Carbon Isotope Composition, Macronutrient Concentrations, and Carboxylating Enzymes in Relation to the Growth of Pinus halepensis Mill. When Subject to Ozone Stress

We present here the effects of ambient ozone (O₃)-induced decline in carbon availability, accelerated foliar senescence, and a decrease in aboveground biomass accumulation in the Aleppo pine (Pinus halepensis Mill.). Aleppo pine seedlings were continuously exposed in open-top chambers for 39 months to three different types of O₃ treatments, which are as follows: charcoal-filtered air, nonfiltered air (NFA), and nonfiltered air supplemented with 40 ppb O₃ (NFA+). Stable carbon isotope discrimination (??) and derived time-integrated c _i/c _a ratios were reduced after an accumulated ozone exposure over a threshold of 40 ppb (AOT40) value from April to September of around 20,000 ppb·h. An AOT40 of above 67,000 ppb·h induced reductions in ribulose-1,5-biphosphate carboxylase/oxygenase activity, aboveground C and needle N and K concentrations, the C/N ratio, Ca concentrations in twigs under 3 mm, and the aerial biomass, as well as increases in needle P concentrations and phosphoenolpyruvate carboxylase (PEPC) activity and the N and K concentrations in twigs under 3 mm. Macronutrients losses, the limitations placed on carbon uptake, and increases in catabolic processes may be the causes of carbon gain diminution in leaves which was reflected as a reduction in aboveground biomass at tree level. Stimulation of PEPC activity, the consequent decreased ??, and compensation processes in nutrient distribution may increase O₃ tolerance and might be interpreted as part of Aleppo pine acclimation response to O₃.     

Bush bean (Phaseolus vulgaris L) leaf injury,photosynthesis and stomatal functions under elevated ozone levels

Three bush bean cultivars (Lit, Groffy and Stella) were grown under four levels of ozone exposure (ambient air+50 ppb O₃ ambient air+25 ppb O₃, ambient air and charcoal filtered air) in open- top chambers. Number and leaf injury statistics showed significant reduction in the number of healthy leaves as the level of O₃ increased. The area based leaf injury percentages of the cvs. Lit, Groffy and Stella were 69.8, 57.9 and 71.1% at the highest O₃ level, 24.1, 19.6 and 30.3% at the 2nd highest O₃ level, and 4.5, 0.7 and 5.6% at the ambient air, respectively. The plants grown in the filtered air revealed no injury symptoms. The stomatal conductances were found to decrease gradually in each cultivar as the O₃ level increased. At the highest O₃ level, Chlorophyll fluorescence measurements on the 2nd leaf from the top on 24th day of exposure resulted in significantly the highest Fv/Fm values, the lowest f₀ and the highest F_m values whereas the 4th leaf showed the smallest Fm and correspondingly the smallest F_v/F_m values. This is an indication of photosystem II damage after accumulation of a high ozone dose in the 4th leaf. The photosynthetic rate of the 2nd leaf measured on 30th day of exposure was comparatively higher at the highest exposure but the data taken from the same leaf on 40th day of exposure showed significantly lower photosynthetic rate than the plants in ambient air. Both chlorophyll fluorescence and photosynthetic measurements indicated that ozone stressed leaves experience a stimulation of photosynthesis (possibly due to increased assimilate demand) prior to irreversible damage. Bush bean leaves need to accumulate a critical ozone dose(an AOT40 of presumably > 18 ppm-h) for reduction of the photosynthetic capacitys.     

The Relative Sensitivity of Different Mediterranean Plant Species to Ozone Exposure

An experimental study was performed in open-top chambers to assess the relative O₃-sensitivity of the following Mediterranean woody plants: Quercus ilex ssp. ilex, Quercus ilex ssp. ballota, Olea europaea ssp. sylvestris, Ceratonia siliqua and Arbutus unedo. Assessment of O₃ ‘sensitivity’ was based on the development of O₃-induced visible injury and the extent of the reduction in relative growth rate induced by O₃. Two-year-old seedlings were exposed in open-top chambers to charcoal filtered air (CFA), Non-filtered air (NFA) or Non-filtered air supplied with 40 ppb O₃ from 09:00 to 18:00 hours (NFA+40). No clear relationships were found between the development of visible injury and effects on plant growth or accumulated biomass. Olea europea ssp. sylvestris and Quercus ilex ssp. ballota appeared to be the most O₃-sensitive tree species screened; a ten month exposure to ambient O₃ levels (AOT40 = 12.4 ppm.h) caused reductions in height and/or stem growth. Further research is needed to characterise the physiological, biochemical and anatomical characteristics that may underlie the ‘sensitivity’ of certain Mediterranean species to O₃     

