Root Decay Research Articles

Partitioning Longleaf Pine Soil Respiration into Its Heterotrophic and Autotrophic Components through Root Exclusion

Rapid and accurate estimations of the heterotrophic and autotrophic components of total soil respiration (Rs) are important for calculating forest carbon budgets and for understanding carbon dynamics associated with natural and management-related disturbances. The objective of this study was to use deep (60 cm) root exclusion tubes and paired control (i.e., no root exclusion) collars to estimate heterotrophic respiration (Rh) and Rs, respectively, in three 26-year-old longleaf pine (Pinus palustris Mill.) stands in western Georgia. Root biomass was measured in root exclusion tubes and control collars after 102–104 days of incubation and fine root biomass loss from root exclusion was used to quantify root decay. Mean Rs from control collars was 3.3 micromol·CO2·m−2·s−1. Root exclusion tubes decreased Rs, providing an estimate of Rh. Mean Rh was 2.7 micromol·CO2·m−2·s−1 when uncorrected by pretreatment variation, root decay, or soil moisture compared to 2.1 micromol·CO2·m−2·s−1 when Rh was corrected for root decay. The corresponding ratio of Rh to Rs ranged from 66% to 82%, depending on the estimation method. This study provides an estimate of Rh in longleaf pine forests, and demonstrates the potential for deep root exclusion tubes to provide relatively rapid assessments (i.e., ~40 days post-treatment) of Rh in similar forests. The range in Rh to Rs is comparable to other reports for similar temperate coniferous ecosystems.

Establishment and early impact of the native biological control candidate Pyropteron chrysidiforme on the native weed Rumex obtusifolius in Europe

Rumex obtusifolius (Caryophyllales: Polygonaceae) is one of the most troublesome weeds in European grasslands and non-chemical control options are largely lacking. In this study, we assessed the potential of the native root-feeding specialist insect Pyropteron chrysidiforme (Lepidoptera: Sesiidae) for inundative biological control of R. obtusifolius. At multiple grassland sites, we applied P. chrysidiforme varying in developmental stage and level of protection onto R. obtusifolius to be examined in the subsequent autumn and spring. We consistently found the highest infestation resulting from the application of eggs (71 % of plants infested in autumn) with concomitantly elevated root decay and fewer rosettes compared to control plants. Moreover, in spring we found trends for associated decreases in biomass and number of shoots. Our findings support P. chrysidiforme as a promising biological control candidate of R. obtusifolius, but further investigations will be required to assess the consistency and long-term impacts of this novel approach.

Changes in the properties of Fijian Oxisols over 30 years of sugarcane cultivation

Sugarcane production plateaued in Fiji at ~4 million tonnes annually (average ~55 t/ha) during the latter part of the 1980s but, in recent years, despite the continuing release of high yielding varieties, the total production has decreased to under 3 million tonnes (average ~45 t/ha). This study was initiated to study the changes in the properties of Oxisols following sugarcane cultivation to ascertain whether yield declines were due to degradation of soil biophysical and chemical properties. The study lasted from 1978 (when the soils were first cleared for agriculture) to 2009. Soil (0–15, 30–40 and 70–80 cm) properties including pH, organic carbon, cation exchange capacity, water retention, bulk density, phosphate retention and exchangeable bases were monitored. The observed topsoil changes could generally be related to changes in organic matter and associated ion exchange properties. The major changes occurred in the first three years after clearing, but some changes continued for many years. Subsoil samples (30–40 cm) showed an increase in organic carbon after cane cultivation, probably due to soil mixing during land preparation, organic matter movement during cropping and decay of sugarcane roots. At 70–80 cm, small but significant increases in organic carbon were observed along with small decreases in pH. Overall, these changes indicate that careful management of topsoils is essential for maintaining soil fertility and hence sugarcane productivity on these highly weathered soils.

