Nematode communities indicate diverse soil functioning across a fog gradient in the Namib Desert gravel plains

Soil nematodes are fundamentally aquatic animals, requiring water to move, feed, and reproduce. Nonetheless, they are ubiquitous in desert soils because they can enter an anhydrobiotic state that allows them to persist when water is biologically unavailable. In the hyper‐arid Namib Desert of Namibia, rain is rare, but fog routinely moves inland from the coast and supports plant and animal life. Very little is understood about how this fog may affect soil organisms. We investigated the role of fog moisture in the ecology of free‐living, soil nematodes across an 87‐km fog gradient in the gravel plains of the Namib Desert. We found that nematodes emerged from anhydrobiosis and became active during a fog event, suggesting that they can utilize fog moisture to survive. Nematode abundance did not differ significantly across the fog gradient and was similar under shrubs and in interplant spaces. Interplant soils harbor biological soil crusts that may sustain nematode communities. As fog declined along the gradient, nematode diversity increased in interplant soils. In areas where fog is rare, sporadic rainfall events can stimulate the germination and growth of desert ephemerals that may have a lasting effect on nematode diversity. In a 30‐day incubation experiment, nematode abundance increased when soils were amended with water and organic matter. However, these responses were not evident in field samples, which show no correlations among nematode abundance, location in the fog gradient, and soil organic matter content. Soil nematodes are found throughout the Namib Desert gravel plains under a variety of conditions. Although shown to be moisture‐ and organic matter‐limited and able to use moisture from the fog for activity, variation in fog frequency and soil organic matter across this unique ecosystem may be biologically irrelevant to soil nematodes in situ.     

Species diversity and decomposition in laboratory aquatic systems: the role of species interactions

1. Interest in the effects of biodiversity on ecosystem processes is increasing, stimulated by the global species decline. Different hypotheses about the biodiversity‐ecosystem functioning (BEF) relationship have been put forward and various underlying mechanisms proposed for different ecosystems. 2. We investigated BEF relationships and the role of species interactions in laboratory experiments focussing on aquatic decomposition. Species richness at three different trophic levels (leaf detritus, detritus‐colonising fungi and invertebrate detritivores) was manipulated, and its effects on leaf mass loss and fungal growth were assessed in two experiments. In the first, monocultures and mixtures of reed (Phragmites australis), alder (Alnus glutinosa) and oak (Quercus cerris) leaf disks were incubated with zero, one or eight fungal species. Leaf mixtures were also incubated with combinations of three and five fungal species. In the second experiment, reed leaf disks were incubated with all eight fungal species and offered to combinations of one, two, three, four or five macroinvertebrate detritivores with different feeding modes. 3. Results from the first experiment showed that leaf mass loss was directly related to fungal mass and varied unimodally with the number of fungi, with a maximum rate attained at intermediate diversity in oak and reed and at maximum diversity in alder (the fastest decomposing leaf). 4. Mixing litter species stimulated fungal growth but interactions between species of fungi slowed down decomposition. In contrast, mixtures of macroinvertebrate detritivores reduced fungal mass and accelerated leaf decomposition. Possible explanations of the positive relationship between detritivore diversity and decomposition are a reduction in fungal dominance and a differentiation in the use of different resource patches promoted by higher fungal diversity. 5. In conclusion, the results show a general increase in decomposition rate with increasing biodiversity that is controlled by within‐ and between‐trophic level interactions, and support the hypothesis of both bottom‐up and top‐down effects of diversity on this process.     

