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PubMed2002

The fate of diesel hydrocarbons in soils and their effect on the germination of perennial ryegrass.

Hydrocarbon contamination in soils may be toxic to plants and soil microorganisms and act as a source of groundwater contamination. The objective of this study was to evaluate the fate of diesel in soils with or without added nutrients. The soils examined either had or had not a previous history of hydrocarbon contamination. Particular aspects examined were soil respiration, changes in microbial population, breakdown of diesel hydrocarbons, and phytotoxicity to the germination of perennial ryegrass. Soil respiration was measured as evolved CO2. Bacterial population was determined as colony forming units in dilution plates and fungal activity was measured as hyphal length. The fate of individual hydrocarbons was determined by gas chromatography-mass spectrometry after extraction with dichloromethane. When diesel was added to soil with no previous history of hydrocarbon contamination at rates up to 50 mg/g, the respiration response showed a lag phase of 6 days and maximum respiration occurred at day 11. The lag phase was 2 days and maximum respiration occurred at day 3 in soil with a previous history of hydrocarbon contamination. After the peak, respiration decreased up to about 20 days in both soils. Thereafter, respiration become more or less constant but substantially greater than the control. N and P addition along with diesel did not reduce the lag phase but increased the respiration over the first 20 days of incubation. Diesel addition with or without N and P increased the bacterial population 10- to 100-fold but fungal hyphal length did not increase. Diesel addition at a rate of 136 mg/g did not increase the microbial population. Removal of inhibition to germination of perennial ryegrass was linked to the decomposition of nC10 and nC11 hydrocarbons and took from 11 to 30 days at diesel additions up to 50 mg/g depending on the soil. Inhibition to germination of perennial ryegrass persisted to more than 24 weeks at the 136 mg/g of diesel addition.

Carbon Dioxide↗
PubMed2006

Size and structure of bacterial, fungal and nematode communities along an Antarctic environmental gradient.

The unusually harsh environmental conditions of terrestrial Antarctic habitats result in ecosystems with simplified trophic structures, where microbial processes are especially dominant as drivers of soil-borne nutrient cycling. We examined soil-borne Antarctic communities (bacteria, fungi and nematodes) at five locations along a southern latitudinal gradient from the Falkland Islands (51 degrees S) to the base of the Antarctic Peninsula (72 degrees S), and compared principally vegetated vs. fell-field locations at three of these sites. Results of molecular (denaturing gradient gel electrophoresis, real-time PCR), biochemical (ergosterol, phospholipid fatty acids) and traditional microbiological (temperature- and medium-related CFU) analyses were related to key soil and environmental properties. Microbial abundance generally showed a significant positive relationship with vegetation and vegetation-associated soil factors (e.g. water content, organic C, total N). Microbial community structure was mainly related to latitude or location and latitude-dependent factors (e.g. mean temperature, NO3, pH). Furthermore, strong interactions between vegetation cover and location were observed, with the effects of vegetation cover being most pronounced in more extreme sites. These results provide insight into the main drivers of microbial community size and structure across a range of terrestrial Antarctic and sub-Antarctic habitats, potentially serving as a useful baseline to study the impact of predicted global warming on these unique and pristine ecosystems.

Animals↗
PubMed1980

Influence of soil on wood-degradation and fruit body formation by parasites and saprophytes among wood-destroying basidiomycetous fungi.

Formation of soil mycelium enables the fungal mycelium to amend the nutrient-deficient wood substrate actively by enclosing macronutrients from soil. Supposition to formation of a soil mycelium proved the resistance of the fungus to competitive substrate microorganisms. This resistance is absent in pathogenic, but wide-spread in saprophytic wood-decay fungi. Consequently, production of soil mycelium was restricted to saprophytic fungi. Saprophytes of the white-rot type are superior to brown-cubical rot type fungi in forming soil mycelium and utilizing soil nutrients. However, rich soils stimulate a more limited degree of wood degradation and yield increase of basidiocarps in parasitic fungi, too, that fail to produce a soil mycelium. It is concluded that uptake of soil nutrients turns out in two different ways, via an actively absorbing soil mycelium and via passive nutrient diffusion from soil into the substrate wood.

