Trophic Dynamics

The carbon (C) and water cycles are intimately linked in terrestrial ecosystems. Thus, an understanding of the processes regulating transfers of water in terrestrial ecosystems requires an understanding of the carbon cycle, and in particular, the factors constraining carbon movement in the soil-plant-atmosphere continuum and through trophic levels in ecosystems. The linkages between the C and the water cycles are mediated primarily through biological processes, and are bidirectional in nature. For example, precipitation (and hence ecosystem water availability) strongly regulates plant growth and biogeochemical cycling in soils. Subsequently, plant growth and soil biogeochemistry strongly influence evaporation and atmospheric water vapor (and hence precipitation). Plant growth and soil processes are also cyclically linked. Thus, plant and soil interactions can have important implications for water cycling. However, while major climatic variables (including precipitation) may drive biological patterns and processes at large scales, other ecological interactions also regulate both plant and soil processes. An appreciation of these ecological factors is important to understanding the relationship between C and water, and to predicting how global environmental change is likely to affect the interactions between the C and water cycles.