Search Results (74)

The quantity, quality, and accumulation rate of plant litter play a key role in forest floor flammability and, by extension, fire regimes. The varying foliage properties of different tree species also determine litter’s decomposition and its accumulation on the forest floor. The removal of litter by soil fauna, i.e., bioturbation, depends on both the dominant tree species and the successional stage of the forest stand. This research involved laboratory mesocosm experiments aiming to determine the effects of litter quality and earthworm activity on the flammability of the forest floor material at different successional ages. The mesocosms simulated the planting of four tree species (the broadleaf species Alnus glutinosa (L.) Gaertn. (Black alder) and Quercus robur L. (English oak) and the conifers Picea omorika (Pančić) Purk. (Serbian spruce) and Pinus nigra J.F. Arnold (Austrian pine)) at a reclamation site near Sokolov (NW Czechia). The mesocosms contained litter from these different tree species, placed directly on overburden soil (immature soil) or on well-developed Oe and A layers (mature soil), inoculated or not inoculated with earthworms, and incubated for 4 months. The surface material in the mesocosms was then subjected to simulated burn events, and the fire path and soil temperature changes were recorded. Burn testing showed that litter type (tree species) and soil maturity significantly influenced flammability. Pine had longer burning times and burning paths and higher post-burn temperatures than those of the other tree species. The immature soil with earthworms had significantly shorter burning times, whereas in the mature soil, earthworms had no effect. We conclude that earthworms have a significant, immediate effect on the litter flammability of immature soils. Full article

Although belowground litter decomposition critically influences lacustrine wetland soil carbon dynamics, the organ-specific microbial mechanisms driving soil organic carbon (SOC) accumulation remain unclear. Existing research has predominantly focused on aboveground litter, leaving a significant gap in the understanding of how roots and rhizomes differentially regulate carbon cycling through microbial community assembly and survival strategies. This study took Phragmites australis (a plant characteristic of lacustrine wetland) as the research object and examined how decomposing belowground litter from different organs affects microbial-mediated SOC accumulation through a one-year in situ field incubation in Jingyuetan National Forest Park, Changchun City, Jilin Province, China. Our findings reveal that root litter exhibited the highest decomposition rate, which was accelerated by intermittent flooding, reaching up to 1.86 times that of rhizome. This process enriched r-strategist microbial taxa, intensified homogeneous selection, and expanded niche width, directly promoting SOC accumulation. Rhizome litter decomposition enhanced dispersal limitation, promoted K-strategist microbial dominance, and indirectly modulated SOC through soil acidification. Mixed-litter treatments significantly enhanced SOC accumulation (up to three times higher than single-litter treatments) through synergistic nutrient release (non-additive effects < 0.04) and reinforced microbial network interactions. SOC accumulation varied significantly with the flooding regime as follows: non-flooded > intermittent flooding > permanent flooding. This study provides new insights into the microbially driven mechanisms of plant-organ-specific decomposition in the carbon cycling of wetland ecosystems. Full article

Nitrogen deposition can significantly impact soil biogeochemical cycling; however, its effects on the decomposition processes and nutrient release from leaf and twig litter in subtropical plantations remain inadequately understood. In this study, we focused on the Pinus yunnanensis Franch. forest in the central Yunnan Plateau, southwestern China, and explored how nitrogen addition influences litter decomposition nutrient release over two years, under four levels: control (CK, 0 g·m⁻²·a⁻¹), low nitrogen (LN, 10 g·m⁻²·a⁻¹), medium nitrogen (MN, 20 g·m⁻²·a⁻¹), and high nitrogen (HN, 25 g·m⁻²·a⁻¹). The results indicate that after 24 nitrogen application treatments, the rates of remaining mass in both leaf and twig litters followed the pattern: LN < CK = MN < HN. Under all nitrogen application treatments, the rate of remaining mass in leaf litters was significantly lower than that of twig litters (p < 0.05). Under LN, the mass retention in leaf and twig litters decreased by 3.96% and 8.41%, respectively, compared to CK. In contrast, under HN treatments, the rates of remaining mass in leaf and twig litters increased by 8.57% and 5.35%, respectively. This demonstrates that low nitrogen accelerates decomposition, whereas high nitrogen inhibits it. Significant differences in the remaining amounts of lignin and cellulose in both leaf and twig litters were observed when compared to CK (p < 0.05). Additionally, decomposition time and nitrogen deposition had significant effects on the remaining rates of nutrients (C, N, P) and their C/N, C/P, and N/P in litters (p < 0.05). Following nitrogen application, the C/N of the litters significantly reduced, while the N/P increased. The results suggest that nitrogen addition alleviates the nitrogen limitation on the litters while intensifying the phosphorus limitation. Full article

