Abiotic Research Articles

Gene expression changes in Maconellicoccus hirsutus in response to sublethal dose of Buprofezin

The pink or hibiscus mealybug, Maconellicoccus hirsutus, is a serious pest of grapes, jute, and mesta, causing severe yield losses in India and other countries. Chemical control remains the foremost choice for farmers to manage this pest. As insecticides break down over time due to biotic and abiotic factors, insects are exposed to varying levels of these exogenous compounds. Several studies have reported that sublethal doses affect insect physiology, but only a few have examined the changes in gene expression at the molecular level. Therefore, studies were conducted to elucidate the molecular mechanisms in M. hirsutus exposed to sublethal doses of buprofezin 25 SC. Life table analysis revealed increased fecundity in M. hirsutus exposed to the sublethal dose. A total of 1,744 differentially expressed genes were identified between the buprofezin-treated and untreated samples using transcriptome analysis. These genes were primarily associated with ribosomal proteins, proteases, cuticular proteins, and cytoskeletal structures. Ribosomes and phagosomes were the most highly enriched pathways. Interestingly, most of the DEGs were involved in restoring homeostasis rather than detoxification. To validate our RNA-sequencing results, qRT-PCR validation was performed on ten randomly selected genes. Overall, our findings provide valuable insights into intermittent changes in stress-coping genes, apart from detoxification genes.

Understanding the effects of livestock grazing on dryland plant communities within the context of abiotic variability

AbstractDrylands, which cover more than 40% of the Earth's terrestrial surface, face rising agricultural demand and the influence of climate change. Understanding how livestock grazing pressure and local climate affect these environments is pivotal for informed land management. We studied big sagebrush plant communities in southwestern Wyoming over grazing gradients created by artificial livestock watering points. To explore the role of abiotic factors in shaping plant community response to grazing, we assessed the response of plant functional groups to grazing while accounting for soil texture variability across a precipitation gradient. Our models estimated that sagebrush cover responded positively to grazing intensity, with a 6% increase in cover with intensity when comparing the heaviest grazing treatment with the lowest grazing intensity. Perennial bunchgrass cover, the primary forage component, had a small negative response, a 3% decrease in cover from the lowest grazing intensity to the highest. Grazing intensity had no effect on bunchgrass density, perennial forbs, or rhizomatous grasses. Compared with abiotic factors, grazing intensity had a small effect on perennial bunchgrass and bare ground. We found that precipitation explained a 13% increase in perennial bunchgrass cover and a 34% decrease in bare ground cover compared with a 6% increase with increasing intensity across our grazing gradients. Sand content also had a larger effect on perennial bunchgrass cover and density than grazing. Increased sand content was associated with increased bunchgrass cover and density, supporting the inverse texture hypothesis. Our results show that while livestock grazing impacts sagebrush plant communities, its effect is small when compared with the effects of climate and soil. Our study contributes to a growing body of research emphasizing the need to contextualize plant community responses to grazing within specific climatic and edaphic conditions, which will promote effective land management in dryland ecosystems.

Spatial Distribution Pattern of Aromia bungii Within China and Its Potential Distribution Under Climate Change and Human Activity.

Aromia bungii is a pest that interferes with the health of forests and hinders the development of the fruit tree industry, and its spread is influenced by changes in abiotic factors and human activities. Therefore, exploring their spatial distribution patterns and potential distribution areas under such conditions is crucial for maintaining forest ecosystem security. This study analyzed the spatial differentiation characteristics of the geographic distribution pattern of A. bungii in China using Moran's I and the Getis-Ord General G index. Hot spot distribution areas were identified using Getis-Ord Gi*. An optimized MaxEnt model was used to predict the potential distribution areas of A. bungii within China under four shared economic pathways by combining multivariate environmental data: (1) prediction of natural environmental variables predicted under current climate models; (2) prediction of natural environmental variables + human activities under current climate models; and (3) prediction of natural environmental variables under the future climate models (2050s and 2070s). Meanwhile, MigClim was used to simulate the unoccupied suitable area in the presence of obstacles under future climate change. The results showed that human activities, minimum temperature of the coldest month, and precipitation of the wettest month had positive effects on the distribution of A. bungii. However, in the current period, human activities drastically reduced the survival area of A. bungii, and its suitable distribution area was mainly concentrated in the eastern and central regions of China. Under the influence of climate change in the future, the habitat of A. bungii will gradually increase. Additionally, the MigClim model indicates that the area unoccupied by A. bungii has been on a continuous increasing trend. This study provides a positive reference for the prevention and control of A. bungii and the maintenance of forest health and ecosystem security, and provides important theoretical guidance for researchers, policymakers, and governments.

