Effects of <i>Phyllostachys edulis</i> expansion on soil microbial residue carbon accumulation in evergreen broad-leaved forests

SHAO Shuai; WANG Zhongqian; PAN Lingqiang; ZHENG Yunyou; ZHENG Xuli; TIAN Libin; XU Qiufang

doi:10.11833/j.issn.2095-0756.20230626

Volume 41 Issue 5

Sep. 2024

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SHAO Shuai, WANG Zhongqian, PAN Lingqiang, et al. Effects of Phyllostachys edulis expansion on soil microbial residue carbon accumulation in evergreen broad-leaved forests[J]. Journal of Zhejiang A&F University, 2024, 41(5): 1005-1012. DOI: 10.11833/j.issn.2095-0756.20230626

Citation:

SHAO Shuai, WANG Zhongqian, PAN Lingqiang, et al. Effects of Phyllostachys edulis expansion on soil microbial residue carbon accumulation in evergreen broad-leaved forests[J]. Journal of Zhejiang A&F University, 2024, 41(5): 1005-1012. DOI: 10.11833/j.issn.2095-0756.20230626

Effects of Phyllostachys edulis expansion on soil microbial residue carbon accumulation in evergreen broad-leaved forests

DOI: 10.11833/j.issn.2095-0756.20230626

1.
College of Environment and Resources/College of Carbon Neutrality, Zhejiang A&F University, Hangzhou 311300, Zhejiang, China
2.
Lingfengsi Forest Farm of Anji County, Anji 313300, Zhejiang, China
3.
College of Forestry, Beijing Forestry University, Beijing 100083, China

Received Date: 2023-12-28
Accepted Date: 2024-05-25
Rev Recd Date: 2024-05-20

Available Online: 2024-09-25

Publish Date: 2024-09-25

Abstract

Objective This study is to reveal the dynamic changes of soil organic carbon (SOC) in evergreen broad-leaved forests during the expansion of Phyllostachys edulis in subtropical regions by affecting the accumulation of soil microbial residue carbon. Method Taking amino sugar as the research object, this study investigated the accumulative effect of microbial residue carbon in surface soil (0−10 cm) of evergreen broad-leaved forest, Ph. edulis and broad-leaved mixed forest, and pure Ph. edulis forest in the state-owned forest farm of Lingfengsi in Anji, Zhejiang Province, as well as the correlation characteristics with organic carbon. Result During the expansion of Ph. edulis, soil fungal residue carbon, bacterial residue carbon and microbial residue carbon all significantly (P＜0.05) decreased (36.76%, 35.13% and 40.32%, respectively), and the annual litter production indirectly affected SOC, fungi biomass, soil bacteria biomass and total microbial biomass, thereby affecting the cumulative effects of soil fungal residue carbon, bacterial residue carbon and total microbial residue carbon, respectively. There was no significant change in the ratio of fungal residue carbon, bacterial residue carbon and total microbial carbon residue to SOC in the early stage of Ph. edulis expansion (from evergreen broad-leaved forest to Ph. edulis and broad-leaved mixed forest), but in the late stage of expansion (from Ph. edulis and broad-leaved mixed forest to Ph. edulis forest), the ratio increased significantly. Conclusion The role of microbial carbon on SOC gradually increases during the expansion of Ph. edulis into evergreen broad-leaved forests. [Ch, 4 fig. 1 tab. 26 ref.]
- Phyllostachys edulis expansion,
- soil organic carbon,
- microbial residue carbon,
- amino sugar

