Acid Forest Soils Research Articles

Tree species affect cation exchange capacity (CEC) and cation binding properties of organic matter in acid forest soils

Soil organic matter (SOM) in forest soil is of major importance for cation binding and acid buffering, but its characteristics may differ among soils under different tree species. We investigated acidity, cation exchange properties and Al bonding to SOM in stands of Scots pine, pedunculate oak, Norway spruce, European beech and common hornbeam in southern Poland. The content of total carbon (Ct) was by far the major contributor to total cation exchange capacity (CECt) even in loamy soils and a strong relationship between Ct and CECt was found. The slope of the regression of CECt to Ct increased in the order hornbeam≈oak<beech<spruce≈pine, suggesting that the number of negatively charged sites of SOM at any value in the acid pH range was smallest for hornbeam and oak, and largest for spruce and pine soils. This was supported by the apparent dissociation constant (pKapp) values of SOM, which were largest in soils under oak. The maximum values of Al saturation were similar between the stands. However, maximum Al bonding to SOM occurred at higher pH values in soils under pine and spruce than under oak. Therefore, at any value in the acid pH range, the SOM in pine soil has less Al complexed and more adsorbed H+ than SOM from oak soils. Such differences in Al and H bonding are not only important for pH buffering and metal solubility controls, but also for stabilization of SOM via saturation of functional groups by Al and H.

Ammonia oxidation is not required for growth of Group 1.1c soil Thaumarchaeota.

Thaumarchaeota are among the most abundant organisms on Earth and are ubiquitous. Within this phylum, all cultivated representatives of Group 1.1a and Group 1.1b Thaumarchaeota are ammonia oxidizers, and play a key role in the nitrogen cycle. While Group 1.1c is phylogenetically closely related to the ammonia-oxidizing Thaumarchaeota and is abundant in acidic forest soils, nothing is known about its physiology or ecosystem function. The goal of this study was to perform in situ physiological characterization of Group 1.1c Thaumarchaeota by determining conditions that favour their growth in soil. Several acidic grassland, birch and pine tree forest soils were sampled and those with the highest Group 1.1c 16S rRNA gene abundance were incubated in microcosms to determine optimal growth temperature, ammonia oxidation and growth on several organic compounds. Growth of Group 1.1c Thaumarchaeota, assessed by qPCR of Group 1.1c 16S rRNA genes, occurred in soil, optimally at 30°C, but was not associated with ammonia oxidation and the functional gene amoA could not be detected. Growth was also stimulated by addition of organic nitrogen compounds (glutamate and casamino acids) but not when supplemented with organic carbon alone. This is the first evidence for non-ammonia oxidation associated growth of Thaumarchaeota in soil.

Comparative Effects of Lime and Phosphorus Sources on Nutrients Uptake and Yield of Maize in a Tropical Ultisol

Ultisols are acid forest soils of low fertility status formed from intense weathering and leaching processes in the humid temperate and tropical regions. Sustainable crop production on these soils where phosphorus (P) deficiency is a main constraint aims at maintaining high crop yields by enhancing nutrients availability and uptake efficiency. This study was carried out at the Faculty of Agriculture, University of Ibadan to compare nutrients uptake and yield among maize plants grown from an ultisol with either sole or combined amendments of lime (L), rock phosphate (RP) and organomineral fertilizer (OMF). Eight treatment combinations: control, L, RP, OMF, L+ RP, L+OMF, RP+OMF and L+RP+OMF, each supplying 200kg P/ha and/or 1.0t/ha of L were replicated three times in a Complete Randomized Design. Crops grown in the RP+OMF amended soil (AMS) took up the highest concentrations of Ca, Zn, Mn and Fe. These were followed by the uptake of Ca and Mn from the L+RP AMS with the highest uptake of Mg. Next were those produced from the OMF AMS for Mg, Ca, Mn with the uptake of Zn and Fe only second to those in the RP+OMF AMS. Maize produced at 4 weeks after sowing from the OMF and L+RP AMS took up relatively higher