Interactions between detritivores and microfungi during the leaf detritus decomposition in a volcanic lake (Lake Vico – central Italy)

The role of biota in the mass loss of Phragmites australis (Cav.) Trin. ex Steud was studied in the littoral belt of a central Italy volcanic lake. The research focussed on the feeding interactions between detritivores and decomposing fungi as drivers of the leaf litter decomposition. The litterbag technique was used to assess the leaf mass loss, the number of colonizing fungi and the patterns of leaf colonization by detritivores during 40 days of submersion in 16 sampling sites. Cores of bottom sediment were collected to estimate the organic content and ergosterol concentration as measure of fungal mass. The rate of leaf mass loss showed significant variability among the sampling sites and was non-linearly related to the quantity of organic depositions onto the lake bottom, peaking at about 40% of the dry matter. The rate was also positively correlated with the density of detritivore mass relative to the leaf unit mass, which increased with time. On the 20th day of litterbag immersion, when 40% of the initial leaf litter remained, we observed the best accordance between the two measures as well as the lowest difference in the detritivore mass density among sampling sites. In the absence of animals, the decomposition rate was positively related to the number of fungi on the decaying litter. The feeding activity of detritivores changed both the species richness and composition of the fungal community on the litter. The substrate reduction due to intense animal feeding appeared to limit the ability of fungi to regrow after grazing. As a result, an inverse relationship between the number of fungi and the decomposition rate was observed.     

Atmospheric water vapor as driver of litter decomposition in Mediterranean shrubland and grassland during rainless seasons

Litter production in many drought‐affected ecosystems coincides with the beginning of an extended season of no or limited rainfall. Because of lack of moisture litter decomposition during such periods has been largely ignored so far, despite potential importance for the overall decay process in such ecosystems. To determine drivers and extent of litter decay in rainless periods, a litterbag study was conducted in Mediterranean shrublands, dwarf shrublands and grasslands. Heterogeneous local and common straw litter was left to decompose in open and shaded patches of various field sites in two study regions. Fresh local litter lost 4–18% of its initial mass over about 4 months without rainfall, which amounted to 15–50% of total annual decomposition. Lab incubations and changes in chemical composition suggested that litter was degraded by microbial activity, enabled by absorption of water vapor from the atmosphere. High mean relative humidity of 85% was measured during 8–9 h of most nights, but the possibility of fog deposition or dew formation at the soil surface was excluded. Over 95% of the variation in mass loss and changes in litter nitrogen were explained by characteristics of water‐vapor uptake by litter. Photodegradation induced by the intense solar radiation was an additional mechanism of litter decomposition as indicated by lignin dynamics. Lignin loss from litter increased with exposure to ultraviolet radiation and with initial lignin concentration, together explaining 90%–97% of the variation in lignin mass change. Our results indicate that water vapor, solar radiation and litter quality controlled decomposition and changes in litter chemistry during rainless seasons. Many regions worldwide experience transient periods without rainfall, and more land area is expected to undergo reductions in rainfall as a consequence of climate change. Therefore, absorption of water vapor might play a role in decomposition and nutrient cycling in an increasing number of ecosystems.     

Detritivore stoichiometric diversity alters litter processing efficiency in a freshwater ecosystem

Many studies have estimated relationships between biodiversity and ecosystem functioning, and observed generally positive effects. Because detritus is a major food resource in stream ecosystems, decomposition of leaf litter is an important ecosystem process and many studies report the full range of positive, negative and no effects of diversity on decomposition. However, the mechanisms underlying decomposition processes in fresh water remain poorly understood. Organism body stoichiometry relates to consumption rates and tendencies, and decomposition processes of litter may therefore be affected by diversity in detritivore body stoichiometry. We predicted that the stoichiometric diversity of detritivores (differences in C: nutrient ratios among species) would increase the litter processing efficiency (litter mass loss per total capita metabolic capacity) in fresh water through complementation regarding different nutrient requirements. To test this prediction, we conducted a microcosm experiment wherein we manipulated the stoichiometric diversity of detritivores and quantified mass loss of leaf litter mixtures. We compared litter processing efficiency among litter species in each microcosm with single species detritivores, and observed detritivores with nutrient‐rich bodies tended to prefer litter with lower C: nutrient ratios over litter with higher C: nutrient ratios. Furthermore, litter processing efficiencies were significantly higher in the microcosms containing species of detritivores with both nutrient‐rich and ‐poor bodies than microcosms containing species of detritivores including only nutrient‐rich or ‐poor bodies. This might mean a higher stoichiometric diversity of detritivores increased litter processing efficiency. Our results suggest that ecological stoichiometry may improve understanding of links between biodiversity and ecosystem function in freshwater ecosystems.     

