Effect of Precipitation and Nitrogen Input on Soil Respiration in Grasslands

Abstract

Nowadays soil respiration has become an important issue in research. Measurement of soil respiration helps in determining the carbon budget under the influence of global climate change. Rainfall variability and nitrogen (N) input both have a profound impact on soil respiration and its components, i.e. autotrophic and heterotrophic respiration. Besides, soil respiration also shows considerable change due to global warming. According to emissions scenario, the elevated CO2 concentration would increase the soil surface temperature by 2oC in the coming 35 years which may lead to huge C-losses to the atmosphere. Such carbon losses to the atmosphere would aggravate the effects of global warming on the human race. Although some progress had been made in soil respiration research about rainfall variability and N-input, there are discrepancies in the results. But despite considerable scientific attention in recent years, there is no consensus on the direction and magnitude of warming-induced changes in soil carbon. Soil respiration changes with climate but to confirm it observationally have big constraints such as high spatial variability in soil respiration, inaccessibility of the soil medium and inability of the instruments to measure soil respiration on large scales. Further, most of the soil respiration studies about rainfall variability and N-input have been conducted in temperate regions, and tropics have remained ignored. Though tropical countries have not yet experienced the extreme variations in rainfall, still under the ongoing climate change the tropical region would also start to experience altered rainfall regimes. Rainfall variability and N-input are the consequences of intense global climate change and industrialisation, respectively. There are reports from grasslands that the antecedent soil moisture determines the strength of the effect of rainfall on soil respiration. N-input is reported to increase soil respiration only when water addition accompanied it. Further, the effect of N-input on soil respiration was different for the short term and long term addition of nitrogen. Likewise many ecosystem warming experiments suggest that warming increases the carbon fluxes to and from the soil, but the net global balance between these responses is uncertain.