Biogeochemical Cycling Of Nutrients Research Articles

Inter-basin water diversion homogenizes microbial communities mainly through stochastic assembly processes

Inter-basin water transfer is an effective manner to achieve the optimal allocation of water resources, while accompanied by some ecological effects. The responses of microorganisms to water diversion and the ecological processes in regulating the community assembly are still unclear. Taking the eastern route of South-to-North Water Diversion Project as the study area, we investigated the microbial community patterns and the underlying assemblage processes in habitats with different hydrological connectivity, including isolated lakes, connected lakes and man-made canal. The results showed that microbial communities in the canal had higher diversity, lower dissimilarity, weaker compositional variation, and stronger co-occurrence patterns compared with that in the connected and isolated lakes. These findings suggested that the increase of connectivity among natural aquatic habitats due to water diversion can homogenize microbial communities and reduce microbial heterogeneity. The neutral and null models demonstrated the importance of stochastic processes in shaping microbial community assembly. Dispersal limitation and variable selection were the predominant mechanisms structuring microbial communities in the isolated lakes. Due to the homogenized environmental condition and the enhanced hydrologic connectivity in the canal and the connected lakes, microbial communities had higher dispersal capability and ecological drift occurred more frequently in these lotic habitats. The variations in microbial community structure were mainly driven by biotic ecological succession than abiotic factors, with positive and negative cohesion explained 63% and 25% of variability, respectively. Six taxa were considered as the potential introduced microorganisms, which may favor the nutrient biogeochemical cycling and the organic matter degradation, but may also bring ecological risks. Overall, this study provides a deeper understanding of the ecological consequences of inter-basin water diversion, and helps the regulation and management of these projects.

Probing Molecular-Level Dynamic Interactions of Dissolved Organic Matter with Iron Oxyhydroxide via a Coupled Microfluidic Reactor and an Online High-Resolution Mass Spectrometry System.

The interactions between dissolved organic matter (DOM) and iron (Fe) oxyhydroxide are crucial in regulating the biogeochemical cycling of nutrients and elements, including the preservation of carbon in soils. The mechanisms of DOM molecular assembly on mineral surfaces have been extensively studied at the mesoscale with equilibrium experiments, yet the molecular-level evolution of the DOM-mineral interface under dynamic interaction conditions is not fully understood. Here, we designed a microfluidic reactor coupled with an online solid phase extraction (SPE)-LC-QTOF MS system to continually monitor the changes in DOM composition during flowing contact with Fe oxyhydroxide at circumneutral pH, which simulates soil minerals interacting with constant DOM input. Time-series UV-visible absorption spectra and mass spectrometry data showed that after aromatic DOM moieties were first preferentially sequestered by the pristine Fe oxyhydroxide surface, the adsorption of nonaromatic DOM molecules with greater hydrophobicity, lower acidity, and lower molecular weights (<400) from new DOM solutions was favored. This is accompanied by a transition from mineral surface chemistry-dominated adsorption to organic-organic interaction-dominated adsorption. These findings provide direct molecular-level evidence to the zonal model of DOM assembly on mineral surfaces by taking the dynamics of interfacial interactions into consideration. This study also shows that coupled microfluidics and online high-resolution mass spectrometry (HRMS) system is a promising experimental platform for probing microscale environmental carbon dynamics by integrating in situ reactions, sample pretreatment, and automatic analysis.

Changes in macrofauna bioturbation during repeated heatwaves mediate changes in biogeochemical cycling of nutrients

The increasing frequency and intensity of marine heatwaves (MHWs) observed worldwide entails changes in the structure and functioning of ecological communities. While severe and extreme heatwaves often have more destructive effects, the more subtle effects of moderate and strong heatwaves may nevertheless affect ecosystem functioning through complex, context-dependent linkages between different processes. Here we conducted a laboratory experiment to study the effects of repeated short-term, strong MHWs on macrofauna bioturbation and associated solute fluxes as a measure of ecosystem functioning using natural soft-sediment communities from the Baltic Sea. Our results showed changes in both bioturbation and biogeochemical cycling of nutrients following short-term, strong heatwaves, which seemed to contribute to an enhanced degradation of organic matter in the seafloor and an enhanced exchange of solutes across the sediment-water interface as well as increased sediment oxygen consumption. Following changes in these processes, the relative contribution of macrofauna and the environmental context to ecosystem functioning was altered. Our results highlight the potential of even shorter-term, strong MHWs of having system-wide impacts due to changes in the mechanistic process of bioturbation underpinning the biogeochemical cycling of nutrients. This study also highlights the need to measure a wide range of variables for a comprehensive understanding of the changes in functioning under disturbances, such as MHWs.

