人工草地土壤有机碳组分与微生物群落对施氮补水的响应

doi:10.3864/j.issn.0578-1752.2020.13.016

Abstract

Abstract:

【Objective】 Establishment of artificial grassland provides one solution for releasing some of the grazing pressure on natural grassland, and thus is conducive to the restoration of degraded grassland. The present study aimed to investigate the effects of nitrogen (N) addition and water supplement on soil organic carbon (SOC) fractionation, composition and activity of soil microbial community on artificial grassland established in Hulunber region, so as to provide insight into the effect of management practices on SOC sequestration and stability of artificial grassland. 【Method Experimental plots were designed with two factors of N addition (0, and 150 kg N·hm^-2·a^-1) and water addition (0, and 60 mm), and were constructed under three types of artificial grasslands, i.e., alfalfa monoculture, smooth bromegrass monoculture, and the mixed cultivation of alfalfa and smooth bromegrass. Soil samples were collected from experimental plots and SOC of bulk soil was fractionated into different particulate-size fractions by wet-sieving method. The abundance, composition and activity of soil microbial community were measured by phospholipid fatty acids (PLFA) and extracellular enzyme activity. Then, the effects of N addition and watering treatments on SOC fractions and soil microbial community, and investigated the relationship between these two components were analyzed. 【Result】 Three years of N fertilization and water addition exerted significant impact on SOC fractionation. Addition of N generally increased the content of particulate organic carbon (POC) in soils of alfalfa monoculture and the mixed cultivation but decreased the content of mineral associated organic carbon (MAOC), while water addition significantly increased the content of coarse POC in soils of smooth bromegrass monoculture. The activities of four soil extracellular enzymes but not the abundance or composition of soil microbial community were significantly affected by N and water addition. Nitrogen application without water addition significantly inhibited the activity of β-N-acetylglucosidase (NAG) in soils of alfalfa monoculture, but promoted that in soils of smooth bromegrass monoculture. The activities of cellobiohydorlase (CB) and NAG were significantly decreased by water addition in soils of two monoculture grasslands. Nitrogen application with water addition significantly inhibited the activities of β-glucosidase (βG), CB and NAG in soils of alfalfa monoculture, but significantly promoted CB activity in soils of the mixed cultivation. The changes in PLFA concentration of total community and specific microbial groups were positively correlated with changes in content of POC, but negatively correlated with MAOC. There were negative correlations between the activities of βG and CB, as well as the ratio of enzyme C/N and C/P with changes in POC content, and these correlations were stronger under treatments with water addition. 【Conclusion】 Results of the present study showed that in artificial grassland established in semi-arid Hulunbeier region, the addition of N fertilization significantly promoted the accumulation of labile SOC fraction, but decreased the proportion of recalcitrant fraction, which reduced the stability of soil carbon sequestration. Nitrogen fertilization and water supplement induced significant changes in activity of soil microbial communities, and these changes in enzyme stoichiometric ratios were closely related to changes in SOC fractions. These results implied that the differential demands for C, N and P by microbial communities were crucial in regulating the turnover of labile SOC fraction in artificial grassland.

Key words: artificial grassland, nitrogen addition, water addition, soil organic carbon, soil microbial community, extracellular enzyme activity, enzyme stoichiometric ratio, Hulunber

XU Meng,XU LiJun,CHENG ShuLan,FANG HuaJun,LU MingZhu,YU GuangXia,YANG Yan,GENG Jing,CAO ZiCheng,LI YuNa. Responses of Soil Organic Carbon Fractionation and Microbial Community to Nitrogen and Water Addition in Artificial Grassland[J].Scientia Agricultura Sinica, 2020, 53(13): 2678-2690.

