Microbial carbon-nitrogen imbalance affects the response of microbial nitrogen use efficiency to nitrogen enrichment in Castanopsis faberi forest soils

doi:10.17521/cjpe.2024.0350

Abstract

Abstract:

Aims Microbial nitrogen use efficiency (NUE) refers to the ratio of nitrogen used by microorganisms for growth to total organic nitrogen absorbed, which is a key regulator of the soil nitrogen cycle. The ¹⁸O-H₂O method and eco-enzyme stoichiometric model are the most common techniques employed to estimate microbial NUE. However, the impact of nitrogen enrichment on microbial NUE in forest soils remains to be elucidated, which would significantly impede the accurate prediction of soil nitrogen supply.

Methods In this study, we sampled the soils from subtropical Castanopsis faberi forests and used urea to simulate atmospheric nitrogen deposition. In total, three levels of nitrogen additions were set up, including control (CK, 0 kg N·hm^-2·a^-1), low nitrogen (LN, 40 kg N·hm^-2·a^-1), and high nitrogen (HN, 80 kg N·hm^-2·a^-1) treatments. The ¹⁸O-H₂O method and eco-enzyme stoichiometric model were used to compare the differences in soil microbial NUE under different nitrogen enrichment levels. Furthermore, soil physicochemical properties, microbial biomass, extracellular enzyme activity, and stoichiometric imbalance were also measured to explore the factors that influence the response of microbial NUE to nitrogen enrichment.

Important findings The results showed that the microbial NUE, as determined by two different methods, exhibited a decline with the increase of nitrogen enrichment. The vector angle values of different nitrogen treatments were all greater than 55°, indicating that soil microorganisms in this study area were generally phosphorus limited, but nitrogen enrichment did not exacerbate the phosphorus limitation. On the contrary, nitrogen enrichment has a significant negative effect on microbial carbon and nitrogen imbalance, and a positive correlation was observed between microbial NUE and microbial carbon and nitrogen imbalance. In summary, the nitrogen enrichment may have a detrimental effect on soil nitrogen storage in subtropical forests, highlighting the necessity to enhance soil nitrogen storage by means of regulating the soil stoichiometric balance in these forests.

Key words: microbial nitrogen use efficiency, nitrogen addition, ecological stoichiometry, isotope labeling, forest

PI Hui-Zhi, ZHANG Qiu-Fang, SUN Hao, ZENG Quan-Xin, PENG Yuan-Zhen, YUAN Xiao-Chun, XU Jian-Guo, CHEN Yue-Min. Microbial carbon-nitrogen imbalance affects the response of microbial nitrogen use efficiency to nitrogen enrichment in Castanopsis faberi forest soils[J]. Chin J Plant Ecol, 2026, 50(1): 34-44.

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URL: https://www.plant-ecology.com/EN/10.17521/cjpe.2024.0350

