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71.
Plant biomass and plant abundance can be controlled by aboveground and belowground natural enemies. However, little is known about how the aboveground and belowground enemy effects may add up. We exposed 15 plant species to aboveground polyphagous insect herbivores and feedback effects from the soil community alone, as well as in combination. We envisaged three possibilities: additive, synergistic, or antagonistic effects of the aboveground and belowground enemies on plant biomass. In our analysis, we included native and phylogenetically related range-expanding exotic plant species, because exotic plants on average are less sensitive to aboveground herbivores and soil feedback than related natives. Thus, we examined if lower sensitivity of exotic plant species to enemies also alters aboveground-belowground interactions. In a greenhouse experiment, we exposed six exotic and nine native plant species to feedback from their own soil communities, aboveground herbivory by polyphagous insects, or a combination of soil feedback and aboveground insects and compared shoot and root biomass to control plants without aboveground and belowground enemies. We observed that for both native and range-expanding exotic plant species effects of insect herbivory aboveground and soil feedback added up linearly, instead of enforcing or counteracting each other. However, there was no correlation between the strength of aboveground herbivory and soil feedback. We conclude that effects of polyphagous aboveground herbivorous insects and soil feedback add up both in the case of native and related range-expanding exotic plant species, but that aboveground herbivory effects may not necessarily predict the strengths of soil feedback effects. 相似文献
72.
David A. DiCarlo Tim W. J. Bauters Christophe J. G. Darnault Eva Wong Barnes R. Bierck Tammo S. Steenhuis J. -Yves Parlange 《Journal of contaminant hydrology》2000,41(3-4)
Gravity-driven preferential flow (fingering) can greatly affect how one fluid displaces another in the subsurface. We have studied the internal properties of these preferential flow paths for water, with and without surfactants, infiltrating into oil saturated porous media using synchrotron X-rays, and miniature tensiometers to characterize fluid content and pressure relationships. We also used a light transmission technique to visualize overall flow pattern. Capillary pressure and water content decrease behind the front, similar to fingers in air-dry sand, with quantitative differences for five different surfactants with surface tensions ranging from 4–21 g/s2. Using unstable flow theory, the finger widths, capillary pressure drops within the fingers, finger tip lengths, and finger splitting dynamics were scaled successfully with interfacial tension, fluid density, and the contact angle using the fingers in air–water systems as the reference. 相似文献
73.
This study examined trends along a gradient of fishing intensity in an artisanal coral reef fishery over a 10-year period along 75 km of Kenya's most populated coastline. As predicted by Malthusian scenarios, catch per unit effort (CPUE), mean trophic level, the functional diversity of fished taxa, and the diversity of gear declined, while total annual catch and catch variability increased along the fishing pressure gradient. The fishery was able to sustain high (approximately 16 Mg x km(-2) x yr(-1)) but variable yields at high fishing pressure due to the dominance of a few productive herbivorous fish species in the catch. The effect of two separate management strategies to overcome this Malthusian pattern was investigated: fisheries area closure and elimination of the dominant and most "competitive" gear. We found that sites within 5 km of the enforced closure showed significantly lower total catch and CPUE, but increased yield stability and trophic level of catch than predicted by regression models normalized for fishing effort. Sites that had excluded illegal beach seine use through active gear management exhibited increased total catch and CPUE. There was a strong interaction between closure and gear management, which indicates that, for closures to be effective at increasing catch, there must be simultaneous efforts at gear management around the periphery of the closures. We propose that Malthusian effects are responsible for the variation in gear and catch and that active management through reduced effort and reductions in the most competitive gear have the greatest potential to increase the functional and trophic diversity and per-person productivity. 相似文献
74.
Using Ion-Exchange Resins to Study Soil Response to Experimental Watershed Acidification 总被引:1,自引:0,他引:1
Szillery JE Fernandez IJ Norton SA Rustad LE White AS 《Environmental monitoring and assessment》2006,116(1-3):383-398
Ion-exchange resins (IER) offer alternative approaches to measuring ionic movement in soils that may have advantages over
traditional approaches in some settings, but more information is needed to understand how IER compare with traditional methods
of measurement in forested ecosystems. At the Bear Brook Watershed in Maine (BBWM), one of two paired, forested watersheds
is treated bi-monthly with S and N (28.8 and 25.2kgha−1yr−1 of S and N, respectively). Both IER and ceramic cup tension lysimeters were used to study soil solution responses after ∼11
years of treatment. Results from both methods showed treatments resulted in the mobilization of base cations and Al, and higher
SO4—S and inorganic N in the treated watershed. Both methods indicated similar differences in results associated with forest
type (hardwoods versus softwoods), a result of differences in litter quality and atmospheric aerosol interception capacity.
