Raczka Nanette C, Carrara Joseph E, Brzostek Edward R
Department of Biology, West Virginia University, Morgantown, West Virginia, USA.
Glob Chang Biol. 2022 Oct;28(19):5820-5830. doi: 10.1111/gcb.16340. Epub 2022 Jul 29.
Given that global change is predicted to increase the frequency and severity of drought in temperate forests, it is critical to understand the degree to which plant belowground responses cascade through the soil system to drive ecosystem responses to water stress. While most research has focused on plant and microbial responses independently of each other, a gap in our understanding lies in the integrated response of plant-microbial interactions to water stress. We investigated the extent to which divergent belowground responses to reduced precipitation between sugar maple trees (Acer saccharum) versus oak trees (Oak spp.) may influence microbial activity via throughfall exclusion in the field. Evidence that oak trees send carbon belowground to prime microbial activity more than maples under ambient conditions and in response to water stress suggests there is the potential for corresponding impacts of reduced precipitation on microbial activity. As such, we tested the hypothesis that differences in belowground C allocation between oaks and maples would stimulate microbial activity in the oak treatment soils and reduce microbial activity in in the sugar maple treatment soils compared to their respective controls. We found that the treatment led to declines in N mineralization, soil respiration, and oxidative enzyme activity in the sugar maple treatment plot. These declines may be due to sugar maple trees reducing root C transfers to the soil. By contrast, the reduced precipitation treatment enhanced soil respiration, as well as rates of N mineralization and peroxidase activity in the oak rhizosphere. This enhanced activity suggests that oak roots provided optimal rhizosphere conditions during water stress to prime microbial activity to support net primary production. With future changes in precipitation predicted for forests in the Eastern US, we show that the strength of plant-microbial interactions drives the degree to which reduced precipitation impacts soil C and nutrient cycling.
鉴于全球变化预计会增加温带森林干旱的频率和严重程度，了解植物地下响应通过土壤系统级联影响生态系统对水分胁迫响应的程度至关重要。虽然大多数研究分别聚焦于植物和微生物的响应，但我们在理解植物 - 微生物相互作用对水分胁迫的综合响应方面存在差距。我们通过野外降雨截留实验，研究了糖枫（Acer saccharum）与橡树（Oak spp.）对降水减少的不同地下响应在多大程度上可能影响微生物活性。有证据表明，在环境条件下以及对水分胁迫的响应中，橡树向地下输送碳以激发微生物活性的程度超过糖枫，这表明降水减少可能对微生物活性产生相应影响。因此，我们检验了以下假设：与各自的对照相比，橡树和糖枫地下碳分配的差异会刺激橡树处理土壤中的微生物活性，并降低糖枫处理土壤中的微生物活性。我们发现，该处理导致糖枫处理地块的氮矿化、土壤呼吸和氧化酶活性下降。这些下降可能是由于糖枫树木减少了向土壤的根系碳转移。相比之下，降水减少处理增强了橡树根际的土壤呼吸以及氮矿化速率和过氧化物酶活性。这种增强的活性表明，在水分胁迫期间，橡树根系提供了最佳的根际条件来激发微生物活性，以支持净初级生产。随着美国东部森林预计未来降水的变化，我们表明植物 - 微生物相互作用的强度决定了降水减少对土壤碳和养分循环的影响程度。
