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121.
Novel weapons: invasive plant suppresses fungal mutualists in America but not in its native Europe 总被引:7,自引:0,他引:7
Callaway RM Cipollini D Barto K Thelen GC Hallett SG Prati D Stinson K Klironomos J 《Ecology》2008,89(4):1043-1055
Why some invasive plant species transmogrify from weak competitors at home to strong competitors abroad remains one of the most elusive questions in ecology. Some evidence suggests that disproportionately high densities of some invaders are due to the release of biochemicals that are novel, and therefore harmful, to naive organisms in their new range. So far, such evidence has been restricted to the direct phytotoxic effects of plants on other plants. Here we found that one of North America's most aggressive invaders of undisturbed forest understories, Alliaria petiolata (garlic mustard) and a plant that inhibits mycorrhizal fungal mutualists of North American native plants, has far stronger inhibitory effects on mycorrhizas in invaded North American soils than on mycorrhizas in European soils where A. petiolata is native. This antifungal effect appears to be due to specific flavonoid fractions in A. petiolata extracts. Furthermore, we found that suppression of North American mycorrhizal fungi by A. petiolata corresponds with severe inhibition of North American plant species that rely on these fungi, whereas congeneric European plants are weakly affected. These results indicate that phytochemicals, benign to resistant mycorrhizal symbionts in the home range, may be lethal to na?ve native mutualists in the introduced range and indirectly suppress the plants that rely on them. 相似文献
122.
Rai Bina Mercurio Steven Don 《Environmental science and pollution research international》2020,27(10):10629-10641
Environmental Science and Pollution Research - Carbendazim and thiram are fungicides used in combination to prevent mold destruction of crops. Studies have demonstrated genotoxicity by these... 相似文献
123.
Untangling the proximate causes and underlying drivers of deforestation and forest degradation in Myanmar 总被引:1,自引:0,他引:1
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Political transitions often trigger substantial environmental changes. In particular, deforestation can result from the complex interplay among the components of a system—actors, institutions, and existing policies—adapting to new opportunities. A dynamic conceptual map of system components is particularly useful for systems in which multiple actors, each with different worldviews and motivations, may be simultaneously trying to alter different facets of the system, unaware of the impacts on other components. In Myanmar, a global biodiversity hotspot with the largest forest area in mainland Southeast Asia, ongoing political and economic reforms are likely to change the dynamics of deforestation drivers. A fundamental conceptual map of these dynamics is therefore a prerequisite for interventions to reduce deforestation. We used a system‐dynamics approach and causal‐network analysis to determine the proximate causes and underlying drivers of forest loss and degradation in Myanmar from 1995 to 2016 and to articulate the linkages among them. Proximate causes included infrastructure development, timber extraction, and agricultural expansion. These were stimulated primarily by formal agricultural, logging, mining, and hydropower concessions and economic investment and social issues relating to civil war and land tenure. Reform of land laws, the link between natural resource extraction and civil war, and the allocation of agricultural concessions will influence the extent of future forest loss and degradation in Myanmar. The causal‐network analysis identified priority areas for policy interventions, for example, creating a public registry of land‐concession holders to deter corruption in concession allocation. We recommend application of this analytical approach to other countries, particularly those undergoing political transition, to inform policy interventions to reduce forest loss and degradation. 相似文献
124.
Ilsa B. Kuffner Rikki Grober-Dunsmore John C. Brock T. Don Hickey 《Environmental monitoring and assessment》2010,164(1-4):513-531
Coral reef ecosystem management benefits from continual quantitative assessment of the resources being managed, plus assessment of factors that affect distribution patterns of organisms in the ecosystem. In this study, we investigate the relationships among physical, benthic, and fish variables in an effort to help explain the distribution patterns of organisms on patch reefs within Biscayne National Park, FL, USA. We visited a total of 196 randomly selected sampling stations on 12 shallow (<10 m) patch reefs and measured physical variables (e.g., substratum rugosity, substratum type) and benthic and fish community variables. We also incorporated data on substratum rugosity collected remotely via airborne laser surveying (Experimental Advanced Airborne Research Lidar—EAARL). Across all stations, only weak relationships were found between physical, benthic cover, and fish assemblage variables. Much of the variance was attributable to a “reef effect,” meaning that community structure and organism abundances were more variable at stations among reefs than within reefs. However, when the reef effect was accounted for and removed statistically, patterns were detected. Within reefs, juvenile scarids were most abundant at stations with high coverage of the fleshy macroalgae Dictyota spp., and the calcified alga Halimeda tuna was most abundant at stations with low EAARL rugosity. Explanations for the overwhelming importance of “reef” in explaining variance in our dataset could include the stochastic arrangement of organisms on patch reefs related to variable larval recruitment in space and time and/or strong historical effects due to patchy disturbances (e.g., hurricanes, fishing), as well as legacy effects of prior residents (“priority” effects). 相似文献
125.
Bacterial abundance, production, and extracellular enzyme activity were determined in the shallow water column, in the epiphytic
community of Thalassia
testudinum, and at the sediment surface along with total carbon, nitrogen, and phosphorus in Florida Bay, a subtropical seagrass estuary.
