Interrelationships among soil nitrogen transformation rates, functional gene abundance and soil properties in a tropical forest with exogenous N inputs

Abstract. Elevated nitrogen (N) deposition affects soil N transformations in the N-rich soil of tropical forests. However, the change in soil functional microorganisms responsible for soil N cycling remains largely unknown. Here, we investigated the variation in soil inorganic N content, net N mineralization (Rm), net nitrification (Rn), inorganic N leaching (Rl), N2O efflux and N-related functional gene abundance in tropical forest soil over a two-year period with four levels of N addition. The responses of soil N transformations (in situ Rm, Rn and Rl) to N additions were delayed during the first year of N inputs. The Rm, Rn, and Rl increased with the medium nitrogen (MN) and high nitrogen (HN) treatments relative to the control treatments in the second year of N additions. Furthermore, the Rm, Rn, and Rl were higher in the wet season than in the dry season. The Rm and Rn were predominately driven by the lower C : N ratio under N addition in the dry season but by higher microbial biomass in the wet season. Throughout the study period, high N additions increased the annual N2O emissions by 78 %. Overall, N additions significantly facilitated soil N availability (Rm and Rn) and N loss (Rl and N2O emission), which had a stimulating effect on N transformations. In addition, the MN and HN treatments increased the ammonia-oxidizing archaea (AOA) abundance by 17.3 % and 7.5 %, respectively. Meanwhile, the HN addition significantly increased the abundance of nirK-denitrifiers but significantly decreased the abundance of ammonia-oxidizing bacteria (AOB) and nosZ-containing N2O reducers. To some extent, the variation in functional gene abundance was related to the corresponding N transformation processes. Partial least squares path modelling (PLS-PM) indicated that inorganic N contents had significant negative direct effects on the abundances of N-related functional genes in the wet season, implying that chronic N deposition would have a negative effect on the N-cycling-related microbes and the function of N transformation.

Download Full-text

The simulated N deposition accelerates net N mineralization and nitrification in a tropical forest soil

Biogeosciences ◽

10.5194/bg-16-4277-2019 ◽

2019 ◽

Vol 16 (21) ◽

pp. 4277-4291

Author(s):

Yanxia Nie ◽

Xiaoge Han ◽

Jie Chen ◽

Mengcen Wang ◽

Weijun Shen

Keyword(s):

N Deposition ◽

Functional Genes ◽

Net N Mineralization ◽

Soil N ◽

Wet Season ◽

Inorganic N ◽

N Transformations ◽

N Transformation ◽

Soil N Transformation ◽

N Additions

Abstract. Elevated nitrogen (N) deposition affects soil N transformations in the N-rich soil of tropical forests. However, the change in soil functional microorganisms responsible for soil N cycling remains largely unknown. Here, we investigated the variation in soil inorganic N content, net N mineralization (Rm), net nitrification (Rn), inorganic N leaching (Rl), N2O efflux and N-related functional gene abundance in a tropical forest soil over a 2-year period with four levels of N addition. The responses of soil net N transformations (in situ Rm and Rn) and Rl to N additions were negligible during the first year of N inputs. The Rm, Rn, and Rl increased with the medium nitrogen (MN) and high nitrogen (HN) treatments relative to the control treatments in the second year of N additions. Furthermore, the Rm, Rn, and Rl were higher in the wet season than in the dry season. The Rm and Rn were mainly associated with the N addition-induced lower C:N ratio in the dry season but with higher microbial biomass in the wet season. Throughout the study period, high N additions increased the annual N2O emissions by 78 %. Overall, N additions significantly facilitated Rm, Rn, Rl and N2O emission. In addition, the MN and HN treatments increased the ammonia-oxidizing archaea (AOA) abundance by 17.3 % and 7.5 %, respectively. Meanwhile, the HN addition significantly increased the abundance of nirK denitrifiers but significantly decreased the abundance of ammonia-oxidizing bacteria (AOB) and nosZ-containing N2O reducers. To some extent, the variation in functional gene abundance was related to the corresponding N-transformation processes. Partial least squares path modelling (PLS-PM) indicated that inorganic N contents had significantly negative direct effects on the abundances of N-related functional genes in the wet season, implying that chronic N deposition would have a negative effect on the N-cycling-related microbes and the function of N transformation. Our results provide evidence that elevated N deposition may impose consistent stimulatory effects on soil N-transformation rates but differentiated impacts on related microbial functional genes. Long-term experimentation or observations are needed to decipher the interrelations between the rate of soil N-transformation processes and the abundance or expression of related functional genes.

