Beech Litter Research Articles

The role of coprophagy in nutrient release from feces of phytophagous insects

In microcosms containing soil from a mixed deciduous forest, we examined the nutrient release from feces of phytophagous insects through coprophagous behavior of saprophagous soil animals during 12 weeks of decomposition. The decomposition of feces of Operophthera fagata (Lepidoptera: Geometridae) fed on beech ( Fagus sylvatica) released more cations (Ca 2+, Mg 2+, K +) into the soil than the decomposition of beech litter, whether or not woodlice, Porcellio scaber and Oniscus asellus (Isopoda: Oniscidea), were present. Similarly, the C/N ratio of the soil was lower in assays with feces than in those with leaf litter. Coprophagy by isopods resulted in decreased C/N ratio of the soil. Respiratory activity of soil microbiota was greater when woodlice degraded Operophthera feces than when they degraded beech litter for 12 weeks. The present study provides evidence for nutrient release from the feces of phytophagous insects into the soil through the feeding activity of coprophagous soil animals.

Fate of nitrogen released from 15N-labeled litter in European beech forests.

The decomposition and fate of 15N-labeled beech litter was monitored in three European beech (Fagus sylvatica L.) forests (Aubure, France; Ebrach, Germany; and Collelongo, Italy) for 3 years. Circular plots around single beech trees were isolated from roots of neighboring trees by soil trenching, and annual litterfall was replaced by 15N-labeled litter. Nitrogen was continuously released from the decomposing litter. However, over a 2-year period, this release was balanced by the incorporation of exogenous N. Released N accumulated mainly at the soil surface and in the topsoil. Microbial biomass remained almost constant during the experiment at all sites except for considerably lower values at Ebrach. The 15N enrichment of the microbial biomass increased strongly during the first year and then remained stable. The 15N released from the decomposing litter was rapidly detected in roots and leaves of the beech trees, increasing regularly and linearly over the course of the experiment. The uptake of litter-released 15N by the trees was reduced under conditions that reduced tree growth. Under these conditions, leaves and fine roots were the dominant N sinks, and little N was allocated to other plant parts. By contrast, N uptake and N allocation from leaves to stem and bark tissues increased when tree growth was enhanced. Budgets for 15N showed that 2 to 4% of litter-released N was incorporated into the trees, about 35% remained in the litter and about 50% reached the topsoil.

Microflora, Protozoa and Nematoda in Lumbricus terrestris burrow walls: a laboratory experiment

Anecic earthworms Lumbricus terrestris L. were kept in laboratory microcosms containing soil and litter from a lime (Tilia cordata) and beech (Fagus sylvatica) forest. Nutrient (mineral nitrogen and phosphorus) contents, microbial activity and densities of protozoa and nematodes were determined in burrow walls and control soils after 165 days. Well-developed burrow linings consisting of earthworm faeces were formed in the “Tilia” treatment, but not in the “Fagus” treatment, presumably because beech litter was not an adequate food resource for L. terrestris. Consequently, increases in microbial biomass, basal respiration and microbial volume in burrow walls compared to surrounding soil were significant in the “Tilia” treatment only. However, in both treatments burrow walls were strongly enriched in mineral nitrogen and phosphorus. The density and biomass of protozoa were significantly greater in burrow walls compared to the control soil. The numbers of naked amoebae increased by similar factors of 4 and 3.5 in burrow walls of the “Tilia” and “Fagus” treatment, respectively. Flagellate density increased more than tenfold in burrow walls of the “Tilia” treatment but only twofold in the “Fagus” treatment. In addition, a comparatively large ciliate population was present in burrow walls in the “Tilia” treatment. The total abundance of protozoa was significantly correlated with the contents of inorganic N and P in the samples (r = 0.68 and 0.63 respectively, P< 0.03) suggesting that protozoan grazing participated in the mobilisation of nutrients from microbial biomass. The total nematode density was increased in burrow walls by a factor of 3 in the “Tilia” treatment (mostly due to bacterivorous nematodes), but was not affected in the “Fagus” treatment. In both treatments density of fungivorous nematodes increased, while that of plant parasites decreased in burrow walls compared to the control soil. It is concluded that the grazing pressure of protozoa and nematodes may control the dynamics of the microbial succession in earthworm burrow walls, strongly affecting nutrient cycling processes in these microhabitats.