Data were statistically reduced by principle components analysis (PCA) and multidimensional scaling and related to T. testudinum leaf total phosphorus content and phytoplankton biomass. Each zone (i.e., pelagic, epiphytic, and surface sediment community)
was significantly dissimilar to each other (Global R = 0.65). Pelagic aminopeptidase and sum of carbon hydrolytic enzyme (esterase, peptidase, and α- and β-glucosidase) activities
ranged from 8 to 284 mg N m−2 day−1 and 113–1,671 mg C m−2 day−1, respectively, and were 1–3 orders of magnitude higher than epiphytic and sediment surface activities. Due to the phosphorus-limited
nature of Florida Bay, alkaline phosphatase activity was similar between pelagic (51–710 mg P m−2 day−1) and sediment (77–224 mg P m−2 day−1) zones but lower in the epiphytes (1.1–5.2 mg P m−2 day−1). Total (and/or organic) C (111–311 g C m−2), N (9.4–27.2 g N m−2), and P (212–1,623 mg P m−2) content were the highest in the sediment surface and typically the lowest in the seagrass epiphytes, ranging from 0.6 to
8.7 g C m−2, 0.02–0.99 g N m−2, and 0.5–43.5 mg P m−2. Unlike nutrient content and enzyme activities, bacterial production was highest in the epiphytes (8.0–235.1 mg C m−2 day−1) and sediment surface (11.5–233.2 mg C m−2 day−1) and low in the water column (1.6–85.6 mg C m−2 day−1). At an assumed 50% bacterial growth efficiency, for example, extracellular enzyme hydrolysis could supply 1.8 and 69% of
epiphytic and sediment bacteria carbon demand, respectively, while pelagic bacteria could fulfill their carbon demand completely
by enzyme-hydrolyzable organic matter. Similarly, previously measured T. testudinum extracellular photosynthetic carbon exudation rates could not satisfy epiphytic and sediment surface bacterial carbon demand,
suggesting that epiphytic algae and microphytobenthos might provide usable substrates to support high benthic bacterial production
rates. PCA revealed that T. testudinum nutrient content was related positively to epiphytic nutrient content and carbon hydrolase activity in the sediment, but
unrelated to pelagic variables. Phytoplankton biomass correlated positively with all pelagic components and sediment aminopeptidase
activity but negatively with epiphytic alkaline phosphatase activity. In conclusion, seagrass production and nutrient content
was unrelated to pelagic bacteria activity, but did influence extracellular enzyme hydrolysis at the sediment surface and
in the epiphytes. This study suggests that seagrass-derived organic matter is of secondary importance in Florida Bay and that
bacteria rely primarily on algal/cyanobacteria production. Pelagic bacteria seem coupled to phytoplankton, while the benthic
community appears supported by epiphytic and/or microphytobenthos production. 相似文献
126.
Intertidal macroalgae may spend a significant part of their lives in air. During photosynthesis in air, they encounter much
lower concentrations of inorganic carbon than in seawater. Because they accumulate inorganic carbon from seawater, we investigated
whether they similarly accumulate it from air. We measured photosynthesis in the intertidal species Fucus vesiculosus L. during 1990 and 1991 with a gas-phase O2 electrode or CO2-exchange apparatus in air and with a liquid-phase O2 electrode in seawater. Maximum rates were rapid and similar in air and seawater regardless of the method. Tissue from seawater
could carry on photosynthesis in CO2-free air, indicating that carbon was stored in the tissue. After 2 h, this store was depleted and photosynthesis ceased.
Supplying CO2 in air replenished the store. Under identical conditions, terrestrial C3 and C4 species showed no evidence of this store, but a CAM (crassulacean acid metabolism) species did. However, in contrast to the
CAM behavior, F. vesiculosus did not store CO2 significantly in the dark. We found a small acid-releasable pool of carbon in the tissue that disappeared as photosynthesis
depleted the carbon store. However, the pool was too small to account for the total carbon stored. While CO2 was being acquired or released from the store in the light, photosynthesis was not inhibited by 21% O2. These results indicate that there are two parallel paths for the supply of CO2 to photosynthesis. The first depends on inorganic carbon in seawater or in air and supports rapid photosynthesis. The second
involves CO2 slowly released from an organic intermediate. The release protects CO2 fixation from the inhibitory effects of 21% O2. Photosynthesis in F. vesiculosus thus appears to be C3-like in its rapid fixation of CO2 from a small inorganic pool into phosphoglycerate. However, it is C4-like in its pre-fixation of carbon in an organic pool in the light, and is CAM-like in its ability to slowly use this pool
as a sole source of CO2. The organic pool may serve to protect photosynthetic CO2 fixation against the inhibitory effects of O2 in air and in the boundary layer in seawater.
Received: 6 March 1998 / Accepted: 16 October 1998 相似文献
127.