Antibiosis↗
PubMed1990

Nutrient accumulation in trees and soil following irrigation with municipal effluent in Australia.

Irrigation of tree crops is being evaluated as a method of land disposal of municipal effluent in Australia. A study was carried out from 1980-84 in which seven tree species were sprinkler-irrigated with effluent at an annual rate of 1191-1752 mm. Effective weed control and frequent irrigation resulted in good survival of all species (range 83-100%) at 12 months. Total productivity was estimated at age 4 years by measuring biomass of each species inclusive of litter and roots to a soil depth of 80 cm. Biomass production of the high-yielding species, flooded gum (Eucalyptus grandis) and Sydney blue gum (E. saligna), was around 10 kg m(-2). Percentage leaf mass of these species was small (8-9%) compared with 25% and 29% for the relatively slow-growing river she-oak (Casuarina cunninghamiana) and radiata pine (Pinus radiata). Accumulation of nutrients in the total biomass differed significantly between species and ranged from 34-54 g m(-2) for nitrogen, 4.0-10.4 g m(-2) for phosphorus, 2.1-12.2 g m(-2) for sodium, 22-34 g m(-2) for potassium, 12-61 g m(-2) for calcium and 4.7-9.3 g m(-2) for magnesium. River she-oak and river red gum (E. camaldulensis), because of their relatively large crown and litter masses, accumulated more nitrogen, phosphorus, potassium and calcium than flooded gum or Sydney blue gum. Chemical properties of soils (0-150 cm) were measured in 1980 and again in 1984. Irrigation significantly increased pH (by around 1 unit), throughout the profile. Concentrations of total phosphorus, and exchangeable sodium, calcium and magnesium were increased in the upper profile. Overall, soil chemical properties were not adversely affected by effluent irrigation over the 4-year period, though there was a trend towards more sodic conditions in the soil profile. Nutrient accumulation in soil occurred mainly in the 0-35 cm depth, coinciding with the main root zone of the trees. Renovation of the effluent was therefore estimated as the amount of each nutrient accumulated in the biomass (averaged over the seven species) plus soil (0-35 cm), expressed as a percentage of amount applied in irrigation over the 4 years; that is, nitrogen, 29%; phosphorus, 78%; sodium, 15%; potassium, 26%; calcium, 98% and magnesium, 54%.

Journal Article↗
PubMed2005

Supply pre-emption, not concentration reduction, is the mechanism of competition for nutrients.

Concentration reduction theory is the leading theory regarding the mechanism of competition for nutrients in soils among plants, yet it has not been rigorously tested. Here we used a spatially explicit, fine-scale grid-based model that simulated diffusion and plant uptake of nutrients by plants in soil to test whether concentration reduction theory was appropriate for terrestrial plant competition for nutrients. In the absence of competition, increasing the rate of diffusion allows a plant to maintain positive growth rates below the lowest average concentration to which it can reduce nutrients in soil solution (R*). As such, differences among plants in the reduction of soil moisture, which here primarily affects nutrient diffusion, can cause R* to predict competitive success incorrectly. The stronger competitor for nutrients captures the largest proportion of the nutrient supply by ensuring nutrients contact its roots before those of a competitor. Although the metric derived from concentration reduction theory, R*, might have predictive power for competitive outcomes in terrestrial ecosystems, this evidence suggests that plants outcompete other plants for nutrients by pre-empting the supply, not reducing the average concentration.

Computer Simulation↗
PubMed2002

The influence of the forest canopy on nutrient cycling.

