42
2 Basic Ecology
Fig. 2.7 The nitrogen cycle, Source: Encyclopædia Britannica (2011a)
bacterial species, including Clostridium and Pseudomonas. The process takes place
in anaerobic conditions, including waterlogged soils.
Many human activities significantly influence the nitrogen cycle. The combustion of fossil fuels, nitrogen-based fertilizer applications, and other activities can
drastically increase the quantity of available nitrogen. Since nitrogen availability
impedes the primary productivity of numerous ecosystems, substantial changes
in nitrogen availability can result in severe changes in the nitrogen cycle within
terrestrial and aquatic ecosystems (Gruber and Galloway 2008). Anthropogenic
activities, including the combustion of fossil fuels and the deployment of artificial
nitrogen fertilizers, have significantly influenced the global nitrogen cycle. Adding
nitrogen to the terrestrial ecosystems could lead to a nutrient imbalance in trees and
the decline of biodiversity.