Stoichiometric Aspects of Nutrient Recycling in Terrestrial Ecosystems

Stoichiometric aspects of nutrient recycling in terrestrial ecosystems Despite new inputs of nutrients due to atmospheric deposition and chemical weathering, the major part of biogeochemical nutrient fluxes in terrestrial ecosystems is originating from the decomposition of dead material in the litterf all and soil (see Chapter 3). 

The composition of organic inputs is as important as size in determining rates of microbial activity and differences in biogeochemical cycling. A complex microcrystalline cellulose base with various intercalated and distinct hemicelluloses, pectins and lignins, all of wbicb contain very little organic nitrogen, forms tbe bulk of terrestrial plant matter. Tbe typical ratio of C N in plant residues is more than 100 (see Table 3). 

In particular, C N ratios 10-15 stimulate mineralization of organic matter with release of mineral nitrogen, whereas C N ratios 30 decrease mineralization and increase assimilation instead with the balance between these processes of uptake and release dependent on the nitrogen content in microbial biomass. Non-symbiotic N fixation can interfere with these processes and ameliorate nitrogen deficiency. 

However, in experimental trials with decomposition of fresh litter in special lit-terbags, these C N and C P ratios decline as decomposition of organic matter proceeds. These may be connected to an increase in the relative part of microbial biomass in litterbags in comparison with the remaining plant materials and remineralization of this biomass (Table 5). 

We can note that C N and C P ratios decrease. This may be related to the retention of nitrogen and phosphorns in microbial biomass, while carbon is lost as CO . The increase of C Ca and C K ratios indicate that Ca and K are lost more rapidly than carbon (Schlesinger, 1991). 

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Discuss the stoichiometric aspects of nutrient recycling in terrestrial ecosystems using carbon and nitrogen cycles as the example. 

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