Influence Of Edaphic Factors Research Articles

The Influence of Edaphic Factors on DNA Damage and Repair in Wild Wheat Triticum dicoccoides Körn. (Poaceae, Triticeae).

A complex DNA repair network maintains genome integrity and genetic stability. In this study, the influence of edaphic factors on DNA damage and repair in wild wheat Triticum dicoccoides was addressed. Plants inhabiting two abutting microsites with dry terra rossa and humid basalt soils were studied. The relative expression level of seven genes involved in DNA repair pathways-RAD51, BRCA1, LigIV, KU70, MLH1, MSH2, and MRE11-was assessed using quantitative real-time PCR (qPCR). Immunolocalization of RAD51, LigIV, γH2AX, RNA Polymerase II, and DNA-RNA hybrid [S9.6] (R-loops) in somatic interphase nuclei and metaphase chromosomes was carried out in parallel. The results showed a lower expression level of genes involved in DNA repair and a higher number of DNA double-strand breaks (DSBs) in interphase nuclei in plants growing in terra rossa soil compared with plants in basalt soil. Further, the number of DSBs and R-loops in metaphase chromosomes was also greater in plants growing on terra rossa soil. Finally, RAD51 and LigIV foci on chromosomes indicate ongoing DSB repair during the M-phase via the Homologous Recombination and Non-Homologous End Joining pathways. Together, these results show the impact of edaphic factors on DNA damage and repair in the wheat genome adapted to contrasting environments.

Alhagi sparsifolia Harbors a Different Root-Associated Mycobiome during Different Development Stages.

The mycobiome in the rhizosphere and within the roots benefits the nutrition and function of host plants. However, compared with the bacterial community, root-associated mycobiomes of desert plants and the forces that drive their assemblage are limited. Here, we investigated the mycobiomes in bulk soil, rhizosphere, and root compartments of Alhagi sparsifolia Shap., a phreatophyte species dominating in Central Asia. The internal transcribed spacer (ITS) gene phylogenetic profiles displayed significantly diverse mycobiomes across three compartments and host growth times, together explaining 31.45% of the variation in the community composition. The community structure of the perennial stage was markedly different from that of other stages (30 days to 2 years old). Along the soil-plant continuum, the α-diversity (estimated by Chao1) decreased gradually, while concomitantly increasing the community dissimilarity and the influence of edaphic factors. Specific leaf area, soil water content, and soil organic matter levels were common factors driving the composition of the three mycobiome communities. A more complex and connected network was observed in the root community compared with the other compartments. Overall, our work suggests that an age-sensitive host effect restructured the desert-plant-root-associated mycobiome, and that edaphic factors and host growth strategy may play potential roles in this process.

The influence of edaphic factors on the vital state of large-flowered magnolia (<i>Magnolia grandiflora</i> L.). in the Nikitsky Botanical Gardens

The most widespread magnolia on the Southern coast of the Crimea and, in particular, in the Arboretum of the Nikitsky Botanical Gardens is the evergreen Magnolia grandiflora L., introduced in 1817. Currently, 28 generative specimens of Magnolia grandiflora of different ages grow in the Arboretum, including garden forms with different vital state. There are very few data on the relation of this species to soil conditions. For this reason, we have studied the influence of edaphic factors on the vital state of Magnolia grandiflora growing in the Arboretum of the Nikitsky Botanical Gardens. A number of limiting edaphic factors have been identified, the main of which is the high skeletal structure of the soil. The humus reserves in the soil have a positive effect on the vital state of trees. A high level of agricultural technology is the main method of improving the vital state of Magnolia grandiflora .

