引用本文:曹子铖,程淑兰,方华军,徐 梦,耿 静,卢明珠,杨 艳,李玉娜.温带针阔叶林土壤有机碳动态和微生物群落结构对有机氮添加的响应特征[J].土壤学报,2020,57(4):963-974. DOI:10.11766/trxb201908130350
CAO Zicheng,CHENG Shulan,FANG Huajun,XU Meng,GENG Jing,LU Mingzhu,YANG Yan,LI Yuna.Responses of Soil Organic Carbon Dynamics and Microbial Community Structure to Organic Nitrogen Fertilization in the Temperate Needle-broadleaved Mixed Forest[J].Acta Pedologica Sinica,2020,57(4):963-974. DOI:10.11766/trxb201908130350
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温带针阔叶林土壤有机碳动态和微生物群落结构对有机氮添加的响应特征
曹子铖1, 程淑兰1, 方华军1, 徐 梦2, 耿 静2, 卢明珠2, 杨 艳2, 李玉娜1
1.中国科学院大学资源与环境学院;2.中国科学院地理科学与资源研究所
摘要:
森林生态系统土壤有机碳(soil organic carbon, SOC)转化和碳储量动态对大气氮沉降增加的响应是具有特异性的,取决于土壤初始氮状态、施氮类型、剂量与持续时间。过去相关研究主要集中在无机氮沉降效应方面,对有机氮沉降如何影响温带针阔混交林SOC及其组分含量尚不清楚,鲜有研究关注氮素富集条件下SOC变化的微生物学机制。以长白山温带针阔混交林为研究对象,设置4个尿素添加水平(0、40、80、120 kg•hm-2•a-1。以N计,下同)的原位控制试验。施肥三年后,采集0~10 cm矿质层土壤样品,测定土壤不同形态氮含量、土壤团聚体比例和不同粒径SOC含量;利用磷脂脂肪酸(PLFA)技术测定土壤微生物不同种群相对丰度与群落结构,探讨SOC含量变化与微生物群落变化之间的相关关系。结果表明,施氮三年显著增加了土壤NO3--N、DON和TN含量,土壤酸化明显。施氮虽然未显著增加表层土壤总SOC含量,但是显著增加活性SOC组分(颗粒态有机碳和团聚体结合态有机碳)含量,增幅介于27.5%~96.3%,导致SOC组分发生累积的大气氮沉降临界负荷为80 kg•hm-2•a-1。SOC含量的变化(ΔSOC)与团聚体结合态有机碳、颗粒态有机碳含量的变化正相关。除好氧细菌丰度外,施氮总体上未改变微生物种群丰度,但是显著改变了微生物的群落结构,革兰氏阳性细菌/革兰氏阴性细菌(G+/G-)丰度比例增加而好氧/厌氧细菌(A/AN)丰度比例下降。有机氮富集倾向于促进温带针阔混交林土壤团聚体的形成,局域产生厌氧微环境,好氧/厌氧细菌(A/AN)丰度比例下降。活性SOC组分含量、土壤团聚体百分比和微生物PLFA丰度之间显著相关,暗示微生物群落结构与SOC积累和稳定之间关系密切。上述研究结果表明,氮素富集会改变温带针阔混交林土壤微生物群落结构,进而导致土壤碳积累。
关键词:  大气氮沉降  SOC物理分组  微生物群落组成  非线性响应  温带针阔混交林
基金项目:国家自然科学基金项目(31770558,41977041,41907036)和中国科学院战略先导专项(XDA2002040203,XDA23060401)
Responses of Soil Organic Carbon Dynamics and Microbial Community Structure to Organic Nitrogen Fertilization in the Temperate Needle-broadleaved Mixed Forest
CAO Zicheng1, CHENG Shulan1, FANG Huajun1, XU Meng2, GENG Jing2, LU Mingzhu2, YANG Yan2, LI Yuna1
1.College of Resources and Environment, University of Chinese Academy of Sciences;2.Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographical Sciences and Natural Resources Research, Chinese Academy of Sciences
Abstract:
【Objective】Carbon (C) and nitrogen (N) cycles in terrestrial ecosystems are closely coupled and reflect the flow of energy and nutrients, respectively. Elevated atmospheric N deposition increases, decreases, or does not affect vegetation and soil C storages across ecosystems and studies. Moreover, the efficiency of C sequestration caused by N amendment varies widely. There is a great uncertainty in the response direction and the magnitude of C sequestration. Soil organic carbon (SOC) transformation and C storage dynamics in forest ecosystems are specific to the increase in atmospheric N deposition, depending on soil initial N status, type, rate, and duration of N fertilization. In the past decades, related research mainly focused on the effect of inorganic N deposition. It is still unclear how organic N deposition affects the SOC and its components in the temperate needle-broadleaved mixed forest. There is few research exploring microbiological mechanism responsible for the change of SOC under N enrichment. The objectives of this research were: (1) to investigate whether multiple levels of N addition significantly changes the C concentrations of bulk soil and different physical fractions, microbial biomass and community structure, as well as general soil properties; (2) to estimate the N critical loads for the alteration of soil C and N concentrations in the temperate needle-broadleaved forest; and (3) to explore the potential linkages between changes in SOC concentration and microbial community abundance. 【Method】In this paper, the in-situ urea fertilization experiment with four levels (0, 40, 80, and 120 kg•hm-2•a-1,N) was set up in the Changbaishan temperate coniferous and broad-leaved mixed forest. After fertilization for three years, soil samples in 0—10 cm mineral layer were collected to determine the soil C and N concentrations, percentage of soil aggregates and SOC content of different particle sizes. The relative abundance and community structure of soil microorganisms were determined using phospholipid fatty acid (PLFA) technique. The relationships between changes in SOC content and changes in microbial community were explored. 【Result】The results showed that three years of N fertilization significantly increased the contents of NO3--N, DON, and TN in soils, and soil acidification was significant. Although N fertilization did not significantly increase SOC content in the surface soil, it significantly increased the contents of labile SOC fractions (particulate organic C and aggregate associated organic C) by 27.5% to 96.3%, resulting in the accumulation of SOC fractions. The critical load of N deposition is estimated as 80 kg•hm-2•a-1. The change in SOC content (ΔSOC) was positively correlated with the change in aggregate associated organic C and particulate organic C. Except for aerobic bacterial abundance, N fertilization did not change the abundance of microbial groups, but significantly changed the structure of microbial community, G+/G- ratio increased while aerobic/anaerobic ratio decreased. There was a significant correlation between labile SOC content, soil aggregates and microbial PLFA abundance, suggesting a close relationship between microbial community structure and SOC accumulation and stability. 【Conclusion】The above results indicate that organic N enrichment tends to promote the formation of soil aggregates in the temperate needle-broadleaved mixed forests, produce anaerobic microenvironment, change microbial community structure, and thereby lead to soil carbon accumulation. Our results suggest that atmospheric N deposition rate below the threshold could lead to a slow accumulation of SOC in the temperate mixed forest over the short term.
Key words:  Atmospheric nitrogen deposition  SOC physical fractionation  Microbial community composition  Nonlinear response  Temperate needle-broadleaved mixed forest