163 research outputs found
Influence of irrigated agriculture on soil carbon and microbial community structure
Increasing the amount of carbon (C) in soils is
one method to reduce the concentration of carbon dioxide
(CO2) in the atmosphere. We measured organic C stored in
southern Idaho soils having long-term cropping histories that
supported native sagebrush vegetation (NSB), irrigated moldboard
plowed crops (IMP), irrigated conservation-chisel-tilled
crops (ICT), and irrigated pasture systems (IP). The CO 2 emitted
as a result of fertilizer production, farm operations, and
CO2 lost via dissolved carbonate in irrigation water, over a
30-year period, was estimated and used to calculate net C
fixation. Organic C in ecosystems decreased in the order
IP>ICT>IMP> NSB. In February 2001, active fungal, bacterial,
and microbial biomass was greater in IP soils than all
other soils. Active fungal, bacterial, and microbial biomass
was least in ICT soils at the 15-30-cm depth than all other
soils. In August 2001, active bacterial biomass was greater in
IMP soils than IP, ICT, and NSB soils. Active fungal biomass
was greater in IP soils than all other soils. Whole-soil fatty acid
profiles differed among management regimes and sampling
dates and, to a lesser extent, with soil depth. FAME profiles
from the NSB soils were distinct from the agricultural treatments
and contained greater amounts of total fatty acids than
the other treatments. The IMP and ICT soils yielded fatty acid
profiles that were similar to each other, although those at the
15-30-cm depth were distinct from all other treatment-depth
combinations. The IP FAME profiles suggest that arbuscular
mycorrhizal fungi are more common in these soils than soils
from the other treatments. Differences in carbon substrate
utilization patterns (BIOLOG) among treatments were more
variable and less pronounced that FAME results. In general,
irrigated arid soils can both increase C storage while increasing
microbial biomass and changing microbial diversity
The influence of vegetation in riparian filterstrips on coliform bacteria: II. Survival in soils
Survival of total and fecal coliform bacteria was measured in the
0 to 5, 5 to 15, and 15 to 30 cm soil depths at 1, 3, 7, 14, and 90 to
120 d after swine (Sus scrofa) wastewater application to riparian
filterstrips in southern Georgia during each season of the year. Vegetative
treatments evaluated were: (i) 20 m grass-10 m forest, (ii) 10 m
grass-20 m forest, and (iii) 10 m grass-20 m maidencane (Panicum
hemitomon Schult.). During winter, spring, and summer vegetation
type in riparian filterstrips did not affect survival of total and fecal
coliform bacteria. Total and fecal coliform bacterial numbers were
usually higher in the top 0 to 5 cm of soil than in the 5 to 15 and 15
to 30 cm soil depths in all treatments. Total and fecal coliform numbers
in the 0 to 5, 5 to 15, and 15 to 30 cm depths declined approximately
10-fold every 7 to 14 d after waste application in all seasons of the
year. At 90 to 120 d after waste application, total and fecal coliform
numbers in the three soil depths did not differ from riparian filterstrips
that did not have animal waste applied. Total coliform bacteria in the
O to 5, 5 to 15, and 15 to 30 cm soil depths correlated with temperature
and moisture in a curvilinear relationship (r2 = 0.80 , 0.77, and 0.64,
respectively). Fecal coliform bacteria in 0 to 5, 6 to 15, and 16 to 30 cm
of soil also correlated with temperature and moisture in a curvilinear
relationship (r 2 = 0.56 , 0.53, and 0.53, respectively)
The influence of vegetation in riparian filterstrips on coliform bacteria: I. Movement and survival in water
Swine (Sus scrofa) wastewater was applied to three separate 4 m
wide x 30 m long riparian filterstrips consisting of 20 m grass and
10 m forest, 10 m grass and 20 m forest, and 10 m grass and 20 m
maidencane (Panicum hemitomon Schult.) in Southern Georgia during
each season. Total and fecal coliform numbers in the applied
wastewater pulse did not decline as water moved downslope regardless
of vegetation type or season. The pulse of applied wastewater did
not move beyond 15 m in any treatment in autumn or summer (dry
seasons) and only moved beyond 7.5 m in the 20 m grass-10 m forest
treatment in the summer. Total and fecal coliform numbers in soil
water and shallow ground water declined by approximately 10-fold
every 7 d for the first 14 d regardless of vegetative treatment or season.
