Horizontal Distribution Patterns Research Articles

Two-Dimensional Amphibian Diversity along a 3500 m Elevational Gradient at the Eastern Edge of the Qinghai-Xizang Plateau.

Amphibians serve as reliable indicators of ecosystem health and are the most threatened group of vertebrates. Studies on their spatial distribution pattern and threats are crucial to formulate conservation strategies. Gongga Mountains, with a peak at 7509 m a.s.l. and running latitudinally, are in the center of the Hengduan Mountains Range and at the eastern steep edge of the Qinghai-Xizang Plateau, providing heterogeneous habitats and varied niches for amphibians. In this study, we combined 83 days of field work with information from 3894 museum specimens that were collected over the past 80 years, and identified twenty amphibian species belonging to seven families and twelve genera by morphology. Of these species, seven were listed in the threatened categories of the Red List of China's Biodiversity and thirteen were endemic to China. Ten species were found on the plateau side (western slope) and eleven species were found on the other side close to the Sichuan Basin (eastern slope). Only one species was found on both sides, indicating different community structures horizontally. The species richness was unimodal vertically and peaking at mid elevation on both sides, with the maximum number (ten vs. nine) of species occurring at 3300-3700 vs. 1700-1900 m a.s.l. and in different types of vegetation. The elevation span and body length of species distributed on both slopes did not show significant differences. These findings help to understand the horizontal and vertical distribution pattern of amphibian diversity, laying a foundation for future biogeographical and conservation research in this area.

Latitudinal variations of iron chemical speciation in the euphotic zone of the central Pacific Ocean

The concentrations of dissolved iron (DFe), iron-binding ligands (LFe), and electroactive humic-like substances (eHS) were revealed in the upper 200 m along the 170°W latitudinal transect of the central Pacific Ocean in summer, which was weakly influenced by terrestrial input. DFe was largely depleted throughout the transect, except in the Bering Sea, and below 100 m in the North Pacific Subarctic Gyre. The concentration of LFe was lowest within the subtropical gyres and was lower in the Southern Hemisphere, which is consistent with the results from the Atlantic Ocean. The vertical distribution of LFe was relatively constant in the subtropical regions, whereas in the subarctic regions the subsurface maximum appeared around or over the subsurface chlorophyll maximum at some stations. The higher concentration of LFe in the subarctic regions coincides with a lower stability constant, which suggests a higher contribution of weaker ligands, including humic and exopolymeric substances. The horizontal and vertical distribution patterns of eHS were largely similar to those of LFe, supporting their significant contribution to iron-binding capacity in the upper 200 m, particularly in the subarctic regions. However, the eHS concentration was only weakly correlated with that of the fluorescently determined humic-like substances, demonstrating the substantially different chemical properties of the two humic-like substances. The strong positive correlation between the concentrations of eHS and chlorophyll a and Synechococcus strongly suggests their biological origins. However, further research is required to examine whether eHS are directly produced by phytoplankton or released via relevant biological processes, such as grazing, bacterial composition, and viral lysis.

Comparative genomic analysis provides insights into the genetic diversity and pathogenicity of the genus Brucella.

