Search Results (38)

Litter decomposition is a fundamental ecological process that drives nutrient cycling and energy flow. However, little is known about the elevational patterns of this process in different stages. We established ten sites on Dongling Mountain in Beijing, China, to investigate the elevational patterns of oak leaf (Quercus liaotungensis) decomposition, as well as the underlying mechanisms. Our results revealed distinct elevational patterns of litter decomposition in different stages. There was no significant altitudinal pattern in the mass loss of Q. liaotungensis leaves at the 2nd, 4th, and 6th months of decomposition. By the 16th month, the mass loss decreased significantly along the elevation gradient (p = 0.008). By the 28th month, a reverse pattern emerged, with greater mass loss observed at higher elevations (p < 0.001). A similar change also took place in the altitudinal pattern of the abundance of invertebrates within the litter bag, which was lower at higher elevations at the 16th month (p = 0.002), but higher at higher elevations at the 28th month (p = 0.002). In addition, we examined the elevational patterns of carbon and nitrogen concentrations in different stages. The results of the structural equation model revealed that the invertebrate abundance at the 4th month influenced the litter residues at the 16th month (p < 0.001), yet nitrogen content at the 16th month affected litter residues at the 28th month(p < 0.001). This study provides novel insights into the temporal dynamics of litter decomposition along an elevational gradient and highlights the underlying mechanisms by which litter chemistry and biological factors regulate this process. Full article

The impact of nitrogen and phosphorus deposition alternations, as well as apoplastic litter quality and quantity, on soil nutrient cycling and soil carbon pool processes in forest ecosystems is of considerable importance. Soil ecological enzyme chemistry is a powerful tool for elucidating the nutrient limitations of microbial growth and metabolic processes. In order to explore the responding mechanisms of soil ecological enzyme chemistry to the simultaneous changes in apoplast input and nitrogen and phosphorus deposition in temperate coniferous and broad-leaved mixed forests, an outdoor simulating experiment was conducted. The results demonstrate that the treatments involving apoplastic material and nitrogen and phosphorus additions had significantly impacted soil nutrient levels across different forest types. Apoplastic treatments and N-P additions had a significant effect on the soil total organic carbon (TOC), dissolved organic carbon (DOC), soil total soluble nitrogen (TSN), soil available phosphorus (SAP), soil total nitrogen (TN), soil total phosphorus (TP), and microbial biomass carbon (MBC). However, the effects on soil microbial biomass (MBN) and microbial biomass phosphorus (MBP) were insignificant. The apomictic treatments with N and P addition did not result in a statistically significant change in soil C-hydrolase activities (β-1,4-glucosidase BG, β-1,4-xylosidase BX, cellobiohydrolase CBH, phenol oxidase POX, and peroxidase PER), N-hydrolase activities (β-1,4-N-acetylglucosaminidase NAG and L-leucine aminopeptidase LAP), or P-hydrolase activities (Acid phosphatase AP). Although the apomictic treatments did not yield a significant overall impact on carbon hydrolase activity, they influenced the activity of specific enzymes, such as CBH, LAP, and PER, to varying degrees. The effects on BG, BX, CBH, AP, and C-hydrolase activities were significant for different stand types. The impact of apomictic treatments and N-P additions on soil nitrogen hydrolase activities was inconsequential with a minimal interactive effect. The highest correlation between PER, LAP, and N-hydrolase activities was observed in conjunction with elevated levels of nitrogen and phosphorus addition (N3L0, original litter treatment, and high amounts of N and P addition). These findings may provide a theoretical foundation for the management of ecosystem function in broad-leaved Korean pine forests. Full article

Soil organic matter (SOM) is essential for nutrient cycling and soil carbon (C) accumulation, both of which are heavily influenced by the quality and quantity of plant litter. Since SOM dynamics in relation to plant diversity are poorly understood, we investigated the effects of willow variety and mixture, and site on the soil C stocks, SOM chemical composition and thermal stability. Using pyrolysis-field ionization mass spectrometry (Py-FIMS), a method of stepwise thermal degradation in ultrahigh vacuum combined with soft ionization in a high electric field, followed by mass-spectrometric separation and detection of molecular ions, we analyzed SOM in the top 10 cm of soil from two 7-year-old experimental sites in Germany and Sweden. Monocultures and mixtures of two willow varieties (Salix spp.) belonging to different species were grown at the experimental plots. Overall, site had the strongest effect on SOM quality. The results showed significant variability across sites for willow identity and mixture effects on C accumulation and SOM chemistry. In the German site (Rostock), yearly soil C accumulation was higher (p < 0.05) for variety ‘Loden’ (1.0 Mg C ha⁻¹ year⁻¹) compared to ‘Tora’ (0.5 Mg C ha⁻¹ year⁻¹), whilst in the Swedish site (Uppsala), both varieties exhibited similar soil C accumulation rates of around 0.6 Mg C ha⁻¹ year⁻¹. Willow variety identity significantly affected SOM quality at both sites, while mixing had minor effects. Our findings emphasize the significance of site-specific context and variety and species identity in shaping soil C accumulation in willow plantations. Full article

