A comparative assessment of support vector regression,artificial neural networks,and random forests for predicting and mapping soil organic carbon stocks across an Afromontane landscape

Soil organic carbon (SOC) is a key indicator of ecosystem health, with a great potential to affect climate change. This study aimed to develop, evaluate, and compare the performance of support vector regression (SVR), artificial neural network (ANN), and random forest (RF) models in predicting and mapping SOC stocks in the Eastern Mau Forest Reserve, Kenya. Auxiliary data, including soil sampling, climatic, topographic, and remotely-sensed data were used for model calibration. The calibrated models were applied to create prediction maps of SOC stocks that were validated using independent testing data. The results showed that the models overestimated SOC stocks. Random forest model with a mean error (ME) of −6.5 Mg C ha⁻¹ had the highest tendency for overestimation, while SVR model with an ME of −4.4 Mg C ha⁻¹ had the lowest tendency. Support vector regression model also had the lowest root mean squared error (RMSE) and the highest R² values (14.9 Mg C ha⁻¹ and 0.6, respectively); hence, it was the best method to predict SOC stocks. Artificial neural network predictions followed closely with RMSE, ME, and R² values of 15.5, −4.7, and 0.6, respectively. The three prediction maps broadly depicted similar spatial patterns of SOC stocks, with an increasing gradient of SOC stocks from east to west. The highest stocks were on the forest-dominated western and north-western parts, while the lowest stocks were on the cropland-dominated eastern part. The most important variable for explaining the observed spatial patterns of SOC stocks was total nitrogen concentration. Based on the close performance of SVR and ANN models, we proposed that both models should be calibrated, and then the best result applied for spatial prediction of target soil properties in other contexts.     

Mapping soil organic matter in low-relief areas based on land surface diurnal temperature difference and a vegetation index

Accurate estimates of the spatial variability of soil organic matter (SOM) are necessary to properly evaluate soil fertility and soil carbon sequestration potential. In plains and gently undulating terrains, soil spatial variability is not closely related to relief, and thus digital soil mapping (DSM) methods based on soil–landscape relationships often fail in these areas. Therefore, different predictors are needed for DSM in the plains. Time-series remotely sensed data, including thermal imagery and vegetation indices provide possibilities for mapping SOM in such areas. Two low-relief agricultural areas (Peixian County, 28 km × 28 km and Jiangyan County, 38 km × 50 km) in northwest and middle Jiangsu Province, east China, were chosen as case study areas. Land surface diurnal temperature difference (DTD) extracted from moderate resolution imaging spectroradiometer (MODIS) land surface temperature (LST), and soil-adjusted vegetation index (SAVI) at the peak of growing season calculated from Landsat ETM+ image were used as predictors. Regression kriging (RK) with a mixed linear model fitted by residual maximum likelihood (REML) and residuals interpolated by simple kriging (SK) were used to model and map SOM spatial distribution; ordinary kriging (OK) was used as a baseline comparison. The root mean squared error, mean error and mean absolute error calculated from leave-one-out cross-validation were used to assess prediction accuracy. Results showed that the proposed covariates provided added value to the observations. SAVI aggregated to MODIS resolution was able to identify local highs and lows not apparent from the DTD imagery alone. Despite the apparent similarity of the two areas, the spatial structure of residuals from the linear mixed models were quite different; ranges on the order of 3 km in Jiangyan but 16 km in Peixian, and accuracy of best models differed by a factor of two (3.3 g/kg and 6.3 g/kg SOM, respectively). This suggests that time-series remotely sensed data can provide useful auxiliary variable for mapping SOM in low-relief agricultural areas, with three important cautions: (1) image dates must be carefully chosen; (2) vegetation indices should supplement diurnal temperature differences, (3) model structure must be calibrated for each area.     

Effects of water potential on mycelial growth,sclerotial production,and germination of Rhizoctonia solani from potato

