Dry Months Research Articles

Impact of climate change on potential distribution of Dickeya zeae causal agent of stalk rot of maize in Sialkot district Pakistan

Maize (Zea mays) is an influential crop in its production across the world. However, the invasion of many phytopathogens greatly affects the maize crop yield at various hotspot areas. Of many diseases, bacterial stalk rot of maize caused by Dickeya zeae results in severe yield reduction, thus the need for efficient management is important. Further, to produce epidemiological information for control of disease outbreaks in the hot spot regions of Sialkot District, Punjab Pakistan, extensive field surveys during 2021 showed that out of 266 visited areas, the highest disease incidence ranging from 66.5 to 78.5% while the lowest incidence was ranging from 9 to 20%. The Maxent modeling revealed that among 19 environmental variables, four variables including temperature seasonality (bio-4), mean temperature of the wettest quarter (bio-8), annual precipitation (bio-12), and precipitation of driest month (bio-14) were significantly contributing to disease distribution in current and coming years. The study outcomes revealed that disease spread will likely increase across four tehsils of Sialkot over the years 2050 and 2070. Our findings will be helpful to policymakers and researchers in devising effective disease management strategies against bacterial stalk rot of maize outbreaks in Sialkot, Pakistan.

Predicting the Potential Distribution Areas of the Asian Redtail Catfi sh (Hemibagrus wyckioides Fang and Chaux, 1949) in the Chao Phraya River, Thailand, using Maximum Entropy Modelling

Hemibagrus wyckioides is recognized as an economically important freshwater fi sh in Thailand. However, there are no available comprehensive data regarding the geographic distribution and habitat suitability of H. wyckioides in Thailand. In addition, its natural population has tended to continuously decrease. This study aimed to predict the suitable distribution areas of H. wyckioides in the Chao Phraya River, Thailand, using the maximum entropy (MaxEnt) algorithm based on climatic factors, including 11 temperature and 8 precipitation indices from the WorldClim database. Model performance was evaluated by the area under the receiver operating characteristic curve (AUC). The jackknife test was used to assess the contribution of each variable to the model. The results revealed that the MaxEnt model performed acceptably well, with an AUC value of 0.939, representing excellent accuracy in predicting the appropriate distribution areas of H. wyckioides in the Chao Phraya River. The potential distribution areas of H. wyckioides were observed mostly along the Chao Phraya River in Sing Buri and Ang Thong Provinces. According to the results of the jackknife test, 11 climatic variables impacted the distribution of H. wyckioides. The annual mean temperature (BIO1), precipitation of driest month (BIO14), and annual temperature range (BIO7) were the most important infl uencing variables, with impact values of 53.5%, 15.9%, and 11.9%, respectively. Therefore, understanding the potential distribution areas can assist researchers in monitoring, management, and conservation activities or with the development of new natural protected areas of H. wyckioides in high-quality areas in the Chao Phraya River.

Spatial Study of Eel Larva Habitat in Ciletuh Bay Waters, Sukabumi Regency, West Java

Eels (Anguilla spp.) are highly nutritious fish that are widely consumed. Ciletuh Bay, situated opposite the Indian Ocean, is a natural habitat for eel larvae. The migration of eel larvae is influenced by various oceanographic factors, including salinity, sea surface temperature, and chlorophyll-a. In order to support fisheries activities in Sukabumi Regency, it is important to identify the optimal habitat for eel larvae and obtain information about their abundance. This study used remote sensing techniques and two algorithms, the Cilamaya Algorithm to estimate salinity and the Wibowo Algorithm to estimate chlorophyll-a. The study was conducted during the wet, dry, and transitional months of 2019 and 2020 in Ciletuh Bay. The potential areas for eel larvae were found to be concentrated at the mouth of the river during the wet month, at the estuary and the shore during the dry month and the first transitional month, and tended to spread during the second transitional month. The largest potential area was found during the dry month of 2019, covering an area of 3.44 km2, but the potential was more stable during the wet months.