Some Brucella spp. are important pathogens. According to the latest prokaryotic taxonomy, the Brucella genus consists of facultative intracellular parasitic Brucella species and extracellular opportunistic or environmental Brucella species. Intracellular Brucella species include classical and nonclassical types, with different species generally exhibiting host preferences. Some classical intracellular Brucella species can cause zoonotic brucellosis, including B. melitensis, B. abortus, B. suis, and B. canis. Extracellular Brucella species comprise opportunistic or environmental species which belonged formerly to the genus Ochrobactrum and thus nowadays renamed as for example Brucella intermedia or Brucella anthropi, which are the most frequent opportunistic human pathogens within the recently expanded genus Brucella. The cause of the diverse phenotypic characteristics of different Brucella species is still unclear. To further investigate the genetic evolutionary characteristics of the Brucella genus and elucidate the relationship between its genomic composition and prediction of phenotypic traits, we collected the genomic data of Brucella from the NCBI Genome database and conducted a comparative genomics study. We found that classical and nonclassical intracellular Brucella species and extracellular Brucella species exhibited differences in phylogenetic relationships, horizontal gene transfer and distribution patterns of mobile genetic elements, virulence factor genes, and antibiotic resistance genes, showing the close relationship between the genetic variations and prediction of phenotypic traits of different Brucella species. Furthermore, we found significant differences in horizontal gene transfer and the distribution patterns of mobile genetic elements, virulence factor genes, and antibiotic resistance genes between the two chromosomes of Brucella, indicating that the two chromosomes had distinct dynamics and plasticity and played different roles in the survival and evolution of Brucella. These findings provide new directions for exploring the genetic evolutionary characteristics of the Brucella genus and could offer new clues to elucidate the factors influencing the phenotypic diversity of the Brucella genus.

Spatial equity of urban parks from the perspective of recreational opportunities and recreational environment quality: A case study in Singapore

Spatial equity in urban park recreational services can significantly contribute to sustainable urban planning. However, there are shortcomings in research comparing the spatial equity of different categories of parks and urban parks overall from the perspective of recreational opportunities and recreational environment quality available to residents across various neighborhoods. In this paper, emphasizing park access within a 10-minute walk, we proposed an evaluation system at the neighborhood level for regional parks, community parks, and urban parks overall (regional and community parks combined) from this under-researched perspective. Taking Singapore as a case study, the feasibility of this evaluation system has been verified. We applied Lorenz curve, Gini coefficient, locational entropy, and spatial autocorrelation analysis to compare the differences of horizontal spatial equity and spatial distribution patterns of different categories of parks and urban parks overall from the perspective of recreational opportunities and recreational environment quality. Results showed that the horizontal spatial inequity of recreational opportunities is higher than that of recreational environment quality with respect to regional parks, community parks, and urban parks overall. Compared with regional parks, community parks have a greater effect on improving the horizontal spatial equity of recreational opportunities and recreational environment quality of urban parks overall. Park recreational opportunities and recreational environment quality available to residents in each neighborhood have significant spatial accumulation patterns. The evaluation system and its application enable a more comprehensive assessment of the spatial distribution of neighborhood-level park recreational opportunities and recreational environment quality.

Rapid variations of phytoplankton blooms and their dynamics off the Changjiang River Estuary

Phytoplankton frequently blooms in estuaries and coastal seas. Numerous dynamic processes affect these regions, generating complex hydrodynamics that induce intense phytoplankton variability over multiple time scales. Especially, the variability over time scales of 100-101 days (event-scale) is a strong signal that is fundamental to coastal aquatic environments and ecosystems. Based on the historical monitoring of harmful algal bloom events and a fully coupled hydrodynamics-sediment-ecosystem numerical model, this study explored horizontal distribution patterns of the phytoplankton maximum off the Changjiang River Estuary over multiple time scales. Our results showed that the bloom events typically lasted less than a week and horizontal distribution of the horizontal chlorophyll maximum varied over the time scale of days. Tidal forcing was shown to dominate the periodic phytoplankton variability. The variations of river runoff and wind forcing also modulated this variability and added more disturbances. Increased runoff and enhanced summer monsoon wind caused the horizontal chlorophyll maximum to physically extend further offshore, while they also biologically stimulated phytoplankton blooms. The analysis of the time scale showed that the regulation of horizontal chlorophyll maximum responds faster to physical effects than in biological ones. At the same time, during neap tides, the adjustment of phytoplankton to the disturbances associated with the hydrodynamic processes was stably salient. Such adjustment was based on the adaptation to light availability and nutrient supply. This study contributes to the understanding of phytoplankton variability in estuaries affected by multiple physical-biological processes over the time scale of days and benefits to the management of environmental conservation.

