Subtropical Zone Research Articles

The Analysis of NPP Changes under Different Climatic Zones and under Different Land Use Types in Henan Province, 2001–2020

Net Primary Productivity (NPP) is a crucial indicator of ecological environment quality. To better understand the carbon absorption and carbon cycling capabilities of Henan Province, this study investigates the trends and driving factors of NPP across different climatic zones and land use types. The Theil–Sen Median trend analysis method and the Mann–Kendall trend test are employed to monitor NPP changes from 2001 to 2020. The average annual NPP in Henan Province during this period was 414.61 gC·m−2·year−1, showing a significant increasing trend with a growth rate of 3.73 gC·m−2·year−1. Spatially, both the annual average NPP and its increase rate were higher in the western part of Henan compared to the eastern part, and NPP variability was more stable in the southern region than in the northern region. By classifying climatic zones and using the Geodetector method to assess NPP sensitivity to natural factors, the results show that climate and vegetation factors jointly influence NPP variations, with annual precipitation being the primary natural factor affecting NPP trends in Henan Province from 2001 to 2020. By analyzing the NPP gain and loss matrix, the impact of land use changes on NPP was evaluated. Forests had the highest average annual NPP at 483.52 gC·m−2·year−1, and the conversion of arable land to urban areas was identified as the primary land change type leading to NPP reductions. In the subtropical zone of Henan, forests, croplands, and grasslands exhibited higher NPP values and increase rates compared to those in the warm belt. This study provides new insights into the spatial variation of NPP caused by changes in climatic zones and land use types.

Modern pollen distribution along a Himalayan elevation gradient in Central Nepal

Modern pollen distribution and its relationship to environmental variables in tropical to alpine vegetation zones are investigated to provide a reference for palaeoenvironmental reconstructions and to improve the understanding of pollen dispersal patterns in Central Nepal. A total of 100 samples (from soil and moss) were collected from along an elevational gradient ranging from 173 to 4615 m above sea level. Results show that the alpine zone is dominated by arboreal pollen (AP) and the sub-alpine zone also shows good representation of coniferous taxa pollen such as Pinus, Abies, Tsuga, and Picea along with Ericaceae. The temperate zone has a good representation of Quercus (Evergreen) and Pinus pollen, whereas the sub-tropical zone is characterized by Alnus pollen and agricultural taxa such as Cerealia (planted Poaceae) and Brassicaceae. In the tropical zone, non-arboreal pollen (NAP), mainly Cerealia dominate, reflecting intensive agricultural practices. Shorea is completely silent in pollen representation. A redundancy analysis indicates that elevation is the primary factor influencing pollen distribution in this region. Overall, the pollen data reflect the vegetation distribution but Pinus is over-represented and Shorea is unrepresented, which should be taken into consideration when interpreting fossil pollen in Central Nepal.

Phlebotomine sand flies (Diptera: Psychodidae) of Bosnia and Herzegovina: distribution, ecology and environmental preferences