The correlation between lysimeter and IER data for individual analytes varied greatly. Significant correlations were evident
for Na (r=0.75), Al (r=0.65), Mn (r=0.61), Fe (r=0.57), Ca (r=0.49), K (r=0.41) and NO3—N (r=0.59). No correlation was evident between IER and soil solution data for NH4—N and Pb. Both IER and soil solution techniques suggested similar interpretations of biogeochemical behavior in the watershed. 相似文献
75.
Robyn E. Tuerena Claire Mahaffey Sian F. Henley Camille de la Vega Louisa Norman Tim Brand Tina Sanders Margot Debyser Kirstin Dhnke Judith Braun Christian Mrz 《Ambio》2022,51(2):355
Climate change is altering nutrient cycling within the Arctic Ocean, having knock-on effects to Arctic ecosystems. Primary production in the Arctic is principally nitrogen-limited, particularly in the western Pacific-dominated regions where denitrification exacerbates nitrogen loss. The nutrient status of the eastern Eurasian Arctic remains under debate. In the Barents Sea, primary production has increased by 88% since 1998. To support this rapid increase in productivity, either the standing stock of nutrients has been depleted, or the external nutrient supply has increased. Atlantic water inflow, enhanced mixing, benthic nitrogen cycling, and land–ocean interaction have the potential to alter the nutrient supply through addition, dilution or removal. Here we use new datasets from the Changing Arctic Ocean program alongside historical datasets to assess how nitrate and phosphate concentrations may be changing in response to these processes. We highlight how nutrient dynamics may continue to change, why this is important for regional and international policy-making and suggest relevant research priorities for the future.Supplementary InformationThe online version contains supplementary material available at 10.1007/s13280-021-01673-0. 相似文献
76.
In situ ammonia removal in bioreactor landfill leachate 总被引:11,自引:0,他引:11
Although bioreactor landfills have many advantages associated with them, challenges remain, including the persistence of NH(3)-N in the leachate. Because NH(3)-N is both persistent and toxic, it will likely influence when the landfill is biologically stable and when post-closure monitoring may end. An in situ nitrogen removal technique would be advantageous. Recent studies have shown the efficacy of such processes; however, they are lacking the data required to enable adequate implementation at field-scale bioreactor landfills. Research was conducted to evaluate the kinetics of in situ ammonia removal in both acclimated and unacclimated wastes to aid in developing guidance for field-scale implementation. Results demonstrate that in situ nitrification is feasible in an aerated solid waste environment and that the potential for simultaneous nitrification and denitrification (even under low biodegradable C:N conditions) in field-scale bioreactor landfills is significant due to the presence of both aerobic and anoxic areas. All rate data fit well to Monod kinetics, with specific rates of removal of 0.196 and 0.117 mgN/day-g dry waste and half-saturation constants of 59.6 and 147 mgN/L for acclimated and unacclimated wastes, respectively. Although specific rates of ammonia removal in the unacclimated waste are lower than in the acclimated waste, a relatively quick start-up of ammonia removal was observed in the unacclimated waste. Using the removal rate expressions developed will allow for estimation of the treatment times and volumes necessary to remove NH(3)-N from recirculated landfill leachate. 相似文献
77.
78.
Miller JJ Olson EC Chanasyk DS Beasley BW Yanke LJ Larney FJ McAllister TA Olson BM Selinger LB 《Journal of environmental quality》2006,35(2):505-515
Soluble salts, nutrients, and pathogenic bacteria in feedlot-pen runoff have the potential to cause pollution of the environment. A 2-yr study (1998-1999) was conducted at a beef cattle (Bos taurus) feedlot in southern Alberta, Canada, to determine the effect of bedding material [barley (Hordeum vulgare L.) straw versus wood chips] and within-pen location on the chemical and bacterial properties of pen-floor runoff. Runoff was generated with a portable rainfall simulator and analyzed for chemical content (nitrogen [N], phosphorus [P], soluble salts, electrical conductivity [EC], sodium adsorption ratio [SAR], dissolved oxygen [DO], and pH) and populations of three groups of bacteria (Escherichia coli, total coliforms, total aerobic heterotrophs at 27 degrees C) in 1998 and 1999. Bedding had a significant (P < or = 0.05) effect on NH4-N concentration and load in 1999, SO4 load in 1998, SO4 concentration and load in 1999, and total coliforms in both years; where these three variables were higher in wood than straw pens. Location had a significant effect on EC and concentrations of total Kjeldahl nitrogen (TKN), Na, K, SO4, and Cl in 1998, and total coliforms in both years. These seven variables were higher at the bedding pack than pen floor location, indicating that bedding packs were major reservoirs of TKN, soluble salts, and total coliforms. Significantly higher dissolved reactive phosphorus (DRP), total P, and NH4-N concentrations and loads at the bedding pack location in wood pens in 1998, and a similar trend for TKN concentration in 1999, indicated that this bedding-location treatment was a greater source of nutrients to runoff than the other three bedding-location treatments. Bedding, location, and their interaction may therefore be a potential tool to manage nutrients, soluble salts, and bacteria in feedlot runoff. 相似文献
79.