Rates of key soil processes involved in recycling of nutrients in forests are governed by temperature and moisture conditions and by the chemical and physical nature of the litter. The forest canopy influences all of these factors and thus has a large influence on nutrient cycling. The increased availability of nutrients in soil in clearcuts illustrates how the canopy retains nutrients (especially N) on site, both by storing nutrients in foliage and through the steady input of available C in litter. The idea that faster decomposition is responsible for the flush of nitrate in clearcuts has not been supported by experimental evidence. Soil N availability increases in canopy gaps as small as 0.1 ha, so natural disturbances or partial harvesting practices that increase the complexity of the canopy by creating gaps will similarly increase the spatial variability in soil N cycling and availability within the forest. Canopy characteristics affect the amount and composition of leaf litter produced, which largely determines the amount of nutrients to be recycled and the resulting nutrient availability. Although effects of tree species on soil nutrient availability were thought to be brought about largely through differences in the decomposition rate of their foliar litter, recent studies indicate that the effect of tree species can be better predicted from the mass and nutrient content of litter produced, hence total nutrient return, than from litter decay rate. The greater canopy complexity in mixed species forests creates similar heterogeneity in nutritional characteristics of the forest floor. Site differences in slope position, parent material and soil texture lead to variation in species composition and productivity of forests, and thus in the nature and amount of litter produced. Through this positive feedback, the canopy accentuates inherent differences in site fertility.

Biomass↗
PubMed2002

Stratification and seasonal stability of diverse bacterial communities in a Pinus merkusii (pine) forest soil in central Java, Indonesia.

In Java, Indonesia, many nutrient-poor soils are intensively reforested with Pinus merkusii (pine). Information on nutrient cycles and microorganisms involved in these cycles will benefit the management of these important forests. Here, seasonal effects on the stratification of bacterial community structure in the soil profile of a tropical pine forest are described, and differences in bacterial communities are related to chemical and physical soil parameters. Culture-independent community profiles of litter, fragmented litter and mineral soil layers were made by denaturing gradient gel electrophoresis (DGGE) of 16S rDNA-specific polymerase chain reaction (PCR) fragments. The community profiles of the different soil layers clustered separately, correlating with significant differences in organic matter content between the three layers. The bacterial communities appeared to be stable during the wet season of 1998. The drought in 1997, caused by the El Niño climatic effect, did not influence the bacterial communities in fragmentation and mineral soil, although moisture content and other soil parameters were markedly lower than in the wet season. However, communities in litter were influenced by drought. In the litter layer, the moisture content was significantly lower than in the fragmentation and mineral layers during the dry season. A clone library was made from a litter sample taken during the wet season. Partial sequencing of 74 clones and linking the DGGE banding positions of these clones to bands in the DGGE profile of the sample from which the clone library was derived showed considerable bacterial diversity. Alpha-proteobacteria (40.5% of the clones, of which 57% belonged to the Rhizobium-Agrobacterium group) and high-G+C content, Gram-positive bacteria (36.5%) dominated the clone library.

Bacteria↗
PubMed2003

Urbanization effects on tree growth in the vicinity of New York City.

Plants in urban ecosystems are exposed to many pollutants and higher temperatures, CO2 and nitrogen deposition than plants in rural areas. Although each factor has a detrimental or beneficial influence on plant growth, the net effect of all factors and the key driving variables are unknown. We grew the same cottonwood clone in urban and rural sites and found that urban plant biomass was double that of rural sites. Using soil transplants, nutrient budgets, chamber experiments and multiple regression analyses, we show that soils, temperature, CO2, nutrient deposition, urban air pollutants and microclimatic variables could not account for increased growth in the city. Rather, higher rural ozone (O3) exposures reduced growth at rural sites. Urban precursors fuel the reactions of O3 formation, but NO(x) scavenging reactions resulted in lower cumulative urban O3 exposures compared to agricultural and forested sites throughout the northeastern USA. Our study shows the overriding effect of O3 despite a diversity of altered environmental factors, reveals 'footprints' of lower cumulative urban O3 exposures amidst a background of higher regional exposures, and shows a greater adverse effect of urban pollutant emissions beyond the urban core.

Air Pollutants↗
PubMed1993

Nitrogen limitation and nitrogen fixation during alkane biodegradation in a sandy soil.