Sand flies (Diptera: Phlebotominae) are the principal vectors for the protozoan parasites Leishmania spp. and for phleboviruses. The sand fly fauna on the Balkan Peninsula, including Bosnia and Herzegovina (BIH), is diverse and the circulation of Leishmania infantum as well as phleboviruses has been proven. However, recent data on the sand fly fauna in BIH are scarce. In this study, we surveyed understudied regions in central and northeastern BIH to update the sand fly distribution and gain insights into the ecological and environmental factors shaping their appearance. CDC light trapping was conducted in 2022 and 2023 and a combination of morphological and molecular methods (cytochrome oxidase I barcoding) was performed for species identifications. We mapped the currently known distribution, modelled climatic suitability patterns and performed environmental analyses by applying machine learning methods. In addition, we analyzed blood meals by host gene sequencing and MALDI-TOF peptide mass mapping and screened for Leishmania spp. DNA and Phlebovirus RNA.Altogether, 591 sand flies of four species were trapped, predominantly Phlebotomus neglectus (97 %), but also Ph. balcanicus, Ph. mascittii, and Ph. papatasi. Records of seven sand fly species known to be endemic were plotted onto distribution maps based on 101 datapoints, identifying Ph. neglectus as the overall predominant species. The environmental analyses of sand fly species indicated variation in altitudinal, thermal, and precipitation conditions across the sand fly-positive sites. Phlebotomus simici, Phlebotomus tobbi, and Sergentomyia minuta are typically found exclusively in Mediterranean and subtropical climate zones, whereas other species typically inhabit continental regions. The Inverse Distance Weighted (IDW) interpolation of sand fly species numbers and Shannon entropy values suggested the southeastern coastal region of BIH as a primary focus for sand fly occurrence. This finding was corroborated by modeled average climatic suitability patterns for sand flies, depicting four distinct meso-regions for sand fly occurrence. The results of the ensemble method highlight the importance of annual precipitation to distinguish between positive and negative sand fly trapping sites in BIH. In total, 55 blood meals of two sand fly species, Ph. neglectus and Ph. balcanicus, were analyzed and five host species identified.Our comprehensive assessment of ecological and environmental preferences of sand flies in BIH may support further entomological surveys and help to better understand and evaluate potential hot spots of disease transmission in the country.

Multi-omics analyses reveal the mechanisms underlying the responses of Casuarina equisetifolia ssp. incana to seawater atomization and encroachment stress

Casuarina equisetifolia trees are used as windbreaks in subtropical and tropical coastal zones, while C. equisetifolia windbreak forests can be degraded by seawater atomization (SA) and seawater encroachment (SE). To investigate the mechanisms underlying the response of C. equisetifolia to SA and SE stress, the transcriptome and metabolome of C. equisetifolia seedlings treated with control, SA, and SE treatments were analyzed. We identified 737, 3232, 3138, and 3899 differentially expressed genes (SA and SE for 2 and 24 h), and 46, 66, 62, and 65 differentially accumulated metabolites (SA and SE for 12 and 24 h). The Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis showed that SA and SE stress significantly altered the expression of genes related to plant hormone signal transduction, plant–pathogen interaction, and starch and sucrose metabolism pathways. The accumulation of metabolites associated with the biosynthetic pathways of phenylpropanoid and amino acids, as well as starch and sucrose metabolism, and glycolysis/gluconeogenesis were significantly altered in C. equisetifolia subjected to SA and SE stress. In conclusion, C. equisetifolia responds to SA and SE stress by regulating plant hormone signal transduction, plant–pathogen interaction, biosynthesis of phenylpropanoid and amino acids, starch and sucrose metabolism, and glycolysis/gluconeogenesis pathways. Compared with SA stress, C. equisetifolia had a stronger perception and response to SE stress, which required more genes and metabolites to be regulated. This study enhances our understandings of how C. equisetifolia responds to two types of seawater stresses at transcriptional and metabolic levels. It also offers a theoretical framework for effective coastal vegetation management in tropical and subtropical regions.

Distribution and growth potential of wild Pittosporum tobira in the subtropical supratidal zone

