Effects of plowing and plant residue mulching on soil nitrous oxide emissions in a black soil beach-type degraded grassland

doi:10.11686/cyxb2023485

Abstract

Abstract:

Grassland restoration is the key measure to promote the restoration of the grassland ecosystem and achieve sustainable development. The aim of this work was to explore the effects of plowing and mulching with plant residues on soil nitrous oxide （N₂O） emissions from an extremely degraded alpine grassland. The experiment was conducted in an alpine meadow in Hongyuan County， Sichuan， China， on the Eastern edge of the Qinghai-Tibetan Plateau. The experiment consisted of a control （CK） and three treatments； i.e.， black soil beach-type degraded grassland with roots removed from the 0-20 cm soil layer and no plant residues （CK）， plowed degraded grassland （PL）， degraded grassland mulched with plant residues （MR）， and plowed degraded grassland mulched with plant residues （PL+MR）. We measured soil basic physical and chemical indicators， microbial biomass， extracellular enzyme activity， nitrification enzyme activity， denitrification enzyme activity， functional microbial gene abundance， and 28-day cumulative N₂O emissions. The results showed that， compared with CK， PL significantly increased cumulative soil N₂O emissions （by 44.2%）. Soil N₂O emissions were significantly lower in PL+MR （by 29.1%） than in PL. Compared with CK， PL significantly enhanced soil pH （by 2.6%）， increased dissolved organic carbon （DOC） and microbial biomass carbon （MBC） concentrations （by 209.5% and 23.8%， respectively）， increased activities of β-1，4-glucosidase （BG） and β-1，4-N-acetylglucosaminidase （NAG）（by 180.4% and 233.9%， respectively）， and increased abundance of amoA genes of ammonia-oxidizing archaea （AOA） and ammonia-oxidizing bacteria （AOB）（by 74.6% and 68.0%， respectively）. Compared with CK， PL significantly decreased soil C/N （by 11.3%）， decreased soil organic carbon （SOC） and microbial biomass nitrogen （MBN） concentrations （by 13.6% and 72.8%， respectively）. Compared with PL， PL+MR significantly decreased soil DOC concentration （by 12.8%）， significantly reduced BG， NAG， leucine aminopeptidase （LAP） and acid phosphatase （AP） activities （by 49.1%， 59.9%， 31.6%， and 25.0%， respectively）， and decreased AOA-amoA， AOB-amoA， and nosZ I genes abundance （by 46.5%， 59.5%， and 23.1%， respectively）. Compared with PL， PL+MR significantly increased MBN concentration （by 29.1%）. Correlation analyses showed that cumulative soil N₂O emissions were significantly positively correlated with the pH， DOC concentration， extracellular enzyme activity， and abundance of genes related to the nitrogen cycling （except nirS）， and significantly negatively correlated with C/N， SOC and MBN concentrations. The abundance of AOA-amoA and AOB-amoA were the key factors affecting N₂O emissions. In summary， plowing resulted in enhanced soil extracellular enzyme activity and amoA gene abundance， as well as increased SOC decomposition and consumption and N₂O emissions. Mulching with plant residues effectively alleviated these negative effects， indicating that it is a feasible improvement measure.

Key words: plowing, plant residue mulching, alpine meadow, nitrogen cycle functional genes, soil nitrous oxide emission

Ya-si FENG, Wen-ting JIANG, Yi-hong LIU, Yan WANG, Yuan LI, You-chao CHEN, Yan-jiang CAI. Effects of plowing and plant residue mulching on soil nitrous oxide emissions in a black soil beach-type degraded grassland[J]. Acta Prataculturae Sinica, 2024, 33(11): 15-29.