Soil temperature and soil moisture correlated with total coliform
bacteria in both 13 m wells (r2 = 0.89) and 2.0 m wells (r2 = 0.89),
and with fecal coliform bacteria in 1.5 (r2 = 0.82) and 2.0 m (r2 =
0.76) wells. Animal production operations may need to locate in
warm–dry climates so animal waste can be applied to lands to help
ensure enteric bacteria input to surface and ground water will not
occur
Influence of C02 enrichment and nitrogen fertilization on tissue chemistry and carbon allocation in longleaf pine seedlings
One-year old, nursery-grown longleaf pine (Pinus palustris Mill.) seedlings were grown in 45-L pots containing a
coarse sandy medium and were exposed to two concentrations of atmospheric CO2 (365 or 720 µmol?1) and two
levels of nitrogen (N) fertility (40 or 400 kg N ha?1 yr?1) within open top chambers for 20 months. At harvest,
needles, stems, coarse roots, and fine roots were separated and weighed. Subsamples of each tissue were frozen
in liquid N, lyophilized at ?50 ?C, and ground to pass a 0.2 mm sieve. Tissue samples were analyzed for carbon
(C), N, nonpolar extractives (fats, waxes, and oils = FWO), nonstructural carbohydrates (total sugars and starch),
and structural carbohydrates (cellulose, lignin, and tannins). Increased dry weights of each tissue were observed
under elevated CO2 and with high N; however, main effects of CO2 were significant only on belowground tissues.
The high N fertility tended to result in increased partitioning of biomass aboveground, resulting in significantly
lower root to shoot ratios. Elevated CO2 did not affect biomass allocation among tissues. Both atmospheric CO2
and N fertility tended to affect concentration of C compounds in belowground, more than aboveground, tissues.
Elevated CO2 resulted in lower concentrations of starch, cellulose, and lignin, but increased concentrations of
FWO in root tissues. High N fertility increased the concentration of starch, cellulose, and tannins, but resulted in
lower concentrations of lignin and FWO in roots. Differences between CO2 concentrations tended to occur only
with high N fertility. Atmospheric CO2 did not affect allocation patterns for any compound; however the high N
treatment tended to result in a lower percentage of sugars, cellulose, and lignin belowgroun
Litterfall, litter decomposition and associated nutrient fluxes in Pinus halepensis: influence of tree removal intensity in a Mediterranean forest
The online version of this
article (doi:10.1007/s10342-015-0893-z) contains supplementary
material, which is available to authorized users[EN] Our knowledge about the influence of silvicultural treatments on nutrient cycling processes in Mediterranean forests is still limited. Four levels of tree removal were compared in an Aleppo pine forest in eastern Spain to determine the effects on litterfall, litter decomposition and the associated nutrient fluxes after 12 years. Removal treatments included clearfelling, two shelterwood intensities (60 and 75 % of basal area removed) and untreated controls. Twelve years later, the basal area removed still explained 60 % of litterfall mass variance and 60 % of C, 52 % of N, 45 % of P, 17 % of K, 47 % of Ca and 60 % of Mg return variances. Litter decomposed somewhat more slowly in clearfellings compared to controls (p = 0.049), accumulated more Ca and released less K compared to the other three treatments. This was explained by contamination with mineral particles due to the poorly developed O horizon in clearfellings. We conclude that the management practices reduced the nutrient return via litterfall, but the nutrient release through decomposition seems poorly sensitive to canopy disturbance. In order to accurately quantify the harvesting impacts on nutrient cycling in this Mediterranean forest system, it is necessary to measure the litterfall of the understory layer.This work has been supported by a fellowship from the Generalitat Valenciana, Conselleria de Educacion, Formacion y Empleo awarded to L. Lado-Monserrat (BFPI/2008/041). Silvicultural treatments were carried out by the Mediterranean Centre for Environmental Studies (CEAM) through programme "I + D en relacion con la restauracion de la cubierta vegetal y otros aspectos de investigacion forestal". Dataloggers and probes were provided by the Generalitat Valenciana through Project "Efecto de diferentes sistemas de aclareo de masa forestal sobre la disponibilidad de agua, nutrientes y la regeneracion de la masa arborea y arbustiva en parcelas de pinar" (GV06/126). We acknowledge Joana Oliver, Ruth M. Tavera and Daniel Fortanet for their help in the laboratory and in the field. The authors wish to thank Francisco Galiana for his assistance, including help in fieldwork and providing information about the experimental design of the silvicultural treatments. Thanks also go to Rafael Herrera from the Centro de Ecologia, Instituto Venezolano de Investigaciones Cientificas, Caracas, Venezuela and two anonymous reviewers for critically reviewing the manuscript.Lado Monserrat, L.; Lidón, A.; Bautista, I. (2015). Litterfall, litter decomposition and associated nutrient fluxes in Pinus halepensis: influence of tree removal intensity in a Mediterranean forest. 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Effect of Biocontrol Agent Pseudomonas fluorescens 2P24 on Soil Fungal Community in Cucumber Rhizosphere Using T-RFLP and DGGE