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References

[1]	JIN Wenhao, SHAO Shuai, CHEN Junhui, et al. Research progress in the impact of different mycorrhizal types on soil carbon cycling [J]. Journal of Zhejiang A&F University, 2021, 38(5): 953 − 962.
[2]	KALLENBACH C M, FREY S D, GRANDY A S. Direct evidence for microbial-derived soil organic matter formation and its ecophysiological controls [J/OL]. Nature Communications, 2016, 7: 13630[2023-11-28]. doi: 10.1038/ncomms13630.
[3]	LIANG Chao, SCHIMEL J P, JASTROW J D. The importance of anabolism in microbial control over soil carbon storage [J/OL]. Nature Microbiology, 2017, 2: 17105[2023-11-28]. doi: 10.1038/nmicrobiol.2017.105.
[4]	LIANG Chao, AMELUNG W, LEHMANN J, et al. Quantitative assessment of microbial necromass contribution to soil organic matter [J]. Global Change Biology, 2019, 25(11): 3578 − 3590.
[5]	JOERGENSEN R G. Amino sugars as specific indices for fungal and bacterial residues in soil [J]. Biology and Fertility of Soils, 2018, 54(5): 559 − 568.
[6]	LIANG Chao, KÄSTNER M, JOERGENSEN R G. Microbial necromass on the rise: the growing focus on its role in soil organic matter development [J/OL]. Soil Biology and Biochemistry, 2020, 150: 108000[2023-11-28]. doi: 10.1016/j.soilbio.2020.108000.
[7]	WANG Chao, WANG Xu, PEI Guangting, et al. Stabilization of microbial residues in soil organic matter after two years of decomposition [J/OL]. Soil Biology and Biochemistry, 2020, 141: 107687[2023-11-28]. doi: 10.1016/j.soilbio.2019.107687.
[8]	ZHU Xuefeng, JACKSON R D, DELUCIA E H, et al. The soil microbial carbon pump: from conceptual insights to empirical assessments [J]. Global Change Biology, 2020, 26(11): 6032 − 6039.
[9]	WANG Baorong, AN Shaoshan, LIANG Chao, et al. Microbial necromass as the source of soil organic carbon in global ecosystems [J/OL]. Soil Biology and Biochemistry, 2021, 162: 108422[2023-11-28]. doi: 10.1016/j.soilbio.2021.108422.
[10]	XU Qiufang, LIANG Chenfei, CHEN Junhui, et al. Rapid bamboo invasion (expansion) and its effects on biodiversity and soil processes [J/OL]. Global Ecology and Conservation, 2020, 21: e00787[2023-11-28]. doi: 10.1016/j.gecco.2019.e00787.
[11]	LI Yumin, FENG Pengfei. Bamboo resources in China based on the ninth national forest inventory data [J]. World Bamboo and Rattan, 2019, 17(6): 45 − 48.
[12]	YANG Qingpei, YANG Guangyao, SONG Qingni, et al. Ecological studies on bamboo expansion: process, consequence and mechanism [J]. Chinese Journal of Plant Ecology, 2015, 39(1): 110 − 124.
[13]	ZHAO Yingzhi, LIANG Chao, SHAO Shuai, et al. Linkages of litter and soil C∶N∶P stoichiometry with soil microbial resource limitation and community structure in a subtropical broadleaf forest invaded by moso bamboo [J]. Plant and Soil, 2021, 465(1): 473 − 490.
[14]	SONG Qingni, OUYANG Ming, YANG Qingpei, et al. Degradation of litter quality and decline of soil nitrogen mineralization after moso bamboo (Phyllostachys pubscens) expansion to neighboring broadleaved forest in subtropical China [J]. Plant and Soil, 2016, 404: 113 − 124.
[15]	LIN Ziwen, LI Yongfu, TANG Caixian, et al. Converting natural evergreen broadleaf forests to intensively managed moso bamboo plantations affects the pool size and stability of soil organic carbon and enzyme activities [J]. Biology and Fertility of Soils, 2018, 54(4): 467 − 480.
[16]	LIU Xishuai, SIEMANN E, CUI Cheng, et al. Moso bamboo (Phyllostachys edulis) invasion effects on litter, soil and microbial PLFA characteristics depend on sites and invaded forests [J]. Plant and Soil, 2019, 438: 85 − 99.
[17]	LU Rukun. The Analysis Method of Soil Agricultural Chemistry [M]. 3rd ed. Beijing: China Agricultural Science and Technology Press, 2020.
[18]	ZHANG Xudong, AMELUNG W. Gas chromatographic determination of muramic acid, glucosamine, mannosamine, and galactosamine in soils [J]. Soil Biology and Biochemistry, 1996, 28(9): 1201 − 1206.
[19]	LIANG Chao, ZHU Xuefeng. The soil microbial carbon pump as a new concept for terrestrial carbon sequestration [J]. Scientia Sinica Terrae, 2021, 51(4): 545 − 558.
[20]	SHAO Shuai, ZHAO Yu, ZHANG Wei, et al. Linkage of microbial residue dynamics with soil organic carbon accumulation during subtropical forest succession [J]. Soil Biology and Biochemistry, 2017, 114: 114 − 120.
[21]	SHAO Pengshuai, LIANG Chao, LYNCH L, et al. Reforestation accelerates soil organic carbon accumulation: evidence from microbial biomarkers [J]. Soil Biology and Biochemistry, 2019, 131: 182 − 190.
[22]	ZHENG Tiantian, XIE Hongtu, THOMPSON G L, et al. Shifts in microbial metabolic pathway for soil carbon accumulation along subtropical forest succession [J/OL]. Soil Biology and Biochemistry, 2021, 160: 108335[2023-11-28]. doi: 10.1016/j.soilbio.2021.108335.
[23]	COTRUFO M F, RANALLI M G, HADDIX M L, et al. Soil carbon storage informed by particulate and mineral-associated organic matter [J]. Nature Geoscience, 2019, 12: 989 − 994.
[24]	THEVENOT M, DIGNAC M F, RUMPEL C. Fate of lignins in soils: a review [J]. Soil Biology and Biochemistry, 2010, 42(8): 1200 − 1211.
[25]	SHAO Shuai, HE Hongbo, LIANG Chenfei, et al. Moso bamboo expansion into a broadleaved forest alters the dominant soil organic carbon source [J/OL]. European Journal of Soil Science, 2023, 74(3): e13366[2023-11-28]. doi: 10.1111/ejss.13366.
[26]	ANGST G, MUELLER K E, NIEROP K G J, et al. Plant- or microbial-derived? A review on the molecular composition of stabilized soil organic matter [J/OL]. Soil Biology and Biochemistry, 2021, 156: 108189[2023-11-28]. doi: 10.1016/j.soilbio.2021.108189.

