STOTEN | 中国科学院东北地理与农业生态研究所王光华团队:大豆根际碳-磷循环对气候变化的响应

在全球气候变化过程中，大气CO₂浓度和温度不断升高，改变了农业生态系统的生产力。土壤有机质富含大量的有机磷，土壤有机碳的矿化对磷素循环具有重要影响。因此，大气CO₂浓度和温度升高改变光合碳向土壤中的输送，刺激土壤微生物活性，加速土壤有机碳（SOC）的分解，可能释放更多的磷（P）进入土壤土壤溶液。本研究利用¹³C示踪技术模拟气候变化下作物光合碳向地下输送过程，以及其对土壤有机磷矿化的影响。今天，就让我们一起来看一看气候变化是如何影响土壤碳—磷循环的耦合过程吧。

Elevated CO₂ and temperature likely alter photosynthetic carbon inputs to soils, which may stimulate soil microbial activity to accelerate the decomposition of soil organic carbon (SOC), liberating more phosphorus (P) into the soil solution. we hypothesis on the association of SOC decomposition and P transformation in the plant rhizosphere requires robust soil biochemical evidence, which is critical to nutrient management for the mitigation of soil quality against climate change. Thus, we stimulated that photosynthetic carbon flow in the plant–soil continuum was traced with ¹³CO₂ labeling. Interestingly, the elevated CO₂ plus warming treatment increased the primed carbon (C) but decreased the NaHCO₃-extratable organic. Furthermore, elevated CO₂ increased the abundances of C degradation genes, such as abfA and ManB, and P mineralization genes, such as gcd, phoC and phnK. The study indicated that the response of microorganisms to plant-C flow was decisive for coupled C and P cycles, which were likely accelerated under climate change.

在大豆¹³C标记期间，利用NaOH溶液吸收土壤释放出的CO₂，每24 h收集一次，并更换NaOH溶液，连续收集15 d。将收集后的NaOH溶液用来测定土壤¹³CO₂释放量。结果显示，升高CO₂浓度、升高温度以及CO₂浓度和温度同时升高均增加了土壤激发碳，增加幅度分别为24%、22%和43%。

CO₂ trapping was conducted to quantify belowground CO₂ released from soil columns after ¹³CO₂ labeling. The belowground CO₂ was trapped in 60 mL 0.5 M NaOH solution, and traps were collected every 24 h for 15 consecutive days from the beginning of labeling to 7 days after labeling. The results that elevated CO₂, warming and elevated CO₂ plus warming significantly increased CO₂ release compared to the control (Fig. 1). Elevated CO₂ and warming increased the primed C by 24% and 22%, respectively. Furthermore, the primed C was 105.75 mg m^-2 h^-1 and 151.11 mg m^-2 h^-1 under control and eCO₂ plus warming conditions, respectively, representing a significant increase of 43% (Fig. 1).

图1 大气CO₂浓度和温度升高对大豆根际土壤碳激发的影响

误差线代表标准误差（SE，n=3）；相同字母代表处理间在0.05水平上不显著（P < 0.05）

Fig. 1 Effect of eCO₂ and warming on priming effects (Primed soil C) of in rhizosphere of soybean. Error bars represent standard errors of means of three replicates. Values with the same letter are not significantly different (P ≥ 0.05)

气候变化对根际磷组分产生了显著的影响（图2）。对于有机磷库，增温和CO₂浓度和温度同时升高分别导致NaHCO₃-Po减少19%和33%，说明大气CO₂浓度和温度升高对NaHCO₃浸提有机磷库产生了交互作用。然而，与NaHCO₃-Po含量相反，大气CO₂浓度和温度同时升高显著增加NaOH-Po含量25%。对于无机磷库，CO₂浓度升高和温度同时升高使根际NaHCO₃-Pi和HCl-P浓度分别降低了8%和12%。此外，通过相关性分析表明，NaHCO₃-Po与微生物碳（MBC）(R² =0.673，图3C)、土壤碳 (R² =0.578，图3B)和植物碳 (R² =0.310，图3A)呈负相关。而NaOH-Po与MBC呈正相关(R² =0.752，图3D)。

Elevated CO₂ and warming altered P pools in the rhizosphere of soybean (Fig. 2). Regarding the organic P fractions, warming and elevated CO₂ plus warming led to 19 % and 33 % decreases in NaHCO₃-Po, respectively. However, elevated CO₂ plus warming significantly increased the concentrations of NaOH-Po by 25 % (Fig. 2). Regarding inorganic P fractions, elevated CO₂ plus warming decreased the concentrations of NaHCO₃-Pi and HCl-P by 8 % and 12 % in the rhizosphere, respectively. Furthermore, NaHCO₃-Po was negatively correlated with MBC (R² =0.673, Fig. 3C), soil-derived C (R² =0.578, Fig. 3B) and plant-derived C (R² =0.310, Fig. 3A); However, NaOH-Po was positively correlated with MBC (R² =0.752, Fig. 3D).