The use of local native plant species for ecological restoration and rehabilitation is considered an important strategy for nature-based solutions. To achieve this goal, the key work is to understand the distribution of local native plants and their limiting factors. Pittosporum tobira is a keystone species of the vegetation community in subtropical coastal areas, and it plays an essential role in the function and stability of the coastal vegetation buffer zone. The aim of this study was to identify the factors that restrict the growth of P. tobira in the subtropical supratidal zone. We investigated the growth and development of P. tobira plants at three field sites, Dongtou Island (DT), Yuhuan Island (YH), and Cangnan County (CN), in Zhejiang Province, China. To investigate the key factors restricting the growth of this species, we sampled soils from both the supratidal zone and the P. tobira habitat zone. Soils in the supratidal zone showed typical characteristics of sodium chloride-type saline-alkali soil, and the soluble salts content showed wide fluctuations. Some soils in the supratidal zone showed severe salinization. The soil pH and soluble salts contents were higher, but soil organic matter content was lower, in the supratidal zone than in the P. tobira habitat zone. Among the three wild P. tobira habitat sites, DT had the lowest soil nutrient contents. In soil from the DT site, the soluble salts content was 150 % higher and soil organic matter content was 50 % lower than those in soils from the YH and CN sites. Compared with P. tobira growing at the CN and YH sites, those growing at the DT site showed higher antioxidant enzyme activity, higher organic osmotic regulatory substances content, and lower malondialdehyde content in the leaves and roots. These results suggest that the growth and distribution of P. tobira are affected by the organic matter content, pH, and soluble salts content in soil. Among the three P. tobira populations studied here, the population at DT was the most tolerant to the highly saline conditions in this subtropical coastal area, and has potential applications in landscape restoration of the supratidal zone.

Results and Discussion of Dengue Model with Temperature Effects in Interval Environment

We have investigated a dengue model with temperature effects under interval uncertainty in this work. This study observed the Aedes aegypti temperature-dependent entomological parameters that affect dengue illness transmission dynamics in Taiwan's subtropical zone. A vector-host transmission model was used to examine how temperature fluctuations influence the development of pre-adult mosquitoes, their egg-laying rates, adult mortality, and the incubation rate of viruses within them. This study showed that although estimations of entomological parameters were positively correlated with slow temperature rises, no such correlation was detected with mosquito mortality or maturation rates, underscoring the slow rate of maturation of pre-adult mosquitoes. The findings suggest that the dynamic modeling of vector-host interactions is significantly influenced by temperature. Additionally, our modeling indicates that a temperature range of about 32°C is ideal for dengue transmission. In the future, control measure modeling and cost-effectiveness assessments may benefit from these insights.

The impact of green roofs’ composition on its overall life cycle

Green roof systems have been developed to improve the environmental, economic, and social aspects of sustainability. Selecting the appropriate version of the green roof composition plays an important role in the life cycle assessment of a green roof. In this study, 10 compositions of an intensive green roof for moderate zone and 4 green roof compositions for different climatic conditions were designed and comprehensively assessed in terms of their environmental and economic impacts within the “Cradle-to-Cradle” system boundary. The assessment was carried out over a 50-year period for a moderate climate zone. The results showed that asphalt strips and concrete slab produced the highest total emissions. It was found that most greenhouse gases emissions were released in the operational energy consumption phase and in the production phase. The energy consumption phase (48.78%) for automatic irrigation and maintenance caused the highest Global Warming Potential (GWP) value (758.39 kg CO2e) in the worst variant, which also caused the highest life cycle cost (878.47€). On the contrary, in the best variant, planting more vegetation and lower maintenance and irrigation requirements led to a reduction in GWP (445.0 kg CO2e), but in terms of cost (506.6€) this composition didn't represent the best variant. The Global Warming Potential Biogenic (GWP-bio) compared to the Global Warming Potential Total (GWP-total) represents a proportion ranging from 0.8% to 78% depending on the proposed vegetation. Overall higher biogenic carbon values (up to 1525 kg CO2e) were observed for the proposed tall vegetation of Magnolia, Red Mulberry, Hawthorne, Cherry, and Crab-apple Tree. Based on the results of the multicriteria analysis, which included core environmental & economic parameters, biogenic carbon emission levels, the outcome of this paper proposed optimal green roof composition. Optimal intensive green roof composition was subjected to a sensitivity analysis to determine the impact of changing climatic conditions on CO2 emissions and life cycle costs. The results of the sensitivity analysis show that the optimal variant of the green roof can be implemented in the cold and subtropical zone with regard to CO2 emissions, but not with regard to life cycle costs.