Do foliar endophytes affect grass litter decomposition? A microcosm approach using Lolium multiflorum

Symbiotic infection with fungal endophytes has been shown to decrease herbivory in several temperate grasses. We tested the hypothesis that foliar endophytes of grasses may also affect below-ground processes upon their host death, by altering the litter quality for detritivores or the microenvironment for decomposition. Microcosm–litterbag experiments were used to assess decay rates for litter produced by endophyte ( Neotyphodium sp.) infected vs uninfected Lolium multiflorum plants, and to examine endophyte-mediated effects of prior site occupants on current litter decomposition. We found that litter from endophyte-infected L. multiflorum decomposed more slowly than litter from endophyte-free conspecifics and from a naturally uninfected grass, Bromus unioloides . Furthermore, the endophyte–grass association modified the decomposition environment, so that B. unioloides litter decomposed faster when placed underneath a thick layer of endophyte-free L. multiflorum litter. Litter decay rates increased with the amount of root debris remaining in situ from the previous season, but were not affected by the infection status of prior site occupants. The lower decomposability of litter from infected L. multiflorum plants persisted across a range of microenvironments, as determined by different amounts of above-ground litter and soil moisture conditions. Endophyte infection tended to reduce the N content of decaying litter; however, litter N and C/N ratio mainly accounted for interspecific differences in decomposition. Our results imply that fungal endophytes not only can affect herbivory food chains, but also soil organisms and the ecosystem processes they regulate. This study suggests a novel role for symbiotic foliar endophytes in linking above-ground and below-ground sub-systems.     

Enhanced summer warming reduces fungal decomposer diversity and litter mass loss more strongly in dry than in wet tundra

Many Arctic regions are currently experiencing substantial summer and winter climate changes. Litter decomposition is a fundamental component of ecosystem carbon and nutrient cycles, with fungi being among the primary decomposers. To assess the impacts of seasonal climatic changes on litter fungal communities and their functioning, Betula glandulosa leaf litter was surface‐incubated in two adjacent low Arctic sites with contrasting soil moisture regimes: dry shrub heath and wet sedge tundra at Disko Island, Greenland. At both sites, we investigated the impacts of factorial combinations of enhanced summer warming (using open‐top chambers; OTCs) and deepened snow (using snow fences) on surface litter mass loss, chemistry and fungal decomposer communities after approximately 1 year. Enhanced summer warming significantly restricted litter mass loss by 32% in the dry and 17% in the wet site. Litter moisture content was significantly reduced by summer warming in the dry, but not in the wet site. Likewise, fungal total abundance and diversity were reduced by OTC warming at the dry site, while comparatively modest warming effects were observed in the wet site. These results suggest that increased evapotranspiration in the OTC plots lowered litter moisture content to the point where fungal decomposition activities became inhibited. In contrast, snow addition enhanced fungal abundance in both sites but did not significantly affect litter mass loss rates. Across sites, control plots only shared 15% of their fungal phylotypes, suggesting strong local controls on fungal decomposer community composition. Nevertheless, fungal community functioning (litter decomposition) was negatively affected by warming in both sites. We conclude that although buried soil organic matter decomposition is widely expected to increase with future summer warming, surface litter decay and nutrient turnover rates in both xeric and relatively moist tundra are likely to be significantly restricted by the evaporative drying associated with warmer air temperatures.     

