Soil Population Density Research Articles

NDVI Changes and Influencing Factors of Different Soil and Water Conservation Zones in Shandong Province

Exploring the characteristics of vegetation change and its influencing factors is essential to construct an ecological environment. Based on the NDVI dataset from 2000 to 2020, this study analyzed the spatial temporal attributes of NDVI changes in Shandong Province using the Sen trend analysis and the gravity center migration model. Furthermore, the spatial heterogeneity of NDVI and its influencing factors within the whole study area and different soil and water conservation zones were investigated using a Geo-detector model, considering population, hydrological, topographic, soil types, and vegetation types. The results were as follows： ① The NDVI in Shandong Province from 2000 to 2020 showed a fluctuating upward trend with significant seasonal characteristics that varied from different zones. The annual NDVI change showed a trend of single-peak in the Ⅲ-4-2t, Ⅲ-4-1xt, and Ⅲ-5-2w but showed a trend of double-peak in the Ⅲ-5-3fn. ② Regarding the spatial distribution, the NDVI was higher in the west-north and west-south areas and lower in the north and coastal areas. During the 21 years, the primary type of NDVI change was "medium-high coverage → high coverage," especially in the northeastern part of the soil conservation area of the Ⅲ-4-2t, the western part of the Ⅲ-4-1xt, and the ecological maintenance area of the Ⅲ-5-2w. Overall, 61.47% of the area had a positive trend of NDVI change with the gravity center of high coverage mitigating to the northeast, and the ecological environment was improved. ③ Soil types and population density were the dominant factors affecting NDVI in Shandong Province, with q values of 0.174 and 0.130, respectively. The chief factor in the Ⅲ-5-3fn, Ⅲ-4-2t, and Ⅲ-4-1xt was population density, with q values higher than 0.22, and the dominant factors in the Ⅲ-5-2w were soil types and vegetation types, with q values of 0.326 and 0.227, respectively. The interaction of the two factors enhanced the influence of the single factor, and the relationship between the influencing factors showed two-factor enhancement and nonlinear enhancement. The q-value of population density ∩ relative humidity was the highest, with a value of 0.257 in the Ⅲ-5-3fn. The q-value of population density ∩ soil types was the highest in the Ⅲ-4-2t and Ⅲ-4-1xt, reaching 0.297 and 0.378, respectively. The q-value of soil types ∩ vegetation types was the highest, with a value of 0.444 in the Ⅲ-5-2w. The results are expected to provide valuable references for improving the ecological environment of Shandong Province and lay a scientific foundation to make different conservation strategies for the individual soil and water conservation zones.

Relationship between Ecosystem-Services Trade-Offs and Supply–Demand Balance along a Precipitation Gradient: A Case Study in the Central Loess Plateau of China

Although the theory of ecosystem services (ESs) is important for guiding land-use planning, knowledge of ESs trade-offs and supply–demand mechanisms is still lacking, and the characteristics of the correlation between the size of trade-offs and the balance between supply and demand along the precipitation gradient have not yet been clarified. In order to supplement this area of knowledge of ESs, we selected 30 small watersheds in high-, medium- and low-precipitation areas as study units. A biophysical model and socio-economic data were used to calculate supply and demand for carbon sequestration, soil conservation and water yield. Redundancy analysis and regression analysis were used to study the ESs trade-offs, the supply–demand dynamics, and the characteristics of their correlation. The results were as follows. (1) The supply and balance between supply and demand of the three ESs, the trade-off between carbon sequestration and water yield and the trade-off between soil conservation and water yield trended downwards from the high-precipitation area to the medium-precipitation area to the low-precipitation area. (2) The primary factors influencing balance between supply and demand with regard to carbon sequestration in high-, medium- and low-precipitation areas were population density and soil organic-matter content, and the size of the conditional effects were greater than 53%. The dominant factor affecting the balance between supply and demand with regard to soil conservation in the three precipitation areas was slope gradient, and the conditional effect was greater than 40%. The most significant determinants of balance between supply and demand with regard to water yield in the three precipitation areas were grassland area, forest area and precipitation, and the conditional effects were greater than 22%. (3) The most significant determinants of the trade-off between carbon sequestration and water yield in high-, medium- and low-precipitation areas were forest, soil organic-matter content and population density, and the conditional effects were all greater than 45%; the primary factors affecting the trade-off between soil conservation and water yield in high-, medium- and low-precipitation areas were grassland and slope gradient, and the conditional effects were all greater than 24%. (4) The relationship between the balance between supply and demand and trade-off size often followed a quadratic function; the next-most-common relationship was a monotonous nonlinear response, and a linear response relationship was relatively rare. This study revealed the factors influencing balance between supply and demand and trade-offs with regard to ESs and the characteristics of their correlations in areas with different degrees of precipitation, which provided a new idea for the synchronous regulation of ESs in the context of conflicts and supply–demand imbalance.

