文章信息
题目：长期保护性耕作改变了土壤固氮菌群落的多样性、组装和网络稳定性/Long-term conservation tillage changes the diversity, assembly and network stability of soil diazotrophic community文章类型：Research Article作者：马玲a,b, 周桂香b, 张佳宝b.*, 贾仲君b,c, 邹洪涛a, 陈林b, 张丛志b, 马东豪b, 韩昌东a,b单位：沈阳农业大学土地与环境学院；中国科学院南京土壤研究所；中国科学院东北地理与农业生态研究所文章链接：https://www.sciencedirect.com/science/article/pii/S100201602300139XDOI: 10.1016/j.pedsph.2023.12.016Citation: Ma L, Zhou G X, Zhang J B, Jia Z J, Zou H T, Chen L, Zhang C Z, Ma D H, Han C D. 2025. Long-term conservation tillage changes the diversity, assembly and network stability of soil diazotrophic community. Pedosphere. 35(2): 299–311. https://doi.org/10.1016/j.pedsph.2023.12.016
图形摘要：
<快速了解本文>
这篇文章在吉林省梨树县进行了长期定位试验，研究了长期保护性耕作对农田土壤中固氮微生物群落的多样性、组装过程以及网络稳定性的影响。研究揭示了保护性耕作对土壤固氮微生物群落的复杂影响，强调了耕作方式和土壤深度在调控微生物群落组装中的重要作用。长期保护性耕作降低了固氮菌群落的多样性，但提高了群落密度，增强了群落的网络稳定性和随机性组装过程的贡献。土壤深度和全氮含量是不同耕作方式下固氮菌群落组装过程的关键预测因子。保护性耕作可能通过改变土壤养分条件和微生物群落结构，促进了更稳定的固氮微生物群落。这些发现为理解保护性农业措施对土壤氮循环过程的影响机制提供了重要见解。
<关键点>
研究方法：测定土壤性质（pH、全氮、有机碳等）、固氮率（15N2法）和固氮菌群落多样性（nifH基因高通量测序）。比较常规耕作和保护性耕作对土壤固氮微生物群落的影响。固氮率与微生物多样性：保护性耕作显著降低了表层土壤（0–10 cm）的固氮率和固氮菌群落的α多样性，但增加了细菌和固氮菌群落的密度。固氮菌群落的结构受耕作方式和土壤深度的显著影响。群落组装过程：常规耕作土壤的固氮菌群落组装主要由确定性过程（68.63%）主导。在保护性耕作下，随机性过程（58.82%）对群落组装的贡献更大。土壤深度和全氮含量是影响群落组装的关键环境因子。土壤深度的影响：随着土壤深度的增加，随机性过程对固氮菌群落组装的影响先增加后减少。在保护性耕作中，随机性过程对固氮菌群落组装的相对贡献随土壤深度的变化更加明显。
<Abstract>
Diazotrophs make important contributions to nitrogen (N) inputs in agricultural ecosystems. However, strong evidence of the effects of conservation tillage (CT) on the coexistence and assembly of soil diazotrophic community and related mechanisms is lacking. Here, a long-term experiment was conducted to study the impacts of CT on the coexistence and assembly patterns of soil diazotrophic community in Lishu County, Jilin Province, North China. Compared to traditional tillage (control, CK), CT significantly reduced both the N fixation rate in top 0–10 cm soil and the alpha diversity of diazotrophic community while increasing the density of diazotrophic and overall bacterial communities. Conservation tillage also reduced the competitive relationships within the diazotrophic community and enhanced network stability. Furthermore, diazotroph assembly was dominated by deterministic processes (relative influence = 68.63%) under CK and stochastic processes (relative influence = 58.82%) under CT. Soil depth and total N (TN) were identified as crucial predictors shaping the assembly processes of diazotrophic community under different tillage practices. The relative influence of stochastic processes on diazotrophic community under CT varied more significantly with increasing soil depth. Overall, tillage practice and soil depth had significant influences on the coexistence and assembly processes of soil diazotrophic community. Moreover, long-term CT may impact the selection of N fixation agents and the specific taxa associated with N fixers. Our results indicated that in CT systems, relatively sufficient nutrient availability led to a reduction in interspecies competition, an increase in network stability, and a greater influence of stochastic processes on community assembly. These findings may help us better understand biological N fixation in sustainable agricultural systems.