氨基酸添加对亚热带森林红壤氮素转化的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 氨基酸添加对亚热带森林红壤氮素转化的影响 DOI: 10.5846/stxb201405110957 作者: 作者单位: 湿润亚热带生态地理过程省部共建教育部重点实验室,湿润亚热带生态地理过程省部共建教育部重点实验室,湿润亚热带生态地理过程省部共建教育部重点实验室,湿润亚热带生态地理过程省部共建教育部重点实验室,湿润亚热带生态地理过程省部共建教育部重点实验室 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目(40901115,41271282,31070549,31170578);教育部创新团队项目(IRT0960);福建省高校杰出青年科研人才培育计划(JA12058)和福建师范大学优秀青年骨干教师培养基金资助(fjsdjk2012069) Effects of amino acid additions on nitrogen transformation in subtropical forest soil Author: Affiliation: Key Laboratory of Humid Subtropical Eco-geographical Process of the Ministry of Education,Fujian Normal University,Key Laboratory of Humid Subtropical Eco-geographical Process of the Ministry of Education,Fujian Normal University,Key Laboratory of Humid Subtropical Eco-geographical Process of the Ministry of Education,Fujian Normal University,Key Laboratory of Humid Subtropical Eco-geographical Process of the Ministry of Education,Fujian Normal University,Key Laboratory of Humid Subtropical Eco-geographical Process of the Ministry of Education,Fujian Normal University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为探究氨基酸氮形态对亚热带土壤氮素含量及转化的影响,选择建瓯市万木林保护区的山地红壤为对象,采用室内培养实验法,通过设计60%和90% WHC两种土壤含水量并添加不同性质氨基酸,测定了土壤中铵态氮、硝态氮、可溶性有机氮的含量和氧化亚氮的释放量,分析了可溶性有机碳、土壤pH值的大小变化及其与氮素的相互关系。结果表明:与对照处理相比,氨基酸添加显著增加了土壤NH4+-N含量并使土壤pH值升高,且在一定程度上解除了高含水量(90% WHC)对NH4+-N产生的抑制,其中甲硫氨基酸的效果最为明显。酸性、碱性、中性氨基酸对土壤NO3--N含量和N2O释放影响不显著,但甲硫氨基酸可显著抑制土壤硝化从而导致NH4+-N的积累,并在培养前期抑制土壤N2O产生而在培养后期促进N2O释放,总体上促进N2O释放。60% WHC的氨基酸添加处理较90% WHC条件下降低土壤可溶性有机氮的幅度更大。氨基酸对土壤氮素转化的影响与带电性关系较小,而可能与其分解产物密切相关。可见,不同性质氨基酸处理对森林土壤氮素含量及转化存在不同程度的影响,且甲硫氨基酸对土壤氮素转化的影响机理值得深入研究。 Abstract:Research on the nitrogen cycle of forest soils has traditionally focused on the mechanisms regulating the turnover of inorganic N. However, the key role of organic N in soil nitrogen transformation tends to be overlooked. Over recent decades, researchers have assessed the relative importance of organic N on the nutritional requirements of plants in forest ecosystems. Most studies have revealed that soil amino acids are important sources of organic N in forest ecosystems. Although the fluxes of organic N in forest ecosystems have been studied in detail, we have a poor understanding about the role of amino acids in soil nitrogen transformation in the subtropical region of China. In this study, subtropical broad-leaved forest soil was collected from Wan Mulin Natural Reserve located at Fujian Province, southeast China. We selected four types of amino acids, including L-Glutamic acid, L-Lysine, L-Alanine, and L-Methionine as the study materials, which represented acidic, basic, neutral, and sulfur amino acids, respectively. Soils were incubated for 0, 2, 8, 12, 16, and 36 days in the laboratory after adding 0 and 40 mg N /kg amino acid. Soil moisture was maintained at 60% WHC (water-holding capacity) or 90% WHC. Ammonium N, nitrate N, soluble organic N, nitrous oxide, soil pH, and soluble organic C content were determined. Data were subjected to analysis of variance (ANOVA) with the SPSS version 18.0, and significant differences between treatments were compared by the LSD test at P < 0.05.The results showed that soil NH4+-N content significantly increased with the addition of amino acids, with the repression of NH4+-N production under high soil moisture content conditions (90% WHC) being relieved to some extent. Soil pH was increased by the addition of amino acids, and was closely correlated with soil NH4+-N and NO3--N. These results support the finding that an increase in soil pH may promote N mineralization in acidic forest soils. Acidic, basic, and neutral amino acids increased NH4+-N production in soil, but had little or no influence on NO3--N production and nitrous oxide emission. Soil nitrification was significantly inhibited by the addition of methionine, resulting in the accumulation of NH4+-N. Nitrous oxide emission from soil as a whole increased with the addition of methionine. The decrease in SON under the amino acid treatments was more evident under 60% WHC than 90% WHC conditions. The turnover of amino acids in forest soil is very rapid, with NH4+-N being the major N form in soil. Nitrogen transformation in forest soil is probably related to the decomposed products of amino acid mineralization, rather than the charge of amino acids. These findings indicate that nitrogen transformation varies with amino acid type, and that the mechanism inhibiting methionine during nitrification needs further research. In conclusion, amino acids might represent the intermediate products between organic nitrogen and mineral nitrogen, regulating nitrogen transformation in forest soils. 参考文献 相似文献 引证文献