Cell wall compositional changes during incubation of plant roots measured by mid-infrared diffuse reflectance spectroscopy and fiber analysis

Plant roots, particularly the constituents of root cell walls (hemicellulose, cellulose and lignin) are important contributors to soil organic matter. Little is known about the cell wall composition of many important crop species or compositional changes as roots decay. The objectives of this study were to quantify changes in root cell wall composition during a four week laboratory incubation by forage fiber analysis and characterize those changes using diffuse reflectance infrared fourier transform spectroscopy (DRIFTS). The roots of six important crop, forage and native grass species were incubated at 25°C and sampled weekly. Alfalfa lost 78% of initial mass over four weeks, while the remaining species lost between 19% and 38%. For all species the majority of this loss occurred during Week 1, and only alfalfa mass loss was significant (P<0.05) each week. The trends observed for whole root decomposition were paralleled by the decomposability of root cell walls. Significant changes in hemicellulose, cellulose and lignin concentrations over time were only observed in alfalfa roots. Significant changes in decomposability of these constituents was likewise only observed in alfalfa, with cellulose the most decomposable fraction, followed by hemicellulose and lignin. Analysis by DRIFTS supported the fiber analysis results and revealed important changes in root cell wall composition. The disappearance of peaks due to starch in the perennial alfalfa and switchgrass roots following Week 1 helped to explain the greater initial mass loss in both of these species relative to the roots of the annuals. The spectral data also illustrated the resistance of alfalfa lignin to decomposition, the preservation of carbonyl compounds and the degradation of readily decomposed proteins. Finally, changes potentially indicative of wax compound preservation were found in the DRIFTS spectra of alfalfa even though the amount of wax was too small to quantify by fiber analysis. This research study reveals differences in the rate at which crop roots decompose and important changes that can occur in readily decomposable roots over relatively short time scales. These results provide valuable information contributing to the understanding and prediction of short term soil organic matter dynamics which will help to predict possible impact of management changes or soil disturbance on soil health and productivity as well as long term organic C stabilization and the potential for C sequestration.

The effect of gap openings on soil reinforcement in two conifer stands in northern Italy

Gap-oriented forestry is a subject that is gaining interest worldwide as a compromise between economic and operational requirements on the one hand and environmental and safety concerns on the other. In principle, the approach mimics the effects of fine-scale natural disturbance while avoiding the threats of soil degradation and instability associated with large clearcuts, but at the same time, it does not limit the productivity associated with single-tree selection.Despite this interest, studies of the real effects of gap-oriented forestry are still limited, particularly those dealing with its impact on slope stability. This paper provides quantitative results about the slope stability of two mixed-conifer stands subjected to gap management in the Italian Central Alps that were monitored for five years after felling.The results showed that root decay, both in strength and density, further reduces additional root cohesion by approximately 60% in the first two years after felling and by another 20% in the third year; it completely vanishes by the fifth year. The observed reduction in root reinforcement values has dramatic consequences for slope stability. In fact:–In undisturbed conditions, the contribution of forest root systems guarantees a very low probability of instability (approximately 10% for a factor of safety of less than 1 as well as for steep slopes and high levels of saturation).–After only two years, the probability of instability dramatically increases for gentle slopes and low levels of saturation. We estimated a 50% probability of a factor of safety less than 1 when steepness was greater than 36–38° and soil saturation was 25% and when steepness was greater than 24–26° and soil saturation was 75%.–The probability of instability is highest five years after felling when the contribution of the root system has vanished. The probability of failure exceeded 50% when steepness was greater than 25–28° and saturation was 25%, and the slopes were practically unstable when saturation was 75%.–At the point when the contribution of the root system to slope stability was null, the regeneration process was still too undeveloped to contribute to soil reinforcement in any way.These results suggest that although the gap-oriented approach is, in principle, more conservative than large clearcuts, the pace of natural regeneration could be slower than the process of root decay, so instability could occur, especially where local slopes exceed 25° and soils are frequently saturated.