Response of actinidia deliciosa plants to abiotic stress in the Russian subtropical zone

The article presents a general description of the culture of Actinidia deliciosa, grown in the humid subtropics of Russia. The work was carried out since 2017 at the site of the Adler experimental station of the branch of the Federal Research Center of the N.I. Vavilov All-Russian Institute of Plant Genetic Resources and in the laboratory of plant physiology and biochemistry of the Subtropical Scientific Center of the Russian Academy of Sciences, Sochi. Physiological and biochemical indicators were determined that reflect the resistance of actinidia plants planted in 1988 to environmental stress factors to identify the most adapted varieties to the conditions of the humid subtropics of the Krasnodar Territory. The soil is alluvial meadow with low humus. The varieties studied were late ripening Hayward; Ellison, Abbott and Bruno – early; Monty – medium; Tomuri (pollinator of kiwi female varieties). The indicator organ is physiologically mature actinidia leaves, which were selected from May to September against the backdrop of a natural increase in air temperature. Water deficit was in 2022–2023 is 29.62–36.46%, the minimum is for the Ellison and Monty varieties (29.62–30.21), the maximum is Abbott (36.46%). The dry matter content is 25.47–35.53%, the water content of leaf blades is 46.09-62.66%. The Monti, Hayward and Tomuri varieties are the most resistant to the weather and climatic conditions of the Russian subtropical zone.

Endophytic fungi from Cissus quadrangularis plant a promising source of bioactive compounds.

Cissus quadrangularis is a succulent, perennial plant belonging to the family Vitaceae typically found in Asia and Africa's tropical and subtropical forest zones. It is an ancient medicinal plant, containing phytosterols, polyphenols, flavonoids, carbohydrates, and ascorbic acid. Due to the presence of phytosterols it plays a crucial role in bone fracture healing. However, due to the limited resources of these medicinal plants there is a need to search for a reservoir of biologically active metabolites. This medicinal property of the plants therefore may be attributed to the endophytic fungi within the plant. This study includes isolation of endophytic fungi from C. quadrangularis and the characterization of fungal extracts. Three endophytes were isolated namely Colletotrichum gloeosporioides, Colletotrichum siamense and Phoma sp. The qualitative analysis of targeted metabolites from Cissus quadrangularis stem and fungal extracts of all the three endophytes showed the presence of phytosterols. Methanol extracts of endophytes and C. quadrangularis plant exhibit significant antioxidant and the radical scavenging activity because of the presence of β-carotene. The Ic50 value for stem and isolated endophytes was 5.748, 19.937, 7.00, and 6.493 respectively. This study will give further scope for studying the bone healing ability of phytosterol from the endophytic isolates of C. quadrangularis plant.

Genotypic and Phenotypic Analyses Show Ralstonia solanacearum Cool Virulence is a Quantitative Trait Not Restricted to "Race 3 biovar 2".

Most Ralstonia solanacearum species complex strains cause bacterial wilts in tropical or subtropical zones, but the group known as Race 3 biovar 2 (R3bv2) is cool virulent and causes potato brown rot at lower temperatures. R3bv2 has invaded potato-growing regions around the world but is not established in the United States. Phylogenetically, R3bv2 corresponds to a subset of the R. solanacearum phylotype IIB clade, but little is known about the distribution of the cool virulence phenotype within phylotype IIB. Therefore, genomes of 76 potentially cool virulent phylotype IIB strains and 30 public genomes were phylogenetically analyzed. A single clonal lineage within the sequevar 1 subclade of phylotype IIB that originated in South America has caused nearly all brown rot outbreaks worldwide. To correlate genotypes with relevant phenotypes, we quantified virulence of ten Ralstonia strains on tomato and potato at both 22°C and 28°C. Cool virulence on tomato did not predict cool virulence on potato. We found that cool virulence is a quantitative trait. Strains in the sequevar 1 pandemic clonal lineage caused the most disease, while other R3bv2 strains were only moderately cool virulent. However, some non-R3bv2 strains were highly cool virulent and aggressively colonized potato tubers. Thus, cool virulence is not consistently correlated with strains historically classified as R3bv2 group. To aid detection of sequevar 1 strains, this group was genomically delimited in the LINbase web server and a sequevar 1 diagnostic primer pair was developed and validated. We discuss implications of these results for the R3bv2 definition.