The effects of osmotic and matric potential on mycelial growth, sclerotial production and germination of isolates of Rhizoctonia solani [anastomosis groups (AGs) 2-1 and 3] from potato were studied on potato dextrose agar (PDA) adjusted osmotically with sodium chloride, potassium chloride, glycerol, and matrically with polyethylene glycol (PEG) 6000. All isolates from AGs 2-1 and AG-3 exhibited fastest mycelial growth on unamended PDA (−0.4 MPa), and growth generally declined with decreasing osmotic and matric potentials. Growth ceased between −3.5 and −4.0 MPa on osmotically adjusted media, and at −2.0 MPa on matrically adjusted media, with slight differences between isolates and osmotica. Sclerotium yield declined with decreasing osmotic potential, and formation by AG 2-1 and AG-3 isolates ceased between −1.5 and −3.0 MPa and −2.5 and −3.5 MPa, respectively. On matrically adjusted media, sclerotial formation by AG 2-1 isolates ceased at −0.8 MPa, whereas formation by AG-3 isolates ceased at the lower matric potential of −1.5 MPa. Sclerotial germination also declined with decreasing osmotic and matric potential, with total inhibition occurring over the range −3.0 to −4.0 MPa on osmotically adjusted media, and at −2.0 MPa on matrically adjusted media. In soil, mycelial growth and sclerotial germination of AG-3 isolates declined with decreasing total water potential, with a minimum potential of −6.3 MPa permitting both growth and germination. The relevance of these results to the behaviour of R. solani AGs in soil and their pathogenicity on potato is discussed.     

Seed storage and germination in Kumara plicatilis,a tree aloe endemic to mountain fynbos in the Boland,south-western Cape,South Africa

Seed storage under appropriate conditions is a relatively inexpensive means of safeguarding plant genetic material for ex situ conservation. Post-storage germination trials are used to determine the viability of stored seeds, and hence the efficacy of the particular storage treatment. Kumara plicatilis (= Aloe plicatilis) is a tree aloe endemic to mountain fynbos in the Boland, south-western Cape. The viability and germination behaviour of K. plicatilis seeds were assessed for seeds stored for four and nine months at − 80 °C, 4 °C, 25 °C and under ambient conditions in a laboratory. Seeds were germinated under controlled conditions and germination rates and percentages determined. Ungerminated seeds were tested for viability using tetrazolium salt. Seed viability was not significantly reduced during storage. Seeds stored at − 80 °C for four and nine months exhibited the fastest germination rate overall (both 5.9 ± 0.3 weeks, mean ± S.E.), and slowest was for seeds stored under ambient conditions for four and nine months (both 7.8 ± 0.4 weeks). All seed lots showed similar percentage germination after four months of storage (78.0–90.4%). The highest percentage germination overall was for seeds stored at − 80 °C for four months (90.4%) and the lowest was for seeds kept at 4 °C and − 80 °C for nine months (39.2 and 39.6%, respectively). Respective percentage viability for ungerminated seeds in these two treatments was 82% and 87%, respectively, indicating the induction of secondary dormancy. Induced dormancy triggered by protracted cold temperatures may be an adaptation that enables seeds to survive prolonged extreme conditions that are unfavourable for germination. Further research on the long-term storage of aloe seeds would be beneficial for developing long-term seed storage and germination testing protocols for ex situ conservation.     

Effect of initial freezing temperature on the semen characteristics of frozen-thawed ram spermatozoa in a semi-arid tropical environment

Ram spermatozoa are sensitive to extreme changes in temperature during the freeze-thaw process. The degree of damage depends on a combined effect of various factors including initial freezing temperature. The present study was conducted to observe the effect of initial freezing temperature on post-thawing motility of ram spermatozoa of native and crossbred rams maintained in a semi-arid tropical environment. Good quality semen obtained from native Malpura and crossbred Bharat Merino rams were pooled within breed and diluted at a rate of 1000 million spermatozoa per milliliter in TEST—yolk–glycerol extender. Diluted semen samples were loaded in 0.25 ml straws and cooled to −25, −75 or −125 °C freezing temperature at the rate of −25 °C/min under controlled conditions before plunging into liquid nitrogen for storage. The thawing of straws was performed at 50 °C in a water bath for 10 s and motility characteristics of the frozen-thawed spermatozoa were assessed by a computer-assisted spermatozoa analysis technique. Initial freezing temperature significantly affected the post-thawing motility of sperm in both the breeds. The post-thawing % motility and rapid motile spermatozoa were significantly higher at initial freezing temperature of −125 °C and lower at −25 or −75 °C. The percentage medium motile sperm were similar at all three initial freezing temperatures. The percentage of slow motile and linearity of sperm varied (P<0.01) between the different freezing temperatures. The curvilinear velocity, average path velocity and straight line velocity of spermatozoa were higher (P<0.01) at −125 °C than −25 or −75 °C. Although the lateral head displacement of spermatozoa did not vary significantly between the different initial freezing temperatures, the stroke frequency was significantly lower at −25 °C than −75 or −125 °C. Except for % linearity, the average path velocity and straight line velocity, other spermatozoa characteristics were not significantly different between breeds. The interaction between freezing temperature and breed was significant only for the % motility and linearity of the spermatozoa. The study indicates that initial freezing temperature has a significant effect on spermatozoa motility and velocity following post-thawing. The best motile spermatozoa following thawing were achieved at −125 °C freezing temperature.     