Restoration of vegetation in the Yellow River Basin of Inner Mongolia is limited by geographic factors

Studying the relationships between vegetation cover and geography in the Mongolian region of the Yellow River Basin will help to optimize local vegetation recovery strategies and achieve harmonious human relations. Based on MOD13Q1 data, the spatial and temporal variations in fractional vegetation cover (FVC) in the Mongolian Yellow River Basin during 2000–2020 were investigated via trend and correlative analysis. The results are as follows: (1) From 2000 to 2020, the vegetation cover in the Mongolian section of the Yellow River Basin recovered well, the mean increase in the FVC was 0.001/a, the distribution of vegetation showed high coverage in the southeast and low coverage in the northwest, and 31.19% of the total area showed an extremely significant and significant increase in vegetation cover. (2) The explanatory power of each geographic factor significantly differed. Precipitation, soil type, air temperature, land use type and slope were the main driving factors influencing the spatial distribution of the vegetation cover, and for each factor, the explanatory power of its interaction with other factors was greater than that of the single factor. (3) The correlation coefficients between FVC and temperature and precipitation are mainly positive. The mean value of the FVC and its variation trend are characterized by differences in terrain and soil characteristics, population density and land use. Land use conversion can reflect the characteristics of human activities, and positive effects, such as returning farmland to forest and grassland and afforestation of unused land, promote the significant improvement of regional vegetation, while negative effects, such as urban expansion, inhibit the growth of vegetation.

Development of a Large-Scale Soil DNA Extraction Method for Molecular Quantification of Fusarium oxysporum f. sp. fragariae in Soil.

The most common soilborne diseases affecting the strawberry industry in California include Verticillium wilt due to Verticillium dahliae, charcoal root rot due to Macrophomina phaseolina, and Fusarium wilt due to Fusarium oxysporum f. sp. fragariae. Detection of these pathogens in soil is an important facet of disease management and fumigation recommendations. Whereas the soil populations of both M. phaseolina and V. dahliae can be readily quantified with quantitative PCR (qPCR) assays using DNA extractions with 500 mg of soil, the single-cell nature of the F. oxysporum chlamydospore does not provide enough pathogen DNA from 500-mg extractions to be reliably quantified. Here, we describe an improved DNA extraction protocol from 10 to 15 g of soil that allows for the quantification of F. oxysporum f. sp. fragariae populations below 10CFU/g. The relationship between results from the TaqMan qPCR assay and pathogen population density in soil was determined by using this extraction method in pathogen-free soils artificially infested with a hygromycin-resistant strain of F. oxysporum f. sp. fragariae to facilitate accurate colony counts when plated on a selective medium. Although the protocol was developed for F. oxysporum f. sp. fragariae, it is applicable for detection and quantification of other soilborne pathogens.

Cotton host resistance as a tool for managing Rotylenchulus reniformis in Louisiana.

