CORAL, Indian Institute of Technology Kharagpur, Kharagpur, 721302, India.
Environ Sci Pollut Res Int. 2024 Oct;31(49):59202-59218. doi: 10.1007/s11356-024-35107-7. Epub 2024 Sep 30.
Soil moisture (SM) interconnects various components of the Earth system and drives the land-atmosphere feedbacks and food production. However, around 40% of global vegetated land experiences SM drying. India is one of the global hotspots of land-atmosphere interactions and an extensively agrarian economy, but underexplored in terms of SM dynamics and its ramifications on food security. Here, we examine the mechanism of SM drying and its implications on cropland productivity in India based on remote sensing measurements and land surface model simulations in recent decades (2000-2019) and future projection of the 21st century. We find SM reduction predominantly in monsoon (4.5%) and winter (3%) seasons that are in the major agricultural seasons of Kharif and Rabi, respectively. Machine learning (ML)-based random forest (RF) reveals that temperature (T, 30.76%) is the dominant driver of SM variability, and then precipitation (P, 26.34%), evapotranspiration (ET, 26.08%) and surface greenness (16.82%). Concurrently, India experiences severe warming in terms of land (0.59 ℃/dec), soil (0.48 ℃/dec) and soil heat flux (SHF, 0.16 W/m/dec) during 2000-2019. Partial correlation analysis between SM and T limiting the influence of P reveals a strong negative (> - 0.5) relationship in the agriculture intensive regions of Indo-Gangetic Plain (IGP) and South India (SI). Drying owing to warming and increased SHF, termed as warming-induced moisture stress, reduces gross primary productivity (GPP) (i.e. browning) and yield of major food crops of wheat, rain-fed rice, maize and soyabean, predominantly in SI and eastern IGP. Granger Causality shows that warming-induced soil moisture stress has a maximum temporal lag of 1 month. In a warming world, the ever-growing population demands more food, and therefore, the warming-induced soil moisture stress is a serious threat to food security in India and similar agro-climatic regions of the world. This calls for climate-resilient agriculture, better agronomic management, improved irrigation and adoption of water-efficient crops.
土壤湿度（SM）连接着地球系统的各个组成部分，并驱动着陆地-大气反馈和粮食生产。然而，全球约有 40%的植被覆盖地区经历着 SM 干燥。印度是全球陆地-大气相互作用的热点地区之一，也是一个以农业为主的经济体，但在 SM 动态及其对粮食安全的影响方面的研究还很匮乏。在这里，我们根据近几十年（2000-2019 年）的遥感测量和陆地表面模型模拟以及 21 世纪的未来预测，研究了 SM 干燥的机制及其对印度耕地生产力的影响。我们发现，SM 主要在季风（4.5%）和冬季（3%）季节减少，这两个季节分别是雨季和冬季，是 Kharif 和 Rabi 的主要农业季节。基于机器学习（ML）的随机森林（RF）的研究表明，温度（T，30.76%）是 SM 变化的主要驱动因素，其次是降水（P，26.34%）、蒸散（ET，26.08%）和地表绿色度（16.82%）。与此同时，在 2000-2019 年期间，印度的陆地（0.59℃/dec）、土壤（0.48℃/dec）和土壤热通量（SHF，0.16 W/m/dec）都经历了严重的变暖。在限制降水影响的情况下，SM 与 T 的偏相关分析揭示了在印度河平原（IGP）和印度南部（SI）农业密集区存在强烈的负相关（>-0.5）关系。由于变暖而导致的 SHF 增加，即变暖引起的水分胁迫，降低了主要粮食作物小麦、雨养水稻、玉米和大豆的总初级生产力（GPP）（即褐变）和产量，这种情况主要发生在 SI 和印度东部 IGP。格兰杰因果关系表明，变暖引起的土壤水分胁迫最大的时间滞后为 1 个月。在一个变暖的世界里，不断增长的人口需要更多的食物，因此，变暖引起的土壤水分胁迫对印度和世界上类似的农业气候地区的粮食安全构成了严重威胁。这就需要发展气候适应型农业、更好的农业管理、改进灌溉和采用节水作物。