Influence of edaphic factors on the structure and distribution of plant species in and around Mekeiman Marsh Wetland, Northeast of Algeria

Abstract. Touarfia M, Bouali N, Djouamaa Ak, Maazi MC, Houhamdi M. 2021. Influence of edaphic factors on the structure and distribution of plant species in and around Mekeiman Marsh Wetland, Northeast of Algeria. Biodiversitas 22: 3219-3228. Understanding the environmental factors that influence plant species composition and distribution is essential for successful management of biodiversity. Hence, the purpose of the present study was to assess plant species composition and distribution in a freshwater wetland Mekeiman Marsh, Northeastern Algeria and to analyze the influence of environmental factors on local plant species. To explore the distribution of plant species in this Marsh and analyze their associations with edaphic soil factors, the mapping and types of plant species in this area were analyzed by MapInfo and principal component analysis (PCA) ordination. For this purpose, four stations were chosen according to a stratified sampling method and phytosociological surveys were carried out in 12 plots, which were sampled using the Braun- Blanquet method. Multivariate analyses were used to determine the relationship between plant species distribution and edaphic factors. The R i386 (version 4.0.3) software was used for data analysis. We have identified 48 plant species belonging to 21 families. Results of biological types in the study area revealed the dominance of hemicryptophytes and therophytes, which indicates the presence of therophytization in this Marsh. Spatial distribution maps showed that plant species were divided into two categories viz. sparse and scattered plants according to the humidity gradient. The most important edaphic factors associated with plant species in Mekeiman Marsh were Sodium, Phosphorus, active limestone, Magnesium, clay, organic matter, C/N and Azot. By combining mapping and influence of edaphic factors on the structure and distribution of plant species in this wetland, it was known that the plant assemblages of this Marsh make disproportionately important contributions to wetland-level diversity. By combining mapping and influence of edaphic factors on the structure and distribution of plant species in this wetland, the plant assemblages of this Marsh make disproportionately important contributions to wetland-level diversity.

Benthic biocoenosis: influence of edaphic factors in the tropical mangroves of Cochin, Southern India

Biocoenosis of macrobenthic communities in relation to environmental and mangrove flora was studied in mangrove ecosystem of Cochin backwaters during 2010–2012 period. A total of 48 species in 45 genera belonging to 38 families of macrobenthos were collected with a mean numerical density of 1628 ± 2283 ind m−2. Malacostraca was the dominant taxa in terms of benthic density (55%) and diversity with 17 spp., then polychaeta (11 spp.), mollusca (9 spp.) and others (9 spp.). The dominant species were amphipods Idunella sp. (40,170 ind m−2), Cheiriphotis geniculata (34,169 ind m−2), polychaete Dendronereis aestuarina (38,808 ind m−2), tanaid Ctenapseudes chilkensis (29,419 ind m−2), bivalve Indosphenia kayalum (23,835 ind m−2) and oligochaete Tubificoides psuedogaster (16,946 ind m−2). The PCA and redundancy analysis revealed that the nature of the substratum determined by sediment texture, organic matter, total organic carbon, sediment nutrients were found to be an influencing factor in the differential distribution and community structure of macrobenthic organisms in mangroves of Cochin. Mangrove plant density also exhibited significant correlation with the density of macrofauna. This study has noted a decline in species composition as well as diversity and richness of macrobenthic fauna compared to the previous study notably polychaetes reported in 1993 in Cochin mangroves. Moreover, community structure exhibited significant change with newer associations of species especially opportunistic oligochaetes, corophiids and tanaids that are tolerant of various anthropogenic stressors. This change in community assemblage and biodiversity, thus demanding efficient management strategies for mangrove ecosystem through integrated planning, rehabilitation and periodic benthic faunal surveillance coupled with mangrove floral assessment.

Vegetation classification of the Margalla foothills, Islamabad under the influence of edaphic factors and anthropogenic activities using modern ecological tools

Vegetation classification of the Margalla foothills, Islamabad under the influence of edaphic factors and anthropogenic activities using modern ecological tools

Contrasting responses of above- and below-ground herbivore communities along elevation