Geospatial modelling of dry season habitats of the malaria vector, Anopheles funestus, in south-eastern Tanzania

BackgroundAnopheles funestus is a major malaria vector in Eastern and Southern Africa and is currently the dominant malaria-transmitting vector in many parts of Tanzania. Previous research has identified its preference for specific aquatic habitats, especially those that persist in dry months. This observation suggests the potential for targeted control through precise habitat mapping and characterization. In this study, we investigated the influence of habitat characteristics, land cover and human population densities on An. funestus distribution during dry seasons. Based on the results, we developed a habitat suitability model for this vector species in south-eastern Tanzania.MethodsEighteen villages in south-eastern Tanzania were surveyed during the dry season from September-December 2021. Water bodies were systematically inspected for mosquito larvae and characterized by their physico-chemical characteristics and surrounding environmental features. A generalized linear model was used to assess the presence of An. funestus larvae as a function of the physico-chemical characteristics, land use and human population densities. The results obtained from this model were used to generate spatially explicit predictions of habitat suitability in the study districts.ResultsOf the 1466 aquatic habitats surveyed, 440 were positive for An. funestus, with river streams having the highest positivity (74%; n = 322) followed by ground pools (15%; n = 67). The final model had an 83% accuracy in predicting positive An. funestus habitats, with the most important characteristics being permanent waters, clear waters with or without vegetation or movement and shading over the habitats. There was also a positive association of An. funestus presence with forested areas and a negative association with built-up areas. Human population densities had no influence on An. funestus distribution.ConclusionsThe results of this study underscore the crucial role of both the specific habitat characteristics and key environmental factors, notably land cover, in the distribution of An. funestus. In this study area, An. funestus predominantly inhabits river streams and ground pools, with a preference for clear, perennial waters with shading. The strong positive association with more pristine environments with tree covers and the negative association with built-up areas underscore the importance of ecological transitions in vector distribution and malaria transmission risk. Such spatially explicit predictions could enable more precise interventions, particularly larval source management, to accelerate malaria control.Graphical

Mapping Water Bodies and Wetlands from Multispectral and SAR Data for the Cross-Border River Basins of the Polish–Ukrainian Border

Using remote sensing data to accurately record water surface changes over large areas is crucial in monitoring water resources. However, mapping water surfaces from remote sensing data has its advantages and disadvantages. This study presents a method for mapping water surfaces and wetlands based on Sentinel-1/-2 data over a study area of more than 26,000 km2 in three river basins, the Bug, Dniester, and San, located along the Polish–Ukrainian border. To achieve this goal, an image processing algorithm with additional options was developed (special filters, type classification, and post-classification), which minimized the shortcomings and increased the accuracy of the method. As a result, by using optical and radar data, it was possible to create maps of water bodies in the study area in the driest month of the year from 2018 to 2021. The results were evaluated numerically and graphically. The accuracy of the method was assessed using the Kappa coefficient. For optical data, the lowest value was 76.28% and the highest was 88.65%; for radar data, these values were 87.61% and 97.18%, respectively. When assessing accuracy, the highest values were achieved for overall accuracy (OA), with a maximum of 0.95 (for SAR) and 0.91 (for optical data). The highest values were in user accuracy (UA), with a maximum value of 1 for both SAR and optical data.

The Atlantic forest is a potentially climatic suitable habitat for four Neotropical Myrtaceae species through time

Myrtaceae is one of the most species-rich botanical families and is a critical floristic component in regions with high diversity, such as the Atlantic Forest and Cerrado. In the Neotropical region, Myrteae is the main tribe of Myrtaceae and includes the most diverse genera Eugenia, Myrcia, Psidium, Myrceugenia, and Campomanesia. Here, we investigated the climatic suitability selected Myrteae species - Campomanesia guazumifolia, C. xanthocarpa, Eugenia pyriformis, and Psidium cattleyanum - across South America. This study spans the present day, three historical periods, and two future climate change scenarios. Our modeling analysis (ENSEMBLE) included environmental variables applied at the times evaluated. Our results suggest that temperature seasonality and precipitation in the driest month were the variables that most influenced climate suitability in the species. The Atlantic Forest lato sensu is a potentially climate suitable habitat for these four species over time, which matches the center of diversification and richness of Myrtaceae, in regions where they coexist and share habitats sympatrically. Historical glaciation events have influenced the retraction and expansion of species distribution, ultimately contributing to their current coexistence in select neotropical ecoregions. Our projections for the future indicate climate suitable habitats in areas similar to present models despite the different effects of climate change. The Atlantic Forest is the key to maintaining Myrteae biodiversity over time. Therefore, it is necessary to combine other approaches (e.g., evolutionary, ecological, and genetic studies) to deeply understand the evolutionary history of this region, its protection, and the maintenance of the biodiversity it harbors.

