Soil Processes and Properties

Soil Processes and Properties

Temperature changes will have only minimal effects on reaction rates for inorganic processes in soils, but changes in soil moisture could have significant effects on rates of diffusion and supply of nutrients to plants.

Carbon Dynamics

The global pool of carbon is available for cycling by natural processes on interannual to centery timescales (i.e., all except fossil carbon) in reservoirs as follows:

Both NPP and organic-matter decomposition likely will increase under increasing temperature. If moisture is readily available, decomposition of organic matter is likely to be enhanced more than NPP under global warming, thereby adding more CO2 to the atmosphere. However, if moisture becomes more limiting then decomposition will be reduced. Models that take both temperature and moisture into account suggest that increased NPP would lead to increases in soil carbon under increasing atmospheric CO2.

Land use is a much more important factor than changes in NPP for determining soil carbon. Typically about half of the native carbon is lost from soils when they are put under cultivation over a period of 50-100 years. Minimum tillage practices reduce carbon loss from soils.

Soil Biodiversity

Climate change, specifically changes in temperature and water availability, could change soil microbial and faunal populations, but changes in land-use practices are likely to have much greater impact. However, another element of global change, namely increased deposition of nitrogen from industrial NOX emissions, is being more widely associated with major losses of fungi in the root zone in some (particularly forest) biomes.

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