Mangrove wetland recovery enhances soil carbon sequestration capacity of soil aggregates and microbial network stability in southeastern China

Mangrove wetlands are highly productive ecosystems in tropical and subtropical coastal zones, play crucial roles in water purification, biodiversity maintenance, and carbon sequestration. Recent years have seen the implementation of pond return initiatives, which have facilitated the gradual recovery of mangrove areas in China. However, the implications of these initiatives for soil aggregate stability, microbial community structure, and network interactions remain unclear. This study assesses the impacts of converting ponds to mangroves—both in natural and artificially restored settings—on soil aggregate stability and microbial networks at typical mangrove restoration sites along China's southeastern coast. Our observations confirmed our hypothesis that pond-to-mangrove conversions resulted in an increase in the proportion of large aggregates (>0.25 mm), improved soil aggregate structural stability, and increased carbon sequestration. However, mangrove recovery led to a decrease in the abundance and diversity of soil fungi communities. In terms of co-occurrence networks, naturally restored mangrove wetlands exhibited more nodes and edges. The naturally recovered mangrove wetlands demonstrated a higher level of community symbiosis compared to those that were manually restored. Conversely, bacterial networks showed a different pattern, with significant shifts in key taxa related to carbon sequestration functions. For instance, the proportion of bacterial Desulfobacterota and fungi Basidiomycota in natural recovery mangrove increased by 15.03 % and 7.82 %, respectively, compared with that in aquaculture ponds. Soil fungi and bacteria communities, as well as carbon sequestration by aggregates, were all positively correlated with soil total carbon content (P < 0.05). Both bacterial and fungal communities contributed to soil aggregate stability. Our study highlights the complex relationships between soil microbial communities, aggregate stability, and the carbon cycle before and after land-use changes. These findings underscore the potential benefits of restoring mangrove wetlands, as such efforts can enhance carbon storage capacity and significantly contribute to climate change mitigation.

Oral Myiasis in Anterior Palate - A Rare Case Report &amp; Review of Literature

Oral myiasis was coined by Reverend F. William Hope in 1840. It is a rare pathology and risk to the patients in humans suffering from myiasis. It has a higher incidence in rural areas and in developing countries having hot climatic conditions such as tropical and sub-tropical zones of Africa and America. Most of the infestations are associated with various predisposing factors such as poor oral hygiene, suppurative lesions, senility, alcoholism, and debilitating conditions and reported in post-extraction socket, trauma. The diagnosis is made basically by the presence of maggots. This article deals with oral myiasis in cerebral palsy female patient. The treatment consisted of manual removal of the maggots by topical application of turpentine oil and surgical debridement of the wound Keywords: Diptera fly, human myiasis, ivermectin, musca domestica, myiasis, parasitic infection

Experimental and numerical investigation of the effects of passive radiative cooling-based cool roof on building energy consumption

Passive radiative cooling is an energy-efficient method that reduces indoor temperature and cooling load in buildings, thus contributing to significant energy savings. This study investigates the thermal performance of the passive radiative cooling-based cool roof (PRC-CR) based on experimental and numerical analysis in terms of indoor air temperature and space cooling load indicators. Two experiment rooms constructed from concrete are developed with an indoor air temperature control system. One is the PRC-CR room with the roof covered by a passive radiative cooling metamaterial and the other is the reference room with a concrete roof. Long-term testing results in Hefei show that the indoor air temperature of the PRC-CR room is 5.5 °C lower in maximal and 1.8 °C lower on average than that of the reference room in summer when the indoor air temperature control system is off. Besides, when the indoor air temperature control system is switched on, the PRC-CR room achieves a 29.1% reduction in daily cooling load in summer and a 4.1% increase in daily heating load in winter, which suggests that passive radiative cooling can indeed save energy in cooling season (i.e., hot season) but cause overcooling in heating season (i.e., cold season). In addition, a simulation building model is developed to further investigate the effect of the PRC-CR on the energy consumption of buildings in different locations. The predicted results show that PRC-CR reduces the total load of buildings in cooling load prevailing regions (e.g., tropical zones, subtropical zones, and the vast majority of warm temperate zones), while increasing the total load of buildings in heating load dominant regions (e.g., most middle temperate zones, cold temperate zones, and plateau climate zones). In summary, this work demonstrates both the positive and negative effects of PRC-CR, providing valuable insights into PRC-CR applications.