A long-term study on free-ranging jaguar-tick interactions, featuring a novel report of Amblyomma incisum adult infestation.

Over nearly 12 years, we collected ticks from free-ranging jaguars (Panthera onca) and performed statistical analyses to comprehend the vector-host relationship throughout the seasons. We evaluated the presence and number of ticks, as well as their association with weight, age, and gender of captured jaguars in the Pantanal and Amazon biomes. Out of 100 captured jaguars (comprising 72 initial captures and 28 recaptures, with 41 females and 31 males), 77 were found to be infested by different tick species. We gathered a total of 1,002 ticks, categorized by the following species in descending order of abundance: Amblyomma sculptum, Amblyomma ovale, Rhipicephalus microplus, Amblyomma triste, Amblyomma cajennense sensu stricto, Amblyomma incisum, and Amblyomma spp. larvae. Apart from weight, statistical analysis indicated that age, gender and seasonality does not significantly affect the presence of different tick species in free ranging jaguars. Notably, A. sculptum adults were more abundant in the first semester, while A. sculptum nymphs and Amblyomma spp. larvae were mainly found during dry months, aligning with their expected life cycle stages. This is the first long-term study in jaguars to correlate seasonality and host factors and also the first time an adult of A. incisum is reported infesting a jaguar.

Changes in inundation drive carbon dioxide and methane fluxes in a temperate wetland

Wetlands cycle carbon by being net sinks for carbon dioxide (CO2) and net sources of methane (CH4). Daily and seasonal temporal patterns, dissolved oxygen (DO) availability, inundation status (flooded or dry/partially flooded), water depth, and vegetation can affect the magnitude of carbon uptake or emissions, but the extent and interactive effects of these variables on carbon gas fluxes are poorly understood. We characterized the linkages between carbon fluxes and these environmental and temporal drivers at the Old Woman Creek National Estuarine Research Reserve (OWC), OH. We measured diurnal gas flux patterns in an upstream side channel (called the cove) using chamber measurements at six sites (three vegetated and three non-vegetated). We sampled hourly from 7 AM to 7 PM and monthly from July to October 2022. DO concentrations and water levels were measured monthly. Water inundation status had the most influential effect on carbon fluxes with flooded conditions supporting higher CH4 fluxes (0.39 μmol CH4 m−2 s−1; −1.23 μmol CO2 m−2 s−1) and drier conditions supporting higher CO2 fluxes (0.03 μmol CH4 m−2 s−1; 0.86 μmol CO2 m−2 s−1). When flooded, the wetland was a net CO2 sink; however, it became a source for both CH4 and CO2 when water levels were low. We compared chamber-based gas fluxes from the cove in flooded (July) and dry (August) months to fluxes measured with an eddy covariance tower whose footprint covers flooded portions of the wetland. The diurnal pattern of carbon fluxes at the tower did not vary with changing water levels but remained a CO2 sink and a CH4 source even when the cove where we performed the chamber measurements dried out. These results emphasize the role of inundation status on wetland carbon cycling and highlight the importance of fluctuating hydrologic patterns, especially hydrologic drawdowns, under changing climatic conditions.

Geographical distribution of two major quarantine fruit flies (Bactrocera minax Enderlein and Bactrocera dorsalis Hendel) in Sichuan Basin based on four SDMs.