Biotic factors as key determinants for ovarian and oothecal developmental plasticity of a tortoise beetle

Ovarian development in r-selected species is a highly dynamic process widely studied in various insect groups. An array of biotic and abiotic factors may influence it. So, the present investigation was to evaluate the impact of a female's age and mating status on the ovarian development, ootheca formation, body colour polymorphism, and fat content of the tortoise beetle, Aspidomorpha miliaris (Fabricius). Females of a certain age and mating status were dissected to demonstrate changes in their ovarioles, lateral oviduct, accessory gland, elytral colour, fat body content, and body size. It was predicted that age or mating status would not affect the ovarian parameters like length and width of ovarioles, lateral oviducts, accessory glands, body size, fat body content, and elytral colour. However, the ootheca-forming modifications would be initiated by ageing and mating. The current study demonstrated the substantial effect of age and mating status on the growth of the accessory glands and ovarioles. On the other hand, fat body contents declined comparatively in multiply-mated females. Besides this, the beetle exhibits elytral colour polymorphism till sexual maturity. An accessory gland was exclusively detected in multiply-mated females. This discovery opens opportunities for further investigation into the precise function of the gland, which is likely involved in the formation of ootheca.

ОЦЕНКА ВИДОВОГО РАЗНООБРАЗИЯ ТЛЕЙ (HEMIPTERA, APHIDIDAE) В АГРОЦЕНОЗЕ ОПЫТНОГО ПОЛЯ ВИЗР ПУШКИНСКОГО РАЙОНА САНКТ-ПЕТЕРБУРГА В 2021–2023 гг.

The research was carried out in order to analyze changes in species diversity and the dynamics of aphid abundance within the same agrocenosis under different weather conditions. The species composition and abundance of aphids were monitored using the Malaise trap at the VIZR experimental field (Pushkinsky district of St. Petersburg) during the growing season 2021-2023. During this period, 34 species of phytophages were identified, of which 20 are pests of crops, including 9 species in 2021, 11 species in 2022 and 27 species in 2023. The smallest number of individuals in the trap was observed in 2021 (36 pcs.), in 2022 and 2023 it was about the same (97 and 101 pcs., respectively). The largest number of insect species and individuals in one trap was identified in 2023, which was the result of a favorable interaction of abiotic and biotic factors. In 2021, the traps were dominated by dendrophilous aphids, among which the largest was the European birch aphid.

Morphological complexity promotes origination and extinction rates in ammonoids.

The causes of heterogeneity in evolutionary rates are a key question in macroevolution. Origination and extinction rates are closely related to abiotic factors, such as climate1,2 and geography,3,4 as well as biotic factors such as taxonomic richness5,6 and morphology,7 which are influenced by phylogeny.8,9 Studies on the relationship between morphology and macroevolution have focused on morphological traits, including body size,6,7,9 shape,10 color,11,12 and complexity,13,14,15 and have proposed biological laws, such as the zero-force evolutionary law16 and Cope's rule.17 However, the relationship between morphological complexity and turnover rates remains poorly defined because of the lack of suitable measures for various subjects.18,19 Here, we establish a quantitative method, the two-dimensional ornamentation index (2D-OI), which allows the description of the ornamental complexity of ammonoids. Ammonoids are one of the most abundant and well-studied fossil groups, with complex conch structures.20 Ammonoids display some similarities with trilobites and mammals21,22 in terms of their high evolutionary rates; however, the underlying mechanisms remain elusive. Moreover, ammonoids exhibit marked heterogeneity in turnover rates across spatiotemporal scales23 and clades,23,24 making them key clades for investigating the relationship between turnover rates and morphological complexity. The results show that morphologically complex genera and species often have higher origination and extinction rates than morphologically simple taxa. Diversity fluctuations of taxa with complex ornamentation generally overimprint and control the overall net diversification rates of ammonoids. This double-edged sword of rapid evolution and increased extinction risk driven by complex morphologies has significant implications for our understanding of how species survive over geological timescales.