Potential contribution of Lumbricus terrestris L. to carbon dioxide, methane and nitrous oxide fluxes from a forest soil

Potential effects of earthworms (Lumbricus terrestris L.) inoculated into soil on fluxes of CO2, CH4 and N2O were investigated for an untreated and a limed soil under beech in open topsoil columns under field conditions for 120 days. Gas fluxes from L. terrestris, beech litter and mineral soil from soil columns were measured separately in jars at 17 °C. The inoculation with L. terrestris and the application of lime had no effect on cumulative CO2 emissions from soil. During the first 3–4 weeks earthworms significantly (P<0.05) increased CO2 emissions by 16% to 28%. In contrast, significantly lower (P<0.05) CO2 emission rates were measured after 11 weeks. The data suggest that earthworm activity was high during the first weeks due to the creation of burrows and incorporation of beech litter into the mineral soil. Low cumulative CH4 oxidation rates were found in all soil columns as a result of CH4 production and oxidation processes. L. terrestris with fresh feces and the beech litter produced CH4 during the laboratory incubation, whereas the mineral soil oxidised atmospheric CH4. Inoculation with L. terrestris led to a significant reduction (P<0.02) in the CH4 oxidation rate of soil, i.e. 53% reduction. Liming had no effect on cumulative CH4 oxidation rates of soil columns and on CH4 fluxes during the laboratory incubation. L. terrestris significantly increased (P<0.001) cumulative N2O emissions of unlimed soil columns by 57%. The separate incubation of L. terrestris with fresh feces resulted in rather high N2O emissions, but the rate strongly decreased from 54 to 2 μg N kg–1 (dry weight) h–1 during the 100 h of incubation. Liming had a marked effect on N2O formation and significantly (P<0.001) reduced cumulative N2O emissions by 34%. Although the interaction of liming and L. terrestris was not significant, N2O emissions of limed soil columns with L. terrestris were 8% lower than those of the control.

Decomposition of 15N-labelled beech litter and fate of nitrogen derived from litter in a beech forest.

The decomposition and the fate of 15N- labelled beech litter was monitored in a beech forest (Vosges mountains, France) over 3 years. Circular plots around beech trees were isolated from neighbouring tree roots by soil trenching. After removal of the litter layer, 15N-labelled litter was distributed on the soil. Samples [labelled litter, soil (0-15 cm depths], fine roots, mycorrhizal root tips, leaves) were collected during the subsequent vegetation periods and analysed for total N and 15N concentration. Mass loss of the 15N-labelled litter was estimated using mass loss data from a litterbag experiment set up at the field site. An initial and rapid release of soluble N from the decomposing litter was balanced by the incorporation of exogenous N into the litter. Fungal N accounted for approximately 35% of the N incorporation. Over 2 years, litter N was continuously released and rates of N and mass loss were equivalent, while litter N was preferentially lost during the 3rd year. Released 15N accumulated essentially at the soil surface. 15N from the decomposing litter was rapidly (i.e. in 6 months) detected in roots and beech leaves and its level increased regularly and linearly over the course of the labelling experiment. After 3 years, about 2% of the original litter N had accumulated in the trees. 15N budgets indicated that soluble N was the main source for soil microbial biomass. Nitrogen accumulated in storage compounds was the main source of leaf N, while soil organic N was the main source of mycorrhizal N. Use of 15N-labelled beech litter as decomposing substrate allowed assessment of the fate of litter N in the soil and tree N pools in a beech forest on different time scales.

Clostridium akagii sp. nov. and Clostridium acidisoli sp. nov.: acid-tolerant, N2-fixing clostridia isolated from acidic forest soil and litter.

