Nutrient Cycling Research Articles

“Blooming” of litter-mixing effects: the role of flower and leaf litter interactions on decomposition in terrestrial and aquatic ecosystems

Abstract. The diversity effect on decomposition, through the litter-mixing effects plays a central role in determining the nutrient and carbon dynamics in ecosystems. However, the litter-mixing effects are centered on a leaf litter perspective. Important aspects related to intraspecific interaction and biomass concentration are rarely evaluated, even though they could be essential to determine the litter decomposition dynamics. To our knowledge, we introduced a new perspective to evaluate whether and how the interaction between flower and leaf litter affects the occurrence, direction, and magnitude of litter-mixing effects in terrestrial and aquatic ecosystems. We performed laboratory experiments using flower and leaf litter from the yellow trumpet tree Tabebuia aurea (Silva Manso) Benth. and Hook. f. ex. S. Moore as a model. To obtain realistic results, we manipulated various scenarios of flower : leaf litter biomass proportion and measured 13 functional traits. Litter-mixing effects were consistent in both aquatic and terrestrial environments, with faster decomposition of both litter types in mixtures compared to their monocultures (synergistic effects). Litter-mixing effects were stronger in the terrestrial environment and at higher flower : leaf litter biomass proportions. Our results indicate that synergistic outcomes are mainly associated with complementary effects. Flower litter had a higher concentration of labile C compounds, N, P, and K and lower lignin concentrations, representing a labile litter, while leaf litter had a higher concentration of lignin, Ca, Mg, and Na, representing a refractory litter. Our results demonstrate the importance of litter-mixing effects between flower and leaf litter via complementary effects. These results shed light on the secondary consequences of flower litter on decomposition, suggesting that species with high reproductive investment in flower biomass may play an important role in the nutrient and carbon recycling of diverse plant communities, exerting a pivotal role in biogeochemical dynamics.

The microbial community structure and nitrogen cycle of high-altitude pristine saline lakes on the Qinghai-Tibetan plateau

The nitrogen (N) cycle is the foundation of the biogeochemistry on Earth and plays a crucial role in global climate stability. It is one of the most important nutrient cycles in high-altitude lakes. The biogeochemistry of nitrogen is almost entirely dependent on redox reactions mediated by microorganisms. However, the nitrogen cycling of microbial communities in the high-altitude saline lakes of the Qinghai-Tibet Plateau (QTP), the world’s “third pole” has not been investigated extensively. In this study, we used a metagenomic approach to investigate the microbial communities in four high-altitude pristine saline lakes in the Altun mountain on the QTP. We observed that Proteobacteria, Bacteroidota, and Actinobacteriota were dominant in these lakes. We reconstructed 1,593 bacterial MAGs and 8 archaeal MAGs, 1,060 of which were found to contain nitrogen cycle related genes. Our analysis revealed that nitrite reduction, nitrogen fixation, and assimilatory nitrate reduction processes might be active in the lakes. Denitrification might be a major mechanism driving the potential nitrogen loss, while nitrification might be inactive. A wide variety of microorganisms in the lake, dominated by Proteobacteria, participate together in the nitrogen cycle. The prevalence of the dominant taxon Yoonia in these lakes may be attributed to its well-established nitrogen functions and the coupled proton dynamics. This study is the first to systematically investigate the structure and nitrogen function of the microbial community in the high-altitude pristine saline lakes in the Altun mountain on the QTP. As such, it contributes to a better comprehension of biogeochemistry of high-altitude saline lakes.

Linking global terrestrial and ocean biogeochemistry with process-based, coupled freshwater algae–nutrient–solid dynamics in LM3-FANSY v1.0