This study investigates the production of biochar from fresh wood shavings (B-WSF) and used wood shavings (B-WSU–animal litter) biomass through pyrolysis at 450 °C and explores its potential for NO₂ adsorption at different temperatures from 22 °C to 250 °C. The biochars’ thermal stability, elemental composition, mineral content, textural properties, and surface chemistry were comprehensively analyzed using various techniques, including thermogravimetric analysis (TGA), ultimate analysis, proximate analysis, mineral composition analysis, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and NO₂ adsorption experiments. The results indicate that biochars derived from WSF and WSU biomass possess high stability and exhibit significant changes in their elemental composition, surface functional groups, and textural properties compared to the raw biomass. The biochars demonstrated substantial NO₂ adsorption capacities and reduction, with B-WSU biochar exhibiting higher adsorption capacity attributed to its higher specific surface area, mineral content, and functional groups. In addition, the results reveal distinct patterns in NO₂ adsorption and NO release, with temperature playing a pivotal role in the process. At lower temperatures, NO₂ adsorption on both biochars exhibits gradual increases, while higher temperatures facilitate immediate adsorption and subsequent reduction to NO. The adsorption of NO₂ increased with increasing adsorption temperature, with B-WSU biochar achieving a maximum adsorption capacity of 43.54 mg/g at 250 °C, compared to 9.62 mg/g for B-WSF biochar. Moreover, XPS analysis revealed alterations in surface functional groups upon NO₂ exposure, indicating enhanced surface oxidation and formation of nitrogen-containing species. In addition, differences in surface heterogeneity and mineral content influence NO₂ adsorption behavior between the biochar samples. These findings highlight the potential of WSF biomass-derived biochar as an effective adsorbent for NO₂ removal, offering insights into its application in air pollution mitigation strategies. The mechanism of NO₂ adsorption involves chemisorption on oxygen-containing functional groups and physical adsorption, facilitated by the high specific surface area and pore volume of the biochar. Furthermore, the rich mineral content in B-WSU biochar explains its high adsorption capacity, demonstrating the potential for valorization of waste materials in the circular economy. 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

The Mediterranean Sea is an almost completely closed basin connecting several countries. Its configuration leads to its peculiarity and richness, but the intensive activities within the basin and along the coast aggravate the ecological conditions. The existing regulatory European Framework for environmental protection has already been in place through a series of legal instruments for almost 20 years. In this context, open science could play a fundamental role. The existing data must become findable, accessible, interoperable, and reusable (FAIR) to provide stakeholders and decision-makers with the instruments to understand how to improve the available information and support decisions based on the best set of existing information. Since 2009, the European Marine Observation and Data Network, EMODnet, has provided access to high-quality marine information supporting research and stakeholders’ mission and objectives. Data related to pollution are collated, validated, and published using standard protocols, formats, and vocabularies, thus becoming FAIR. For marine litter, a detailed and qualified data management system for macro- and microlitter in diverse compartments was structured. Some of these data and metadata were already used to calculate the first coastline litter baselines based on harmonized and FAIR datasets (2012–2016). The availability of these data related to the Mediterranean area is relevant, but additional work is required. Full article