Two anaerobic acid-tolerant bacteria, CK58T and CK74T, were isolated from acidic beech litter and acidic peat-bog soil, respectively. Both bacteria were spore-forming, motile rods with peritrichous flagella. The capacity to sporulate decreased with prolonged cultivation. Cells of CK58T formed chains or aggregates and were linked by a connecting filament that consisted of a core and a surrounding sheath. Cellobiose, glucose, xylose, arabinose, maltose, mannose and salicin supported growth of CK58T. These substrates, as well as mannitol, lactose, sucrose, glycerol, melezitose, raffinose and rhamnose, supported growth of CK74T. Sorbitol, trehalose, H2/CO2, CO/CO2, vanillate, Casamino acids, peptone, and various purines and pyrimidines did not support the growth of either organism. Growth of CK58T and CK74T on glucose yielded butyrate, lactate, acetate, formate, H2 and CO2 as end products. Growth of CK58T and CK74T was observed at pH 3.7-7.1 and 3.6-6.9, respectively. CK58T and CK74T grew in nitrogen-free medium at pH 3.7 under an N2 atmosphere and reduced acetylene at rates approximating 1 nmol min-1 (mg protein)-1. CK58T and CK74T did not contain carbon monoxide dehydrogenase or cytochromes, produce methane, or dissimilate nitrate or sulfate. Thus, CK58T and CK74T were characterized as nonacetogenic, N2-fixing, fermentative chemo-organotrophs. The G + C contents of CK58T and CK74T were 31.4 and 30.7 mol%, respectively. CK58T and CK74T were phylogenetically most closely related to Clostridium pasteurianum. The 16S rRNA gene sequence similarity values of CK58T and CK74T to C. pasteurianum and each other did not exceed 96.5%, and it is proposed that strains CK58T and CK74T be named Clostridium akagii CK58T (DSM 12554T) and Clostridium acidisoli CK74T (DSM 12555T), respectively. These results suggest that previously uncharacterized clostridial species reside and might fix N2 in the annoxic microzones of acidic forest soil and litter.

Microbial biomass, biovolume and respiration in Lumbricus terrestris L. cast material of different age

Effects of the gut passage, the age of cast material and the type of ingested substrate on the microbial community in Lumbricus terrestris faeces were studied in laboratory microcosms containing four soil–litter combinations: lime forest soil+lime litter, beech forest soil+lime litter, beech forest soil+beech litter and beech forest soil without litter. Microbial biomass (SIR method), basal respiration and biovolume of bacteria and fungi were measured in earthworm casts and reference material after 1, 5, 10 and 100 d of incubation. To separate effects of mixing of litter and soil in the gut of L. terrestris from specific gut or cast associated processes, actual faecal properties were compared with ‘expected’ values, calculated on the basis of corresponding measurements in soil and litter ingested by L. terrestris. Microbial respiration, biomass and fungal volume in fresh (1 d old) faeces strongly depended on the type of soil and litter material consumed by L. terrestris. The comparison with ‘expected’ values indicated that microbial biomass and volume changed little during the passage through the gut of L. terrestris. In contrast, even a short incubation of casts caused marked changes in the microbial properties studied: microbial biomass sharply declined during the first 5 d of incubation; basal respiration which exceeded ‘expected’ values by 30–120% in fresh casts, decreased steadily and was significantly below ‘expected’ values by d 10 of the incubation; biovolume of bacteria and fungi in fresh casts was 20–60% higher than expected and then steadily declined in lime litter but not in beech litter treatments. Generally, the fungal-to-bacterial volume ratio in cast material was not significantly affected by the gut passage nor by the incubation of casts.

Structural and functional responses of benthic macroinvertebrates to acid precipitation in two forested headwater streams (Vosges Mountains, northeastern France)

From December 1996 to August 1997, beech litter breakdown and stream benthic macroinvertebrate communities were investigated to assess the effects of acidic precipitation on community structure and function in two second-order headwater streams of the Vosges Mountains (NE France). Because of microscale changes in bedrock mineral composition, one of the streams was acidified (mean pH=4.53, mean total Al=421 μg.l-1) and the other circum-neutral (mean pH=7.23, mean total Al=36 μg.l-1). Results showed that both litter breakdown rate and macroinvertebrate community structure were drastically affected under acidic conditions. The rate of leaf litter breakdown decreased by nine times in the acidic stream. Benthic sampling showed that scrapers were totally eradicated and both gathering and filtering collectors were drastically reduced. Such drastic effects appear to be the consequences of the toxicity of acid water including both proton and aluminum toxicity. A decrease in shredder abundance and a shift from the efficient acid-sensitive Amphipoda Gammarus fossarum to acid-tolerant Nemouroidea (mainly Leuctra sp.) was observed in the acidic stream. Our results indicate that freshwater acidification significantly alters the action of shredders processing leaf litter in the acidic stream. Consequently, interactions between structural and functional responses to acidification probably have profound consequences on the efficiency of acidified stream ecosystems, which in return may alter downstream functioning.