Oestrus cycle characteristics and prediction of ovulation in Catalonian jennies

The Catalonian donkey breed is in danger of extinction, and much needs to be learned about the reproductive features of its females if breeding and conservation programmes are to be successful. This study reports the oestrous behaviour, oestrus cycle characteristics and dynamic ovarian events witnessed during 50 oestrous cycles (involving 106 ovulations) in 10 Catalonian jennies between March 2002 and January 2005. These jennies were teased, palpated transrectally and examined by ultrasound using a 5 MHz linear transducer—daily during oestrus and every other day during dioestrus. Predictors of ovulation were sought among the variables recorded.The most evident signs of oestrus were mouth clapping (the frequent vertical opening and closing of the mouth with ears depressed against the extended neck) and occasional urinating and winking of the vulval lips (homotypical behaviour). Interactions between jennies in oestrus were also recorded, including mounting, herding/chasing, the Flehmen response, and vocalization (heterotypical behaviour).Nine jennies ovulated regularly throughout the year; one had two anovulatory periods (54 and 35 days). The length of the oestrus cycle was 24.90 ± 0.26 days, with oestrus itself lasting 5.64 ± 0.20 days (mean ± S.E.M.) and dioestrus 19.83 ± 0.36 days. The incidence of single, double and triple ovulations was 55.66% (n = 59), 42.45% (n = 45) and 1.89% (n = 2), respectively. No significant difference was seen in the number of ovulations involving the left and right ovaries (52.63% [n = 70] compared to 47.37% [n = 63] respectively; P > 0.05). The mean interval between double ovulation was 1.44 ± 3.98 days. The mean diameter of the preovulatory follicle at day −1 was 44.9 ± 0.5 mm; the mean growth rate over the 5 days before ovulation was 3.7 mm/day.Data on preovulatory changes in oestrous behaviour, follicle size, follicle texture, the echographic appearance of the follicle and uterus, and uterine tone were subjected to stepwise logistic regression analysis to detect predictors of ovulation. The logit function showed the best predictors to be follicle size, follicular texture and oestrous behaviour. Certain combinations of these three variables allow the prediction of ovulation within 24 h with a probability of >75%.     

Development to the blastocyst stage of immature pig oocytes arrested before the metaphase-II stage and fertilized in vitro

In vitro fertilization (IVF) and embryonic development of mature and meiotically arrested porcine oocytes were compared in the present study. After in vitro maturation (IVM) of cumulus-oocyte complexes for 48 h, 75.4% of them extruded a visible polar body (PB). Most of the oocytes with a first polar body (PB+ group) were at the metaphase-II (M-II) stage (91.4%). Most of the oocytes without a visible polar body (PB− group) appeared to be arrested at the germinal vesicle (GV) (41.6%) and metaphase-I (M-I) (34.0%) stages. After IVF of oocytes (day of IVF = Day 0), there was no difference between PB⁺ and PB⁻ groups in rates of sperm penetration, mono-spermy, however oocyte activation rate after penetration was greater in the PB+ than in the PB− group (P < 0.05). On Day 2, there was no difference between rates of embryos cleaved at the 2–4 cell stages in PB+ and PB− groups (42.1 ± 48.8% and 33.6 ± 2.1%, respectively). On Day 4, the rate of PB+ embryos developing beyond the 4-cell stage was greater than that of PB− embryos (P < 0.05, 31.7 ± 3.9% and 14.1 ± 1.5%, respectively), and PB+ embryos had more cells than the PB− embryos (P < 0.05, 8.3 ± 0.4 and 6.0 ± 0.8 cells, respectively). On Day 6, a greater proportion of PB+ embryos developed to the blastocyst stage than did PB− embryos (P < 0.05, 34.6 ± 2.4% and 20.7 ± 2.8%, respectively). However, when the GV oocytes of the PB− group were not included in recalculations, there was no difference in blastocyst rates between M-I arrested and M-II oocytes (35.3 and 34.6%, respectively). The number of blastomere nuclei in embryos obtained from the PB+ group (52.0 ± 2.5) was greater than that from the PB− group (P < 0.05, 29.1 ± 2.8). The proportion of degenerated parts in the blastocysts, as determined by morphological appearance, was the same in the PB+ and PB− groups. Although the quality of PB+ embryos was enhanced as compared with that of the PB− group, the proportion of inner cell mass and trophectoderm cells in PB+ and PB− blastocysts did not differ (1:1.9 and 1:2.2, respectively). Chromosome analysis revealed that PB+ blastocysts had more diploidy (P < 0.05, 69.7%) than did PB− blastocysts (44.0%), whereas PB− blastocysts had more triploid cells (P < 0.05, 34.0%) than did PB+ oocytes (8.4%). These results indicate that pig oocytes arrested before the M-II stage (M-I oocytes) undergo cytoplasmic maturation during maturation culture and have the same ability to develop to blastocysts after IVF as M-II oocytes, but some of them resulted in degeneration or delayed development with poor embryo quality.     

