Leaching of metals from the A-horizon of a spruce forest soil

The study quantifies the amount of metals (Na, K, Mg, Ca, Al, Fe, Mn, Ni, Cr, V, Cu, Zn, Cd, Pb) leached from the A-horizon of a podzolic spruce forest soil in southern Sweden during 2.5 yr, and offers statistical evidence of environmental conditions of importance to metal release. Considerable losses of Pb, Cr, Ni and V may occur from the A-horizon of forest soils under conditions favoring leaching of organic matter, Fe, and Al, i.e. during periods of comparably high soil temperature and moisture. Metals with a larger fraction present in exchangeable form (Na, Mg, Ca, Zn, Cd) are more susceptible to minor pH changes. An accelerated deposition or internal production of acidic matter therefore will reduce the retention times of these elements particularly.     

Mobility of heavy metals in pine forest soils as influenced by experimental acidification

The mobility of Pb, Zn, Cd and Cu was examined at two adjacent experimental plots at åmli, southern Norway, B-1 and B-2. Both experiments were established on the same glacifluvial deposits, with forest consisting of uniform stands of Pinus sylvestris L. The forest in B-1 was planted between 1968 and 1970, while B-2 consisted of naturally regenerated trees. The experiments included plots supplied with artificial rain of varying acidity over a period of seven and eight years for B-1 and B-2, respectively, in addition to control plots. In experiment B-1, experimental acidification was carried out both in unlimed plots and in plots applied with three different levels of lime. The two experiments showed distinct differences with respect to effects of the acidification on mobilization of heavy metals from the O horizon. In experiment B-1, the amount of Zn and Cd decreased with decreasing pH in artificial rain, while Pb and Cu were not appreciably affected. The reduction in Zn and Cd concentrations ceased after termination of the acidification experiment. Liming reduced the leachability of Zn, but still appreciable amounts of Zn were obviously leached from the O horizon during the experiment. In experiment B-2 a high retention even of Zn and Cd was observed in the O horizon, probably due to microbial uptake and accumulation.     

Organic matter dynamics in a temperate forest as influenced by soil frost

In the future, climate models predict an increase in global surface temperature and during winter a changing of precipitation from less snowfall to more raining. Without protective snow cover, freezing can be more intensive and can enter noticeably deeper into the soil with effects on C cycling and soil organic matter (SOM) dynamics. We removed the natural snow cover in a Norway spruce forest in the Fichtelgebirge Mts. during winter from late December 2005 until middle of February 2006 on three replicate plots. Hence, we induced soil frost to 15 cm depth (at a depth of 5 cm below surface up to –5°C) from January to April 2006, while the snow‐covered control plots never reached temperatures < 0°C. Quantity and quality of SOM was followed by total organic C and biomarker analysis. While soil frost did not influence total organic‐C and lignin concentrations, the decomposition of vanillyl monomers (Ac/Ad)_V and the microbial‐sugar concentrations decreased at the end of the frost period, these results confirm reduced SOM mineralization under frost. Soil microbial biomass was not affected by the frost event or recovered more quickly than the accumulation of microbial residues such as microbial sugars directly after the experiment. However, in the subsequent autumn, soil microbial biomass was significantly higher at the snow‐removal (SR) treatments compared to the control despite lower CO₂ respiration. In addition, the water‐stress indicator (PLFA [cy17:0 + cy19:0] / [16:1ω7c + 18:1ω7c]) increased. These results suggest that soil microbial respiration and therefore the activity was not closely related to soil microbial biomass but more strongly controlled by substrate availability and quality. The PLFA pattern indicates that fungi are more susceptible to soil frost than bacteria.     

Soil acidification and element fluxes of a Fagus sylvatica forest as influenced by simulated nitrogen deposition

Water, Air, &; Soil Pollution - The influence of simulated 3- and 9-fold increases in the current N deposition on element fluxes and soil acidification was investigated in a beech forest in S...     