Research on acidification in forest soil driven by atmospheric nitrogen deposition

Soil acidification is defined as the process in which exchangeable cations are leaching and soil H+ concentration is raising thereby increases soil acidity. Changes in soil pH value and acid neutralizing capacity are mainly indicators of soil acidification. Soil acidification is considered to be a serious ecological and environmental issue, which not only reduces soil quality, but also decreases biodiversity of forest ecosystem and induces forest decline. With nitrogen (N) deposition rapidly increasing, its contribution to soil acidification becomes a major concern in the world. However, the impact of increased N deposition on soil acidification is not well addressed highlighting the need for further attention to the issue. In this paper, the studies on forest soil acidification induced by N deposition were reviewed. The factors related to soil acidification driven by N deposition were classified and discussed, which included soil acidic buffering capacity, N components in atmospheric N deposition, climate, plant species in forests, and N status in ecosystem. Iron (Fe) buffering phase and the consequent Fe toxicity occurring to the acidified soil caused by high N deposition were concerned. The scarcity of phosphorus (P) element induced by soil acidification was particularly emphasized. The research methods used to study soil acidification driven by N deposition were also evaluated. In the end we stressed the importance of the study on soil acidification especially in tropical and subtropical regions driven by N deposition and its mechanisms. This paper can serve for maintaining sustainable forest and agricultural ecosystems.

Effect of liming and organic and inorganic fertilization on soil carbon sequestered in macro-and microaggregates in a 17-year old Pinus radiata silvopastoral system

Agroforestry systems have been recognized as a potential greenhouse gas mitigation strategy under the Kyoto Protocol because of their ability to absorb carbon dioxide from the atmosphere and store carbon mainly in the soil. Soil particle size and land management practices are known to have a considerable influence on carbon storage in soils. This study evaluated changes in soil chemical and physical properties, and quantified and compared the amount of C stored in the bulk soil and in three different soil fractions (250–2000, 53–250 and <53 μm) at each of four soil depths (0–25, 25–50, 50–75 and 75–100 cm) in a silvopastoral system located on an acidic forest soil under Pinus radiata D. Don. Areas of this system were subjected ten years ago to one of nine fertilization treatments: three different doses of sewage sludge or no fertilization, all with or without the addition of lime, and mineral fertilizer with no liming. Seventeen years after reforestation and seven years after canopy closure, strong gradients with soil depth were found regarding soil bulk density, pH and carbon storage. Intense soil management (high doses of sewage sludge and liming) generally reduced soil carbon storage, mainly in coarse aggregates, but this could be compensated by the increase in tree and pasture development observed in soils subject to intermediate sewage sludge doses.