Elevated CO2 increases soil redox potential by promoting root radial oxygen loss in paddy field

Soil redox potential (Eh) plays an important role in the biogeochemical cycling of soil nutrients. Whereas its effect soil process and nutrients’ availability under elevated atmospheric CO2 concentration and warming has seldom been investigated. Thus, in this study, a field experiment was used to elucidate the effect of elevated CO2 concentration and warming on soil Eh, redox-sensitive elements and root radial oxygen loss (ROL). We hypothesized elevated CO2 and warming could alter soil Eh by promoting or inhibiting ROL. We found that soil Eh in the rhizosphere was significantly higher than that of non-rhizosphere. Elevated CO2 enhanced soil Eh by 11.5%, which corresponded to a significant decrease in soil Fe2+ and Mn2+concentration. Under elevated CO2, the concentration of Fe2+ and Mn2+ decreased by 14.7% and 13.7%, respectively. We also found that elevated CO2 altered rice root aerenchyma structure and promoted rice root ROL. Under elevated CO2, rice root ROL increased by 79.5% and 112.2% for Yangdao 6 and Changyou 5, respectively. Warming had no effect on soil Eh and rice root ROL. While warming increased the concentration of Mn2+ and SO42− by 4.9% and 19.3%, respectively. There was a significant interaction between elevated CO2 and warming on Fe2+ and Mn2+. Under elevated CO2, warming had no effect on the concentration of Fe2+ but decreased Mn2+ concentration significantly. Our study demonstrated that elevated atmospheric CO2 in the future could increase soil Eh by promoting rice root ROL, which will alter some soil nutrients’ availability, such as Fe2+ and Mn2+.

Фенольные соединения и лигнин в растениях еловых и сосновых лесов в условиях промышленного воздушного загрязнения

The changes in the content of phenolic compounds and lignin in the needles/leaves of six plant species growing in spruce and pine forests of the Kola Peninsula, including those exposed to industrial air pollution (Cu, Ni) of varying degrees of intensity, were established. The results obtained indicate that the reaction to industrial pollution largely depends on the type of plant and the place of growth. Some plant species adapt to increased anthropogenic loads by increasing concentrations of phenolic compoundsand lignin, while others, on the contrary, reduce these indicators. Such, changes in perennial needles/leaves of plants can lead to a change in the rate of decomposition of this litter, which can affect the functioning of the ecosystem (for example: slowing down the biogeochemical cycles of nutrients). Biochemical monitoring of Empetrum hermaphroditum looks very promising, because of its resistance to contamination and an unambiguous reaction to it in both spruce and pine forests.

A research agenda for nonvascular photoautotrophs under climate change.

Nonvascular photoautotrophs (NVP), including bryophytes, lichens, terrestrial algae, and cyanobacteria, are increasingly recognized as being essential to ecosystem functioning in many regions of the world. Current research suggests that climate change may pose a substantial threat to NVP, but the extent to which this will affect the associated ecosystem functions and services is highly uncertain. Here, we propose a research agenda to address this urgent question, focusing on physiological and ecological processes that link NVP to ecosystem functions while also taking into account the substantial taxonomic diversity across multiple ecosystem types. Accordingly, we developed a new categorization scheme, based on microclimatic gradients, which simplifies the high physiological and morphological diversity of NVP and world-wide distribution with respect to several broad habitat types. We found that habitat-specific ecosystem functions of NVP will likely be substantially affected by climate change, and more quantitative process understanding is required on (1) potential for acclimation, (2) response to elevated CO2 , (3) role of the microbiome, and (4) feedback to (micro)climate. We suggest an integrative approach of innovative, multimethod laboratory and field experiments and ecophysiological modelling, for which sustained scientific collaboration on NVP research will be essential.