Both Bactrocera minax and Bactrocera dorsalis are phytophagous insects, and their larvae are latent feeders, which cause great damage and economic losses to agriculture production and trade. This study aimed to provide a scientific reference for researching and developing the feasible countermeasures against these two pests. Based on the distribution data of B. minax and B. dorsalis in China, obtained from the Chinese herbaria, investigation and literature. Four niche models (Garp, Bioclim, Domain, and Maxent) were used to analyze the key environmental factors affecting the distribution of both pests and to build prediction models of the potential distribution in Sichuan Basin. Combined with two statistical standards, area under the receiver operating characteristic curve (AUC) and Kappa, the validity of prediction models were analyzed and compared. The results show that: the average AUC values of the four models are all above 0.90, and the average Kappa values are all above 0.75, indicating that the four models are suitable for predicting the potential distribution area of B. minax and B.dorsalis. The annual range of temperature, the mean temperature in the driest quarter, the mean temperature in the warmest quarter, the annual precipitation, and the precipitation in driest month are the key environmental factors affecting the distribution of B. minax, while the mean diurnal temperature range, the mean temperature in the driest quarter, the seasonal temperature variations and the precipitation in driest month affect the potential distribution of B. dorsalis. The suitable areas for B. minax are mainly concentrated in the eastern of Sichuan Basin, while the suitable areas for B. dorsalis are concentrated in the southeastern. Except for the Bioclim model, the highly-suitable area for both pests predicted by the other three models are all greater than 15.94 × 104 km2 and the moderately-suitable areas are greater than 13.57 × 104 km2. In conclusion, the suitable areas for both pests in Sichuan Basin are quite wide. Therefore, the relevant authorities should be given strengthened monitoring of both pests, especially in areas with high incursion rates.

Field infestation of the invasive fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae) on maize in Southern Ethiopia

The biggest obstacle to Ethiopia's maize production is the fall armyworm (FAW), Spodoptera frugiperda. Since its recent introduction, the pest has assumed a key pest status displacing most other stalk borer insects known to attack maize in the country. This study was carried out to assess the infestation of FAW on maize, identify associated natural enemies, and determined the geographic distribution of the pest in southern Ethiopia. Infestation by FAW was encountered in most surveyed areas. The earwig, Doru luteipes (Scudder) was frequently found preying on larvae of FAW while the larvae of Chrysoperla rufilabris (Burmeister) were observed feeding on FAW egg masses. Megaselia scalaris (Loew) and Palexorista zonata (Curran), two parasitoids of FAW, were recovered from FAW larvae. The entomopathogenic fungus, Beauveria bassiana, was isolated from the cadaver of FAW larvae. Modeling the distribution of FAW revealed that there are many suitable places in southern Ethiopia, with low-lying plain lands having the greatest potential for pest invasion. With AUC values above 0.9, the MaxEnt models demonstrated great prediction accuracy. Precipitation in the driest month (27.3%) and precipitation in the coldest quarter (25.4%), accounted for more than half of the variance in the pest's potential distribution. The findings of this study have contributed to a greater understanding of field infestation of FAW and associated natural enemies. The species distribution model result constituted a crucial point in providing the rationale for devising management strategy by taking into account a specified area susceptible to enhance invasion risk by FAW.

Characterising Rainwash Nutrient Fluxes and Soil Nutrients under Anacardium occidentale L. (Anacardiaceae) and Lowland Rainforest: implications for Ecosystem Management

This study aimed to ascertain the relationship between rainwash nutrient fluxes and soil nutrient properties under Anacardium occidentale L. (Anacardiaceae) and lowland rainforest for the purpose of sustainable ecosystem management. Both experimental and quasi experimental research designs were adopted. Samples from rainwash (for 12 months) and soil (from 0–15 cm and 15–30cm) were taken from 12 A. occidentale stands and 12 rainforests within 12 stratified quarters. Laboratory analyses of samples involved standard procedures, while data generated where statistically analysed. Results revealed that from A. occidentale and rainforest, fluxes of nutrients varied between throughfall (Tf) and stemflow (Sf), and between rainy season and dry season. The monthly nutrient fluxes by rainwash is such that Tf > Sf for both A. occidentale and native rainforest. The highest fluxes of nutrients by Tf occurred during dry months, with corresponding Sf fluxes were observed during rainy months. At 0.05 alpha levels, nutrient fluxes between Tf and Sf differed significantly; as well as between soil nutrient contents under A. occidentale and rainforest. Rainwash nutrients correlated positively and significantly with soil nutrients. Over time, A. occidentale add nutrients to soil through rainwash, therefore its cultivation is recommended for agro-forestry and sustainable ecosystem management.

