Relationship between basal soil respiration rate, tree stand and soil characteristics in boreal forests.

Soil respiration is considered to represent the overall microbial activity reflecting mineralisation of organic matter in soil. It is the most commonly used biological variable in soil studies. In long-term monitoring of forested areas, there is a need for reference values for soil microbiological variables in different forest ecosystems. In this study we describe the relationship between soil respiration rate, tree stand and humus chemical characteristics of boreal coniferous forests stands. Soil respiration rate was higher in pine dominated than in spruce dominated study sites when the result was calculated on dry matter bases. However, when calculated on area bases, the result was opposite and no difference was found when the soil respiration rate was calculated on organic carbon bases. Irrespective of the main tree species, the soil respiration rate was equal in different development classes but not equal in soil fertility classes, i.e. within forest site types based on differences in ground vegetation. Respiration rates were clearly higher in mesic sites when calculated on dry matter, C(org) or area bases. However, soil respiration rate did not correlate with soil chemical variables indicating site fertility. Soil respiration rate on dry matter basis was at a lower level in the south and on more fertile sites, and on the other hand at a higher level in older stands and on sites with a thicker organic layer.

Effects of different plant protection programs on soil microbes.

The aim of this study was to assess the effects of two pesticide regimens (conventional full insurance compared with supervised and reduced pesticide use) and two cultivation techniques (conventional tillage and fertilization compared with no tillage and lower fertilization) on soil microbes in a field study, and to evaluate the results with laboratory tests. The herbicides used were chlorsulfuron, MCPA, and bentazone; the fungicides carboxin-imazalin and propiconazole; and the insecticides dimethoate and pirimicarb. In the field studies, the effects on microbial biota were assessed by measuring biomass (ATP content) and microbial activities related to carbon and nitrogen metabolism (soil respiration, nitrification potential). Potential harmful effects of commercial formulations of the same pesticides on microbes were studied in the laboratory with two bacterial toxicity tests (Pseudomonas putida growth inhibition and Vibrio fischeri luminescence inhibition tests) and with a soil respiration inhibition test. Bioavailability of the pesticides in the soil was assessed by a solid-phase modification of the luminescent bacteria test. In the field studies the microbial activities and biomass followed the weather conditions during the growing season, and significant effects of pesticide treatments on microbial processes were not observed. In the laboratory studies the toxicity of certain pesticides was clearly detected by bacterial toxicity tests. However, in the soil respiration inhibition assessment with soil similar to that used in the field trial, inhibition was observed only at unrealistically high concentrations. This could be due to the limited bioavailability of the pesticides in soil of high clay and organic carbon content.

The quantitative insulin sensitivity check index QUICKI predicts the onset of type 2 diabetes better than fasting plasma insulin in obese subjects: a 5-year follow-up study.

The aim of the present study was to evaluate the predictive value of QUICKI and fasting plasma insulin (FPI0 as predictors of the onset of type 2 diabetes mellitus. We performed a five-year follow-up study in a sample of middle-aged subjects with at least one of the following risk factors; hypertension defined as systolic blood pressure >or=160 mmHg and/or diastolic blood pressure >or=90 mmHg or medication for hypertensin, obesity defined as a body mass index >or=30 kg/m(2) and/or a waist-to-hip ratio >or=1.00 in men and >or=0.88 in women, or a family history of type 2 DM. When the QUICKI index was used to compare the tertile with the lowest risk to the tertile of the highest risk of obese subjects. Odd's Ratio (OR) for type 2 diabetes was 7.77 (95% CI 1.39-202.24). For FPI, the respective OR's were 2.84 (95% CI 0.82-9.82) and 3.96 (95% CI 1.02-15.48). QUICKI and fasting insulin did not have a statistically significant predictive value among non-obese subjects. Concerning QUICKI, the subjects in the tertiles at the medium and highest risk had a higher risk for type 2 DM than the corresponding tertiles of FPI among obese subjects.

Relative weight gain and obesity as a child predict metabolic syndrome as an adult.