INFLUENCE OF A MYCORRHIZAL FUNGUS AND/OR RHIZOBIUM ON GROWTH AND BIOMASS PARTITIONING OF SUBTERRANEAN CLOVER EXPOSED TO OZONE

The influence of soilborne symbionts such as rhizobia or mycorrhizal fungi on plant response to ozone (O₃) has not been well defined. Leguminous plants in the field are infected by both types of organisms, which influence plant nutrition and growth. We studied the effects of infection with Rhizobium leguminosarum biovar trifolii and/or Gigaspora margarita on response of subterranean clover (Trifolium subterraneum L. cv Mt. Barker) to O₃. Exposures were conducted in greenhouse CSTR chambers using four O₃ concentrations [charcoal-filtered (CF), 50, 100, or 150 ppb; 6 h day^-1, 5 day wk^-1 for 12 weeks] as main plots (replicated). Four inoculum types were subplot treatments, i.e., inoculated with one, both, or neither microorganisms. At 2-wk intervals, plants were exposed to ¹⁴CO₂ and harvested 24 h later for determination of biomass and ¹⁴C content of shoots and roots. Ozone at 100 or 150 ppb suppressed clover growth during the experiment. Inoculation with G. margarita alone suppressed clover growth by the last two harvests, whereas R. leguminosarum alone enhanced growth during this time period. When both symbionts were present, the plants grew similarly to the noninoculated controls. Shoot/root ratios were increased by 100 or 150 ppb O₃ compared to that for CF-treated plants. Shoot/root ratios were greater for all inoculated plants compared to noninoculated controls. Under low O₃ stress (CF or 50 ppb), plants inoculated with both R. leguminosarum and G. margarita transported a greater proportion of recent photosynthate (¹⁴C) to roots than did noninoculated plants; we attribute this to metabolic requirements of the microorganisms. At the highest level of O₃ stress (150 ppb), this did not occur, probably because little photosynthate was available and the shoots retained most of it for repair of injury. Statistically significant interactions occurred between O₃ and inoculum types for shoot and total biomass. When averaged across harvests, 50 ppb O₃ suppressed biomass in the plants inoculated with G. margarita alone. Apparently, the mycorrhizal fungus is such a significant C drain that even a small amount of O₃ stress suppresses plant growth under these conditions.     

Quantifying the fine scale (1km × 1km) exposure and effects of ozone. Part 1. Methodology and application for effects on forests

Surface ozone concentrations show very large local variability. This, in rural areas, is largely a consequence of the degree to which the surface air is decoupled from the bulk of the atmosphere by nocturnal and winter stability effects and of the aerodynamic roughness and topography of the countryside. Procedures have been developed to simulate these effects and have been used with O₃ data from a regional monitoring network to quantify exposure of vegetation to mean and peak O₃ concentrations. The index of exposure to potentially phytotoxic O₃ concentrations is the AOT40 (accumulated exposure over a threshold of 40 ppb) expressed in ppb.h. The accumulated exposure of crop and forest surfaces to ozone is shown to increase approximately linearly with altitude and along a gradient from 3000 ppb.h in north west Scotland to 7000 ppb.h in the south of England. The area of UK forest which exceeds the critical level for ozone effects (10⁴ ppb.h above 40 ppb) totals 2.0 × 10⁴ km² and represents 47% of afforested land. The areas affected include most of southern and central England and Wales and large plantation forests of Northumberland and the Scottish borders.     