We investigated nutrient limitations during hydrocarbon degradation in a sandy soil and found that fixed nitrogen was initially a limiting nutrient but that N limitation could sometimes be overcome by N2 fixation. Hydrocarbon biodegradation was examined in an unsaturated sandy soil incubated aerobically at 20 degrees C with propane or butane and various added nutrients. Propane and butane degradation proceeded similarly during the first 3 months of incubation. That is, bacteria in soil amended with N oxidized these hydrocarbons more rapidly than in controls without nutrient additions or in soil with added phosphate or trace minerals. Both propane- and butane-amended soil apparently became N limited after the initial available inorganic N was utilized, as indicated by a decrease in the rates of hydrocarbon degradation. After 3 months, propane and butane degradation proceeded differently. Bacteria in propane-degrading soil apparently remained N limited because propane degradation rates stayed low unless more N was added. In contrast, bacteria in butane-degrading soil appeared to overcome their N limitation because butane degradation rates later increased regardless of whether more N was added. Analyses of total N and acetylene reduction assays supported this apparent surplus of N in butane-amended soil. Total N was significantly (P < 0.01) higher in soil incubated with butane and no N amendments than in soil incubated with propane, even when the latter was amended with N. Acetylene reduction occurred only in butane-amended soil. These results indicate that N2 fixation occurred in butane-amended soil but not in propane-amended soil.

Acetylene↗
PubMed2002

[Difference of several major nutrients accumulation in vegetable and cereal crop soils].

Investigation and determination of several major nutrients in different types of vegetable and cereal crop soils were carried out in the Guanzhong Plain in Shaanxi Province. The results showed that organic matter, nitrogen, phosphorus and potassium accumulated more in the 0-200 cm profile of vegetable soils than in that of cereal crop soils. However, the accumulation degrees were different with different nutrient forms. The total amount of nitrate-N in the soil profile of plastic greenhouse and usual vegetable field was 1520.9 kg.hm-2 and 1358.8 kg.hm-2, being 5.2 and 4.5 times higher than that in the cereal crop fields respectively. The total amount of available-P was respectively 978.1 kg.hm-2 and 503.3 kg.hm-2 in the two vegetable soils, and 136.2 kg.hm-2 in cereal crop soils, and the former two were 6.2 and 2.7 times higher than the latter. For other nutrients, organic matter in cereal crop soil was 249.4 Mg.hm-2, and that in plastic greenhouse and usual vegetable soil was 280.5 Mg.hm-2 and 269.3 Mg.hm-2, respectively, which were only 12.5% and 8.0% higher than that in cereal crop soils. The total-N in plastic greenhouse and usual vegetable soils was 37.5 Mg.hm-2 and 32.7 Mg.hm-2, which was 36.2% and 18.6% higher than that (27.5 Mg.hm-2) in cereal crop soils, respectively. The ammonium-N was 211.5 kg.hm-2 and 197.8 kg.hm-2, which was 29.6% and 21.2% higher than that (163.2 kg.hm-2) in cereal crop soils. The available-K was 6567.8 kg.hm-2 and 5523.6 kg.hm-2, which was 30.6% and 9.8% higher than that (5029.7 kg.hm-2) in cereal crop soils. Furthermore, serious nutrient leaching occurred in vegetable soil profiles due to over-fertilization and irrigation.

Agriculture↗
PubMed2004

Implications of rhizospheric heavy metals and nutrients for the growth of alfalfa in sludge amended soil.