River damming enhances ecological functional stability of planktonic microorganisms.

Planktonic microorganisms play an important role in maintaining the ecological functions in aquatic ecosystems, but how their structure and function interrelate and respond to environmental changes is still not very clear. Damming interrupts the river continuum and alters river nutrient biogeochemical cycling and biological succession. Considering that river damming decreases the irregular hydrological fluctuation, we hypothesized that it can enhance the ecological functional stability (EFS) of planktonic microorganisms. Therefore, the community composition of planktonic bacteria and archaea, functional genes related to carbon, nitrogen, sulfur, and phosphorus cycling, and relevant environmental factors of four cascade reservoirs in the Pearl River, Southern China, were investigated to understand the impact of damming on microbial community structure and function and verify the above hypothesis. Here, the ratio of function to taxa (F:T) based on Euclidean distance matrix analysis was first proposed to characterize the microbial EFS; the smaller the ratio, the more stable the ecological functions. The results showed that the reservoirs created by river damming had seasonal thermal and chemical stratifications with an increasing hydraulic retention time, which significantly changed the microbial structure and function. The river microbial F:T was significantly higher than that of the reservoirs, indicating that river damming enhances the EFS of the planktonic microorganisms. Structural equation modeling demonstrated that water temperature was an important factor influencing the relationship between the microbial structure and function and thus affected their EFS. In addition, reservoir hydraulic load was found a main factor regulating the seasonal difference in microbial EFS among the reservoirs. This study will help to deepen the understanding of the relationship between microbial structure and function and provide a theoretical basis of assessing the ecological function change after the construction of river damming.

Soil Nutrient Concentrations, Associations and Their Relationships with Canopy Tree Category and Size in the Southwestern China Tropical Rainforests

ABSTRACT Soil nutrients and their stoichiometry are important indicators of nutrient biogeochemical cycles and various ecological processes. Soil nutrients are heterogeneously distributed and can be influenced by plants through litterfall and root activity. To explore the associations between soil nutrients and relationships between soil nutrients and plant characteristics, we selected three canopy tree categories based on abundance as dominant, common, and rare, with different plant sizes based on DBH (diameter at breast height, cm) for each species from three 1 ha tropical forest sites (Bu-Beng, P55, and Na-Ban-He forests), and collected the topsoil (0–10 cm) for physiochemical analysis. The results showed that soil nutrient concentrations were significantly different among the three forest sites. For soil total C, N, and P associations, soil total C and N had significant associations at all three sites; however, the associations of soil total C-P and N-P varied among sites. The plant category had significant relationships with soil stoichiometry, whereas plant size had significant relationships with soil nutrient concentrations; these relationships varied among the three sites. The results indicate that soil nutrient heterogeneity is influenced by tree category and size. Future studies should include a larger sample size to further validate these results.

Plant growth-promoting rhizobacteria: a potential bio-asset for restoration of degraded soil and crop productivity with sustainable emerging techniques.

The rapid expansion of degraded soil puts pressure on agricultural crop yield while also increasing the likelihood of food scarcity in the near future at the global level. The degraded soil does not suit plants growth owing to the alteration in biogeochemical cycles of nutrients, soil microbial diversity, soil organic matter, and increasing concentration of heavy metals and organic chemicals. Therefore, it is imperative that a solution should be found for such emerging issues in order to establish a sustainable future. In this context, the importance of plant growth-promoting rhizobacteria (PGPR) for their ability to reduce plant stress has been recognized. A direct and indirect mechanism in plant growth promotion is facilitated by PGPR via phytostimulation, biofertilizers, and biocontrol activities. However, plant stress mediated by deteriorated soil at the field level is not entirely addressed by the implementation of PGPR at the field level. Thus, emerging methods such as CRISPR and nanotechnological approaches along with PGPR could manage degraded soil effectively. In the pursuit of the critical gaps in this respect, the present review discusses the recent advancement in PGPR action when used along with nanomaterials and CRISPR, impacting plant growth under degraded soil, thereby opening a new horizon for researchers in this field to mitigate the challenges of degraded soil.