Different responses of ash and beech on nitrate versus ammonium leaf labeling

The effects of tree species on the N cycle in forest systems are still under debate. However, contradicting results of different ¹⁵N labeling techniques of trees and N tracers in the individual studies hamper a generalized mechanistic view. Therefore, we compared Ca(¹⁵NO₃)₂ and ¹⁵NH₄Cl leaf‐labeling method to investigate: (1) N allocation patterns from aboveground to belowground, (2) the cycles of N in soil‐plant systems, and (3) to allow the production of highly ¹⁵N enriched litter for subsequent decomposition studies. 20 beeches (Fagus sylvatica ) and 20 ashes (Fraxinus excelsior ) were ¹⁵N pulse labeled from aboveground with Ca(¹⁵NO₃)₂ and 40 beeches and 40 ashes were ¹⁵N pulse labeled from aboveground with ¹⁵NH₄Cl. ¹⁵N was quantified in tree compartments (leaves, stem, roots) and in soil after 8 d. Beech and ash incorporated generally more ¹⁵N from the applied ¹⁵NH₄Cl compared to Ca(¹⁵NO₃)₂ in all measured compartments, except for ash leaves. Ash had highest ¹⁵N incorporation [45% of the applied with Ca(¹⁵NO₃)₂] in its leaves. Both tree species kept over 90% of all fixed ¹⁵N from Ca(¹⁵NO₃) in their leaves, whereas only 50% of the ¹⁵N from the ¹⁵NH₄Cl tracer remained in the leaves and 50% were allocated to stem, roots, and soil. There was no damage of the leaves by both salts, and thus both ¹⁵N tracers enable long‐term labeling in situ field studies on N rhizodeposition and allocation in soils. Nonetheless, the ¹⁵N incorporation by both salts was species specific: the leaf labeling with ¹⁵NH₄Cl results in a more homogenous distribution between the tree compartments in both tree species and, therefore, ¹⁵NH₄Cl is more appropriate for allocation studies. The leaf labeling with Ca(¹⁵NO₃)₂ is a suitable tool to produce highly enriched ¹⁵N leaf litter for further long term in situ decomposition and turnover studies.     

Irrigating Onions and Potatoes with Chromium and Nickel: Its Effects on Catalase and Peroxidase Activities and the Cross-Contamination of Plants

Tropospheric ozone (O₃) has long been documented to cause an injury to plants, but a plants’ protectant, widely applicable in agronomical practice, does not exist. We evaluated the potential antiozonate efficacy of the antitranspirant di-1-p-menthene (Vapor Gard) compared with ethylenediurea (EDU) on Bel-W3 tobacco plants. Plants were treated either with water, or by EDU (10, 100, and 500 mg dm^?3), or by vapor (1, 5, 10, and 50 ml dm^?3) and were exposed either to O₃-enriched (90 ppb) or O₃-free air, for 12 days and 8 h day^?1. EDU when applied at 10 mg dm^?3 did not protect the plants against O₃, but when applied at 100 and 500 mg dm^?3 offered a significant protection to the plants. Vapor, when applied at 1 ml dm^?3 did not protect the plants against O₃, neither by terms of foliar visible injury nor by terms of aboveground biomass. In addition, when applied at 10 and 50 ml dm^?3 caused phytotoxicity to all the plants, which it was expressed as necrotic spots on the leaves’ surface, misshaping of the leaves, or short plants' height_. It is obvious that vapor does not protect Bel-W3 tobacco plants against O₃. The antiozonate role of di-1-p-menthene is species-specific and probably occurs only under short-term exposures.     

Effects of Elevated Ozone Concentrations on Thai Jasmine Rice Cultivars (Oryza Sativa L.)

This study investigated the effects of O₃ on growth, yields and physiological characteristics of Thai Jasmine rice cultivars. Rice was exposed to O₃ for 7 h day^?1 in a closed chamber for 113 days, beginning from seedling until harvest. O₃ concentration in each chambers was controlled at 0 ppb, 50 ppb, 100 ppb, 150 ppb and at the ambient level. Effects of O₃ on leaf area index (LAI) became obvious at maturity when LAI significantly decreased in the treatments under elevated O₃ concentrations. Results in shoot biomass indicated that shoot length was more affected by O₃ than shoot dry weight. Root length rather than dry weight was significantly reduced in all cultivars. The most severe damage of O₃ was found in photosynthetic components, namely chlorophyll and carotenoid contents, and rate of net photosynthesis. Yield components were also strongly affected by O₃. The highest reduction in filled seed per ear was found in the Pathumthani 1 cultivar by 78% when it was exposed to 150 ppb O₃ compared to the control (0 ppb). Similarly, 100-grain weight was also reduced as much as 12.3% in this cultivar.     

Cadmium in Fagus sylvatica L. trees and seedlings: Leaching,uptake and interconnection with transpiration

Most of the airborne Cd-polluted particles which eventually precipitate in forest regions remain on the surface of the tree leaves and do not penetrate into the plants' live tissues. Such pollutions can be removed from the leaves by cation exchange or can be washed off with water of low pH. Acid rains and acid soils have contributed very much to the solubilization of Cd and to its transformation into an available ionic form which is later absorbed by tree roots. ^115mCd uptake by young beech trees (Fagus sylvatica L.) seems to be positively correlated with the concentrations of the applied solutions as well as with the duration of the exposure. Low environmental pH increases the rate of ^115mCd uptake. High or low transpiration had no apparent effect on root absorption of Cd, but exposure of beech trees to a Cd(NO₃)₂ solution reduced their rates of transpiration after very few days of treatment.     