Abstract. Estimating global river solids, nitrogen (N), and phosphorus (P), in both quantity and composition, is necessary for understanding the development and persistence of many harmful algal blooms, hypoxic events, and other water quality issues in inland and coastal waters. This requires a comprehensive freshwater model that can resolve intertwined algae, solid, and nutrient dynamics, yet previous global watershed models have limited mechanistic resolution of instream biogeochemical processes. Here we develop the global, spatially explicit, and process-based Freshwater Algae, Nutrient, and Solid cycling and Yields (FANSY) model and incorporate it within the Land Model (LM3). The resulting model, LM3-FANSY v1.0, is intended as a baseline for eventual linking of global terrestrial and ocean biogeochemistry in next-generation Earth system models to project global changes that may challenge empirical approaches. LM3-FANSY explicitly resolves interactions between algae, N, P, and solid dynamics in rivers and lakes at 1° spatial and 30 min temporal resolution. Simulated suspended solids (SS), N, and P in multiple forms (particulate or dissolved, organic or inorganic) agree well with measurement-based yield (kg km−2 yr−1), load (kt yr−1), and concentration (mg L−1) estimates across a globally distributed set of large rivers, with an accuracy comparable to other global nutrient and SS models. Furthermore, simulated global river loads of SS, N, and P in different forms to the coastal ocean are consistent with published ranges, though regional biases are apparent. River N loads are estimated to contain approximately equal contributions by dissolved inorganic N (41 %) and dissolved organic N (39 %), with a lesser contribution by particulate organic N (20 %). For river P load estimates, particulate P, which includes both organic and sorbed inorganic forms, is the most abundant form (64 %), followed by dissolved inorganic and organic P (25 % and 11 %). Time series analysis of river solid and nutrient loads in large US rivers for the period ∼ 1963–2000 demonstrates that simulated SS and N loads in different N forms covary with variations of measurement-based loads. LM3-FANSY, however, has less capability to capture interannual variability of P loads, likely due to the lack of terrestrial P dynamics in LM3. Analyses of the model results and sensitivity to components, parameters, and inputs suggest that fluxes from terrestrial litter and soils, wastewater, and weathering are the most critical inputs to the fidelity of simulated river nutrient loads for observation-based estimates. Sensitivity analyses further demonstrate a critical role of algal dynamics in controlling the ratios of inorganic and organic nutrient forms in freshwaters. While the simulations are able to capture significant cross-watershed contrasts at a global scale, disagreement for individual rivers can be substantial. This limitation is shared by other global river models and could be ameliorated through further refinements in nutrient sources, freshwater model dynamics, and observations. Current targets for future LM3-FANSY development include the additions of terrestrial P dynamics, freshwater carbon, alkalinity, enhanced sediment dynamics, and anthropogenic hydraulic controls.

Nine-year fertilization promoted C sink and mediated microbial nutrient utilization in alpine meadow soil aggregates

Increased nitrogen (N) and phosphorus (P) inputs to terrestrial ecosystems, which are caused by human activities and atmospheric deposition, significantly affect soil nutrient cycling. However, information on the variations of fertilization treatments on the nutrient utilization and carbon (C) storage mechanisms in alpine meadow soil aggregates is limited. Here, we investigated the responses of microbial nutrient utilization and C storage dynamics in soil aggregates to nine-year fertilization (N, P, and NP addition) in an alpine meadow. The results demonstrated that nine-year fertilization did not affect soil aggregate stability, however, they promoted soil organic C (SOC), total N (TN), and total P (TP) accumulation and altered the microbial nutrient-limitation patterns of soil aggregates in the alpine meadow. Compared to N and NP treatments, the P addition was optimal for improving soil aggregate-associated C storage and soil C pool management index (CMI). Furthermore, the NP treatment significantly exacerbated the microbial C limitation and microbial P limitation was significantly greater with N addition alone than with P addition alone, which was consistent with the resource allocation theory. The enhanced microbial carbon limitation caused by fertilization had no significant impact on soil aggregate-associated C storage and CMI. Simultaneously, soil nutrients and enzyme activities increased with decreasing soil aggregate size. However, these changes did not affect the microbial nutrient limitation patterns and CMI, which may have been related to the stronger nutrient protection ability of microaggregates. Therefore, nine years of fertilization increased the soil aggregate-associated C sink functions and affected soil microbial nutrient-limitation patterns by altering the soil C, N and P stoichiometry in the alpine meadow. These findings provide technical support for future alpine meadow management.