Tree Ring Blue Intensity-Based August Temperature Reconstruction for Subtropical Central China

Tree-ring blue intensity (BI) has the potential to provide information on past summer temperatures of a similar quality to that of tree-ring maximum latewood density and at a substantially reduced cost. To explore the applicability of BI in subtropical regions, the inverted BI for the earlywood, latewood, and the delta BI (DBI) parameters, together with tree-ring width of subalpine fir (Abies fargesii Franch.) in the Shennongjia area of China, were measured, and the corresponding chronologies were developed. The relationships of these chronologies with the monthly mean temperature and monthly precipitation were explored via correlation analysis. Results show that the DBI chronology is closely related to the temperature in August of the current year, indicating that BI, specifically delta BI, data are suitable for use in dendroclimatology studies in subtropical areas. The resultant mean temperature August reconstruction, based on DBI, explains 40.8% of the temperature variance and is robustly validated using independent periods from the calibration. This pilot study not only highlights the potential of DBI for temperature reconstruction in China but also offers valuable insights into historical climate variations in the Shennongjia region. Moreover, it shows the potential for utilizing such tree-ring data from low-latitude regions to derive past climate data in subtropical warm-humid zones.

Characteristics and assembly mechanisms of bacterial and fungal communities in soils from Chinese forests across different climatic zones

Forest soils are intricate ecosystems that harbor a diverse array of microorganisms, yet our current understanding of the characteristics and environmental implications of forest soil microbiomes remains limited. Here we present a continental-scale study on soil microbiomes of ten forests in China, spanning latitudes from 18°54′N to 50°48′N, resulting in a comprehensive catalog of bacterial and fungal operational taxonomic units (OTUs). Both bacterial and fungal communities exhibited discernible spatial variations in taxonomic and phylogenetic diversity. The composition of bacterial communities varied distinctively due to climatic zones—cold temperate, temperate, subtropical, and tropical—whereas fungal communities did not exhibit such pronounced distinctions. The co-occurrence network complexity of bacterial communities displayed a decremental trend along the cold temperate, temperate, subtropical, and tropical zones, whereas that of fungal communities displayed an incremental pattern. These results may be attributed to the facts that low temperatures sustain a high biomass of bacteria and foster increased interactions, while high temperatures and precipitation stimulate fungi-plant interactions. Furthermore, community assembly modeling revealed that forest soil microbial communities were dominated by stochastic processes. The bacterial community structure was mainly driven by homogeneous selection (26–41%) and dispersal limitation (35–44%), whereas dispersal limitation (51–56%) had the greatest impact on fungal community structure. Notably, bacterial functional genes associated with carbon fixation were more abundant in cold temperate soils compared to tropical soils. This study sheds light on spatial variations of forest soil microbiomes in China, enhancing further understanding of their response to global changes and implications for soil organic carbon cycles.

Liver Cancer Mortality Disparities at a Fine Scale Among Subpopulations in China: Nationwide Analysis of Spatial and Temporal Trends.