Electronic cooling in Weyl and Dirac semimetals

Energy transfer from electrons to phonons is an important consideration in any Weyl or Dirac semimetal based application. In this work, we analytically calculate the cooling power of acoustic phonons, i.e. the energy relaxation rate of electrons which are interacting with acoustic phonons, for Weyl and Dirac semimetals in a variety of different situations. For cold Weyl or Dirac semimetals with the Fermi energy at the nodal points, we find the electronic temperature, $T_e$, decays in time as a power law. In the heavily doped regime, $T_e$ decays linearly in time far away from equilibrium. In a heavily doped system with short-range disorder we predict the cooling power of acoustic phonons is drastically increased because of an enhanced energy transfer between electrons and phonons. When an external magnetic field is applied to an undoped system, the cooling power is linear in magnetic field strength and $T_e$ has square root decay in time, independent of magnetic field strength over a range of values.

Wood Decay Fungi Associated with Tamarind Tree in Gujarat, India

Fungi may cause internal decay, cankers, loosening of tissue and cell walls result into weak forks in the trunk and large branches. Tree rot may be associated with root decay, damage to foliage and fruits. Wood decay fungi isolated from Tamarindus indica were Daldinia concentrica, Schizophyllum commune, Flavodon flavus,Irpex hydnoides, and Phellinus fastuosus, in which D. concentrica causing canker rot is reported for the first time from India and F. flavus and I. hydnoidesP. fastuosus are recorded for the first time on T. indica wood causing white rot. During canker rot, formation of bark canker and extensive internal decay of wood was observed; as a result the tree growing in the M.S. University campus became structurally unstable and broken off at the canker face. Early detection and removal of such hazardous branches of trees is advocated to avoid loss of life and property.

Wood Decay Fungi Associated with Tamarind Tree in Gujarat, India

Fungi may cause internal decay, cankers, loosening of tissue and cell walls result into weak forks in the trunk and large branches. Tree rot may be associated with root decay, damage to foliage and fruits. Wood decay fungi isolated from Tamarindus indica were Daldinia concentrica, Schizophyllum commune, Flavodon flavus,Irpex hydnoides, and Phellinus fastuosus, in which D. concentrica causing canker rot is reported for the first time from India and F. flavus and I. hydnoidesP. fastuosus are recorded for the first time on T. indica wood causing white rot. During canker rot, formation of bark canker and extensive internal decay of wood was observed; as a result the tree growing in the M.S. University campus became structurally unstable and broken off at the canker face. Early detection and removal of such hazardous branches of trees is advocated to avoid loss of life and property.

Effects of mixture of branch order-based roots and nitrogen addition on root decay in a subtropical pine plantation

Non-additive effects may occur when branching order-based fine roots decompose in mixture, due to their distinct chemical composition. However, these effects and how they respond to increased nitrogen (N) availability are poorly known. We conducted a 524-day field litterbag experiment to examine the potential non-additive effects of order-based fine root decomposition and their responses to different rates of N addition in a Pinus elliottii (slash pine) plantation in China. The intact fine roots of slash pine trees were hierarchically dissected and split into two groups (lower-order roots (the first and second order roots) and higher-order roots (the third to fifth order roots)). The decomposition of these two root groups was monitored either separately or in 1:1 mixture. The non-additive effects did not occur when the two root groups decomposed in mixture. However, high rate of N addition shifted the root group interactions from additive to synergistic effects through contrasting effects on individual root group (lower-order roots). High rate of N addition retarded the decomposition of lower-order roots more in isolation than in mixture, due to the decreased binding of acid-unhydrolyzable residue to inorganic N ions in mixture. Therefore, we suggest that although stoichiometric heterogeneity holds within the branching hierarchy of fine roots, the tight coupling of N with acid-unhydrolyzable residue of root tissues may limit N use by microdecomposers, and thereby causing the additive effect. Since the mixing effect of order-based root decomposition is affected by N addition, understanding the chemical heterogeneity within fine root systems and their linkage with ambient N availability during decomposition either in isolation or in mixture may facilitate the accurate prediction of root decomposition responses to N loading.