A β-1,4-endoglucanase-encoding gene from Cellulomonas pachnodae

A gene library of Cellulomonas pachnodae was constructed in Escherichia coli and was screened for endoglucanase activity. Five endoglucanase-positive clones were isolated that carried identical DNA fragments. The gene, designated cel6A, encoding an endoglucanase enzyme, belongs to the glycosyl hydrolase family 6 (cellulase family B). The recombinant Cel6A had a molecular mass of 53 kDa, a pH optimum of 5.5, and a temperature optimum of 50-55 degrees C. The recombinant endoglucanase Cel6A bound to crystalline cellulose and beech litter. Based on amino acid sequence similarity, a clear cellulose-binding domain was not distinguished. However, the regions in the Cel6A amino acid sequence at the positions 262-319 and 448-473, which did not show similarity to any of the known family-6 glycosyl hydrolases, may be involved in substrate binding.

Aggregation of Potamophylax cingulatus (Trichoptera: Limnephilidae) larvae in response to possible food limitation in a southern French stream

Larvae of Potamophylax cingulatus (Trichoptera: Limnephilidae) were observed to be living at high densities in a low-order stream in a beechwood in southern France. The hypothesis that this population was food-limited was investigated by adding supplementary food sources in the form of dried leaf litter, contained within mesh bags. Caddis larvae rapidly colonised alder leaves, even while naturally occurring beech litter was still relatively abundant. After a major storm, which removed natural leaf aggregations but left the benthic population of P. cingulatus intact, colonisation of alder leaves remained rapid; beech leaves added at the same time, however, were colonised much more slowly. Mass loss of alder leaves was significantly more rapid than that of beech leaves. Population estimates of P. cingulatus demonstrated continuous recolonisation of the benthos, with rapid aggregation onto alder leaf packs both before and after the storm, suggesting that this movement was related to food availability. Relative lack of consumption in beech leaves, however, when natural food supplies were apparently severely reduced, demonstrated that total food limitation was not occurring. It is speculated that P. cingulatus, in its immediate pre-pupal instar, has specific nutritional requirements that alder litter can satisfy but beech litter cannot.

Effect of vegetation on chemical composition of H horizons in incipient podzols as characterized by [formula omitted] NMR and pyrolysis-GC/MS

In a primary vegetation sequence on wind blown sands in the Netherlands, podzolization becomes evident under pine forest with various undergrowth and is more expressed under the subsequent beech forest. Recognizable podzol-B horizons appear together with H (humified O) horizons. In order to investigate whether the vegetation influences H horizon composition and the water-soluble fraction of this horizon, H horizons of three subsequent succession stages ( Pinus/Empetrum–Fagus/Vaccinium–Fagus without undergrowth) were sampled, fractionated, and analysed with 13 C CPMAS-NMR, pyrolysis-GC/MS, and by pollen analysis. Water soluble and NaOH soluble fractions of the three H horizons were very similar, suggesting that the humified material in the H horizon was formed exclusively from pine litter and that beech litter, yearly added to the soil surface in large amounts, did not influence the composition of the H horizon. The fact that the input of beech litter into the H horizon under beech was small was supported by very low amounts of Fagus pollen in all H layers. Humin fractions of the three H horizons were remarkably different, which was mainly due to varying amounts of beech root litter. The similarity of the water soluble organic matter fractions suggested that a direct relation between vegetation and organic matter mobilized by humification in the H horizon only exists under pine forest. Hence, increased podzolization under beech was probably not due to changing organic matter input, but to the factor time.

