Understanding processes determining soil carbon balances under perennial bioenergy crops CARBO-BIOCROP

与一年生粮食作物相比，有证据表明，多年生生物能源作物生产的生物燃料具有积极的温室气体减排潜力。然而，这种效益的大小最近受到质疑，因为长期和间接影响可能大大减少种植制度产生的任何温室气体节约。事实上，对土壤C的影响已被确定为生物能源所带来的净碳当量效益的生命周期分析中的薄弱环节。氧化亚氮（N2O）和甲烷（CH4）排放率的变化也与之相关，因为它们具有较大的温室气体变暖潜势，但这些变化对于多年生生物能源种植系统来说大多无法量化。虽然已经为农业和传统森林系统开发了几种土壤碳和微量气体模型，但这些模型尚未被参数化并验证用于土地利用向多年生生物能源作物的过渡。为了预测种植生物质作物后10到30年的有机碳变化，我们需要确定(a)在主要生物质作物下，碳在数量、质量和向土壤中的碳安置方面的周转动态和碳通量差异；(b)克服过渡期间原有土壤碳短期损失的机制；(c)可预测的基于过程的定量建模方法。探讨未来最佳土壤碳管理方案。该项目的总体目标是更好地了解由于土地从可耕地/草地转变为陆地可再生能源而导致土壤碳储量和库变化的基本土壤过程。该项目侧重于土地利用变化的影响，特别是对多年生生物能源作物（快速生长的SRC树和草）的影响，目前在这方面存在重大的知识空白。该项目将产生新的证据，以改善目前对土壤碳过程、固存和排放如何受到多年生能源作物的影响的理解。与种植粮食作物和使用化石燃料生产热能、电力和液体燃料相比，使用这些作物生产生物能源和生物燃料是否会显著减少碳排放，土壤碳平衡是辩论的关键。从长期来看（超出本项目的生命周期），这将使英国不同气候和土壤类型的陆基生物能源系统的温室气体（C当量，简称为C）减排潜力的动态、空间明确建模成为可能。我们希望为英国开发“碳机会地图”。该项目的工作将分三个工作包进行：数据综合（WP1）、实验数据收集（WP2）和建模（WP3）。在整个项目中，我们将利用其他资源，包括在Brattleby和Aberystwyth的两个旗舰站点，在那里建立了商业规模的种植园，并在其他地方资助的一些长期测量和监测活动正在进行中。类似地，来自项目内部的建模资源是广泛的，并且是由其他资源资助的，这些资源将用于这里的工作。它们包括DNDC、JULES、ROTH C和正在进行的芒草和SRC建模方法。产出将包括一个新的生物能源作物土壤碳综合数据数据库。我们将测试和校准基于过程的模型，这些模型能够模拟英国多年生生物能源作物的土壤有机碳、碳固存和温室气体排放的动态。我们将增加对生物能源种植系统下土壤过程的基本理解，包括菌根关联的作用和生物炭作为优化土壤碳和植物生长潜力的有效性。我们将开发未来“碳机会”制图的能力。

In contrast to annual food crops, evidence suggests that biofuels from perennial bioenergy crops have a positive greenhouse gas (GHG) mitigation potential. However, the magnitude of this benefit has been recently questioned, since long-term and indirect effects may considerably reduce any GHG savings generated by the cropping system. Indeed, impacts on soil C have been identified as the weak link in life-cycle analysis of net carbon-equivalent benefit presented by bioenergy. Changes in rates of nitrous oxide (N2O) and methane (CH4) emission are relevant too since they have a large GHG warming potential, but these changes are mostly unquantified for perennial bioenergy cropping systems. Although several soil carbon and trace-gas models have been developed for agricultural and conventional forest systems these have not been parameterized and validated for transition of land-use to perennial bioenergy crops. To predict the changes in SOC that will occur one to three decades after establishing biomass crops, we need to establish (a) differences in turnover dynamics and fluxes of carbon under key biomass crops in terms of amount, quality and placement of carbon into the soil from the plant, and (b) mechanisms to overcome short-term loss of pre-existing soil carbon during transition (c) quantitative, process-based modeling approaches that are predictive, to explore future scenarios for optimum soil carbon management. The overarching aim of this project is to provide improved understanding of fundamental soil processes resulting in changes of soil carbon stocks and pools as a result of land conversion from arable/grassland to land-based renewables. The project focuses on impacts of land use change specifically to perennial bioenergy crops (fast growing SRC trees and grasses) where there is currently a significant knowledge gap. This project will generate new evidence to improve current understanding on how soil carbon processes, sequestration and emission, are affected by the introduction of perennial energy crops. The soil carbon balance is key to informing the debate on whether using these crops for bioenergy and biofuels will result in significant carbon savings compared to land use for food crops and the use of fossil fuels for heat, power and liquid fuels. In the long-term (beyond the life of this project), this will enable dynamic, spatially explicit modeling of GHG (C equivalents, abbreviated here as C) mitigation potential of land-based bioenergy systems across different climates and soil types of the UK. We wish to develop 'Carbon Opportunity Maps' for the UK. The work of the project will be undertaken in three workpackages dealing with data synthesis (WP1), experimental data collection (WP2) and modeling (WP3). Throughout the project we will use leverage of other resources including two flagship sites at Brattleby and Aberystwyth, where commercial-scale plantations are established and where several long-term measuring and monitoring activities are underway funded from elsewhere. Similarly, the modeling resources from within the project are extensive and funded from other sources that will be levered against the work here. They included DNDC, JULES, ROTH C and on-going modeling approaches for miscanthus and SRC. Outputs will include a new database of synthesized data for soil carbon under bioenergy crops. We will have tested and calibrated process-based models that are capable of simulating the dynamics of soil organic carbon, carbon sequestration and greenhouse gas emissions for perennial bioenergy crops in the UK. We will provide increased fundamental understanding of soil processes occurring under bioenergy cropping systems including the role of mycorrhizal associations and the effectiveness of biochar as a potential to optimize soil carbon and plant growth. We will develop capacity for future 'carbon opportunity' mapping.