Dynamics of bubble plumes produced by breaking waves

Abstract Bubble plumes play a significant role in the air-sea interface by influencing processes such as air-sea gas exchange, aerosol production, modulation of oceanic carbon and nutrient cycles, and the vertical structure of the upper ocean. Using Acoustic Doppler Current Profiler (ADCP) data collected off the west coast of Ireland, we investigate the dynamics of bubble plumes and their relationship with sea state variables. In particular, we describe the patterns of bubble plumes vertical extension, duration and periodicity. We establish a power-law relationship between the average bubble penetration depth and wind speed, consistent with previous findings. Additionally, the study reveals a significant association between whitecapping coverage and observed acoustic volume backscatter intensity, underscoring the role of wave breaking in bubble plume generation. The shape of the probability distribution of bubble plume depths reveals a transition towards stronger and more organised bubble entrainment events during higher wind speeds. Furthermore, we show that deeper bubble plumes are associated with turbulent Langmuir number Lat∼ 0.3, highlighting the potential role of Langmuir circulation on the transport and deepening of bubble plumes. These results contribute to a better understanding of the complex interactions between ocean waves, wind, and bubble plumes, providing valuable insights for improving predictive models and enhancing our understanding of air-sea interactions.

Effects of rubber intercropping with native trees on litterfall and litter main nutrient return in Hainan Island, China

Understanding the process of litterfall production is crucial for sustainable development of plantations. However, the underlying dynamics of litterfall and its nutrient return in plantation agroforestry systems remain unclear. In this study, we investigated litterfall, including leaves, branches, flowers, and fruits, in three patterns: Hevea monoculture system (RM), Hevea–Michelia intercropping system (RAS1), and Hevea–Mytilaria intercropping system (RAS2) in Hainan Island, China. Our findings indicate that total litterfall was significantly higher in RAS1 (27,309 kg ha−1) and RAS2 (34,477 kg ha−1) than in RM (22,364 kg ha−1) and was predominantly composed of leaf litterfall in all three patterns, followed by branches, flowers, and fruits. The seasonal dynamics litterfall production of RM, RAS1, and RAS2 showed characteristic patterns. Litterfall nutrients exhibited peak and sub-peak monthly dynamics, peaking from February to March, during the dry season. Total nitrogen (TN), total phosphorus (TP), and total potassium (TK) content of annual litterfall in RAS1 significantly increased by 120 kg ha−1, 30 kg ha−1, and 139 kg ha−1, respectively, compared to those in RM, with percentage increases of 67.88%, 122.79% and 96.27%, respectively. Similarly, TN, TP, and TK content of annual litterfall in RAS2 significantly increased by 185 kg ha−1, 35 kg ha−1, and 170 kg ha−1, respectively, with percentage increases of 103.70%, 159.15% and 139.46%, respectively, for the abovementioned in RM. Litterfall showed a strong correlation with monthly average temperature, monthly minimum temperature, and monthly average wind speed, contributing 80.5%, 75.5%, 69.8%, and 69.6% to the total litterfall and its components, respectively. Further analysis indicated that monthly average temperature, monthly minimum temperature, and monthly average wind speed contributed 73.9%, 43.0%, and 66.6%, respectively, to TN, TP, and TK content of the annual litterfall, highlighting the significant influence of temperature and wind speed. These findings enhance our understanding of carbon and nutrient cycling and contribute to the sustainable management of tropical plantation ecosystems.

Soil Metaproteomics for Microbial Community Profiling: Methodologies and Challenges.

Soil represents a complex and dynamic ecosystem, hosting a myriad of microorganisms that coexist and play vital roles in nutrient cycling and organic matter transformation. Among these microorganisms, bacteria and fungi are key members of the microbial community, profoundly influencing the fate of nitrogen, sulfur, and carbon in terrestrial environments. Understanding the intricacies of soil ecosystems and the biological processes orchestrated by microbial communities necessitates a deep dive into their composition and metabolic activities. The advent of next-generation sequencing and 'omics' techniques, such as metagenomics and metaproteomics, has revolutionized our understanding of microbial ecology and the functional dynamics of soil microbial communities. Metagenomics enables the identification of microbial community composition in soil, while metaproteomics sheds light on the current biological functions performed by these communities. However, metaproteomics presents several challenges, both technical and computational. Factors such as the presence of humic acids and variations in extraction methods can influence protein yield, while the absence of high-resolution mass spectrometry and comprehensive protein databases limits the depth of protein identification. Notwithstanding these limitations, metaproteomics remains a potent tool for unraveling the intricate biological processes and functions of soil microbial communities. In this review, we delve into the methodologies and challenges of metaproteomics in soil research, covering aspects such as protein extraction, identification, and bioinformatics analysis. Furthermore, we explore the applications of metaproteomics in soil bioremediation, highlighting its potential in addressing environmental challenges.