Quality, Decomposition and Isopod Consumption of Tree Litter Produced under Elevated CO 2

Rising atmospheric CO 2 is expected to alter plant tissue quality which in turn could affect litter quality, decomposition, and carbon and nutrient turnover. We tested this hypothesis using leaf litter of beech (Fagus sylvatica) and branchlets (wood + bark) of spruce (Picea abies) produced under contrasting CO 2 concentrations in model ecosystems. Both types of litter produced under elevated CO 2 had significantly lower N concentrations, but showed no CO 2 -related differences in carbon and lignin concentrations. Decomposition rates (mass loss) assessed in a natural temperate forest were significantly slower in litter produced at high CO 2 . However, this effect became stronger in beech leaves but gradually disappeared in spruce branchlets over the 331-d exposure period. Irrespective of CO 2 treatment beech leaf litter lost 16% of its initial N content. Spruce branchlets produced at low CO 2 lost 50% of their initial N content, and those produced at high CO 2 lost 26%. Two isopod species representing native macro-decomposers consumed 36% more of the high CO 2 -produced beech litter than they did of low CO 2 -produced beech litter. Only small, and non-significant increases in consumption of high CO 2 -produced spruce branchlets were observed. Isopods feeding on high CO 2 litter also produced more feces than those feeding litter from low CO 2 Our results indicate that CO 2 -induced litter quality changes influence only certain stages of decomposition, and that these stages differ between different litter types. Inhibitory effects of elevated CO 2 , however, may be compensated by the positive feed-back of intensified litter processing of low quality litter by macro-decomposers. Consequently, the entire cycle of litter production and decomposition must be included in the analysis of the potential effects of rising CO 2 on litter decomposition. This includes both micro- and macro-decomposer specific effects.

Influence of soil type on mass loss and nutrient release from decomposing foliage litter of beech and Norway spruce

Mass loss and nutrient release from decomposing foliage litter of beech (Fagus sylvatica L.) and Norway spruce (Picea abies (L.) Karst.) were studied at three sites along a soil fertility gradient. The influence of soil type on initial litter quality and on decomposition was separated by reciprocal transplantation of litter among soil types using the litterbag technique. Decomposition of beech litter was influenced by both initial litter quality and incubation site. Mass loss in beech litter was positively influenced by soil nutrient status. Decomposition of Norway spruce litter was not affected by initial litter quality, and the positive influence of a nutrient-rich soil environment on decomposition was weak. Nutrient release in litters of both tree species was greatly affected by soil type through its influence on initial litter quality, as nutrient release was positively related to initial nutrient concentrations. Nutrient release was less affected through the soil environment, as it only influenced release of some nutrients, and the differences were not consistently related to soil nutrient status or mass loss. The influence of soil type on decomposition differed among the two tree species, suggesting that it may be more significant in species that produce relatively higher quality litter.

Possible mechanisms of sugar maple regeneration failure and replacement by beech in the Boisé-des-Muir old-growth forest, Québec

To better understand the causes of sugar maple (Acer saccharum Marsh.) replacement by beech (Fagus grandifolia Ehrh.) in the Boisé-des-Muir old-growth forest (Québec), we studied, i) the effect of beech litter on soil properties, ii) the effect of low light availability on maple survival, and iii) beech regeneration via root sprouts. Soil properties, understory light, seedling emergence and survival, height growth, and density distribution of maple and beech were compared between the old-growth stand and an adjacent managed stand where the abundance of maple regeneration was high. We did not observe any detrimental effect of beech litter on soil properties and maple early establishment. Overall light availability and maple stocking were lower, and maple density declined more markedly with increasing size in the old-growth stand than in the managed stand. The deficient maple regeneration in the old-growth stand might be related to a lack of microsites where light availability is high enough for maple survival, and not to a lack of initial recruitment in this species. In the old-growth stand, beech was located in more shaded microsites than maple but had a higher growth. Size class distributions of maple and beech suggest that beech had a higher survival rate than maple and that beech sprouts had a higher survival rate than beech seedlings. Beech seems to be better adapted than maple to survive in the deep shade of the old-growth stand. However, we expect that maple will regain its dominance in the understory of the Boisé-des-Muir with increasing stand breakup that is likely to occur in the future.