The Ecological Differentiation of Particle-Attached and Free-Living Bacterial Communities in a Seasonal Flooding Lake-the Poyang Lake.

Particle-attached (PA) and free-living (FL) bacterial communities play essential roles in the biogeochemical cycling of essential nutrients in aquatic environments. However, little is known about the factors that drive the differentiation of bacterial lifestyles, especially in flooding lake systems. Here we assessed the compositional and functional similarities between the FL and PA bacterial fractions in a typical flooding lake-the Poyang Lake (PYL) of China. The results revealed that PA communities had significantly different compositions and functions from FL communities in every hydrological period, and the diversity of both PA and FL communities was affected mainly by the water regime rather than bacterial lifestyles. PA communities were more diverse and enriched with Proteobacteria and Bacteroidetes, while FL communities had more Actinobacteria. There was a higher abundance of photosynthetic and nitrogen-cycling bacterial groups in PA communities, but a higher abundance of members involved in hydrocarbon degradation, aromatic hydrocarbon degradation, and methylotrophy in FL communities. Water properties (e.g., temperature, pH, total phosphorus) significantly regulated the lifestyle variations of PA and FL bacteria in PYL. Collectively, our results have demonstrated a clear ecological differentiation of PA and FL bacterial communities in flooding lakes, suggesting that the connectivity between FL and PA bacterial fractions is water property-related rather than water regime-related.

Geobacter-associated prophages confer beneficial effect on dissimilatory reduction of Fe(III) oxides

The dissimilatory reduction of Fe(III) oxides driven by Fe(III)-reducing bacteria (FRB) is an important biogeochemical process that influences not only iron cycling but also the biogeochemical cycles of carbon, trace metals, nutrients and contaminants. Phages have central roles in modulating the population and activity of FRB, but the mechanism for phage-involved Fe(III) oxide reduction is still unclear. This work used a common FRB, Geobacter soli, to explore the roles and underlying mechanisms of FRB-harboring prophages in the dissimilatory reduction of Fe(III) oxides. Bioinformatic analysis predicted 185 phage-related genes in the G. soli genome, comprising functional prophages that were verified to be induced to form tailed phage particles. Ferrihydrite reduction was facilitated as prophage induction was stimulated and declined as prophage induction was inhibited, which indicated a positive role of G. soli-harboring prophages in Fe(III) oxide reduction. A comparison of gene expression and released phage particles in the cells grown with Fe(III)-citrate and ferrihydrite suggested that microbial ferrihydrite reduction would activate the SOS response and consequently induce the prophages to enter lytic cycles. The prophage-mediated lysis of the subpopulation resulted in an increased release of extracellular DNA and membrane vesicles that were conducive to Fe(III) oxide reduction, which might explain the positive role of prophages in ferrihydrite reduction. In summary, our results revealed the functional roles and underlying mechanisms of FRB-associated prophages in facilitating the dissimilatory reduction of Fe(III) oxides, which will advance our understanding of iron cycling in natural ecosystems.

Hitchhiking into the Deep: How Microplastic Particles are Exported through the Biological Carbon Pump in the North Atlantic Ocean.

Understanding residence times of plastic in the ocean is a major knowledge gap in plastic pollution studies. Observations report a large mismatch between plastic load estimates from worldwide production and disposal and actual plastics floating at the sea surface. Surveys of the water column, from the surface to the deep sea, are rare. Most recent work, therefore, addressed the "missing plastic" question using modeling or laboratory approaches proposing biofouling and degradation as the main removal processes in the ocean. Through organic matrices, plastic can affect the biogeochemical and microbial cycling of carbon and nutrients. For the first time, we provide in situ measured vertical fluxes of microplastics deploying drifting sediment traps in the North Atlantic Gyre from 50 m down to 600 m depth, showing that through biogenic polymers plastic can be embedded into rapidly sinking particles also known as marine snow. We furthermore show that the carbon contained in plastic can represent up to 3.8% of the total downward flux of particulate organic carbon. Our results shed light on important pathways regulating the transport of microplastics in marine systems and on potential interactions with the marine carbon cycle, suggesting microplastic removal through the "biological plastic pump".

The rhizosphere microbiome improves the adaptive capabilities of plants under high soil cadmium conditions.