アカエゾマツ、トドマツ、カラマツの根の分解速度－リターバック法による分解試験１４年経過の結果－

アカエゾマツ、トドマツ、カラマツの根の分解速度－リターバック法による分解試験１４年経過の結果－

Differential responses of needle and branch order-based root decay to nitrogen addition: dominant effects of acid-unhydrolyzable residue and microbial enzymes

Both chemical differences between foliage and different orders of fine roots and their contrasting decomposing microenvironments may affect their decomposition. However, little is known about how foliage and branch order-based root decomposition responds to increased N availability and the response mechanisms behind. The effects of different doses of N addition on the decomposition of needles and order-based roots of Pinus elliottii (slash pine) were monitored using the litterbag method for 524 days in a subtropical slash pine plantation in south China. The acid-unhydrolyzable residue (AUR) concentration and microbial extracellular enzymatic activities (EEA) in decomposing needles and roots were also determined. Our results indicate that the responses of needle and order-based root decomposition were N-dose-specific. The decomposition of both needles and lower-order roots was inhibited under the high N dose rate. The retarded decomposition of lower-order roots could be explained more by the increased binding of AUR to inorganic N ions, while the retarded decomposition of needles could be explained more by the reduced microbial EEA. Further, in contrast to lower-order roots, N addition had no effect on the decomposition of higher-order roots. We conclude that the decomposition of foliage and fine roots may fail to mirror each other at ambient conditions or in response to N deposition due to their contrasting decomposition microenvironments and tissue chemistry. Given the differential effects of N addition on order-based roots, our findings highlight the need to consider the tissue chemistry heterogeneity within branching fine root systems when predicting the responses of root decomposition to N loading.

Quantification of soil biopore density after perennial fodder cropping

Plant root traits affect soil biopore (BP) formation. Aims of this study were to measure the effects of fodder crop species with contrasting root traits and duration of cropping on BP density (BPD), and also to address the consistency of these effects over different years focusing on the effects of root decay. Soil BPD was quantified after growing three perennial fodder crop species with contrasting root systems, namely, lucerne (Medicago sativa L.), chicory (Cichorium intybus L.) and tall fescue (Festuca arundinacea Schreb.) for 1, 2, and 3 years with 2 years fallow in two repeated field trials from 2007 to 2014. Total BPD after taprooted fodder crops (421 ± 14 m−1) was significantly higher compared with fibrous-rooted crops (337 ± 12 m−1). Cropping duration did not affect soil BPD. On average, density of medium-sized BP (BPmed; 2–5 mm) increased 14 % after 2 years of fallow, whereas BPD decreased by 5 % for coarse-sized BP (BPcor; >5 mm) after the fallow. Taprooted fodder crops enhanced BP formation into subsoil. Accurate assessment of biopores (BPs) and their persistence must take account of the temporal dynamics, including effects of root decay.

First Report of Fusarium Root Rot Caused by Fusarium oxysporum Infecting Pigmented Grapefruit Trees in Turkey

