FACE underground:can trees in mature forests gain greater access to soil nutrients under elevated atmospheric CO2?

面向地下：在大气二氧化碳浓度升高的情况下，成熟森林中的树木能否获得更多土壤养分？

• 批准号: NE/T000449/1
• 负责人: Sami Ullah
• 金额: $ 78.11万
• 依托单位: University of Birmingham
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2020
• 资助国家: 英国
• 起止时间: 2020 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FT000449%2F1
• 关键词: FACE; underground; trees; mature; forests

Land ecosystems including forests capture about 30% of the carbon dioxide (CO2) released by human activities. This uptake is mainly attributed to the beneficial effects of increasing atmospheric CO2 concentrations (eCO2) on rates of photosynthesis (the "CO2 fertilisation effect"). Based on current CO2 uptake rates and the predicted increases in atmospheric CO2 concentrations, an attempt has been made to predict future Carbon (C) uptake by forests using different large-scale models. However, the model estimates are highly uncertain because we lack a clear understanding of how the limited availability of soil nutrients, particularly nitrogen (N) and phosphorus (P), regulate the CO2 fertilisation effect. For example, incorporating nitrogen availability into models reduced predicted uptake rates of CO2 by ~50%, which shows that previous estimates may have been optimistic. Furthermore, previous experiments have focused on young forests and to date there are no large-scale CO2 enrichment experiments in mature temperate forests. This is important because: 1) mature forests in northern temperate regions are currently responsible for almost half (~40%) of the global net C uptake and 2) young forests may be able to increase access to nutrients by increasing root growth under eCO2 to explore more of the soil space, whereas mature forests already have well-developed root systems, so greater carbon allocation to roots and their associated fungal partners (mycorrhizas) may have less potential to increase access to nutrients. Therefore, a realistic assessment of the role of nutrient availability in controlling the responses of mature temperate forests to eCO2 is essential. Given the global significance of temperate forests, the Birmingham Institute of Forest Research (BIFoR), established a CO2 fertilization experiment (>£15 million investment) in a >160 year old deciduous forest stand in Staffordshire in 2017. This is the first such experiment in a mature temperate forests and thus provides a unique opportunity to test a key question: can mature trees gain greater access to limiting nutrients under eCO2 and, if so, which strategies do they employ to do so? Thus, we aim to test the broad hypothesis that under eCO2 a mature, deciduous temperate forest will transfer additional carbon belowground to increase nitrogen and phosphorus availability and subsequent uptake by trees. The research will be undertaken in three plots under eCO2 and three control plots. We will measure root and mycorrhizal hyphal production, and the release of substrates (exudates) from roots throughout the year. We will also carry out a series of experiments to determine the relative roles of roots versus mycorrhizal fungi in controlling rates of decomposition and nutrient cycling, and the extent to which these are affected by eCO2. These decomposition experiments will involve root and/or mycorrhizal fungi exclusion, as well as a novel approach for simulating root exudation. The results will enable us to determine whether, and through which mechanisms, trees can stimulate decomposition and nutrient mobilization under eCO2. Finally, we will determine if the types of nitrogen containing compounds that roots take up changes under eCO2 and how this relates to their availability in the soil. In summary, we will use the first FACE experiment in a mature temperate forest to determine whether mature temperate forest trees will be able to access more soil nutrients under eCO2, and therefore, whether there is likely to be a large and sustained carbon sink in these ecosystems, addressing a major uncertainty in carbon cycle modelling. If our results suggest that the forest uptake will become increasingly nutrient limited in the future then it would have major societal implications as greater cuts in greenhouse gas emissions would be needed to avoid the most dangerous consequences of climate change.