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酶 Enzyme	缩写 Abbreviation	底物 Substrate
β-葡萄糖苷酶β-glucosidase	βG	4-MUB-β-D-glucoside
纤维二糖水解酶 Cellobiohydorlase	CB	4-MUB-β-D-cellobioside
β-N-乙酰氨基葡萄糖苷酶β-N-acetylglucosidase	NAG	4-MUB-N-acetyl-β-D-glucosaminide
酸性磷酸酶 Acid phosphatase	AP	4-MUB-phosphate

处理 Treatment	pH	有机碳 SOC (g·kg^-1)	总氮 TN (g·kg^-1)	硝态氮 NO₃^--N (mg·kg^-1)	铵态氮 NH₄⁺-N (mg·kg^-1)	总可溶性氮 TDN (mg kg^-1)	土壤水分 Soil moisture (%)
苜蓿单播 Alfalfa monoculture
CK	7.0±0.4a	21.6±1.5a	2.1±0.1a	27.0±2.6c	4.6±0.4a	51.3±1.2c	12.4±0.3a
N	7.1±0.4a	20.2±0.7a	2.0±0.1a	52.9±6.9b	6.1±0.8a	78.8±6.8b	12.8±0.4a
W	6.6±0.5a	22.0±1.0a	2.1±0.1a	28.7±1.8c	5.4±0.8a	54.3±3.3c	13.6±0.6a
N+W	6.4±0.5a	21.3±1.0a	2.2±0.1a	78.3±11.4a	6.6±1.4a	103.8±11.4a	12.7±0.8a
无芒雀麦单播 Smooth bromegrass monoculture
CK	7.2±0.2a	20.6±0.1a	2.1±0.0a	28.6±2.2b	4.7±0.8a	54.7±2.9b	12.5±0.9a
N	6.6±0.2a	21.4±0.5a	2.2±0.0a	81.3±19.4a	6.4±0.9a	121.2±26.1a	13.0±0.9a
W	7.2±0.2a	19.6±1.3a	2.0±0.1a	40.4±9.0b	4.9±0.4a	67.1±10.0b	13.0±1.1a
N+W	7.0±0.3a	20.4±0.8a	2.0±0.1a	55.4±7.6ab	4.8±0.9a	80.9±9.0ab	12.2±0.5a
苜蓿-无芒雀麦混播 Mixed cultivation
CK	6.8±0.2a	21.6±1.2a	2.1±0.1a	29.9±3.0b	5.6±1.0a	55.7±4.7b	12.9±0.5a
N	6.8±0.3a	21.8±1.4a	2.2±0.1a	72.3±7.8a	6.0±1.7a	104.6±6.8a	13.1±0.7a
W	7.0±0.2a	22.5±0.8a	2.2±0.1a	25.8±3.8b	6.0±0.9a	54.4±4.3b	12.4±0.3a
N+W	7.1±0.3a	21.8±2.3a	2.2±0.2a	78.1±10.3a	5.8±0.7a	109.1±11.6a	12.4±0.4a

处理 Treatment	总磷脂脂肪酸含量 Total PLFA	革兰氏阳性细菌 Gram-positive bacteria	革兰氏阴性细菌 Gram-negative bacteria	真菌 Fungi	丛枝菌根真菌 AMF	真菌细菌比 F/B	革兰氏阳性/ 阴性细菌比 G+/G-
苜蓿单播 Alfalfa monoculture
CK	25.1±1.7a	10.2±0.8a	8.3±0.5a	2.5±0.2a	0.86±0.07a	0.137±0.003a	1.23±0.05a
N	21.7±2.7a	8.7±1.1a	7.3±0.8a	2.4±0.4a	0.72±0.09a	0.147±0.006a	1.19±0.03a
W	25.6±3.2a	10.3±1.2a	8.6±1.1a	2.6±0.4a	0.87±0.12a	0.137±0.006a	1.21±0.04a
N+W	26.0±2.3a	10.5±0.9a	8.6±0.8a	2.7±0.3a	0.83±0.09a	0.143±0.002a	1.22±0.03a
无芒雀麦单播 Smooth bromegrass monoculture
CK	23.9±2.6a	9.7±1.1a	7.8±0.8a	2.4±0.3a	0.88±0.10a	0.138±0.008a	1.24±0.02a
N	22.8±2.3a	9.5±0.8a	7.4±0.8a	2.2±0.2a	0.79±0.14a	0.128±0.003a	1.28±0.02a
W	21.7±1.6a	8.8±0.6a	7.1±0.6a	2.3±0.2a	0.75±0.06a	0.143±0.001a	1.25±0.04a
N+W	22.6±1.8a	9.2±0.7a	7.5±0.6a	2.2±0.2a	0.79±0.04a	0.133±0.004a	1.22±0.02a
苜蓿-无芒雀麦混播 Mixed cultivation
CK	22.1±1.1ab	9.1±0.5ab	7.3±0.3ab	2.2±0.1a	0.73±0.03ab	0.132±0.004a	1.25±0.04a
N	25.9±1.6a	10.2±0.7a	8.8±0.5a	2.6±0.2a	0.95±0.07a	0.135±0.003a	1.16±0.02a
W	21.2±2.4ab	8.7±0.9ab	6.9±0.7ab	2.1±0.3a	0.73±0.10ab	0.135±0.005a	1.26±0.05a
N+W	19.8±1.4b	7.8±0.6b	6.8±0.5b	3.0±0.2a	0.69±0.06b	0.144±0.002a	1.15±0.04a