Impacts of Climate change on soil microbial diversity, distribution and abundance

Climate change, driven by anthropogenic activities, has far-reaching consequences for our planet. Among its many impacts, changes in temperature, elevated carbon dioxide levels, and shifts in greenhouse gas concentrations significantly affect soil ecosystems. In particular, soil microbial communities play a pivotal role in nutrient cycling, organic matter decomposition, and overall soil health. Soil microbial communities respond differently to the effects of climate change, like elevated warming and precipitation. The change in climatic conditions is reported to be adversely affecting soil biological activity directly through either drying or wetting of soil or affecting their associated plants. This review delves into the intricate relationship between climate change and soil microbial abundance, diversity, and distribution. The paper also discusses climatic change pressure on soil enzymatic activity and microbial biomasses, as well as soil faunal activity, as they are key indicators of soil health in a changing climate. Soil microbial communities cope with climate change by changing their diversity and physiological characteristics and by changing their symbiotic plants, which indicates the role of soil microbes in withstanding the negative impact of climate change.

Forest and soil fungal community dynamics are fuelled by root rot pathogen‐induced gaps

Abstract Forest dynamics are driven by micro‐disturbances leading to gap formation. Root rot pathogens can cause mortality to adult trees, which die forming gaps. However, little is known about the biotic and abiotic factors that govern gap creation and expansion such as tree infection or drought resilience, and what are the consequences for nutrient cycling and soil microbiota. We studied the dynamics of gaps created by Heterobasidion abietinum in mountain silver fir (Abies alba) forests from the Spanish Central Pyrenees. Tree‐ring width information was used to evaluate growth patterns of trees located within and at the edge of gaps and under closed canopy conditions. We analysed soil nutrient content and microbial structure at different positions with respect to the gap. Soil fungal community was also characterized by sequencing the ITS2 region. Gaps created by H. abietinum ranged 582–1072 m2 and gathered large amounts of standing and laying dead wood biomass amounting to up to 500 m3 ha−1 of coarse woody debris. This indicates that tree mortality had been occurring over decades, and it was preceded by a long‐term growth decline and impaired drought resilience. Root rot affected trees beyond the current limit of the gaps leading to growth decline, preventing canopy closure and allowing the release of suppressed trees within the gap. Gap formation did neither affect soil fertility nor fungal and bacterial biomass and diversity, but long‐distance ectomycorrhizal fungi were more abundant within gaps. Synthesis. Root rot pathogens play key ecological roles in forest dynamics at fine spatial scale. Heterobasidion abietinum infection, and its interaction with drought, creates and expands gaps by killing large trees and preventing surrounding trees from closing the gap. The survival of mycorrhizal networks to gap formation suggests little disruption of soil fungal communities.

Examining The Role of Soil in Promoting Sustainable Development and Achieving the UN Sustainable Development Goals (SDGs)