Download Full-text

1007 - Fire-deposited charcoal enhanced soil N retention without affecting N-cycling functional gene abundance in a Chinese Pinus massoniana plantation

10.26226/morressier.5b5199c1b1b87b000ecee783 ◽

2018 ◽

Author(s):

Xian Liu

Keyword(s):

Pinus Massoniana ◽

N Cycling ◽

Functional Gene ◽

Soil N ◽

N Retention ◽

Gene Abundance ◽

Functional Gene Abundance

Download Full-text

Tree species influence on microbial functional gene abundance and N cycling in riparian soil

10.33915/etd.8276 ◽

2021 ◽

Author(s):

Elizabeth Matejczyk

Keyword(s):

Tree Species ◽

N Cycling ◽

Functional Gene ◽

Gene Abundance ◽

Functional Gene Abundance ◽

Microbial Functional Gene

Download Full-text

Abiotic versus biotic controls on soil nitrogen cycling in drylands along a 3200 km transect

10.5194/bg-2016-226 ◽

2016 ◽

Author(s):

Dongwei Liu ◽

Weixing Zhu ◽

Xiaobo Wang ◽

Yuepeng Pan ◽

Chao Wang ◽

...

Keyword(s):

Arid Zone ◽

N Cycling ◽

Mean Annual Precipitation ◽

N Availability ◽

Soil N ◽

Inorganic N ◽

N Transformations ◽

Soil Inorganic N ◽

Soil Inorganic ◽

Biotic Controls

Abstract. Nitrogen (N) cycling of drylands under changing climate is not well understood. Our understanding about N cycling over larger scales to date relies heavily on the measurement of bulk soil N, and the information about soil internal N transformations remains limited. The 15N natural abundance (δ15N) of ammonium and nitrate can serve as a proxy record for the N processes in soils. To better understand the patterns and mechanisms of water availability on soil N cycling in drylands, we collected soils along a 3200 km dryland transect at about 100 km intervals in northern China, with mean annual precipitation (MAP) from 36 mm to 436 mm. We analysed N pools and δ15N of ammonium, dual isotopes (15N and 18O) of nitrate, and the microbial gene abundance associated with soil N transformations. We found that the N status and their driven factors were different on the two sides of MAP = 100 mm. In the arid zone with MAP below 100 mm, soil inorganic N accumulated, with a large fraction being of atmospheric origin. Ammonia volatilization was strong because of the higher soil pH. The abundance of microbial genes associated with soil N transformations was also significantly low. In the semiarid zone with MAP above 100 mm, soil inorganic N concentrations were low and controlled mainly by biological processes, e.g., plant uptake and denitrification. The preference of soil ammonium to nitrate by the dominant plant species may enhance the possibility of soil nitrate loss via denitrification. Overall, our study suggest that the shifting from abiotic to biotic controls on soil N biogeochemistry under global climate changes would greatly affect N losses, soil N availability, and other N transformation processes in these drylands in China.

Download Full-text

Abiotic versus biotic controls on soil nitrogen cycling in drylands along a 3200 km transect

Biogeosciences ◽

10.5194/bg-14-989-2017 ◽

2017 ◽

Vol 14 (4) ◽

pp. 989-1001 ◽

Cited By ~ 16

Author(s):

Dongwei Liu ◽

Weixing Zhu ◽

Xiaobo Wang ◽

Yuepeng Pan ◽

Chao Wang ◽

...

Keyword(s):

Arid Zone ◽

N Cycling ◽

Mean Annual Precipitation ◽

N Availability ◽

Soil N ◽

Inorganic N ◽

N Transformations ◽

Soil Inorganic N ◽

Soil Inorganic ◽

Biotic Controls

Abstract. Nitrogen (N) cycling in drylands under changing climate is not well understood. Our understanding of N cycling over larger scales to date relies heavily on the measurement of bulk soil N, and the information about internal soil N transformations remains limited. The 15N natural abundance (δ15N) of ammonium and nitrate can serve as a proxy record for the N processes in soils. To better understand the patterns and mechanisms of N cycling in drylands, we collected soils along a 3200 km transect at about 100 km intervals in northern China, with mean annual precipitation (MAP) ranging from 36 to 436 mm. We analyzed N pools and δ15N of ammonium, dual isotopes (15N and 18O) of nitrate, and the microbial gene abundance associated with soil N transformations. We found that N status and its driving factors were different above and below a MAP threshold of 100 mm. In the arid zone with MAP below 100 mm, soil inorganic N accumulated, with a large fraction being of atmospheric origin, and ammonia volatilization was strong in soils with high pH. In addition, the abundance of microbial genes associated with soil N transformations was low. In the semiarid zone with MAP above 100 mm, soil inorganic N concentrations were low and were controlled mainly by biological processes (e.g., plant uptake and denitrification). The preference for soil ammonium over nitrate by the dominant plant species may enhance the possibility of soil nitrate losses via denitrification. Overall, our study suggests that a shift from abiotic to biotic controls on soil N biogeochemistry under global climate changes would greatly affect N losses, soil N availability, and other N transformation processes in these drylands in China.

Download Full-text