处理 Treatment	土壤酶C/N比 Enzyme C/N		土壤酶C/P比 Enzyme C/P
处理 Treatment	βG/NAG	CB/NAG	βG/AP	CB/AP
苜蓿单播 Alfalfa monoculture
CK	6.5±0.6c	0.33±0.11b	0.58±0.05a	0.033±0.004a
N	12.4±0.6a	0.65±0.11a	0.75±0.06a	0.035±0.006a
W	10.2±1.6ab	0.30±0.02b	0.77±0.14a	0.037±0.006a
N+W	7.7±1.3bc	0.15±0.04b	0.61±0.13a	0.032±0.001a
无芒雀麦单播 Smooth bromegrass monoculture
CK	7.7±0.3a	0.30±0.05a	0.84±0.07a	0.057±0.010a
N	6.4±0.1a	0.32±0.01a	0.70±0.07a	0.052±0.009a
W	8.0±1.0a	0.32±0.07a	1.47±0.33a	0.069±0.006a
N+W	6.8±0.6a	0.28±0.08a	1.25±0.27a	0.087±0.027a
苜蓿-无芒雀麦混播 Mixed cultivation
CK	9.9±0.7a	0.32±0.03ab	0.86±0.12a	0.034±0.003b
N	9.0±0.4a	0.26±0.05b	0.75±0.08a	0.036±0.002b
W	9.5±1.5a	0.40±0.05a	0.91±0.10a	0.038±0.006ab
N+W	8.9±0.5a	0.40±0.04a	1.15±0.20a	0.059±0.012a

项目 Item	全部处理 All treatments				不补水 No water addition			补水 With water addition
项目 Item	Coarse POC	Fine POC	POC	MAOC	Coarse POC	POC	MAOC	Coarse POC	Fine POC	POC	MAOC
土壤微生物量 Soil microbial biomass
PLFA总量 Total PLFA	—	0.424*	0.486*	-0.657**	—	0.554?	-0.679*	—	0.679*	0.534?	-0.767**
革兰氏阳性细菌 G+	—	0.426*	0.461*	-0.628**	—	0.520?	-0.616*	—	0.682*	—	-0.781**
革兰氏阴性细菌 G-	0.390?	0.366?	0.435*	-0.629**	—	0.538?	-0.772**	—	0.585?	—	-0.635*
真菌 Fungi	—	0.419*	0.498*	-0.623**	—	0.574?	-0.660*	0.585?	0.564?	0.550?	-0.733*
丛枝菌根真菌 AMF	0.464*	0.378?	0.508*	-0.632**	—	0.558?	-0.710*	0.617*	0.627*	0.563?	-0.596?
土壤酶活性 Extracellular enzyme activity
βG	—	—	—	—	-0.642*	—	0.685*	—	—	-0.709*	—
CB	—	—	—	—	-0.651*	—	0.711*	—	—	-0.748*	—
土壤酶化学计量比 Enzyme stoichiometric ratio
βG/NAG	—	—	—	—	—	—	—	—	—	-0.581?	—
CB/NAG	—	—	—	—	-0.691*	—	0.607?	—	—	-0.540?	—
βG/AP	—	-0.463*	-0.476*	0.404?	—	—	—	—	-0.797**	-0.821**	—
CB/AP	—	—	—	—	—	—	0.572?	—	-0.572?	-0.667*	—

Responses of Soil Organic Carbon Fractionation and Microbial Community to Nitrogen and Water Addition in Artificial Grassland

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