Google earth engine for spatio-temporal drought monitoring in Bangkalan, Indonesia

Drought occurrence in a certain area can be monitored by remote sensing through cloud-based platform of Google Earth Engine (GEE). The objective this study was to analyze spatially and temporally distribution of drought in Bangkalan Regency between 2017 to 2022 with GEE. This study employed CHIRPS and satellite images of Landsat 8 at Level 2 covering Bangkalan area from 2017 to 2022. Masking and Cloud masking had been carried out before analyzed the satellite images. Data was processed using Java scrip API algorithm in GEE to obtain rainfall, LST, NDVI, NDWI and NDDI data. Result of rainfall analysis from CHIRPS data showed that dry months from 2017 to 2022 occurred from June to October. The value of LST was between 24.75 38.87°C. Drought events in the study area from 2017 to 2022 were dominated by severe and extreme drought. The severe drought covers the area of 83.17% (2017), 57.34% (2018), 67.13% (2019), 84% (2020), 80.93% (2021), and 89.89% (2022). Meanwhile, the extreme drought wraps the area of 14.05% (2017), 40.05% (2018), 30.17% (2019), 13.15% (2020), 16.27% (2021), and 7.03% (2022). The area with severe drought was always over the one with extreme drought, and when the severe drought area increased; the extreme drought area decreased Result of this study could be employed in planning of drought mitigation and adaptation, the use of water and land resources, and public information on risks and actions for drought-affected communities.

Urban Sustainability: Spatial distribution and ecological niche modelling of Brachytrupes membranaceus under climatic incidence in Kinshasa, DR. Congo

Species distribution modeling has become a very popular tool for anticipation and decision-making in biological resource conservation. This study aims to assess changes in the future distribution of Brachytrupes membranaceus habitats in Kinshasa between 2055 and 2100.\nThree variables contributed most to the model: rainfall in the driest month (38.4%), soil (28.9%) and rainfall in the coldest quarter (13.9%). Currently, 89.3% of Kinshasa\'s surface area is highly favorable to the development and conservation of B. membranaceus, compared with 69.5% and 47.5% in 2055 (optimistic and pessimistic scenarios respectively) and 61.5% and 39.2% in 2100 (optimistic and pessimistic scenarios respectively), mainly in the urban zone. From the current to the future climate, the areas potentially favorable to the development and conservation of B. membranaceus shift from the periphery to the urban center of Kinshasa (for all scenarios for the years 2055 and 2100).\nThis shows that threats to the development and conservation of B. membranaceus are mainly due to anthropogenic activities (anarchic construction and slash-and-burn agriculture) and less to climatic/environmental factors (rainfall and soil). These results contribute to Sustainable Development Goals 11 and 15 by 2030.

Influência do ciclo hidrológico sobre a abundância de desmídias em uma lagoa rasa de planície de inundação do semiárido brasileiro

Abstract Aim Knowledge of hydrological characteristics is essential for understanding ecological processes in floodplains, which can support sustainable management. We evaluated environmental variations in a shallow floodplain lagoon located in the Chapada Diamantina, Andaraí, Bahia. We aim to identify phases of the hydrologic cycle and their influence on desmid density, which is a group of algae known for its potential as bioindicator of trophic changes. Methods Bimonthly samplings were performed at four points in the lagoon. Abiotic (temperature, conductivity, pH, transparency, depth, dissolved oxygen, total and dissolved nutrients) and biotic (macrophyte cover, phytoplankton chlorophyll-a, and desmid density) variables were determined. The Trophic State Index (TSI) was calculated based on phytoplankton chlorophyll-a, and total phosphorus concentration. Results The lagoon was characterized by well-oxygenated, slightly acidic waters with low electrical conductivity. According to the TSI, the lagoon varied from mesotrophic to hypereutrophic during the study period. The driest months (August and October) were marked by high water transparency, low depth, nitrogen concentration, and macrophyte coverage. The highest value of accumulated precipitation was registered in December, when there was an increase in depth and a decrease in electrical conductivity and PT concentration. Two phases of the hydrologic cycle were evidenced and determined by the depth and nutrient concentrations. The highest abundance of desmids occurred at the end of the rainy season when the nutrient availability and pH were higher, and the depth was reduced. Conclusions Our results suggest that the flood pulse was the determining factor of the local environmental conditions and that, together with the macrophyte morphological traits, it influenced desmid abundance and distribution in a floodplain lagoon in the semiarid region.