The reniform nematode, Rotylenchulus reniformis, is a major yield-limiting pest of upland cotton (Gossypium hirsutum) in the United States that has been steadily increasing in incidence in many states. Reniform nematode-resistant cotton cultivars have recently become commercially available for cotton producers; however, few field trials have evaluated their efficacy as a nematode management tool. The aim of this study was to evaluate reniform nematode population development, plant growth, and seed cotton yield of reniform nematode-resistant cotton cultivars in two nematode-infested fields in Louisiana. Replicated small-plot field trials were conducted in St. Joseph, LA (NERS field) and Winnsboro, LA (MRRS field) during the 2022 and 2023 growing seasons. In 2022, cultivars evaluated included: (1) DP 1646 B2XF (susceptible/tolerant), (2) DP 2141NR B3XF (resistant), (3) PHY 332 W3FE (resistant), (4) PHY 411 W3FE (resistant), and (5) PHY 443 W3FE (resistant). In 2023, an additional susceptible cotton cultivar, PHY 340 W3FE, was also included. All nematode-resistant cotton cultivars evaluated provided suppression of reniform nematode population development relative to that of the susceptible cotton cultivars, with suppression of nematode soil population densities at harvest ranging from 49 - 81% relative to DP 1646 B2XF. The resistant cultivar PHY 411 W3FE provided the most consistent suppression of reniform nematode population development, reducing reniform nematode soil population densities at harvest in both field locations and both trial years. In contrast, DP 2141NR B3XF only reduced soil population densities at harvest in the NERS field in 2023. Despite relatively consistent nematode suppression and improvements in plant vigor ratings and canopy coverage associated with the resistant cotton cultivars, a yield increase was only observed with PHY 332 W3FE and PHY 411 W3FE planted at the NERS field in 2023. Despite strong resistance to reniform nematode in the evaluated cotton cultivars, nematode soil population densities still increased during the growing season in plots planted with resistant cotton cultivars, emphasizing the need for additional management tactics to use alongside host resistance. This study indicates that new reniform nematode-resistant cotton cultivars show promising potential to reduce nematode population development during the growing season in Louisiana.

As a Transitional Host, Weed Solanum nigrum L. Increases the Population Base of Root-Knot Nematode Meloidogyne enterolobii for the Next Season

The aim of this study was to determine the status of weed Solanum nigrum L. as a transitional host for Meloidogyne enterolobii and its effect on the population base of the nematodes in the next season. The nematode species infecting S. nigrum L. in a fallow field was identified by morphological identification and molecular diagnosis, and parasitic characteristics of the nematodes in S. nigrum L., including development of the nematode in S. nigrum L., the histopathological response of S. nigrum L. to M. enterolobii, and the host suitability of S. nigrum L., were studied. The M. enterolobii soil population density was evaluated before and after S. nigrum L. planting. Species identification revealed that it was M. enterolobii infection. Developmental observation indicated that juveniles of M. enterolobii developed fast in S. nigrum L., establishing feeding sites by 5 days after inoculation (DAI) and forming obvious egg masses on the root at 25 DAI. Histopathological observation showed the typical susceptible response of S. nigrum L., including giant cells with thick cell walls, uniformly dense cytoplasm, and less vacuolation, mainly inside the vascular cylinder. Host suitability assays suggested that S. nigrum L. is a good host for M. enterolobii with an average reproduction factor (RF) of 48.04 ± 14.71. Population densities assays revealed that S. nigrum L. increased the population density of M. enterolobii for two consecutive years from 0.48 ± 0.25 and 0.53 ± 0.31 J2/cm3 to 1.33 ± 0.16 and 1.56 ± 0.43 J2/cm3 of soil. These results indicated that M. enterolobii could reproduce well by infecting S. nigrum L. during the fallow season, and it increased the population base of M. enterolobii to the next season during vegetable production, which suggested a novel direction for the control of root-knot nematodes by controlling weeds as transitional hosts of M. enterolobii in the fallow season.

Sampling and Extraction of Plant Parasitic Nematodes.

The study of nematodes requires availability of nematode specimens and their population densities in plants and soil. This can be achieved using adequate sampling schemes and extraction methods. In this chapter, the most common and suitable sampling and extraction procedures and equipment are described. These include the use of Baermann's funnels, Cobb's decanting and sieving, floating methods such as the Oostenbrink method and Fenwick can, elutriators such as Seinhorst methods, centrifugation methods including that of Coolen, and mechanical and enzymatic maceration. The combination of different methods for cleaning the nematode suspensions is described, such as Cobb's sieving with Baermann's funnels or centrifugation, and for cysts combining Seinhorst's elutriator or Fenwick can with the alcohol methods. Methods for extraction of eggs and/or juveniles of cyst and egg mass forming nematodes, to be used as inoculum or to ascertain egg viability, are also described. Only little information is also noted on the use of molecular tools to identify and quantify nematode populations in soil and roots.