Organic nitrogen stimulates the heterotrophic nitrification rate in an acidic forest soil

Many previous studies have demonstrated that heterotrophic nitrification processes play an important role in the production of NO3− in acidic soils. However, it is not clear whether a low concentration of nitrogenous organic compounds support heterotrophic nitrification processes in natural soils. In this study, we performed an 15N tracer experiment with a glycine concentration gradient (20, 40, 80, and 160 mg Nkg−1) to investigate the effect of the organic nitrogen concentration on the heterotrophic nitrification rate and its relative contribution to the total nitrification of the studied acidic forest soil. This experiment demonstrated that 15N–NO3− accumulated over time with all nitrogen treatments in the presence of acetylene, confirming that heterotrophic nitrification occurred even at a low organic nitrogen concentration (20 mg kg−1) in the studied acidic forest soil. In the presence of acetylene, the 15N–NO3− concentration in the 20 and 40 mg kg−1 glycine-N treatments was significantly lower than in the 80 and 160 mg kg−1 glycine-N treatments (p < 0.05), indicating that a high organic nitrogen concentration stimulated the heterotrophic nitrification rate. There was no significant difference in the average contribution of heterotrophic nitrification to total nitrification among the different nitrogen treatments, suggesting that the organic nitrogen concentration did not affect the relative contribution of heterotrophic nitrification to total nitrification in the studied acidic soil. Our results confirmed that a low concentration of organic N (20 mg kg−1) supported heterotrophic nitrification in the studied soil. The organic nitrogen concentration stimulates the heterotrophic nitrification rate, but does not affect the relative contribution of heterotrophic nitrification to total nitrification in the studied acidic soil.

Conversion of forest to agricultural land affects the relative contribution of bacteria and fungi to nitrification in humid subtropical soils

Land-use and management practices can affect soil nitrification. However, nitrifying microorganisms responsible for specific nitrification process under different land-use soils remains unknown. Thus, we investigated the relative contribution of bacteria and fungi to specific soil nitrification in different land-use soils (coniferous forest, upland fields planted with corn and rice paddy) in humid subtropical region in China. 15N dilution technique in combination with selective biomass inhibitors and C2H2 inhibition method were used to estimate the relative contribution of bacteria and fungi to heterotrophic nitrification and autotrophic nitrification in the different land-use soils in humid subtropical region. The results showed that autotrophic nitrification was the predominant nitrification process in the two agricultural soils (upland and paddy), while the nitrate production was mainly from heterotrophic nitrification in the acid forest soil. In the upland soils, streptomycin reduced autotrophic nitrification by 94%, whereas cycloheximide had no effect on autotrophic nitrification, indicating that autotrophic nitrification was mainly driven by bacteria. However, the opposite was true in another agricultural soil (paddy), indicating that fungi contributed to the oxidation of NH4+ to NO3−. In the acid forest soil, cycloheximide, but not streptomycin, inhibited heterotrophic nitrification, demonstrating that fungi controlled the heterotrophic nitrification. The conversion of forest to agricultural soils resulted in a shift from fungi-dominated heterotrophic nitrification to bacteria- or fungi-dominated autotrophic nitrification. Our results suggest that land-use and management practices, such as the application of N fertilizer and lime, the long-term waterflooding during rice growth, straw return after harvest, and cultivation could markedly influence the relative contribution of bacteria and fungi to specific soil nitrification processes.

Assessment of the bioavailability and toxicity of lead polluted soils using a combination of chemical approaches and bioassays with the collembolan Folsomia candida

Understanding bioavailability and toxicity is essential for effective ecological assessment of contaminated soils. Total, water and 0.01M CaCl2 extractable and porewater Pb concentrations and soil properties in different shooting field soils were investigated. Three artificial soils containing different pH and organic matter contents and two natural soils were included as controls. Survival, reproduction and avoidance responses of Folsomia candida exposed to these soils as well as internal Pb concentrations were measured. In the shooting range soils, total Pb concentrations were 47–2398mg/kgdw, pHCaCl2 3.2–6.8 and organic matter content 3.8–7.0%. Pb concentrations in F. candida linearly increased with increasing Pb concentrations in the soils. Acid forest soils caused significantly higher collembolan mortality and avoidance responses and significantly lower reproduction than the neutral grassland soils, which could be attributed to differences in pH and especially CaCl2 extractable Pb concentrations. Soil properties significantly affected bioavailability and toxicity of Pb, but overall the collembolans seemed more sensitive to pH than to Pb in soils. This study shows the importance of selecting proper reference soils for assessing the effects of field soils.