In terrestrial ecosystems, the decomposition of early spring ephemeral plant litter (ESPL for short) is one of the important processes in the carbon and nutrient cycles during the early spring stage. The current study focused on four typical spring ephemeral plant species in three forest types of Northeast China and investigated the decomposition characteristics of herb litters, using litterbag decomposition experiments. The study results indicate that the mass loss rate of ESPL decomposition after 50 days can be as high as 73.15% to 80.44%. Throughout the entire decomposition period, there is a significant correlation between the decomposition of ESPL and time, with initial decomposition relatively fast and later decomposition slowing down. Overall, Hylomecon japonicum exhibits slightly faster decomposition, and Cardamine leucantha decomposes relatively slowly, while Cardamine leucantha shows the highest mass loss rate in the first 10 days, reaching 38.71%. The mass loss rates of the four types of ESPL are significantly correlated with the litter nutrient conditions, as are the stage-specific mass loss rates. Furthermore, there are distinct differences in the nutrient composition affecting the decomposition of different types of ESPL. Across different forest stands, influenced by different decomposition environments, such as soil conditions, the decomposition of ESPL is fastest in the deciduous broad-leaved forest, with decomposition reaching 50% and 95% in only 15–18 days and 63–88 days, respectively. In the broad-leaved forest, it takes 18–23 days and 78–110 days, while, in the birch forest, it takes 22–32 days and 99–136 days. Full article

With global warming, understanding the effect of elevated temperature on the decomposition of Chinese fir needle litter has significant implications for nutrient cycling, yield, and management of economically important Chinese fir plantations. We conducted simulated warming decomposition experiments in incubators at 25 °C, 30 °C, and 35 °C on Chinese fir needle litter from middle-aged, mature, and overmature stands. Changes in litter mass and concentrations of some metallic elements and recalcitrant components were measured in litter sampled at different decomposition time-steps up to 264 days (d). Warming to 35 °C significantly increased the mass loss rate of needle litter from overmature stands throughout the experiment (except at 72 d). The effect of warming on litter mass loss rate for middle-aged and mature stands was lower and is attributed to higher litter quality in these stands. Compared to 25 °C, warming to 30 °C and 35 °C increased the needle litter decomposition rate across all developmental stages by 17.3% and 48.3%, respectively. Potassium (K), calcium (Ca), and magnesium (Mg) were mostly released during needle litter decomposition in all Chinese fir developmental stages. Lignin, condensed tannins, total phenols, and cellulose were enriched in needle litter, while the release of hemicellulose from near the start of the decomposition experiment was attributed to its lower molecular weight compared with other carbohydrates in litter. Compared with 25 °C, warming to 35 °C increased the release rates from litter of K, Ca, and Mg by 14.7%, 24.6%, and 21.5%, and the release rates of lignin, total phenols, cellulose, and hemicellulose by 7.5%, 8.8%, 10.4%, and 13.7%. Needle litter iron (Fe), aluminum (Al), and sodium (Na) in different development stages and manganese (Mn) in the overmature stands were mostly enriched during the experiment. Warming significantly promoted the enrichment of Fe, Al (except for mature stands), and Na, and reduced the enrichment of Mn. In summary, the sensitivity of needle litter to temperature in overmature stands is higher than that in middle-aged and mature stands, suggesting that forest managers can extend the rotation length of Chinese fir plantations to increase the yield of large-diameter timber, litter decomposition, and ecosystem nutrient return. Full article