The application of biochar is one of the promising management practices to alleviate soil acidification and improve soil fertility. However, it has been found to reduce the content of ammonium nitrogen (${\mathrm{NH}}_4^{+}$−N) in the soil, which is the most important form of nitrogen (N) for tea tree growth. To investigate the response of soil ${\mathrm{NH}}_4^{+}$−N content to the combined application of biochar and pruned tea plant litter, a pot trial was performed with three treatments: control (CK); biochar (BC); biochar + tea plant litter (BC + L). Soil chemistry properties and ammonification rates were determined, and the microbial community composition was analyzed by high-throughput sequencing. The results showed that the ${\mathrm{NH}}_4^{+}$−N content in BC + L treatment was 1.7–9.5 fold higher than CK and BC treatments after 15 days of application, with no difference in the proportion of ammonia oxidation phyla such as Nitrospirae. The proportion of soil fungus Ascomycota was strongly correlated with the content of soil available nitrogen (p = 0.032), and the relationship was well described by a linear equation (R² = 0.876, p = 0.01). Further redundancy analysis revealed that soil pH, soil organic carbon (SOC), the ratio of SOC to total nitrogen and the ratio of SOC to alkaline hydrolyzable nitrogen appeared to be important factors influencing the separation of BC + L from CK and BC groups. In summary, the addition of biochar and pruned tea plant litter alters soil properties and may influence the composition of microorganisms with various trophic groups, thus affecting ecosystem function. Our results also highlight the importance of returning pruned materials with biochar application in tea plantation ecosystems. Full article

Litter humification plays a crucial role in organic matter formation and soil carbon sequestration in forest ecosystems. However, how forest gap formation and gap size variation affect the litter humification process remains poorly understood. An eight-year in situ decomposition experiment was conducted to evaluate humus accumulation (humic substances, humic and fulvic acid), humification degrees, humification ratios and optical properties (ΔlogK, E4/E6 and A600/C) of Minjiang fir (Abies faxoniana Rehder & E.H.Wilson) twig litter in four gap size treatments in an alpine primitive forest on the eastern Tibetan Plateau, including (1) closed canopies, (2) small gaps (38–46 m² in size), (3) medium gaps (153–176 m² in size),and (4) large gaps (255–290 m² in size). The results indicated that the accumulation of humic substances and humic acid in the closed canopies was significantly higher than that in the large gaps during the first two years of decomposition. After eight years of decomposition, there were significant differences in the humic substance accumulations and the values of ΔlogK and A₆₀₀/C among the different gap sizes. Furthermore, twig litter was humified in the first 2 years of incubation, and the net accumulation of humic substances was ranged from −23.46% to −44.04% of the initial level at the end of the experiment. The newly accumulated humus was young (mature (type Rp) humus) and transformed to mature (type A) humus after 4–6 years of decomposition. Partial least squares (PLS) suggested that gap-induced variations in twig litter chemistry (i.e., contents of cellulose, lignin, nitrogen (N) and phosphorus (P), and the ratios of C/N N/P) mainly drove the process of twig litter humification. Our results presented here denote that the formation of forest gaps retard twig litter humification process, which might be detrimental to carbon sequestration in the alpine forest ecosystems. Full article

This study aimed to compare the effects of whole-tree and stem-only harvesting in hemiboreal forests in Latvia. Chemistry of soil solution, precipitation, litter and needles, as well as tree parameters in regenerated stands were measured from 2012 to 2021 in oligotrophic and mesotrophic Scots pine sites with mineral soils and a eutrophic Norway spruce site with drained peat soil. Compared to the undisturbed control, the soil solution pH was significantly lower and N-NO₃⁻ and K⁺ concentrations were significantly higher after stem-only harvesting at the oligotrophic site, stem-only and whole-tree harvesting at the mesotrophic site and whole-tree harvesting at the eutrophic site. The height growth of the regenerated stands in all sites was similar for both harvesting methods six years after planting. More slender trees were observed after whole-tree harvesting than after stem-only harvesting at the eutrophic site. Whole-tree harvesting produced significant negative short-term effects on height growth in the oligotrophic site four to six years after harvest. The nutrient levels of needles differed with harvest intensity but did not indicate insufficient nutrient availability with any type of harvesting. Full article

