塔克拉玛干沙漠咸水滴灌林地土壤碳时空分布与淋溶过程研究

The Taklimakan Desert Highway Shelterbelt is the longest artificial ecosystem that continuously running across a shifting desert in the world, the carbon storage of the shelterbelt-soil-groundwater system has been changing greatly under long-term saline drip irrigation. Through field position monitoring and large-scale lysimeter, combined with laboratory analysis and soil column simulation, the project plans to systematically study and analyze spatial-temporal distribution of soil organic carbon and inorganic carbon, variation of vertical distribution and flux of soil CO2, leaching process of dissolved carbon, and carbon balance process of soil-groundwater in the shelterbelt planted for different years under drip irrigation with different salinity groundwater. We aim to clarify the spatial-temporal distribution of soil carbon and influencing factors in the saline drip-irrigated shelterbelt, identify the changes of carbon storages in shelterbelt soil and groundwater during the utility of saline groundwater, develop and construct the soil carbon leaching model of saline drip-irrigation, predict the impact of long-term saline drip-irrigation on trend of carbon storages in shelterbelt soil and groundwater, explore the measures of irrigation schedules and maintenance management to increase carbon sequestration in soil and groundwater, probe the ecological and environmental significance of carbon cycle of saline drip-irrigated shelterbelt in global climate change. The results may provide decision-making basis for sustainable management and maintenance of the desert highway shelterbelt, rational utilization of regional soil and water resources.

塔克拉玛干沙漠公路防护林是世界上连续穿越流动沙漠最长的人工生态系统，长期的咸水滴灌使防护林-土壤-地下水系统的碳储量发生了极大变化。本项目拟通过野外定位监测和大型蒸渗仪，结合室内分析和土柱模拟，系统研究与分析不同矿化度咸水滴灌条件下不同林龄防护林土壤有机和无机碳的时空分布、土壤CO2垂直分布及通量变化过程、可溶性碳淋溶过程和土壤-地下水碳平衡过程，阐明咸水滴灌防护林土壤碳的时空分布特征及影响因素，查明地下咸水开采利用过程中防护林土壤和地下水碳储量的变化，发展和构建咸水滴灌土壤碳淋溶模型，预估长期咸水滴灌对防护林土壤和地下水碳储量的影响趋势，探索增加土壤和地下水固碳量的灌溉制度和维护管理措施，探讨咸水滴灌防护林碳循环在全球气候变化中的生态环境意义。研究成果可为沙漠公路防护林的可持续管护和区域水土资源的合理开发利用提供决策依据。

长期咸水滴灌使塔克拉玛干沙漠公路防护林-土壤-地下水系统的碳储量发生了极大变化。项目聚焦于沙漠公路防护林生态工程，通过野外定位监测、室内分析和模型模拟，阐明了咸水滴灌防护林土壤碳的时空分布特征及影响因素，查明了地下咸水滴灌防护林土壤碳储量的变化，构建了咸水滴灌土壤碳淋溶方程，预估了沙漠公路防护林土壤的固碳潜力，并应用分子动力学模型模拟了土壤颗粒对有机、无机碳吸附固持过程进行了模拟。结果表明：土壤碳储量受林龄、灌溉水矿化度、土层深度等多重因素的影响，SICD是SOCD的15.14~16.35倍；防护林土壤固碳潜力为7.58 Tg，其中无机碳库占96.4 %；灌溉水矿化度对SDOC和SDIC的垂直分布具有重要影响，同时与土壤含水量、土层深度、EC等因素紧密相关；灌溉水矿化度和离子组成对可溶性碳的淋洗作用差异明显，淋洗强度随着矿化度的升高呈先增后减趋势，且不同盐分淋洗强度峰值时的累积淋洗量各有不同，滤出液EC与DC间存在十分良好的线性关系，可作为估算DC的指标；土壤颗粒吸附固持碳的过程受到土粒大小、pH、离子组成等多重因素的影响，碳酸氢根倾向于和石英表面形成氢键，而碳酸根则倾向于通过阳离子桥的形式吸附；不同阳离子对NOM团簇在伊利石表面的吸附行为影响较大，其固持能力的大小顺序为Ca2+ > Mg2+ > Na+ > K+，NOM的固持不受NOM-阳离子的相互作用影响，而是通过NOM-伊利石的相互作用进行调节。研究结果可为沙漠公路防护林的可持续利用和高效固碳提供有力支撑。