Horizontal migration of zooplankton in lake–wetland interfaces. Can temperature-driven surface exchange flows modulate its patterns?

Lake ecology can be affected by exchange flows driven by horizontal temperature gradients in lake–wetland interfaces. In this work, we investigate the hypothesis that thermally driven flows modulate the horizontal migration patterns of freshwater zooplankters. A 48-h field campaign in a shallow lake (Lake Vela, Quiaios, Portugal) was carried out to test this hypothesis. Thermal differences between the littoral and limnetic areas were measured along two transects featuring a Schoenoplectus lacustris and a Myriophyllum aquaticum stand in the littoral. In parallel, the physiochemistry and chlorophyll a, as a proxy for food availability differences between the littoral and the limnetic zones, were monitored. Zooplankton samples were collected for assessing overall and group-specific number-density differences. The diel period (day or night) and the site (littoral or limnetic zone) did not interact significantly to modulate the variation patterns for the studied physiochemical variables, indicating that these parameters should not explain horizontal zooplankton distribution patterns. The expected patterns for zooplankton diel horizontal migration as driven by the presence of visual predators were occasionally confirmed by our limnetic versus littoral abundance records through time, depending on the transect. Group-specific abundance patterns indicate particular features: copepods always preferred the littoral over the limnetic zone regardless of the diel period; chydorids always preferred the littoral zone regardless of the macrophyte stand involved; bosminids tended to preferentially concentrate in the limnetic zone. No consistent relationship was identified between the expected flow direction due to temperature differences and zooplankton abundance changes, although it occasionally occurred through the dataset.

Effects of coal mine waste dump on soil seed bank and vegetation distribution pattern

Long-term occupation of coal gangue dumping sites (CGDS) may destroy ecological environment of nearby area. However, how the CGDS affects the distribution pattern of soil seed banks and vegetation in the nearby area is not clear. In this study, we investigated soil seed bank and vegetation at different distances from the second CGDS of Yangchangwan in Ningdong mining area, Lingwu, Ningxia. The results showed that soil seed bank was mainly distributed in 0-10 cm layer and decreased with increasing soil depth. Species richness of soil seed bank and vegetation first increased and then tended to be stable with increasing distance to the CGDS. The influence range of CGDS on soil seed banks was 300-500 m and was 100-300 m on aboveground vegetation. The CGDS did not affect the vertical distribution pattern of soil seed bank, but significantly affected the horizontal distribution pattern of soil seed banks and aboveground vegetation. The key area of vegetation restoration around the CGDS was between 100 m and 300 m.

Biológiai vízminőségi paraméterek hatásainak vizsgálata a szarvasi Holt-Körösön

One of the essential natural resources is water resource in Hungary. It is threatened by many threats, both quantitative and qualitative. For these reasons, the protection of surface water and groundwater is a priority. The main objective of the present study is to determine which parameters have the greatest influence on the horizontal and vertical distribution patterns of phytoplankton in the water body. The study area is the Holt-Körös, which plays an important ecological, social, economic and recreational role in the region. Between the field and laboratory tests, the following physical, chemical and biological water quality parameters were investigated: water temperature, UV radiation index, Secchi depth, underwater light condition, dissolved oxygen content, suspended solids content, chlorophyll-a content, Fe, NO2-, NO3- NH4+, PO43-, Na+, K+, Mg2+, and pH value.