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土壤微生物在有机碳形成与转化过程中起到了关键作用^[1]。土壤微生物“碳泵”理论的续埋效应观点认为：微生物残体碳(MRC)累积效应对土壤有机碳(SOC)转化起着重要作用^[2−3]。在量化微生物残体碳对全球陆地生态系统表层土壤有机碳的贡献后，发现微生物残体碳对土壤有机碳的贡献可达50%以上^[4]。这是由于土壤中海量微生物在不断生长、代谢、增殖和死亡等迭代过程中，微生物细胞壁残体组分(如真菌细胞壁组分几丁质和细菌细胞壁组分肽聚糖等)在土壤中会不断累积，而且，土壤中大部分微生物附着于土壤矿物表面生长和繁殖，微生物死亡后形成的残体碳也多与土壤矿物表面相结合形成有机无机复合体，能够相对稳定地存留在土壤中，直接贡献于土壤碳库^[5]。因此，微生物残体碳的形成和转化对于维持土壤碳汇功能、缓解气候变化有重要意义^[6]。然而，土壤微生物残体碳结构复杂、组分多样，目前无法准确被量化，只能通过解析微生物残体的生物标志物——氨基糖，来表征其形成和转化过程^[7]。目前，土壤中有4种氨基糖可以被定量化，分别是氨基葡萄糖(GluN)、胞壁酸(MurN)、氨基半乳糖(GalN)和氨基甘露糖(ManN)，其中GluN主要来源于真菌细胞壁，MurN唯一来源于细菌；GalN一般认为其主要是由细菌合成，但目前尚不确定其准确来源，ManN在土壤中很少，可忽略不计^[8]。因此，探究不同微生物来源微生物残体碳与土壤有机碳的关系，有助于揭示土壤有机碳形成和转化过程中真菌和细菌的作用^[9]。