Effects of Soil Solarization and Grafting on Tomato Yield and Southern Root-knot Nematode Population Densities

High tunnel production has increased in the past 10 years in Kentucky with more than 1500 high tunnels constructed across the state. Tomato is the most popular and most valuable high tunnel crop per square foot. This has contributed to a lack of rotation and increased pressure from root-knot nematodes (RKN; Meloidogyne spp.). Infection by RKN leads to root galling and reduces the host plant’s ability to take up water and nutrients. Sustainable strategies are needed to manage increasing RKN populations for long-term health of high tunnel soils. Soil solarization is a nonchemical management strategy that has shown promise in other regions and in open field systems. Because tunnels are primarily used to produce high-value crops and are often used for season extension, solarizing during the off-season would be the most beneficial for growers because solarizing would require taking the tunnel out of production. The primary objective of this study was to determine whether springtime soil solarization in Kentucky high tunnels followed by use of resistant tomato cultivars is a viable and effective management strategy for RKN populations. Soil solarization was performed in two commercial high tunnels naturally infested with southern RKN (Meloidogyne incognita) for 2, 4, and 6 weeks and compared with a nonsolarized control. Soil temperatures reached during solarization were assessed at 7.6-, 15.2-, and 22.8-cm soil depth. After solarization, tomato was transplanted, including ‘Cherokee Carbon’ grafted onto RKN-resistant rootstocks ‘Fortamino’ and ‘Estamino’, RKN-resistant nongrafted ‘Caimon’, and susceptible ‘Cherokee Carbon’ as the control. The highest soil temperature achieved was 50 °C during 6 weeks of solarization at 7.6-cm soil depth compared with 38 °C reached in nonsolarized soil. Soil population densities of RKN increased each month after solarization and were generally lower after solarization with resistant tomato cultivars. The interaction of soil solarization and tomato cultivars was significant with respect to RKN densities in soil and roots. The mean RKN soil and root population densities in the nonsolarized, nonresistant treatment combination was significantly greater compared with all other treatments (P < 0.0001). Population densities of RKN were significantly higher in the nonsolarized control compared with solarized treatments (P = 0.0002). Nongrafted ‘Cherokee Carbon’ had significantly more RKN in surrounding soil compared with all other tomato treatments. Tomato yield was unaffected by soil solarization, but there were significant differences based on tomato cultivars alone; nongrafted ‘Cherokee Carbon’ yielded less than the resistant ‘Caimon’. Together, solarization and resistant cultivars reduced RKN population densities in soil and roots, which can provide growers with a nonchemical approach for long-term RKN management and high tunnel resiliency.

Managing Southern Root-knot Nematode in Kentucky High Tunnels Using Grafted Tomato

Infection by root-knot nematode (Meloidogyne spp.; RKN) leads to root galling and reduces the host plant’s ability to take up water and nutrients. Protected cropping systems, such as high tunnels, create conducive environments for RKN through increased soil temperatures and more intensive crop production. In Kentucky, high tunnel production has increased in the past 10 years, with tomato being the most cultivated high tunnel crop. This has contributed to a lack of rotation and increased pressure from RKN. Tomato grafting with RKN-resistant rootstock is a nonchemical management strategy that has shown promise in other regions of the United States. The primary objective of this 2-year, two-site study (Knox and Boyle Counties) was to determine whether using grafted resistant rootstock could be a viable management strategy in high tunnels naturally infested with Meloidogyne incognita. The rootstocks included ‘Arnold’, ‘Maxifort’, ‘Shin Cheong Gang’, and ‘Estamino’. ‘Primo Red’ and ‘Cherokee Purple’ were the scions and nongrafted controls in Knox and Boyle Counties, respectively. In 2020 and 2021 in Knox County, three of the four grafted treatments produced at least 38% higher yield than the nongrafted control. Grafted treatments had at least 44% fewer RKN eggs/g of dry root compared with the nongrafted control in both years. In 2021 and 2022 in Boyle County, tomato yield was at least five times greater in all four of the grafted treatments compared with the nongrafted control. In 2021, the nongrafted control had three times more RKN eggs/g dried root compared with three of the four grafted treatments. In 2022 in Boyle County, the nongrafted control had four times more RKN eggs/g of dried root than all grafted treatments. In both years and locations, ‘Arnold’ and ‘Estamino’ treatments had higher yield and lower RKN population densities in soil and roots compared with the nongrafted controls. Utilization of resistant rootstock will help Kentucky growers maintain crop productivity in soils infested with RKN, but should be combined with other management methods for long-term resiliency of the high tunnel system.