https://www.plant-ecology.com/EN/Y2026/V50/I1/34

Figures/Tables 4

References 57

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指标 Index	对照 CK	低氮 LN	高氮 HN	p
土壤理化性质 Soil physical and chemical property
土壤pH Soil pH	4.37 ± 0.02^a	4.29 ± 0.04^ab	4.27 ± 0.02^b	0.07
土壤总有机碳含量 SOC content (g·kg^-1)	52.64 ± 0.74^b	57.80 ± 0.86^a	57.80 ± 1.35^a	0.01
总氮含量 Total N content (g·kg^-1)	1.97 ± 0.25^c	3.07 ± 0.05^b	4.51 ± 0.45^a	<0.01
总磷含量 Total P content (g·kg^-1)	0.34 ± 0.02^a	0.24 ± 0.01^b	0.19 ± 0.01^c	<0.01
可溶性有机碳含量 DOC content (mg·kg^-1)	148.33 ± 9.92^a	140.79 ± 4.75^a	117.22 ± 2.89^b	0.02
无机氮含量 IN content (mg·kg^-1)	24.20 ± 0.82^b	34.29 ± 2.08^a	35.23 ± 1.03^a	<0.01
有效磷含量 AP content (mg·kg^-1)	3.24 ± 0.38	3.01 ± 0.14	3.24 ± 0.18	0.77
酶活性和微生物生物量 Enzyme activity and microbial biomass
β-葡萄糖苷酶活性 βG activity (nmol·g^-1·h^-1)	7.76 ± 0.09^a	6.70 ± 0.64^a	4.99 ± 0.22^b	<0.01
β-N-乙酰氨基葡萄糖苷酶活性 NAG activity (nmol·g^-1·h^-1)	21.90 ± 1.29	23.37 ± 1.40	20.38 ± 0.77	0.26
亮氨酸氨肽酶活性 LAP activity (nmol·g^-1·h^-1)	2.31 ± 0.40	1.62 ± 0.32	1.61 ± 0.39	0.36
酸性磷酸酶活性 ACP activity (nmol·g^-1·h^-1)	880.39 ± 4.71	684.72 ± 122.17	680.25 ± 98.62	0.26
微生物生物量碳含量 MBC content (mg·kg^-1)	1035.94 ± 59.24	1025.00 ± 58.28	1005.38 ± 48.22	0.93
微生物生物量氮含量 MBN content (mg·kg^-1)	79.87 ± 2.51^b	85.54 ± 3.77^b	96.79 ± 2.60^a	0.01
微生物生物量磷含量 MBP content (mg·kg^-1)	220.06 ± 17.14^a	177.93 ± 5.41^b	144.53 ± 5.81^b	<0.01
化学计量比 Stoichiometric ratio
DOC:IN	6.20 ± 0.64^a	4.14 ± 0.22^b	3.33 ± 0.02^b	<0.01
DOC:AP	46.98 ± 4.35	47.31 ± 3.97	36.38 ± 1.26	0.09
IN:AP	7.84 ± 1.08^b	11.52 ± 1.17^a	10.93 ± 0.37^a	0.05
MBC:MBN	13.01 ± 0.85^a	12.02 ± 0.67^ab	10.40 ± 0.54^b	0.07
MBC:MBP	4.74 ± 0.16^c	5.78 ± 0.41^b	6.95 ± 0.18^a	<0.01
MBN:MBP	0.37 ± 0.03^c	0.48 ± 0.03^b	0.67 ± 0.02^a	<0.01
βG:(NAG + LAP)	0.32 ± 0.02^a	0.28 ± 0.04^ab	0.23 ± 0.00^b	0.10
βG:ACP	0.01 ± 0.01	0.01 ± 0.01	0.01 ± 0.01	0.41
(NAG + LAP):ACP	0.03 ± 0.01	0.04 ± 0.01	0.03 ± 0.01	0.15
化学计量不平衡 Stoichiometric imbalance
碳:氮计量不平衡 Imbalance C:N	0.47 ± 0.03^a	0.35 ± 0.02^b	0.32 ± 0.02^b	<0.01
碳:磷计量不平衡 Imbalance C:P	10.01 ± 1.16^a	8.38 ± 1.16^a	5.24 ± 0.21^b	0.02
氮:磷计量不平衡 Imbalance N:P	21.67 ± 3.59	24.20 ± 2.90	16.36 ± 0.98	0.17
矢量长度 Vector length	0.24 ± 0.02^a	0.21 ± 0.05^ab	0.19 ± 0.01^b	0.07
矢量角度 Vector angle (°)	87.94 ± 0.22	87.18 ± 0.76	87.61 ± 0.63	0.23