Effects of gaseous air pollutants on aphid performance on Scots pine and Norway spruce seedlings

Aphids are frequently found on conifers, but mass outbreaks are seldom reported. On trees stressed by air pollutants the natural resistance can be broken and insect attack combined with pollution stress may promote plant damages. To evaluate effects of air pollution on conifer aphids Scots pine and Norway spruce seedlings have been exposed to gaseous pollutants (O₃, SO₂ and NO₂) in growth chambers. The studied aphid species were Cinara pilicornis Hartig on Norway spruce, C. pinea (Mordv.) and Schizolachnus pineti Fabr. on Scots pine in SO₂ fumigations and S. pineti in O₃ and NO₂ fumigations. C. pilicornis nymphs had peaked dose response to SO₂ concentration. Both the first and third instar larvae of C. pilicornis showed highest mean relative growth rate (MRGR) at 100 ppb SO₂ concentration. MRGR of C. pinea peaked at 50 and 150 ppb SO₂ The response of S. pineti was more inconsistent During fumigation the peak MRGR of S. pineti was at 100 ppb and after exposure at 50 ppb SO₂. MRGR of S. pineti nymphs was not significantly affected during fumigation or after the end of fumigation experiment by 100 ppb O₃ or 100 ppb NO₂ or the mixtures. The results suggest that SO₂ affects more distinctively on aphid performance on conifers than O₃ or NO₂. Especially stem-feeding aphids on spruce can exploit physiological disturbance of host plant under pollution stress.     

Ozone concentrations at a rural mountain site of Northwestern Turkey

Average ozone concentrations at a remote site in the Uludag Mountain of Northwestern Turkey was 29 ppb for a 12 month period. Only 11% of the time 1-h average values exceed 50 ppb. The US Air Quality Standard of 0.12 ppm was not exceeded. The diurnal variations of O₃ and NO₂ were 27 and 2.3 ppb respectively, during summer 1993, indicating the impact of urban and industrial sources. Highest O₃ concentrations were observed under southerly and northerly winds, suggestive of the transport of photochemically produced oxidants from Bursa city and industries and a power plant located downwind of the sampling site.     

Physiological responses of Quercus ilex Leaves to Water Stress and Acute Ozone Exposure Under Controlled Conditions

The combined effect of water stress and ozone (O₃) on stomatal O₃ flux, damage to photosynthesis, and detoxification by biogenic volatile organic compounds (BVOC) in Quercus ilex leaves was studied. A 4-weeks O₃ exposure (250 ppb, 4 h per day) caused a reduction of photosynthesis and stomatal conductance, which was fully recovered 1 week after the end of the treatment, in well-watered and water-stressed plants. Measurements of stomatal O₃ flux revealed a low stomatal flux of the pollutant, which became minimal after stomatal closure caused by water stress. An induction of volatile monoterpenes, important compounds in the O₃ scavenging system in Q. ilex, and a burst of lipoxygenase compounds (LOX), which are released as gaseous by-products of membrane peroxidation, was observed after 2–3 weeks of O₃ fumigation. However, these compounds were also released in control leaves that were exposed to ozone only briefly, to determine stomatal O₃ flux. The low stomatal flux that occurred in water stress conditions helped avoiding permanent damage to Q. ilex leaves, although during the O₃ treatment photosynthesis was severely limited by stomatal closure. In well-watered plants, O₃ fumigation caused a noticeable increase of nocturnal stomatal conductance. If confirmed on adult plants under field conditions, this effect can imply larger flux of O₃ at night and possible detrimental effects of O₃ on leaf functions in plants exposed to high nocturnal O₃ levels.     