Predicting germination in semi-arid wildland seedbeds II. Field validation of wet thermal-time models

Accurate prediction of germination for species used for semi-arid land revegetation would support selection of plant materials for specific climatic conditions and sites. Wet thermal-time models predict germination time by summing progress toward germination subpopulation percentages as a function of temperature across intermittent wet periods or within singular wet periods. Wet periods may be defined by any reasonable seedbed water potential above which seeds are expected to imbibe sufficiently to germinate. These models may be especially applicable to the Artemisia steppe of the western U.S.A. where water availability limits germination in summer and early fall while cool temperatures limit germination in late fall, winter, and spring when soil water is available. To test accuracy of wet thermal-time models we placed seedbags with seeds of five species commonly used in wildland revegetation, as well as two collections of the invasive annual grass, Bromus tectorum L. into Artemisia tridentata Nutt. ssp. wyomingensis Beetle and Young zone seedbeds for 19 field incubation periods over four seasons. Hourly surface (1–3 cm) soil temperatures and soil water potentials were measured near the seedbags. These data were input into thermal-time models which predicted time to germination for each seedbag retrieval date. Binomial data representing agreement (1) or lack of agreement (0) of predicted and actual germination for each retrieval date were analyzed using logistic regression. Thermal summation method, season, water potential threshold, and species most affected accuracy of predictions (P < 0.0002). A model which defined a wet period as ≥−1.5 MPa soil water potential and summed progress toward germination across intermittent wet periods was most accurate in predicting actual germination by a retrieval date. Across all species, this model correctly predicted that germination would occur in seedbags 75–95% of the time over the latewinter to mid-spring seasons, but only 50–71% of the time for the fall-early winter season when time of soil water availability was least. Although the wet thermal-time model overestimated time to germination for some species and seasons, its accuracy should be high enough to evaluate germination potential by mid-spring for different species, sites, and climatic conditions.     

Embryonic diapause in the Australian plague locust relative to parental experience of cumulative photophase decline

The Australian plague locust Chortoicetes terminifera (Walker) exhibits facultative embryonic diapause during autumn. To approximate natural photoperiod changes during late summer and autumn, locust nymphs were reared under different total declines in laboratory photophase (−0.5, −0.75, −1.0, −1.25, −1.5, −1.75, −2 h each lowered in 15 min steps) in a 24 h photoperiod to quantify any effect on the subsequent production of diapause eggs. Induction of diapause eggs was significantly affected by accumulated photoperiod decline experienced by the parental generation throughout all development stages from mid-instar nymph to fledgling adult. The incidence of embryonic diapause ranged from nil at −0.5 h to 86.6% diapause at −2 h. Continued declines in photoperiod for post-teneral locusts (transitioned from −1 h until fledging to −1.75 h) produced a further increase in the proportion of diapause eggs. The results were unaffected by time spent at any given photoperiod, despite a previously indicated maximal inductive photoperiod of 13.5 h being used as the mid-point of all treatments. Implications for the seasonal timing processes of photoperiodism in C. terminifera, which has a high migratory capacity and a latitudinal cline in the timing of diapause egg production across a broad geographic range, are discussed.     