毛竹Phyllostachys edulis是中国亚热带地区数量最多、分布面积最大、最具代表性的竹种^[10]，面积达4.68×10⁶ hm^2[11−12]。毛竹借助其强大的地下竹鞭向周围扩张，逐渐改变原有林分植物群落组成并使其结构简化。毛竹向常绿阔叶林扩张会使得生境内凋落叶输入量有所减少^[13−14]，土壤有机碳储量下降且结构也发生改变^[15]，土壤微生物生物量下降而细菌多样性和丰富度却显著增加，细菌和真菌的生物量比例升高^[16]。然而，毛竹扩张对常绿阔叶林土壤微生物残体的累积特征及其影响因素仍不清楚。因此，本研究以毛竹向亚热带常绿阔叶林扩张演替序列为研究对象，通过分析土壤氨基糖质量分数，揭示毛竹扩张对常绿阔叶林土壤微生物残体碳累积的影响及与有机碳关联特征，并进一步分析毛竹扩张过程中土壤微生物残体碳变化的影响因子，以期提升对亚热带森林土壤有机碳转化的微生物调控机制的认知。

1. 研究区与研究方法

1.1. 研究区概况

研究区位于浙江省湖州市安吉县灵峰寺国有林场(30°60′N，119°63′E)。该地属亚热带季风气候，气候温和，光照充足，雨量充沛，四季分明，年平均气温为16.1℃，最冷月平均气温为0.0 ℃，极端最低气温为−18.0 ℃，极端最高气温为41.0 ℃，年日照时数为1 771.7 h，年平均降水为1 423.4 mm，集中在3—8月。地形主要是低山丘陵，海拔为75~250 m。研究区土壤母岩为粉砂岩，母质为坡积物，土壤类型为红壤，按照土壤系统分类可划定为湿润淋溶土。研究区在20世纪80年代前主要为常绿阔叶林，乔木主要有青冈Cyclobalanopsis glauca、木荷Schima superba、苦槠Castanopsis sclerophylla、栲树C. fargesii、麻栎Quercus acutissima和枫香Liquidambar formosana等。林下灌木、杂草丛生，林分郁闭度高。20世纪80年代，人工种植毛竹林。毛竹竹鞭较强的扩张能力，使得毛竹不断向周围常绿阔叶林扩张，并逐步替代常绿阔叶林，在毛竹扩张带上形成了3种不同类型的森林，分别是常绿阔叶林(以青冈为主)、毛竹-阔叶混交林和毛竹纯林。

1.2. 土壤样品采集与处理

2018年5月，在研究区内选择总面积近60 hm²的毛竹向常绿阔叶林扩张演替序列样带，包含常绿阔叶林(BL)、毛竹-阔叶混交林(Mix)、毛竹纯林(BB)。常绿阔叶林乔木以青冈为主；毛竹-阔叶混交林中以青冈为主的阔叶树和毛竹数量比大致为1∶1。3种林分中的灌木及草本类型接近，以山胡椒Lindera glauca、六月雪Serissa japonica、中日金星蕨Parathelypteris nipponica、大油芒Spodiopogon sibiricus等为主。在3种林分内选择地形相对平坦区域，分别划出3个面积为20 m×20 m的样方作为重复，样方之间的直线距离为50 m。在每个样方内随机选取5个采样点，采集凋落物和表层土壤样品，采样深度均为0~10 cm (A层土壤)。将每个采样点的凋落物和土壤样品分别充分混匀为1个样品带回实验室。将凋落物样品风干后，研磨过1 mm筛，测定凋落物有机碳和全氮质量分数；将土壤样品过2 mm筛，风干后测定氨基糖及基础理化性质。年凋落物输入量采用尼龙网(1 mm网格，1 m×1 m)收集，从2018年5月至2019年5月隔3个月收集1次，最后将全年收集的凋落物相加得到年凋落物输入量。

1.3. 分析方法

凋落物和土壤样品的有机碳和全氮质量分数利用元素分析仪(Flash 2000)干烧法测定；土壤含水量采用105 ℃烘干法测定；土壤全磷(TP)采用浓硫酸和高氯酸消解，钼黄比色法测定；土壤微生物生物量碳(MBC)和微生物生物量氮(MBN)均采用氯仿熏蒸硫酸钾浸提-TOC分析仪测定^[17]。

