediment concentration in the rivers. Correct timing of suspended sediment concentration peaks is not, however, captured by the INCA-Sed model, which may be due to the stochastic nature of erosion and delivery processes at the catchment scale which are not taken into account in the parameter values used in the modelling. Parameter values were estimated from previous researches based on average process loads. The INCA-Sed model was, however, generally found to be a suitable tool for evaluating effects of land use change on erosion and sediment delivery in Finland as it correctly reproduces spatial and seasonal variations in sediment delivery, in addition to annual averages with spatial and temporal variations.     

Contribution of dissolved organic nitrogen deposition to total dissolved nitrogen deposition under intensive agricultural activities

For elucidating the atmospheric deposition contribution of dissolved organic nitrogen (DON) to the total dissolved nitrogen (TDN) deposition rate, dissolved inorganic nitrogen (DIN: NH₄ ⁺ + NO₃ ^–) and DON deposition rates were annually and monthly estimated during 4 and half-yr monitoring period in an experimental multi-farm under intensive agricultural activities of N fertilizer use and animal husbandry in Central Japan. Annual NH₄ ⁺, DON and NO₃ ^– deposition rates in bulk and wet deposition data accounted for 48%, 32% and 20% of TDN deposition, respectively, which indicated that this area is strongly affected by the intensive agricultural activities. The DIN and DON deposition rates were respectively estimated at 21.6 and 10.1 kg N ha^?1 yr^?1, which ranked high in a worldwide regional data set. Consequently, this area has been exposed to a large amount of N deposition including DON with N fertilizer input. The difference between bulk and wet deposition rates (NH₄ ⁺ and DON) is one of important factors controlling the N deposition in this area. Monthly DON deposition showed positive correlations with DIN and NH₄ ⁺ deposition rates, respectively, with a significant linear regression curve. The linear regression curve of our monthly data (n = 127) indicates the same trend as the worldwide annual data set (n = 31).     

Influence of nitrogen on cellulose and lignin mineralization in blackwater and redwater forested wetland soils

 Microcosms were used to determine the influence of N additions on active bacterial and active fungal biomass, cellulose degradation and lignin degradation at 5, 10 and 15 weeks in soils from blackwater and redwater wetlands in the northern Florida panhandle. Blackwater streams contain a high dissolved organic C concentration which imparts a dark color to the water and contain low concentrations of nutrients. Redwater streams contain high concentrations of suspended clays and inorganic nutrients, such as N and P, compared to blackwater streams. Active bacterial and fungal biomass was determined by direct microscopy; cellulose and lignin degradation were measured radiometrically. The experimental design was a randomized block. Treatments were: soil type (blackwater or redwater forested wetlands) and N additions (soils amended with the equivalent of 0, 200 or 400 kg N ha^–1 as NH₄NO₃). Redwater soils contained higher concentrations of C, total N, P, K, Ca, Mn, Fe, B and Zn than blackwater soils. After N addition and 15 weeks of incubation, the active bacterial biomass in redwater soils was lower than in blackwater soils; the active bacterial biomass in blackwater soils was lower when 400 kg N ha^–1, but not when 200 kg N ha^–1, was added. The active fungal biomass in blackwater soils was higher when 400 kg N ha^–1, but not when 200 kg N ha^–1, was added. The active fungal biomass in redwater wetland soils was lower when 200 kg N ha^–1, but not when 400 kg N ha^–1, was added. Cellulose and lignin degradation was higher in redwater than in blackwater soils. After 10 and 15 weeks of incubation, the addition of 200 or 400 kg N as NH₄NO₃ ha^–1 decreased cellulose and lignin degradation in both wetland soils to similar levels. This study indicated that the addition of N may slow organic matter degradation and nutrient mineralization, thereby creating deficiencies of other plant-essential nutrients in wetland forest soils. Received: 7 April 1999     

黄土高原小流域土壤水分及全氮的垂直变异

为了研究黄土高原土壤中水分及全氮垂直分布及变异情况,对陕北神木县六道沟小流域中苜蓿地、荒草地、农地、柠条地以及油松地5种不同植被类型下0～800 cm土层中土壤含水率和土壤全氮进行了测定和分析。土壤含水率在垂直方向上呈现出干湿交替的层状分布。植被类型影响土壤水分含量的垂直剖面分布;各植被类型下相对高湿层和低湿层出现的深度不同;不同深度土层平均土壤含水率不同。农地及退耕荒草地土壤水分涵养较好,垂直方向上含水率变化较大;人工植被苜蓿、柠条消耗土壤水分较多,土壤含水率变化相对平缓;油松地平均土壤含水率及变化幅度居中。研究区域中,土壤全氮含量水平较低,表层发生陡降后,在20 cm以下土层中仍以很小的变幅降低,变化平缓。柠条地土壤全氮含量高于其他植被类型。     