图2 大气CO₂浓度和温度升高对大豆根际磷组分的影响

Fig. 2 Effect of eCO2 and warming on the P fraction in the rhizosphere of soybean

图3 大气CO₂浓度和温度升高条件下大豆根际NaHCO₃-Po与植物碳（A）、土壤碳（B）、微生物量C（C）以及NaOH-Po与微生物量C（D）的关系

Fig. 3 Effect of eCO₂ and warming on the P fraction in the rhizosphere of soybean

气候变化对大豆根际磷酸酶活性和MBC均产生了显著影响（图4）。与对照相比，大气CO₂浓度升高使酸性磷酸酶活性增加了19%，而且当温度同时升高时，酸性磷酸酶活性增加了50%（图4）。此外，单独CO₂浓度升高对MBC未产生显著影响，但是温度升高以及CO₂浓度和温度同时升高使MBC分别增加46%和88%，说明大气CO₂浓度和温度升高对MBC产生了交互影响。

Elevated CO₂ and warming altered phosphatase activity and microbial biomass C in the rhizosphere of soybean (Fig. 4). Compare with control, elevated CO₂ and elevated CO₂ plus warming significantly increased acid phosphatase activity by 19 % and 50 %, respectively. In addition, elevated CO₂ did not change the microbial biomass C compared to the control, but warming and elevated CO₂ plus warming increased the microbial biomass C by 46 % and 88%, respectively, indicating an interactive effect of elevated CO₂ and temperature (Fig. 4).

图4 大气CO₂浓度和温度升高对大豆根际磷酸酶和土壤微生物量碳的影响

Fig. 4Effect of eCO₂ and warming on acid phosphatase activity and microbial biomass C in the rhizosphere of soybean

大气CO₂浓度和温度升高对大豆根际C、N、P和S功能基因丰度具有不同的影响（图5）。与对照相比，大气CO₂浓度升高增加了C降解基因abfA和ManB拷贝数，但是增温显著降低了abfA和ManB基因拷贝数（图5）。此外，与对照相比，大气CO₂浓度升高显著增加了磷转化gcd、phoC和phnK基因拷贝数。大气CO₂浓度升高对编码N循环的功能基因没有产生显著影响，但是增温以及CO₂浓度和温度同时升高均使ureC、nirS1和gdhA基因丰度显著下降。然而，编码S循环功能基因丰度yedZ和darA在大气CO₂浓度升高条件下显著增加。

Elevated CO₂ and warming altered C, N, P and S the abundances of the function genes in the rhizosphere of soybean (Fig. 5). Compared to the control, elevated CO₂ significantly increased the abundances of the genes encoding arabinofuranosidase (abfA) and mannose- 1-phosphate guanylyl transferase (manB) that were involved in the C degradation. However, warming significantly decreased abundances of abfA and manB genes (Fig. 5). Regarding the P cycle processes, compared to the control, eCO₂ increased abundances of gcd, phoC, and phnK. Elevated CO₂ and warming decreased the abundances of functional genes relevant to N-cycling including ureC, nirS1 and gdhA. Regarding the S cycle, the abundances of yedZ for sulfite oxidase and darA for sulfite reductase alpha subunit significantly increased in response to elevated CO₂ (Fig. 5).

图5 大气CO₂浓度和温度升高对大豆根际C降解功能基因（abfA、lig和ManB），P循环功能基因（gcd、phoD、phoC、pstS、qppC、phnX和phnK），N循功能基因（nosZ1、ureC、narG、nirS1和gdhA）和S循环功能基（yedz和darA）的影响

Fig. 5 The effect of eCO₂ and warming on functional genes abundance of C degradation (abfA, lig and ManB), P cycling (gcd, phoD, phoC, pstS, qppC, phnK and phnX), N cycling (nosZ1, ureC, narG, nirS1 and gdhA) and S cycling (yedz and darA) in the rhizosphere of soybean 

大气CO₂浓度和温度升高促进更多的光合碳向地下部输入，对土壤有机质降解和有机磷矿化产生了正激发效应，表明在气候变化条件下微生物分解有机C和有机P的能力较强。而且，在气候变化条件下，根际碳降解和磷转化相关功能微生物的基因丰度的协同变化进一步证明了这种正激发效应与土壤有机磷矿化相关联。本研究为气候变化条件下CO₂浓度能够通过植物碳流来影响土壤功能微生物，进而促进土壤碳磷循环过程提供了理论支持和数据支撑。

The elevated CO₂ plus warming stimulated more plant-C into the rhizosphere of soybean, resulting in a positive effect on soil organic matter and more P mineralization, implying greater microbial decomposing capacities to decomposition soil C and organic P. Labile P and organic P fractions in the rhizosphere of soybean would be more depleted in future higher CO₂ atmosphere, probably due to a higher the abundance of P functional genes. Furthermore, the synergistic effect of gene abundance of functional microorganisms related to C degradation and P transformation further indicates that the priming effect is associated with soil organic P mineralization under climate change in future. This study provides a theoretical and data support for that future high atmospheric CO₂ concentration may promote soil carbon and phosphorus cycling by altering plant carbon flow and functional microorganisms involved in C decomposition and P transformation.

本文内容来自ELSEVIER旗舰期刊Sci Total Environ第899卷发表的论文：

Guo L.L., Yu Z.H., Li Y.S., Xie Z.H., Wang G.H., Liu J.J., Hu X.J., Wu J.J., Liu X.B., Jin J., 2023. Stimulation of primed carbon under climate change corresponds with phosphorus mineralization in the rhizosphere of soybean. Sci Total Environ, 899, 165580.

https://doi.org/10.1016/j.scitotenv.2023.165580

近期在Sci Total Environ发表的其他论文：

1. Guo LL, et al., 2022. Plant phosphorus acquisition links to phosphorus transformation in the rhizospheres of soybean and rice grown under CO₂ and temperature co-elevated. Science of the Total Environment, 823, 153558.

2. Liu ZX, et al., 2022. Archaeal communities perform an important role in maintaining microbial stability under long term continuous cropping systems. Science of the Total Environment, 2022, 838, 156413.

3. Li S, et al., 2022. Liming mitigates the spread of antibiotic resistance genes in an acid black soil. Science of the Total Environment, 2022, 817, 152971.

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