A comparative study of beech leaf breakdown, energetic content, and associated fauna in acidic and non-acidic streams

We performed an eight-month study on beech litter breakdown and caloric content in two headwater streams characterized by different degrees of acidification (mean pH = 4.5 and 7.2). We also compared macroinvertebrate colonization of the leaves in the two streams. Beech leaf breakdown rate was 9 times slower under acidic conditions, which is a decrease greater than in other records from the literature. In both streams leaf caloric content decreased as litter decomposition proceeded but was always lower in the non-acidic one. Furthermore, results of energy loss per litter basket showed that the acidified stream was energetically inefficient when compared with the circumneutral stream. Gammarus fossarum dominated the shredder assemblage in leaf packs placed in the circumneutral stream. Gammarus was lacking in the acidified stream where Leuctra assumed greatest importance. This suggests that the absence of an efficient shredder, G. fossarum may have partly accounted for the slow leaf breakdown and the resulting accumulation of leaf litter in the acidified stream.

Carbohydrate decomposition in beech litter as influenced by aluminium, iron and manganese oxides

Although carbohydrates are one of the most degradable groups of soil organic matter compounds, they can accumulate in soil horizons containing strongly humified organic matter. It is therefore assumed that stabilization reactions exist, which may be related to the presence of particular mineral compounds in soils. An incubation experiment was made to investigate the influence of selected oxides (ferrihydrite, aluminium hydroxide, birnessite) on the decomposition of polysaccharides in beech litter. pH changes and the dynamics of total organic carbon, cellulosic and non-cellulosic polysaccharides, and potential cellulase activity were recorded. Carbon loss during incubation was promoted by 10% in the presence of birnessite, which acts as an oxidizing agent. Polysaccharide decomposition was hardly affected by birnessite. On the other hand, ferrihydrite and aluminium hydroxide reduced the decomposition of bulk organic matter by 12 and 65%, respectively. These mineral phases resulted in a reduction of carbohydrate decomposition by 15 and 50%, respectively. In the presence of aluminium hydroxide, there was no significant cellulose decomposition after 90 d. Nevertheless, throughout the experiment, potential cellulase activity was higher in this treatment than in the presence of birnessite. Therefore we assume that organic matter stabilization is caused by toxic effects, or by adsorption to the oxides or hydroxides, especially to aluminium hydroxide, or by both. This process tends to lower the microbial availability of organic matter and therefore to inhibit the decomposition.

Effects of litter (beech and stinging nettle) and earthworms (Octolasion lacteum) on carbon and nutrient cycling in beech forests on a basalt-limestone gradient: A laboratory experiment

Effects of leaf litter of beech (Fagus sylvatica L.) and stinging nettles (Urtica dioica L.) and of the endogeic earthworm species Octolasion lacteum (Orley) on carbon turnover and nutrient dynamics in soil of three beechwood sites on a basalt hill (Hesse, Germany) were investigated in a laboratory experiment lasting for about 1 year. The sites were located along a gradient from basalt (upper part of the hill) to limestone (lower part of the hill) with an intermediate site in between (transition zone). At the intermediate site U. dioica dominated in the understory whereas at the other sites Mercurialis perennis L. was most abundant. The amount and composition of organic matter was similar in soil of the basalt (carbon content 5.9%, C/N ratio 13.8) and intermediate site (carbon content 5.6%, C/N ratio 14.3) but the soil of the intermediate site produced more CO2 (in total +17.5%) and more nitrogen (as nitrate) was leached from this soil (in total +55.6%). It is concluded that the soil of the intermediate site contains a large mobile carbon and nitrogen pool and the formation of this pool is ascribed to the input of U. dioica litter. Leaf litter of U. dioica strongly increased NO3 –-N leaching immediately after the litter had been added, whereas nitrogen was immobilized due to addition of beech litter. Despite the very fast initial decomposition of nettle litter, the increase in CO2 production due to this litter material was only equivalent to 20.1% of the amount of carbon added with the nettle litter; the respective value for beech litter was 34.8%. Earthworms altered the time course of carbon and nitrogen mineralization in each of the treatments. In general, earthworms strongly increased mineralization of nitrogen but this effect was less pronounced in soil of the intermediate site (treatments without litter), which is ascribed to a depleted physically protected nitrogen and carbon pool. In contrast, their effect on the total amount of nitrogen mobilized from nettle litter was small. Earthworms significantly reduced CO2 production from soil of the intermediate site (treatments without litter) and it is concluded that earthworm activity contributes to the restoration of the depleted physically protected carbon pool at this site.