Enhancing bio-suppression of Parthenium hysterophorus L.: Diapause in Zygogramma bicolorata Pallister and its manipulation through insulin-like peptides (ILPs)

In-depth investigations on diapause behaviour of Z. bicolorata revealed that the adults entered diapause at any time from August to December and that the number peaked (42.00%) during the last half of November. The percentage of adults entering diapause increased with a decrease in day length. Weight of diapausing adults was significantly higher than weight of non-diapausing adults. The percentage of adults undergoing diapause at 30 °C was significantly lower than those undergoing diapause at 15 and 25 °C. The percentage of adults burrowing increased with increasing moisture. In silty soil and soil with high organic matter, 46.7% and 49.2% of adults entered diapause, respectively, whereas in sandy soil, only 23.5% of adults entered diapause. When newly emerged beetles were exposed to 5 μg of human insulin 30/70, a significantly lower percentage of treated adults underwent diapause compared to untreated adults under both feeding and no feeding conditions. Insulin treatment also influenced the emergence period from diapause (93.92 ± 1.73 days), percent emergence (81 ± 1.54%) and fecundity/month (512.7 ± 25.38 eggs) of Z. bicolorata in treated adults as compared to untreated adults (109.05 ± 2.2, 74.00 ± 1.82 and 438.3 ± 19.33 eggs, respectively). However, there was no significant impact of insulin on adult longevity. These findings are of great utility in the biological suppression of Parthenium as it will enhance the effectiveness of this beetle through manipulation of diapause.     

The effects of fire on woody plant encroachment are exacerbated by succession of trees of decreased palatability

The ingression of woody plants into the grassy layer of savannas and grasslands has become a global concern. The increase of woody plants has been primarily attributed over grazing, fire and more recently to the increase of atmospheric CO₂. We used long-term observations and analyses to assess changes in woody vegetation in Ithala Game Reserve (IGR), South Africa. Textural analysis of aerial photographs was used to detect changes in woody vegetation, from 1943 to 2007 in Ithala Game Reserve (IGR), South Africa. Daily rainfall data from 1905 to 2009 were used in a time-series analysis to determine if rainfall patterns have changed. The time-series analysis showed that the low magnitude (0–10 mm) rainfall events decreased from 1916 to 2009 and high magnitude rainfall events increased (10–20 and >20 mm). The mean annual rainfall increased from ～700 to ～850 mm from the 1930s to the 2000s. This change in rainfall was a key factor in the increase in woody vegetation from 1943 to 2009. We also used field data from the same reserve collected over 30 years to assess the increases in tree cover. Tree cover and density increased significantly by 32.5% and 657.9 indiv ha^?1 respectively, over 64 years. Before the proclamation of IGR in 1972, increases in woody vegetation from 1943 were non-significant. After the proclamation of IGR, herbivore population numbers and spatial distribution influenced the accumulation of grassy biomass required to fuel fires. In areas with reduced fuel loads, the consequential suppression of fire accelerated the rate of woody plant invasion into savannas. The increase in woody vegetation coincided with a decrease in palatable (e.g. Acacia gerrardii and Acacia davyi) and an increase in unpalatable woody plants. The avoidance of the unpalatable trees (e.g. Euclea and Searsia species) by large mammalian herbivores has allowed these trees to increase in density relatively unhindered.     

Verification of a threshold concept of ecologically effective precipitation pulse: From plant individuals to ecosystem

In water-limited ecosystems, an ecologically significant rainfall pulse was defined as a rainfall event that altered both soil water status and plant physiological activity. We developed a new threshold concept of an ecologically effective precipitation pulse (EEPP) applicable to both plant individual and ecosystem scales. The concept was tested in a typical steppe on Inner Mongolia plateau. Two EEPPs, single 3-mm rainfall and 5-mm rainfall, were applied to investigate their effects on soil and plant water status, CO₂ assimilation of five species (four C₃ plants and one C₄ plant), whole-plot soil respiration (R_s), and net ecosystem CO₂ exchange (NEE) on 1 June and 28 July 2009, respectively. Both EEPPs increased leaf water potential (Ψ_l) of all the species, which peaked 1–3 days after rainfall pulses. Soil water content (SWC) in two depths (5 cm and 20 cm) significantly increased after the two EEPPs for 1–3 days. Soil water potential (Ψ_s) within 20‐cm soil layer in EEPP treatments significantly differed (p < 0.05) from control. Net assimilation rates (A_net) of all C₃ plants had a slight increase at the next day after two EEPPs, in contrast to the C₄ species. R_s elevated and peaked 1–3 days later after water supply. Ecosystem net CO₂ absorption rate rose to maximum value 3 days after the 5-mm pulse on 28 July, higher than the response to 3-mm pulse on June 1. The grassland turned to net emission of CO₂ after 3-mm pulse on 28 July. The results supported that there was an ecosystem level threshold for EEPP, and the threshold was temporally variable. It also highlighted the necessity of considering the response threshold of EEPP in rainfall manipulative experiment. In addition, effective rainfall amount was more approriate than total rainfall amount in modeling ecosystem carbon balance.     