Above- and below-ground herbivory are key ecosystem processes that can be substantially altered by environmental changes. However, direct comparisons of the coupled variations of above- and below-ground herbivore communities along elevation gradients remain sparse. Here, we studied the variation in assemblages of two dominant groups of herbivores, namely, aboveground orthoptera and belowground nematodes, in grasslands along six elevation gradients in the Swiss Alps. By examining variations of community properties of herbivores and their food plants along montane clines, we sought to determine whether the structure and functional properties of these taxonomic groups change with elevation. We found that orthoptera decreased in both species richness and abundance with elevation. In contrast with aboveground herbivores, the taxonomic richness and the total abundance of nematode did not covary with elevation. We further found a stronger shift in above- than below-ground functional properties along elevation, where the mandibular strength of orthoptera matched a shift in leaf toughness. Nematodes showed a weaker pattern of declined sedentary behavior and increased mobility with elevation. In contrast to the direct exposal of aboveground organisms to the surface climate, conditions may be buffered belowground, which together with the influence of edaphic factors on the biodiversity of soil biota, may explain the differences between elevational patterns of above- and below-ground communities. Our study emphasizes the necessity to consider both the above- and below-ground compartments to understand the impact of current and future climatic variation on ecosystems, from a functional perspective of species interactions.

Influence of edaphic factors along an altitudinal gradient on a litter arthropod community in an Abies-Quercus forest in Mexico

Elevational gradients can serve as natural experiments to study how species are restricted spatially according to environmental conditions. The variation in resources and conditions that habitats experience in relation to the seasons can be useful for understanding why the abundance and distribution of the species change temporarily. In this study, we evaluated the influence of an altitudinal gradient and seasonality on the composition, richness (S), diversity (Hʹ), and density of arthropod community associated with litter in a conserved Abies-Quercus forest in Central Mexico. We defined five altitudinal ranges in an altitudinal gradient that oscillated between 2570 and 2770 m, in which edaphic factors [pH, organic matter (OM), carbon (C), total nitrogen (N), total phosphorous (P), C/N, C/P, N/P ratios] and environmental temperature were characterized. Litter arthropods were collected through this vertical gradient in dry and rainy season. We identified 163 species belonging to 22 orders. Arthropods composition on each elevation zone is significantly different from one another in both seasons. The highest abundance and S values through altitudinal gradient were registered in the rainy season; in contrast, H’ values were higher during the dry season. We detected a significant negative effect related to the altitude on S, Hʹ and abundance of litter arthropods during the dry season and total data. An exception was the rainy season in which we did not detect any pattern. The community similarity reduces as altitude increases. Surprisingly, the intermediate altitudinal range showed the higher density values in the rainy season. On the other hand, OM, C/N and C/P ratios had a negative influence on litter community parameters analyzed in the rainy season and total data. In contrast, P shows a positive influence on S of litter arthropods in the same period. Edaphic characteristics recorded along the altitudinal gradient can explain differences in litter arthropod communities.

The influence of edaphic factors on bamboo population in Mount Baung Natural Tourist Park, Pasuruan, East Java, Indonesia

Sofiah S, Setiadi D, Widyatmoko D. 2018. The Influence of Edaphic Factors on Bamboo Population in Mount Baung Natural Tourist Park, Pasuruan, East Java. Trop Drylands 2: 12-17. There are 1250 bamboo species in the world, an estimated 161 of them are in Indonesia. Mount Baung Natural Tourist Park (MBNTP) is one of the bamboo forests located in a conservation area in East Java. The purpose of this research was to study the influence of edaphic factors on the growth of bamboo. This research was carried out from September 2011 to May 2012. The principal component analysis (PCA) was performed to determine the relationships between edaphic components and bamboo occurrences. Seven species of bamboo were found in MBNTP, namely, Bambusa blumeana, Bambusa vulgaris, Dendrocalamus asper, Schizostachyum iraten, Gigantochloa atter, Gigantochloa apus, and Dinochloa matmat. The edaphic factors affected the presence of bamboo in MBNTP. Phosphor (P) is one of the edaphic factors which contributes significantly to B. blumeana, B. vulgaris, D. asper and S. iraten presence in MBNTP. These bamboos grow in soil with high P levels of up to 27 ppm. The existence of G. apus was influenced by Manganese (Mn) and Sodium (Na) elements. This bamboo in this area was more commonly found in soil environments with low levels of Na (< 0.02 (cmol (+) kg-1)) and Mn (≤ 24 ppm). The species of bamboo with the densest population in Mount Baung, namely B. blumeana, was influenced by environment factor, i.e., the slope. Each bamboo has its own uniqueness in its growth. G. apus and G. atter populations were affected by solar radiation.