Arbuscular mycorrhizal (AM) fungi are one of the most widely distributed microorganisms in all terrestrial ecosystems, playing an important role in supplying nitrogen (N) and phosphorus (P) to plants and in nutrient cycling. The contribution discusses the responses of rises in temperature and atmospheric N deposition to stoichiometric features of plant–soil–litter–microorganism–soil hydrolases in forest ecosystems. It summarizes the role that AM fungi play in the context of global change in carbon (C), N, and P stoichiometric characteristics of forest plant–soil systems. In this study, under conditions of warming with N application, it said the AM fungi will strongly influence the stoichiometric characteristics of C, N, and P in forest ecosystems. In addition to that, the presence of AM fungi may weaken certain impacts of global change on nutrient limitations in plants, increasing their plant dependency on mycorrhizal symbionts. AM fungi also seem to control soil nutrient transformation but simultaneously enhance soil nutrient stability, accelerate litter decomposition, and shorten the cycling time of litter C, N, and P. Full article

Knowledge about the decomposition of litter in signal grass pastures is still limited, especially in pastures managed under deferred grazing. Thus, we aimed to evaluate the chemical composition, carbon/nitrogen (C/N) ratio, and decomposition rate of litter in signal grass (Urochloa decumbens cv. Basilisk) pastures not fertilized with N (U0), fertilized with 50 kg·N·ha⁻¹ (U50), fertilized with 100 kg·N·ha⁻¹ (U100), and intercropped with calopo (Calopogonium mucunoides Desv.) (UC), managed under deferred grazing at different incubation times for two experimental periods (2017–2018 and 2018–2019). Data were analyzed using a randomized block experimental design with four management systems and two blocks, each containing two replicates per treatment. Nitrogen sources increased the N concentrations in the litter before incubation. Nitrogen concentrations in the incubated litter were affected by the incubation times and periods, increasing over time, mainly for U50 and U100. U100 litter samples exhibited higher acid detergent insoluble nitrogen (ADIN) levels than the U0 litter samples only in period 2. Notably, the C/N ratio did not differ with the different management systems; however, it decreased with increasing incubation times and periods, with final values of 24:1 and 26:1 in periods 1 and 2, respectively. Overall, litter samples from pastures fertilized with chemical or biological N sources exhibited higher N concentrations, but their incubated litter samples exhibited higher ADIN concentrations. However, management systems did not affect C/N ratios and no differences in litter biomass decomposition were observed among the systems, possibly due to the grazing period occurring prior to litter sampling. Full article

Forest leaf litter is an important source of soil nutrients, but how its decomposition products affect the availability of soil heavy metals is not totally clear. In order to understand the effects of leaf litter decomposition on soil heavy metal availability in a forest ecosystem, leaf litter samples were collected from Daluoshan in Wenzhou and the Wuyanling National Nature Reserve of Zhejiang and subjected to analysis. The leaf litter was produced by the forests’ dominant tree species, such as Myrica ruba, Bambusa cerosissima, Pinus sylvestris, Machilus thunbergia, Cunninghamia lanceolata, and Quercus acutissima. Decomposition of the leaf litter samples at room temperature and leaching decomposition of the samples were carried out to analyze the acid production characteristics of the litter samples and their impact on soil heavy metal availabilities. Oxalic acid, lactic acid, fumaric acid, succinic acid, malic acid, and citric acid were the dominant organic acids in the leaf litter decomposer, and the sum of these six organic acids accounted for more than 50% of the total organic acid. During a 30-day litter decomposition, the levels of organic acids basically increased, with significant increases appearing in the early stage. After leaching, the available contents of Cr, Mn, Ni, Cu, Zn, As, Cd, and Pb increased by a maximum of 11.95, 2.33, 12.00, 0.80, 0.83, 0.54, 51.50, and 0.28-fold, respectively, compared with those of the original soil sample. During leaching, the higher the content of low molecular weight organic acids in the leaf litter, the longer the leaching time required and the more obvious the influence on the level of available heavy metals. A stronger leaching effect was found for the soil samples taken from a depth of 0–20 and 20–40 cm accompanied by a more obvious increase in the available heavy metals in the soil. PLSPM results showed that there were significant differences between the soil acidity index and the available heavy metals in Daluoshan (p < 0.05) and that there were significant differences between the soil acidity index and the available heavy metals in Wuyanling (p < 0.01). The decomposition of litter produced low molecular weight organic acids, which caused a decrease in soil pH and an increase in exchangeable H⁺ and Al³⁺. Both changes had an impact on soil organic matter and further led to an increase in the activity of heavy metals in the soil. This will further lead to the increase of ecological and environmental risks to forest soil. Full article