China has the highest number of liver cancers worldwide, and liver cancer is at the forefront of all cancers in China. However, current research on liver cancer in China primarily relies on extrapolated data or relatively lagging data, with limited focus on subregions and specific population groups. The purpose of this study is to identify geographic disparities in liver cancer by exploring the spatial and temporal trends of liver cancer mortality and the years of life lost (YLL) caused by it within distinct geographical regions, climate zones, and population groups in China. Data from the National Death Surveillance System between 2013 and 2020 were used to calculate the age-standardized mortality rate of liver cancer (LASMR) and YLL from liver cancer in China. The spatial distribution and temporal trends of liver cancer were analyzed in subgroups by sex, age, region, and climate classification. Estimated annual percentage change was used to describe liver cancer trends in various regions, and partial correlation was applied to explore associations between LASMR and latitude. In China, the average LASMR decreased from 28.79 in 2013 to 26.38 per 100,000 in 2020 among men and 11.09 to 9.83 per 100,000 among women. This decline in mortality was consistent across all age groups. Geographically, Guangxi had the highest LASMR for men in China, with a rate of 50.15 per 100,000, while for women, it was Heilongjiang, with a rate of 16.64 per 100,000. Within these regions, the LASMR among men in most parts of Guangxi ranged from 32.32 to 74.98 per 100,000, whereas the LASMR among women in the majority of Heilongjiang ranged from 13.72 to 21.86 per 100,000. The trend of LASMR varied among regions. For both men and women, Guizhou showed an increasing trend in LASMR from 2013 to 2020, with estimated annual percentage changes ranging from 10.05% to 29.07% and from 10.09% to 21.71%, respectively. Both men and women observed an increase in LASMR with increasing latitude below the 40th parallel. However, overall, LASMR in men was positively correlated with latitude (R=0.225; P<.001), while in women, it showed a negative correlation (R=0.083; P=.04). High LASMR areas among men aligned with subtropical zones, like Cwa and Cfa. The age group 65 years and older, the southern region, and the Cwa climate zone had the highest YLL rates at 4850.50, 495.50, and 440.17 per 100,000, respectively. However, the overall trends in these groups showed a decline over the period. Despite the declining overall trend of liver cancer in China, there are still marked disparities between regions and populations. Future prevention and control should focus on high-risk regions and populations to further reduce the burden of liver cancer in China.

Winter entrainment drives the mixed layer supply of manganese in the Southern Ocean

AbstractDespite the subnanomolar dissolved manganese concentrations that can co‐limit Southern Ocean primary production, their physical supply mechanisms during winter, for biological consumption in spring and summer have not yet been explored. During austral winter and spring 2019, two cruises were conducted in the Atlantic sector of the Southern Ocean, to determine the distribution and surface water supply mechanisms of dissolved manganese in the upper water column. The supply mechanisms were used to calculate the total flux of dissolved manganese to productive surface waters and were compared to biological consumption estimates. Mean dissolved manganese concentrations in the upper water column (&lt; 500 m) during winter and spring were comparably low (≤ 0.34 nmol kg−1; p &gt; 0.05), with seasonal mixed layer reservoir sizes averaging 65.21 ± 12.93 and 21.64 ± 19.32 μmol m−2, respectively. Winter entrainment contributed 89.33–99.99% (average 97.26% ± 5.28%) of the total dissolved manganese flux, while diapycnal diffusion contributed 0.52–10.58% (average 4.92% ± 5.14%), was identified as the dominant mechanisms for transporting dissolved manganese into the mixed layer in the subantarctic zone, polar frontal zone, and antarctic zone. Here, the winter physical supply rates were higher than the estimated consumption rates during spring, meeting phytoplankton biological demands. Whereas in the subtropical zone, the supply rates were lower than the consumption rates, indicating the presence of additional supply mechanisms such as coastal upwelling, which may help to meet the biological demands in this region.