Comparison of Degradative Ability, Enzymatic Activity, and Palatability of Aquatic Hyphomycetes Grown on Leaf Litter

Stream fungi have the capacity to degrade leaf litter and, through their activities, to transform it into a more palatable food source for invertebrate detritivores. The objectives of the present study were to characterize various aspects of fungal modification of the leaf substrate and to examine the effects these changes have on leaf palatability to detritivores. Fungal species were grown on aspen leaves for two incubation times. Leaves were analyzed to determine the weight loss, the degree of softening of the leaf matrix, and the concentrations of ATP and nitrogen associated with leaves. The activities of a protease and 10 polysaccharide-degrading enzymes produced by each fungus were also determined. Most fungi caused similar changes in physicochemical characteristics of the leaves. All fungi exhibited the capability to depolymerize pectin, xylan, and cellulose. Differences among fungi were found in their capabilities to produce protease and certain glycosidases. Leaf palatability was assessed by offering leaves of all treatments to larvae of two caddisfly shredders (Trichoptera). Feeding preferences exhibited by the shredders were similar and indicated that they perceived distinct differences among fungi. Two fungal species were highly consumed, some moderately and others only slightly. No relationships were found between any of the fungal characteristics measured and detritivore feeding preferences. Apparently, interspecific differences among fungi other than parameters associated with biomass or degradation of structural polysaccharides influence fungal palatability to caddisfly detritivores.     

Diversity,role in decomposition,and succession of zoosporic fungi and straminipiles on submerged decaying leaves in a woodland stream

Leaf litter is a very important primary source of energy in woodland streams. Decomposition of leaf litter is a process mediated by many groups of microorganisms which release extracellular enzymes for the degradation of complex macromolecules. In this process, true fungi and straminipiles are considered to be among the most active groups, more active than the bacteria, at least during the early stages of the process. Colonization increases the quality of the leaves as a food resource for detritivores. In this way, matter and energy enter detritus-based food chains. Previously, aquatic hyphomycetes were considered to be the major fungal group responsible for leaf litter decomposition. Although zoosporic fungi and straminipiles are known to colonize and decompose plant tissues in various environments, there is scant information on their roles in leaf decomposition. This study focuses on the communities of zoosporic fungi and straminipiles in a stream which are involved in the decomposition of leaves of two plant species, Ligustrum lucidum and Pouteria salicifolia, in the presence of other groups of fungi. A characteristic community dominated by Nowakowskiella elegans, Phytophthora sp., and Pythium sp. was found. Changes in the fungal community structure over time (succession) was observed: terrestrial mitosporic fungi appeared during the early stages, zoosporic fungi, straminipiles, and aquatic Hyphomycetes in early-to-intermediate stages, while representatives of the phylum Zygomycota were found at early and latest stages of the decomposition. These observations highlight the importance of zoosporic fungi and straminipiles in aquatic ecosystems.     

Soil fungal diversity and assembly along a xeric stress gradient in the central Namib Desert

The Namib Desert of south-western Africa is one of the oldest deserts in the world and possesses unique geographical, biological and climatic features. While research through the last decade has generated a comprehensive survey of the prokaryotic communities in Namib Desert soils, little is yet known about the diversity and function of edaphic fungal communities, and even less of their responses to aridity. In this study, we have characterized soil fungal community diversity across the longitudinal xeric gradient across the Namib desert (for convenience, divided into the western fog zone, the central low-rainfall zone and the eastern high-rainfall zone), using internal transcribed sequence (ITS) metabarcoding. Ascomycota, Basidiomycota and Chytridiomycota consistently dominated the Namib Desert edaphic fungal communities and a core mycobiome composed of only 15 taxa, dominated by members of the class Dothideomycetes (Ascomycota), was identified. However, fungal community structures were significantly different in the fog, low-rainfall and high-rainfall zones. Furthermore, Namib Desert gravel plain fungal community assembly was driven by both deterministic and stochastic processes; the latter dominating in the all three xeric zones. We also present data that suggest that the inland limit of fog penetration represents an ecological barrier to fungal dispersal across the Namib Desert.     