HomePlant DiseaseVol. 99, No. 4First Report of Fusarium Root Rot Caused by Fusarium oxysporum Infecting Pigmented Grapefruit Trees in Turkey PreviousNext DISEASE NOTES OPENOpen Access licenseFirst Report of Fusarium Root Rot Caused by Fusarium oxysporum Infecting Pigmented Grapefruit Trees in TurkeyF. Baysal-Gurel and A. CinarF. Baysal-GurelSearch for more papers by this author and A. CinarSearch for more papers by this authorAffiliationsAuthors and Affiliations F. Baysal-Gurel , Department of Plant Pathology, The Ohio State University, OARDC, Wooster 44691 A. Cinar , Department of Plant Protection, Faculty of Agriculture, Cukurova University, Balcali, Adana, Turkey 01330. Published Online:1 Apr 2015https://doi.org/10.1094/PDIS-07-14-0746-PDNAboutSections ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat Pigmented grapefruit trees (Citrus paradisi Macf. cvs. Star ruby and Rio red) grafted on sour orange (Citrus aurantium L.) exhibiting root rot symptoms have been observed in three orchards in Adana, Turkey, since 1996. Symptoms were decay of roots and aboveground parts (below the grafting point) without oozing gum and vascular discoloration. Infected trees showed reduced vigor and chlorosis on the foliage. The disease incidence was nearly 5 to 10% in each orchard. Nine diseased root parts from nine different plants were surface-sterilized with 1% NaClO for 2 min and cultured on Fusarium-selective medium (3) at 25°C for 1 week. The culture was transferred to potato dextrose agar (PDA) to determine cultural characteristics. Nine isolates consistently yielded white to purple aerial hyphae and produced abundant oval to ellipsoidal, unicellular microconidia (2.2 to 4.1 × 4.3 to 11.0 μm) borne in false heads on short monophialidic conidiophores, three-to-five-septate macroconidia with pedicellate bases (2.2 to 5.7 × 18.7 to 42.8 μm), and chlamydospores (2). To confirm pathogen identity, total DNA was extracted directly from fungal mycelium, using the PowerSoil DNA isolation kit (MO BIO Laboratories, Inc., Carlsbad, CA). The ribosomal DNA internal transcribed spacer (ITS) region was amplified by PCR using the primer pair ITS1 and ITS4 (4) and sequenced. The sequence, deposited in GenBank (Accerssion No. KP119604), was 99% identical to that of Fusarium oxysporum isolates from Spain (KC427029) and China (JN232163). Morphological and cultural characteristics and PCR confirmed the identity of the causal agent as F. oxysporum Schlechtend.:Fr. Ten 14-month-old Star ruby and Rio red plants, grafted on sour orange and transplanted into steam-sterilized potting mix, were drench-inoculated with a conidial suspension (1 × 106 conidia/ml and 50 ml/plant) of a selected isolate (CU2-97) harvested from a 7-day-old culture on PDA. Plants were maintained in a greenhouse from a low of 20°C at night to a high of 25°C during the day until symptoms appeared. Ten control plants from each pigmented grapefruit were drenched with sterilized water and maintained in the same greenhouse. Three months after inoculation, roots and aboveground parts below the grafting point of the grapefruit plants developed necrotic areas on all inoculated seedlings, and fungus was re-isolated from root parts. All control plants remained disease-free, and no fungus was re-isolated. F. oxysporum was reported infecting sweet orange and tangerines grafted on sour orange in Tunisia in 2014 (1). To our knowledge, this is the first report of Fusarium root rot caused by F. oxysporum infecting pigmented Star ruby and Rio red grapefruit grafted on sour orange in Turkey. This indicates that grapefruit trees grafted on sour orange could be at risk for infection of this potentially destructive disease in Turkey.

Abundance and dimensions of naturally occurring macropores along stream channels and the effects of artificially constructed large macropores on transient storage

AbstractMacropores are connected void spaces in the subsurface and can act as preferential flow paths for groundwater transport, but their dimensions and distribution patterns have not been well characterized in stream banks and hyporheic sediments. We ran field surveys in 5 streams of varying size, bed slope, and watershed land use in the Appalachian Mountains of southwestern Virginia. Natural surface-connected macropores were nearly ubiquitous. Macropores in this region arise by a variety of mechanisms, including soil piping, tree root decay, erosion around hardened structures, macroinvertebrate burrows, and invertebrate burrows. Macropore openings were slightly wider than tall, with median cross-sectional widths and heights of 3.5 cm and 3.0 cm, respectively. The median and maximum macropore lengths to first bend were 15.0 cm and 120.5 cm into the bank, respectively. True (tortuous) macropore lengths probably are often greater, and methods to map macropores are needed. Median interspacing of macropores...

