Decomposition Of Coniferous Litter Research Articles

О некоторых факторах, лимитирующих почвообразовательную роль дождевых червей в европейской части таежной зоны России

The aim of the study: In order to study the factors limiting soil-forming activity of various earthworm species most common for the European part of the taiga zone of Russia. Location and time of the study. The study was conducted, in the period 2017-2018 in the European part of Russia. Methodology. Model experiments in standardized laboratory conditions were carried out in plastic trays to examine the influence of mineral subsoil acidity and plant litter composition on the survival and preferences of representatives of different ecological groups of earthworms (Oligochaeta, Lumbricidae): Dendrobaena octaedra, Lumbriscus rubellus, Aporrectodea caliginosa (epigeic, epigeic-endogeic and endogenic, respectively), differently involved in mixing of soil mineral and organic layers. Main results. For D. octaedra, which is not involved in the mixing of soil layers, the limiting factors (among the studied combinationst of mineral subsoil and litter properties) were not revealed. For L. rubellus, the most pedoturbation-effective of the studied species, the effect of litter chemistry on their integument was found to be the limiting factor in spruce forests. The A. caliginosa and D. octaedra were not sensitive to the chemical stimuli of the spruce litter F-layer. The substrates, which were apparently toxic for L. rubellus, were found to be suitable for D. octaedra, but not for A. caliginosa nutrition. L. rubellus was shown to useas food decomposition products of spruce, fir, juniper, cowberry, moss (Sphagnum) litter, enriched with carbonate-containing coprolites. The decomposition products of spruce litter, also enriched in coprolites, or in deciduous tree litter, were suitable for consumption by L. rubellus and A. caliginosa. The decomposition products of pine and cedar litter, including those enriched in coprolites, were not attractive as a food source for L. rubellus. Conclusion. It was concluded that active relocation of mineral particles to the fresh litter surface is an evolutionarily developed type of L. rubellus behavior, leading to decreased litter acidity and increased decomposition rate, and that L. rubellus participates in the formation of coarse-humus soils. However, the decomposition of coniferous litter accelerates acidification of mineral soil layers, precluding even limited vermopedoturbation from soil-forming processes. Among the studied earthworm species D. octaedra (the least effective n pedoturbation) is the most fit to the habitat formed by climax taiga vegetation, whereas the most effective L. rubellus is the least fit.

Nitrogen and carbon reallocation in fungal mycelia during decomposition of boreal forest litter.

Boreal forests are characterized by spatially heterogeneous soils with low N availability. The decomposition of coniferous litter in these systems is primarily performed by basidiomycete fungi, which often form large mycelia with a well-developed capacity to reallocate resources spatially- an advantageous trait in heterogeneous environments. In axenic microcosm systems we tested whether fungi increase their biomass production by reallocating N between Pinus sylvestris (Scots pine) needles at different stages of decomposition. We estimated fungal biomass production by analysing the accumulation of the fungal cell wall compound chitin. Monospecific systems were compared with systems with interspecific interactions. We found that the fungi reallocated assimilated N and mycelial growth away from well-degraded litter towards fresh litter components. This redistribution was accompanied by reduced decomposition of older litter. Interconnection of substrates increased over-all fungal C use efficiency (i.e. the allocation of assimilated C to biomass rather than respiration), presumably by enabling fungal translocation of growth-limiting N to litter with higher C quality. Fungal connection between different substrates also restricted N-mineralization and production of dissolved organic N, suggesting that litter saprotrophs in boreal forest ecosystems primarily act to redistribute rather than release N. This spatial integration of different resource qualities was hindered by interspecific interactions, in which litters of contrasting quality were colonised by two different basidiomycete species. The experiments provide a detailed picture of how resource reallocation in two decomposer fungi leads to a more efficient utilisation of spatially separated resources under N-limitation. From an ecosystem point of view, such economic fungal behaviour could potentially contribute to organic matter accumulation in the litter layers of boreal forests.

Seasonal dynamics of decomposition of coniferous leaf litter in a forest plantation ( Pinus merkusii) in Central Java, Indonesia

Decomposition of coniferous litter was studied from March 1990 until March 1991 in a pine forest plantation ( Pinus merkusii) in two 0.2 ha plots, at altitudes of 600 and 800 m on the south-west slope of Mount Merapi (2911 m), Central Java. Stratified litterbag sets were used to compare the influences of seasonality and degradation stage on the decomposition of pine litter. The variables used in monitoring the decomposition processes were weight loss, carbon and nitrogen contents and enzyme activity of the litter microflora. At each site the litterbags containing pine needles from L and F layers were randomly distributed in the L and F layers, respectively. After 1 year the weight loss in the litterbags in the upper plot was 32% in the L and 53% in the F layer. Weight loss in the lower plot was 60% in the L and 42% in the F layer. Temperature and moisture were not responsible for these differences in weight loss. Carbon content of litter in both plots decreased during a year from 49 to 35–37% in the L layer and from 38 to 28–31% in the F layer. Net immobilization of N took place in the L layer and net mobilization in the F layer. Dehydrogenase activity was positively correlated with N content and was highest when the critical N % was reached. Decomposition rate was influenced by moisture, but the chemical composition of the litter seemed to be even more important in determining the decay rate of the L layer.

Nutrient availability and interactions between soil arthropods and microorganisms during decomposition of coniferous litter: a mesocosm study

The functional roles of the fungivorous collembolan Tomocerus minor and the detritivorous isopod Philoscia muscorum during the decomposition of Pinus nigra needles were studied in mesocosms filled with two different types of F1 litter, obtained from two different forest soils. The effects of the animals on the availability of K+, Ca2+, NO inf3 sup- , NH inf4 sup+ , and PO inf4 sup3- and on the respiration, dehydrogenase, and cellulase activity of microorganisms were measured over one growing season. The animals were introduced into the F1 litter in three densities. The most important animal effect was a buffering effect, in that addition of the animals increased nutrient availability and microbial activity where the corresponding values in control mesocosms without animals were low, and decreased the nutrient availability and microbial activity where control values were high. This effect occurred for both species and was most evident in the substrate with the highest temporal fluctuations. The effects on nutrient availability are attributed to an animal effect on the activity of and successional stage reached the microbial community, with NH inf4 sup+ availability seen as the most important factor. The concept of functional groups in relation to these animal effects is discussed.

Dynamic interactions between functional groups of soil arthropods and microorganisms during decomposition of coniferous litter in microcosm experiments

Using microcosms containing decomposing Pinus nigra litter, the effects of introducing two species of soil arthropods, the fungivorous collembolan Tomocerus minor and the detritivorous isopod Philoscia muscorum, have been studied. The effects of these animals on microbial respiration, on dehydrogenase and cellulase activity, and on the concentration of exchangeable macronutrients (Ca2+, Mg2+, K+, NO inf3 sup- , NH inf4 sup+ , PO inf4 sup3- ) were measured. Both species enhanced microbial activity and the concentration of exchangeable nitrate, ammonium, and phosphate. Ca2+ and Mg2+ concentrations were lowered in the microcosms with animals. The differences between the two species were mainly quantitative, and it appears that the effect of isopods is direct, whereas the collembolans show direct and indirect effects. Positive effects of the presence of animals were found when microbial activities or concentrations of exchangeable nutrients in microcosms without animals were low; negative effects were found when they were relatively high. Thus, soil arthropods have a buffering role in soil processes. These results ae discussed against a background of a supposed succession of sugar fungi/bacteria to more slowly growing decomposing fungi.