包括森林在内的陆地生态系统捕获了人类活动释放的约30%的二氧化碳。这种吸收主要归因于大气CO2浓度（eCO 2）增加对光合作用速率的有益影响（“CO2施肥效应”）。根据目前的CO2吸收率和预测的大气CO2浓度的增加，试图使用不同的大尺度模型预测森林未来的碳（C）吸收。然而，模型估计是高度不确定的，因为我们缺乏对土壤养分的有限可用性，特别是氮（N）和磷（P）如何调节CO2施肥效应的清晰理解。例如，将氮的可用性纳入模型，使预测的CO2吸收率降低了约50%，这表明以前的估计可能过于乐观。此外，以前的实验都集中在年轻的森林，到目前为止，还没有大规模的CO2富集实验在成熟的温带森林。这一点很重要，因为：1）北方温带地区的成熟森林目前占全球净碳吸收量的近一半（约40%），2）幼龄林可能能够通过在eCO 2下增加根系生长来增加养分的获取，以探索更多的土壤空间，而成熟森林已经有发达的根系，因此，更多的碳分配给根部及其相关的真菌伙伴（菌根）可能不太可能增加获得养分的机会。因此，必须现实地评估养分供应在控制成熟温带森林对eCO 2的反应方面的作用。鉴于温带森林的全球重要性，伯明翰森林研究所（BIFoR）于2017年在斯塔福德郡一个160年以上的落叶林中建立了一个CO2施肥实验（投资超过1500万英镑）。这是第一次在成熟的温带森林中进行这样的实验，因此提供了一个独特的机会来测试一个关键问题：成熟的树木能否在eCO 2下获得更多的限制性养分，如果是这样，它们采用了什么策略来做到这一点？因此，我们的目标是测试广泛的假设，在eCO 2的成熟，落叶温带森林将转移额外的碳belowground，以增加氮和磷的可用性和随后的树木吸收。研究将在eCO 2下的三个地块和三个对照地块进行。我们将测量根和菌根菌丝的生产，以及全年从根中释放的基质（分泌物）。我们还将进行一系列的实验，以确定相对作用的根与菌根真菌在控制分解率和养分循环，以及在何种程度上，这些是受二氧化碳。这些分解实验将涉及根和/或菌根真菌的排斥，以及一种新的方法来模拟根系分泌物。研究结果将使我们能够确定树木是否以及通过何种机制可以刺激eCO 2下的分解和养分动员。最后，我们将确定根吸收的含氮化合物的类型是否在eCO 2下发生变化，以及这与它们在土壤中的可用性有何关系。总之，我们将在一个成熟的温带森林中使用第一个FACE实验，以确定成熟的温带森林树木是否能够在eCO 2下获得更多的土壤养分，因此，这些生态系统中是否可能有一个大的和持续的碳汇，解决碳循环建模中的一个主要不确定性。如果我们的研究结果表明，森林吸收的养分在未来将变得越来越有限，那么它将产生重大的社会影响，因为需要更多地减少温室气体排放，以避免气候变化最危险的后果。

项目成果

Nitrogen cycling in forest soils under elevated CO2: response of a key soil nutrient to climate change

二氧化碳浓度升高下森林土壤的氮循环：关键土壤养分对气候变化的响应

• DOI: 10.5194/egusphere-egu22-178
• 发表时间: 2022
• 作者: Rumeau M

Stimulation of soil gross nitrogen transformations and nitrous oxide emission under Free air CO2 enrichment in a mature temperate oak forest at BIFoR-FACE

BIFoR-FACE 成熟温带橡树林在自由空气 CO2 富集下对土壤总氮转化和一氧化二氮排放的刺激

• DOI: 10.1016/j.soilbio.2023.109072
• 发表时间: 2023
• 期刊: Soil Biology and Biochemistry
• 影响因子: 9.7
• 作者: Sgouridis, Fotis;Reay, Michaela;Cotchim, Suparat;Ma, Jiaojiao;Radu, Aleksandar;Ullah, Sami
• 通讯作者: Ullah, Sami

Soil – atmosphere exchange of greenhouse gases under future climates

土壤

• DOI: 10.5194/egusphere-egu22-10237
• 发表时间: 2022
• 作者: Douwes Dekker N

BIFoR FACE : Water-soil-vegetation-atmosphere data from a temperate deciduous forest catchment, including under elevated CO 2

BIFor FACE：来自温带落叶林流域的水-土壤-植被-大气数据，包括在 CO 2 升高的情况下

• DOI: 10.1002/hyp.14096
• 发表时间: 2021
• 期刊: Hydrological Processes
• 影响因子: 3.2
• 作者: MacKenzie A

Root exudation rate increases, and composition changes in a mature temperate forest under elevated carbon dioxide

二氧化碳升高下成熟温带森林的根系分泌率增加和成分变化

• DOI: 10.5194/egusphere-egu22-5026
• 发表时间: 2022
• 作者: Reay M