Seasonal abundance and activity of pill millipedes (Arthrosphaera magna) in mixed plantation and semi-evergreen forest of southern India

Seasonal occurrence and activity of endemic pill millipedes (Arthrosphaera magna) were examined in organically managed mixed plantation and semi-evergreen forest reserve in southwest India between November 1996 and September 1998. Abundance and biomass of millipedes were highest in both habitats during monsoon season. Soil moisture, conductivity, organic carbon, phosphate, potassium, calcium and magnesium were higher in plantation than in forest. Millipede abundance and biomass were about 12 and 7 times higher in plantation than in forest, respectively (P < 0.001). Their biomass increased during post-monsoon, summer and monsoon in the plantation (P < 0.001), but not in forest (P > 0.05). Millipede abundance and biomass were positively correlated with rainfall (P = 0.01). Besides rainfall, millipedes in plantation were positively correlated with soil moisture as well as temperature (P = 0.001). Among the associated fauna with pill millipedes, earthworms rank first followed by soil bugs in both habitats. Since pill millipedes are sensitive to narrow ecological changes, the organic farming strategies followed in mixed plantation and commonly practiced in South India seem not deleterious for the endangered pill millipedes Arthrosphaera and reduce the risk of local extinctions.     

Ecophysiological requirements on seed germination of a Mediterranean perennial grass (Stipa tenacissima L.) under controlled temperatures and water stress

Stipa tenacissima L. (alpha grass) steppes are one of the most representative ecosystems in arid Mediterranean ecosystems. On the one hand these steppes, which are perpetually exposed to climate and strong anthropogenic pressure, have undergone severe degradation. On the other hand, the ability of S. tenacissima to regenerate naturally is significantly reduced. In this study the germination response and seedling emergence of S. tenacissima are examined in relation to the main environmental factors (water stress and temperature) under laboratory-controlled conditions. The main aim of this paper was to investigate the influence of temperature over a temperature range (10 °C–30 °C) and water stress induced by the solutions of polyethylene glycol (PEG)-6000 (0 to − 1.6 MPa) for a period of 30 days, on the germination behavior of S. tenacissima seeds. The results showed that temperatures between 10° and 20 °C seem to be favorable for the germination of this species, with optimum temperatures among accessions found in 20 °C. When seeds were water-stressed, germination severely decreased at − 0.8 MPa, indicating that the accession resistance limits to the water stress, and was completely inhibited at − 1.6 MPa. Consequently, the final germination percentage (FGP) decreased and the mean time germination (MTG) increased. Based on the empirical data of the germination rate, we estimated that the parameters of the thermal time and hydrotime models showed different values in all accessions which proves the difference between accession adaptive capacities.     

Variability of soil carbon sequestration capability and microbial activity of different types of salt marsh soils at Chongming Dongtan

Variations in the soil carbon sequestration capability of different types of salt marsh soils at Chongming Dongtan and its influencing factors were studied by analyzing the soil organic carbon (SOC) content, organic matter input and microbial activities. The results indicated that the total SOC content at Area A (southeast of Dongtan, sandy soil with Phragmites communis) was only 46.11% of that of Area B (northeast of Dongtan, clay soil with mixed P. communis and Spartina alterniflora) (P = 0.000 < 0.05), but their organic matter input per year was almost identical. These findings implied that Area B had a lower output of SOC. The microbial biomass at Area A was 3.83 times greater than that at Area B (P = 0.049 < 0.05); the soil catalase and invertase activities at Area A, which were related to carbon metabolism, were 60.31% (P = 0.006 < 0.05) and 34.33% (P = 0.021 < 0.05) higher than at Area B, respectively; and the soil respiration at Area A was also higher than at Area B. These findings implied that the microbial activities at Area A were greater than those at Area B, and therefore the carbon metabolism was rapid, resulting in increased SOC output at Area A. Increased water content and salinity in the clay soil at Area B may inhibit the microbial activities, thereby reducing the decomposition of the organic matter and enhancing carbon sequestration. In addition, some artificial measures for controlling spread of S. alterniflora at Area B (mowing/digging and tillage (M + D); mowing/digging and tillage/waterlogging (M + D + W)) were found to generally improve the microbial activity of soil, thereby increasing SOC output. However, when the two different physical controlling modes were compared, the SOC and microbial activities of the soil subjected to the M + D + W treatment were relatively high and low, respectively, due to waterlogging restraining the microbial metabolism. These findings indicated that the difference in microbial activities was the important factor leading to variability in the SOC sequestration capability between Areas A and B. Additionally, with the exception of soil texture and vegetation types, environmental conditions and artificial turbulence also influenced microbial activities of soil, and hence SOC output and organic carbon sequestration capability.     