OBJECTIVE: To examine whether birth weight, weight gain from birth to the age of seven or body-mass index at the age of seven have any association with metabolic syndrome as an adult. DESIGN: A population study. SUBJECTS: 210 men and 218 women out of a total 712 subjects aged 36, 41 or 46 years in Pieksämäki town, Finland. MAIN OUTCOME MEASURES: Weight at birth and weight and height at the age of seven and metabolic syndrome defined as a clustering of hypertension, dyslipidemia (hypertriglyceridaemia or low high-density-lipoprotein cholesterol), and insulin resistance (inferred by abnormal glucose tolerance or hyperinsulinaemia). RESULTS: No association was found between birth weight and the metabolic syndrome as an adult. Among obese children at the age of seven (body-mass index in the highest quartile), the odds ratio (OR) for the metabolic syndrome in adulthood was 4.4 (95% CI 2.1-9.5) as compared to the other children (the three other quartiles combined). After adjustment for age, sex and current obesity, the risk of the syndrome still was 2.4 (95% CI 2.1-9.5). CONCLUSION: We could not replicate the close association between low birth weight and the metabolic syndrome in adulthood as has been shown in some earlier studies. Obesity at the age of seven predicts the metabolic syndrome in adulthood.

Effects of growth-promoting antimicrobials on inhibition of Yersinia enterocolitica O:3 by porcine ileal microflora.

The survival of Yersinia enterocolitica serotype O:3 was examined in an in vitro model of the porcine ileum in the presence of normal ileal microflora using a medium supplemented with the growth-promoting antimicrobials avoparcin, spiramycin, tylosin, carbadox and olaquindox, or without any antimicrobials, at 39 degrees C for 5 d. Growth of Y. enterocolitica was inhibited in all trials in the following order: avoparcin < carbadox < spiramycin < no feed additives < tylosin < olaquindox. The media supplemented with avoparcin, carbadox and spiramycin supported the survival of Y. enterocolitica up to 5 d. When incubated with the normal ileal microflora without any growth-promoting antimicrobials, Y. enterocolitica could not be isolated after 4 d. With olaquindox and tylosin, Y. enterocolitica was not detected after 3 d.

Structure of a microbial community in soil after prolonged addition of low levels of simulated acid rain

Humus samples were collected 12 growing seasons after the start of a simulated acid rain experiment situated in the subarctic environment. The acid rain was simulated with H2SO4, a combination of H2SO4 and HNO3, and HNO3 at two levels of moderate acidic loads close to the natural anthropogenic pollution levels of southern Scandinavia. The higher levels of acid applications resulted in acidification, as defined by humus chemistry. The concentrations of base cations decreased, while the concentrations of exchangeable H+, Al, and Fe increased. Humus pH decreased from 3.83 to 3.65. Basal respiration decreased with decreasing humus pH, and total microbial biomass, measured by substrate-induced respiration and total amount of phospholipid fatty acids (PLFA), decreased slightly. An altered PLFA pattern indicated a change in the microbial community structure at the higher levels of acid applications. In general, branched fatty acids, typical of gram-positive bacteria, increased in the acid plots. PLFA analysis performed on the bacterial community growing on agar plates also showed that the relative amount of PLFA specific for gram-positive bacteria increased due to the acidification. The changed bacterial community was adapted to the more acidic environment in the acid-treated plots, even though bacterial growth rates, estimated by thymidine and leucine incorporation, decreased with pH. Fungal activity (measured as acetate incorporation into ergosterol) was not affected. This result indicates that bacteria were more affected than fungi by the acidification. The capacity of the bacterial community to utilize 95 different carbon sources was variable and only showed weak correlations to pH. Differences in the toxicities of H2SO4 and HNO3 for the microbial community were not found.

Vitality fertilization of Scots pine stands growing along a gradient of heavy metal pollution: short-term effects on microbial biomass and respiration rate of the humus layer.

In 1992 forest vitality fertilization experiments were established on a heavy metal deposition gradient with four treatments in three replications at distances of 0.5, 4 and 8 km from a Cu-Ni smelter in order to estimate their impact on the disturbed forest ecosystem. The increase in Cu concentration in the humus (F/H) layer of the Calluna site type Scots pine (Pinus sylvestris) stands from ca. 300 to 8000 mg kg(-1) d.m. (dry matter) along the 8 km long transect towards the smelter resulted in declining soil microbial biomass and soil respiration activity. Three independent measurements of microbial biomass: C(mic)-FE (fumigation extraction), C(mic)-SIR (substrate induced respiration), and ATP have been used together with an indicator of fungal biomass (ergosterol) and microbial activity (soil respiration). Within this Cu pollution range, all the measured microbial biomass levels declined to 10%-28% of the control plot values and activity assessed by respiration was lowered to 16%. Liming has increased the C(mic)-SIR and respiration rate. Treatments with test fertilizer, made from grounded apatite, did not result in different microbial biomass and respiration rate values compared to the respective controls along the whole gradient. Nitrogen + lime treatments resulted in similar changes to lime alone. No changes, as compared to the respective control, could be detected with nitrogen fertilization at the less polluted end of the gradient.