Water relations and CO2 exchange of the terrestrial lichen Teloschistes capensis in the Namib fog desert: Measurements during two seasons in the field and under controlled conditions

Although the coastal zone of the Central Namib Desert (Namibia) has negligible rainfall, frequent fog, dew and high air humidity support a luxurious lichen flora. Large areas of soil crust communities are dominated by the multibranched, fruticose Teloschistes capensis interspersed by a (still indeterminable) Ramalina species. In earlier communications, based on field measurements in autumn, we began the analysis of functional mechanisms that allow these lichens to exist under the special conditions of a fog desert. We have extended this work by monitoring lichen CO₂ exchange and water relations in spring and by experiments under controlled conditions.In both seasons, nocturnal hydration, by fog and/or dew, activated dark respiration of the lichens which was followed, after sunrise, by a short period of positive net photosynthesis (NP) that continued until metabolic inactivation occurred from desiccation. Dry thalli of T. capensis were able to reactivate NP through water vapour uptake alone, beginning at an air relative humidity of 82%, i.e. at a water potential of −26.3 MPa; the moisture compensation point during desiccation was at 13% thallus water content (WC, dry weight related). Optimal WC for photosynthesis was around 100%, and both species showed a large and extended suprasaturation depression of CO₂ assimilation. Light response showed “sun-plant” characteristics with saturation >1000 μmol m⁻² s⁻¹ photosynthetically active photon flux density (PPFD). However, due to rapid desiccation, the combination of light saturation with optimal WC very rarely occurred under field conditions. Light compensation point after sunrise was highly dependent on actual WC: at low hydration, it amounted to only ca. 10 μmol m⁻² s⁻¹ PPFD so that even the smallest levels of hydration could be used for carbon gain before desiccation took place again. This phenomenon was probably due to a hydration gradient in the thallus branches during transient moistening so that the outer photobiont layer was favoured in contrast to the internal mycobiont which remained dry longer and did not contribute respiratory CO₂ loss. Fully hydrated thalli had light compensation points around 50 μmol m⁻² s⁻¹ PPFD. Extended desiccation of 1–3 days had no impact on the magnitude and recovery of photosynthesis but, imposed desiccation of 10 days reduced NP in lab and field experiments and caused an extended period of recovery. “Resaturation respiration” was not detected in the field data, although it was present after experimental moistening of dry thalli.In spring, the higher fog frequency and intensity increased maximal nocturnal WC, maximal attained NP as well as integrated daily carbon income (ΣNP) compared to the autumn measurements. NP_max and ΣNP depended on maximal nocturnal WC with a saturation-type response. In terms of carbon gain both species seem to be optimally adapted to nocturnal moistening up to 160% WC and were not able to make use of higher degrees of hydration, a feature that might well influence their habitat selection.Maximal daily carbon-related ΣNP for T. capensis was 4.6 mg_C (g_C)⁻¹ day⁻¹. A rough estimate of the annual (projected) area-related carbon balance (photosynthetic income minus respiratory losses) based on published fog and dew frequencies and personal observations was 15–34 mg_C m⁻² yr⁻¹.     

Direct and indirect effects of the fungal endophyte <Emphasis Type="Italic">Epichloë uncinatum</Emphasis> on litter decomposition of the host grass, <Emphasis Type="Italic">Schedonorus pratensis</Emphasis>