In northern hardwood forests, litter decomposition might be affected by nutrient availability, species composition, stand age, or access by decomposers. We investigated these factors at the Bartlett Experimental Forest in New Hampshire. Leaf litter of early and late successional species was collected from four stands that had full factorial nitrogen and phosphorus additions to the soil and were deployed in bags of two mesh sizes (63 µm and 2 mm) in two young and two mature stands. Litter bags were collected three times over the next 2 years, and mass loss was described as an exponential function of time represented by a thermal sum. Litter from young stands had higher initial N and P concentrations and decomposed more quickly than litter from mature stands (p = 0.005), regardless of where it was deployed. Litter decomposed more quickly in fine mesh bags that excluded mesofauna (p < 0.001), which might be explained by the greater rigidity of the large mesh material making poor contact with the soil. Neither nutrient addition (p = 0.94 for N, p = 0.26 for P) nor the age of the stand in which bags were deployed (p = 0.36) had a detectable effect on rates of litter decomposition. Full article

Litter decomposition is a crucial biochemical process regulated by microbial activities in the forest ecosystem. However, the dynamic response of the fungal community during litter decomposition to vegetation changes is not well understood. Here, we investigated the litter decomposition rate, extracellular enzyme activities, fungal community, and nutrient cycling-related genes in leaf and twig litters over a three-year decomposition period in a pure Liquidamabar formosana forest and a mixed L. formosana/Pinus thunbergii forest. The result showed that during the three-year decomposition, twig litter in the mixed forest decomposed faster than that in the pure forest. In both leaf litter and twig litter, β-cellobiosidase and N-acetyl-glucosamidase exhibited higher activities in the mixed forest, whereas phosphatase, β-glucosidase, and β-xylosidase were higher in the pure forest. The fungal α-diversity were higher in both litters in the pure forest compared to the mixed forest, with leaf litter showing higher α-diversity than twig litter. Fungal species richness and α-diversity within leaf litter increased as decomposition progressed. Within leaf litter, Basidiomycota dominated in the mixed forest, while Ascomycota dominated in the pure forest. Funguild analysis revealed that Symbiotroph and ectomycorrhizal fungi were more abundant in the mixed forest compared to the pure forest. In the third-year decomposition, genes related to phosphorus cycling were most abundant in both forests, with the pure forest having a higher abundance of cex and gcd genes. Fungal community structure, predicted functional structure, and gene composition differed between the two forest types and between the two litter types. Notably, the fungal functional community structure during the first-year decomposition was distinct from that in the subsequent two years. These findings suggest that dominant tree species, litter quality, and decomposition time all significantly influence litter decomposition by attracting different fungal communities, thereby affecting the entire decomposition process. Full article

