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1.
Nico van Breemen Alan Jenkins Richard F. Wright David J. Beerling Wim J. Arp Frank Berendse Claus Beier Rob Collins Douwe van Dam Lennart Rasmussen Paul S. J. Verburg Mark A. Wills 《Ecosystems》1998,1(4):345-351
To evaluate the effects of climate change on boreal forest ecosystems, both atmospheric CO2 (to 560 ppmv) and air temperature (by 3°–5°C above ambient) were increased at a forested headwater catchment in southern
Norway. The entire catchment (860 m2) is enclosed within a transparent greenhouse, and the upper 20% of the catchment area is partitioned such that it receives
no climate treatment and serves as an untreated control. Both the control and treatment areas inside the greenhouse receive
deacidified rain. Within 3 years, soil nitrogen (N) mineralization has increased and the growing season has been prolonged
relative to the control area. This has helped to sustain an increase in plant growth relative to the control and has also
promoted increased N export in stream water. Photosynthetic capacity and carbon–nitrogen ratio of new leaves of most plant
species did not change. While the ecosystem now loses N, the long-term fate of soil N is a key uncertainty in predicting the
future response of boreal ecosystems to climate change.
Received 18 November 1997; accepted 13 April 1998. 相似文献
2.
The Role of Sharks and Longline Fisheries in a Pelagic Ecosystem of the Central Pacific 总被引:2,自引:0,他引:2
James F. Kitchell Timothy E. Essington Christofer H. Boggs Daniel E. Schindler Carl J. Walters 《Ecosystems》2002,5(2):202-216
The increased exploitation of pelagic sharks by longline fisheries raised questions about changes in the food webs that include
sharks as apex predators. We used a version of Ecopath/Ecosim models to evaluate changes in trophic interactions due to shark
exploitation in the Central North Pacific. Fisheries targeted on blue sharks tend to produce compensatory responses that favor
other shark species and billfishes, but they have only modest effects on the majority of food web components. Modest levels
of intraguild predation (adult sharks that eat juvenile sharks) produce strong, nonlinear responses in shark populations.
In general, analysis of the Central North Pacific model reveals that sharks are not keystone predators, but that increases
in longline fisheries can have profound effects on the food webs that support sharks.
Received 19 April 2001; accepted 2 October 2001. 相似文献