Bioactivity in limed soil of a spruce forest

Summary The stimulative effect of lime on the bioactivity of various soil horizons was demonstrated by the ATP test, and respiration and microcalorimetric measurements, but not by FDA hydrolysis or the iron reduction test. The latter showed clear inhibition. When the natural structure of layers was saved while sampling, a smaller stimulation of bioactivity was observed than in the case of mixing natural layers. No stimulation was recorded when the lime layer was removed.     

Effects of liming,fertilization and acidification on pH,soil moisture,and ATP content of soil from a spruce forest in Southern Germany

Short-term and medíum-term effects of liming (CaCO₃), fertilization [5Ca(NO)₃)₂·NH₄NO₃], and acidification on soil bioactivity were measured in a spruce stand in Southern Germany. The experiment was set up in a randomized block design. Acid precipitation lowered the pH, liming increased the pH, while fertilization caused only small alterations in pH values. Significant differences in soil moisture occurred only in the mineral horizons. The soil ATP content of the humus layers decreased in all plots (control included) up to day 100. On all sampling dates, a pronounced decrease in ATP content followed the acidification. Minor decreases in ATP were observed after fertilization, while liming produced no defined effects. Similar trends, but less pronounced, were observed in the mineral horizons. Only a few significant correlations were found between pH values and ATP or between moisture and ATP within a treatment and sampling date. Present address: Institut für Biologie II (Zoologie), RWTH Aachen, Kopernikusstrasse 16, D-52056 Aachen, Germany     

Modelling subalpine forest dynamics as influenced by a changing environment

FORSUM, a forest succession model of the JABOWA/FORET type was applied to simulate possible impacts of environmental changes on subalpine forest ecosystems and compared with the model FORECE (Kienast, 1987). The model used is based on approaches of Botkin et al. (1972), Shugart (1984) and Kienast (1987) and has been improved by implementing soil water movement calculations based on a user-defined one-dimensional nonhomogeneous soil profile. The influence of a possible climatic change on subalpine ecosystems was investigated for three different sites in the Grisons (Switzerland). The scenarios used are based on climate change predictions of General Circulation Models. A temperature increase of 3? C would cause important changes in species composition. Deciduous trees would invade today's subalpine belt causing a displacement of various conifers in this zone. Some coniferous species might eventually migrate into today's alpine zone which would consequently become afforested. Comparing the vegetation changes as predicted by the model FORSUM and FORECE we found that the models generate the main general patterns. However under global warming and a concurrent precipitation decrease total biomass production seems to be overestimated by FORECE. Information about seed dispersal rates (horizontal and vertical), seed availability and soil formation processes should be implemented in these models to improve the reliability of the predictions.     

Aluminium chemistry of the soil solution in an acid forest soil as influenced by percolation rate and soil structure

The predicted activity of Al in the soil solutions of acid forest soils often differs from that observed in the field. We have investigated the influence of soil structure and flow rate of the soil solution on the aluminum release to explain this divergence. Disturbed and undisturbed samples of soil were collected from the A and B horizons of a dystric cambisol at Waldstein (Fichtelgebirge, Germany). The samples were irrigated with solutions mixed according to field data on throughfall or soil solution composition with pH 3.5 with flow rates of 4 mm d^?1, 12 mm d^?1 and 36 mm d^?1. The percolates were analysed for major ions. Resulting relations between pH and pAl were compared with batch experiments. In neither the A horizon nor in the B horizon did soil structure influence the relation between pH and pAl. The apparent equilibrium between pH and pAl was described as the pK_app value with pK_app= pAl—a pH (where a is an empirical constant). It was found that the pK_app values for the column percolates were in the range of variation of those found in batch experiments. Flow rate had no influence on pK_app at 4 and 12 mm d^?1. At 36 mm d^?1 a significant increase of pK_app was observed. This relative undersaturation of Al was more pronounced in the A horizon than in the B horizon. When flow is fast Al release into the percolating soil solution might be limited by diffusion.     