Soil is a critical component of terrestrial ecosystems, playing an invaluable role in supporting plant growth, regulating water and nutrient cycles, filtering pollutants, and providing habitat for soil organisms. However, increasing pressures from human activities, including intensive agriculture, deforestation, urbanization, and climate change are degrading soils across the world. Therefore, sustainable management of soil resources is imperative to ensure continued provisioning of ecosystem services, promote sustainable development outcomes, and help us to achieve the UN Sustainable Development Goals (SDGs). This paper reviews literature across multiple disciplines to examine the vital links between soil and realization of the SDGs. Soil properties influence productivity and food security, water availability and quality, climate regulation through carbon storage, biodiversity conservation, and human health. Degraded soils undermine these ecosystem services, exacerbating poverty, hunger, and inequality. Research shows ecosystem-based approaches that prioritize soil health, including conservation agriculture, agroecology, and regenerative systems, can sustainably intensify agriculture while restoring multi-functionality. Additionally, nature-based solutions utilizing plant-soil interactions for restoration have demonstrated cost-effectiveness. Achieving land degradation neutrality is now an explicit target under the United Nations Convention to Combat Desertification (UNCCD), emphasizing the need to scale soil-focused initiatives within the SDG framework. Therefore, protecting and restoring global soil assets can serve as a nexus in policy frameworks to simultaneously advance progress across multiple SDGs.

Do Tasmanian devil declines impact ecosystem function?

Tasmanian eucalypt forests are among the most carbon-dense in the world, but projected climate change could destabilize this critical carbon sink. While the impact of abiotic factors on forest ecosystem carbon dynamics have received considerable attention, biotic factors such as the input of animal scat are less understood. Tasmanian devils (Sarcophilus harrisii)-an osteophageous scavenger that can ingest and solubilize nutrients locked in bone material-may subsidize plant and microbial productivity by concentrating bioavailable nutrients (e.g., nitrogen and phosphorus) in scat latrines. However, dramatic declines in devil population densities, driven by the spread of a transmissible cancer, may have underappreciated consequences for soil organic carbon (SOC) storage and forest productivity by altering nutrient cycling. Here, we fuse experimental data and modeling to quantify and predict future changes to forest productivity and SOC under various climate and scat-quality futures. We find that devil scat significantly increases concentrations of nitrogen, ammonium, phosphorus, and phosphate in the soil and shifts soil microbial communities toward those dominated by r-selected (e.g., fast-growing) phyla. Further, under expected increases in temperature and changes in precipitation, devil scat inputs are projected to increase above- and below-ground net primary productivity and microbial biomass carbon through 2100. In contrast, when devil scat is replaced by lower-quality scat (e.g., from non-osteophageous scavengers and herbivores), forest carbon pools are likely to increase more slowly, or in some cases, decline. Together, our results suggest often overlooked biotic factors will interact with climate change to drive current and future carbon pool dynamics in Tasmanian forests.

Effect of fear with saturated fear cost and harvesting on aquatic food chain model (plankton-fish model) in the presence of nanoparticles

Studying the interplay of phytoplankton-zooplankton-fish (PP-ZP-F) in an aquatic system is crucial for better understanding of nutrient cycling, assessing ecosystem health, predicting and mitigating harmful algal blooms, and managing fisheries in the water bodies. In order to investigate the effectiveness of nanoparticles (NPs), fear, and harvesting, this paper focuses on exploring the dynamics of a food chain model among PP-ZP-F species. We consider the fear of fish on zooplankton species (which reduces the reproduction rate of ZPs) with saturated fear cost in the presence of nanoparticles (NPs) and harvesting in fish. The system dynamics are studied from the viewpoint of proving positivity, boundedness, and uniqueness, followed by analyzing the existence and local stability of biologically feasible equilibria. Conditions for the global stability of the interior equilibrium point are also found. Furthermore, we established the transversality conditions for the occurrence of Hopf, transcritical, and saddle–node bifurcations. To validate our theoretical results, we made numerous phase portraits, time-series graphs, tables showing the extinction of species, and bifurcation diagrams. It is numerically observed that increasing the contact rate of NPs with PPs makes the system stable from chaos, and further increase of contact rate may lead to extinction. Chaos at a low contact rate can also be managed by increasing the fear level, and the chaotic behaviour at a low fear level can again be controlled by enhancing the harvesting of fish species. Over-exploitation may result in the extinction of fish, whereas fear may promote coexistence, stability, and long-term survival of the species. Increased saturated fear cost can make the system chaotic from stable dynamics. Therefore, the theoretical as well as numerical findings of our paper may be of great interest in estimating the behaviour of aquatic systems biologically and practically.