Identification of potentially contaminated areas of soil microplastic based on machine learning: A case study in Taihu Lake region, China

Soil microplastic (MP) pollution has recently become increasingly aggravated, with severe consequences being generated. Understanding the spatial distribution characteristics of soil MPs is an important prerequisite for protecting and controlling soil pollution. However, determining the spatial distribution of soil MPs through a large number of soil field sampling and laboratory test analyses is unrealistic. In this study, we compared the accuracy and applicability of different machine learning models for predicting the spatial distribution of soil MPs. The support vector machine regression model with radial basis function (RBF) as kernel function (SVR–RBF) has a high prediction accuracy (R2 = 0.8934). Among the six ensemble models, random forest (R2 = 0.9007) could better explain the significance of source and sink factors affecting the occurrence of soil MPs. Soil texture, population density, and MPs point of interest (MPs–POI) were the main source-sink factors affecting the occurrence of soil MPs. Furthermore, the accumulation of MPs in soil was significantly affected by human activity. The spatial distribution map of soil MP pollution in the study area was drawn based on the bivariate local Moran's I model of soil MP pollution and the normalized difference vegetation index (NDVI) variation trend. A total of 48.74 km2 of soil was in an area of serious MP pollution, mainly concentrated in urban soil. This study provides a hybrid framework that includes spatial distribution prediction of MPs, source-sink analysis, and pollution risk area identification, providing scientific and systematic methods and techniques for pollution management in other soil environments.

Resistance of the citrus rootstock forner-alcaide 5 to Tylenchulus semipenetrans in replant situations

The resistance of the citrus rootstock Forner-Alcaide 5 to Tylenchulus semipenetrans was assessed in comparison to the susceptible Carrizo citrange (S) in two replant situations. Changes in soil and root population densities were monitored after planting the new trees to detect tree infection and nematode population growth over time. The efficacy of pre-plant control methods such as fumigation with 1,3 Dichloropropene (1,3D) or 2-year fallowing was also assessed. Fumigation and fallowing reduced juveniles + males/250 cm3 soil to undetectable levels for 3 and 2 years, respectively, and postponed root parasitism on Forner-Alcaide 5 for 3 and 2.5 years, respectively. Forner-Alcaide 5 supported lower densities of juveniles + males/250 cm3 soil and females/g root than Carrizo citrange in both replant situations The efficacy of the resistant rootstock was enhanced when combined with 1,3D fumigation or 2-year fallowing because the pre-planting control reduced densities of juveniles + males in soil before establishing the orchard, and the resistant rootstock, the female densities in the roots. Selection for virulence within the field population did not occurr after 9-years of exposure of Forner-Alcaide 5 to the nematode. The durability of the resistance can be enhanced by combining rootstock resistance with pre-planting control methods in order to delay root parasitism, and therefore, diminish the selection pressure exerted on the resistant rootstock. Forner-Alcaide 5 exibited higher scion diameter and yield than Carrizo citrange.

Evaluation of fumigant and non-fumigant nematicides for management of Rotylenchulus reniformis on sweetpotato.

Reniform nematode (Rotylenchulus reniformis) is a major pest of sweetpotato in many production regions in Southern United States. Applying soil fumigants and non-fumigant nematicides are the primary management strategies available to growers. This study compared the relative efficacy of nematicides (1,3-dichloropropene, fluopyram, oxamyl, fluazaindolizine, aldicarb, Majestene, and fluensulfone) for management of reniform nematode on sweetpotato. Fumigating soil with 1,3-dichloropropene consistently reduced soil population densities of reniform nematode at the time of planting in both trial years (31 - 36% reduction relative to the untreated control); however, the duration of suppression varied greatly by growing season. A similar trend was observed with fluopyram (56 - 67% reduction) and aldicarb (63 - 65% reduction), which provided season-long suppression of reniform nematode population development in 2021 but had no impact in 2022. In 2021, nematicide application had no impact on yield; however, in 2022, oxamyl and aldicarb increased the yield of U.S.#1 grade sweetpotato. Overall, soil fumigation with 1,3-dichloropropene and in-furrow application of fluopyram and aldicarb provided the most consistent suppression of reniform nematode on sweetpotato.