Biomass distribution of a microarthropod community in spruce forest soil

It has been previously demonstrated that fractal habitat features, combined with the allometric relationship between body size and metabolic rate, can sufficiently predict the biomass distribution in arthropod communities. This study shows that the relationship between biomass B and abundance N in a community of soil microarthropods is flatter than might be predicted by a combination of hypotheses concerning the (1) fractal dimension of pore surface, (2) metabolic rate, and (3) accessibility of soil pores. The relationship between B and N is N B ^-0.80 for the size classes to the right of the mode of the biomass distribution. Since the relationship between B and metabolic rate M is M B ^0.81, the energy use per size class is independent of size (B ^-0.80×B ^0.81 B ⁰) for a broad range of size classes with the exception of very small microarthropods.     

水稻子实对不同形态重金属的累积差异及其影响因素分析

在分析成都平原核心区土壤重金属(Cd、Cr、Pb、Cu、Zn)全量、各形态含量及相应点位种植的水稻子实重金属含量的基础上,通过统计分析、空间插值及线性回归方程的模拟,研究了土壤Cd、Cr、Pb、Cu、Zn全量的空间分布状况、各形态重金属含量统计特征,以及水稻子实对重金属各形态的累积差异及其影响因素。结果表明,成都平原水稻土重金属污染较轻,除Cd外,均低于国家土壤环境质量二级标准。土壤中重金属的可交换态含量均较低,Cd主要以铁锰氧化态存在,Cr、Cu、Zn、Pb主要以残渣态存在。水稻子实对5种重金属的累积效应顺序为:Cd>Zn>Cu>Pb>Cr。与水稻重金属累积关系密切的重金属活性形态(可交换态、碳酸盐结合态、铁锰氧化物结合态和有机物结合态)主要有:Cd的碳酸盐结合态、Cr的可交换态、Pb的有机物结合态和Cu的碳酸盐结合态含量;Zn各活性形态对水稻子实含量的影响不明显。土壤理化性质对不同活性形态重金属元素的影响效应各不相同。活性态Cd主要受有机质、pH和容重的影响;活性态Cr与pH、有机质、CEC和容重密切相关;活性态Pb与有机质、容重、中细粉粒、砂粒等均有密切的关系;Cu的活性主要受粘粒、有机质含量的影响;Zn的有效性主要受pH、有机质、砂粒、容重的影响。总的看来,对土壤Cd、Cr、Pb、Cu、Zn各活性形态含量影响效应较强的是有机质、pH、容重,而与土壤吸附性能密切相关的颗粒组成、CEC的影响不甚明显。     

水稻籽实对不同形态重金属的累积差异及其影响因素分析

在分析成都平原核心区土壤重金属（Cd、Cr、Pb、Cu、Zn）全量、各形态含量及相应点位种植的水稻籽实重金属含量的基础上，通过统计分析、空间插值及线性回归方程的模拟，研究了土壤Cd、Cr、Pb、Cu、Zn全量的空间分布状况、各形态重金属含量统计特征，以及水稻籽实对重金属各形态的累积差异及其影响因素。结果表明，成都平原水稻土重金属污染较轻，除Cd外，均低于国家土壤环境质量二级标准。土壤中重金属的可交换态含量均较低，Cd主要以铁锰氧化态存在，Cr、Cu、Zn、Pb主要以残渣态存在。水稻籽实对5种重金属的累积效应顺序为：Cd＞Zn＞Cu＞Pb＞Cr。与水稻重金属累积关系密切的重金属活性形态（可交换态、碳酸盐结合态、铁锰氧化物结合态和有机物结合态）主要有：Cd的碳酸盐结合态、Cr的可交换态、Pb的有机物结合态和Cu的碳酸盐结合态含量；Zn各活性形态对水稻籽实含量的影响不明显。土壤理化性质对不同活性形态重金属元素的影响效应各不相同。活性态Cd主要受有机质、pH和容重的影响；活性态Cr与pH、有机质、CEC和容重密切相关；活性态Pb与有机质、容重、中细粉粒、砂粒等均有密切的关系；Cu的活性主要受粘粒、有机质含量的影响；Zn的有效性主要受pH、有机质、砂粒、容重的影响。总的看来，对土壤Cd、Cr、Pb、Cu、Zn各活性形态含量影响效应较强的是有机质、pH、容重，而与土壤吸附性能密切相关的颗粒组成、CEC的影响不甚明显。     