Impacts of Ambient Ozone and/or Acid Mist on the Growth of 14 Tree Species: An Open-Top Chamber Study Conducted in Japan

Young trees of 14 species were exposed to ambient ozone (O₃), (charcoal-filtered air [CF] or non-filtered air [NF]) and/or acid mist (pH 5 or 3: SO₄ ^2?, NO₃ ^?, Cl^? at equivalent 1:2:1 ratio) over three seasons (from June 1993 to November 1995) using tunnel-type open-top chambers at two sites (Abiko: 25 m a.s.l. and Akagi: 540 m a.s.l.) in Japan. Ambient, 12-hr (0600–1800) mean O₃ concentration for April–September during the period of experiment at Akagi (41 ppb) was 40 % higher than that at Abiko (30 ppb). The NF- and CF-chambers had 90 % and 30 % of ambient O₃, respectively. Significant decreases in biomass in the NF treatments were observed in Pinus densiflora, Larix k aempferi, Picea abies, Abies firma, Abies homolepis, Abies veitchii, Cryptomeria japonica, Populus maximowiczii, Betula platyphylla, Fagus crenata and Zelkova serrata as compared with the CF treatment. These results indicate that the current ambient level of O₃ in Japan is high enough to have adverse effects on the growth of all tree species examined, except Pinus thunbergii, Chamaecyparis obtusa and Quercus mongolica. Increasing acidity of mist caused no growth decreases in all tree species examined. However, the growth decreases by O₃ were greater at pH 3 mist treatment than at pH 5 mist treatment on Abies veitchii and Fagus. This suggested that the O₃ effect on tree growth can be exacerbated by the deposition of acid mist, possibly associated with nitrate.     

Pigment Concentrations and Ratios of Aleppo Pine Seedlings Exposed to Ozone

Two-year-old Aleppo pine (Pinus halepensis Mill.) seedlings were exposed to ambient air+50 ppb O₃ in open-top chambers (24 hours/day, 7 days/week) during May-October 1997 and to ambient air+70 ppb O₃ from May 1998 onwards. One growing season fumigation with ozone did not affect the pigment concentrations of the current-year (c) needles, nor were there any differences in photosynthesis or stomatal conductance. In May 1998, however, a marked carry-over effect was seen in the chlorophyll a and b and total carotenoid concentrations of the O₃-fumigated one-year-old (c+1) needles. The chlorophyll a and b and total carotenoid concentrations of newly flushed needles of the O₃-fumigated seedlings also seemed to be slightly decreased, as was their net photosynthesis when compared to the values of the filtered-air control needles. The chlorotic mottle and the changes in chloroplast pigments and photosynthesis of the c and/or c+1 needles of the NFA+O₃3 seedlings in May 1998 indicate that frequent episodes of ozone concentrations of ≥100 ppb, especially when they also occur during the evening and night hours, as in some areas in southern Europe, may result in visible needle damage on Aleppo pine.     

Air pollution measurements at the boulder atmospheric observatory

Pollution episodes of three distinct types were detected at the Boulder Atmospheric Observatory, which is a 300 m instrumented tower located in a rural area 25 km north of Denver and 20 km east of Boulder. Under stably stratified atmospheric conditions, usually at night or early morning, both power-plant-derived and general urban plumes were sampled. The powerplant plumes were characterized by SO₂ concentrations of 30 to 50 ppb in the plume centers, NO₂ maxima of 20 to 40 ppb on the plume edges, NO maxima of as much as 50 ppb in the plume centers, and the absence of O₃ from the plume centers. Light scattering (b _scat), principally due to coarse particles, was typically enhanced by 20 to 40%, relative to nominally clean air. The urban plumes typically contained NO₂ uniformly distributed throughout the affected air mass at 20 to 30 ppb, no detectable NO or SO₂, and O₃ present at concentrations less than half that in background air; b _scat was typically increased by a factor of 2 to 3. A third type of pollution episode, containing greatly increased concentrations of condensation nuclei, was observed during days when surface heating had apparently stimulated biological particle production. At these times the usual indicators of anthropogenic pollution were absent.     

Trends of Air Pollution and Its Present Situation in Hiroshima Prefecture

The ambient concentration of SO₂, NOx and O_x in the atmosphere of Hiroshima, Fukuyama and Fuchu city which were monitored by the prefectural monitoring stations, are examined to give a picture of the typical air pollution at these sites. Results show that the yearly concentrations of SO₂ in these areas are significantly fall from 20 to 6 ppb during 1978–1996 when the NOx concentrations having no such significant change which varies from 40 to 30 ppb. The Photo-chemical Oxidant (Ox) increases annually at the rate of 0.3 ppb to 0.6 ppb in Hiroshima city only. To know the present situation of air pollution the Differential Optical Absorption Spectroscopy (DOAS) system is used in the city of Higashi Hiroshima. The daily average concentrations of SO₂, NO₂, O₃ and HONO measured during the period of August 1999 to March 2000 ranged from 1.4 ppb to 2.8 ppb, 13 ppb to 26.9 ppb, 21 ppb to 53.6 ppb and 1 ppb to 4.3 ppb respectively. The patterns of concentrations of NO₂ and O₃ measured by DOAS look similar to the seasonal patterns of NOx and Ox by the conventional system.     