Horizontal prey distribution determines the foraging performance of short‐ and long‐billed waders in virtual resource landscapes

When waders gather in mixed‐species flocks to feed on benthic prey, differences in morphological traits, foraging strategies and prey selection may allow different species to optimize their energy intake while reducing competition. As the effect of the fine‐scale spatial distribution of resources on energy intake is unknown, we simulated the foraging performance of two types of waders with contrasting body plans and foraging strategies in a variety of virtual mudflats with different horizontal and vertical prey distribution patterns. Although larger, longer‐billed individuals had higher energy intake rates, smaller individuals with shorter bills maintained higher prey capture rates by relocating if prey was insufficiently available. Shorter‐billed individuals struggled more to meet their energetic demands because they selected smaller prey items and had a more limited capacity to metabolize energy from food. Being able to catch larger, high‐quality prey offered a competitive advantage for longer‐billed individuals, which could be a driving force for the evolutionary lengthening of bills in waders. Interestingly, their performance was more affected by the horizontal than by the vertical prey distribution. Quantifying prey distributions may help explain how some wader species can co‐occur in the field and why some wetland areas are unattractive as foraging areas. The work confirms that the foraging performance of larger, longer‐billed birds is not limited by bill size per se, but by the energetic trade‐offs associated with the ability to catch larger prey items more efficiently, increased handling times and higher absolute energy costs. These trade‐offs may become particularly important in landscapes where prey is scarce and spatially patchy.

Effects of the fundamental axes of variation in structural diversity on the forest canopy temperature in an urban area

The spatial distribution and heterogeneity of forest canopy elements reveal the fundamental dimensions of plant structure variations. Forests characterized by greater structural complexity and diversity intercept solar radiation more effectively, directly influencing the thermal environment and energy balance of the canopy. However, the axes of variation in the distribution and heterogeneity of the canopy remain largely unknown, which limits our understanding of how structural diversity responds to canopy temperature variability. Here, we derived a set of structural diversity metrics from a dataset of canopy structure measurements obtained using unmanned aerial vehicle-light detection and ranging across major forest communities in an urban area in 2021 and 2022. We also explored the key axes of structural diversity variability and tested their predictive power for canopy temperature. The results showed that: (1) most of the variability within structural diversity (83.6 % and 81.8 %) was captured by the three key axes in 2021 and 2022. The first axis was primarily driven by structural heterogeneity, representing the heterogeneity of vegetation distribution within the canopy. The second axis was primarily influenced by the interaction between height and cover/openness, indicating the vertical structure and horizontal distribution pattern of the canopy. The third axis represented the horizontal coverage and density of the canopy. (2) In both 2021 and 2022, the second axis was identified as the most influential predictor of canopy temperature, as evidenced by R2 values of 0.46 and 0.28, respectively. The model incorporating all three axes of structural diversity achieved the highest accuracy in predicting the canopy temperature for 2021 (R2 = 0.68, AIC = 81.35, ΔAIC = 0, and RMSE = 0.89). Prior research on canopy temperature prediction has overlooked the true potential of principal component axes derived from structural diversity. The findings present a novel approach for selecting structural diversity indicators for future investigation.

Spatial differences of specialty agriculture development in the mountainous areas of China -- "one village, one product" as an example

With the rapid development of urbanization, the rate of abandonment of arable land in China's mountainous areas has accelerated. Solving the phenomenon of abandonment of arable land has become an important issue in managing the use of China’s arable land, the key to which lies in the development of specialty agriculture using the unique natural environment of mountainous areas. This paper scrutinizes both the horizontal and vertical distribution of specialty agriculture in these areas, drawing upon the “One Village, One Product” dataset provided by the Chinese Ministry of Agriculture and Rural Development. The findings reveal that the horizontal distribution pattern of specialty agriculture exhibits the formation of eight primary clusters. It is intriguing to observe that a majority of these clusters are situated at the intersection of two or three provincial administrative units, with the largest cluster occurring at the border of Chengdu and Chongqing. In terms of the vertical distribution pattern, the specialty agriculture in China’s mountainous areas are mainly distributed at low altitudes, i.e., below 500 m, and at gentle slopes of 4°–8°, and with increases in altitude or slope, the overall amount of specialty agriculture declines rapidly.