Plio/Pleistocene-induced climatic oscillations drive cladogenesis in a high-altitude freshwater crab, Potamonautes mariepskoppie (Decapoda: Potamonautidae), in South Africa

Abstract In this study, we explored the phylogeographical history of the mountain-dwelling freshwater crab Potamonautes mariepskoppie to understand evolutionary processes and identify possible hidden lineages. DNA sequence data from mitochondrial loci (COI, 12S rRNA, and 16S rRNA) and a nuclear locus (histone 3) were analysed using both maximum likelihood and Bayesian inference. Species delimitation was tested with four methods: ASAP, bPTP, bGMYC, and STACEY. Divergence time estimation and ecological niche modelling with ENMEval and Maxent were used to study species distribution and elucidate abiotic factors affecting evolution. Phylogenetic analyses showed three distinct clades, corresponding to geographical regions: Limpopo, Mpumalanga, and Mount Sheba. These clades had no shared haplotypes and exhibited moderate genetic differentiation. Divergence time estimates indicated that these clades diverged during the Plio/Pleistocene, a period of significant climatic shifts in southern Africa. All four species delimitation methods consistently supported the recognition of these clades as distinct species; however, discriminant function analyses of carapace characteristics showed significant overlap between the three clades. Ecological niche modelling indicated that rainfall is a key factor in the species distribution. The present study highlights the need for further investigation of the high-elevation plateaus throughout Limpopo and Mpumalanga, because fine-scale sampling might unmask considerable hitherto-undocumented biodiversity.

Elevational patterns of species richness and phylogenetic diversity in a Mediterranean island

Understanding the abiotic factors influencing biodiversity patterns on Earth is a crucial task for conservation scientists. At the regional level, meso-climate factors, primarily associated with elevational gradients, are of great importance. However, disentangling these factors can be challenging due to the influence of other variables, such as geological substrata. To address this issue and better understand elevational gradients, it is essential to study geologically homogeneous terrains, particularly in Mediterranean islands where such research is lacking. In this study, we investigated the distribution of plant species richness along the elevational gradient of the Limbara massif, which consists predominantly of granite rocks and ranks as the third-highest peak in Sardinia at 1,359 meters a.s.l. We employed generalized linear models to analyze richness patterns, considering various factors, including all plant species, functional species groups categorized by Raunkiær life forms, chorological groups of species, alien species and phylogenetic diversity. Our findings revealed a hump-shaped model of species richness along the elevational gradient, with lower elevations exhibiting the highest species richness. Additionally, endemic species richness increased with higher elevations, while alien species were predominantly found at lower elevations. These results indicate that the Limbara massif possesses a significant elevational gradient in species composition, likely reflecting a unique plant evolutionary history. Furthermore, we emphasize the importance of published floras as valuable sources of biodiversity data for such studies.

Joint Influence of Forest Strata Attributes and Abiotic Factors on Herbaceous Plant Abundance in South Korean Forest Restoration Sites: Native Versus Alien Species

The success of ecosystem restoration is often evaluated by the stable establishment and growth of native plants while preventing the spread of alien plants. However, research on the factors and mechanisms controlling the abundance (richness and coverage) of native and alien plants remains limited. To address this, we analyzed data from 167 plots (100 m2) in forest restoration sites in South Korea. We assessed the effects of abiotic factors (topography, climate, and soil), biotic factors, and the number of years integrally since restoration on both plant groups by using a piecewise structural equation model. Native plant abundance was influenced by shrub density (species richness: β = 0.19; coverage: β = 0.20) and available phosphorus (β = 0.19), while alien plant abundance was controlled by soil pH (species richness: β = 0.45), elevation (β = −0.15), species richness, and tree (β = −0.15) and shrub species richness (β = −0.16). The number of years since restoration has indirectly affected native and alien plants through shrub species richness and shrub coverage. Our results indicate that high resource availability, such as light, in the early stages of restoration may allow native and alien herbaceous plants to coexist. However, as vegetation and forest strata develop, reduced light availability can lead to a decline in alien species and the dominance of native plants. We also provide management strategies to suppress alien plants by promoting structural complexity within forest stands.

Potential of Binahong Leaves (Anredera cordifolia Ten.) and Shallot Skin (Allium cepa L.) Extract as Biopesticides for Biological Control of Rice Bug (Leptocorisa oratorius F.)