Characterization and Biodegradation Rates of Tall Oil Soaps in Different Water and Soil Environments

Biodegradation of different tall oil soaps was studied in order to examine the behaviour of these bioproducts in natural environments and to study their biodegradation rates. The rates of biodegradation were studied by modelling the biodegradation phenomenon as a pseudo-first-order reaction. Biodegradation was studied in seven different environments. Four of these were water phases: groundwater in aerobic and anaerobic conditions, river water and Office of Environmental Compliance and Documentation (OECD) 301 F standard conditions. In addition, three solid phases, sand, acidic forest soil and topsoil, were used as a solid matrix. The results showed that the matrix and the concentration had a strong effect on both the rate and degree of the biodegradation reaction. As a result, all of the tall oil soaps were about 57–85 % biodegradable in OECD 301 F conditions, but only moderately biodegradable in Finnish river water taken in the summer. When compared to the sample taken in the autumn, the biodegradation degree was considerably higher. In groundwater, biodegradation degree was low, even negligible in anaerobic conditions. With ten times less sample content, the biodegradation degrees in groundwater and surface water increased to 60 % for all the tall oil soaps, with one soap, in particular, up to 80 % during 100 days of measurement. In the topsoil, biodegradation was vague, and in slightly acidic forest soil, the decomposition reactions were complex. This is probably due to gas formation in the side reactions. In sand, tall oil soaps did not biodegrade at all.

Effect of metal oxide on surface area and pore size of water-dispersible colloids from three German silt loam topsoils

The surface area and pore structure of easily dispersed soil particles <2μm in size (water-dispersible colloids, WDCs) are important for carbon sequestration and transport in soil, two processes which are essential for the terrestrial carbon cycling. In this work, we determine the effects of dithionite–citrate–bicarbonate (DCB) extractable metal oxides, and oxalate extractable metal oxides on the specific surface area (SSA) and pore structure of WDCs from silt loam topsoils of three TERENO test sites with a similar clay content (20%) in Germany (arable (Selhausen), grassland (Rollesbroich) and forest (Wuestebach) soils). The N2 gas-adsorption (−196°C), small-angle X-ray scattering (SAXS), dynamic light scattering (DLS) and microelectrophoretic (ME) methods were used and compared. Results show that 1) the SSA of the WDCs from Selhausen, Rollesbroich, and Wuestebach decreased more after DCB treatment (27%, 35%, and 44%) than after oxalate treatment (5%, 14%, and 22%). DCB removed metal oxide nanoparticles from WDCs were found to have diameters (dp) ranging from 4nm to 8nm and the surface loading ratios on the surface of aluminosilicate residues in WDCs were estimated to be 11% to 22% for three soils where the highest value was found in the acidic forest soil. 2) Pore sizes in the mesopore range (2nm to 50nm) were analyzed in the WDC fractions. The results were discussed in terms of accessible open pores for the pristine WDCs and WDC samples from which metal oxide nanoparticles and organic carbon (OC) had been removed. The lower average pore radius (Rp) measured by the N2 gas-adsorption method based on the total volume (Vt) to SSA ratio variations in WDCs without metal oxides compared to WDC with metal oxides indicated a contraction of the porous structure of WDCs due to the presence of metal oxide nanoparticles. The pore size distribution (PSD) analysis showed a sensitive contribution of metal oxide nanoparticles in the low range of pore sizes (<25nm) of WDCs. In SAXS measurements, higher surface fractal dimensions (Ds) were observed in WDCs before the metal oxide's removal, which supports a roughness increase of the interfaces in the presence of nanoparticles. The colloidal characterization of WDCs by the DLS and ME methods shows, at a μm scale, the role of positively charged metal oxide nanoparticles in forming WDCs with a more compact structure by decreasing the particle size (dz) and the negative zeta potential (ζ). 3) The comparison of Rp, k, dz and dp results between different soils also indicates the dependence on the clay mineralogy of WDCs so that the heterocoagulation between kaolinite and illite (clay minerals of different aspect ratios) increases the size of soil mesopores (Rollesbroich). In conclusion, the results of this study clearly show that the combination of the N2 gas-adsorption, SAXS, DLS and ME methods allows the characterization of soil porosity in the nanometer range where metal oxide nanoparticles contribute to a more compact structure of WDC.

Can shrub species with higher litter quality mitigate soil acidification in pine and oak forests on poor sandy soils?