Allelopathy is an underlying and controversial mechanism for detrimental environmental effects in the management of Eucalyptus plantations. However, little attention has been paid to the dynamics of allelochemicals and phytotoxicity in soil fauna during litter decomposition. To explore the relationship between the dynamics of phytotoxicity and allelochemicals, a decomposition experiment was conducted using 4-year-old and 8-year-old Eucalyptus grandis litter (0, 10, 20, 30, and 45 days). The acute toxicity of Eisenia fetida was assessed, and a chemical analysis of the eucalyptus leaves was performed. Biochemical markers, including total protein, acetylcholinesterase (AChE) activity, and oxidative stress levels (SOD and MDA) were measured. A comet assay was used to determine DNA damage in E. fetida cells. The results showed that after 20–30 days of decomposition, E. grandis litter exhibited stronger phytotoxic effects on E. fetida in terms of growth and biochemical levels. After 20 days of decomposition, the weight and total protein content of E. fetida first decreased and then increased over time. SOD activity increased after 20 days but decreased after 30 days of decomposition before increasing again. MDA content increased after 20 days, then decreased or was stable. AChE activity was inhibited after 30 days of decomposition and then increased or stabilized with further decomposition. Soluble allelochemicals, such as betaine, chlorogenic acid, and isoquercitrin, significantly decreased or disappeared during the initial decomposition stage, but pipecolic acid significantly increased, along with newly emerging phenolic fractions that were present. More allelochemicals were released from 8-year-old litter than from 4-year-old E. grandis litter, resulting in consistently more severe phytotoxic responses and DNA damage in E. fetida. Scientific management measures, such as the appropriate removal of leaf litter in the early stages of decomposition, might help support greater biodiversity in E. grandis plantations. Full article

Litter’s chemical complexity influences carbon (C) cycling during its decomposition. However, the chemical and microbial mechanisms underlying the divergence or convergence of chemical complexity under UV radiation remain poorly understood. Here, we conducted a 397-day field experiment using ¹³C cross-polarization magic-angle spinning nuclear magnetic resonance (¹³C-CPMAS NMR) to investigate the interactions among the initial chemistry, microbial communities, and UV radiation during decomposition. Our study found that the initial concentrations of O-substituted aromatic C, di-O-alkyl C, and O-alkyl C in Deschampsia caespitosa were higher than those in Kobresia tibetica. Litter’s chemical composition exhibited divergent patterns based on the initial chemistry, UV radiation, and decay time. Specifically, D. caespitosa consistently displayed higher concentrations of di-O-alkyl C and O-alkyl C compared to K. tibetica, regardless of the UV exposure and decay time. Additionally, litter’s chemical complexity was positively correlated with changes in the extracellular enzyme activities, particularly those involved in lignin, cellulose, and hemicellulose degradation, which accounted for 9%, 20%, and 4% of the variation in litter’s chemical complexity, respectively. These findings highlighted the role of distinct microbial communities in decomposing different C components through catabolism, leading to chemical divergence in litter. During the early decomposition stages, oligotrophic Planctomycetes and Acidobacteria metabolized O-alkyl C and di-O-alkyl C under UV-blocking conditions. In contrast, copiotrophic Actinobacteria and Chytridiomycota utilized these components under UV radiation exposure, reflecting their ability to thrive under UV stress conditions due to their rapid growth strategies in environments rich in labile C. Our study revealed that the inherent differences in the initial O-alkyl C and di-O-alkyl C contributed to the chemical divergence, while UV radiation further influenced this divergence by shifting the microbial community composition from oligotrophic to copiotrophic species. Thus, differences in the initial litter chemistry, microbial community, and UV radiation affected the quantity and quality of plant-derived C during decomposition. Full article