Microbial plant symbionts have been suggested to mediate plant-soil feedback and affect ecosystem functions. Systemic Epichloë fungal endophytes of grasses are found to mediate litter decomposition. These effects are often linked to alkaloids produced by Epichloë species, which are hypothesized to negatively affect decomposers. Although endophytes have been found to affect plant community and soil biota, direct (through litter quality) and indirect (through the environment) effects of fungal endophytes on litter decomposition have been scarcely scrutinized. We placed litterbags with endophyte-symbiotic (E+) and non-symbiotic (E?) Schedonorus pratensis plant litter in plots dominated by E+ or E? plants of the same species, and followed the dynamics of mass losses over time. We predicted the endophyte would hinder decomposition through changes in litter quality and that both types of litter would decompose faster in home environments. E+ litter decomposed faster in both environments. The mean difference between decomposition rate of E+ and E? litter tended to be higher in E? plots. Nitrogen and phosphorus, two elements usually associated with high decomposition rates, were significantly lower in E+ litter. We also detected a higher proportion of C in the cellulose form in E+ litter. Contrary to the general assumption, we found that symbiosis with Epichloë fungal endophytes can be associated with higher decomposition of plant litter. Since direct effects of Epichloë fungi were still stronger than indirect effects, it is suggested that besides the alkaloids, other changes in plant biomass would explain in a context-dependent manner, the endophyte effects on the litter decomposition.     

Potential Physiological Activities of Fungi and Bacteria in Relation to Plant Litter Decomposition along a Gap Size Gradient in a Natural Subtropical Forest

Abstract The dynamics of fungal and bacterial potential physiological activities during leaf, branch, and bark litter decomposition along a gap size gradient in a subtropical forest was determined using substrate-induced respiration (SIR) with antibiotics selective for fungi and bacteria, respectively. A gap size gradient (1) was under closed canopy; (2) had small gaps with a diameter (≤5m); (3) had small to intermediate gaps (5–15 m diameter); (4) had intermediate to large gaps (15–30 m diameter); and (5) had large gaps (≥30 m diameter). Litter decomposition was studied using a litter bag technique. Fungi had higher SIR than bacteria for each type of litter in any size class of gaps. Gaps 1, 2, and 3 had higher fungal and bacterial SIRs than gaps 4 and 5. Moreover, decomposing leaf litter exhibited higher fungal and bacterial SIRs than branch, and branch higher than bark. Simple correlation analysis indicated that fungal SIR was a reliable index of decomposition rates. Fungal SIR was significantly and positively correlated with soil moisture, whereas bacterial SIR was not significantly correlated with soil moisture. The relationships among microclimatic factors, fungal and bacterial physiological activities, and rates of plant litter decomposition suggest that, in subtropical ecosystems, fungal community activities were strongly and directly regulated by the environmental heterogeneity within gaps, and an important regulator of rates of plant litter decomposition rates. Received: 13 January 1997; Accepted 28 March 1997     

A global experiment suggests climate warming will not accelerate litter decomposition in streams but might reduce carbon sequestration

The decomposition of plant litter is one of the most important ecosystem processes in the biosphere and is particularly sensitive to climate warming. Aquatic ecosystems are well suited to studying warming effects on decomposition because the otherwise confounding influence of moisture is constant. By using a latitudinal temperature gradient in an unprecedented global experiment in streams, we found that climate warming will likely hasten microbial litter decomposition and produce an equivalent decline in detritivore-mediated decomposition rates. As a result, overall decomposition rates should remain unchanged. Nevertheless, the process would be profoundly altered, because the shift in importance from detritivores to microbes in warm climates would likely increase CO(2) production and decrease the generation and sequestration of recalcitrant organic particles. In view of recent estimates showing that inland waters are a significant component of the global carbon cycle, this implies consequences for global biogeochemistry and a possible positive climate feedback.     

