J Plant Ecol ›› 2022, Vol. 15 ›› Issue (4): 721-732 .DOI: 10.1093/jpe/rtac015

• Research Articles • Previous Articles     Next Articles

Greater soil microbial biomass loss at low frequency of N addition in an Inner Mongolia grassland

Qiushi Ning1, Liangchao Jiang1,2, *, Ruzhen Wang3,4, Jing Wang1, Xingguo Han1,2, * and Junjie Yang1,2, *   

  1. 1 State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China, 2 University of Chinese Academy of Sciences, Beijing 100049, China, 3 Erguna Forest-Steppe Ecotone Ecosystem Research Station, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, China, 4 School of Life Sciences, Hebei University, Baoding 071002, China

    *Corresponding author. E-mail: jianglc@ibcas.ac.cn (L.J.); xghan@ibcas.ac.cn (X.H.); yangjunjie@ibcas.ac.cn (J.Y.)
  • Received:2022-01-29 Revised:2022-02-09 Accepted:2022-02-14 Online:2022-02-17 Published:2022-08-01

Abstract: Soil microbial biomass is critical for biogeochemical cycling and serves as precursor for carbon (C) sequestration. The anthropogenic nitrogen (N) input has profoundly changed the pool of soil microbial biomass. However, traditional N deposition simulation experiments have been exclusively conducted through infrequent N addition, which may have caused biased effects on soil microbial biomass compared with those under the natural and continuous N deposition. Convincing data are still scarce about how the different N addition frequencies affect soil microbial biomass. By independently manipulating the frequencies (2 times vs. 12 times N addition yr–1) and the rates (0–50 g N m−2 yr−1) of N addition, our study aimed to examine the response of soil microbial biomass C (MBC) to different N addition frequencies with increasing N addition rates. Soil MBC gradually decreased with increasing N addition rates under both N addition frequencies, while the soil MBC decreased more at low frequency of N addition, suggesting that traditional studies have possibly overestimated the effects of N deposition on soil microbial biomass. The greater soil microbial biomass loss with low N frequency resulted from the intensified soil acidification, higher soil inorganic N, stronger soil C and N imbalance, less net primary production allocated to belowground and lower fungi to bacteria ratio. To reliably predict the effects of atmospheric N deposition on soil microbial functioning and C cycling of grassland ecosystems in future studies, it is necessary to employ both the dosage and the frequency of N addition.

Key words: nitrogen addition frequency, temperate grasslands, nutrient imbalance, fungi to bacteria ratio, plant–microbe interaction, belowground net primary production, Shannon–Weiner diversity index

土壤微生物生物量在生物地球化学循环过程中至关重要,是土壤碳固持的前体物质。人为氮输入深刻地改变了草地土壤微生物生物量。然而,传统氮沉降模拟实验仅通过低频率的氮添加进行,与持续高频率的自然氮沉降相比,对土壤微生物生物量的影响可能存在差异。不同频率的氮添加对土壤微生物生物量的影响尚缺乏可靠的数据支撑。本研究通过在不同的氮添加速率(0–50 g N m−2 yr−1)下,控制氮添加频率(每年2次和12次),研究了土壤微生物生物量碳对不同氮添加频率的响应。研究结果表明,在两种氮添加频率下,随着施氮水平的提高,土壤微生物生物量碳逐渐降低。然而,在低施氮频率下,土壤微生物生物量的下降幅度更大,这说明传统的氮添加实验可能高估了氮沉降对土壤微生物生物量的影响。在低施氮频率下,土壤酸化、无机氮积累、碳氮失衡、地下净初级生产力分配减少和真菌细菌比例降低等情况加剧,导致微生物生物量出现较大幅度下降。在未来研究中,为可靠预测氮沉降对草地生态系统土壤微生物功能和碳循环的影响,不仅要考虑氮添加的剂量,还需要考虑氮添加的频率。

关键词: 氮添加频率, 温带草原, 真菌细菌比例, 养分失衡, 植物微生物相互作用, 地下净初级生产力, 香农-威纳多样性指数