Monitoring drought dynamics using remote sensing-based combined drought index in Ergene Basin, Türkiye

Abstract Remote sensing-based approaches have gained widespread usage in drought monitoring studies. However, relying on single-variable drought indices may be inadequate to provide a comprehensive understanding of drought dynamics. In this study, principal component analysis was employed to derive a combined index, namely, the combined drought index (CDI), from multiple indices such as vegetation condition index, temperature condition index, precipitation condition index, and soil moisture condition index. The CDI was subsequently employed to analyze drought occurrences in the Ergene Basin-Türkiye period from 2001 to 2020 (May to October) using MODIS data. Correlations were computed with standardized precipitation index (SPI) and standardized precipitation evapotranspiration index (SPEI) at 1-, 3-, and 6-month scales and crop yield. The results revealed that drought incidents transpired in the Ergene Basin for at least 1 month annually. May exhibited the wettest, while September stood as the driest month. The severity of drought and its spatial extent displayed an increasing trend followed by a subsequent decline during the aforementioned period. The CDI demonstrated stronger correlations with the 1-month standardized indices than the 3- and 6-month SPI-SPEI. A robust correlation of 0.79 was also observed between the CDI and the crop yield. In general, the CDI performed well in determining the spatial and temporal patterns of the historic droughts. As a result, the CDI could be leveraged to develop effective drought monitoring and management, which could help mitigate the negative impact of drought in the fragile environment of the Ergene Basin.

STUDI KESESUAIAN LAHAN POHON SERBAGUNA (MPTS) DI KELURAHAN LAYANA INDAH, KECAMATAN MANTIKULORE, KOTA PALU

This research was motivated by the aftermath of the land rehabilitation program with MPTS plants in the Mantikulore District by the Palu City Government. Closely related to efforts to determine land suitability classes for several types of MPTS in Layana Indah Village, Palu City. Land assessment, especially land suitability assessment, becomes important to prevent obstacles that may arise from limitations for plant growth, especially MPTS plants. The research was carried out for seven months, from April to September 2021, in Layana Indah Village, Mantikulore District, Palu City, Central Sulawesi. The field survey method was purposive sampling or carried out deliberately on other use areas in Palu City, Layana Village. Soil samples were taken from Wintu, representing Layana Village, another use area in the development of forest and land rehabilitation programs. In comparison, collecting climate data from the Meteorology and Geophysics Agency of Palu City. Land suitability assessment refers to the Atlas Format Procedure. Suitability indicators for several types of MPTS (durian, breadfruit, mango and jackfruit) are water availability, field slope, drainage, rock outcrops, and effective depth. The research in Layana Indah Sub-District shows the suitability of MPTS land with the limiting factor of dry months.

Present status, future trends, and control strategies of invasive alien plants in China affected by human activities and climate change

Invasive alien plants (IAPs) have serious environmental and economic impacts, especially in vulnerable areas of China. However, IAP richness distribution patterns, their driving factors, and the dynamic shifts in potential distribution areas remain elusive. We assessed IAP richness distribution patterns and drivers using 402 IAPs recorded in China at 88 926 occurrence points, and then predicted their potential distribution areas. The results show that IAP hotspots were mainly located in southeastern China, especially coastal areas of the South and East and large inland cities. Population density, gross domestic product (GDP), and four climate variables associated with precipitation and temperature jointly influenced the richness distribution pattern of all IAPs. Specifically, population density and GDP impacted the richness distribution pattern of narrow‐range IAPs, and population density, GDP, distance to the nearest national highway, and five climate variables affected the richness distribution pattern of widespread IAPs. Only GDP contributed significantly to the richness distribution pattern of the top 5% hotspot grid cells, whereas population density, GDP, and precipitation in the driest month (BIO14) significantly influenced the richness distribution patterns of hotspots for both the top 10% and top 20%. Prediction analysis demonstrated that southeastern China would have particularly high invasion risk under both current and future climate scenarios. Regions with increases in predicted species richness are more common (44.83–64.97%) than those with decreases, except under the Representative Concentration Pathway (RCP) 4.5 scenario. Climate change will contribute greatly to the expansion of potential IAP distribution areas under both optimistic (RCP 2.5) and pessimistic scenarios (RCP 8.5). The results of this study provide insights into the priority management of IAPs by developing promising strategies for the control and prevention of IAP invasion.