The rice bug is a pest causing decrease rice production. Meanwhile, binahong leaves and shallot skin contain potential materials for making biopesticides. This research aimed to analyze potential of binahong leaves and shallot skin extract as biopesticides and toxicity tested against rice bug. The research was carried out using Completely Randomized Design, biopesticides were made in various concentrations, 0% as a control; 10; 20; 30; 40; and 50. The extract was calculated for yield, pH, and phytochemical screening. Then, biopesticide sprayed on the pests at 24, 48, 72, 96, 120, 144, and 168 hours to observe mortality, LC50, morphology, behavior, biotic, and data analysis using ANOVA followed 0.05 Tukey test. The results showed the extract has potential as a biopesticide with yield value 8,3 – 12; pH value 4,84 – 5,37; and positive secondary metabolite. Meanwhile, toxicity tests showed the highest mortality at concentration 50%, LC50 at 144th hours and 168th hours was 4,373 and 2,002. Besides that, biopesticides changes morphology and behavior pest. Observations abiotic factors showed that rice bug can survive in temperature range of 22,75 – 25oC and relative humidity of 77 - 84%. In the future, it hoped biopesticides can be commercialized to reduce dependence on chemical pesticides.

C:N stoichiometry and the fate of organic carbon in ecosystems of the northwest Pacific Ocean

Phytoplankton elemental composition regulates the efficiency of energy and material transfer in the interface between phytoplankton and their consumers. The ratio of particulate organic carbon to particulate organic nitrogen (POC:PON) shows considerable regional deviations from the canonical Redfield ratio in the global surface ocean. However, in certain oceanic regions such as the northwest Pacific Ocean (NWPO) POC:PON distribution and its ecological significance remain uncertain. We investigated surface ocean POC:PON distributions at 66 stations in the NWPO, and quantified the correlations between POC:PON and multiple biotic and abiotic factors including sea surface temperature (SST), nutrient concentrations and multiple lipid biomarkers (fatty acids and sterols), by combining correlation analyses and generalized additive models. POC:PON (range: 3.53–14.18 M ratios; median: 6.89) was overall higher in the (sub)tropical biome than that in the high-latitude biome. In the entire study region, SST, nutrient concentration and lipid-derived phytoplankton community structure explained 41 %, 33 % and 26 % of the variance in POC:PON, respectively, while the respective importance of each factor differed between the (sub)tropical and high-latitude biomes. Furthermore, we calculated the percentage of primary production consumed by herbivores (PPC; 54–156 %), showing a higher mean value (117 %) in the high-latitude biome and a lower one (92 %) in the (sub)tropical biome. The spatial distribution pattern of PPC can be attributed to multiple factors, with PPC correlating negatively with SST and positively with lipid-based indicators of phytoplankton food quality and POC concentrations. The increase in SST may be associated with a reduced nitrogen content, resulting in lower PPC in the (sub)tropical biome. This study highlights the significance of SST and elemental and biochemical composition of phytoplankton in regulating the transfer of organic carbon to herbivores in the NWPO.

Decline of soil volatile organic compounds from a Mediterranean deciduous forest under a future drier climate

Biogenic volatile organic compounds (BVOCs) are crucial for ecosystem functioning, atmospheric chemistry and climate. While modulation of BVOC emissions from living vegetation with biotic and abiotic factors is well documented, how these factors drive soil BVOC emissions remain less understood, particularly in Mediterranean forests. To fill this gap, this pioneer study investigates whether BVOC fluxes from natural soil covered by litter (referred to as forest soil) vary under natural and amplified long-term water stress (35% annual rain exclusion over the past 10 years) in a deciduous oak Mediterranean forest (Quercus pubescens Willd.) compared to natural climate conditions. This aim has only been tackled in a single evergreen Mediterranean forest so far. Using proton transfer reaction time of flight mass spectrometer (PTR-ToF-MS) we also provide, for the first time, a detailed diurnal cycle of soil BVOCs in relation to air temperature, air humidity, and biotic factors including soil respiration and litter content in lignin, cellulose and hemicellulose. The main results revealed that forest soil represents a source of most BVOCs (e.g., acetaldehyde, acetone, acrolein, hexanol, monoterpenes) with maximum values at mid-day (42 μgC.m−2. h−1) in response to higher temperatures while it acts as a clear sink of isoprene. Total soil BVOC emission rates, together with soil respiration, decreased by 43% after a decade of partial rain restriction. These results will contribute to enhance further modeling of soil BVOC emissions under various climate scenarios both at regional and global scales.