This study, aiming to unravel whether topsoil conditions under tree species with nutrient-poor leaf litter can be altered by admixing a shrub layer, was performed in 12 pine (mainly Pinus sylvestris) and 12 oak (Quercus robur) stands on sandy podzolic soils in north-east Belgium. We examined the effects of presence of a shrub layer on forest floor mass and topsoil chemical properties related to soil acidification. The shrub species included were European rowan (Sorbus aucuparia), alder buckthorn (Rhamnus frangula) and black cherry (Prunus serotina). For each tree species, 60–90years old stands were selected containing shrubs present in varying cover classes: sparse (<20%), intermediate (20–70%) and dense (>70%). The oak stands were characterized by less but ‘nutrient-richer’ litterfall, compared to the pine stands. This was reflected in less humus build-up (FH-horizon) and higher pH, CEC, BS and lower C/N in the topsoil in the oak stands compared to the pine stands. However, despite the fact that the shrubs produced litter with significantly higher base cation and N concentrations than that of the studied tree species, we did not find any significant changes in topsoil conditions in the pine and oak stands under study, even under dense shrub layers (87–91% cover).

Nitrogen deposition contributes to soil acidification in tropical ecosystems.

Elevated anthropogenic nitrogen (N) deposition has greatly altered terrestrial ecosystem functioning, threatening ecosystem health via acidification and eutrophication in temperate and boreal forests across the northern hemisphere. However, response of forest soil acidification to N deposition has been less studied in humid tropics compared to other forest types. This study was designed to explore impacts of long-term N deposition on soil acidification processes in tropical forests. We have established a long-term N-deposition experiment in an N-rich lowland tropical forest of Southern China since 2002 with N addition as NH4 NO3 of 0, 50, 100 and 150kg Nha(-1) yr(-1) . We measured soil acidification status and element leaching in soil drainage solution after 6-year N addition. Results showed that our study site has been experiencing serious soil acidification and was quite acid-sensitive showing high acidification (pH(H2O) <4.0), negative water-extracted acid neutralizing capacity (ANC) and low base saturation (BS,< 8%) throughout soil profiles. Long-term N addition significantly accelerated soil acidification, leading to depleted base cations and decreased BS, and further lowered ANC. However, N addition did not alter exchangeable Al(3+) , but increased cation exchange capacity (CEC). Nitrogen addition-induced increase in SOC is suggested to contribute to both higher CEC and lower pH. We further found that increased N addition greatly decreased soil solution pH at 20cm depth, but not at 40cm. Furthermore, there was no evidence that Al(3+) was leaching out from the deeper soils. These unique responses in tropical climate likely resulted from: exchangeable H(+) dominating changes of soil cation pool, an exhausted base cation pool, N-addition stimulating SOC production, and N saturation. Our results suggest that long-term N addition can contribute measurably to soil acidification, and that shortage of Ca and Mg should receive more attention than soil exchangeable Al in tropical forests with elevated N deposition in the future.

The substrate is an important factor in controlling the significance of heterotrophic nitrification in acidic forest soils

In this study, a 15N tracer experiment was carried out to investigate the relative availability of different nitrogen (N) substrates for heterotrophic nitrifiers and to determine the significance of heterotrophic nitrification in two acidic forest soils in eastern China. Five 15N labeled substrates were applied, i.e. Glycine (4.90 atom% 15N excess), l-glutamic acid (4.89 atom% 15N excess), maize straw (3.63 atom% 15N excess), (NH4)2SO4 (4.97 atom% 15N excess), and control and were incubated for 4 days without or with C2H2 at 1 KPa (1%) in laboratory. The results showed that accumulation of 15N-NO3− significantly increased with the incubation time in all 15N labeled treatments in the presence of acetylene, indicating that NO3− produced from heterotrophic nitrification convincingly occurred and heterotrophic nitrifiers could use both ammonium and organic N compounds substrates for nitrification in the studied soils. The 15N-NO3− production in the Glycine and l-glutamic acid treatments in the presence of acetylene was obviously higher than that in the (NH4)2SO4 and maize straw treatments (p < 0.05), indicating availability of N substrates for heterotrophic nitrifiers was different. The heterotrophic nitrification of amino organic N compounds could occur via a combined organic and inorganic pathway. However, for complicated organic N substrate, e.g. maize straw in this study, almost all 15N-NO3− was produced by organic N pathway. The contribution of heterotrophic nitrification to total nitrification varied from 23% to 93% in the different N substrate treatments as follows: (NH4)2SO4 < amino acid < maize straw. The substrate was an important factor in controlling the significance of heterotrophic nitrification in acidic forest soils.