Vegetation structure and species composition variation of roadside slopes in Sichuan Basin, China

Sichuan Basin in southwestern China is a region of great conservation concern, yet little is known about the influence of edaphic factors on plant community dynamics of disturbed areas. We used multivariate analyses to identify differences in vegetation structure (i.e., tree, shrub, forb, and graminoid) and species composition between sandstone and shale substrates across 13 successional forest plant communities that varied in soil depth and soil texture. Vegetation structure did not differ between substrates (P >0.05), but plant community composition varied significantly (P = 0.0017). In addition, six indicator species were identified, including two native perennial grasses; namely, Imperata cylindrica for intermediate soil depths (20-30 cm) on sandstone substrate (P = 0.016) and Miscanthus sinensis for greater soil depths ( > 30 cm) on sandstone (P = 0.012) as well as on intermediate soil depths (20-30 cm) on shale substrate (P = 0.0002). Imperata cylindrica and M. sinensis were also the most dominant perennial grass species on sandstone (15.6 ± 5.3% cover) and shale (12.3 ± 4.9% cover), respectively. These patterns provide insights into species interactions and successional dynamics of roadside slopes, and offer guidance when choosing suitable species for future restoration projects in the Sichuan Basin.

Influence of edaphic factors on plant distribution and diversity in the arid area of Xinjiang, Northwest China

ABSTRACTThe influence of edaphic factors on plant distribution is essential to community ecology and important for vegetation restoration and management in arid ecosystems. In this study, desert plant distribution and diversity as well as soil water, salinity, and nutrients were measured in the Ebinur Lake Wetland Nature Reserve (ELWNR) in arid Northwest China. We determined relationships between plant distribution and soil factors along a transect with increasing distance from the river and created optimal models using soil factors to explain variations in plant diversity. In general, soil factors decreased with increasing distance from the river. Soil volumetric water content (SVWC), electrical conductivity (EC), pH, nitrogen (N), phosphorus (P), and sulfur (S) were closely related to plant distribution. According to canonical correspondence analysis, plants along the transect were divided into three groups: saline–alkaline tolerant, drought tolerant, and high P-demanding. SVWC, pH, soil organic carbon (C), N, P, and S account for 93.8% of the variations in plant diversity in the ELWNR. Compared with other soil factors, S explained the largest percentage of variations in diversity when single soil variables were considered in generalized additive models (R2 = 38.9%). Our results suggest increases in soil pH, P, N, and S would improve plant diversity significantly. We found differences among species groups in preference for habitat, and N and S content had a significant positive effect of on plant diversity, providing a scientific reference for plant restoration and saline soil remediation in desert ecosystems.

Effect of the edaphic factors and metal content in soil on the diversity of Trichoderma spp.

Influence of edaphic factors and metal content on diversity of Trichoderma species at 14 different soil sampling locations, on two depths, was examined. Forty-one Trichoderma isolates from 14 sampling sites were determined as nine species based on their internal transcribed spacer (ITS) sequences. Our results indicate that weakly alkaline soils are rich sources of Trichoderma strains. Also, higher contents of available K and P are connected with higher Trichoderma diversity. Increased metal content in soil was not inhibiting factor for Trichoderma species occurrence. Relationship between these factors was confirmed by locally weighted sequential smoothing (LOESS) nonparametric smoothing analysis. Trichoderma strain (Szeged Microbiology Collection (SZMC) 22669) from soil with concentrations of Cr and Ni above remediation values should be tested for its potential for bioremediation of these metals in polluted soils.

The Influence of edaphic factors on the level of some physiological parameters for Lycium shawii in Taba Protected Area, Egypt.