Key Words: alpha diversity; biological nitrogen fixation; community assembly; deterministic processes; nitrogen fixation rate; soil diazotroph; stochastic processes
<中文摘要>
固氮菌对农业生态系统中的氮（N）输入具有重要贡献。然而，关于保护性耕作（CT）对土壤固氮菌群落共存和组装的影响及相关机制还缺乏有力的证据。本研究基于吉林省梨树县的长期定位试验，探究了保护性耕作对土壤固氮菌群落共存和组装模式的影响。与常规耕作（对照，CK）相比，CT显著降低了表层0-10 cm土壤的固氮率和固氮菌群落的α多样性，同时增加了固氮菌群落和整体细菌群落的密度。CT还减少了固氮菌群落内部的竞争关系，增强了网络的稳定性。此外，在CK条件下，固氮菌群落组装由确定性过程（相对影响= 68.63%）主导，而在CT条件下由随机性过程（相对影响= 58.82%）主导。土壤深度和全氮（TN）是不同耕作方式下影响固氮菌群落组装过程的关键预测因子。在CT条件下，随机性过程对固氮菌群落组装的相对影响随土壤深度的变化更加明显。总体而言，耕作方式和土壤深度对土壤固氮菌群落的共存和组装过程有显著影响。此外，长期的CT可能会影响固氮者的选择以及与固氮者相关的特定类群。我们的研究结果表明，在CT系统中，相对充足的养分供应会导致种间竞争减少、网络稳定性增加以及随机性过程对群落组装的影响增大。这些发现可能有助于我们更好地理解可持续农业系统中的生物固氮。
关键词：α多样性；生物固氮；群落组装；确定性过程；固氮速率；土壤固氮菌；随机性过程
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图1 常规耕作（对照，CK）和保护性耕作（CT）下土壤固氮率（a）和固氮菌群落的α（香农指数）（b）和β（通过主坐标（PCo）分析可视化的群落结构）（c）多样性和组成（d）随土层深度的变化。通过相似性分析检验了两种耕作方式和不同土壤深度下样本间的差异。图a中的横杠和图b中的竖杠表示平均值的标准偏差（n=3）。星号*和**分别表示P<0.05和P<0.01时的显著差异。Fig. 1. Variations in N fixation rate (a) and alpha (i.e., Shannon index) (b) and beta (i.e., community structure visualized via principal coordinate (PCo) analysis) (c) diversities and composition (d) of soil diazotrophic community with depth under traditional tillage (control, CK) and conservation tillage (CT). Differences among samples under the two tillage practices and different soil depths were examined via analysis of similarities. Horizontal bars in panel a and vertical bars in panel b indicate the standard deviations of the means (n = 3). The asterisks * and ** indicate significant differences at P < 0.05 and P < 0.01, respectively.
图2. 常规耕作（a、c和e）和保护性耕作（b、d和f）条件下土壤固氮菌群落的共现网络。网络根据主要模块（相互高度共现的类群）（a和b）和固氮菌类群（c和d）以及固氮菌操作分类单元（OTUs）的分布情况进行着色。根据模块内连通性（Zi）和模块间连通性（Pi）（e和f）的阈值，将固氮菌操作分类单元（OTU）分为四类。（封面图片）
Fig 2. Co-occurrence networks with nodes of soil diazotrophic community, colored according to the main modules (groups of taxa highly co-occurring with each other) (a and b) and diazotrophic taxa (c and d) and distributions of diazotrophic operational taxonomic units (OTUs) based on their network roles, classified into four categories based on the threshold values of within-module connectivity (Zi) and among-module connectivity (Pi) (e and f) under traditional tillage (a, c, and e) and conservation tillage (b, d, and f).
图3. 常规耕作（对照，CK）和保护性耕作（CT）土壤固氮菌网络中优势菌门的操作分类单元（OTU）比例和关键物种的相对丰度。网络结构稳健性通过移除节点的比例与自然连通性之间的关系来表示。星号***表示P< 0.001 时差异显著。Fig 3. Operational taxonomic unit (OTU) proportions of soil dominant diazotrophic phyla and relative abundances of keystone taxa under traditional tillage (control, CK) and conservation tillage (CT) and network structural robustness shown as the relationship between proportion of removed nodes and natural connectivity. The asterisks *** indicate significant difference at P < 0.001.