Headwater streams are reliant on riparian tree leaf litterfall to fuel brown food webs. Terrestrial agents like herbivores and contaminants can alter plant growth, litter production, litter quality, and the timing of litterfall into streams, influencing aspects of the brown food web. At Mount St. Helens (USA), early successional streams are developing willow (Salix sitchensis) riparian zones. The willows are attacked by stem-boring herbivores, altering litter quality and the timing of litterfall. Within a established experimental plots, willows (male and female plants) were protected from herbivores using insecticides and provided with experimental additions of nitrogen. This enabled us to test the interacting influences of herbivores, nitrogen deposition, and willow sex on leaf litter quality, aquatic litter decomposition, and microbial and invertebrate detritivores. We found weak litter quality effects (higher N and lower C:N) for the herbivore treatment, but no effect of nitrogen deposition. Although litter decomposition rates were not strongly affected by litter treatments, detritivore communities were altered by all treatments. Nitrogen deposition resulted in decreased bacterial richness and decreased fungal diversity in-stream. Aquatic macroinvertebrate communities were influenced by the interacting effects of herbivory and nitrogen addition, with abundances highest in herbivore litter with the greatest N addition. Shredders showed the highest abundance in male, herbivore-attacked litter. The establishment of riparian willows along early successional streams and their interacting effects with herbivores and nitrogen deposition may be influencing detritivore community assembly at Mount St. Helens. More broadly, global changes like increased wet and dry N deposition and expanded ranges of key herbivores might influence tree litter decomposition in many ecosystems. Full article

Flammable litter such as Pinus koraiensis needle accumulation increases the risk of wildfire. In the event of a high-intensity fire, forest resources can be severely damaged. To reduce the occurrence of forest fires, it is important to reduce loads and modify structures. This study conducted 270 indoor degradation experiments to determine physicochemical properties of Pinus koraiensis during the combustion degradation process. Combustion degradation treatment variables were constructed with different durations, Trichoderma fungi, and doses. The results show that the physicochemical properties of flammable litter changed significantly after degradation, with a maximum degradation rate of 11. The degradation rate was affected by time and microbial agents, but there was no significant difference between different doses. Principal component analysis was used to determine overall combustibility, and it was found that a dose of 4 mL of Trichoderma harzianum had the best effect on degradation for 42 days, reducing combustibility by 203%. It was found that the 6ml composite mould had the best inhibitory effect on fire spread rate, reaching the lowest value. After 42 days, the flame intensity of 4 mL Trichoderma harzianum reached its lowest value of 57.17 kw/m, which represents a decrease of 54% compared to the initial value. Similarly, the flame’s length reached its lowest value of 4.91 cm, which represents a decrease of 31% compared to the same period last year. The aim of this study is to establish the relationship between time, microbial agents, dosage, flammable physical and chemical properties, overall flammability, and potential fire behaviour. The values of the goodness-of-fit index and the comparative fit index are both >0.98, and the values of the standardised root mean square residual and the approximate root mean square error are both <0.05. This study has a positive effect on accelerating the decomposition of combustibles, reducing the content of flammable components, reducing flammability and potential fire behaviour, and reducing the risk of forest fires. It is of great significance for strengthening natural resource management and forest ecological conservation. Full article

Litter of different species coexists in the natural ecosystem and may induce non-additive effects during decomposition. Identifying and quantifying the origins of species in litter mixtures is essential for evaluating the responses of each component species when mixed with co-occurring species and then unraveling the underlying mechanism of the mixing effects of litter decomposition. Here, we used near-infrared spectroscopy (NIRS) to predict the species composition and proportions of four-tree species foliage mixtures in association with litter crude ash and litter decomposition time. To simulate the whole mixed litter decomposition process in situ, a controlled mixture of four tree species litter leaves consisting of 15 tree species combinations and 193 artificial mixed-species samples were created for model development and verification using undecomposed pure tree species and decomposed litter of single tree species over one year. Two series of NIRS models were developed with the original mass and ash-free weight as reference values. The results showed that these NIRS models could provide an accurate prediction for the percentage of the component species from in the litter leaf mixture’s composition. The predictive ability of the near-infrared spectroscopy model declined marginally with the prolonged litter decomposition time. Furthermore, the model with ash-free litter mass as a reference exhibited a higher coefficient of determination (R²) and a lower standard error of prediction (RMSECV). Thus, our results demonstrate that NIRS presents great potential for not only predicting the organic composition and proportion in multi-species mixed samples in static conditions, but also for samples in dynamic conditions (i.e., during the litter decomposition process), which could facilitate evaluation of the species-specific responses and impacts on the interspecific interactions of co-occurring species in high-biodiversity communities. Full article