Ragnhildur Sigurdardottir

STRUCTURAL AND FUNCTIONAL RESPONSES OF A SUBTROPICAL FOREST TO 10 YEARS OF HURRICANES AND DROUGHTS

Little is known about ecosystem-level responses to multiple, climatic disturbance events. In the subtropical forests of Puerto Rico, the major natural disturbances are hurricanes and droughts. We tested the ecosystem-level effects of these disturbances in sites with different land use histories. From 1989 to 1992, data were collected to determine the effects of Hurricane Hugo and two droughts on litterfall inputs, fine-root biomass, and decomposition rates in three topographic locations (stream, riparian, upslope) within two watersheds. From 1994 to 1998, we added a third watershed and an experiment in which coarse-wood levels were manipulated to simulate hurricane inputs. Data were collected on tree and palm growth rates, litterfall inputs, fine-root biomass, and decomposition rates. From 1994 to 1998, four hurricanes and three droughts were recorded. Measured parameters had unique responses and recovery rates to hurricanes and droughts. Litterfall inputs returned to long-term mean rates within one month...

List of Boxes

1.1 Leakage effects can be very substantial 12 1.2 The unpredictability of the effects of support removal 16 2.1 Subsidy addiction in Germany 31 2.2 Four ways to better target water subsidies 40 7.1 Selected rates of German mineral oil tax, 1998 125 11.1 Comparing the costs of reducing diesel consumption 199 13.1 Extracts from Council Regulation (EEC) 2078/92 on Agricultural Production Methods Compatible with the Requirements of the Protection of the Environment and the Maintenance of the Countryside 229 14.1 The use of taxes to support environmental objectives 252 14.2 The environmental impact of ‘novel crops’ – oilseed rape 255 14.3 Article 2 of the Agri-environment Regulation 258 14.4 Environmental benefits of maintaining anthropogenic ecosystems 262 14.5 The work of the Food and Veterinary Office, European Commission 265 14.6 Agri-environmental policy in the Netherlands – trading in manure 270