Climate change triggers effects of fungal pathogens and insect herbivores on litter decomposition

Increasing infestation by insect herbivores and pathogenic fungi in response to climate change will inevitably impact the amount and quality of leaf litter inputs into the soil. However, little is known on the interactive effect of infestation severity and climate change on litter decomposition, and no such study has been published for deciduous forests in Central Europe. We assessed changes in initial chemical quality of beech (Fagus sylvatica L.) and maple litter (Acer platanoides L.) in response to infestation by the gall midge Mikiola fagi Hart. and the pathogenic fungus Sawadaea tulasnei Fuckel, respectively, and investigated interactive effects of infestation severity, changes in temperature and soil moisture on carbon mineralization in a short-term laboratory study. We found that infestation by the gall midge M. fagi and the pathogenic fungus S. tulasnei significantly changed the chemical quality of beech and maple litter. Changes in element concentrations were generally positive and more pronounced, and if negative less pronounced for maple than beech litter most likely due to high quality fungal tissue remaining on litter after abscission. More importantly, alterations in litter chemical quality did not translate to distinct patterns of carbon mineralization at ambient conditions, but even low amounts of infested litter accelerated carbon mineralization at moderately increased soil moisture and in particular at higher temperature. Our results indicate that insect herbivores and fungal pathogens can markedly alter initial litter chemical quality, but that afterlife effects on carbon mineralization depend on soil moisture and temperature, suggesting that increased infestation severity under projected climate change potentially increases soil carbon release in deciduous forests in Central Europe.     

Leaf litter fungi in a Central Amazonian forest: the influence of rainfall,soil and topography on the distribution of fruiting bodies

Fungi are important components of tropical ecosystems, especially in the recycling of nutrients. However, there is little information on how fungal diversity is structured at scales suitable to plan their conservation. We tested if the distribution of fruiting bodies of litter fungi was random in the landscape (over 25 km²) in a tropical evergreen forest in Central Amazonia. We used linear regressions to evaluate the influence of rainfall, soil characteristics and topography on morphospecies richness and composition. Fungi were collected twice in thirty 0.25 × 250 m plots. Short-term rainfall was represented by the cumulative rainfall in the three days before each plot was surveyed. Plots were classified in two groups based on cumulative rainfall. Clay content in soil and rainfall influenced morphospecies richness, but responses to edaphic factors depended on rainfall. Wetter periods apparently decreased limiting moisture conditions in higher areas, allowing fungal activity and fruiting body production. Morphospecies composition was influenced by clay content, but influence on fungi was probably indirect as clay content was correlated with altitude, plant community and nitrogen availability. Our results suggest that the species of litter fungi are not randomly distributed in the landscape. Furthermore, they indicate that it is viable to conduct mesoscale evaluations of fungal diversity, if the temporal and spatial variation and their interaction are taken into account.     

Litter quality,decomposition rates and saprotrophic mycoflora in Fallopia japonica (Houtt.) Ronse Decraene and in adjacent native grassland vegetation

Fallopia japonica succeeds in invading different ecosystems likely because of its huge biomass production. This biomass is characterized by low nutritional quality and low decomposition rates but knowledge on whether these features are correlated to microbial decomposers is still lacking. The aims of this work were: i) to determine litter decomposition rates of native grassland vegetation and F. japonica under different conditions in a year-round experiment; ii) to evaluate litter quality and/or site effect on the decomposition of the invader and native vegetation and iii) to characterize mycoflora isolated from F. japonica and native vegetation litter. The results showed that F. japonica litter decomposes 3–4 times slower than that of native grassland, mainly due to its low N content and consequently high C/N ratio both in leaves and stems. As decomposition proceeds C/N in F. japonica litter decreases to values approaching those of the grassland litter. Site had no effect on the decomposition rates of F. japonica and grassland litter. Total fungal load and composition differed between F. japonica and native litter, and also varied across sites. These results indicate that the successful invasive plant F. japonica affects the structure and functions of the invaded ecosystem through a huge production of low quality, slow-decomposing litter that selects saprotrophic fungi.     

The legacy of climate change effects: previous drought increases short-term litter decomposition rates in a temperate mixed grass- and shrubland

Aims

Fungi play a central role in litter decomposition, a key process controlling the terrestrial carbon cycle and nutrient availability for plants and microorganisms. Climate change and elevated CO₂ affect soil fungi, but the relative importance of the global change variables for litter decomposition is still uncertain. The main objective was therefore to assess the short-term litter decomposition and associated fungal community in a global change manipulated temperate heath ecosystem.