Seroprevalence of Erysipelothrix rhusiopathiae in Beaufort Sea Polar Bears (Ursus maritimus) is Linked to Ringed Seal (Pusa hispida) Demographics.

Polar bear (Ursus maritimus) life history is intimately associated with the distribution of sea ice and their prey in Arctic ecosystems. These ecosystems are changing in response to climate warming, resulting in the increased prevalence of pathogens in polar bears. Erysipelothrix rhusiopathiae has a long history of infection in domestic species and more recently in wildlife in the Canadian Arctic. As a result of increasing reports of E. rhusiopathiae causing morbidity and mortality in Arctic terrestrial mammals, we tested the seroprevalence of E. rhusiopathiae in Beaufort Sea polar bears sampled in 1985-87, 1992, 1994, and 2003-11. Our sample of 180 polar bears (117 females, 61 males, two unknown) with a median age of 9 yr (range 1-26 yr) had a seropositivity of 27.2% (49/180 individuals). We used binomial logistic regressions to investigate biotic and abiotic factors that may be linked to seropositivity. The resulting top model found that increased predation on adult ringed seals (Pusa [Phoca] hispida) and negative winter Arctic Oscillation Index (AOI) years were associated with a higher probability of seropositivity. Ringed seals may be a reservoir for E. rhusiopathiae via their consumption of infected prey, as the pathogen can persist in marine fish, molluscs, and crustaceans. Negative winter AOIs in our data set reflected high ice volume years, which reduced ringed seal natality, resulting in fewer seal pups available as prey. Our results suggest that exposure to E. rhusiopathiae in Beaufort Sea polar bears is modulated by a predator-prey mechanism.

Fine-scale habitat selection in tree-dwelling spiders: an experimental approach.

Habitat selection by spiders is strongly influenced by biotic factors such as the availability and diversity of prey and abiotic factors such as temperature, humidity, and the structural complexity of the habitat. Structural complexity is an aspect that intensely affects species persistence, population stability, and the coexistence of interacting species. Trees comprise a complex set of microhabitats due to their large biomass and heterogeneity of the architectural components of their trunk surface and branches. Spider species that live on trunks have diversified physiological or morphological adaptations that confer advantages in this environment. In this study, we experimentally examined the habitat choice by the tree-dwelling spiders Selenops cocheleti (Selenopidae), Corinna rubripes (Corinnidae), and Loxosceles gaucho (Sicariidae). We found that microhabitat specialization was restricted to trunk architectural characteristics rather than plant taxonomy. Selenops cocheleti and C. rubripes significantly preferred loose barks and holes in the trunks, respectively, showing that both spider species can evaluate the physical structure of the microhabitat on a fine scale. On the other hand, L. gaucho selected crevices and holes near the base of the trunk without giving much importance to the physical characteristics of the microhabitat per se (e.g., depth, height, length). Our findings indicate that for generalist predators like spiders, coexistence relies heavily on spatial segregation driven by distinct habitat preferences, irrespective of their method for capturing prey.

The swash zone selects functionally specialized assemblages of beach interstitial meiofauna (Platyhelminthes, Proseriata)

Life is not a beach for those animals that survive in the rough ecological conditions found in marine sandy beaches – and yet, microscopic animals thrive on them. We explore the drivers for meiofaunal diversity in beaches by analysing taxonomic and functional patterns of 348 flatworm communities across 116 reflective beaches in the western Mediterranean, totalling 152 species (61.2% new to science). First, we confirm that species richness does not differ between beach hydrodynamic levels (swash, shoaling and surf) but rather depends on the characteristics of each beach. Second, we demonstrate that species composition across those levels depends on the species traits, in addition to geographical and abiotic factors. Third, we highlight that the species functional space has a lower richness than expected and a lower redundancy in the wave‐exposed swash level compared to the shoaling and subtidal levels, suggesting a trait‐based ecological filtering. Finally, we show that those differences depend on the higher frequency of hydrodynamics‐related traits in the species of the swash level. Our results suggest that the rough hydrodynamic conditions in the swash level favour a unique combination of species traits, which might be linked to ecological speciation in flatworms but also in other interstitial animals.