Figures/Tables 9

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基因Gene	引物名称及序列 Primers names and sequences （5′-3′）	片段长度Fragment length （bp）	热循环Thermal condition
AOA-amoA	Arch-amoAF： STAATGGTCTGGCTTAGACG Arch-amoAR： GCGGCCATCCATCTGTATGT	635	94 ℃预变性 5 min；94 ℃变性 30 s，55 ℃退火 45 s，72 ℃延伸 60 s，40 个循环Pre-denaturation at 94 ℃ for 5 min； 40 cycles of denaturation at 94 ℃ for 30 s， annealing at 55 ℃ for 45 s and extension at 72 ℃ for 60 s
AOB-amoA	amoA-1F： GGGGTTTCTACTGGTGGT amoA-2R： CCCCTCKGSAAAGCCTTCTTC	491	94 ℃预变性 5 min；94 ℃变性 30 s，57 ℃退火 45 s，72 ℃延伸 30 s，40 个循环Pre-denaturation at 94 ℃ for 5 min； 40 cycles of denaturation at 94 ℃ for 30 s， annealing at 57 ℃ for 45 s and extension at 72 ℃ for 30 s
nirS	nirSCd3aF： GTSAACGTSAAGGARACSGG nirSR3cd： GASTTCGGRTGSGTCTTGA	406	95 ℃预变性 3 min；95 ℃ 变性 10 s，56 ℃退火 30 s，72 ℃延伸 20 s，35 个循环Pre-denaturation at 95 ℃ for 3 min； 35 cycles of denaturation at 95 ℃ for 10 s， annealing at 56 ℃ for 30 s and extension at 72 ℃ for 20 s
nirK	nirKF1aCu： ATCATGGTSCTGCCGCG nirKR3Cu： GCCTCGATCAGRTTGTGGTT	473	95 ℃预变性 3 min；95 ℃变性 30 s，56 ℃退火 30 s，72 ℃延伸 20 s，35 个循环Pre-denaturation at 95 ℃ for 3 min； 35 cycles of denaturation at 95 ℃ for 30 s， annealing at 56 ℃ for 30 s and extension at 72 ℃ for 20 s
nosZ I	NosZ1840F： CGCRACGGCAASAAGGTSMSSGT NosZ2090R： CAKRTGCAKSGCRTGGCAGAA	259	95 ℃预变性 3 min；95 ℃变性 10 s，58 ℃退火 25 s，72 ℃延伸 20 s，35 个循环Pre-denaturation at 95 ℃ for 3 min； 35 cycles of denaturation at 95 ℃ for 10 s， annealing at 58 ℃ for 25 s and extension at 72 ℃ for 20 s

基因Gene	引物名称及序列 Primers names and sequences （5′-3′）	片段长度Fragment length （bp）	热循环Thermal condition
AOA-amoA	Arch-amoAF： STAATGGTCTGGCTTAGACG Arch-amoAR： GCGGCCATCCATCTGTATGT	635	94 ℃预变性 5 min；94 ℃变性 30 s，55 ℃退火 45 s，72 ℃延伸 60 s，40 个循环Pre-denaturation at 94 ℃ for 5 min； 40 cycles of denaturation at 94 ℃ for 30 s， annealing at 55 ℃ for 45 s and extension at 72 ℃ for 60 s
AOB-amoA	amoA-1F： GGGGTTTCTACTGGTGGT amoA-2R： CCCCTCKGSAAAGCCTTCTTC	491	94 ℃预变性 5 min；94 ℃变性 30 s，57 ℃退火 45 s，72 ℃延伸 30 s，40 个循环Pre-denaturation at 94 ℃ for 5 min； 40 cycles of denaturation at 94 ℃ for 30 s， annealing at 57 ℃ for 45 s and extension at 72 ℃ for 30 s
nirS	nirSCd3aF： GTSAACGTSAAGGARACSGG nirSR3cd： GASTTCGGRTGSGTCTTGA	406	95 ℃预变性 3 min；95 ℃ 变性 10 s，56 ℃退火 30 s，72 ℃延伸 20 s，35 个循环Pre-denaturation at 95 ℃ for 3 min； 35 cycles of denaturation at 95 ℃ for 10 s， annealing at 56 ℃ for 30 s and extension at 72 ℃ for 20 s
nirK	nirKF1aCu： ATCATGGTSCTGCCGCG nirKR3Cu： GCCTCGATCAGRTTGTGGTT	473	95 ℃预变性 3 min；95 ℃变性 30 s，56 ℃退火 30 s，72 ℃延伸 20 s，35 个循环Pre-denaturation at 95 ℃ for 3 min； 35 cycles of denaturation at 95 ℃ for 30 s， annealing at 56 ℃ for 30 s and extension at 72 ℃ for 20 s
nosZ I	NosZ1840F： CGCRACGGCAASAAGGTSMSSGT NosZ2090R： CAKRTGCAKSGCRTGGCAGAA	259	95 ℃预变性 3 min；95 ℃变性 10 s，58 ℃退火 25 s，72 ℃延伸 20 s，35 个循环Pre-denaturation at 95 ℃ for 3 min； 35 cycles of denaturation at 95 ℃ for 10 s， annealing at 58 ℃ for 25 s and extension at 72 ℃ for 20 s