Influence of Land Use and Land Cover on the Quality of Surface Waters and Natural Wetlands in the Miranda River Watershed, Brazilian Pantanal

Water quality assessment stands as a fundamental step in water resource management. In addition to substances and organisms present in the water, land use and land cover are two factors also affecting water quality. This study analyzed the correlation and influence between water quality and land use and land cover in the Miranda River Basin (MRB) and the natural wetlands in the Pantanal Biome. Using a watershed-wide approach, results suggested that water quality management policies can be considered in terms of sub-basins (smaller planning units). The Water Quality Index (WQI) was considered GOOD or EXCELLENT throughout the MRB. It was observed that the natural wetlands have the capacity to contribute to improving the WQI, with reductions in thermotolerant coliforms and turbidity; however, high values were found for thermotolerant coliforms, a temporal increasing trend of biochemical oxygen demand (BOD), and a reduction in dissolved oxygen and total phosphorus. Conversely, in these flooded areas, trends of a decrease in dissolved oxygen and an increase in BOD levels were found. Natural wetlands play important hydrological and ecological roles in water quality, storing, removing, and cycling nutrients. They are highly relevant areas for defining watershed management and conservation strategies, environmental protection, and providing ecosystem services.

Assessing the Suitability of Animal and Food Waste Samples for Biogas Production and Fertilizer Evaluation

With increasing concerns over fossil fuel depletion and environmental pollution, research into alternative energy sources has gained significant momentum. Organic wastes, particularly from animals and food, offer a promising substrate for biogas production, providing dual benefits of energy generation and waste reduction. This study evaluates the suitability of food waste, cow regurgitates, and cow dung for biogas production through biodigestion. The objectives were to design a lab-scale biodigester, compare biomethane yields from each waste, and evaluate their effectiveness as fertilizers. The results indicate that all three samples have properties within the acceptable range for digestion. Food waste exhibited the highest methane yield with a daily biogas production of 0.4979 m³/day, corresponding to an energy content of 27,699.45 KJ/day. Cow regurgitates produced 0.2656 m³/day of biogas, yielding an energy content of 14,739.6 KJ/day. Cow dung yielded 0.3213 m³/day of biogas, translating to an energy content of 17,723.65 KJ/day. Microbial analysis indicated the presence of beneficial bacteria and fungi, such as Staphylococcus spp, Proteus vulgaris, Escherichia coli, Enterobacter aerogens, Aspergillus spp, and Mucor spp, which are advantageous for soil conditioning and nutrient cycling. The study highlights the importance of assessing physicochemical properties, nutrient content, and microbial composition to optimise biogas production and explore the potential of organic waste as a sustainable energy source and soil conditioner.

Soil Acidification Can Be Improved under Different Long-Term Fertilization Regimes in a Sweetpotato–Wheat Rotation System

Soil acidification is a significant form of agricultural soil degradation, which is accelerated by irrational fertilizer application. Sweetpotato and wheat rotation has emerged as an important rotation system and an effective strategy to optimize nutrient cycling and enhance soil fertility in hilly areas, which is also a good option to improve soil acidification and raise soil quality. Studying the effects of different fertilization regimes on soil acidification provides crucial data for managing it effectively. An eight-year field experiment explored seven fertilizer treatments: without fertilization (CK), phosphorus (P) and potassium (K) fertilization (PK), nitrogen (N) and K fertilization (NK), NP fertilization (NP), NP with K chloride fertilization (NPK1), NP with K sulfate fertilization (NPK2), and NPK combined with organic fertilization (NPKM). This study focused on the soil acidity, buffering capacity, and related indicators. After eight years of continuous fertilization in the sweetpotato–wheat rotation, all the treatments accelerated the soil acidification. Notably, N fertilization reduced the soil pH by 1.30–1.84, whereas N-deficient soil showed minimal change. Organic fertilizer addition resulted in the slowest pH reduction among the N treatments. Both N-deficient (PK) and organic fertilizer addition (NPKM) significantly increased the soil cation exchange capacity (CEC) by 8.83% and 6.55%, respectively, compared to CK. Similar trends were observed for the soil-buffering capacity (pHBC). NPK2 increased the soil K+ content more effectively than NPK1. NPKM reduced the sodium and magnesium content compared to CK, with the highest magnesium content among the treatments at 1.60 cmol·kg−1. Regression tree analysis identified the N input and soil magnesium and calcium content as the primary factors influencing the pHBC changes. Structural equation modeling showed that the soil pH is mainly influenced by the soil ammonium N content and pHBC, with coefficients of −0.28 and 0.29, respectively. Changes in the soil pH in the sweetpotato–wheat rotation were primarily associated with the pHBC and N input, where the CEC content emerged as the main factor, modulated by magnesium and calcium. Long-term organic fertilization enhances the soil pHBC and CEC, slowing the magnesium reduction and mitigating soil acidification in agricultural settings.