Spatiotemporal Heterogeneity of Temperature and Precipitation in Complex Terrain along the Northeastern Margin of the Tibetan Plateau

The study of climate element distribution models under complex terrain conditions is a popular topic in the field of GIS application in climatology, especially in plateau areas with a complex topography and scarce meteorological station information. In this paper, the spatial and temporal heterogeneity of temperature and precipitation at the northeastern edge of the Tibetan Plateau was analyzed by taking the northeastern edge of the plateau as the study area and constructing a topographic spatial statistical model using 47 meteorological stations and digital elevation models from 1981 to 2010. The following conclusions were drawn from the study: (1) The ME of the temperature distribution model for each month is below 0.9 °C; the maximum ME of the precipitation distribution model for each month is −5.808 mm in July, and the precipitation distribution model has similar error characteristics with the temperature distribution model, which can reflect the horizontal zone distribution pattern of meteorological data and can clearly show the changes of temperature and precipitation as the altitude increases. (2) The spatial distribution pattern of temperature is as follows: the temperature in the study area gradually increases from the southwest to the northeast, with Zhouqu County in Linxia Prefecture and Gannan Prefecture as the main high-temperature areas; the spatial distribution of precipitation is as follows: the precipitation in the southwest of the study area is significantly higher than that in the north, and the precipitation in Linxia Prefecture is significantly lower than that in Gannan Prefecture. (3) The temporal distribution pattern of the temperature distribution model is as follows: the overall temperature in the study area is at its lowest level in January, and the maximum temperature is only 2.6 °C, until July, when the maximum temperature rises to 24.2 °C and then gradually starts to decline; the spatial distribution of precipitation is as follows: the precipitation in the study area gradually rises from January, and the maximum precipitation rises to July and then starts to decline, and in December the precipitation falls to the lowest level. The temporal distribution characteristics of the precipitation distribution model are similar to those of the air temperature model, with obvious hydrothermal synchronization characteristics.

Recent Changes in Composition and Distribution Patterns of Summer Mesozooplankton off the Western Antarctic Peninsula

The Southern Ocean has undergone significant climate-related changes in recent decades. As a result, pelagic communities inhabiting these waters, particularly mesozooplankton, have adapted to new conditions. The present study considers the patterns of horizontal and vertical (up to 1000 m) distribution, the composition, abundance, and biomass of mesozooplankton, and the relationships of these parameters to the extreme environmental conditions off the western Antarctic Peninsula throughout the record-warm austral summer season of 2022. Sampling was conducted using the opening/closing Multinet system (0.25 m2 aperture) equipped with five 150-μm mesh nets and a WP-2 net. The mesozooplankton was represented by the three most abundant groups: eggs and larvae of euphausiids such as Euphausia superba, small copepods such as Oithona similis, and large calanoid copepods such as Calanoides acutus, Calanus propinquus, Metridia gerlachei, and Rhincalanus gigas. The composition and quantitative distribution of the mesozooplankton significantly varied: the copepods were abundant in the west, off the Antarctic Peninsula, while eggs and larvae of euphausiids were abundant in the east, off the South Orkney Islands. Most mesozooplankton occurred in the upper 200 m layer, and each taxon showed characteristic depth preference: small copepods, euphausiids larvae, and cirripeds cypris larvae were abundant in the epipelagic layer, while large calanoid copepods, euphausiids eggs, amphipods, pelagic polychaetes, and ostracods were found mostly in the mesopelagic layer. The composition and quantitative distribution of mesozooplankton had clear relationships with environmental factors, particularly with a combination of variables such as water salinity, temperature, and chlorophyll a concentration.

Benthic biogeographic patterns on the deep Brazilian margin.