土壤氨基糖利用气相色谱法测定^[18]。实验步骤如下：称取一定量土样(根据样品含氮量)，用6 mol·L⁻¹盐酸水解，加入内标1(肌醇)溶液过滤，滤液干燥后将其溶解，把pH调到6.6~6.8后离心10 min，再次进行干燥处理。干燥物经过无水甲醇溶解离心后，把上清液转移到衍生瓶内进行氮吹干燥，氮吹后的干燥物加入内标2溶液置于−40 ℃冰箱彻底冷冻后，在冷冻干燥仪内冷冻干燥。干燥后的样品均加入衍生试剂去除无机相，余下的有机相进行氮吹，加入乙酸乙酯∶正己烷为1∶1(质量比)的混合溶剂溶解，瓶内溶液转移到色谱瓶内进行色谱分析测定。利用内标法定量各氨基单糖质量分数。

利用土壤各氨基单糖质量分数估算土壤真菌残体碳(C_MRCF)、土壤细菌残体碳(C_MRCB)及土壤总微生物残体碳(C_MRC)的质量分数^[4]。计算公式如下：

其中：C_MurN为胞壁酸质量分数(μg·g⁻¹)，C_GluN为氨基葡萄糖质量分数(μg·g⁻¹)。胞壁酸和细菌残体碳的转换系数为45，氨基葡萄糖和真菌残体碳的转换系数为9，GluN的分子质量为179.17，MurN的分子质量为251.23，细菌细胞壁中胞壁酸与氨基葡萄糖的摩尔比例约为1∶2。

1.4. 数据处理与统计分析

采用SPSS 17.0对数据进行统计分析。采用单因素方差分析法(one-way ANOVA)和Duncan法对土壤微生物残体碳数量、真细菌残体碳比值与微生物残体碳占土壤有机碳的比值进行方差分析(P＜0.05)，并通过结构方程初步分析毛竹扩张过程中土壤微生物残体碳与凋落物年产量、凋落物碳氮比、土壤碳氮比、总磷脂肪酸的直接和间接相关性。利用Origin 8.0绘图。图表中数据均为平均值±标准误。

3. 讨论

3.1. 毛竹扩张对常绿阔叶林土壤微生物残体碳累积的影响

在本研究中，毛竹向常绿阔叶林扩张后表层土壤真菌残体碳、细菌残体碳和总微生物残体碳均显著下降，说明毛竹扩张显著降低了常绿阔叶林土壤微生物残体碳的累积效应。Spearman相关分析表明：毛竹扩张过程中土壤真菌残体碳、细菌残体碳和总微生物残体碳质量分数变化与凋落物碳质量分数、真菌群落生物量、细菌群落生物量和总微生物群落生物量的下降密切相关^[19−20]。结构方程模拟结果发现：毛竹扩张过程中凋落物年产量能够通过间接影响土壤有机碳和土壤真菌生物量、细菌生物量和总微生物生物量，进而分别影响土壤真菌残体碳、细菌残体碳和总微生物残体碳的累积效应，说明在水热条件适宜的条件下，相较于凋落物质量(凋落物碳氮比)，凋落物输入量是影响微生物残体碳的关键因素^[13]。毛竹向常绿阔叶林扩张显著降低了凋落物年产量，使得微生物可利用底物输入减少。同时，常绿阔叶林土壤有机碳显著高于毛竹林土壤，说明阔叶林土壤碳源丰富，有利于微生物生存。毛竹扩张过程中凋落物年产量和土壤有机碳均逐渐下降，使得土壤真菌、细菌和总微生物生物量逐渐下降，而土壤真菌、细菌和总微生物生物量分别与土壤真菌残体碳、细菌残体碳和总微生物残体碳具有正相关关系，说明毛竹向常绿阔叶林扩张过程中，凋落物数量下降和不同林分间土壤有机碳水平的差异引起的微生物生物量减少是土壤真菌残体碳、细菌残体碳和总微生物残体累积效应下降的主要原因^[21]。不过，本研究发现凋落物碳氮比与土壤真菌生物量和总微生物生物量存在显著负相关，意味着毛竹扩张过程中凋落物质量的提升并没有提高真菌和总微生物生物量，原因可能是毛竹向阔叶林扩张导致土壤中微生物可利用底物显著下降，较少的高质量毛竹凋落物输入(碳氮比较低)无法满足微生物需求，使得微生物增殖和周转过程受到抑制，从而降低了微生物残体碳的累积^[22]。说明毛竹扩张改变了常绿阔叶林生境条件，不利于微生物源有机碳累积。