The aim of this article is assess the influence of environmental factors (especially edaphic) on the level of some physiological characteristics of plant communities in Taba Protected Area (Taba PA), South Sinai region. The Taba Protected Area (TPA) is one of Egypt's largest protected, about 2850 km2 (Lat. 29° 32´ N, Long. 34° 46´ E, Alt. 500 m a.s.l.),In International Protection Category III (In accordance with IUCN). Results showed that edaphic factors have an important role at variation in biochemical contents of plant communities within the selected wadis. The soils of study area, as desert soils (Arid soils), where soil properties vary over quite small distances, the causes of this variation due to some environmental factors such as gradient on the elevation, temperature, and rainfall between different locations..Four samples of Lycium shawii were collected from four studied locations. Evaluation of present methods used for analyzing the major biochemical contents (Soluble Carbohydrate, Water Soluble protein, Proline and Photosynthetic Pigments). Results were statistically analyzed by using One-way ANOVA and Post hoc-LSD tests (the least significant difference). In this study, prominent variation was recorded as regards the biochemical constituents of the plant among the different wadis.

Weed species composition and distribution pattern in the maize crop under the influence of edaphic factors and farming practices: A case study from Mardan, Pakistan

Weeds are unwanted plant species growing in ordinary environment. In nature there are a total of 8000 weed species out of which 250 are important for agriculture world. The present study was carried out on weed species composition and distribution pattern with special reference to edaphic factor and farming practices in maize crop of District Mardan during the months of August and September, 2014. Quadrates methods were used to assess weed species distribution in relation to edaphic factor and farming practices. Phytosociological attributes such as frequency, relative frequency, density, relative density and Importance Values were measured by placing 9 quadrates (1 × 1 m2) randomly in each field. Initial results showed that the study area has 29 diverse weed species belonging to 27 genera and 15 families distributed in 585 quadrats. Presence and absence data sheet of 29 weed species and 65 fields were analyzed through PC-ORD version 5. Cluster and Two Way Cluster Analyses initiated four different weed communities with significant indicator species and with respect to underlying environmental variables using data attribute plots. Canonical Correspondence Analyses (CCA) of CANOCO software version 4.5 was used to assess the environmental gradients of weed species. It is concluded that among all the edaphic factors the strongest variables were higher concentration of potassium, organic matter and sandy nature of soil. CCA plots of both weed species and sampled fields based on questionnaire data concluded the farming practices such as application of fertilizers, irrigation and chemical spray were the main factors in determination of weed communities.

Relation Between Edaphic Factors and Vegetation Development on Copper Mine Wastes: A Case Study From Bor (Serbia, SE Europe)

The relationship between edaphic characteristics and vegetation growing on mine wastes in the Bor region (East Serbia, SE Europe) was studied using multivariate statistical analysis. The influence of edaphic factors on the composition of plant life-forms was also investigated, since it could reflect strategies for the avoidance of or tolerance to disturbances of ecosystems. The goal was to provide potential models for the restoration and management of this and similar mine waste areas. The results of this study imply that soil textures, nitrogen contents, reclamation technology and the presence of hydrothermally altered andesite as the type of bedrock significantly influenced plant colonization and vegetation composition of the Bor mine wastes. These edaphic factors explained 30.3 % of the total variation in the vegetation data set. It was also revealed that the pattern of plant life-forms found on the considered site groups corresponded to the soil texture. Based on their relative abundance on the investigated sites and relationships with soil properties it is concluded that therophytes and geophytes are unsuccessful primary colonizers of the Bor mine wastes. Hemicryptophytes of psammophytic character were the most successful primary colonizers and therefore potential candidates for anthropogenically-assisted natural recovery. This study suggested that an assessment of edaphic factors should be widely used in the characterization of mine wastes prior to reclamation. Estimation of their role in the development of existing mine vegetation should predate reclamation procedures. Thus, approaches based on adequate plant life-forms should have a more prominent role in future mine reclamation schemes.

