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- Griffiths, B S, et al.
(författare)
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Ecosystem response of pasture soil communities to fumigation-induced microbial diversity reductions: an examination of the biodiversity-ecosystem function relationship
- 2000
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Ingår i: Oikos. - : Wiley. - 1600-0706 .- 0030-1299. ; 90:2, s. 279-294
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Tidskriftsartikel (refereegranskat)abstract
- A technique based on progressive fumigation was used to reduce soil microbial biodiversity, and the effects of such reductions upon the stability of key soil processes were measured. Mineral soil samples from a grassland were fumigated with chloroform for up to 24 h and then incubated for 5 months to allow recolonisation by surviving organisms. The diversity of cultivable and non-cultivable bacteria, protozoa and nematodes was progressively reduced by increasing fumigation times, as was the number of trophic groups, phyla within trophic groups, and taxa within phyla. Total microbial biomass was similar within fumigated soils, but lower than for unfumigated soil. There was no direct relationship between biodiversity and function. Some broad-scale functional parameters increased as biodiversity decreased, e.g. thymidine incorporation, growth on added nutrients, and the decomposition rate of plant residues. Other more specific parameters decreased as biodiversity decreased, e.g. nitrification, denitrification and methane oxidation. Thus specific Functional parameters may be a more sensitive indicator of environmental change than general parameters. Although fumigation reduced soil microbial biodiversity, there was evidence to suggest that it selected for organisms with particular physiological characteristics. The consequences of this for interpreting biodiversity - function relationships are discussed. The stability of the resulting communities to perturbation was further examined by imposing a transient (brief healing to 40 degrees C) or a persistent (addition of CuSO4) stress. Decomposition of grass residues was determined on three occasions after such perturbations. The soils clearly demonstrated resilience to the transient stress; decomposition rates were initially depressed by the stress and recovered over time. Resilience was reduced in the soils with decreasing biodiversity. Soils were not resilient to the persistent stress, there was no recovery in decomposition rate over time, but the soils with the highest biodiversity were more resistant to the stress than soils with impaired biodiversity. The study of functional stability under applied perturbation is a powerful means of examining the effects of biodiversity.
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| 2. |
- Cho, Eunyoung, et al.
(författare)
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Alcohol intake and colorectal cancer : a pooled analysis of 8 cohort studies
- 2004
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Ingår i: Annals of Internal Medicine. - : American College of Physicians. - 0003-4819 .- 1539-3704. ; 140:8, s. 603-613
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Epidemiologic studies have generally reported positive associations between alcohol consumption and risk for colorectal cancer. However, findings related to specific alcoholic beverages or different anatomic sites in the large bowel have been inconsistent. OBJECTIVE: To examine the relationship of total alcohol intake and intake from specific beverages to the incidence of colorectal cancer and to evaluate whether other potential risk factors modify the association. DESIGN: Pooled analysis of primary data from 8 cohort studies in 5 countries. SETTING: North America and Europe. PARTICIPANTS: 489,979 women and men with no history of cancer other than nonmelanoma skin cancer at baseline. MEASUREMENTS: Alcohol intake was assessed in each study at baseline by using a validated food-frequency questionnaire. RESULTS: During a maximum of 6 to 16 years of follow-up across the studies, 4687 cases of colorectal cancer were documented. In categorical analyses, increased risk for colorectal cancer was limited to persons with an alcohol intake of 30 g/d or greater (approximately > or =2 drinks/d), a consumption level reported by 4% of women and 13% of men. Compared with nondrinkers, the pooled multivariate relative risks were 1.16 (95% CI, 0.99 to 1.36) for persons who consumed 30 to less than 45 g/d and 1.41 (CI, 1.16 to 1.72) for those who consumed 45 g/d or greater. No significant heterogeneity by study or sex was observed. The association was evident for cancer of the proximal colon, distal colon, and rectum. No clear difference in relative risks was found among specific alcoholic beverages. LIMITATIONS: The study included only one measure of alcohol consumption at baseline and could not investigate lifetime alcohol consumption, alcohol consumption at younger ages, or changes in alcohol consumption during follow-up. It also could not examine drinking patterns or duration of alcohol use. CONCLUSIONS: A single determination of alcohol intake correlated with a modest relative elevation in colorectal cancer rate, mainly at the highest levels of alcohol intake.
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