Peronosclerospora philippinensis (Philippine corn downy mildew): predicting plant disease emergence and distribution

Peronosclerospora philippinensis, or the Philippine corn downy mildew, is an obligate biotrophic pathogen of the Phylum Oomycota. The organism is tagged as the most destructive pathogen of maize worldwide, and recently, there have been a few reports on the re-occurrence of the pathogen from the past decade. Disease control and mitigation through chemical agents have been the current practice; however, it appears that the pathogen is influenced by environmental factors that drive re-emergence. Presented herein is an attempt to predict the potential geographical distribution of P. philippinensis in the Philippines. Two changing climate scenarios were generated, and data suggested a probable expansion of the pathogen to the Southern Tagalog region and some areas in the Visayas region, particularly on Negros Island. Further, the mean diurnal range for the current climate and precipitation in the driest month for the predicted scenarios appeared as the most contributory bioclimatic variables affecting distribution. Generated data suggest a call for a proactive response to the potential disease breakthrough of the Philippine corn downy mildew

Predicting the Distribution of the Invasive Species Atractosteus spatula, the Alligator Gar, in China

The Alligator Gar (Atractosteus spatula) is a very dangerous species that has an extremely destructive impact on the ecological environment in aquatic areas. As a kind of ornamental fish, it is spreading rapidly all over the world. In order to avoid or delay the spread of Alligator Gar in China, it is urgent to further monitor and clarify its distribution range within the country. In this study, a maximum entropy model (MaxEnt) and geographical information system (ArcGIS) were used to identify suitable regions under climate change scenarios in China, and the significance of environmental factors that shape this species’ distribution were evaluated. According to the geographical distribution data of Alligator Gar and selected environmental variables, the potential habitat area of Chinese Alligator Gar under four climate scenarios in the present (2000s) and future (2050s and 2070s) was predicted. (1) The main environmental variables affecting the potential geographical distribution of Alligator Gar are temperature factor variables (the mean temperature of the warmest quarter and the mean temperature of the coldest quarter), precipitation factor variables (precipitation in the driest month and in the driest quarter), and altitude. (2) Under the current climate conditions, the suitable breeding areas of Alligator Gar are mainly concentrated in the Guangxi Zhuang Autonomous Region, Guangdong Province, and Hainan Province. Under the four future climate scenarios, the distribution area of the total suitable area of Alligator Gar will gradually decrease, and the suitable area of Alligator Gar will spread to high latitudes.

Evaluation of the Vertical Profile of Radio Refractivity and its Gradients in a Tropical Atmosphere

This paper evaluates radio refractivity and its gradients over Abuja, the Federal Capital Territory of Nigeria, using five years upper air meteorological data obtained from the Nigerian Meteorological Agency (NiMet). From the results obtained, radio refractivity was observed to decrease with increasing altitude. Also, higher refractivity values were observed in wet season, while lower values were recorded in dry season. An average refractivity value of 326 N-Units was obtained at 1 km altitude, while average refractivity gradient values of -34 N-Units/km and -40 N-Units/km were recorded for the dry and wet season months respectively. A total average value of -38 N-Units/km for refractivity gradient was obtained for the five-year study period, thus making the atmospheric condition over Abuja to be sub-refractive. The effective earth radius factor (k-factor) computed for the location was also observed to be higher in the wet season months than the dry season months. An average k-factor value of 1.32 was obtained for the study period.