Foliar Injuries Caused by Ozone in Betula pubescens Ehrh. and Phleum pratense L. as Influenced by Climatic Conditions Before and During O3 Exposure

Seedlings of Betula pubescens Ehrh. (mountain birch) and Phleum pratense L. (timothy) were grown for 42 days under full light or 50% shade in the field at 12°C, and at comparable photosynthetic active radiation (PAR) levels in a greenhouse at 18°C. Plants from the four pretreatments were exposed to 78 nmol mol^-1 (ppb) O₃ (8 h day^-1) under two temperatures (15 and 25°C), two relative air humidities (50 and 80% RH) or two CO₂     

On Surface O3 Associated with Long-Range Transport in the Yellow Sea Region

Measurements of surface ozone (O₃) and nitrogen oxides (NO _x ) were conducted at Tae-ahn (TAP) and Chongwon (CHN) on the Korean Peninsula, during the Aerosol Characterization Experiment—Asian Pacific region (ACE-Asia) campaign, March–May 2001. The measurements provide ground-based data at a western remote site of south Korea and characterize the long-range transport of O₃ over the Yellow Sea region during spring. The mean values of O₃ and NO₂ concentration at TAP were 42 ppb and 12 ppb, respectively. The average O₃ diurnal variation of 17 ppb at TAP indicates that the loss of O₃ was not pronounced during the night. The highest NO₂ concentrations, with an average diurnal variation of 8 ppb, occurred in the afternoon at 13–15 LST. The day-to-day variation of daily O₃ concentrations at TAP is strongly influenced by the movement of synoptic scale weather patterns. In general, the O₃ concentration in a southwesterly airflow tended to increase when a moving anticyclone crossed the site, ahead of a cold front. By contrast, north-northwesterly airflows associated with the passage of a cold front bring fresh continental outflow and decrease O₃ concentrations. Surface O₃ data at TAP were classified utilizing backward trajectory analysis based on the residence time, as well as the path of the airflows, in the boundary layer (1500 m asl) over the Yellow Sea region. The results show that north-northwest continental airflows, that were transported around Lake Baikal and eastern Mongolia at an altitude of approximately 3 km at relatively high speed and came straight down at TAP, represent continental background O₃ concentrations with a mean value of 29 ppb for this period. These airflows have a short period of residence of less than one day in the boundary layer over the Yellow Sea region. In contrast, the mean O₃ value of 45 ppb was observed in regionally polluted airflows mainly passing through the east-southeast part of China and remaining for 3 days, on average, in the Yellow Sea region. These three days residence time of the regionally polluted airflows over the Yellow Sea region allowed sufficient time for photochemical O₃ formation.     

Translocation of 13C-labeled leaf or root litter carbon of beech (Fagus sylvatica L.) and ash (Fraxinus excelsior L.) during decomposition – A laboratory incubation experiment

The aim was to quantify medium term litter type and litter mixture effects on the translocation and transformation dynamics of root and leaf litter C during decomposition. Partitioning of ¹³C-labeled root or leaf litter C (beech – Fagus sylvatica L., ash – Fraxinus excelsior L.) to CO₂, water-extractable organic C (WEOC), microbial biomass C (C_MB) and light (LF) and heavy soil fraction (HF) was determined in a laboratory decomposition experiment of 206 days. The proportions of C mineralized from ash leaf (34%) and root litter (29%) were higher than those from beech leaf (24%) and root litter (23%). In mixture with beech, the mineralization of ash leaf litter was enhanced. Mineralization was positively correlated with litter-derived WEOC until day 29. Water-extractable organic C declined with time, until <0.1% of litter C remained in this fraction. Litter-C recovery in C_MB was higher for ash (0.7–1.0%) than for beech (0.2–0.4%). The litter C recovery in HF (4–12%) was positively correlated with that in WEOC (days 9 and 29) and C_MB, but did not differ between treatments. Ash leaf litter mineralization showed different behavior in mixed treatments from pure treatments. Thus, the ability to transfer results from pure to mixed treatments is limited. The litter differed in chemical composition and in mineralization dynamics, but differences in partitioning to HF, WEOC and MB were finally of minor importance.