Jonathan M. H. Green Gemma R. Cranston William J. Sutherland Hannah R. Tranter Sarah J. Bell Tim G. Benton Eva Blixt Colm Bowe Sarah Broadley Andrew Brown Chris Brown Neil Burns David Butler Hannah Collins Helen Crowley Justin DeKoszmovszky Les G. Firbank Brett Fulford Toby A. Gardner Rosemary S. Hails Sharla Halvorson Michael Jack Ben Kerrison Lenny S. C. Koh Steven C. Lang Emily J. McKenzie Pablo Monsivais Timothy O’Riordan Jeremy Osborn Stephen Oswald Emma Price Thomas David Raffaelli Belinda Reyers Jagjit S. Srai Bernardo B. N. Strassburg David Webster Ruth Welters Gail Whiteman James Wilsdon Bhaskar Vira 《Sustainability Science》2017,12(2):319-331
Delivering access to sufficient food, energy and water resources to ensure human wellbeing is a major concern for governments worldwide. However, it is crucial to account for the ‘nexus’ of interactions between these natural resources and the consequent implications for human wellbeing. The private sector has a critical role in driving positive change towards more sustainable nexus management and could reap considerable benefits from collaboration with researchers to devise solutions to some of the foremost sustainability challenges of today. Yet opportunities are missed because the private sector is rarely involved in the formulation of deliverable research priorities. We convened senior research scientists and influential business leaders to collaboratively identify the top forty questions that, if answered, would best help companies understand and manage their food-energy-water-environment nexus dependencies and impacts. Codification of the top order nexus themes highlighted research priorities around development of pragmatic yet credible tools that allow businesses to incorporate nexus interactions into their decision-making; demonstration of the business case for more sustainable nexus management; identification of the most effective levers for behaviour change; and understanding incentives or circumstances that allow individuals and businesses to take a leadership stance. Greater investment in the complex but productive relations between the private sector and research community will create deeper and more meaningful collaboration and cooperation. 相似文献
80.
Annemieke Farenhorst Inoka Amarakoon Lindsey Andronak 《Journal of environmental science and health. Part. B》2017,52(8):564-569
Mineralization studies of natural steroid hormones (e.g., 17β-estradiol, E2) are performed in environmental incubators, usually under a constant temperature such as 20°C. In this paper, we present a microcosm protocol that quantified the mineralization of E2 in soils under field temperatures. The nine agricultural soils tested had a wide range of soil organic carbon (1.1 to 5.2%) and clay (9 to 57%) contents. The calculated time over which half of the applied E2 was mineralized (E2-½) ranged from 299 to 910 d, and total E2 mineralization at 48 d (E2-TOT48) ranged from 4 to 13%. In subsequent laboratory incubations, the same soils were incubated under a constant temperature of 20°C, as well as under cyclic temperatures of 14.5°C (14 h) and 11.5°C (10h), which was within the temperature extremes observed in the field microcosms. E2-½ ranged from 157 to 686 d at 20°C and from 103 to 608 d at the cyclic temperatures, with the E2-TOT48 ranging from 6 to 21% at 20°C and from 7 to 30% under cyclic temperatures. Despite the overall 6.75°C lower mean temperatures under the cyclic versus constant temperatures, E2 mineralization was stimulated by the temperature cycles in three soils. Regardless of the incubation, the same loamy sand soil always showed larger E2 mineralization than the other eight soils and this loamy sand soil also had the smallest E2 sorption. Current modeling approaches do not take into consideration the effects of temperature fluctuations in the field because the input parameters used to describe degradation are derived from laboratory incubations at a constant temperature. Across the eight soils, E2-½ was on average 1.7 times larger and E2-TOT48 was on average 0.8 times smaller under field temperatures than under a constant 20°C. Hence, we conclude that incubations at 20°C give a reasonable representation of E2 mineralization occurring under field conditions to be expected in a typical Prairie summer season. 相似文献