茶树种植对中国东部黄棕壤酸化的影响

Soil acidification is an important process in land degradation around the world as well as in China. Acidification of Alfisols was investigated in the tea gardens with various years of tea cultivation in the eastern China. Cultivation of tea plants caused soil acidification and soil acidity increased with the increase of tea cultivation period. Soil pH of composite samples from cultivated layers decreased by 1.37, 1.62 and 1.85, respectively, after 13, 34 and 54 years of tea plantation, as compared to the surface soil obtained from the unused land. Soil acidification rates at early stages of tea cultivation were found to be higher than those at the later stages. The acidification rate for the period of 0-13 years was as high as 4.40 kmol H⁺ ha^-1 year^-1 for the cultivated layer samples. Soil acidification induced the decrease of soil exchangeable base cations and base cation saturation and thus increased the soil exchangeable acidity. Soil acidification also caused the decrease of soil cation exchange capacity, especially for the 54-year-old tea garden. Soil acidification induced by tea plantation also led to the increase of soil exchangeable Al and soluble Al, which was responsible for the Al toxicity to plants.     

Fluctuations of diptera larvae in soil from a spruce forest in relation to climatic factors

Summary Diptera larvae were extracted by the wash and flotation method according to Healey and Russell-Smith (1970) as modified by Altmüller (1979). The larvae had been kept in alcohol for at least 2 months. After this time their specific gravity changed, and an additional flotation with MgSO₄-water solution of SG = 1.26 g/cm³ was very effective. This new method is described. The working procedure can be reduced to about 50%–70% of the time Altmüller (1979) and Hövemeyer (1984) needed. Many tests have shown that some small sciarid larvae settle out with the needle and humus particles in solution of SG = 1.26 and cannot be found, so that it is necessary to apply a correction factor. Samples taken each August from 1979 to 1984 were extracted and floated off by the methods described. Larvae from seven families of Diptera nematocera and from six families of Diptera brachycera were found. Numbers of sciarid larvae varied between 2500 (1979) and 100/m² (1981), of the cecidomyid larvae between 6700 (1983) and 400/m² (1980) and of the brachyceran larvae between 650 (1979) and 50/m² (1984). The correlation coefficient (= r) of larval population size with temperature and precipitation, respectively, was calculated and hence the coefficient of determination as a percentage (r ² x 100), which represents the proportion of the fluctuations in population size that is accounted for by weather factors. All families were influenced negatively by the temperature and positively by the precipitation in August, i.e., the higher the precipitation and the lower the temperature in August the higher the larval abundance in August. The development of the larvae begins in the previous year, and the influence of monthly climatic factors during the whole period of development was tested. It was shown that: Precipitation is correlated with the abundance of (1) sciarid larvae in June and August of the previous year (positively); (2) brachyceran larvae in June (August) of the previous year and in (February), March, April and August of the same year (positively); and (3) cecidomyid larvae in July of the same year (negatively). Temperature is correlated with the abundance of (1) sciarid larvae in August of the previous year (negatively); (2) brachyceran larvae in August of the previous year (negatively); and (3) cecidomyid larvae in September of the previous year, in January and July of the same year (positively). Monthly data for precipitation and temperature, taken together, showed maximum positive correlations with abundance as follows: (1) for sciarid larvae, with data for August of the previous year; (2) for brachyceran larvae, with data for August of the previous year; (3) for cecidomyid larvae, with data for July of the same year.     