Soil Census of Kentucky High Tunnels Reveals Statewide Distribution of Two Meloidogyne Species

High tunnels are passively heated and cooled structures used for specialty crop production that can increase marketable yields, extend the growing season, and protect crops from harsh weather. Kentucky has more than 1,500 high tunnels, and although there are many benefits, production still has several challenges. High soil temperatures, lack of rotation and sanitation, and intensive and continuous cropping make high tunnels hospitable environments for the root-knot nematode (RKN; Meloidogyne spp.). This plant parasite infects roots, causing chlorosis, wilting, stunting, and yield loss. Determining the presence, population density, and species of RKN is important to inform management strategies. To our knowledge, this is the first research aimed at determining the presence and distribution of RKN across Kentucky. From 2019 to 2022, we sampled the soil in 175 high tunnels in 62 counties. The characteristics of production system, soil type, crop rotation, and high tunnel age were collected to analyze with RKN presence, species, and soil population density. Of the soil samples collected, 45% had no presence of RKN. Among those samples where RKNs were observed, 55% were identified as M. incognita, 39% as M. hapla, and 4% as M. arenaria. RKN presence was dependent on production system and crop rotation, whereas RKN species was dependent on production system and soil type. With over half of the sampled high tunnels infested with RKN, this project justifies further research for management strategies for RKN, especially those that are sustainable species-specific options and appropriate for commercial high tunnels.

The research on spatial-temporal evolution and influence factors of urban resilience: A case study in the Guangzhou metropolitan area

Resilience city, a new concept of city sustainable development, becomes one of the important subjects of high-quality development research. Compared to the traditional urban disaster mitigation approach, resilient cities focus more on the organizational capacity and coordination within the urban systems. Taking Guangzhou metropolitan area as an instance, which is featured a highly developed economy and society and frequently happened hazards and disturbances, the paper constructs an evaluation index system from four city subsystems, including economy, society, ecology, and engineering. Meanwhile, by applying the methods of global entropy weight, variation coefficient, geographic information system, and obstacle degree model, the paper explores the time changes, space evolution, and obstacle degree factors of city resilience in the Guangzhou metropolitan area from 2010 to 2020. The research results show that: (1) There is a significant change in the time difference of city comprehensive resilience of the Guangzhou metropolitan area. The resilience of each city’s resilience subsystem has grown steadily, of which the development level of economic resilience, social resilience, and engineering resilience has been steadily improved, and ecology resilience level shows a slight decline among a steadily increasing. (2) The overall city resilience of the Guangzhou metropolitan area shows a radial pattern taking Guangzhou as the core, of which the city economy, society, and engineering resilience grades mainly show a medium and low resilience level, the ecology resilience mainly shows a medium and high resilience level, and the general performance of resilience space distribution level is high in the southeast and low in the northwest. (3) Social resilience and ecological resilience are the main driving subsystems in the early and late stages of city resilience development in Guangzhou metropolitan area during the research period, and engineering resilience is the main constraint subsystem. (4) Water and soil loss control area and population density are the main obstacle factors in the early and late stages of city resilience in the Guangzhou metropolitan area. The density of the city drainage pipeline and the total import and export volume are the basic resilience barrier factors. The paper analyzes the spatial-temporal pattern and influencing factors of city resilience in the metropolitan area from a multi-dimensional perspective, provides a new thinking and analysis framework for the management and sustainability of city resilience in the metropolitan area, and provides a reference for the coordinated development of the metropolitan area.

A Proposed New Species Complex within the Cosmopolitan Ring Nematode Criconema annuliferum (de Man, 1921) Micoletzky, 1925.

Ring nematodes are obligate ectoparasites on cultivated and wild herbaceous and woody plants, inhabiting many types of soil, but particularly sandy soils. This study explored the morphometrical and molecular diversity of ring nematodes resembling Criconema annuliferum in 222 soil samples from fruit crops in Spain, including almond, apricot, peach and plum, as well as populations from cultivated and wild olives, and common yew. Ring nematodes of the genus Criconema were detected in 12 samples from under Prunus spp. (5.5%), showing a low to moderate nematode soil densities in several localities from southeastern and northeastern Spain. The soil population densities of Criconema associated with Prunus spp. ranged from 1 nematode/500 cm3 of soil in apricot at Sástago (Zaragoza province) to 7950 and 42,491 nematodes/500 cm3 of soil in peach at Ricla and Calasparra (Murcia province), respectively. The integrative taxonomical analyses reveal the presence of two cryptic species identified using females, males (when available), and juveniles with detailed morphology, morphometry, and molecular markers (D2-D3, ITS, 18S, and COI), described herein as Criconema paraannuliferum sp. nov. and Criconema plesioannuliferum sp. nov. All molecular markers from each species were obtained from the same individuals, and these individuals were also used for morphological and morphometric analyses. Criconema paraannuliferum sp. nov. was found in a high soil density in two peach fields (7950 and 42,491 nematodes/500 cm3 of soil) showing the possibility of being pathogenic in some circumstances.