The productivity of mangrove ecosystems is associated with litterfall production, which continuously contributes large quantities of organic matter, in the form of detritus, to the food web via adjacent ecosystems. However, the degree of deterioration of mangrove ecosystems worldwide has been increasing due to anthropogenic activities, leading to the loss of vegetation cover and changes in hydrological patterns, the chemical conditions of interstitial water and soil, and the litterfall degradation rate and, thus, the integration of organic matter into the ecosystem. In this study, we investigate the relationship between leaf degradation and interstitial water chemistry in two mangrove forests located in Oaxaca, Mexico, that are characterized by differences in environmental conditions, species, and anthropogenic activity. Forty-two 10 cm × 20 cm nylon mesh bags were installed in the Rhizophora mangle forest along two flood-associated lines (21 per line), and twenty-one bags were installed centrally in the Avicennia germinans forest because of the flood conditions in this area. Three bags per line were collected each month. This material was then dried and calcined for determination of the decomposition rate (k). The in situ redox potential and interstitial water salinity of mangrove forests were measured using a HACH HQ40d multiparametric probe and A&O refractometer, and the sulfate concentration was determined by ion chromatography. The results show that daily average decomposition rates were higher in the Salina lagoon (k = 0.01 g·day⁻¹) than in the Chacahua lagoon (k = 0.004 g·day⁻¹). The degradation model was Y = 66.054e^−0.010t, R² = 0.89, p ≤ 0.05, for the Salina lagoon and Y = 67.75e^−0.004t, R² = 0.76, p ≤ 0.05, for the Chacahua lagoon. Leaf decomposition rates differed between the Salina and Chacahua lagoons (F_1,206 = 4.8, p < 0.03). In the Salina lagoon, dominated by A. germinans, an inverse relationship was established between the percentage of degraded biomass with respect to salinity concentration (R² = 0.82, p < 0.013) and redox potential (R² = 0.89, p < 0. 015), and for the Chacahua lagoon, dominated by R. mangle, the percentage of degraded litter biomass was found to be inversely correlated with redox potential (R² = 0.94, p < 0.005) and sulfate concentration (R² = 0.88, p < 0.017). Based on the results obtained in this study, we conclude that variations in the chemical conditions of interstitial water and hydrological patterns can affect the process of mangrove leaf degradation based on species and the integration of organic matter in the soil and in adjacent ecosystems. These findings are potentially useful for mangrove management because they advance understanding of the dynamics of organic matter in mangroves and the importance of maintaining the health of these ecosystems, which is necessary for the maintenance of coastal fishing production. Full article

In this work, we evaluated the effects of cultivation practices and sites (representing four locations in Crete, Greece) on soil organic carbon sequestration in established citrus orchards, olive groves, and uncultivated fields (used as a control). Soil pH, soil texture, soil organic matter (SOM), Permanganate Oxidizable Carbon (POXC), Total Kjeldahl Nitrogen (TKN), Carbon and Nitrogen ratio (C:N), as well as soil CO₂ respiration rates, and specific enzymes’ activity (i.e., N-Acetyl Glutamate (NAG), Beta Glucosidase (BG), Dehydrogenase) were determined in the upper soil layer (0–20 cm). It was shown that citrus and olive orchards under the South Mediterranean conditions could substantially increase C storage in the soil. However, soils planted with orange trees showed lower capacity than olive trees, which was related to litter chemistry (i.e., leaf C:N ratio). Sites had no significant impact on SOM. In our study, SOM had a positive relationship with TKN (and less with POXC) and the C:N ratio of the tree crop species litter. Our findings have implications for designing soil conservation practices in Mediterranean conditions and developing initiatives describing achievable targets of SOM restoration depending on soil properties and cropping systems. Full article

In this study, we describe the variation in δ¹³C value in the litter of two species of peat-forming plants: Sphagnum fuscum and Eriophorum vaginatum, during 3 years of field decomposition in oligotrophic bog ecosystems drained for the purpose of forest melioration and fire affected and at the stage of post-pyrogenic restoration. Litterbags were periodically retrieved in the autumn and the δ¹³C value in the residual litter was related to mass loss, litter chemistry, and hydrothermal conditions. Sph. fuscum decomposes much more slowly than E. vaginatum. Low rate of transformation for Sph. fuscum is observed in drained and post-pyrogenic sites, while for E. vaginatum minimal rate of transformation is observed in the native site. During the decomposition of Sphagnum residues, ¹³C enrichment occurs, and during the decomposition of E. vaginatum, we observed ¹²C enrichment. The changes in the isotope composition of carbon for investigation sites are insignificant for Sphagnum fuscum, but it was observed for E. vaginatum, the largest of ¹³C depletion is observed in the drained site (−28.3‰) and minimal in the postpyrogenic site (−27.4‰). Full article