Nitrogen addition and precipitation reduction alter ecosystem multifunctionality and decrease soil nematode abundance and trophic energy fluxes in a temperate forest

Soil biota and energy flow within their food webs have a profound impact on various ecosystem functions. However, there are still significant gaps in our understanding of how climate change factors, such as nitrogen deposition and reduced precipitation, impact ecosystem functioning, particularly in temperate forest ecosystems. In this study, we evaluated the response of ecosystems to long-term nitrogen deposition and/or reduced precipitation due to climate change. We assessed these responses by examining nematode community energy fluxes and their associated ecosystem multifunctionality. Field experiments were conducted in a temperate forest to simulate nitrogen deposition (5.0 kg N·ha−1·yr−1) using NH4NO3 application and to reduce precipitation (to 70 % of a normal year) using rain shelters. Our findings showed that nitrogen addition and/or precipitation reduction treatments altered soil nematode composition. Nitrogen addition alone reduced the abundance and energy fluxes of high trophic groups such as omnivore-predators, which served as proxies for total abundance and energy fluxes. In contrast, precipitation reduction did not exhibit significant effects on overall abundance and energy fluxes. Environmental factors influencing changes in soil nematode abundance and energy fluxes included soil pH, NH4+-N, and total nitrogen in the soil. Nitrogen addition increased ecosystem multifunctionality by promoting nutrient cycling, while precipitation reduction promoted plant productivity and inhibited carbon cycling, without changing ecosystem multifunctionality. Regression analysis showed that soil nematode energy fluxes were negatively correlated with ecosystem multifunctionality. The effects of these two factors on soil nematode food webs showed temporal variation, as well as indicators related to multiple functions of the ecosystem. Our study suggests that soil nematode energy fluxes are more sensitive than nematode abundance for quantifying the relationship between biodiversity and ecosystem multifunctionality.

A global atlas of soil viruses reveals unexplored biodiversity and potential biogeochemical impacts

Historically neglected by microbial ecologists, soil viruses are now thought to be critical to global biogeochemical cycles. However, our understanding of their global distribution, activities and interactions with the soil microbiome remains limited. Here we present the Global Soil Virus Atlas, a comprehensive dataset compiled from 2,953 previously sequenced soil metagenomes and composed of 616,935 uncultivated viral genomes and 38,508 unique viral operational taxonomic units. Rarefaction curves from the Global Soil Virus Atlas indicate that most soil viral diversity remains unexplored, further underscored by high spatial turnover and low rates of shared viral operational taxonomic units across samples. By examining genes associated with biogeochemical functions, we also demonstrate the viral potential to impact soil carbon and nutrient cycling. This study represents an extensive characterization of soil viral diversity and provides a foundation for developing testable hypotheses regarding the role of the virosphere in the soil microbiome and global biogeochemistry.

Green Microbe Profile: Rhizophagus intraradices—A Review of Benevolent Fungi Promoting Plant Health and Sustainability

Arbuscular mycorrhizal fungi (AMF) such as Rhizophagus intraradices (formerly known as Glomus intraradices) are of great importance to maintaining the soil ecosystem while supporting sustainable agriculture and practices. This review explores the taxonomy of Rhizophagus intraradices, their attributes, mycorrhizal symbiosis, plant growth improvement, nutrient recycling in the soil, soil health and environmental rehabilitation, and challenges that impede the effective use of AMF in agriculture. AMF impacts soil structure by releasing organic compounds like glomalin, improving total organic carbon and water-holding capacity, and reducing water scarcity. AMF, in sustainable agriculture, not only improves crop productivity through nutrient uptake but also enhances soil fertility and plants’ resistance to so-called stress from abiotic factors as well. The integration of AMF with other beneficial microorganisms in organic farming will be powerful both to ensure long-term soil output and to protect food from bacteria. Nevertheless, chemical inputs and spatial biases of the researchers remain matters to be solved in connection with the broad feasibility of AMF use.

