祁连山土壤有机碳沿梯度变化规律及机理研究

The Qilian mountains range is one of the famous mountain ranges in northwest China, with elevation generally ranging from 2000 to 5000 meters above sea level. The vertical variation of vegetation and soil types are significant, and the accumulation of soil organic carbon varying by elevation is mainly affected by natural factors such as temperature and precipitation, and also by human activities. Due to the harsh conditions in alpine regions, the effects of human activities on natural vegetation are limited. Therefore, the Qilian Mountains are very ideal regions for studying the effects of climate change on soil carbon in different vegetation communities. The study will investigate and analyze the soil organic carbon at different ecosystems by elevations, and determine the distribution patterns of soil organic carbon content and density under different topographic conditions. The effects of climatic factors and human activities will be analyzed to explore the possible mechanisms that how soil moisture, radiation, nutrients, and biomass affect soil carbon under complex topography. Based on the profile pedotransfer functions and continuous soil organic carbon density method, we will establish soil organic carbon prediction equations with elevation, aspect and depth as independent variables on sloping areas. In addition, at the regional scale, we will construct soil carbon distribution model based on machine learning algorithms. This will be fundamental for the accurate estimation and dynamics prediction of soil carbon as well as ecological protection engineering in alpine regions.

祁连山是西北地区著名的山系之一，海拔一般在2000~5000m。植被类型与土壤类型的垂直变化显著，沿海拔梯度变化的土壤有机碳的累积主要受气温和降水等自然因子的影响，但同时又受人类活动的影响。由于区域高寒条件的制约，天然植被受人类影响有限。因此，本地区可为研究气候变化对不同群落土壤碳的影响提供非常理想的场所。项目拟开展不同海拔生态系统土壤碳研究，确定不同地形条件下有机碳含量和密度的分布特征和规律；分析气候条件和人类活动对土壤有机碳的影响，探讨不同地形条件下的土壤含水量、辐射量、土壤养分和植被生物量对土壤有机碳累积的影响机制；借鉴剖面土壤转换函数法和连续土壤有机碳密度法，建立包含海拔、坡向和深度的坡面土壤有机碳预测方程；基于机器学习算法，构建区域有机碳分布模型。为山地土壤有机碳储量的准确估算和演变及山区生态保护工程提供数据支撑。

祁连山是我国西北地区著名的山系之一，海拔一般在2000~5000m。植被类型与土壤类型的垂直变化显著，沿海拔梯度变化的土壤有机碳的累积主要受气温和降水等自然因子的影响，但同时又受人类活动的影响。由于区域高寒条件的制约，天然植被受人类影响有限。因此，本地区可为研究土壤有机碳沿环境梯度变化规律及其机理提供非常理想的场所。项目基于不同空间尺度系统地野外土壤和植被调查数据，对祁连山土壤有机碳沿环境梯度的变化规律及机理进行了系统地研究。主要取得了以下研究成果。第一，量化了山区坡面尺度上土壤有机碳空间异质性，构建了土壤有机碳三维变化模拟模型，基于数字土壤制图技术和高分辨率遥感影像，完成了祁连山林草复合小流域2m分辨率土壤有机碳制图，量化了不同海拔带内坡向效应及其影响机制；第二，系统分析了高寒山区流域尺度上土壤有机碳储量、服务价值、格局、影响因素及未来演变规律，明确了气候、地形、植被、土地利用等对土壤碳库的影响机制；第三，分析了祁连山及其周边区域土壤碳库格局及驱动因素，构建了基于机器学习算法和瓦片系统的区域尺度上土壤碳库评估模型，首次完成了祁连山30m分辨率高精度土壤有机碳产品，明确了区域尺度上环境变化对土壤碳的影响。项目完成了申请书中的预期目标，在国内外主流期刊共发表论文20篇，发布数据集2套，授权专利3项，获得省部级一等奖2项。以上成果引起国内外学者关注和引用，制作完成的祁连山高分辨率土壤碳密度数据集已提供给国家冰川冻土沙漠科学数据中心供公开下载。项目研究不仅提升了对高寒复杂地形条件下土壤有机碳多尺度异质性及其驱动机制的认识，相关数据产品还可以服务于祁连山生态和水文过程模拟研究，为祁连山国家公园建设和甘青两省“双碳”目标的实现提供数据和技术支撑。