Tripathi Binu M, Piñeiro Juan, Dang Chansotheary, Brzostek Edward, Morrissey Ember M
Division of Plant and Soil Sciences, West Virginia University, Morgantown, West Virginia, USA.
Department of Biology, West Virginia University, Morgantown, West Virginia, USA.
Glob Chang Biol. 2025 Apr;31(4):e70173. doi: 10.1111/gcb.70173.
Labile carbon (C) inputs in soils are expected to increase in the future due to global change drivers such as elevated atmospheric CO concentrations or warming and potential increases in plant primary productivity. However, the role of mycorrhizal association in modulating microbial activity and soil organic matter (SOM) biogeochemistry responses to increasing below-ground C inputs remains unclear. We employed O-HO quantitative stable isotope probing to investigate the effects of synthetic root exudate addition (0, 250, 500, and 1000 μg C g soil) on bacterial growth traits and SOM biogeochemistry in rhizosphere soils of trees associated with arbuscular mycorrhizal (AM) and ectomycorrhizal (ECM) fungi. Soil respiration increased proportionally to the amount of exudate addition in both AM and ECM soils. However, microbial biomass C (MBC) responses differed, increasing in AM and decreasing in ECM soils. In AM soils, exudate addition increased taxon-specific and community-wide relative growth rates of bacteria, leading to enhanced biomass production. Conversely, in ECM soils, relative growth rates were less responsive to exudate addition, and estimates of MBC mortality increased with increasing exudate addition. In the AM soils, aggregated bacterial growth traits were predictive of soil respiration, but this relationship was not observed in ECM soils, perhaps due to substantial MBC mortality. These findings highlight the distinct responses of bacterial communities in AM and ECM rhizosphere soils to exudate addition. Considering that microbial products contribute to the formation of stable soil organic carbon (SOC) pools, future increases in labile exudate release in response to global change may consequently lead to greater SOC gains in AM soils compared to ECM soils.
由于大气CO浓度升高、气候变暖和植物初级生产力潜在增加等全球变化驱动因素，预计未来土壤中不稳定碳（C）输入将增加。然而，菌根共生在调节微生物活性以及土壤有机质（SOM）对地下碳输入增加的生物地球化学响应方面的作用仍不清楚。我们采用O-HO定量稳定同位素示踪技术，研究了添加合成根系分泌物（0、250、500和1000μg C g土壤）对与丛枝菌根（AM）和外生菌根（ECM）真菌相关树木根际土壤中细菌生长特性和SOM生物地球化学的影响。在AM和ECM土壤中，土壤呼吸均与分泌物添加量成比例增加。然而，微生物生物量碳（MBC）的响应有所不同，在AM土壤中增加，而在ECM土壤中减少。在AM土壤中，添加分泌物增加了细菌的分类群特异性和群落水平相对生长速率，从而提高了生物量产量。相反，在ECM土壤中，相对生长速率对分泌物添加的响应较小，并且MBC死亡率估计值随分泌物添加量的增加而增加。在AM土壤中，聚集的细菌生长特性可预测土壤呼吸，但在ECM土壤中未观察到这种关系，这可能是由于大量的MBC死亡所致。这些发现突出了AM和ECM根际土壤中细菌群落对分泌物添加的不同响应。考虑到微生物产物有助于形成稳定的土壤有机碳（SOC）库，未来因全球变化导致的不稳定分泌物释放增加，可能会使AM土壤中的SOC积累量比ECM土壤更多。
