积雪变化对东北农业主产区春季土壤干旱化的影响及机制

The Northeast China is the second largest region in China with stable accumulated snow area and it differs from other accumulated snow areas in its highest average annual accumulated snow reserves and the most obvious interannually variability of accumulated snow reserves. Northeast China is also experiencing the most significant climate warming. In recent years, there is a continuous expansion and increasing trend of spring soil drought in the Songnen- Sanjiang Plain, Songnen-Sanjiang Plain, an important commodity grain base of China. Accumulated snowmelt water is an important water resource in this region. Under the pressure of climate warming, the soil water availability and supply characteristics have been changed along with the decreasing of accumulated snow reserves and the advancing snow melt. Therefore, it is essential to examine the impact of accumulated snow change on the spring soil drought in the Northeast China. In this study, we propose to examine the impact and mechanism of accumulated snow change on soil spring drought in Northeast China since the 1980s, with the research plan of accumulated snow - snow melt - soil moisture and the study method of experiment - model establishment - integrated simulation. This study will enhance our capability to respond to the cryosphere change and therefore, provide a scientific basis for the protection of national food production security.

东北地区是我国第二大稳定积雪区，以其积雪年均储量大和年际变率最明显而著称，东北地区又是我国重要的商品粮基地，是近30年中国乃至全球增温最显著区域。近年来东北农业主产区（松嫩-三江平原）春季土壤干旱不断加重并持续扩张，凸显出土壤干旱化趋势。积雪融水是春季土壤重要水资源之一，在气候变暖背景下，积雪减少并提前集中融化，使土壤水资源供应量减少、补给时间提前且短期流失，使农业播种错失融雪水补给期，缺失融雪水补偿量，积雪变化对东北春季土壤干旱化的影响已不容忽视。本项目以积雪—融雪—土壤水分为研究主线，采用试验—模型构架—集成模拟等研究方法，探讨20世纪80年代以来，东北积雪变化对松嫩—三江平原粮食主产区春季土壤干旱化的影响及机制，提升应对冰冻圈变化的能力，为保障国家粮食生产安全战略提供科学依据。

本研究基于多源数据，采用控制试验、统计、同位素、模拟等方法，揭示了东北积雪对松嫩—三江平原春季土壤干旱化的影响及机制，对于保障国家粮食生产安全具有重要意义。.研究结果显示，1981-2019年中国东北部高纬度地区降雪的指标均发生了显著变化，降雪初日、雪季长度是对气候变暖最敏感的指标，东北部向多雪化转变，降雪更多地以暴雪、大雪方式出现，而小雪显著减少，中西部地区则向中雪和小雪形式转化；东亚大槽强度减弱、位置偏西及北极涡旋强度减弱是导致高纬度冬季降水偏多及极端降水年份增加的主要原因；东北地区1841-2015年年及各季积雪深度、积雪面积均呈现极显著减少趋势，春季积雪深度和面积减小最为显著，中部及西北部地区积雪深度显著减少，西南部积雪面积明显减少；20世纪80年代以来东北地区表层平均土壤湿度显著变干，松嫩平原显著变干，三江平原不显著；1981-2019年松嫩平原、三江平原积雪深度显著增加，积雪初日逐渐推后，积雪终日提前，积雪期显著缩短；积雪对三江平原春季土壤湿度均无显著贡献，而对松嫩平原有贡献，提出积雪初日推迟，积雪终日提前，积雪期显著缩短加剧了松嫩平原春季土壤向干旱方向发展；定量界定了10cm、30cm、50cm深度的积雪融水对0-30cm土壤湿度的贡献分别为8.13%、8.55%、11.24%；30cm积雪厚度为对土壤含水率敏感的分界线；温度与黑碳相比较，温度对积雪融化贡献率约为73.953%，黑碳为26.047%，黑碳浓度与粒径相比，黑碳浓度对积雪融化贡献率约为70.925%，粒径为29.075%。本研究经过4年的努力，率先提出降雪对气候变暖的敏感指标，厘清了影响其变化的环流机制，突破性地辨析了积雪对东北两大农业区的影响差异，创新性地量化了不同深度积雪融水对0-30cm土壤湿度的贡献，率先模拟了东北积雪黑碳污染及对积雪融化影响贡献率。