In vitro water stress bioassays with the nematophagous fungus Pochonia chlamydosporia: Effects on growth and parasitism

The biocontrol potential of Pochonia chlamydosporia, a fungus with parasitic activity against economically important plant-parasitic nematodes, can be influenced by abiotic factors such as water availability. The objective of this study was to evaluate the effects of different water stress regimes on in vitro growth, sporulation, germination and parasitism of P. chlamydosporia isolates. The osmotic water potential of 1.7% corn meal agar (CMA) was modified by addition of potassium chloride (KCl) or glycerol, and the matric water potential was modified using polyethylene glycol (PEG 8000). The fungus was able to grow over a range of potentials but radial growth rates decreased with the increase of osmotic and matric stress. No growth was observed at −10 MPa on 1.7% CMA amended with glycerol and at −7.1 MPa on medium with PEG 8000 but all isolates were able to resume growth when transferred onto unmodified 1.7% CMA. The production of chlamydospores was repressed in both osmotic and matric modified media. Although the production of conidia increased in medium modified with KCl, the germination rate was lower. Spores/hyphal fragments remained viable in all isolates that were previously inoculated onto media with growth-limiting water potential (−10 MPa on 1.7% CMA amended with glycerol and −10 MPa on medium with PEG 8000). The percentage of viable conidia produced on 1.7% CMA, after inoculation under osmotic or matric stress conditions for 25 days, was over 74.5% in all isolates (osmotic stress) and ranged from 1% (Pc1) to 65.8% (Pc280) (matric stress). The in vitro infection of potato cyst nematodes, Globodera rostochiensis eggs by P. chlamydosporia isolates, grown under these limiting conditions, was studied using a standard bioassay. The percentage of parasitized eggs was significantly higher under osmotic stress except for isolates Pc2 and Pc3. P. chlamydosporia spores/hyphal fragments can remain viable at water potentials limiting for growth, for prolonged periods of time, suggesting that the osmoregulation mechanisms, used to compensate water stress, affect in vitro sporulation and increased pathogenicity. Knowledge on water requirements of P. chlamydosporia enables a better understanding of its survival and growth strategies in the soil environment and could aid the development of effective strategies to increase the production and quality of inoculum, thus contributing to the implementation of biosafe, sustainable management strategies against plant-parasitic nematodes.     

Patients at risk for trace element deficiencies: Bariatric surgery

Obesity is a worldwide epidemic associated with diseases such as diabetes mellitus and cardiovascular disease. Current methods for weight loss are not very effective, particularly for those with morbid obesity. Surgical therapy may be recommended for those with a BMI ≥ 40 kg/m², or BMI ≥ 35 kg/m² with co-morbidities. This therapy can produce significant weight loss and improve/resolve co-morbidities including hypertension and hyperlipidemia. Yet successes may be tempered by adverse effects on trace element absorption and status. A PubMed literature search identified studies from January 1980 to February 2013 for inclusion in a meta-analysis. Publications that contained keywords ‘bariatric surgery or gastric bypass,’ ‘trace element or mineral or zinc or iron or copper or iodine or manganese’, and ‘absorption or status or rate or level’ were identified. Inclusion criteria were human markers that reflect changes in trace element status before and after bariatric surgery. The meta-analysis found a decrease in blood copper, zinc, hemoglobin, as well as an increase in iron, regardless of the type of surgery. The pooled effect sizes and 95% confidence intervals were 0.17 and −0.09 to 0.43 for plasma/serum iron (p = 0.20); −0.49 and −0.67 to −0.31 for blood hemoglobin (p = 0.00); −0.47 and −0.90 to −0.05 for plasma/serum copper (p = 0.03); −0.77 and −1.20 to −0.35 for plasma/serum zinc (p = 0.00). Differences in levels of these minerals pre- and post-surgery may have been influenced by the time period after surgery, a pre-existing deficiency, type and dose of vitamin–mineral supplements, and malabsorption due to elimination of parts of the gastrointestinal tract.     