Cadmium (Cd) contamination of agricultural soils poses a potential public health issue for humans. Phytoremediation-based accumulating plants are an effective and sustainable technology for Cadmium remediation of contaminated agricultural soil. The rhizosphere microbiome can promote the growth and Cadmium accumulation in hyperaccumulators, but its taxonomic and functional traits remain elusive. The present study used two ecotypes of Sedum alfredii, an accumulating ecotype (AE) and a non-accumulating ecotype (NAE), as model plants to investigate the rhizosphere microbiome assemblages and influence on plant growth under high cadmium conditions. Our results showed that distinct root microbiomes assembled in association with both ecotypes of S. alfredii and that the assemblages were based largely on the lifestyles of the two ecotypes. In addition, we demonstrated that the functions of the microbes inhabiting the rhizosphere soils were closely associated with root-microbe interactions in both ecotypes of S. alfredii. Importantly, our results also demonstrated that the rhizosphere microbiome assembled in the AE rhizosphere soils contributed to plant growth and cadmium uptake under high cadmium conditions through functions such as nitrogen fixation, phosphorus solubilization, indole acetic acid (IAA) synthesis, and siderophore metabolism. However, this phenomenon was not clearly observed in the NAE. Our results suggest that the rhizosphere microbiome plays important roles in biogeochemical nutrient and metal cycling that can contribute to host plant fitness.

The Use of Raw Poultry Waste as Soil Amendment Under Field Conditions Caused a Loss of Bacterial Genetic Diversity Together with an Increment of Eutrophic Risk and Phytotoxic Effects.

Poultry waste has been used as fertilizer to avoid soil degradation caused by the long-term application of chemical fertilizer. However, few studies have evaluated field conditions where livestock wastes have been used for extended periods of time. In this study, physicochemical parameters, metabarcoding of the 16S rRNA gene, and ecotoxicity indexes were used for the characterization of chicken manure and poultry litter to examine the effect of their application to agricultural soils for 10years. Poultry wastes showed high concentrations of nutrients and increased electrical conductivity leading to phytotoxic effects on seeds. The bacterial communities were dominated by typical members of the gastrointestinal tract, noting the presence of pathogenic bacteria. Soils subjected to poultry manure applications showed statistically higher values of total and extractable phosphorous, increasing the risk of eutrophication. Moreover, while the soil bacterial community remained dominated by the ones related to the biogeochemical cycles of nutrients and plant growth promotion, losses of alpha diversity were observed on treated soils. Altogether, our work would contribute to understand the effects of common local agricultural practices and support the adoption of the waste treatment process in compliance with environmental sustainability guidelines.

Microbial communities associated with epilithic algal matrix with different morphological characters in Luhuitou fringing reef

The microbiota is an important component of the epilithic algal matrix (EAM) and plays a central role in the biogeochemical cycling of important nutrients in coral reef ecosystems. Insufficient studies on EAM microbiota diversity have led to a limited understanding of the ecological functions of EAMs in different states. To explore the microbial community of EAMs in the Luhuitou fringing reef in Sanya, China, which has undergone the incessant expansion and domination of algae over the past several decades, investigations were conducted in the reef’s intertidal zone. Five types of substrate habitats (dead branching coral, dead massive coral, dead flat coral, granite block, and concrete block) were selected, and their microbial communities were analyzed by high-throughput sequencing of EAM holobionts using the 16S rDNA V4 region. Proteobacteria was the most abundant group, accounting for more than 70% of reads of the microbial composition across all sites, followed by Cyanobacteria (15.89%) and Bacteroidetes (5.93%), respectively. Cluster analysis divided all microbial communities into three groups, namely short, medium, and long EAMs. Algal length was the most important morphological factor impacting the differences in the composition of the EAM microbiota. The three EAM groups had 52 common OTUs and 78.52% common sequences, among which the most abundant were Vibrio spp. and Photobacterium spp. The three types of EAM also had unique OTUs. The short EAMs had 238 unique OTUs and 48.61% unique sequences, mainly in the genera Shewanella and Cyanobacterium. The medium EAMs contained 130 unique OTUs and 4.36% unique sequences, mainly in the genera Pseudomonas and Bacillus. The long EAMs only had 27 unique OTUs and 4.13% unique sequences, mainly in the genus Marinobacter. Compared with short EAM, medium and long EAM had a lower proportion of autotrophic bacteria and higher proportion of potential pathogenic bacteria. It is suggested that EAMs with different phenotypes have different microbial compositions, and the ecological function of the EAM microbiota changes from autotrophic to pathogenic with an increase in algal length. As EAMs have expanded on coastal coral reefs worldwide, it is essential to comprehensively explore the community structure and ecological role of their microbial communities.