指标 Index	对照 CK	低氮 LN	高氮 HN	p
土壤理化性质 Soil physical and chemical property
土壤pH Soil pH	4.37 ± 0.02^a	4.29 ± 0.04^ab	4.27 ± 0.02^b	0.07
土壤总有机碳含量 SOC content (g·kg^-1)	52.64 ± 0.74^b	57.80 ± 0.86^a	57.80 ± 1.35^a	0.01
总氮含量 Total N content (g·kg^-1)	1.97 ± 0.25^c	3.07 ± 0.05^b	4.51 ± 0.45^a	<0.01
总磷含量 Total P content (g·kg^-1)	0.34 ± 0.02^a	0.24 ± 0.01^b	0.19 ± 0.01^c	<0.01
可溶性有机碳含量 DOC content (mg·kg^-1)	148.33 ± 9.92^a	140.79 ± 4.75^a	117.22 ± 2.89^b	0.02
无机氮含量 IN content (mg·kg^-1)	24.20 ± 0.82^b	34.29 ± 2.08^a	35.23 ± 1.03^a	<0.01
有效磷含量 AP content (mg·kg^-1)	3.24 ± 0.38	3.01 ± 0.14	3.24 ± 0.18	0.77
酶活性和微生物生物量 Enzyme activity and microbial biomass
β-葡萄糖苷酶活性 βG activity (nmol·g^-1·h^-1)	7.76 ± 0.09^a	6.70 ± 0.64^a	4.99 ± 0.22^b	<0.01
β-N-乙酰氨基葡萄糖苷酶活性 NAG activity (nmol·g^-1·h^-1)	21.90 ± 1.29	23.37 ± 1.40	20.38 ± 0.77	0.26
亮氨酸氨肽酶活性 LAP activity (nmol·g^-1·h^-1)	2.31 ± 0.40	1.62 ± 0.32	1.61 ± 0.39	0.36
酸性磷酸酶活性 ACP activity (nmol·g^-1·h^-1)	880.39 ± 4.71	684.72 ± 122.17	680.25 ± 98.62	0.26
微生物生物量碳含量 MBC content (mg·kg^-1)	1035.94 ± 59.24	1025.00 ± 58.28	1005.38 ± 48.22	0.93
微生物生物量氮含量 MBN content (mg·kg^-1)	79.87 ± 2.51^b	85.54 ± 3.77^b	96.79 ± 2.60^a	0.01
微生物生物量磷含量 MBP content (mg·kg^-1)	220.06 ± 17.14^a	177.93 ± 5.41^b	144.53 ± 5.81^b	<0.01
化学计量比 Stoichiometric ratio
DOC:IN	6.20 ± 0.64^a	4.14 ± 0.22^b	3.33 ± 0.02^b	<0.01
DOC:AP	46.98 ± 4.35	47.31 ± 3.97	36.38 ± 1.26	0.09
IN:AP	7.84 ± 1.08^b	11.52 ± 1.17^a	10.93 ± 0.37^a	0.05
MBC:MBN	13.01 ± 0.85^a	12.02 ± 0.67^ab	10.40 ± 0.54^b	0.07
MBC:MBP	4.74 ± 0.16^c	5.78 ± 0.41^b	6.95 ± 0.18^a	<0.01
MBN:MBP	0.37 ± 0.03^c	0.48 ± 0.03^b	0.67 ± 0.02^a	<0.01
βG:(NAG + LAP)	0.32 ± 0.02^a	0.28 ± 0.04^ab	0.23 ± 0.00^b	0.10
βG:ACP	0.01 ± 0.01	0.01 ± 0.01	0.01 ± 0.01	0.41
(NAG + LAP):ACP	0.03 ± 0.01	0.04 ± 0.01	0.03 ± 0.01	0.15
化学计量不平衡 Stoichiometric imbalance
碳:氮计量不平衡 Imbalance C:N	0.47 ± 0.03^a	0.35 ± 0.02^b	0.32 ± 0.02^b	<0.01
碳:磷计量不平衡 Imbalance C:P	10.01 ± 1.16^a	8.38 ± 1.16^a	5.24 ± 0.21^b	0.02
氮:磷计量不平衡 Imbalance N:P	21.67 ± 3.59	24.20 ± 2.90	16.36 ± 0.98	0.17
矢量长度 Vector length	0.24 ± 0.02^a	0.21 ± 0.05^ab	0.19 ± 0.01^b	0.07
矢量角度 Vector angle (°)	87.94 ± 0.22	87.18 ± 0.76	87.61 ± 0.63	0.23