Macrophyte root and rhizome decay: the impact of nutrient enrichment and the use of live versus dead tissue in decomposition studies

The decomposition of roots and rhizomes of two macrophytes, Eleocharis cellulosa and Typha domingensis, was studied in oligotrophic phosphorus (P) limited marshes of northern Belize. The experiment was conducted in long-term control and P enriched plots in five limestone-based inland marshes. Decomposition of naturally senescent root and rhizome litter was studied over 9 months using litterbags. Belowground litter was acquired by growing plants in unenriched (control) or P enriched marsh soils for 5 months. Plants were then allowed to naturally senesce using a split root design, which promoted nutrient retranslocation. The resulting senescent litter had 30 % higher C:P and 40 % lower P content than living roots and rhizomes. There were no differences in C:N among treatments or senescent versus live litter. Litterbags, filled with control or enriched root and rhizome litter, were buried in the upper 10–14 cm soil in the corresponding plot of each marsh. Differences in the rate of decay between species were greatest for rhizome tissue, with Typha decaying more than twice as fast as Eleocharis. For both species, however, tissue P enrichment had no effect on coarse root and rhizome decay. Enhanced root production from P enrichment, coupled with no change in decay, should lead to enhanced accretion over time. Additional tests, using litterbags filled with living roots and rhizomes, yielded dramatically different results between treatments compared to senescent tissue. Results from senescent belowground tissue also differed from shoot decomposition. Caution should be exercised when inferring belowground decomposition from live tissue and aboveground rates of decay.

First Report of Root Rot of Field Pea Caused by Aphanomyces euteiches in Alberta, Canada.

In recent years, root rots have severely impacted yields of field pea (Pisum sativum L.) in the Canadian province of Alberta. Above-normal precipitation levels in the springs of 2011 to 2013 led to the hypothesis that Aphanomyces euteiches Drechsler may play a role in root rot in water-saturated pea fields. To determine causal agent(s) of root rot, 145 pea fields were surveyed at flowering in July 2013 (1). Symptoms of root rot were abundant; the most prominent included red vascular streaking and dark brown rot of the tap root, indicative of Fusarium spp., but brown discoloration and cortical decay of lateral roots, indicative of A. euteiches, was also observed. Total genomic DNA was extracted from diseased root samples from each field, using the Qiagen DNeasy Plant kit, and amplified with species-specific primers for A. euteiches (2). Fusarium spp. were present in all fields, but seven fields located within a 200-km radius yielded a positive reaction for A. euteiches. Five fields were re-visited in May 2014 to collect soil for a bait test (3). Tests were performed using surface-sterilized pea seeds (cv. CDC Meadow) treated with Allegiance FL (Bayer, a.i. metalaxyl) at a rate of 110 ml/kg of seed. Five seeds per pot were planted into field soils in 10-cm pots with 12 replicate pots per field. Soils were irrigated as needed until the second-node stage and then kept at saturation for 14 days. Thirty day-old pea roots were evaluated for root rot symptoms; plated onto cornmeal agar amended with metalaxyl, benomyl, and vancomycin (MBV) without surface sterilization; and visualized microscopically for presence of oospores in the roots. Roots from three out of the five field soils showed symptoms typical of A. euteiches infection, including honey-brown discoloration, degradation of the root cortex, and presence of oospores. Root rot symptoms from the remaining fields were characteristic of Fusarium root rot, and oospores were not observed in roots. Fungal cultures with fast-growing, white, aerial mycelia characteristic of A. euteiches on MBV, were recovered from roots with Aphanomyces root rot symptoms, and transferred to PDA. To confirm pathogen identity, total DNA was extracted from 7-day-old cultures growing on PDA using the Qiagen DNeasy Plant Kit. The ribosomal DNA internal transcribed spacer (ITS) region was amplified using the primer pair ITS1 and ITS4 and sequenced (4). The sequences, deposited in GenBank with accession numbers KM486065, KM486066, and KM486067, were 100% identical to the ITS rDNA sequence of several isolates of A. euteiches using a BLASTn query. Fusarium spp. were also recovered from all root samples in the soil bait test. Total DNA extracted from roots was used in PCR assays with A. euteiches-specific primers as described above. PCR amplification of root DNA was successful only from the same three fields that showed Aphanomcyces root rot symptoms, further verifying presence of A. euteiches. The inability to detect or recover A. euteiches from two fields that had tested positive in the survey was likely due to patchy distribution of this pathogen and emphasizes the importance of rigorous soil collection methods to accurately detect pathogens. Although this is the first record of A. euteiches on field pea in Alberta, the distribution of A. euteiches within a 200-km radius in southern Alberta indicates that it has likely been present in soils for several years. The interaction between A. euteiches and Fusarium spp. infection in the root rot complex of field pea and their impact on field pea production in Alberta is currently being investigated.