The uncertainty in forecasting trends of forest soil acidification

A Regional Soil Acidification Model (RESAM) has been developed to gain insight in long-term impacts of deposition scenarios on forest soils in The Netherlands. Model predictions of such large-scale environmental effects of acid deposition require extrapolation of site specific data to large geographical regions. The major aim of this study is to quantify the uncertainty in model response to a given deposition scenario, due to uncertainty and spatial variability in data. Furthermore, the uncertainty analysis was performed to determine which additional data will most likely improve the reliability of predictions. An efficient Monte Carlo technique was used in combination with regression analysis. The analysis was restricted to one forest soil ecosystem: a leptic podzol with Douglas fir, subject to a reducing deposition scenario. The investigated output variables were pH, Al/Ca ratio and NH₄/K ratio in the root zone, which are generally used as indicators of forest soil acidification and of potential forest damage. Statistical analyses showed that in most cases the relation between the parameters and model output can be satisfactorily described by a linear regression model. The uncertainty contribution of various parameters depends on the considered output variable, soil compartment and time. The uncertainty, as measured by the coefficient of variation, appears to be high for the NH₄/K and Al/Ca ratios, whereas it was relatively low for the pH. Results show that the uncertainty in the depositions of SO_x, NO_x, and NH_x in a receptor area and the uncertainty in the parameters and variables determining the nitrogen and aluminium dynamics contribute most to the resulting uncertainty of the considered model output.     

Solubility of soil phosphorus as influenced by urea

The objective of this study was to investigate possible ways of mobilizing residual fertilizer P as a result of local pH elevation caused by urea hydrolysis. The response of water-soluble P (P_w) and dissolved organic C (DOC) to urea hydrolysis was monitored in three cultivated soils and at two P levels for up to 127–135 d and compared with corresponding changes in soils limed with Ca(OH)₂. Hydrolysis of urea was complete in 8–15d during which soil pH increased by 1–1.5 units at the maximum. Subsequently, the pH decreased to or below the original level owing to nitrification. Mobilization of soil P was enhanced substantially in parallel with the increase in pH, the peak P_w occurring simultaneously with the highest pH value. In all urea-treated soils, P_w remained at an elevated level for at least 60d. As compared to urea, elevation of soil pH with Ca(OH)₂ had only a minor and inconsistent influence on P_w. In mobilization of soil P, the urea-induced increase in pH and a simultaneous production of NH₄⁺ ions proved to be superior to liming with Ca(OH)₂. It was hypothesized that when an acid soil is amended with urea, phosphate is first displaced by OH^? ions, resulting in elevated solution P concentrations. A simultaneous dissolution of organic matter contributes to the persistence of high P concentration by competition for sorption sites on Fe and Al oxides, and thus retards the resorption of P.     

Carbon mineralization kinetics as influenced by soil properties

In a short-term laboratory study C mineralization potentials were determined on soil samples obtained from some representative agricultural soils in Tuscany, Italy. All the kinetic models tested to describe the mineralization process provided a good fit to the experimental data. A modified first-order model best described C mineralization in the soil. Both potentially mineralizable C and the mineralization rate (k) varied considerably among soils, reflecting the differences in soil properties. Potentially mineralizable C was positively related to C evolved as CO₂ and to the exchange capacity. Normalized values (potentially mineralizable C divided by organic C), representing on average about 2% of the total soil C, was positively correlated to soil pH and negatively to the soil C pool, the soil N pool, and total microbial activity. Values for k ranged between 0.050 and 0.104 day^-1, being higher in fine-textured soils and in soils with a large free Fe content. A low C:N ratio was indicative of a high k value. Turnover times for mineralized C were relatively rapid, ranging from 10 to 20 days.     

Sulphur mineralization kinetics as influenced by soil properties

A 10-week laboratory study, using an open incubation technique, was carried out to determine net sulphur (S) mineralization potentials of soil samples obtained from some representative soils in Tuscany, Italy. The time-course of organic S mineralization in the soils was analyzed by fitting the experimental values to three kinetic models (first-order, first-order E, zero-order). The first-order model was found to be the most suitable because it provided the best fit to the experimental data and for its simplicity. Potentially mineralized S (S ₀) values ranged from a minimum of 13.6 to a maximum of 50.7 mg kg⁻¹ soil and the mineralization rate k varied from 0.111 to 0.615 week⁻¹. It was also positively related to organic C, N, and S, protease, arylsulphatase, and dehydrogenase activities. The mineralization rate did not show any significant relationship with soil properties.     

