Abstract
Soil moisture is the major factor influencing microbial properties and nitrous oxide (N2O) production. Agricultural soils can be probed under wetting, wet/dry alternating, and constant moisture conditions to evaluate the combined effects of early (previous) and immediate (current) moisture on N2O emission and nitrification/denitrification. In view of the water history of upland black soil, five moisture regimes comprising different antecedent and present water holding capacity (WHC) levels were set up in the microcosm study. The 20% WHC was adopted as the initial legacy moisture, while three immediate water statuses include constant WHC, dry-wet cycle, and incremental moisture. Quantitative PCR and 16S rRNA amplicon sequencing were used to assess the impact of current and previous moisture on the bacterial community composition and abundance of nitrification/denitrification genes (amoA, nirS, and nosZ); the soil physicochemical properties, and N2O emission were monitored. The N2O production and nitrifying-denitrifying microbial communities were influenced by the antecedent moisture and pattern of the dry-wet cycle. The nitrifying-denitrifying microbial communities, especially members of β-/γ-Proteobacteria, Bacteroidetes and Gemmatimonadetes, in black soil were important in explaining the variation of N2O production. The key taxonomic groups in response to the moisture alteration, e.g., Acidobacteria, Sphingobacteriia, Deltaproteobacteria, Methylobacterium, Gemmatimonas and Pseudarthrobacter, etc., were also highlighted. The soil nitrate, ammonium nitrogen, N2O emission, nitrification/denitrification and mineralization were profoundly impacted by water regimes and showed statistically significant correlation with specific bacterial genera; the nitrite/nitrate reduction to ammonium could be boosted by high moisture. Both nitrifier denitrification and heterotrophic denitrification could be enhanced substantially when the black soil moisture was increased to above 60% WHC. These findings help evaluate the effects of the water mode on the N2O emission from black soil, as well as the associated impacts on both soil fertility and the global environment.
Highlights
Introduction distributed under the terms andBlack soil is rich in organic matter and of high fertility [1]
The antecedent moisture is relative to the subsequent moisIn each moisture regime, the antecedent moisture is relative to the subsequent moisture, ture, the time duration of early moisture varied in different regimes
We try to answer: Is there a legacy effect of soil moisture on bacterial community structure and N2O emission in the upland black soil of northeast China? How do the structure and quantitative activity of nitrification and denitrification microbe communities change in black soil with regard to the antecedent moisture? What is the water can provide a lot of relevant information about the legacy effect of early moisture
Summary
Black soil is rich in organic matter and of high fertility [1]. In light of the water and heat conditions of soil, the soil aeration and heat absorption, the microbial functions that accelerate the decomposition of organic matter, and the soil effective fertility, black soil is very suitable for plant growth. Black soil is very degraded [2], and the utilization rate of nitrogen fertilizer is reduced, accompanied by nitrogen loss and environmental problems, e.g., the emission of greenhouse gas nitrous oxide (N2 O). Soil physicochemical and biological properties, such as moisture, aeration, pH, inorganic nitrogen, organic carbon, and microbial community/populations largely determine the production and emission of N2 O [3,4]; among them, soil moisture status has a strong impact on N2 O production [5]. While there have been studies investigating the effects of water regime on N2 O in soils, a majority of them focused on the effects of water content [4,6] or the wet-dry cycle [7] and the relationship between N2 O production/discharge and soil moisture history (preceding water) was comparatively less-studied
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