Vertical dynamics of soil organic carbon across Shaanxi Province, China from 1980s to 2010s

AbstractDynamics of soil organic carbon (SOC) has been paid great emphasis for its linkage to the nutrient cycling as well as the global climate changes. Despite the extensive changes in land use, climate, and field management practices that have profoundly affected SOC in Shaanxi Province, few studies have investigated the vertical dynamics of SOC across different soil depths. In this paper, we investigated vertical (0–100 cm with 20 cm intervals) changes of SOC based on soil surveys conducted in 1980s and 2010s in Shaanxi Province as well as three subregions (LP, GP, and QM) by using Geographic Regression Weighted Kriging (GRWK) method. The results indicated that the first four soil layers received 0.87, 0.79, 0.48, and 0.34 g/kg SOC increments, respectively, while SOC decreased by 0.49 g/kg in 80–100 cm. Spatially, most of study area received slight SOC increment (0–2 g/kg) among all soil layers, significant (>4 g/kg) SOC increments were distributed in the junction area of three subregions, while significant (<−4 g/kg) SOC decrement area was occurred in the western QM. SOC was increased in first four soil layers and decreased in 80–100 cm in LP relating to the implement of revegetation program that many cultivated land changed into grassland and forestland. SOC was increased in first two layers and decreased in last three layers in GP relating to the intensive agricultural activities, and it was decreased in the top layers and increased in sublayers in QM due to decreasing trend of NDVI in the western QM. Even several anthropogenic and environmental variables were highly related to SOC dynamics in Shaanxi, human activities were significantly controlled SOC changes than the natural factors.

Effects of ant mounds construction on the carbon cycle in a drained peatland, Northeast China

Acting as ecosystem engineers, ant activities are significantly crucial in altering carbon (C) cycles by modifying the energy flows and nutrient cycles in soils. However, how ant mound constructions reshape soil organic carbon (SOC) pool heterogeneity and stability remains elusive. In this study, we compared differences in soil properties, vegetation biomass, greenhouse gas (GHG) emission, and molecular composition of SOC between ant mounds and nearby soils from a drained peatland, intending to decipher factors that govern carbon dynamics during ant excavates. Results indicated that ant mound construction simultaneously caused a decrease in SOC contents and an increase in nutrient level (total nitrogen and phosphorus), dissolved organic carbon (DOC), and its proportion to SOC (DOC/SOC) dramatically. The proportions of pyrolytic products derived from lignin, phenol, and aromatics decreased significantly from 31.70 % in nearby soils to 27.43 % in ant mounds. However, no significant difference in iron-bound organic carbon (OC-Fe) was found between ant mounds and nearby soils (p > 0.05). Ant mound building greatly accelerated SOC mineralization, with average CO2 emission fluxes 1–2 times higher than that in nearby soils. Notably, CH4 emissions from ant mounds was negative, meaning ant mounds acted as CH4 sinks. Meanwhile, net CH4 flux emission into the atmosphere from nearby soils were positive. Both plant biomass and SOC density (SOCd) in ant mounds were considerably lower than those observed in nearby soils. The structural equation model indicated that soil nutrient enrichment in ant mounds indirectly stimulated SOC decomposition by stimulating microbial abundance. Still, ant mounds construction had direct positive effects on labile carbon components accumulation and posed negative effects on resistant SOC compounds. Moreover, redundancy analysis and variation partitioning analysis confirmed that SOCd decline in ant mounds was primarily attributed to reduced soil moisture and elevated microbial abundance. The conceptual model implied that ants could effectively strengthen SOC content heterogeneity at the microscales, characterized by lower SOC storage and stability, and higher CO2 emission than those in nearby soils.