图4. 常规耕作（对照，CK）和保护性耕作（CT）下土壤固氮菌群落的β最近分类单元指数（βNTI），以及确定性过程和随机性过程对两种耕作方式下土壤固氮菌群落组装的影响的零模型分析。星号***表示P<0.001时差异显著。水平虚线表示βNTI阈值2和-2。确定性 = 同质选择 + 变量选择；随机性= 同质扩散+扩散限制+未主导过程；差异化=变量选择+扩散限制；同质化=同质选择+同质扩散。Fig 4. Beta nearest taxon index (βNTI) patterns of soil diazotrophic community under traditional tillage (control, CK) and conservation tillage (CT) and null model analysis of the effects of deterministic and stochastic processes on the assemblies of soil diazotrophic community under the two tillage practices. The asterisks *** indicate significant difference at P < 0.001. Horizontal dashed lines indicate the βNTI significance thresholds of 2 and -2. Deterministic = homogeneous selection + variable selection; Stochastic = homogenizing dispersal + dispersal limitation + undominated process; Differentiating = variable selection + dispersal limitation; Homogenizing = homogeneous selection + homogenizing dispersal.
图5. 中性模型对常规耕作（CK）和保护性耕作（CT）土壤固氮菌群落的拟合。蓝色实线表示最佳拟合的中性模型，蓝色虚线描述了模型预测的95%置信区间。R2表示中性模型的拟合优度，m表示估计的迁移率。饼图中显示了中性分布、高于预测和低于预测的固氮菌操作分类单元所占的百分比。Fig 5. Fit of neutral model to soil diazotrophic community under traditional tillage (control, CK) and conservation tillage (CT). The solid blue line indicates the best-fitting neutral model, and the dashed blue lines describe the 95% confidence intervals around the model prediction. R2 denotes the goodness of fit to the neutral model, and m depicts the estimated migration rate. The pie charts show the percentages of diazotrophs among neutrally distributed, overrepresented, and underrepresented operational taxonomic units.
表I 常规耕作（对照，CK）和保护性耕作（CT）下土壤固氮菌群落的β最近分类单元指数与土壤全氮（TN）、深度和环境变量距离（EVD）之间相关性的部分曼特尔检验结果。TABLE I Results of the partial Mantel test for the correlations between beta nearest taxon index of soil diazotrophic community and soil total N (TN), depth, and environmental variable distance (EVD) under traditional tillage (control, CK) and conservation tillage (CT)
图6. 在常规耕作（对照，CK）和保护性耕作（CT）条件下，土壤固氮菌群落的β最近分类单元指数（βNTI）与土壤全氮（TN）和根据欧氏距离计算的土壤全氮的变化之间的关系。星号**和***分别表示 P < 0.01 和 P < 0.001 时的显著差异。水平虚线表示 βNTI 显著性临界值2和-2。Fig 6. Relationships between beta nearest taxon index (βNTI) of soil diazotrophic community and soil total N (TN) and changes of soil TN calculated based on Euclidean distances under traditional tillage (control, CK) and conservation tillage (CT). The asterisks ** and *** indicate significant differences at P < 0.01 and P < 0.001, respectively. Horizontal dashed lines indicate the βNTI significance thresholds of 2 and -2.
图7. 常规耕作（对照组，CK）和保护性耕作（CT）条件下不同深度土壤固氮菌群落的β最近分类单元指数（βNTI），以及在所有样本和CK和/或CT条件下样本中确定性和随机性组装过程的相对影响与土壤深度之间的关系。灰线表示随机性过程随土壤深度变化的趋势。水平虚线表示βNTI阈值2和-2。用不同字母标记的组表示P< 0.05的显著差异。Fig 7. Beta nearest taxon index (βNTI) in soil diazotrophic community in different depths under traditional tillage (control, CK) and conservation tillage (CT) and relationships between the relative influence of deterministic and stochastic assembly processes and soil depth in all samples and samples under CK and/or CT. The gray line represents the trend in the stochastic processes varying with soil depth. Horizontal dashed lines indicate the βNTI significance thresholds of 2 and -2.
