我国林农生态系统温室气体收支管理的净减排与可行性研究

Forest and cropland ecosystems play important roles in terrestrial ecosystem greenhouse gas (GHG) budget, and may make substantial contribution to the application of the Intended Nationally Determined Contribution (INDC) in Paris Agreement. Based on multi-source data blending from field survey in typical regions, modeling, literature survey, the characters and spatial-temporal patterns of the three main GHGs, i.e., CO2, CH4 and N2O fluxes from forest and cropland ecosystem will be clarified, concerning the carbon stock dynamics, carbon loss from disturbance, fossil energy and material consumptions, trace gas flux and substitution of fossil energy and products. The influence of major forest and cropland management measures and forest-cropland mutual conversion such as Grain for Green and reclamation through deforestation on GHGs budgets and off site GHG leakage would also be revealed. And focusing on the effectiveness and persistence of GHG mitigation and sequestration, a set of forest and cropland ecosystem management GHG budget and net GHG mitigation estimation methodologies would be further summed up and assembled. Based on the estimation of net GHG mitigations of the management practices, integrated with resource and economic feasibility analysis including resource supply and consumption, economic cost and stakeholders’ income, this study will build a forest & cropland GHG mitigation management feasibility and net mitigation model (FeaCANM- Forest & Cropland). According to different content and extent of ecosystem management and forest-cropland mutual conversion, carbon exchange market, and regional resource and energy availability and consumption, scenarios would be set and inputted to FeaCANM. Forest and cropland ecosystem GHG mitigation and its spatial distribution and temporal dynamics in different scenarios would be subsequently predicted, and the potential contribution of forest and cropland ecosystem management to the application of China’s INDC would also be clarified. Finally, this study would present forest and cropland GHG mitigation management zoning, and provide technical approaches, management strategies and policies to enhance net GHG mitigation and promote the feasibility of the mitigation measures.

研究拟基于典型地区实地调查、模型模拟以及文献调研的多源数据融合，明确我国森林和农田生态系统三种温室气体（GHG）—CO2、N2O和CH4收支特征和时空格局。揭示我国林农生态系统管理措施及退耕还林等林农土地用途转变过程对系统边界内外GHG收支的影响及GHG泄漏特征，基于固碳减排有效性和持久性，构建森林和农田生态系统管理措施GHG净减排算法集。结合资源消耗和供给、经济成本和相关者收入变化等资源、经济可行性分析，建立我国林农生态系统减排增汇管理可行性及可行净减排潜力评估模型FeaCANM。设立林农管理措施、林农土地用途转变、碳交易和资源能源利用情景，分析不同时空尺度和管理情景下林农GHG净减排效果及其空间分异和时间动态，明确各情景下林农生态系统管理对履行《巴黎协定》国家自主承诺的贡献，并提出我国森林和农田生态系统GHG减排增汇的空间区划、能力提升途径和政策建议。

项目执行的四年间，在各方面均明确了我国森林和农田生态系统不同类型温室气体收支的时空格局和驱动因素；揭示了管理措施和林农土地用途转变对 GHG 收支的影响及其时空分异规律；明晰了资源限制和经济成本有效性对我国森林和农田生态系统 GHG 减排管理措施可行性的制约作用，评估了不同生态系统管理、资源和经济条件情景下的可行净减排潜力，为我国森林和农田 GHG 减排增汇管理提出了理论依据、科学方法和政策建议。.明确林农温室气体 收支的时空格局和驱动因素方面：项目在细化落实森林生态系统 GHG 收支分析方案的基础上研究构建了包括CANM森林林业等森林碳计量与净减排系系列核算方法、核算了我国森林生态系统管理下的温室气体收支，以及林业生产的温室气体收支情况，明确了我国森林的净碳汇。同时，项目在农田生态系统碳足迹-水足迹耦合估算方案基础上，构建了农田生态系统碳足迹-水足迹耦合估算方法，农田管理碳计量与净减排核算方法，并明确了我国主要作物生产的碳足迹的时空分布。.揭示管理措施和林农土地用途转变对 GHG 收支的影响方面：研究完善了系列CANM系列方法。针对我国农业活动，构建了包括CANM-化肥施用等方法，明确了按照国家推荐量施肥，减少化学肥料对我国针对我国生态系统管理措施的净减排效应。针对我国林业重大生态工程特别是造林活动，建立了针对重大生态工程的CANM-EP方法，核算了京津风沙源治理工程一期的温室气体净减排效益。建立了用于林农生态系统转换的CANM-CFI方法，评估了我国林农转换的净减排；并分析了气候变化和CO2浓度升高下重大生态工程和土地利用变化对生态系统碳汇的影响。.在评估不同生态系统管理、资源和经济条件情景下的可行净减排潜力为我国森林和农田 GHG 减排增汇管理提供理论依据、科学方法和政策建议方面：项目从耕地资源和粮食产量的角度，建立了明确了我国农林土地利用转换的净温室气体收支，揭示了维护耕地资源和粮食安全前提下森林-农田生态系统类型转换固碳的资源可行性；以华中华南地区为研究对象，明确了不同造林类型退耕还林实施者成本收益和经济可行性，以京津风沙源治理工程区为研究区域，分析了气候变化和CO2浓度升高背景下，重大生态工程影响区域碳汇的同时对区域主要生态系统服务的影响，明确管理措施固碳的生态可行性。此外，提出了中国陆地生态系统碳汇巩固和提升区划，并在青藏高原区域进行应用。