3.2. 毛竹扩张对微生物残体碳占土壤有机碳比例的影响

毛竹向常绿阔叶林扩张过程中，土壤真菌残体碳、细菌残体碳和总微生物残体碳在土壤中的占比均呈现先下降后上升的趋势，说明毛竹扩张前期(常绿阔叶林演替为毛竹-阔叶混交林)土壤微生物体内周转作用对有机碳累积贡献有下降趋势，而毛竹扩张后期(毛竹-阔叶混交林演替为毛竹纯林)土壤微生物体内周转作用对有机碳累积的贡献显著增加^[23]。土壤微生物体内周转和植物难降解组分残留是有机碳形成的2条主要途径^[24]。常绿阔叶林凋落物输入量大，且凋落物中含有大量微生物可利用的活性底物，微生物会优先利用活性底物，将难分解的植物残体保留下来，并贡献于有机碳的累积和储存^[13]，因此，常绿阔叶林土壤中微生物对土壤有机碳的贡献较低；毛竹扩张形成毛竹-阔叶混交林后，虽然凋落物的输入量减少，不利于微生物增殖，但是生境植被多样性增加及生境凋落物质量的提升(毛竹凋落叶碳氮比低于常绿阔叶林凋落叶)却有利于微生物周转。虽然微生物残体碳与土壤有机碳协同下降，但是微生物残体碳对有机碳的贡献与常绿阔叶林相比并没有显著差异；而当毛竹-阔叶混交林逐渐演替为毛竹纯林后，凋落物数量显著下降，降低土壤中活性底物数量(活性有机碳质量分数下降)，这可能会促进残留在土壤中的难分解植物组分也被微生物作为碳源利用^[25]，导致凋落物中难分解组分在土壤中的累积逐渐减少，土壤有机碳质量分数显著降低。已有研究发现：毛竹扩张降低了常绿阔叶林土壤中木质素质量分数，而微生物残体碳主要以矿物结合态的形式相对稳定地存留在土壤中^[26]，因此，毛竹扩张提升了微生物残体碳对土壤有机碳的贡献。

4. 结论

毛竹扩张降低了常绿阔叶林土壤真菌残体碳、细菌残体碳和总微生物残体碳的累积，而微生物对土壤有机碳的贡献却呈现先下降后上升的趋势，这可能与凋落物数量下降和质量提升有关。而且，毛竹向常绿阔叶林扩张在改变土壤有机碳来源和组分的同时，提高了有机碳的可利用性，有利于提高毛竹林土壤有机碳抵抗环境条件变化的能力。研究结果对通过合理的营林措施提升土壤有机碳储量，发挥森林土壤碳汇功能具有重要意义。

Reference (26)