Establishment of Fagus sylvatica and Fraxinus excelsior in an old‐growth beech forest

Abstract. Distribution of tree seedlings, forest architecture, light conditions, ground vegetation and humus conditions were studied in a 45 m × 100 m area including multiple gaps in an old‐growth beech forest. Gaps were created after some beech trees had been felled in severe storms in February 1990. A group of adult ash trees is found near the study site. The data were analyzed by Correspondence Analysis. Young seedlings (&lt; 4 yr), of both Fraxinus (a sun species) and Fagus (a shade species), were most abundant under the crown of beech trees in semi‐shade conditions, and where beech litter did not accumulate.Differences in the dissemination of Fraxinus and Fagus explained differences in the establishment of the two species. In contrast, older seedlings of beech established before the storms were more numerous in the gaps, suggesting a change in the ecological requirements of beech seedlings in the course of time.

Field study of beech (t Fagus sylvatica L.) and melojo oak (t Quercus pyrenaica Willd) leaf litter decomposition in the centre of the Iberian Peninsula

The effect of the canopy on leaf decomposition of beech (t Fagus sylvatica) and melojo oak (t Quercus pyrenaica) was studied during a period of 660 days in a mountain forest of central Spain; response of leaves to leaching was also studied to determine the effects of rainfall after leaf fall. Beech leaves lost 5.8% of their weight by leaching, whereas melojo oak leaves lost 13%. Under both types of canopy, beech leaves showed almost no difference in their decomposition patterns, with decay constants of 0.31 and 0.32 respectively. Melojo oak leaves showed quite a different behaviour under both canopies; decay constant was 0.47 under t Quercus pyrenaica and 0.77 under beech canopy. Total immobilization of nitrogen was less in the melojo oak forest. Effects of summer dryness were sharper in the melojo oak forest, where decomposition stopped during the summer. This delay in the decomposition might have been due to the lower canopy density in the melojo oak forest. The decomposition patterns of the leaves of both species, under the canopy of the other species, suggests what might happen in mixed stands. Thus, the presence of melojo oaks in beech forest would increase decay and decrease nitrogen immobilization. The presence of beech trees in melojo oak forests would improve microclimatic conditions and increase decay, whereas beech litter on the soil would immobilizate more nitrogen.

Decomposition, nitrogen and phosphorus mineralization from beech leaf litter colonized by ectomycorrhizal or litter‐decomposing basidiomycetes

summaryThe decomposition and the nitrogen and phosphorus mineralization of fresh beech (Fagus sylvatica L.) leaf litter are described. Leaves were buried for up to 6 months in plant containers in which Scots pine (Pinus sylvestris L.) seedlings were cultivated at a low rate of nutrient addition. The saprotrophic abilities of three ectomycorrhizal fungi, Thelephora terrestris Ehrh.: Fr., Suillus bovinus (L.: Fr.) O. Kuntze and Paxillus involutes (Batsch: Fr) Fr., were compared with the degradation caused by the litter‐decomposing basidiomycete, Lepista nuda (Bull.: Fr.) Cooke. Uninoculated leaves were included as controls. The investigation was performed at two different pH values since substrate pH is supposed to have an effect on the activities of extracellular enzymes of ectomycorrhizal fungi. The enzyme expression might also be largely influenced by the substrate they colonised. The mycorrhizal fungi caused only a low decomposition rate of the litter compared with that of L. nuda, and nitrogen was released only by L. nuda. Leaves colonized by mycorrhizal fungi showed no net release of nitrogen; on the contrary, a small accumulation of N in the litter was observed. It therefore seems likely that the ectomycorrhizal fungi studied do not have the ability to decompose efficiently the lignocellulose matrix of the relatively recalcitrant beech leaf litter. The degradation of this matrix seems to be essential for the fungi to gain access to the leaf nitrogen pool of fresh beech litter. A direct release of nitrogen from organic compounds by ectomycorrhizal fungi seems therefore to be confined to the older litter layers. The beech leaf litter contained an important fraction of easily mineralizable phosphorus. P was not a growth limiting factor m the cultivation system, and could therefore accumulate in the leaf litter colonized by the ectomycorrhizal mycelium.