Conclusions

1. Single species appear to determine the NPP processes in the ecosystem in a more than proportional manner. It will be a major task of future research to identify these species and their characteristics and develop modeling approaches.

2. Current identification of biomes is not based on a functional analysis, and while some major biomes function similarly in carbon uptake (e.g., European conifer and deciduous forest), within-biome or-species effects can be extremely large. New ways of organizing ecological variability are needed.

3. The quantification of the mean residence time of vegetation and soil compartments and an understanding of the parameters that control this time-scale is necessary for process-based predictions of carbon storage.

4. Some ecosystem processes are "carbon neutral" on a landscape scale because of disturbance-related variability but show distinct trends (positive and negative) at plot within landscapes. Relatively few types of direct measurements are possible at the landscape scale and so the differences in plot and landscape behavior will be a major problem in predicting the effects of the implementation of the Kyoto protocol with respect to mitigation of the increase in atmospheric C02.

N-inputs [g N m"2 yr"1]

Evapostranspiration [cm yr"1

Evapostranspiration [cm yr"1

FIGURE 11 (a) Sum of annual N gas fluxes (N, + NO + N,0) vs N inputs from a global Century model simulation. N inputs result from wet and dry deposition and biological nitrogen fixation. Yellow points are grassland ecosystems, green points are forests, and black points are "mixed" ecosystems such as savannas, (b) N trace gases vs évapotranspiration, (c) N trace gases vs annual N-mineralization. Lines indicate regressions computed from Matson and Vitousek (1990) based on data from the Amazon Basin (Schimel and Panikov, 1999).

N mineralisation [g N m"2 yr"1]

FIGURE 11 (a) Sum of annual N gas fluxes (N, + NO + N,0) vs N inputs from a global Century model simulation. N inputs result from wet and dry deposition and biological nitrogen fixation. Yellow points are grassland ecosystems, green points are forests, and black points are "mixed" ecosystems such as savannas, (b) N trace gases vs évapotranspiration, (c) N trace gases vs annual N-mineralization. Lines indicate regressions computed from Matson and Vitousek (1990) based on data from the Amazon Basin (Schimel and Panikov, 1999).

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Meteorolo, Hamburg, Cennanv

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