Influence of nitrogen on atrazine and 2, 4 dichlorophenoxyacetic acid mineralization in blackwater and redwater forested wetland soils

 Microcosms were used to determine the influence of N additions on active bacterial and fungal biomass, atrazine and dichlorophenoxyacetic acid (2,4-D) mineralization at 5, 10 and 15 weeks in soils from blackwater and redwater wetland forest ecosystems in the northern Florida Panhandle. Active bacterial and fungal biomass was determined by staining techniques combined with direct microscopy. Atrazine and 2,4-D mineralization were measured radiometrically. Treatments were: soil type, (blackwater or redwater forested wetland soils) and N additions (soils amended with the equivalent of 0, 200 or 400 kg N ha^–1 as NH₄NO₃). Redwater soils contained higher concentrations of C, total N, P, K, Ca, Mn, Fe, B and Zn than blackwater soils. After N addition and 15 weeks of incubation, active bacterial biomass in redwater soils was lower when N was added. Active bacterial biomass in blackwater soils was lower when 400 kg N ha^–1, but not when 200 kg N ha^–1, was added. Active fungal biomass in blackwater soils was higher when 400 kg N ha^–1, but not when 200 kg N ha^–1, was added. Active fungal biomass in redwater soils was lower when 200 kg N ha^–1, but not when 400 kg N ha^–1, was added. After 15 weeks of incubation 2,4-D degradation was higher in redwater wetland soils than in blackwater soils. After 10 and 15 weeks of incubation the addition of 200 or 400 kg N ha^–1 decreased both atrazine and 2,4-D degradation in redwater soils. The addition of 400 kg N ha^–1 decreased 2,4-D degradation but not atrazine degradation in blackwater soils after 10 and 15 weeks of incubation. High concentrations of N in surface runoff and groundwater resulting from agricultural operations may have resulted in the accumulation of N in many wetland soils. Large amounts of N accumulating in wetlands may decrease mineralization of toxic agricultural pesticides. Received: 26 June 1998     

Validating erosion rate estimates provided by caesium‐137 measurements for two small forested catchments in Calabria,southern Italy

Increasing concern for problems of soil degradation and the off‐site impacts of accelerated erosion has generated a need for improved methods of estimating rates and patterns of soil erosion by water. The use of environmental radionuclides, particularly ¹³⁷Cs, to estimate erosion rates has attracted increased attention and the approach has been shown to possess several important advantages. However, the use of ¹³⁷Cs measurements to estimate erosion rates introduces one important uncertainty, namely, the need to employ a conversion model or relationship to convert the measured reduction in the ¹³⁷Cs inventory to an estimate of the erosion rate. There have been few attempts to validate these theoretical conversion models and the resulting erosion rate estimates. However, there is an important need for such validation, if the ¹³⁷Cs approach is to be more widely applied and reliance is to be placed on the results obtained. This paper reports the results of a study aimed at validating the use of two theoretical conversion models, namely the exponential depth distribution model and the diffusion and migration model, that have been used in several recent studies to convert measurements of ¹³⁷Cs inventories on uncultivated soils to estimates of soil erosion rates. The study is based on data assembled for two small catchments (1.38 and 1.65 ha) in Calabria, southern Italy, for which measurements of sediment output are available for the catchment outlet. The two catchments differ in terms of the steepness of their terrain, and this difference is reflected by their sediment yields. Because there is no evidence of significant deposition within the two catchments, sediment delivery ratios close to 1.0 can be assumed. It is therefore possible to make a direct comparison between the estimates of the mean annual erosion rates within the two catchments derived from ¹³⁷Cs measurements and the measured sediment outputs. The results of the comparison show that the erosion rate estimates provided by both models are reasonably consistent with the measured sediment yields at the catchment outlets. However, more detailed assessment of the results shows that the validity of the erosion rate estimates is influenced by the magnitude of the erosion rates within the catchment. The exponential depth distribution model appears to perform better for the catchment with higher erosion rates and to overestimate erosion rates in the other catchment. Similarly, the basic migration and diffusion model performs better for the catchment with lower erosion rates and overestimates erosion rates in the other catchment. However, the improved migration and diffusion model appears to perform satisfactorily for both catchments. There is a need for further studies to extend such independent validation of the ¹³⁷Cs technique to other environments, including cultivated soils, and to other conversion models and procedures. Copyright © 2003 John Wiley & Sons, Ltd.     

