Soil carbon pool

The effects that changes in vegetation have on soil carbon pools and nutrient availability are also difficult to evaluate. However, several models have been successful in predicting vegetation-soil nutrient relationships because they assume that such changes occur as a result of different rates of decomposition and nutrient release from leaf litter of different taxa 50, 60), Such predictions could be tested and the models refined or parameterized for new taxa by measuring soil nutrient availability and respiration in stands of different species on the same soil type. For example, fifty years ago the U.S. Civilian Conservation Corps (CCC) established such stands as species trial plots measurements in some indicate large differences in soil nutrient availability (48), Further measurements in these stands would now occur at the same time-scale at which we expect the feedback between species replacement and soil processes to occur. 

Fig. 11-12 Detrital carbon dynamics for the 0-20 cm layer of chernozem grassland soil. Carbon pools (kg C/ m ) and annual transfers (kg C/m per year) are indicated. Total profile content down to 20 cm is 10.4 kg C/m. (Reproduced with permission from W. H. Schlesinger (1977). Carbon balance in terrestrial detritus, Ann. Rev. Ecol. Syst. 8,51-81, Annual Reviews, Inc.)...

Collins HP, Elliott ET, Paustian K, Bundy LG, Dick WA, Huggins DR, Smucker AJM, Paul EA (2000) Soil carbon pools and fluxes in long-term com belt agroecosystems. Soil Biol Biochem 32 157-168... 

Cardon, et al. 2001. Contrasting the effects of elevated C02 on old and new soil carbon pools. Soil Biology and Biochemistry, 33, 365-373. 

Rillig, M. C., Wright, S. F., Nichols, K. A., Schmidt, W. F., and Torn, M. S. (2001). Large contribution of arbuscular mycorrhizal fungi to soil carbon pools in tropical forest soils. Plant Soil 233,166-177. 

Plant productivity is determined by factors such as plant species composition, moisture, soil fertility, growing season length, and solar radiation—many of which are affected by human activities. All else equal, increases in primary productivity and production of plant tissues will lead to increases in soil C stock, while decreases will lead to decreases in soil C stock. The rate of change in soil C stock is determined by the difference between C inputs and outputs, as well as the turnover times of the soil C, which are often not known. Here we review briefly how some environmental factors are expected to alter productivity and explore how the effects on stock depend on the number of soil carbon pools and their turnover times. 

Castanha, C., Trumbore, S., and Amundson, R. (2008). Methods of separating soil carbon pools affect the chemistry and turnover time of isolated fractions. Radiocarbon. 50(1), 83-97. 

Alteration of soil carbon pools and communities of mycorrhizal fungi in chaparral exposed to elevated carbon dioxide. Ecosystems, 6, 786-96. 

Post W. M., Emanuel W. R., Zinke P. J., and Stangenberger A. G. (1982) Soil carbon pools and world life zones. Nature 298, 156-159. 

Townsend A. R., Vitousek P. M., Desmarais D. J., and Tharpe A. (1997) Soil carbon pool structure and temperature sensitivity inferred using CO-2 and 13CO-2 incubation fluxes from five Hawaiian soils. Biogeochemistry (Dordrecht) 38(1), 1-17. 

Hu, S., Coleman, D. C., Carroll, C. R., Hendrix, P. F., Beare, M. H. 1997. Labile soil carbon pools in subtropical forest and agricultural ecosystems as influenced by management practices and vegetation types. Agric. Ecosyst. Environ. 65 69-78. 

Figure 11. Detrital carbon dynamicsfor the 0-20 cm layer ofchemozem grassland soil. Carbon pool (kgC/rrP ) and annual transfers (t is 10.4 kg C/rrr (Schlesinger, 1997).

The nature of P mineralization in soils is a second factor mediating towards phosphorus availability not constraining tropical forest [CO2] responses. This is because, unlike nitrogen, phosphorus is mineralized independent of carbon in most soils. Thus, it has less potential to be locked up in the larger soil carbon pool that should occur as a result of increased plant productivity at higher [CO2]. 

The term d[P j,]/dt is calculated assuming that the concentration of phosphorus in all decomposing litter is 0.16 mmol 1110 . This is based on the 68% retranslocation of P from leaves and fine roots and the average branch, bole, and coarse root P concentrations (Sec. 3.2). Where the sensitivity of the model to P accumulation in the microbial carbon pool is tested, based on data summarized by Gijsman et al. (1996) we use a tissue P concentration for microbes of 6.4 mmol P moG C. In all simulations, it is assumed that soil phosphorus mineralization proceeds with a rate constant of 0.5 year , with phosphorus mineralization proceeding independently of carbon mineralization. This is on the basis of the evidence discussed in Sec. 2.1. Indeed, inflexible soil carbon pool C/P ratios which effectively link phosphorus mineralization rate to the carbon mineralization rate in models such as CENTURY (Parton et al, 1988) have been strongly criticized by some tropical soil chemists (Gijsman et al, 1996). 

Introduction the Soil Carbon Pool and Global Change. 185... 

This chapter examines the status of observational studies of the SOC pool, global trends in the soil carbon pool, and the relationship between observational studies and efforts to model the dynamics of carbon exchange in the SOC pool and suggests how... 

The complex interactions possible between all of the above variables are one of the root causes of the many uncertainties surrounding the dynamics of carbon exchange through and within the soil carbon pool. 

---