The Brazilian continental margin (BCM) extends from the Tropical to the Subtropical Atlantic Ocean, with much of its seafloor within deep waters, supporting rich geomorphological features and under wide productivity gradients. Deep-sea biogeographic boundaries on the BCM have been limited to studies that used water mass and salinity properties of deep-water masses, partly as a result of historical under sampling and a lack of consolidation of available biological and ecological datasets. The aim of this study was to consolidate benthic assemblage datasets and test current oceanographic biogeographical deep-sea boundaries (200-5,000 m) using available faunal distributions. We retrieved over 4,000 benthic data records from open-access databases and used cluster analysis to examine assemblage distributions against the deep-sea biogeographical classification scheme from Watling et al. (2013). Starting from the assumption that vertical and horizontal distribution patterns can vary regionally, we test other schemes incorporating latitudinal and water masses stratification within the Brazilian margin. As expected, the classification scheme based on benthic biodiversity is in overall agreement with the general boundaries proposed by Watling et al. (2013). However, our analysis allowed much refinement in the former boundaries, and here we propose the use of two biogeographic realms, two provinces and seven bathyal ecoregions (200-3,500 m), and three abyssal provinces (>3,500 m) along the BCM. The main driver for these units seems to be latitudinal gradients as well as water mass characteristics such as temperature. Our study provides a significant improvement of benthic biogeographic ranges along the Brazilian continental margin allowing a more detailed recognition of its biodiversity and ecological value, and also supports the needed spatial management for industrial activities occurring in its deep waters.

Trapped microplastics within vertical redeposited sediment: Experimental study simulating lake and channeled river systems during resuspension events

Plastic waste and its fragments (microplastics; <5 mm) have been observed in almost all types of environments. However, the mechanisms underlying the flow and transport processes of plastics are unknown. This is particularly valid for river sediments, where complex interactions occur between particles and influence their vertical and horizontal distribution patterns. In this study, we investigated the vertical redistribution of 14 pristine microplastics (MPs) with different densities, sizes, and shapes within disturbed sediment without lateral transport (i.e., low-velocity flow). MPs were spiked into sediments (height: 8 cm) in a column with a height of 1 m (diameter: 6 cm) filled to the top with water. The sediment was perturbed by turning the column upside-down to simulate remobilization and the subsequent deposition of sediment. After the complete sedimentation of the particles, the water column was filtered and the sediment was cut into vertical sections. MPs were then extracted from the sediment using sieves and a density separation method, and were counted under a stereomicroscope. Low-density polymers were mainly recovered in the water column and at the surface of the sediment, whereas high-density polymers were found within all sediment sections. The vertical distribution of high-density polymers changes primarily with the sediment grain size. The distribution of each polymer type changes depending on the size and/or shape of the particles with complex interactions. The observed distributions were compared with the expected distributions based only on the vertical velocity formulas. Overall, the formulas used did not explain the sedimentation of a portion of low-density polymers and predicted a lower distribution in the sediment than those observed in the experiment. In conclusion, this study highlights the importance of considering MPs as multi-dimensional particles and provides clues to understand their fate in low-velocity flow systems, considering that they undergo scavenging in sediments.

Effects of Duct Height and Fire Location on Fire Phenomena of Enclosure with Two Horizontal Vents Installed on Ceiling

The effects of duct height (DH) and fire location (FL) in an enclosure on the mass flow rate and flow pattern of horizontal vent (HV) flow and temperature distribution in the enclosure were investigated through numerical simulations under the condition that two HVs were installed on the ceiling of the enclosure. To evaluate the effect of DH, DHs of HV1 were set to 0.19 m (HV1_DH0.19) and 0.05 m (HV1_DH0.05) under the condition that DH of HV2 was 0.05 m (HV2_DH0.05). The effect of FL was evaluated in three cases where the fire sources were located in the center of the floor (F LC), below HV1 (F L1), and below HV2 (F L2). With respect to the DH effect, the total mass flow rate of the vent flow was slightly higher and temperature was slightly lower in the case of HV1_DH0.19 than that in the case of HV1_DH0.05. However, considering the error bars, the effect of DH in this numerical simulation condition was considered to be insignificant. Furthermore, bidirectional flow patterns appeared in HV1 and HV2 in both DH conditions. Meanwhile, with respect to the FL effect, a bidirectional flow dominated by the mass flow rate of outflow occurred in the HV where the fire source was located, and a unidirectional inflow dominated by the mass flow rate of inflow occurred in the HV where the fire source was not located. The total mass flow rates of FL1 and FL2 conditions were similar, which were higher than those of FLC condition. The temperature was higher in FLC than those in FL1 and FL2. This was due to the small mass flow rate through the HV in the FLC. Meanwhile, an increasing trend of the temperature with the rising measurement height from the floor was observed at most of the temperature measurement points. However, when the fire source was located below HV1 and HV2, as the height from the floor increased, the temperature decreased and the overall temperature was low at the temperature measurement points below the vent where the fire source was not located. This trend was attributed to the occurrence of a strong unidirectional inflow wherein a large volume of low-temperature air flowed into the enclosure from the HV where the fire source was not located.