Nitrate leaching from a small, underdrained, grassland, clay catchment

Abstract. Losses of nitrogen in the tile drainflow from a clay soil (Evesham series) under grazed grassland were monitored during the 1982/83 and 1983/84 drainflow seasons. In 1982/83, 40% of the discharge had a NO₃⁻ concentration > 11.3 mgNl⁻¹, while in 1983/84 concentrations were always > 20 mgNl⁻¹. Total N lost by leaching was 17.5 and 48.7 kg ha⁻¹ in 1982/83 and 1983/84 respectively, which was equivalent to 9 and 43% of the fertilizer applied. The marked difference in N losses for the two seasons was attributed to differences in the quantity and timing of N fertilizer applications, the dryness of the preceding summer and the duration and density of stocking.     

Multi-parameter fingerprinting of sediment deposition in a small gullied catchment in SE Australia

The determination of relative contributions of potential sediment sources is an important step in the development of management strategies to combat soil erosion. In a 1.2 km² gullied catchment in southeastern New South Wales, multi-parameter fingerprinting of sediment deposited in successive downstream pools has identified gully walls as the dominant sediment source when the grazed pasture surface was the only other potential source. The median fractional contributions remained relatively steady in the successive downstream pools, with the gully walls responsible for between 90% and 98% of the pool sediment. This result was achieved despite the ratio of the source areas varying considerably between successive nested subareas. Reliability bounds on the predictions, accounting for limited sampling of sources, were well constrained and varied between 5.4% and 13.8%. Downstream of an unsealed road crossing, sediment from the road source dominated the pool sediments such that contributions from the pasture surface and gully sources could not be determined.     

Investigating the spatial distribution of soil erosion and deposition in a small catchment on the Loess Plateau of China, using Cs

An understanding of the spatial distribution of soil erosion and deposition in a catchment is important for designing soil and water conservation measures. Traditional monitoring techniques provide limited information on the spatial patterns of erosion and deposition. The fallout radionuclide ¹³⁷Cs was used to document rates and patterns of soil redistribution within a small (0.17 km²) gully catchment located near An'sai in Shaanxi Province, representative of the Loess Plateau of China. The local reference inventory was estimated to be 2266 Bq m⁻² and the ¹³⁷Cs inventories of 198 soil cores collected from the catchment, ranged from 0 to 3849 Bq m⁻². The coefficient of variation of the inventories of the individual cores was 0.85, reflecting the complex pattern of ¹³⁷Cs redistribution by soil erosion and deposition. Estimates of erosion rates derived from ¹³⁷Cs measurement ranged from less than 25 to 150 Mg ha⁻¹ year⁻¹, with about 70% of the net soil loss from the catchment coming from the gully area. The ¹³⁷Cs technique was shown to provide an effective means of documenting the spatial distribution of soil erosion and deposition within the small catchment.     

珠江三角洲小流域地下水化学特征及演化规律

珠江三角洲地下水环境日益恶化,已成为制约经济社会发展的重要因素。以珠海市具有典型特征的闭合小流域作为研究对象,分旱、雨两季采集地下水分析主要离子及D、18O同位素,全面系统地研究了地下水水化学的时空变异特征与演变规律。结果表明：研究区内地下水主要受大气降水及附近地表水体渗透补给,以蒸发及地下水径流排泄,季节变化对区域内水化学空间变异性影响较小。沿地下水流方向（补给区-径流区-排泄区）,地下水化学类型主要从Ca-Na（Mg）-HCO3型向Na-Cl和Na-K-HCO3-CO3型演化,风化-溶滤、离子交换、海陆交互作用是控制当地地下水质演变的主要水文化学过程。     

Liming and fertilization of acid forest soil: Short-term effects on runoff from small catchments

Increased atmospheric deposition of strong acids and deposition of potentially acidifying compounds (e.g. ammonium) has caused a decline in pH and exchangeable base cations in forest soils in Sweden. In recent years, attention has been paid to liming of forest soil as a method to counteract the effects of acid deposition. Experiments with liming, fertilization and woodash treatment of acid forest soils started in 1984. The aim of this study was to determine the effects of low doses of lime (500 to 1500 kg ha^–1) in combination with N fertilizers on tree growth, nutritional status of trees as well as soil, and runoff chemistry. This paper describes the short term effects of liming and fertilization on runoff from ten small catchments in two regions in south Sweden. The effects of liming were small in both areas. In the catchments fertilized with N (NH₄NO₃), a substantial leakage of various N species appeared in runoff after treatment. The increased N output was dominated by nitrate. The excess leakage of N during 2 yr after fertilization was 25 and 13% as an average of the applied N in the two study areas. The mobile nitrate increased the base cations output via runoff with 10 to 100% during 1 yr after N treatment. The runoff of Al increased with 60 to 1009, the first year in the fertilized catchments. Mobilization of cations was also influenced by ammonium, especially K that was exchanged by ammonium on the surface of the soil particles. The effects of woodash-treatment were small, however, sulfate in the ash leaked out following application and about 100% of the added sulfate was found in runoff during the first year.