Comparison of Soil Physical and Chemical Properties in Grassland and Shrub Land Communities, Iran

Proper management of rangelands is based on ecological principles, and an understanding of ecological processes is a precondition of the right management. Composition and construction of each plant community are largely under the control and influence of edaphic factors, and these factors help to identify growing plants of their own region. Determination of the scientific relationship between soil factors and vegetation in each region and its expansion to other similar regions will be important achievements in the management of rangelands. The aim of the study was to compare the physical and chemical properties of soil in the two communities of shrub land and grassland. For this purpose, two sites of grassland and shrub land were selected in the rangeland of Vavsar Kiasar. Vavsar is located in longitude 45′′ 43′ 53°–35′′ 37′ 53° and in latitude 13′′ 10′ 36°–40′′ 5′ 36°. Climate was semi-arid to semi-humid and Mediterranean, using the Domartin method. Dominant plant species in the shrub land were Artemisia aucheri, Astragalus caspicus, Acantholimon bodeamun, and Stachys infelata, and species Festuca ovina, Stachys inflata, Noea mucronata, and Ephorbia cheiradenia were dominant in grassland. Sixty soil samples from each site were taken from two depths, 0–15 and 15–30 cm. In the laboratory, soil properties including organic carbon (OC), total nitrogen (TN), electrical conductivity (EC), calcium carbonate (CaCO3) percentage, moisture content, and percentages of clay, silt, and sand were measured. The comparison of mean soil properties was performed between the two communities and two depths by using the T-test. The results showed that there was a significant difference in the level of 5% among electrical conductivity, moisture content, and clay percentages at two depths of soil in the shrub-land site but there were no significant differences in soil factors between the two depths in the grassland site. There was a significant difference in the first depth of soil between shrub-land and grassland communities according to percentages of sand and silt, electrical conductivity, and CaCO3 and organic-matter percentages and in the second depth between the two communities for electrical conductivity, CaCO3 percentage, and clay percentage. In conclusion, soil condition in the shrub land was more desirable than in grassland because there was a greater percentage of vegetation and grazing intensity was less.

Influence of Edaphic Factors on Distribution of Mycorrhiza Associated with Medicinal Plants in Indian Central Himalayas

Influence of Edaphic Factors on Distribution of Mycorrhiza Associated with Medicinal Plants in Indian Central Himalayas

CARACTERÍSTICAS EDÁFICAS RELACIONADAS À PRODUÇÃO DE UM POVOAMENTO DE Araucaria angustifolia (Bert.) O. Kuntze

Este trabalho teve por objetivo estudar a influência dos fatores edáficos na produção de 12 procedências de Araucaria angustifolia (pinheiro-do-paraná) na Estação Experimental de Rio Negro da Universidade Federal do Paraná (UFPR). O experimento consiste em 36 parcelas de aproximadamente 550 m² cada, instaladas em blocos ao acaso, com 3 repetições para cada procedência. Foram feitas avaliações de diâmetro à altura do peito (DAP), altura dominante (Hdom), área basal (G/ha) e volume por hectare (V/ha) de 24 árvores distribuídas em todas as classes diamétricas, e analisados a profundidade e os atributos físicos e químicos de solo. Constatou-se que a diferença de produtividade está ligada aos fatores edáficos e não às procedências testadas. Assim, foi necessário agrupar as parcelas em classes homogêneas de solo, usando as ferramentas estatísticas multivariadas de análise de agrupamento e discriminante. Foram determinados cinco grupos de parcelas com classes semelhantes de solo, sendo que a variável “profundidade” apresentou o melhor valor discriminante. Analisando a relação entre os grupos de solos formados e os valores dendrométricos Hdom, G/ha e V/ha, pôde-se verificar que para Hdom não existiram diferenças significativas entre os grupos de solos, e que apenas um grupo apresentou valores significativamente inferiores aos demais para G/ha e V/ha. Dessa forma, constatou-se que, no experimento, há dois sítios distintos, e a profundidade maior ou menor que um metro de solo define em qual sítio cada parcela está contida. Palavras-chave: Solo; teste de procedências; sítio. Abstract Edaphic aspects related to the yield of an Araucaria angustifolia (Bert.) O. Kuntze stand. This work aimed at the study of the influence of edaphic factors on the yield of 12 different provenances of Araucaria angustifolia (parana-pine) at the Rio Negro Experimental Station – Federal University of Paraná (UFPR). The experiment consists of 36 plots of 550 sq.m. each, laid out in a randomized block design with three replicates by provenance, where the following data have been collected: d.b.h., dominant height (Hdom), soil depth, soil samples and volume of 24 trees distributed in all diameter classes. No significant differences were detected among plots, thus suggesting that edaphic factors have more influence on the productivity than genetic factors related to seed provenances. Multivariate analysis techniques were used to group plots according to soil chemical and physical characteristics. Five homogenous soil groups were defined and the variable “soil depth” presented the most discriminating power. An analysis of the relationship between soil groups and stand variables showed that, for dominant height, there were no differences between plots associated with different soil groups. For basal area and volume per hectare, only one group was considered different from the others. This fact led to the conclusion that there are two different sites in the experimental area, defined by soil depths lower or higher than 1 meter, respectively.Keywords: Soils; provenance test; site.

