Effects of long-term fertilization of forest soils on potential nitrification and on the abundance and community structure of ammonia oxidizers and nitrite oxidizers

Abstract

Forest fertilization in British Columbia is increasing, to alleviate timber shortfalls resulting from the mountain pine beetle epidemic. However, fertilization effects on soil microbial communities, and consequently ecosystem processes, are poorly understood. Fertilization has contrasting effects on ammonia-oxidizing bacteria and archaea (AOB and AOA) in grassland and agricultural ecosystems, but there are no studies on AOB and AOA in forests. We assessed the effect of periodic (6-yearly application 200 kg N ha⁻¹) and annual (c. 75 kg N ha⁻¹) fertilization of lodgepole pine and spruce stands at five long-term maximum productivity sites on potential nitrification (PN), and the abundance and diversity of AOB, AOA and Nitrobacter and Nitrospira-like nitrite-oxidizing bacteria (NOB). Fertilization increased AOB and Nitrobacter-like NOB abundances at some sites, but did not influence AOA and Nitrospira-like NOB abundances. AOB and Nitrobacter-like NOB abundances were correlated with PN and soil nitrate concentration; no such correlations were observed for AOA and Nitrospira-like NOB. Autotrophic nitrification dominated (55–97%) in these forests and PN rates were enhanced for up to 2 years following periodic fertilization. More changes in community composition between control and fertilized plots were observed for AOB and Nitrobacter-like NOB than AOA. We conclude that fertilization causes rapid shifts in the structure of AOB and Nitrobacter-like NOB communities that dominate nitrification in these forests.

Effects of nitrogen deposition and fertilization on N transformations in forest soils: a review

“…For example, in two acidic forest soils that long suffered from a heavy load of N deposition dominated by dry N deposition and acid deposition, it was found that nitrification in organic and 0-10 cm mineral soils was dominated by heterotrophic nitrification (Jordan et al 2005). However, Wertz et al (2012) reported that autotrophic nitrification still contributed mostly (54.6 to 96.9 %) to nitrification in N-amended organic and mineral soils of lodgepole pine and spruce stands. However, to our knowledge, research on specific pathway-related processes such as autotrophic nitrification and heterotrophic nitrification in N-deposited and N-fertilized forest sites is still very lacking (Tables 1 and 2).…”

“…For instance, in acidic forest soils of southern China, low soil pH led to the low rate of autotrophic nitrification (Zhang et al 2013a). Despite the fact that Wertz et al (2012) found that fertilization increased the abundances of AOB and Nitrobacter-like NOB, rather than ammoniaoxidizing archaea (AOA) and Nitrospira-like NOB abundances, there is increasing evidence that AOA, with a higher affinity for low concentrations of NH 3 in acidic environment, leads to AOB in ammonia oxidation in acidic forest soils (Levy-Booth et al 2014;Zhang et al 2012b). However, rates of autotrophic nitrification in acidic forest soils are generally reported to be low even in the case of N input (Schmidt et al 2007;Zhang et al 2013a).…”

“…Whether net and gross nitrification in forest soils can be stimulated by N deposition and fertilization is associated with N mineralization (Corre et al 2007), the importance of autotrophic nitrification and heterotrophic nitrification (Jordan et al 2005;Perakis et al 2005;Wertz et al 2012), soil N content and pH (Jordan et al 2005), soil C availability (Corre et al 2007), acid tolerance of autotrophic nitrifiers and heterotrophic fungal nitrifiers (Corre et al 2007), and the density of nitrifiers (Bengtsson and Bergwall 2000). In general, increased gross N mineralization, autotrophic nitrification and C availability, acid-tolerant autotrophic nitrifiers, and heterotrophic fungal nitrifiers are conducive to gross nitrification (Corre et al 2007).…”

The activity and kinetic parameters of oxidoreductases in phaeozem in response to long-term fertiliser management

“…Many studies have revealed that long-term fertilisation, whether balanced or unbalanced, influences both the abundance and composition of the soil microbial community (Wu et al, 2011;Wertz et al, 2012). Because the enzymes in the soil originate mainly from these microorganisms, our hypothesis was that balanced or unbalanced long-term fertilisation could alter the specific activity and kinetic parameters of oxidoreductases to differing degrees.…”

Effect of soil acidification on nitrification in soil

“…For each pan, one tube was prepared and treated with 50 mg NH 4 -N kg (1 soil as described above, and incubated for 19 d. At the end of the incubation, a subsample of soil from each tube was then used in the nitrification potential assay to represent soils which has been recently exposed to an addition of NH ' 4 : At that time, subsamples of soil were also collected from each pan, which had been maintained at constant water content and 258C in the growth room, to represent soils that did not have exposure to a recent addition of NH ' 4 : Nitrification potential was assayed under aerobic and non-limiting N substrate conditions, using a soil slurry method (Hart et al 1994;Wertz et al 2011) adjusted to account for pH differences among soil samples. To remove any NO 3 ( initially present in the sample, 3 g of soil was shaken with 30 mL potassium phosphate buffer (1 mM, pH 7.2) for 15 min.…”