Rhizospheric distribution of nutrients and heavy metals in sludge amended soil was investigated using the rhizobag technique to give an indication of the release of metals from wastewater sludge. DTPA-extractable Zn, Cd, Ni and Mn, and available P, K and NH4+-N in the rhizosphere were markedly depleted when soil was amended with sludge. There was no conspicuous depletion or accumulation of DTPA-extractable Cu in the rhizosphere when the soil was amended with sewage sludge but DTPA-extractable Fe accumulated in the rhizosphere when the soil was amended with increasing amounts of sludge. The pH value in the rhizosphere increased with distance from the roots when soil was amended with larger amounts of sludge. The exchangeable fraction of Cu in the rhizosphere was depleted whether or not the soil was treated with sludge. Carbonate, oxide, organic and residual fractions of Cu and Zn were depleted in the rhizosphere at a distance of 0-2 mm from the roots when soil was amended with 50% sludge. Application of sewage sludge had a positive effect on alfalfa growth. With an increase in sludge amounts, the concentrations of Fe, Cu and Zn in alfalfa shoots did not change. Soil amendments with less than 25% sludge did not increase the availability or mobility of heavy metals. The depletion in rhizospheric DTPA-extractable Zn, Cd and Ni indicates that with the sole exception of Cu, release of metals from sludge amended soil was very limited.

Analysis of Variance↗
PubMed2006

Relationship between crown condition and tree diameter growth in southern Swedish oaks.

We studied correlation between crown conditions and tree-ring widths in 260 trees of pedunculate oak (Quercus robur L.) growing on 33 sites in southern Sweden. The tree-ring increment over 1998-2002 was highest in trees with healthy crowns, intermediate in trees with moderately declined crowns, and lowest in trees with heavily declining crowns. The time period with significant correlation between crown status and tree-ring increment varied between 10 years (given autocorrelation in tree-ring chronologies preserved) and 4 years (autocorrelation removed). In pairwise comparisons of three crown classes, differences in tree-ring increment between trees with healthy crowns and trees with heavily declining crowns were the most pronounced, Fisher LSD P value staying below 0.05 over 13 years (autocorrelation preserved ) or 4 years (autocorrelation removed). Over two 5-year periods (1993-1997 vs. 1998-2002) the cumulative increment increased significantly for trees with healthy crowns, did not change in trees with moderately declining crowns, and significantly decreased in trees with heavily declining crowns. For trees with healthy crowns, this dynamics may represent growth recovery after 1992 drought. Instead, oaks with defoliation above 60% appear to reach a threshold in their ability to recover growth. At sites on nutrient-poor soils cumulative increments over 1998-2002 differed significantly among trees with different crown condition and no differences were observed at sites on nutrient-rich soils. Analyses and interpretation of the oak growth trends as recovered from tree-ring chronologies may be improved by controlling for the crown status of the trees sampled, e.g., by using sampling strategy that would represent the average crown and growth conditions of the sites.

Disasters↗
PubMed2004

Nutrient loss and water quality under extensive grazing in the upper Burdekin river catchment, North Queensland.

Increased sediment and nutrient losses resulting from unsustainable grazing management in the Burdekin River catchment are major threats to water quality in the Great Barrier Reef Lagoon. To test the effects of grazing management on soil and nutrient loss, five 1 ha mini-catchments were established in 1999 under different grazing strategies on a sedimentary landscape near Charters Towers. Reference samples were also collected from watercourses in the Burdekin catchment during major flow events. Soil and nutrient loss were relatively low across all grazing strategies due to a combination of good cover, low slope and low rainfall intensities. Total soil loss varied from 3 to 20 kg ha(-1) per event while losses of N and P ranged from 10 to 1900 g ha(-1) and from 1 to 71 g ha(-1) per event respectively. Water quality of runoff was considered moderate across all strategies with relatively low levels of total suspended sediment (range: 8-1409 mg l(-1)), total N (range: 101-4000 microg l(-1)) and total P (range: 14-609 microg l(-1)). However, treatment differences are likely to emerge with time as the impacts of the different grazing strategies on land condition become more apparent. Samples collected opportunistically from rivers and creeks during flow events displayed significantly higher levels of total suspended sediment (range: 10-6010 mg l(-1)), total N (range: 650-6350 microg l(-1)) and total P (range: 50-1500 microg l(-1)) than those collected at the grazing trial. These differences can largely be attributed to variation in slope, geology and cover between the grazing trial and different catchments. In particular, watercourses draining hillier, grano-diorite landscapes with low cover had markedly higher sediment and nutrient loads compared to those draining flatter, sedimentary landscapes. These preliminary data suggest that on relatively flat, sedimentary landscapes, extensive cattle grazing is compatible with achieving water quality targets, provided high levels of ground cover are maintained. In contrast, sediment and nutrient loss under grazing on more erodable land types is cause for serious concern. Long-term empirical research and monitoring will be essential to quantify the impacts of changed land management on water quality in the spatially and temporally variable Burdekin River catchment.