Fungi and fungal community play important roles in the soil ecosystem, and the diversity of fungal community could act as natural antagonists of various plant pathogens. Biological control is a promising method to protect plants as chemical pesticides may cause environment pollution. Pseudomonas fluorescens 2P24 had strong inhibitory on Rastonia solanacearum, Fusarium oxysporum and Rhizoctonia solani, etc., and was isolated from the wheat rhizosphere take-all decline soils in Shandong province, China. However, its potential effect on soil fungal community was still unknown. In this study, the gfp-labeled P. fluorescens 2P24 was inoculated into cucumber rhizosphere, and the survival of 2P24 was monitored weekly. The amount decreased from 108 to 105 CFU/g dry soils. The effect of 2P24 on soil fungal community in cucumber rhizosphere was investigated using T-RFLP and DGGE. In T-RFLP analysis, principle component analysis showed that the soil fungal community was greatly influenced at first, digested with restriction enzyme Hinf I and Taq I. However, there was little difference as digested by different enzymes. DGGE results demonstrated that the soil fungal community was greatly shocked at the beginning, but it recovered slowly with the decline of P. fluorescens 2P24. Four weeks later, there was little difference between the treatment and control. Generally speaking, the effect of P. fluorescens 2P24 on soil fungal community in cucumber rhizosphere was just transient
Clustering of cancer among families of cases with Hodgkin Lymphoma (HL), Multiple Myeloma (MM), Non-Hodgkin's Lymphoma (NHL), Soft Tissue Sarcoma (STS) and control subjects
<p>Abstract</p> <p>Background</p> <p>A positive family history of chronic diseases including cancer can be used as an index of genetic and shared environmental influences. The tumours studied have several putative risk factors in common including occupational exposure to certain pesticides and a positive family history of cancer.</p> <p>Methods</p> <p>We conducted population-based studies of Hodgkin lymphoma (HL), Multiple Myeloma (MM), non-Hodgkin's Lymphoma (NHL), and Soft Tissue Sarcoma (STS) among male incident case and control subjects in six Canadian provinces. The postal questionnaire was used to collect personal demographic data, a medical history, a lifetime occupational history, smoking pattern, and the information on family history of cancer. The family history of cancer was restricted to first degree relatives and included relationship to the index subjects and the types of tumours diagnosed among relatives. The information was collected on 1528 cases (HL (n = 316), MM (n = 342), NHL (n = 513), STS (n = 357)) and 1506 age ± 2 years and province of residence matched control subjects. Conditional logistic regression analyses adjusted for the matching variables were conducted.</p> <p>Results</p> <p>We found that most families were cancer free, and a minority included two or more affected relatives. HL [(OR<sub>adj </sub>(95% CI) <b>1.79 (1.33, 2.42)]</b>, MM <b>(1.38(1.07, 1.78))</b>, NHL <b>(1.43 (1.15, 1.77)</b>), and STS cases <b>(1.30(1.00, 1.68)) </b>had higher incidence of cancer if any first degree relative was affected with cancer compared to control families. Constructing mutually exclusive categories combining "family history of cancer" (yes, no) and "pesticide exposure ≥10 hours per year" (yes, no) indicated that a positive family history was important for HL <b>(2.25(1.61, 3.15))</b>, and for the combination of the two exposures increased risk for MM <b>(1.69(1.14,2.51))</b>. Also, a positive family history of cancer both with <b>(1.72 (1.21, 2.45)) </b>and without pesticide exposure <b>(1.43(1.12, 1.83)) </b>increased risk of NHL.</p> <p>Conclusion</p> <p>HL, MM, NHL, and STS cases had higher incidence of cancer if any first degree relative affected with cancer compared to control families. A positive family history of cancer and/or shared environmental exposure to agricultural chemicals play an important role in the development of cancer.</p
Efeito da disponibilidade de água e de luz na colonização micorrízica e no crescimento de Tabebuia avellanedae Lorentz ex Griseb. (Bignoniaceae)
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