Unravelling nutrient fate and CO2 concentrations in the reservoirs of the Seine Basin using a modelling approach

Reservoirs are active reactors for the biogeochemical cycling of carbon (C) and nutrients (nitrogen: N, phosphorus: P, and silica: Si), however, our in-depth understanding of C and nutrient cycling in reservoirs is still limited by the fact that it involves a variety of closely linked and coupled biogeochemical and hydrological processes. In this study, the updated process-based Barman model was applied to three reservoirs of the Seine Basin during 2019–2020, considering the variations of carbon dioxide (CO2) concentrations and key water quality variables. The model simulations captured well the observed seasonal variations of water quality variables, although discrepancies remained for some variables. According to the model, we found that: (1) the three reservoirs are autotrophic ecosystems and showed high removal efficiency of dissolved inorganic carbon and nutrients during 2019-2020; (2) phytoplankton assimilation, benthic denitrification, precipitation and dissolution of calcium carbonate, and gas exchange at the water-air interface are the dominant processes for water quality variations in reservoirs; (3) based on scenarios results, trophic state and mean water depth of reservoir would impact the biogeochemical processes and the retention efficiency of nitrate and dissolved silicate. Finally, we expect that the successful application of Barman model in the reservoirs of the Seine Basin could provide a useful tool for simulating reservoir water quality changes and thus evaluating the impacts of reservoirs on downstream water quality.

Intensity and duration of exposure determine prokaryotic community response to salinization in freshwater wetland soils

The salinization of coastal freshwater wetlands may impact the biogeochemical cycling of critical nutrients by altering soil microbial community structure and function. Nitrate (NO3–) reduction pathways appear particularly sensitive, though the interactive effects of salinization intensity and duration of exposure remain unclear. To address this knowledge gap, we performed a transplant experiment that exposed soil from a freshwater (≤0.1 ppt) wetland to oligohaline (1 ppt) and mesohaline (14 ppt) conditions for two years. In transplanted soils, we found physicochemical changes characteristic of salinization events, including elevated porewater concentrations of ammonium and sulfate and decreased soil organic matter and redox potential. Amplicon sequencing (16S rRNA) revealed that mesohaline levels of salinization caused rapid community restructuring; distinct transition communities were evident by the first sampling event (5 months) and persisted for ∼2 years (19–22 months). In contrast, freshwater communities transplanted to oligohaline conditions were highly resistant to restructuring, and it took nearly 2 years of salinization for differences to manifest. For both transplants, community shifts included changes in the distribution and abundance of taxa capable of NO3– reduction, including several groups also known for sulfur redox metabolism. Nitrate (15NO3-) reduction assays were performed to determine how rates were affected. Dissimilatory nitrate reduction to ammonium (DNRA) increased for all sampling events, but only under mesohaline conditions, whereas denitrification responses depended more on the duration of exposure than salinity level. These findings may be useful for determining when and how the ability of wetlands to remove nitrogen will be impacted by sea-level rise. Further, these results suggest that efforts to synthesize and generalize prior research regarding salinization effects on wetland microbial community structure and function must explicitly consider both salinity intensity and exposure length.