Dendrodorididae (Heterobranchia, Nudibranchia) from Persian Gulf with a description of a new species of Doriopsilla and remarks on the family

The family Dendrodorididae has a global distribution, with prevalence in tropical and subtropical intertidal zones. Three species of Dendrodorididae were collected from the intertidal zone of the northern coast of the Persian Gulf in Iran. Based on anatomical, histological, and molecular investigations they can be assigned to Dendrodoris fumata, Dendrodoris nigra, and a new species of Doriopsilla, D. aroni sp. nov. Molecular analyses of CO1 and 16S, including all genera of Dendrodorididae, members of the sister taxon Phyllidiidae, and other dorid outgroups resulted in a polyphyletic genus Dendrodoris, which is in contrast to the nuclear gene studies. Our molecular results confirm the differentiation between Dendrodoris rubra and D. fumata. Dendrodoris nigra, D. fumata, and D. krusensternii each consist of several clades, indicating cryptic species complexes requiring further investigation. We describe the presence of bacteria for the first time in the vestibular gland of D. fumata. Validation of the specimens of Doriopsilla from the Persian Gulf as a new species is supported by haplotype networking, genetic distance, and ABGD analyses of mitochondrial genes. Our CO1 analysis confirms a previous hypothesis that Cariopsilla is a junior synonym of Doriopsilla.

Integrative analysis of transcriptome and metabolome reveal the differential tolerance mechanisms to low and high salinity in the roots of facultative halophyte Avicennia marina.

Mangroves perform a crucial ecological role along the tropical and subtropical coastal intertidal zone where salinity fluctuation occurs frequently. However, the differential responses of mangrove plant at the combined transcriptome and metabolome level to variable salinity are not well documented. In this study, we used Avicennia marina (Forssk.) Vierh., a pioneer species of mangrove wetlands and one of the most salt-tolerant mangroves, to investigate the differential salt tolerance mechanisms under low and high salinity using inductively coupled plasma-mass spectrometry, transcriptomic and metabolomic analysis. The results showed that HAK8 was up-regulated and transported K+ into the roots under low salinity. However, under high salinity, AKT1 and NHX2 were strongly induced, which indicated the transport of K+ and Na+ compartmentalization to maintain ion homeostasis. In addition, A. marina tolerates low salinity by up-regulating ABA signaling pathway and accumulating more mannitol, unsaturated fatty acids, amino acids' and L-ascorbic acid in the roots. Under high salinity, A. marina undergoes a more drastic metabolic network rearrangement in the roots, such as more L-ascorbic acid and oxiglutatione were up-regulated, while carbohydrates, lipids and amino acids were down-regulated in the roots, and, finally, glycolysis and TCA cycle were promoted to provide more energy to improve salt tolerance. Our findings suggest that the major salt tolerance traits in A. marina can be attributed to complex regulatory and signaling mechanisms, and show significant differences between low and high salinity.

Leaf nutrient-based processes of conservatism and convergence regulate the vertical stratification of plant growth forms during subtropical forest degradation

Unveiling the ecological and evolutionary mechanisms that guide the differentiation of various plant growth forms into vertical forest strata during forest degradation continues to pose a challenge. We utilized the biogeochemical niche theory to decipher these mechanisms. We measured leaf concentrations of basal elements (C, N, P, K, Ca, and Mg) and used them to generate the biogeochemical niches in herbs, shrubs, trees, and climbers from different vertical strata within a degraded forest and its neighboring mature forest in subtropical montane zones. Our results showed that biogeochemical niches varied significantly among growth forms. Biogeochemical niches also differed significantly between species in the degraded and mature forests, as evidenced by the significantly lower leaf C concentration relative to other nutrients in degraded forest species. This could be attributable mainly to the expansive canopy openness in the degraded forest, facilitating the colonization of light-demanding self-supporters and climbers. The phylogenetic signals in leaf nutrient concentrations were significantly present across all species, suggesting the general similarities in biogeochemical niches among closely related species. Following evolutionary model comparisons, stabilizing selection towards varying optimal leaf nutrient concentrations for distinct growth forms in the degraded or mature forest emerged as the most suitable model. Our study thus highlights the important role of phylogenetic biogeochemical niche conservatism and stabilizing selection towards various optimal leaf nutrient compositions for diverse growth forms in both degraded and mature forests in the formation of vertical plant communities during subtropical forest degradation.