William Whipple Donald Duflois Neil Grigg Edwin Herricks Howard Holme Jonathan Jones Conrad Keyes Mike Ports Jerry Rogers Eric Strecker Scott Tucker Ben Urbonas Bud Viessman Don Vonnahme 《Journal of the American Water Resources Association》1999,35(4):713-716
ABSTRACT: The planning and developing of water resources to meet the country's needs for water supply, flood control, hydroelectric power, irrigation, and navigation now needs to take more account of environmental needs and regulations. Water resource development is often beneficial to the environment, but may also be harmful, as in cases involving salmon and various other endangered species. As a national objective, the environment must be preserved and in some cases restored; but how can this be done consistent with other national objectives, relating to life and welfare of human beings? This problem has aroused the concern of many engineers and water scientists. As a result, a national conference on this subject was held in Chicago in June 1998, as an integral part of ASCE's Annual Conference on Water Resources Planning and Management and the Annual Conference on Environmental Engineering. At the conclusion of that conference, a post-conference meeting was held by a group of prominent water resource practitioners. It was concluded at this meeting that action should be taken by our government to establish a new form of interagency approach, involving the states, as a means of coordination in cases of national importance. 相似文献
128.
Rainbow trout were exposed to sublethal waterborne Cd (5 and 10 μg L−1) and dietary Ca (60 mg g−1), individually and in combination, for 30 d to elucidate the interactive effects and evaluate the toxicological significance of mitochondrial responses to these cations in vivo. Indices of fish condition and mortality were measured and livers, centers of metabolic homeostasis, were harvested to assess mitochondrial function and cation accumulation. All indices of condition assessed (body weight, hepatosomatic index and condition factor) were reduced in all the treatment groups. Mortality occurred in the Cd-exposed groups with dietary Ca partly protecting against and enhancing it in the lower and higher Cd exposure, respectively. State 3 mitochondrial respiration was inhibited by 30%, 35% and 40% in livers of fish exposed to Ca, Cd and Cd + Ca, respectively, suggesting reduced ATP turnover and/or impaired substrate oxidation. While the phosphorylation efficiency was unaffected, state 4 and state 4+ (+ oligomycin) respirations were inhibited by all the exposures. Mitochondrial coupling was reduced and transiently restored denoting partially effective compensatory mechanisms to counteract Cd/Ca toxicity. The respiratory dysfunction was associated with accumulation of both Cd and Ca in the mitochondria. Although fish that survived acute effects of Cd and Ca exposure apparently made adjustments to energy generation such that liver mitochondria functioned more efficiently albeit at reduced capacity, reduced fitness was persistent possibly due to increased demands for maintenance and defense against toxicity. Overall, interactions between Cd and Ca on condition indices and mitochondrial responses were competitive or cooperative depending on exposure concentrations and duration. 相似文献
129.
Hideaki Shibata Cristina Branquinho William H. McDowell Myron J. Mitchell Don T. Monteith Jianwu Tang Lauri Arvola Cristina Cruz Daniela F. Cusack Lubos Halada Ji?í Kopá?ek Cristina Máguas Samson Sajidu Hendrik Schubert Naoko Tokuchi Jaroslav Záhora 《Ambio》2015,44(3):178-193
Anthropogenically derived nitrogen (N) has a central role in global environmental changes, including climate change, biodiversity loss, air pollution, greenhouse gas emission, water pollution, as well as food production and human health. Current understanding of the biogeochemical processes that govern the N cycle in coupled human–ecological systems around the globe is drawn largely from the long-term ecological monitoring and experimental studies. Here, we review spatial and temporal patterns and trends in reactive N emissions, and the interactions between N and other important elements that dictate their delivery from terrestrial to aquatic ecosystems, and the impacts of N on biodiversity and human society. Integrated international and long-term collaborative studies covering research gaps will reduce uncertainties and promote further understanding of the nitrogen cycle in various ecosystems. 相似文献
130.
Spatially variable refuse gas permeability and landfill gas (LFG) generation rate, cracking of the soil cover, and reduced refuse gas permeability because of liquid addition can all affect CH4 collection efficiency when intermediate landfill covers are installed. A new gas collection system that includes a near-surface high permeability layer beneath the landfill cover was evaluated for enhancing capture of LFG and mitigating CH4 emissions. Simulations of gas transport in two-dimensional domains demonstrated that the permeable layer reduces CH4 emissions up to a factor of 2 for particular spatially variable gas permeability fields. When individual macrocracks formed in the cover soil and the permeable layer was absent, CH4 emissions increased to as much as 24% of the total CH4 generated, double the emissions when the permeable layer was installed. CH4 oxidation in the cover soil was also much more uniform when the permeable layer was present: local percentages of CH4 oxidized varied between 94% and 100% across the soil cover with the permeable layer, but ranged from 10% to 100% without this layer for some test cases. However, the permeable layer had a minor effect on CH4 emissions and CH4 oxidation in the cover soil when the ratio of the gas permeability of the cover soil to the mean refuse gas permeability ?0.05. The modeling approach employed in this study may be used to assess the utility of other LFG collection systems and management practices. 相似文献