Sediment phosphorus speciation changes by extracellular enzymatic activity (EEA) of three phosphatase pH-dependent isoforms

Salt marshes are key ecosystems for biogeochemical cycling of nutrients in coastal areas, providing essential sequestration of contaminants and elemental organic forms while recycling these last to more bioavailable forms. Extracellular phosphatase-mediated phosphorus biogeochemical cycling acquires this way a reinforced role. In terms of speciation, salt marsh sediments exhibited a large pool of P in a bioavailable form (> 60%), being this pool characterized by being readily accessible to plants by weak chemical reactions. Regarding phosphatase activity, the acid isoform was found to be the most abundant pH-isoform present in salt marsh rhizosediments. A positive correlation could be found between humic acid bound P and total and acid phosphatase activities, possibly driven by the action of acid phosphatase on the acidic molecules of humic acids, using organic P as substrate, and releasing inorganic P into the desorbable P-pool. This process is more evident during the cold seasons, where the largest necromass input is observed entering the sediments, due to seasonal plant senescence. It could also be observed a positive correlation between inorganic phosphorus forms and phosphatase activity, consistent with phosphatases-driven inorganic phosphorus production from the recycling of organic forms, and thus a possible direct effect of phosphatase, as it was described for other ecosystems. This biogeochemical cycling is key for the ecosystem nutrient recycling, while passive remediator of eutrophication, but also for maintaining the salt marsh areas high primary productivity and their role as habitat, shelter and feeding ground of many animal species.

An Assessment of Biodiversity in Tabuk Region of Saudi Arabia: A Comprehensive Review

Biodiversity refers to all the type of species in one geographical region or ecosystem. It consists of plants, animals, bacteria, and other life forms. As an estimate, around 1.7 million species are on record globally and approximately 15,000–18,000 new species are added each year. Global climate change is accelerating species extinction due to habitat destruction. Further, various abiotic and biotic environmental factors are limiting the pattern of biodiversity in a geographical region. A change in species category from endangered to extinction occurs due to their physiological, morphological, and life history pattern, which limits them to a specific niche. Biodiversity is very important for energy production and flow, bioremediation, and biogeochemical cycling of nutrients in terrestrial to aquatic ecosystems and vice versa. It is further required for human existence in the form of food, fibers, medicines, and biological control. Therefore, consistent monitoring, assessment, and conservation of ecological habitats and diversity of flora and fauna of aquatic and terrestrial ecosystems is the need of the hour. In this article, we are presenting an assessment based upon the literature survey on the biodiversity of Tabuk region of Kingdom of Saudi Arabia. A comprehensive study on the biodiversity of plants, animals and microorganisms of the Tabuk region (Tabuk city, Tayma, Haql, Sharma, Duba, Al Wajh and Umluj, Al Zetah, Al Beda’a, etc.) are included in this review. This study will be a landmark as it is conducted at the inception of NEOM project in Tabuk region. It will help the authorities to enhance the native green cover, decrease desertification, regenerate biodiversity in natural environments, and advance the quality of life, to achieve the objectives of the Saudi Green Initiative and VISION 2030. However, studies and investigations on Tabuk biodiversity are still limited and need further exploration. Recently, a joint work between King Salman Royal Natural Reserve (KSRNR) and Department of Biology of University of Tabuk is underway to monitor the baseline data of flora and fauna of this region.

Recycling of Leaf Litters: Biowaste Management for Resource Conservation

The search for viable agricultural production systems in the era of unpredictable climate events has elevated the prospects of agroforestry practices for resilience and sustainability. The litter biomass in these ecosystems govern the biogeochemical nutrient cycling prevalent, but can also serve as organic inputs in crop production under situations where these are considered as menace and cumbersome to dispose. When left to decay under natural conditions litter takes a considerably long time for decomposition and release of nutrients entrapped in them. With the increasing need to conserve natural resources and energy, recycling of organic wastes assumes major significance. Leaf litters are untapped sources of nutrients and are generated in substantial quantities in most of the agroforestrty systems. Among the different alternatives available for recycling biomass residues, composting is considered most efficient and viable option, but recent innovations such as biochar production and thermochemical digestion have also been attempted. Organic farming strategies call for in situ production of nutrient inputs for economic viability of the practice and hence information on alternative technologies to enrich the repository of organic manures in the form of litter compost will be of immense importance. These composts could be recycled to soil for enriching soil organic carbon, plant nutrients and to sustain soil health in the long run. Proper utilization of the biowastes in the tree based systems will also ensure reduction in environmental pollution and forest fire incidents that otherwise threaten life. The review unveils the possible technologies for recycling the litter and use as a nutrient source but emphasizes the need for a suitable environment favouring the rapid decomposition.