Evaluation of host-plant resistance and high residue rye for management of Meloidogyne incognita in cotton

The root-knot nematode Meloidogyne incognita (Mi) is the most important pathogen of cotton in the southeastern United States. Cotton cultivars with resistance to this nematode are commercially available; however, they have not been widely adopted by growers in fields infested with M. incognita. The objective of this study was to determine whether rotations of Mi-resistant (cv. PHY 487 WFR) and susceptible (cv. PHY 490 W3FE) cotton can be combined with high residue rye to provide a similar or better level of M. incognita suppression and cotton yield than continuous susceptible cotton with a nematicide (abamectin applied to the seed) or continuous resistant cotton. The experiment was a split-plot design with the cover-crop treatments of standard rye, high residue rye, and weedy fallow (main plots, eight replications each) and four management systems as the subplots. The management systems (subplots) were a resistant-susceptible (R–S) cotton rotation, a susceptible-resistant (S-R) rotation, continuous susceptible cotton plus nematicide, and continuous resistant cotton. The cover crop treatment had no effect on either root galling in cotton or soil population densities of M. incognita J2 at plant, mid-season and harvest. Root galling from M incognita was greater in the continuous susceptible cotton with abamectin (S–S) and in the susceptible sequence in the rotation (R–S) than in the resistant sequence (S-R) and the R-R treatments. Populations of M. incognita J2 were lower in the spring following a resistant cultivar but increased by mid-season in the susceptible sequence of the rotation (R–S) to levels numerically above those observed for the susceptible cultivar with abamectin. Contrary to our expectations, the nematode suppression provided by the resistant cultivar had no carry over benefit to the susceptible cultivar in terms of reducing damage from M. incognita or improving yield. The cotton cultivar used was only moderately resistant to the nematode; perhaps a cultivar with a higher level of resistance may have had a more of a carry-over effect. Moreover, unlike a previous study, planting high residue rye in the winter did not reduce populations of M. incognita.

Characterising social-ecological drivers of landuse/cover change in a complex transboundary basin using singular or ensemble machine learning

Studies have focused on understanding land use/cover (LULC) change through regression techniques. However, machine learning (ML) techniques and their ensembles may provide more accurate results. Accurate determination of drivers of LULC can guide reliable land use planning and effective natural resource management. In this study, we tested the utility of ML techniques and ensemble modelling to explain the social-ecological drivers of LULC in the Okavango basin. The Deep Neural Network (DNN) coupled with climate-based regionalization of the study area were used for LULC classification of the years 2002, 2013 and 2020. Centroids of 22 LULC transitions of the same period were used to separately calibrate five (5) machine algorithms (namely Random Forests (RF), Gradient Boost Models (GBM) and Maximum Entropy (MaxEnt), Classification Tree Analysis (CTA) and their ensemble. Model performance was evaluated using the Receiver Operating Characteristic (ROC) and the True skill statistic (TSS). Variable importance was used to assess the contribution of social-ecological variables to each LULC transition. Variables that were determined to be driving LULC were then used to predict future LULC using the Artificial Neural Network and Cellular Automata (ANN-CA). Analysis results show that average LULC classification accuracy for the study period (2002, 2013 and 2020) was (Bsh Koppen zone; OA = 95.03, Kappa = 0.94), (Cwa Koppen zone; OA = 95.29, Kappa = 0.94), Cwb Koppen zone; OA = 96.04, Kappa = 0.95). The ML ensemble performed better (ROC> 95, TSS >87) than singular ML models based on two separate model evaluation metrics. The Random Forest classifier outperformed other singular ML (ROC = 90.41, TSS = 84.2). Based on the top-performing ensemble model, distance from rivers, population density, annual average temperature, drought severity, fire frequency and distance from towns influence the conversion of natural to anthropogenic LULC classes (importance >0.5). On the other hand, distance from rivers, soil organic carbon, precipitation, GDP, elevation, population density and annual average temperature importantly influenced conversion from one natural LULC class to another natural LULC class. The study revealed that natural classes (wetland, shrubland, water and woodlands) will gradually decrease at the expense of anthropogenic classes (built-up and cultivated) in future (2040). Despite proposing the necessity of a basin-wide land-use plan to minimise pressure on resources and ensure sustainable use, findings in this study illustrate the benefit of ensemble modelling in understanding LULC dynamics in transboundary basins.