Influence of Edaphic Factors on the Mineralization of Neem Oil Coated Urea in Four Indian Soils

The utility of neem (Azadirachta indica A Juss) oil coated urea as a value-added nitrogenous fertilizer has been now widely accepted by Indian farmers and the fertilizer industry. In the present study, the expeller grade (EG) and hexane-extracted (HE) neem oils, the two most common commercial grades, were used to prepare neem oil coated urea (NOCU) of various oil doses, for which mineralization rates were assessed in four soils at three incubation temperatures (20, 27, and 35 degrees C). Neem oil dose-dependent conservation of ammonium N was observed in NOCU treatments in all of the soils. However, a longer incubation period and a higher soil temperature caused depletion of ammonium N. Overall, the nitrification in NOCU treatment averaged 56.6% against 77.3% for prilled urea in four soils. NOCU prepared from EG neem oil was consistently superior to that derived from hexane-extracted oil. The performance of NOCUs was best in coarse-textured soil and poorest in sodic soil. The nitrification rate (NR) of the NOCUs in the soils followed the order sodic > fine-textured > medium-textured > coarse-textured. The influence of edaphic factors on NR of NOCUs has been highlighted. The utility of the present study in predicting the performance of NOCU in diverse Indian soils was highlighted through the use of algorithms for computation of the optimum neem oil dose that would cause maximum inhibition of nitrification in any soil.

Chemical polymorphism of populations of Thymus caespititius grown on the islands Corvo, Flores, São Miguel and Terceira (Azores) and on Madeira, assessed by analysis of their essential oils

The composition of the essential oils isolated from 24 populations of Thymus caespititius collected on Corvo, Flores, São Miguel and Terceira (Azores) and on Madeira were studied by GC and GC–MS. All the oil samples analysed were dominated by their monoterpene fraction (66–89%). In the Azorean populations, the proportion of the oxygenated monoterpenes (51–79%) was higher than that of the monoterpene hydrocarbons (8–27%). In contrast, the monoterpene hydrocarbons and the oxygenated monoterpenes represented 35–44 and 42–43%, respectively, of the total oils from the populations grown on Madeira. Cluster analysis of the identified components with a concentration ≥1% grouped the oils into three main clusters that corresponded with their main components: carvacrol (41–65%), thymol (35–51%) and α-terpineol (33–37%). Although the populations collected on Madeira were grouped in the same cluster, the chiral analysis of sabinene, terpinen-4-ol and α-terpineol showed that there was a clear chemical polymorphism. Actually, in the oils from two populations (−)-sabinene, (−)-terpinen-4-ol and (+)-α-terpineol were the predominant enantiomers while in that from the third population an opposite ratio was found. The chemical polymorphism of the essential oils from T. caespititius may result either from the genetic variability of the populations or from the influence of edaphic factors.