Spatial Distribution Characteristics of Soil Salt Ions in Tumushuke City, Xinjiang

Concrete durability in saline soil areas is a global problem. Both SO42− and Cl− in saline soil seriously affect the durability of concrete and restrict the sustainable development of engineering construction. Soil samples were collected from Tumushuke city, Xinjiang, and the concentrations of SO42− and Cl− in the soil were measured. Classical statistics and geostatistics methods were combined to analyze the distribution characteristics of the soil salts. Additionally, the kriging interpolation method was used to draw a salt distribution map. The results showed that the average contents of SO42− and Cl− in the soil of this area were 7037.08 and 6018.94 mg/kg, respectively. SO42− exhibited moderate variability at depths of 30–60 and 60–100 cm in the soil and strong variability in the surface layer; Cl− exhibited strong variability at depths of 0–30, 30–60, and 60–100 cm in the soil. The SO42− and Cl− concentrations exhibited high spatial correlation and showed regular changes. The horizontal distribution patterns of “low in the south and high in the north” and “high in the east and low in the west” were observed. Regarding the vertical distribution, the profiles of the SO42− and Cl− contents in the soils primarily exhibited “surface aggregation” distribution characteristics. Therefore, according to the spatial distribution characteristics of SO42− and Cl−, local concrete engineering construction can adopt different anti-erosion measures to enhance the safety and durability of concrete structures.

Effect of some environmental factors on the occurrence and distribution of Polychaeta Namalycastis indica (Southern, 1921) in the intertidal region of Shatt Al-Arab River Basrah Iraq

The current study was conducted on N. indica in three stations for the period from December 2017 to November 2018 (Al-Sharsh, Al-Salhiya and Al-Dweab), as samples were collected monthly. Some environmental factors were calculated, such as water temperature. The lowest water temperature was 12 °C during January and the highest temperature was 33 °C during July, both in Al-Salhiya station. The lowest value of salinity was 0.5‰ reached in April and November in Al-Sharsh station, while reached highest value ‰ 39.3 were recorded during July for Al-Dweab station, the light transmittance values ranged between (63-18) cm, recorded during July and November for Al-Salhiya and Al-Sharsh stations, respectively. As for the values of dissolved oxygen, it ranged between (12.1-5.1) mg/liter during August and May in the two stations. Al- Salhiya and Al-Sharsh, respectively. As for the bottom sediments of all the stations, they were alluvial with few and different percentages of sand and clay. The study showed that the studied environmental factors have an impact on the distribution and spread of this species within the horizontal and vertical sections in the tidal zone. The total density and density were measured within the horizontal distribution pattern in each station and the monthly total density ranges were 592-32 individuals/m2. The density of the three species was calculated within the horizontal distribution after dividing the area into three sections for each station. The results of the study indicated that there were significant differences at the level of P&lt;0.05 for densities between the first and second different sections of N. indica, and there were significant differences between the first and third sections and between the second and third sections.