Influence of shrub encroachment on CT-measured soil macropore characteristics in the Inner Mongolia grassland of northern China

The Inner Mongolia grassland of northern China is extensively affected by shrub encroachment. However, the influence of shrub encroachment on soil architecture is not well understood. The objective of this study was to quantify the architecture of soils beneath the shrub canopy and in the adjacent interspace grass area following the establishment of a shrub Caragana microphylla Lam. Study treatments were three transition states of C. microphylla that represent 1.32%, 12.96%, and 40.12% shrub densities and the grass patch as the control. A total of eighteen soil cores (0–50cm deep) were taken at the three sites with 3 replicates. At each site, three cores were from the shrub canopy and three from the grass patch, and cores were scanned with a GE HISPEED FX/I Medical Scanner. Numbers of macropores, macroporosity and macropore equivalent diameter within the 50cm soil profile were interpreted from X-ray computed tomography to analyze soil architecture. The results indicated that shrub encroachment significantly influenced soil macropores. Soils under shrub canopy had greater macroporosity, and developed deeper and longer macropores than those in the interspace grass. X-ray CT showed that macroporosity was 1.4–3.4 times greater in soil under C. microphylla L. than interspace grass. The intensity of shrub encroachment also had noticeable influences on soil macropore characteristics. Soil macroporosity decreased as shrub encroachment increased. In the grass patch, macropores were distributed mainly in the 0–200mm soil layer, while in the shrub patch, they were found throughout the 0–400mm soil layer. The large number of macropores found in soil under the shrub canopy can be attributed to greater root development and subsequent root decay. We speculate that a continual increase of anthropogenic disturbance would further lower the macroporosity of grasses, leading to an increase of surface flow and the decrease of infiltration, and macropore architecture could cause transport of water to the deeper soil layers in the shrub patches than in the grass patches.

Influence of organo-mineral fertilizers on the basis of the precipitation of sewage on micromycetes cenosis

One from actual problems of ecological safety of the modern industrial cities development is utilization of sewage. One of solutions of this problem is studying of possibility of use of ecologically safe organo-mineral fertilizers on the basis of a precipitation of city sewage. Therefore studying of influence of organo-mineral fertilizers on the basis of a precipitation of sewage (Dnipropetrovsk) in comparison with complex fertilizer ammophos on the number and specific structure of soil micromycetes was the purpose of researches. Field experiments were made on sites of 5 m2 in the following variants: control without fertilizers; introduction of ammophos and organo-mineral fertilizers on the basis of a precipitation of city sewage in number of 10 and 30 t/hectare. Experiments were made in triple frequency on fields of Erastovsky experimental station of Institute of agriculture of steppe zone NAAS of Ukraine (Pyatikhatsky area, Dnipropetrovsk region). The soil (chernozem usual) selected from depth of 0–10, 10–20 and 20–30 cm under crops of summer barley of a sort «Galaxies» in a phase of full maturing of seeds. Quantity of soil micromycetes considered on Capek agarized medium. Structure of soil microscopic fungi cenosis estimated using indicators of frequency of species occurrence, similarity of communities (Serensen coefficient), extents of species domination in cenosis (Berger-Parker index), specific wealth (Simson index) and a specific variety (Shannon index). In a layer of soil 0–10 cm of a site at introduction of 30 t/hectare of organo-mineral fertilizers on the basis of a precipitation of city sewage the quantity of microscopic fungi increased by 1.5 times in comparison with control. In the bottom layers (10–20 and 20-30 cm) – in 1.3 and 1.6 times –espectively. The increase in quantity of micromycetes is noted and in the soil of sites after introduction of 30 t/hectare of ammophos. In a layer of soil 0–10 cm their number increased by 2.3 times, and in the bottom layers – in 1.9 and 2.1 times respectively in comparison with control. From soils of a site of a field experiment are allocated and identified 13 species from 10 genuses of microscopic fungi. Soils of sites of various variants of experience differed on the frequency of occurrence of microscopic fungi. From the chernozem usual of control site are allocated 4 species of micromycetes. In micocenosis dominated Fusarium oxysporum with a frequency of occurrence 100 %, to subdominant species (frequency of occurrence 40 %) belonged F. solani. The least similar on the control was micocenosis of site at introduction of 30 t/hectare of ammophos. Micocenosis of soils in variants of experience at introduction of ammophos in number of 10 t/hectare and organo-mineral fertilizers from a precipitation of city sewage in number of 30 t/hectare were very close to control variant. In the soil of site at introduction of organo-mineral fertilizers from a precipitation of city sewage in number of 30 t/hectare 6 species of microscopic fungi are identified. In micocenosis dominated P. vinaceum (frequency of occurrence 80 %), Trichoderma viride (frequency of occurrence 40 %) belonged to subdominants. On the basis of determination of micromycetes frequency of occurrence, coefficient similarities of communities, indexes of domination, specific wealth and variety, it is proved that entering into the soil of organo-mineral fertilizers on the basis of a precipitation of sewage promotes to increase of specific variety of microscopic fungi. It is shown that use of organo-mineral fertilizers on the basis of a precipitation of sewage considerably reduces the frequency of occurrence of a phytopathogenic specie Fusarium oxysporum which is the activator of root decay at plants.