指标Index	CK	PL	MR	PL+MR
土壤质量含水量Soil water content （SWC， %）	44.26±1.43b	38.27±1.77c	49.04±1.49a	41.59±2.18bc
土壤pH值Soil pH value	5.37±0.02b	5.51±0.04a	5.44±0.03a	5.48±0.03a
土壤有机碳Soil organic carbon （SOC， g·kg^-1）	57.11±3.27a	49.34±2.31b	53.02±3.54ab	52.63±1.98ab
总氮Total nitrogen （TN， g·kg^-1）	4.82±0.15a	4.62±0.17a	4.54±0.24a	4.79±0.19a
铵态氮Ammonium nitrogen （NH₄⁺-N， mg·kg^-1）	5.88±0.50a	4.32±0.58b	3.56±0.40b	3.75±0.46b
硝态氮Nitrate nitrogen （NO₃^--N， mg·kg^-1）	40.23±3.69b	37.06±1.41b	48.22±2.62a	36.61±2.42b
可溶性有机碳Dissolved organic carbon （DOC， mg·kg^-1）	53.15±8.33c	164.51±10.39a	54.12±2.50c	143.37±4.93b
可溶性有机氮Dissolved organic nitrogen （DON， mg·kg^-1）	23.08±2.85a	12.81±5.41b	21.65±3.89a	14.91±2.19ab
土壤C/N Soil C/N	12.05±0.04a	10.69±0.09c	11.82±0.07b	10.77±0.08c

指标Index	CK	PL	MR	PL+MR
土壤质量含水量Soil water content （SWC， %）	44.26±1.43b	38.27±1.77c	49.04±1.49a	41.59±2.18bc
土壤pH值Soil pH value	5.37±0.02b	5.51±0.04a	5.44±0.03a	5.48±0.03a
土壤有机碳Soil organic carbon （SOC， g·kg^-1）	57.11±3.27a	49.34±2.31b	53.02±3.54ab	52.63±1.98ab
总氮Total nitrogen （TN， g·kg^-1）	4.82±0.15a	4.62±0.17a	4.54±0.24a	4.79±0.19a
铵态氮Ammonium nitrogen （NH₄⁺-N， mg·kg^-1）	5.88±0.50a	4.32±0.58b	3.56±0.40b	3.75±0.46b
硝态氮Nitrate nitrogen （NO₃^--N， mg·kg^-1）	40.23±3.69b	37.06±1.41b	48.22±2.62a	36.61±2.42b
可溶性有机碳Dissolved organic carbon （DOC， mg·kg^-1）	53.15±8.33c	164.51±10.39a	54.12±2.50c	143.37±4.93b
可溶性有机氮Dissolved organic nitrogen （DON， mg·kg^-1）	23.08±2.85a	12.81±5.41b	21.65±3.89a	14.91±2.19ab
土壤C/N Soil C/N	12.05±0.04a	10.69±0.09c	11.82±0.07b	10.77±0.08c

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