Differential Thermal Regimes of the Tarim and Sichuan Basins in China: Implications for Hydrocarbon Generation and Conservation

AbstractThe uncertainty surrounding the thermal regimes of the ultra‐deep strata in the Tarim and Sichuan basins, China, is unfavorable for further hydrocarbon exploration. This study summarizes and contrasts the present‐day and paleo heat flow, geothermal gradient and deep formation temperatures of the Tarim and Sichuan basins. The average heat flow of the Tarim and Sichuan basins are 42.5 ± 7.6 mW/m2 and 53.8 ± 7.6 mW/m2, respectively, reflecting the characteristics of ‘cold’ and ‘warm’ basins. The geothermal gradient with unified depths of 0–5,000 m, 0–6,000 m and 0–7,000 m in the Tarim Basin are 21.6 ± 2.9 °C/km, 20.5 ± 2.8 °C/km and 19.6 ± 2.8 °C/km, respectively, while the geothermal gradient with unified depths of 0–5,000 m, 0–6,000m and 0–7,000 m in the Sichuan Basin are 21.9 ± 2.3 °C/km, 22.1 ± 2.5 °C/km and 23.3 ± 2.4 °C/km, respectively. The differential change of the geothermal gradient between the Tarim and Sichuan basins with depth probably results from the rock thermal conductivity and heat production rate. The formation temperatures at depths of 6,000 m, 7,000 m, 8,000 m, 9,000 m and 10,000 m in the Tarim Basin are 80°C–190°C, 90°C–220°C, 100°C–230°C, 110°C–240°C and 120°C–250°C, respectively, while the formation temperatures at depths of 6,000 m, 7,000 m, 8,000 m and 9,000 m in the Sichuan Basin are 120°C–200°C, 140°C–210°C, 160°C–260°C and 180°C–280°C, respectively. The horizontal distribution pattern of the ultra‐deep formation temperatures in the Tarim and Sichuan basins is mainly affected by the basement relief, fault activity and hydrothermal upwelling. The thermal modeling revealed that the paleo‐heat flow in the interior of the Tarim Basin decreased since the early Cambrian with an early Permian abrupt peak, while that in the Sichuan Basin experienced three stages of steady state from Cambrian to early Permian, rapidly rising at the end of the early Permian and declining since the late Permian. The thermal regime of the Sichuan Basin was always higher than that of the Tarim Basin, which results in differential oil and gas generation and conservation in the ultra‐deep ancient strata. This study not only promotes theoretical development in the exploration of ultra‐deep geothermal fields, but also plays an important role in determining the maturation phase of the ultra‐deep source rocks and the occurrence state of hydrocarbons in the Tarim and Sichuan basins.

Spatial structure characteristics of plain ecological plantation in Tongzhou District, Beijing, China

Forest spatial structure (FSS) directly reflects resource competition and growth space distribution among different trees. The characteristics of FSS play an important role in mastering the growth status of ecological forest, formulating stand structure regulation measures, and improving forest quality and ecological services. In this study, seven plain ecological plantations including Pinus tabuliformis, Fraxinus chinensis, Salix matsudana, Populus tomentosa, Sophora japonica, Robinia pseudoacacia, and Salix babylonica in Tongzhou District, Beijing were selected as the research objects. The spatial structure characteristics of plain ecological plantations were evaluated by aggregation degree, angle index, neighborhood comparison, open degree, canopy index, competition index, edge benefit, and spatial structure comprehensive index. The horizontal distribution pattern of stand was well, with the aggregation degree of 0.32-1.41, the angle index of 0.4, and the neighborhood comparison mainly around 0.5. The vertical distribution pattern of stand was not well and needed to be improved, with the open degree of 0.19-0.52, most canopy indexes of about 0.7. The competition index presented a high competitive status with the all values of >50. Except the comprehensive evaluation index of R. pseudoacacia plantation presented in grade Ⅲ, the other six kinds of plain ecological plantations fell to grade Ⅱ, with low stand openness and low vitality. The comprehensive evaluation indices of FSS followed the order of R. pseudoacacia > S. babylonica > P. tabuliformis > S. matsudana > F. chinensis > S. japonica > P. tomentosa.