[1]	金文豪, 邵帅, 陈俊辉, 等. 不同类型菌根对土壤碳循环的影响差异研究进展[J]. 浙江农林大学学报, 2021, 38(5): 953 − 962.	JIN Wenhao, SHAO Shuai, CHEN Junhui, et al. Research progress in the impact of different mycorrhizal types on soil carbon cycling [J]. Journal of Zhejiang A&F University, 2021, 38(5): 953 − 962.
[2]	KALLENBACH C M, FREY S D, GRANDY A S. Direct evidence for microbial-derived soil organic matter formation and its ecophysiological controls [J/OL]. Nature Communications, 2016, 7: 13630[2023-11-28]. doi: 10.1038/ncomms13630.
[3]	LIANG Chao, SCHIMEL J P, JASTROW J D. The importance of anabolism in microbial control over soil carbon storage [J/OL]. Nature Microbiology, 2017, 2: 17105[2023-11-28]. doi: 10.1038/nmicrobiol.2017.105.
[4]	LIANG Chao, AMELUNG W, LEHMANN J, et al. Quantitative assessment of microbial necromass contribution to soil organic matter [J]. Global Change Biology, 2019, 25(11): 3578 − 3590.
[5]	JOERGENSEN R G. Amino sugars as specific indices for fungal and bacterial residues in soil [J]. Biology and Fertility of Soils, 2018, 54(5): 559 − 568.
[6]	LIANG Chao, KÄSTNER M, JOERGENSEN R G. Microbial necromass on the rise: the growing focus on its role in soil organic matter development [J/OL]. Soil Biology and Biochemistry, 2020, 150: 108000[2023-11-28]. doi: 10.1016/j.soilbio.2020.108000.
[7]	WANG Chao, WANG Xu, PEI Guangting, et al. Stabilization of microbial residues in soil organic matter after two years of decomposition [J/OL]. Soil Biology and Biochemistry, 2020, 141: 107687[2023-11-28]. doi: 10.1016/j.soilbio.2019.107687.
[8]	ZHU Xuefeng, JACKSON R D, DELUCIA E H, et al. The soil microbial carbon pump: from conceptual insights to empirical assessments [J]. Global Change Biology, 2020, 26(11): 6032 − 6039.
[9]	WANG Baorong, AN Shaoshan, LIANG Chao, et al. Microbial necromass as the source of soil organic carbon in global ecosystems [J/OL]. Soil Biology and Biochemistry, 2021, 162: 108422[2023-11-28]. doi: 10.1016/j.soilbio.2021.108422.
[10]	XU Qiufang, LIANG Chenfei, CHEN Junhui, et al. Rapid bamboo invasion (expansion) and its effects on biodiversity and soil processes [J/OL]. Global Ecology and Conservation, 2020, 21: e00787[2023-11-28]. doi: 10.1016/j.gecco.2019.e00787.
[11]	李玉敏, 冯鹏飞. 基于第9次全国森林资源清查的中国竹资源分析[J]. 世界竹藤通讯, 2019, 17(6): 45 − 48.	LI Yumin, FENG Pengfei. Bamboo resources in China based on the ninth national forest inventory data [J]. World Bamboo and Rattan, 2019, 17(6): 45 − 48.
[12]	杨清培, 杨光耀, 宋庆妮, 等. 竹子扩张生态学研究: 过程、后效与机制[J]. 植物生态学报, 2015, 39(1): 110 − 124.	YANG Qingpei, YANG Guangyao, SONG Qingni, et al. Ecological studies on bamboo expansion: process, consequence and mechanism [J]. Chinese Journal of Plant Ecology, 2015, 39(1): 110 − 124.
[13]	ZHAO Yingzhi, LIANG Chao, SHAO Shuai, et al. Linkages of litter and soil C∶N∶P stoichiometry with soil microbial resource limitation and community structure in a subtropical broadleaf forest invaded by moso bamboo [J]. Plant and Soil, 2021, 465(1): 473 − 490.
[14]	SONG Qingni, OUYANG Ming, YANG Qingpei, et al. Degradation of litter quality and decline of soil nitrogen mineralization after moso bamboo (Phyllostachys pubscens) expansion to neighboring broadleaved forest in subtropical China [J]. Plant and Soil, 2016, 404: 113 − 124.
[15]	LIN Ziwen, LI Yongfu, TANG Caixian, et al. Converting natural evergreen broadleaf forests to intensively managed moso bamboo plantations affects the pool size and stability of soil organic carbon and enzyme activities [J]. Biology and Fertility of Soils, 2018, 54(4): 467 − 480.
[16]	LIU Xishuai, SIEMANN E, CUI Cheng, et al. Moso bamboo (Phyllostachys edulis) invasion effects on litter, soil and microbial PLFA characteristics depend on sites and invaded forests [J]. Plant and Soil, 2019, 438: 85 − 99.
[17]	鲁如坤. 土壤农业化学分析方法[M]. 3版. 北京: 中国农业科技出版社, 2020.	LU Rukun. The Analysis Method of Soil Agricultural Chemistry [M]. 3rd ed. Beijing: China Agricultural Science and Technology Press, 2020.
[18]	ZHANG Xudong, AMELUNG W. Gas chromatographic determination of muramic acid, glucosamine, mannosamine, and galactosamine in soils [J]. Soil Biology and Biochemistry, 1996, 28(9): 1201 − 1206.
[19]	梁超, 朱雪峰. 土壤微生物碳泵储碳机制概论[J]. 中国科学: 地球科学, 2021, 51(4): 545 − 558.	LIANG Chao, ZHU Xuefeng. The soil microbial carbon pump as a new concept for terrestrial carbon sequestration [J]. Scientia Sinica Terrae, 2021, 51(4): 545 − 558.
[20]	SHAO Shuai, ZHAO Yu, ZHANG Wei, et al. Linkage of microbial residue dynamics with soil organic carbon accumulation during subtropical forest succession [J]. Soil Biology and Biochemistry, 2017, 114: 114 − 120.
[21]	SHAO Pengshuai, LIANG Chao, LYNCH L, et al. Reforestation accelerates soil organic carbon accumulation: evidence from microbial biomarkers [J]. Soil Biology and Biochemistry, 2019, 131: 182 − 190.
[22]	ZHENG Tiantian, XIE Hongtu, THOMPSON G L, et al. Shifts in microbial metabolic pathway for soil carbon accumulation along subtropical forest succession [J/OL]. Soil Biology and Biochemistry, 2021, 160: 108335[2023-11-28]. doi: 10.1016/j.soilbio.2021.108335.
[23]	COTRUFO M F, RANALLI M G, HADDIX M L, et al. Soil carbon storage informed by particulate and mineral-associated organic matter [J]. Nature Geoscience, 2019, 12: 989 − 994.
[24]	THEVENOT M, DIGNAC M F, RUMPEL C. Fate of lignins in soils: a review [J]. Soil Biology and Biochemistry, 2010, 42(8): 1200 − 1211.
[25]	SHAO Shuai, HE Hongbo, LIANG Chenfei, et al. Moso bamboo expansion into a broadleaved forest alters the dominant soil organic carbon source [J/OL]. European Journal of Soil Science, 2023, 74(3): e13366[2023-11-28]. doi: 10.1111/ejss.13366.
[26]	ANGST G, MUELLER K E, NIEROP K G J, et al. Plant- or microbial-derived? A review on the molecular composition of stabilized soil organic matter [J/OL]. Soil Biology and Biochemistry, 2021, 156: 108189[2023-11-28]. doi: 10.1016/j.soilbio.2021.108189.