Kök Lezyon Nematodlarının (Pratylenchus thornei (Sher et Allen) Pratylenchus neglectus (Rensch) Filipjev & Schuurmans Stekhoven (Tylenchida: Pratylenchidae) ve Soğan-sak Nematodu Ditylenchus dipsaci (Kühn, 1857) (Tyleneida) 'nın Nohut Yetiştirme Alanlarında Dikey Dağılımı

Investigation of the vertical distribution of three plant-parasitic nematodes was conducted in two southeastern (Şanlıurfa) and central Anatolia (Ankara) Turkey chickpea fields during 2015/2016 and 2016/2017 growing season. Twelve accessions of wild Cicer species representing three Cicer species (Cicer reticulatum L. and C. echinospermum L.) were used in the experiments for it. Soil samples were collected around the plant roots at a 10-20 cm and 20-30 cm depth by using an auger at each site. Maximum population densities of the root-lesion nematodes (Pratylenchus thornei (Sher et Allen) and (Pratylenchus neglectus (Rensch) Filipjev & Schuurmans) were observed at the depth of 20-30 cm, pod filling stage, and harvest time on most sampling. Also, the population density of root-lesion nematodes at the depths of 20-30 cm was observed as higher than Ditylenchus dipsaci (Kühn, 1857) (Tylenchida: Anguinidae) in the chickpea field. Population density of root-lesion nematodes was positively correlated with the contents of depth, site, time sampling, species chickpea, and there was determined significant difference between soil depth and population density of nematodes in both sites statistically.

Biological Performance of Certain Bio-Agents, Fluopyram and Fosthiazate against Meloidogyne spp. on Guava Trees (Psidium guajava L.)

In this study, the potential of some bio-agents, fluopyram and fosthiazate were investigated against root-knot nematodes (Meloidogyne spp.) on guava trees under field conditions for two successive seasons (2020 & 2021). The examined bio-agents were; Bio-Nematon® (Paecilomyces lilacinus), Bio Cure-F® (Trichoderma viridi), Bio Cure-B® (Pseudomonas fluorescens) and BIOTECT® (Bacillus thuringiensis var. kurstaki). The infection parameters of root-knot nematodes (Meloidogyne spp.) were recorded at 35 and 70 days after treatment. Results indicated that all the applied treatments suppressed the soil population density (J2/250g soil) at range of 68.75 to 88.85% during the 1st season, and from 57.72 to 92.92% during the 2nd season. Besides, the numbers of root galls were decreased at range of 60.22 to 77.11% and from 57.90 to 70.90% during 1st and 2nd seasons, respectively. Also, the number of isolated eggs from roots was decreased at range of 67.13 to 94.61% and from 51.37 to 88.45% during 1st and 2nd seasons, respectively. However, the content of total N, P and K (%) in leaves of guava trees was fluctuated during both seasons.

Improving screening model of pesticide risk assessment in surface soils: Addressing regional specific human exposure risks and regulatory management

In this study, a simple screening approach was proposed to evaluate region-specific population health risks of soil pesticides, which was achieved by introducing region-specific factors of pesticides, including fate factors (FFs), environmental distribution factors (DFs), and intake factors (IFs). These region-specific factors were characterized using simple weather variables and calculated the characterization factors (CFs) to link pesticide emissions to population exposure risks. The CF at the reference state indicates the potential of a pesticide entering the human body. Simulations for over 700 pesticides showed that pesticides that are thermodynamically stable in soil organics have large CFs. In addition, we conducted a case study on the region-specific risk assessment of malathion in the United States. The results indicated that colder regions have larger CFs of malathion than those of the warmer regions due to the large FF values for the same emission rates. However, from a regulatory perspective, colder regions should have less strict malathion soil standards than those of warmer regions as children in colder regions spend limited time outdoors. Although other region-specific factors such as soil type and population density need to be considered to improve the model, the approach proposed in this study can be used as a simple screening tool to evaluate region-specific population health risks and manage soil residues for different regions.