Biochar applications to soils may enhance soil quality, hydrological properties, and agronomic productivity. Modification of biochar by activation via introduction of heteroatoms at different pyrolysis conditions can alter physical and chemical characteristics, which may enhance soil properties, although the extent of this is unknown. The objective of this study was to investigate the impacts of pyrolysis temperature (400, 500, 600, and 700 °C) on activated (activated with methanesulfonic acid) and unactivated biochar produced from poultry litter to identify optimum production conditions for end use as a soil amendment. Physical, chemical, and surface properties of biochars were determined using wet chemistry and spectroscopic analyses. Results showed that activation with methanesulfonic acid increased biochars’ oxygen content, while decreasing its point of zero charge and electrical conductivity. Conversion of raw poultry litter to activated and unactivated biochar increased concentration of P (3-fold), K (1.8-fold), Ca (3-fold), Mg (2.3-fold), and S (4.8-fold), with concentrations increasing with increasing temperatures (p < 0.05) except for C and N. Activated biochar had lower recovery of C and N, but greater water-holding capacity than unactivated biochar. Concentrations of NH₄-N, NO₃-N, and water-soluble P were greater in unactivated biochar (p < 0.05). Among all biochars, activated biochar produced at 400 °C had the lowest bulk density, total P, K, Ca, and Mg, and greatest water-holding capacity, water-soluble P, Ca, and Mg concentrations, thereby suggesting improved soil amendment characteristics and subsequent soil health under poultry litter biochars produced under these conditions. Full article

Solar radiation has been regarded as a driver of litter decomposition in arid and semiarid ecosystems. Photodegradation of litter organic carbon (C) depends on chemical composition and water availability. However, the chemical changes in organic C that respond to solar radiation interacting with water pulses remain unknown. To explain changes in the chemical components of litter organic C exposed to UV-B, UV-A, and photosynthetically active radiation (PAR) mediated by water pulses, we measured the chemistry of marcescent Lindera glauca leaf litter by solid-state ¹³C cross-polarization magic angle spinning (CPMAS) nuclear magnetic resonance (NMR) over 494 days of litter decomposition with a microcosm experiment. Abiotic and biotic factors regulated litter decomposition via three pathways: first, photochemical mineralization of lignin methoxyl C rather than aromatic C exposed to UV radiation; second, the biological oxidation and leaching of cellulose O-alkyl C exposed to PAR and UV radiation interacts with water pulses; and third, the photopriming effect of UV radiation on lignin aromatic C rather than cellulose O-alkyl C under the interaction between radiation and water pulses. The robust decomposition index that explained the changes in the mass loss was the ratio of aromatic C to O-alkyl C (AR/OA) under radiation, but the ratio of hydrophobic to hydrophilic C (hydrophobicity), the carbohydrate C to methoxyl C ratio (CC/MC), and the alkyl C to O-alkyl C ratio (A/OA) under radiation were mediated by water pulses. Moreover, the photopriming effect and water availability promoted the potential activities of peroxidase and phenol oxidase associated with lignin degradation secreted by fungi. Our results suggest that direct photodegradation of lignin methoxyl C increases microbial accessibility to lignin aromatic C. Photo-oxidized compounds might be an additional C pool to regulate the stability of the soil C pool derived from plant litter by degrading lignin methoxyl and aromatic C. Full article

Mangrove forests have proven to be resilient to most environmental change, surviving catastrophic climate events over time. Our study aimed to evaluate the chemical variability of pore water and its effect on phenological production in three mangrove species (Rhizophora mangle, Avicennia germinans, and Laguncularia racemosa) along the coast of the state of Campeche during a year of severe drought (2009) and a year of average precipitation (2010). Pore water salinity and redox potential were measured monthly in a mangrove forest in 2009 and 2010. Litterfall production and reproductive phenology was measured monthly. We determined the relationships among litterfall production, reproductive phenology, pore water chemistry and precipitation of three species between years. Precipitation, pore water salinity and redox potential significantly differed among years, seasons and sites, and also showed significant interaction between years and seasons (p < 0.05). Significant variation was observed in litterfall production, propagules, flowers, and leaf litter among sites (p < 0.05). A significant change was observed in propagules and flowers among years, and in total litterfall and leaf litter between seasons and species (p < 0.05). Under severe drought, salinity had the strongest effect on total litterfall and propagules in R. mangle, while A. germinans, had the strongest effect on propagule/flower precipitation. Both A. germinans and L. racemosa showed higher resilience than R. mangle at all sites under severe drought conditions. These findings can support activity allocation for mangrove conservation and restoration by providing the tolerance thresholds of the three species that dominate in the regional area of Campeche state. Likewise, this research provides knowledge to the Intergovernmental Experts Group on climate change about drought intensity and its magnitude of impact on mangrove productivity, reproduction and integrity. Full article