Effects of conversion of natural forest to plantations on the abundance of nitrite reducing genes in soil aggregates in subtropical forest region.

Large proportion of natural forest has been transformed into plantations in subtropical regions, with consequences on forest ecosystem structure and function. In order to understand the responses of two nitrite reducing genes ( and ) in NO production to forest conversion, we collected soil samples from natural forest, plantation and plantation and examined the abundance of and genes in soils and aggregates. Results showed that forest conversion increased soil pH, while decreased soil ammonium content. Forest conversion did not influence the mass proportion of soil aggregates. The abundance of and genes varied in aggregates with different particle sizes. The abundance of and genes was the highest in small macraoaggregates and the lowest in the silt-clay particles. Moreover, the abundance of was significantly higher than that of in soils of all forest types, indicating that dominated in the acidic forest soils. Conversion of natural forest to plantations significantly increased the abundance of and genes in the bulk soil and aggregates, indicating that forest conversion would be beneficial for the growth of microorganisms bearing and genes, which might be associated with the increases of soil pH. Taken together, conversion of natural forest to plantation or plantation significantly increased the abundance of and in soils and aggregates, but did not affect the mass proportions of aggregates.