Metabolomic Analysis of Elymus sibiricus Exposed to UV-B Radiation Stress.

Plants cultivated on the Qinghai-Tibet Plateau (QTP) are exposed to high ultraviolet radiation intensities, so they require effective mechanisms to adapt to these stress conditions. UV-B radiation is an abiotic stress factor that affects plant growth, development, and environmental adaptation. Elymus sibiricus is a common species in the alpine meadows of the QTP, with high-stress resistance, large biomass, and high nutritional value. This species plays an important role in establishing artificial grasslands and improving degraded grasslands. In this study, UV-B radiation-tolerant and UV-B radiation-sensitive E. sibiricus genotypes were subjected to simulated short-term (5 days, 10 days) and long-term (15 days, 20 days) UV-B radiation stress and the metabolite profiles evaluated to explore the mechanism underlying UV-B radiation resistance in E. sibiricus. A total of 699 metabolites were identified, including 11 primary metabolites such as lipids and lipid-like molecules, phenylpropanoids and polyketides, organic acids and their derivatives, and organic oxygen compounds. Principal component analysis distinctly clustered the samples according to the cultivar, indicating that the two genotypes exhibit distinct response mechanisms to UV-B radiation stress. The results showed that 14 metabolites, including linoleic acid, LPC 18:2, xanthosine, and 23 metabolites, including 2-one heptamethoxyflavone, glycyrrhizin, and caffeic acid were differentially expressed under short-term and long-term UV-B radiation stress, respectively. Therefore, these compounds are potential biomarkers for evaluating E. sibiricus response to UV-B radiation stress. Allantoin specific and consistent expression was up-regulated in the UV-B radiation-tolerant genotype, thereby it can be used to identify varieties resistant to UV-B radiation. Different metabolic profiles and UV-B radiation response mechanisms were observed between the UV-B radiation-tolerant and UV-B radiation-sensitive E. sibiricus genotypes. A model for the metabolic pathways and metabolic profiles was constructed for the two genotypes. This metabolomic study on the E. sibiricus response to UV-B radiation stress provides a reference for the breeding of new UV-B radiation-tolerant E. sibiricus cultivars.

Assessment of Bleaching Stress Vulnerability of Lakshadweep Islands using Google Earth Engine (GEE)

Coral reefs, among the Earth’s most diverse and valuable ecosystems, face unprecedented challenges due to climate change. Coral bleaching is a phenomenon wherein corals lose their symbiotic zooxanthellae owing to various stressors, leading to a whitening effect of the coral tissues. In recent decades, climate change has intensified coral bleaching events. Multiple stressors, including elevated Sea Surface Temperature (SST), extreme irradiance levels, and various biotic and abiotic factors trigger bleaching events. Coral bleaching is primarily driven by thermal stress caused by elevated SSTs. Climate change has worsened bleaching’s frequency and intensity. Global bleaching events are often linked to planetary ocean-atmospheric circulation processes such as El Niño Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD). This study focused on assessing the vulnerability of coral reefs in the Lakshadweep region of India from 2016 to 2023 using National Oceanic and Atmospheric Administration’s Climate Data Record Optimum Interpolation Sea Surface Temperature (NOAA CDR OISST) daily data. GOOGLE EARTH ENGINE (GEE) is a cloud computing platform which is used to collect and generate the base data for this study. The vulnerability assessment utilized two bleaching indices: SST anomaly and Degree Heating Week (DHW). Analysis of DHW data reveals that 2020 experienced the highest SST anomaly residence time due to IOD event of 2019, as compared to 2016 and 2023 which are known El Niño years. All Lakshadweep islands exhibited vulnerability, although in varying degrees across different areas. Based on the magnitude, intensity, and frequency of bleaching stress, the islands are categorized into different categories of vulnerability. This study identifies Baliyapaniyam, Cheriyam-Kalpeni and Suhelipar reefs as very highly vulnerable reefs in Lakshadweep. This study highlights the urgent need for monitoring and management measures to mitigate the impacts of climate change on coral reef ecosystems using spatial vulnerability patterns.