林分类型	凋落物				土壤
林分类型	凋落物年产量/ (Mg·hm⁻²·a⁻¹)	凋落物有机碳/ (g·kg⁻¹)	凋落物全氮/ (g·kg⁻¹)	凋落物碳氮比	土壤含水量/%	土壤有机碳/ (g·kg⁻¹)	土壤全氮/ (g·kg⁻¹)	土壤碳氮比
常绿阔叶林	11.11±1.63 a	461.98±30.35 a	12.84±0.40 a	35.98±2.05 a	0.32±0.06 a	35.24±6.33 a	2.57±0.6 ab	13.85±1.31 a
毛竹-阔叶混交林	10.30±1.13 a	420.72±19.81 b	12.45±1.82 a	34.35±5.90 a	0.28±0.07 a	28.02±0.80 b	2.26±0.2 a	12.48±1.74 a
毛竹纯林	5.71±0.37 b	301.56±49.24 c	14.49±1.62 a	20.74±1.07 b	0.37±0.05 a	19.70±5.44 c	1.63±0.4 b	12.06±0.39 a

林分类型	土壤
林分类型	土壤全磷/ (g·kg⁻¹)	可溶性有机碳/ (mg·kg⁻¹)	pH	磷脂脂肪酸/ (nmol·g⁻¹)	真菌脂肪酸/ (nmol·g⁻¹)	细菌脂肪酸/ (nmol·g⁻¹)	真菌脂肪酸/ 细菌脂肪酸
常绿阔叶林	0.44±0.04 a	892.94±96.97 a	3.82±0.21 a	9.31±1.06 a	1.34±0.24 a	5.97±0.56 a	0.22±0.02 a
毛竹-阔叶混交林	0.44±0.03 a	746.87±108.16 b	3.92±0.28 a	7.13±1.41 b	0.88±0.27 b	4.79±0.71 b	0.18±0.03 ab
毛竹纯林	0.33±0.04 b	672.67±86.62 b	4.09±0.14 a	5.64±0.40 b	0.66±0.04 b	3.84±0.19 b	0.17±0.01 b
说明：不同小写字母表示不同林分类型间差异显著(P＜0.05)。