Relationship between N-cycling communities and ecosystem functioning in a 50-year-old fertilization experiment

Abstract

The relative importance of size and composition of microbial communities in ecosystem functioning is poorly understood. Here, we investigated how community composition and size of selected functional guilds in the nitrogen cycle correlated with agroecosystem functioning, which was defined as microbial process rates, total crop yield and nitrogen content in the crop. Soil was sampled from a 50-year fertilizer trial and the treatments comprised unfertilized bare fallow, unfertilized with crop, and plots with crop fertilized with calcium nitrate, ammonium sulfate, solid cattle manure or sewage sludge. The size of the functional guilds and the total bacterial community were greatly affected by the fertilization regimes, especially by the sewage sludge and ammonium sulfate treatments. The community size results were combined with previously published data on the composition of the corresponding communities, potential ammonia oxidation, denitrification, basal and substrate-induced respiration rates, in addition to crop yield for an integrated analysis. It was found that differences in size, rather than composition, correlated with differences in process rates for the denitrifier and ammonia-oxidizing archaeal and total bacterial communities, whereas neither differences in size nor composition was correlated with differences in process rates for the ammonia-oxidizing bacterial community. In contrast, the composition of nitrate-reducing, denitrifying and total bacterial communities co-varied with primary production and both were strongly linked to soil properties.

Response of denitrification genes nirS, nirK, and nosZ to irrigation water quality in a Chinese agricultural soil

“…The abundance of nosZ gene was the highest one among the three functional genes in this study. This result was higher than those of previously reported: nosZ density of 3×10 6 -2.8×10 8 copies g −1 dry soil (Kandeler et al 2006;Dandie et al 2008;Hallin et al 2009). But Chronakova et al (2009) found the nosZ gene copy number was in a range of 9.1×10 7 -7.5×10 9 copies g −1 soil in an upland pasture soil.…”

Effect of pyrene on denitrification activity and abundance and composition of denitrifying community in an agricultural soil

“…Previous studies showed that denitrification enzyme activity was correlated with the copy numbers of nirK gene (Throbäck et al, 2007) and nosZ gene (Hallin et al, 2009), suggesting that denitrifiers harboring these functional genes played an important role in the denitrification process, and the abundance of the denitrifying community could predict the corresponding process (Hallin et al, 2009). The mean EC 50 values of pyrene for copy numbers of nirK, nirS and nosZ genes were lower than that of pyrene for PDA, indicating that denitrifiers harboring nirK, nirS or nosZ gene was more sensitive to pyrene than PDA, and denitrifiers harboring nirS gene was more sensitive to pyrene than that harboring nirK or nosZ gene.…”

“…The activity of reductases and the expression of functional genes involved in denitrification process varies among individual strains (Zumft, 1997), and community composition is thus considered to be able to influence functionality at both community and ecosystem levels (Braker et al, 2010). Nevertheless, some studies have reported correlations between abundance and function as well as between structure and function of denitrifying communities (Bremer et al, 2009;Hallin et al, 2009;Rich et al, 2003) while others not Miller et al, 2008;Wertz et al, 2009). Therefore, it is important to determine the correlations among changes in function, abundance and composition of the denitrifying community in an agricultural soil in response to PAHs stress.…”

Abundance and community structure of ammonia oxidizing bacteria and archaea in a Sweden boreal forest soil under 19-year fertilization and 12-year warming

“…Studies in three forest ecosystems indicated that shifts of soil C/N ratio, soil acidification, and root exudation reduction induced by N saturation caused bacterial biomass decreasing under long-term fertilization (Wallenstein et al 2006). Nitrogen fertilization has previously been shown to increase the abundance of soil AOB, which dominated N-rich environments (Di et al 2009;Hallin et al 2009). However, we observed an insignificant effect of fertilization on AOB and AOA abundance (see Fig.…”

“…1b). A 50-year-old fertilization experiment showed that amoA gene copy numbers of AOB and AOA under several fertilized treatments were insignificant, except for the ammonium sulfate treatment (Hallin et al 2009). That difference may be explained by the fact that the application of ammonium sulfate would lower the soil pH value.…”