International Delegations and the Values of Federalism

Inland water sediments receive large quantities of terrestrial organic matter(1-5) and are globally important sites for organic carbon preservation(5,6). Sediment organic matter mineralization is positively related to temperature across a wide range of high-latitude ecosystems(6-10), but the situation in the tropics remains unclear. Here we assessed temperature effects on the biological production of CO2 and CH4 in anaerobic sediments of tropical lakes in the Amazon and boreal lakes in Sweden. On the basis of conservative regional warming projections until 2100 (ref. 11), we estimate that sediment CO2 and CH4 production will increase 9-61% above present rates. Combining the CO2 and CH4 as CO2 equivalents (CO(2)eq; ref. 11), the predicted increase is 2.4-4.5 times higher in tropical than boreal sediments. Although the estimated lake area in low latitudes is 3.2 times smaller than that of the boreal zone, we estimate that the increase in gas production from tropical lake sediments would be on average 2.4 times higher for CO2 and 2.8 times higher for CH4. The exponential temperature response of organic matter mineralization, coupled with higher increases in the proportion of CH4 relative to CO2 on warming, suggests that the production of greenhouse gases in tropical sediments will increase substantially. This represents a potential large-scale positive feedback to climate change

Energy or nutrient regulation of decomposition: Implications for the mineralization-immobilization response to perturbations

A model developed previously to describe the turnover of forest soil nitrogen is modified here to explain the effects of carbon and nitrogen additions on their dynamics. The model, which is structurally very simple, seems to explain correctly, among other phenomena, the negative correlation between N mineralization and CO₂ evolution observed in many experimental situations. An important variable used to explain this behaviour is the deficiency factor, which is related to the critical C-to-nutrient ratio and which gives a measure of the C or nutrient deficiency in the substrate with respect to the needs of the decomposers. Ways are discussed in which the model output can be used to explain the observed retention in the soil of fertilizer N added to mature forest soils