Nitrous oxide evolution from structurally intact soil as influenced by tillage and soil water content

Among farmers there is a growing interest for adoption of reduced tillage practices, which has accentuated the need to understand the consequences for soil nutrient dynamics and losses. A laboratory study was conducted with structurally intact soil cores collected from two depths, 0–4 and 14–18 cm, within tillage experiments on contrasting soil types, both experiments with soil under mouldboard ploughing (MP) or shallow tillage (ST). The soil cores were adjusted to one of seven matric potentials ranging from ?1500 to ?15 hPa. The extent and regulation of nitrous oxide (N₂O) evolution as a function of tillage, depth and soil characteristics was studied by measurement of N₂O and CO₂ evolution rates, as well as nitrifying and denitrifying potentials, and subsequent data analysis by multiple linear regression models. At both sites, compaction of ST soil below the depth of tillage was significant. The vertical distribution of N₂O evolution was different in MP and ST soil, but no main effect of tillage on N₂O evolution was observed. Effects of soil variables on N₂O evolution were analysed using volumetric water content, water-filled pore space, or relative gas diffusivity (RD) to represent the effect of soil water. Using RD weakened interactions with tillage and C availability and strengthened main effects, suggesting that RD may provide a more general representation of the water effect. At 0–4 cm depth, N₂O evolution was related to NO₃^? availability in the soil with 5.1% C, but to C availability in the soil with 1.5% C. The contrasting patterns of dependencies in the different environments support the interpretation of reduced tillage and soil water content as indirect controls, via diffusional constraints, of N₂O evolution.     

Biological changes in northern spruce forest soil after clear-cutting

In northern Finland, reforestation has frequently failed in clear-cut areas of coniferous forests. These failures prompted an investigation of the changes in the invertebrate fauna and in the bacterial populations of such forest soils after clear-cutting. Clear-cut areas in four neighbouring sites of various ages were sampled monthly, and the results were compared with those for samples taken simultaneously from a control site in an untreated spruce stand. After clear-cutting, the total biomass of the invertebrate fauna showed a strong increase, mainly due to an increase of the Enchytraeidae populations. The biomass reached its maximum after 7 yr and returned to the original level by year 13 after clear-cutting. Bacterial counts showed the same pattern as the faunal biomass; the numbers at first increased after clear-cutting, then regressed, and approached the control value after 13 yr. Cellulose degradation and soil respiration behaved in the same way. Bacterial numbers showed a significant seasonal variation at all sites, including the control; counts were maximal after the snow melt in June and decreased during the growing season.     

Liming induces growth of a diverse flora of ammonia-oxidising bacteria in acid spruce forest soil as determined by SSCP and DGGE

The autotrophic ammonia-oxidising bacterial (AOB) community composition was studied in acid coniferous forest soil profiles at a site in southwestern Sweden 6 years after liming. Liming caused a significant increase in pH in the organic horizons, while the mineral soil was unaffected. The AOB communities were studied by single-strand conformation polymorphism (SSCP) in parallel with denaturing gradient gel electrophoresis (DGGE) analysis of partial 16S rRNA genes amplified by PCR using primers reported to be specific for β-Proteobacteria AOB, followed by nucleotide sequencing. High genetic diversity of Nitrosospira-like sequences was found in the limed soil profiles, whereas no AOB-like sequences were detected in the control soil at any depth, according to both the SSCP and DGGE analyses. This clearly showed that liming induced growth of a diverse flora of AOB at this forest site. Both Nitrosospira cluster 2 and cluster 4 sequences were present in the limed soil profiles, regardless of soil pH, but we found a higher number of sequences affiliated with cluster 4. The high lime dose seemed to affect the AOB community more than the low dose, and its effects reached deeper into the soil profile. Seven different Nitrosospira-like sequences were found 10 cm under the litter layer in the soil limed with the high dose, but only two in the soil amended with the low lime dose.