Effects of calcite and magnesite application to a declining Masson pine forest on strongly acidified soil in Southwestern China

Liming of strongly acidified soil under a Masson pine (Pinus massoniana Lamb.) forest was studied through a seven-year field manipulation experiment at Tieshanping, Chongqing in Southwestern China. To distinguish between the individual effects of Ca2+ and Mg2+ addition, we separately applied calcite (CaCO3) and magnesite (MgCO3), rather than using dolomite [CaMg(CO3)2]. Both calcite and magnesite additions caused a significant increase in pH and a decrease in dissolved inorganic monomeric aluminium (Ali) concentration of soil water. Ecological recovery included increases of herb biomass (both treatments) and Mg content in Masson pine needles (magnesite treatment only). However, the growth rate of Masson pine did not increase under either treatment, possibly because of nutrient imbalance due to phosphorus (P) deficiency or limited observation period. In China, acid deposition in forest ecosystems commonly coincides with large inputs of atmogenic Ca2+, both enhancing Mg2+ leaching. Calcite addition may further decrease the Mg2+ availability in soil water, thereby exacerbating Mg2+ deficiency in the acidified forest soils of southern and southwestern China. The effect of anthropogenic acidification of naturally acid forest soils on P availability needs further study.

Effects of temperature change and tree species composition on N2O and NO emissions in acidic forest soils of subtropical China

Tree species and temperature change arising from seasonal variation or global warming are two important factors influencing N2O and NO emissions from forest soils. However, few studies have examined the effects of temperatures (5–35°C) on the emissions of forest soil N2O and NO in typical subtropical region. A short-term laboratory experiment was carried out to investigate the influence of temperature changes (5–35°C) on soil N2O and NO emissions under aerobic conditions in two contrasting (broad-leaved and coniferous) subtropical acidic forest types in China. The results showed that the temporal pattern of N2O and NO emissions between the three lower temperatures (5°C, 15°C, and 25°C) and 35°C was significantly different for both broad-leaved and coniferous forest soils. The effects of temperature on soil N2O and NO emission rates varied between broad-leaved and coniferous forest soils. Both N2O and NO emissions increased exponentially with an increase in temperature in the broad-leaved forest soil. However, N2O and NO emissions in the coniferous forest soil were not sensitive to temperature change between 5°C and 25°C. N2O and NO emission rates were significantly higher in the broad-leaved forest soil as compared with the coniferous forest soil at all incubation temperatures except 5°C. These results suggest that the broad-leaved forest could contribute more N2O and NO emissions than the coniferous forest for most of the year in the subtropical region of China.

Characterization and evolution of dissolved organic matter in acidic forest soil and its impact on the mobility of major and trace elements (case of the Strengbach watershed)

Dissolved Organic Carbon (DOC) plays an important role in the behavior of major and trace elements in the soil and influences their transfer from soil to soil solution. The first objective of this study is to characterize different organic functional groups for the Water Extractable Organic Carbon (WEOC) fractions of a forest soil as well as their evolution with depth. The second objective is to clarify the influence of these organic functional groups on the migration of the trace elements in WEOC fractions compared to those in the soil solution obtained by lysimeter plates. All experiments have been performed on an acidic forest soil profile (five depths in the first meter) of the experimental spruce parcel in the Stengbach catchment.The Infra-red spectra of the freeze-dried WEOC fractions show a modification of the molecular structure with depth, i.e. a decrease of the polar compounds such as polysaccharides and an increase of the less polar hydro-carbon functional groups with a maximum value of the aromaticity at 30cm depth. A Hierarchical Ascending Classification (HAC) of the evolution of Water Extractable Chemical Elements (WECE) with the evolution of the organic functional groups in the organic matter (OM) enriched soil compartments permits recognition of relationships between trace element behavior and the organic functional group variations. More specifically, Pb is preferentially bound to the carboxylic acid function of DOC mainly present in the upper soil compartment and rare earth elements (REE) show similar behavior to Fe, V and Cr with a good affinity to carboxy-phenolic and phenolic groups of DOC. The experimental results show that heavy REE compared to light REE are preferentially bound to the aromatic functional group. This different behavior fractionates the REE pattern of soil solutions at 30cm depth due to the here observed aromaticity enrichment of DOC. These different affinities for the organic functional groups of the DOC explain some aspects of the behavior of trace elements in soil solutions and in the soil profile but, also the competition between trace elements in complexation with DOC. The results of this study are important for the understanding of the mobility and the migration of pollutants (as heavy metals or radionuclides) as well as nutrients in natural ecosystems.