Microbial processes and bacterial populations associated to anaerobic treatment of sulfate-rich wastewater

A pilot-scale (1.2 m³) anaerobic sequencing batch biofilm reactor (ASBBR) containing mineral coal for biomass attachment was fed with sulfate-rich wastewater at increasing sulfate concentrations. Ethanol was used as the main organic source. Tested COD/sulfate ratios were of 1.8 and 1.5 for sulfate loading rates of 0.65–1.90 kgSO₄²⁻/cycle (48 h-cycle) or of 1.0 in the trial with 3.0 gSO₄²⁻ l⁻¹. Sulfate removal efficiencies observed in all trials were as high as 99%. Molecular inventories indicated a shift on the microbial composition and a decrease on species diversity with the increase of sulfate concentration. Beta-proteobacteria species affiliated with Aminomonas spp. and Thermanaerovibrio spp. predominated at 1.0 gSO₄²⁻ l⁻¹. At higher sulfate concentrations the predominant bacterial group was Delta-proteobacteria mainly Desulfovibrio spp. and Desulfomicrobium spp. at 2.0 gSO₄²⁻ l⁻¹, whereas Desulfurella spp. and Coprothermobacter spp. predominated at 3.0 gSO₄²⁻ l⁻¹. These organisms have been commonly associated with sulfate reduction producing acetate, sulfide and sulfur. Methanogenic archaea (Methanosaeta spp.) was found at 1.0 and 2.0 gSO₄²⁻ l⁻¹. Additionally, a simplified mathematical model was used to infer on metabolic pathways of the biomass involved in sulfate reduction.     

Assessment of germination and carnivorous activities of a nematode-trapping fungus Arthrobotrys dactyloides in fungistatic and fungicidal soil environment

Carnivorism is the ability of nematode-trapping fungi to trap and digest the nematodes by sophisticated devices called traps. Delivery of nematode-trapping fungi in soil for bio-control of pest nematodes often fails or gives inconsistent results. Possible reasons for failure could be the effect of soil fungistasis on germination of nematode-trapping fungi in soil environment, use of avirulent species and sensitivity of these fungi to fungicidal residues in soil. Exploitation of nematode-trapping fungi for nematode control demands that it be compatible with fungicides applied in soil or crops and proliferate in soil. This investigation represents is one of the first to evaluate the effect of fungicides on the nematode-trapping fungus Arthrobotrys dactyloides. A. dactyloides showed in vitro carnivorous potential against Meloidogyne incognita, Meloidogyne javanica, Meloidogyne graminicola, Helicotylenchus dihystera and Heterodera cajani. Conidia of A. dactyloides exposed to agricultural soils showed poor germination but formed conidial traps, which captured and killed the soil nematodes. Conidial traps, which trapped the nematodes, grew well in all soils after killing and nutrient absorption from nematode body. Soil amended with 20 mg ai kg⁻¹ of carbendazim and thiram, 30 mg ai kg⁻¹ of mancozeb, 50 mg ai kg⁻¹ of captan, and 100 mg ai kg⁻¹ of carboxin completely checked the conidial trap formation and nematode capturing. 30, 50 and 100 mg ai kg⁻¹ of metalaxyl adversely affected the conidial trap formation and nematode capturing in soil. Propiconazole inhibited 15.2% conidial trap formation up to 50 mg ai kg⁻¹ but caused 93.3% inhibition of conidial traps formation and complete inhibition of nematode capturing at 100 mg ai kg⁻¹. Sulphur, triademefon, and tricyclazole showed least toxic effect on conidial trap formation and nematode capturing activities of A. dactyloides in soil up to 100 mg ai kg⁻¹.     

Influence of rhizospheric microbial inoculation and tolerant plant species on the rhizoremediation of lindane

Application of rhizospheric microbes to enhance the phytoremediation of organic pollutants has gained considerable attention recently due to their beneficial effects on the survival and growth of plants in contaminated soil sites. The present study was demonstrated to test the combined rhizoremediation potential of Staphylococcus cohnii subspecies urealyticus in the presence of tolerant plant Withania somnifera grown in lindane spiked soil. Withania was grown in garden soil spiked with 20 mg kg⁻¹ of lindane and inoculated with 100 ml of microbial culture (8.1 × 10⁶ CFU). Effect of microbial inoculation on plant growth, lindane uptake, microbial biomass carbon, dehydrogenase activity, residual lindane concentration and lindane dissipation percentage were analyzed. The microbial inoculation significantly enhances the growth and lindane uptake potential of test plant (p < 0.05). Furthermore, there was an enhanced dissipation of lindane observed in microbial inoculated soil than the dissipation rate in non-inoculated soil (p < 0.01) and the dissipation rate was positively correlated with the soil dehydrogenase activity and microbial biomass carbon (p < 0.05). The study concludes that the integrated use of tolerant plant species and rhizospheric microbial inoculation can enhance the dissipation of lindane, and have practical application for the in situ remediation of contaminated soils.