Iconica: Impact of Long-Term Phosphorus Additions on Carbon Sequestration and Nitrogen Cycling in Agricultural Soils

Greenhouse gas (GHG) emissions pose a challenge to the modern world and further generations. One possible strategy for climate change mitigation is enhancing soil carbon (C) sequestration by promoting C uptake from the atmosphere and storing it in the form of soil organic matter (SOM) to reduce increases in atmospheric carbon dioxide (CO2) concentration. A pivotal process hypothesized to control soil organic C (SOC) sequestration is the soil microbial C pump which is based on microbial decomposition of organic litter and release of new organic substances. The coupled Carbon-Nitrogen-Phosphorus cycles (CNP) mediate SOM formation and turnover, for example, soil phosphorus (P) is a key nutrient for crop growth and P limitation can reduce plant and soil microbial biomass affecting SOC sequestration. In vitro studies have shown that soil P concentration significantly affects emissions of nitrous oxide, a potent greenhouse gas, soil nitrogen (N) mineralisation, N immobilisation and C fluxes. Varying P level impacts on microbial composition and activity of organisms, which are predicted to control specific transformation pathways within the soil C and N cycles, will influence the stabilisation of GHG emissions, SOC and nutrients. While the stoichiometric constraint of P on plant growth is known, the effect of this constraint on other soil processes at different P levels is uncertain, particularly in relation to GHG emissions and N and C cycling. Agricultural soils are considered likely storage sites for carbon making them a potential tool for climate change mitigation. An increase in SOM has additional benefits, including improvements in soil fertility, water retention and texture, which supports crop productivity and biodiversity. Restoring and maintaining SOM can be achieved by adopting management practices which increase C sequestration and stabilize C in the soil matrix. This relies on development of tools in the form of agricultural practices that favour soil C sequestration, such as long-term P or N fertilization. To predict the effect of certain agricultural management on SOC, the mechanisms of C transformations in soil must be understood. At its core, we must study soil microbial communities that mediate C transformations. Exploring the mechanisms of C cycle can lead to the development of novel sustainable techniques for land management that may reduce GHG emissions and favour soil fertility. The key to understanding these processes is integrating the role of microbial communities.

温室气体（Greenhouse gas, GHG）排放是当代世界乃至后世子孙面临的严峻挑战。缓解气候变化的可行策略之一，是通过促进大气碳吸收、将碳以土壤有机质（soil organic matter, SOM）形式储存于土壤中，来增强土壤碳固存（soil carbon sequestration, C）能力，以减缓大气二氧化碳（atmospheric carbon dioxide, CO₂）浓度的上升。
据推测，调控土壤有机碳（soil organic C, SOC）固存的核心过程是土壤微生物碳泵（soil microbial C pump）——该过程依托微生物对有机凋落物的分解与新生有机物质的释放。碳-氮-磷循环（Carbon-Nitrogen-Phosphorus cycles, CNP）的耦合过程介导了土壤有机质的形成与周转：例如，土壤磷（soil phosphorus, P）是作物生长的关键营养元素，磷限制会降低植物与土壤微生物生物量，进而影响土壤有机碳固存。
体外实验表明，土壤磷浓度会显著影响一氧化二氮（一种强效温室气体）的排放、土壤氮（soil nitrogen, N）矿化、氮固持（N immobilisation）与碳通量（C fluxes）。磷水平的变化会影响微生物群落组成与生物活性，而这些因素被认为是调控土壤碳、氮循环中特定转化途径的关键，最终会对温室气体排放、土壤有机碳与养分的稳定性产生影响。
尽管磷对植物生长的化学计量约束效应已被广泛认知，但这种约束在不同磷水平下对其他土壤过程的影响仍不明确，尤其是在温室气体排放以及氮、碳循环方面。
农业土壤被视为潜在的碳储存库，因此可作为缓解气候变化的潜在手段。土壤有机质的增加还能带来额外益处，包括提升土壤肥力、保水性与质地，从而助力作物生产力与生物多样性的维持。
通过采用能够增加碳固存并稳定土壤基质中碳的管理措施，可实现土壤有机质的恢复与维持。这有赖于开发有利于土壤碳固存的农业实践工具，例如长期施用磷或氮肥。
若要预测特定农业管理措施对土壤有机碳的影响，必须明晰土壤中的碳转化机制。从根本上来说，我们需要研究介导碳转化的土壤微生物群落（soil microbial communities）。
探索碳循环机制，有助于开发新型可持续土地管理技术，从而减少温室气体排放并提升土壤肥力。理解这些过程的关键，在于整合微生物群落的作用。