The biological activity of soil in Norway spruce forests and in fern Athyrium distentifolium Tausch ex Opiz stands on deforested polluted sites in the Beskydy Mts.

The study is focussed on the biological activity of acid forest soil with aim to characterize some of its parameters. Activity of acidic soil phosphatase, basal and potentional respiration were compared and viable plate counts of microorganism colonies were evaluated. The soils of the Kněhyně region in the Moravian-Silesian Beskids Mts. are intensively influenced by acid deposition. They were sampled from area where often occurrence of fernAthyrium distentifoliumTausch ex Opiz was recorded. Above mentioned characteristics (values of parameters) were determined in soil samples collected in fern stands (close to the periphery of fern individuals with rich root system), from site between individual ferns and from the rest of neighbouring spruce community without distinct herbage layer. In majority of studied cases, increased values of all monitored parameters were found in space ofA. distentifoliumroots accumulated close by fern base. Bare soil between individual fern plants often shows on a lower biological soil activity, however these differences were mostly not statistically significant. On the contrary, values of studied soil parameters recorded in the rest of neighbouring forest community without distinct herbage layer, reached mostly the lowest values and they often differ significantly from values assessed in soil taken near theA. distentifoliumroots.

Different temperature sensitivity and kinetics of soil enzymes indicate seasonal shifts in C, N and P nutrient stoichiometry in acid forest soil

Acid forest soils in the Bohemian Forest in Central Europe are biogeochemically imbalanced in organic C, N and P processing. We hypothesized that these imbalances can be due to different temperature sensitivities of soil enzyme activities and their affinities to substrate in litter and organic soil horizons. We measured potential activities of five main soil enzymes (β-glucosidase, cellobiohydrolase, Leu-aminopeptidase, Ala-aminopeptidase, and phosphatase) responsible for organic carbon, nitrogen and phosphorus acquisition. We also modeled potential in situ enzyme activities and nutrient release based on continuous in situ temperature measurements. We determined basic kinetic parameters (Km, Vmax), enzyme efficiencies (kcat) and temperature sensitivities (Ea and Q10) according to Michaelis–Menten kinetic and modified Arrhenius models. Our results showed significant differences in substrate affinities between the litter and organic soil horizons. Higher aminopeptidase affinity (lower Km) in the litter soil horizon can lead to leaching of peptidic compounds to lower soil horizons. β-Glucosidase and phosphatase showed high temperature response following the Arrhenius model. However, both aminopeptidases showed no or even decreased activity with increasing temperature. The aminopeptidase temperature insensitivity means that peptidic compounds are degraded at the same or even lower rate in warmer and colder periods of the year in acid forest soils. This imbalance results in different release of available nutrients from plant litter and soil organic matter which may affect bacterial and fungal community composition and nutrient leaching from these ecosystems.

Mechanisms for the retention of inorganic N in acidic forest soils of southern China

The mechanisms underlying the retention of inorganic N in acidic forest soils in southern China are not well understood. Here, we simultaneously quantified the gross N transformation rates of various subtropical acidic forest soils located in southern China (southern soil) and those of temperate forest soils located in northern China (northern soil). We found that acidic southern soils had significantly higher gross rates of N mineralization and significantly higher turnover rates but a much greater capacity for retaining inorganic N than northern soils. The rates of autotrophic nitrification and NH3 volatilization in acidic southern soils were significantly lower due to low soil pH. Meanwhile, the relatively higher rates of NO3− immobilization into organic N in southern soils can counteract the effects of leaching, runoff, and denitrification. Taken together, these processes are responsible for the N enrichment of the humid subtropical forest soils in southern China.