[Soil biochemical characteristics in different ecological systems and their relationships with soil respiration and N2O emission].

The biochemical characteristics of soil in different ecological system and their effects on soil respiration (CO2) and nitrous oxide (N2O) emission were investigated by an indoor incubation method. The results showed that the biochemical characteristics of soils in the different ecosystems and CO2 and N2O emissions from different soils greatly varied with each other. In general, the highest abundance of bacteria was found in the orchard soil, the highest abundance of actinomycetes occurred in the meadows and the highest abundance of fungi appeared in the woodlands. The abundance of bacteria or actinomycetes in the bamboo soil was the lowest among all soils, and the orchard soil had the lowest content of fungi. The contents of soil microbial biomass carbon and nitrogen generally followed the order of orchard soil > woodland > cropland. Moreover, cumulative CO2 and N2O emissions from the different soils followed the order of orchard soil > bamboo soil > farmland > woodland > grassland and farmland > orchard > grassland > woodland > bamboo soil, respectively. Correlation analysis indicated that there was positive correlations between the abundance of soil bacteria and the contents of microbial biomass carbon and nitrogen, as well as between the abundance of soil fungi and the soil total nitrogen content (P < 0.05), while the abundance of soil actinomycosis was positively correlated with soil organic carbon and total nitrogen contents (P < 0.01). The soil bacteria, microbial carbon and nitrogen had a significant positive impact on soil respiration (P < 0.05), and soil bacteria, actinomycetes, fungi and ammonium nitrogen had the same impact on N2O emissions (P < 0.05). Stepwise regression analysis suggested that soil respiration could be quantitatively determined by a linear combination of soil bacteria and soil pH, while N2O emission was mainly dependent on the values of soil bacteria and ammonium nitrogen.