| 1. |
- Biggs, Reinette, et al.
(författare)
-
Preparing for the future : teaching scenario planning at the graduate level
- 2010
-
Ingår i: Frontiers in Ecology and the Environment. - : Wiley. - 1540-9295. ; 8:5, s. 267-273
-
Tidskriftsartikel (refereegranskat)abstract
- Are environmental science students developing the mindsets and obtaining the tools needed to help address the considerable challenges posed by the 21st century? Today's major environmental issues are characterized by high-stakes decisions and high levels of uncertainty. Although traditional scientific approaches are valuable, contemporary environmental issues also require new tools and new ways of thinking. We provide an example of how such new, or “post-normal”, approaches have been taught at the graduate level, through practical application of scenario planning. Surveyed students reported that they found the scenario planning course highly stimulating, thought-provoking, and inspiring. Key learning points included recognizing the need for multiple points of view when considering complex environmental issues, and better appreciating the pervasiveness of uncertainty. Collaborating with non-academic stakeholders was also particularly helpful. Most students left the course feeling more positive about the potential contribution they can make in addressing the environmental challenges that society faces. Read More: http://www.esajournals.org/doi/abs/10.1890/080075
|
|
| 2. |
- Bade, Darren L., et al.
(författare)
-
Sources and fates of dissolved organic carbon in lakes as determined by whole-lake carbon isotope additions
- 2007
-
Ingår i: Biogeochemistry. - : Springer Science and Business Media LLC. - 1573-515X .- 0168-2563. ; 84:2, s. 115-129
-
Tidskriftsartikel (refereegranskat)abstract
- Four whole- lake inorganic C-13 addition experiments were conducted in lakes of differing trophic status. Inorganic C-13 addition enriched algal carbon in C-13 and changed the delta C-13- DOC by + 1.5 parts per thousand to + 9.5 parts per thousand, depending on the specific lake. This change in delta C-13- DOC represented a significant input of algal DOC that was not completely consumed by bacteria. We modeled the dynamics in delta C-13- DOC to estimate the fluxes of algal and terrestrial carbon to and from the DOC pool, and determine the composition of the standing stock. Two experiments in lightly stained, oligotrophic lakes indicated that algal production was the source of about 20% of the DOC pool. In the following year, the experiment was repeated in one of these lakes under conditions of nutrient enrichment, and in a third, more humic lake. Algal contributions to the DOC pool were 40% in the nutrient enriched lake and 5% in the more humic lake. Spectroscopic and elemental analyses corroborated the presence of increased algal DOC in the nutrient enriched lake. Natural abundance measurements of the delta C-13 of DOC in 32 lakes also revealed the dual contributions of both terrestrial and algal carbon to DOC. From these results, we suggest an approach for inferring the contribution of algal and terrestrial DOC using easily measurable parameters.
|
|
| 3. |
- Carpenter, Stephen R., et al.
(författare)
-
Ecosystem subsidies : Terrestrial support of aquatic food webs from C-13 addition to contrasting lakes
- 2005
-
Ingår i: Ecology. - : John Wiley & Sons. - 0012-9658 .- 1939-9170. ; 86:10, s. 2737-2750
-
Tidskriftsartikel (refereegranskat)abstract
- Whole-lake additions of dissolved inorganic C-13 were used to measure allochthony (the terrestrial contribution of organic carbon to aquatic consumers) in two unproductive lakes (Paul and Peter Lakes in 2001), a nutrient-enriched lake (Peter Lake in 2002), and a dystrophic lake (Tuesday Lake in 2002). Three kinds of dynamic models were used to estimate allochthony: a process-rich, dual-isotope flow model based on mass balances of two carbon isotopes in 12 carbon pools; simple univariate time-series models driven by observed time courses of delta(13)CO(2); and multivariate autoregression models that combined information from time series of delta(13)C in several interacting carbon pools. All three models gave similar estimates of allochthony. In the three experiments without nutrient enrichment, flows of terrestrial carbon to dissolved and particulate organic carbon, zooplankton, Chaoborus, and fishes were substantial. For example, terrestrial sources accounted for more than half the carbon flow to juvenile and adult largemouth bass, pumpkinseed sunfish, golden shiners, brook sticklebacks, and fathead minnows in the unenriched experiments. Allochthony was highest in the dystrophic lake and lowest in the nutrient-enriched lake. Nutrient enrichment of Peter Lake decreased allochthony of zooplankton from 0.34-0.48 to 0-0.12, and of fishes from 0.51-0.80 to 0.25-0.55. These experiments show that lake ecosystem carbon cycles, including carbon flows to consumers, are heavily subsidized by organic carbon from the surrounding landscape.
|
|
| 4. |
- Cole, Jonathan J, et al.
(författare)
-
Multiple approaches to estimating air-water gas exchange in small lakes
- 2010
-
Ingår i: Limnology and Oceanography. - : American Society of Limnology and Oceanography. - 1541-5856. ; 8, s. 285-293
-
Tidskriftsartikel (refereegranskat)abstract
- The rate of gas exchange between air and water is an essential quantity in a number of contexts, from mass balances to the calculation of whole-system metabolism. The exchange of a gas between water and the atmosphere is controlled by differential partial pressures of gases in air and in water (both straightforward to measure) and by the amount of turbulent energy exchange between the air-water interface, the measurement of which is neither simple nor direct. This physical exchange is often expressed as a piston velocity (k). We compared four methods for estimating k in a series of small (0.3 to 45 ha), low-wind (mean wind < 3 m s–1) lakes: 1) floating chambers using ambient CH4; 2) whole-lake SF6 additions; 3) three wind-based models from the literature; and 4) C mass balances constrained by whole-lake 13C additions. All of the methods, with the exception of one windbased model, converged on values for k600 of between 0.35 and 0.74 m d–1 with no biases among methods. The floating chambers, if designed properly, are a cost-effective way of obtaining site-specific values of k for low wind lakes over fairly short time frames (hours).
|
|
| 5. |
- Pace, Michael L., et al.
(författare)
-
Whole-lake carbon-13 additions reveal terrestrial support of aquatic food webs
- 2004
-
Ingår i: Nature. - : Nature Publishing Group. - 0028-0836 .- 1476-4687. ; 427:6971, s. 240-243
-
Tidskriftsartikel (refereegranskat)abstract
- Ecosystems are supported by organic carbon from two distinct sources. Endogenous carbon is produced by photosynthesis within an ecosystem by autotrophic organisms. Exogenous carbon is produced elsewhere and transported into ecosystems. Consumers may use exogenous carbon with consequent influences on population dynamics, predator-prey relationships and ecosystem processes(1). For example, exogenous inputs provide resources that may enhance consumer abundance beyond levels supported by within-system primary production(2). Exogenous fluxes of organic carbon to ecosystems are often large, but this material is recalcitrant and difficult to assimilate, in contrast to endogenously produced organic matter, which is used more easily(3,4). Here we show, by the experimental manipulation of dissolved inorganic C-13 in two lakes, that internal primary production is insufficient to support the food webs of these ecosystems. Additions of NaH (CO3)-C-13 enriched the C-13 content of dissolved inorganic carbon, particulate organic carbon, zooplankton and fish. Dynamics of C-13 indicate that 40-55% of particulate organic carbon and 22-50% of zooplankton carbon are derived from terrestrial sources, showing that there is significant subsidy of these ecosystems by organic carbon produced outside their boundaries.
|
|