Animal Husbandry↗
PubMed2001

Influence of different organic waste materials on the transformation of nitrogen in soils.

Organic waste materials like crop residues, well-decomposed cow dung, composts, and other rural and urban wastes are considered highly useful resources in enhancing soil fertility and also in build-up of soil organic matter. Organic matter decomposition provides plant nutrients in soil, which in turn increases crop productivity. Availability of nutrients and nitrogen (N) and phosphorus from organic waste materials is dependent upon the nature of organic residues, climatic conditions, and soil moisture activity. Keeping these factors in view, the present investigation was undertaken to study the transformation of N from different organic waste materials in two contrasting soils from an eastern India, subtropical region. The results showed that the amounts of ammoniacal-N (NH4-N), nitrate-N (NO3-N), hydrolysable N (HL-N), and nonhydrolysable (NHL-N) were increased for up to 60 days of soil submergence and increased further with the increase (1% by weight of soil) of organic residue application. Considering the effect of various organic waste materials, it was found that the amounts of NH4-N, NO3-N, HL-N, and NHL-N were higher with the application of groundnut hull as compared to wheat straw and potato skin, which may be due to relatively narrow carbon:N ratio of groundnut (22:43) than that of wheat straw (62:84) and potato skin (71:32); however, the results showed that the release of NH4-N, NO3-N, HL-N, and NHL-N was in the order of groundnut hull > wheat straw > potato skin.

Animals↗
PubMed2006

A conceptual model for the development of Phytophthora disease in Quercus robur.

Here, a conceptual model is presented for the development of Phytophthora disease in pedunculate oak. The model is presented using the causal loop diagram tool and gives an overview of how various abiotic and biotic factors, such as soil moisture, nutrient availability and mycorrhizal colonization, may affect the reproduction and the infective capacity of soil-borne Phytophthora species, the susceptibility of the host and subsequent disease development. It is suggested that the link between the root damage caused by Phytophthora species and overall tree vitality is in the assimilation and allocation of carbon within the plants. The potential impact of environmental factors on these processes is discussed. The model is presented with reference to scenarios related to variation in soil moisture and nutrient availability. The need for species-specific validation of the model and the implications of the model are discussed.

Carbon↗
PubMed2006

[Interrelations between plant communities and environmental factors of wetlands and surrounding lands in mid- and lower reaches of Tarim River].

A total of 16 quadrants of wetlands and surrounding lands in the mid- and lower reaches of Tarim River were surveyed, and the data about the characteristics of plant communities and environmental factors were collected and counted. By using PCA (principal component analysis) ordination and regression procedure, the distribution patterns of plant communities and the relationships between the characteristics of plant community structure and environmental factors were analyzed. The results showed that the distribution of the plant communities was closely related to soil moisture, salt, and nutrient contents. The accumulative contribution rate of soil moisture and salt contents in the first principal component accounted for 35.70%, and that of soil nutrient content in the second principal component reached 25.97%. There were 4 types of habitats for the plant community distribution, i. e., fenny--light salt--medium nutrient, moist--medium salt--medium nutrient, mesophytic--medium salt--low nutrient, and medium xerophytic-heavy salt--low nutrient. Along these habitats, swamp vegetation, meadow vegetation, riparian sparse forest, halophytic desert, and salinized shrub were distributed. In the wetlands and surrounding lands of mid- and lower reaches of Tarim River, the ecological dominance of the plant communities was markedly and unitary-linearly correlated with the compound gradient of soil moisture and salt contents. The relationships between species diversity, ecological dominance, and compound gradient of soil moisture and salt contents were significantly accorded to binary-linear regression model.

Biodiversity↗