Methods

The heath had been exposed to 6 years of warming, elevated atmospheric CO₂ and an extended pre-summer drought. Litterbags with litter from heather (Calluna vulgaris) and wavy-hair grass (Deschampsia flexuosa) were incubated in the litter layer for 6 months, where after we analyzed the litter-associated fungal community, litter loss, CO₂ respiration, and total content of carbon, nitrogen and phosphorus.

Results

Elevated temperature tended to increase litter decomposition rates, whereas elevated CO₂ had no effect on the process. The pre-summer drought treatment had a positive impact on litter decomposition, CO₂ respiration and fungal abundance in the litterbags, although we observed no major changes in fungal community composition.

Conclusions

The drought treatment during pre-summer had a legacy effect on litter decomposition as decomposition rates were positively affected later in the year. The community structure of litter-decomposing fungi was not affected by the drought treatment. Hence, the legacy effect was not mediated by a change in the fungal community structure.

     

Lentic and lotic habitats as templets for fungal communities: traits,adaptations, and their significance to litter decomposition within freshwater ecosystems

Decomposition of plant matter is a key ecosystem process and considerable research has examined plant litter decay processes in freshwater habitats. Fungi are common inhabitants of the decomposer microbial community and representatives of all major fungal phyla have been identified within freshwater systems. Development and application of quantitative methods over the last several decades have firmly established that fungi are central players in the decomposition of plant litter in freshwaters and are important mediators of energy and nutrient transfer to higher trophic levels. Despite the critical roles that fungi play in carbon and nutrient cycling in freshwater ecosystems, there are notable differences in the types and adaptations of fungal communities between lotic and lentic habitats. These differences can be explained by the wide range of hydrologic, physical, chemical and biological conditions within freshwater systems, all of which can influence the presence, type, and activity of fungal decomposers and their impact on litter decomposition. This paper seeks to provide a brief overview of the types, adaptations, and role of fungi within lotic and lentic freshwater ecosystems, with a particular emphasis on their importance to litter decomposition and the key environmental conditions that impact their growth and decay activities. This discussion will specifically focus on fungal dynamics occurring on plant litter in forested headwater streams and emergent freshwater marshes, since published data concerning their role in these systems is considerably more abundant in comparison to other freshwater habitats.     

Disentangling the Litter Quality and Soil Microbial Contribution to Leaf and Fine Root Litter Decomposition Responses to Reduced Rainfall

Climate change-induced rainfall reductions in Mediterranean forests negatively affect the decomposition of plant litter through decreased soil moisture. However, the indirect effects of reduced precipitation on litter decomposition through changes in litter quality and soil microbial communities are poorly studied. This is especially the case for fine root litter, which contributes importantly to forests plant biomass. Here we analyzed the effects of long-term (11 years) rainfall exclusion (29% reduction) on leaf and fine root litter quality, soil microbial biomass, and microbial community-level physiological profiles in a Mediterranean holm oak forest. Additionally, we reciprocally transplanted soils and litter among the control and reduced rainfall treatments in the laboratory, and analyzed litter decomposition and its responses to a simulated extreme drought event. The decreased soil microbial biomass and altered physiological profiles with reduced rainfall promoted lower fine root—but not leaf—litter decomposition. Both leaf and root litter, from the reduced rainfall treatment, decomposed faster than those from the control treatment. The impact of the extreme drought event on fine root litter decomposition was higher in soils from the control treatment compared to soils subjected to long-term rainfall exclusion. Our results suggest contrasting mechanisms driving drought indirect effects on above-(for example, changes in litter quality) and belowground (for example, shifts in soil microbial community) litter decomposition, even within a single tree species. Quantifying the contribution of these mechanisms relative to the direct soil moisture-effect is critical for an accurate integration of litter decomposition into ecosystem carbon dynamics in Mediterranean forests under climate change.