Factors contributing to tooth loss among the elderly: A cross sectional study

BackgroundThe present study evaluates the influence of several demographic, health, personal, and clinical factors on the number of missing teeth in old age sample. MethodsThe number of patients included was 259; they received a full mouth examination and answered a questionnaire provided by one examiner. All the variables related to teeth loss based on the literature were included. These variables focused on age, gender, race, marital status, clinical attachment level, pocket depth, year of smoking, number of cigarettes smoked per day, number of medications, root decay, coronal decay, health status, and year of education. Statistical analysis involved stepwise multivariate linear regression. ResultsTeeth loss was statistically associated with clinical attachment level (CAL)(p value 0.0001), pocket depth (PD) (0.0007) and education level (0.0048). When smoking was included in the model, age was significantly associated with teeth loss (0.0037). At least one of these four factors was also related to teeth loss in several specific groups such as diabetes mellitus, male, and White. The multiple linear regressions for all the proposed variables showed that they contributed to teeth loss by about 23%. ConclusionsIt can be concluded that less education or increased clinical attachment level loss may increase number of missing teeth. Additionally, age may cause teeth loss in the presence of smoking.

Soil phosphorus availability and soybean response to phosphorus starter fertilizer

Phosphorus fixation in tropical soils may decrease under no-till. In this case, P fertilizer could be surface-spread, which would improve farm operations by decreasing the time spend in reloading the planter with fertilizers. In the long term, less soluble P sources could be viable. In this experiment, the effect of surface-broadcast P fertilization with both soluble and reactive phosphates on soil P forms and availability to soybean was studied with or without fertilization with soluble P in the planting furrow in a long-term experiment in which soybean was grown in rotation with Ruzigrass (Brachiaria ruziziensis). No P or 80 kg ha-1 of P2O5 in the form of triple superphosphate or Arad reactive rock phosphate was applied on the surface of a soil with variable P fertilization history. Soil samples were taken to a depth of 60 cm and soil P was fractionated. Soybean was grown with 0, 30, and 60 kg ha-1 of P2O5 in the form of triple phosphate applied in the seed furrow. Both fertilizers applied increased available P in the uppermost soil layers and the moderately labile organic and inorganic forms of P in the soil profile, probably as result of root decay. Soybean responded to phosphates applied on the soil surface or in the seed furrow; however, application of soluble P in the seed furrow should not be discarded. In tropical soils with a history of P fertilization, soluble P sources may be substituted for natural reactive phosphates broadcast on the surface. The planting operation may be facilitated through reduction in the rate of P applied in the planting furrow in relation to the rates currently applied.