Estimation of Malondialdehyde Content in Medicago truncatula under Salt Stress Based on Multi-Order Spectral Transformation Characteristics

Salt stress is a significant abiotic factor affecting the growth and development of alfalfa. Malondialdehyde (MDA) serves as a critical biomarker for assessing alfalfa’s salt tolerance. Traditional methods for measuring MDA are often time-consuming and labor-intensive. Recent advances in remote sensing technology have made non-destructive estimation of metabolites feasible, positioning the accurate estimation of MDA content in alfalfa as a key focus in intelligent breeding. To address the challenge of detecting subtle changes in MDA content, this study developed a partial least squares regression (PLSR) model specifically for Medicago truncatula. This study utilized leaf reflectance hyperspectral data across the visible near-infrared–shortwave infrared (VIR-NIR-SWIR) spectrum, applying multi-order spectral transformation methods, including continuous wavelet transform (CWT), fractional differential (FD), and multi-granularity spectral segmentation (MGSS). Feature selection techniques, such as sequential forward selection (SFS), Least-Squares Boosting (LSBoost), and feature selection using neighborhood component analysis for regression (FSRNCA), were employed to enhance the efficiency of the MDA estimation. The findings revealed that the optimal PLSR model for MDA estimation was achieved by integrating CWT features across orders 1–30 with the SFS method. This model demonstrated robust estimation capabilities under varying salt stress conditions, significantly outperforming the original spectral data (R2 = 0.654, RMSE = 22.567 vs. R2 = 0.242, RMSE = 33.411). A comparative analysis of feature selection methods confirmed that SFS was the most effective for estimating MDA content in alfalfa. These results provide valuable insights and methodologies for MDA estimation and evaluating salt tolerance in alfalfa.

Pollution and the abundance of plankton in Rangkui River in Bangka Island

Land use and activity around the Rangkui Watershed affect water quality, and plankton have been studied to help manage the river's water quality. In the 2017 dry season, six station points representing land use functions from upstream to downstream were studied. Surface water sampling was carried out during the day with three replicates. Pollution around the Rangkui Watershed affected plankton abundance. Based on saprobity and physicochemical readings, the pollution level ranged from light upstream to heavy downstream. This study found 15 species from 15 families from six phytoplankton classes, that is, Bacillariophyceae, Chlorophyceae, Euglenophyceae, Cyanophyceae, Cryptophyceae, Dinophyceae, and 2 species of zooplankton Eurotatoria, and Branchiopoda. The highest total abundance of phytoplankton and zooplankton was observed upstream of Station 1 (721 ind/L) and gradually decreased downstream, with the exception of the absence of plankton at Station 3. Nitrate had a positive correlation with phytoplankton at different correlation levels, whereas other abiotic environments responded differently to phytoplankton and zooplankton. The water quality is highest upstream, where there are pepper plantations, and gradually decreases as it flows downstream. The station near tin mining activities was the most polluted.

Both Biotic and Abiotic Factors Shape the Spatial Distribution of Aboveground Biomass in a Tropical Karst Seasonal Rainforest in South China

Forest biomass accumulation is fundamental to ecosystem stability, material cycling, and energy flow, and pit lays a crucial role in the carbon cycle. Understanding the factors influencing aboveground biomass (AGB) is essential for exploring ecosystem functioning mechanisms, restoring degraded forests, and estimating carbon balance in forest communities. Tropical karst seasonal rainforests are species-rich and heterogeneous, yet the impact mechanisms of biotic and abiotic factors on AGB remain incompletely understood. Based on the survey data of a 15 ha monitoring plot in a karst seasonal rainforest in Southern China, this study explores the distribution characteristics of AGB and its intrinsic correlation with different influencing factors. The results show that the average AGB of the plot is 125.7 Mg/ha, with notable variations among habitats, peaking in hillside habitats. Trees with medium and large diameters at breast height (DBH ≥ 10 cm) account for 83.94% of the aboveground biomass (AGB) and are its primary contributors; dominant tree species exhibit higher AGB values. Both biotic and abiotic elements substantially influence AGB, with biotic factors exhibiting the largest influence. Among abiotic factors, topographic factors have a strong direct or indirect influence on AGB, while soil physicochemical properties have the smallest indirect impact. This research provides a comprehensive understanding of AGB distribution and its influencing factors in tropical karst forests (KFs), contributing to the management of carbon sinks in these ecosystems.