Data Sheet 1_Global soil moisture dynamics: attribution of contributions and their association with GPP.docx

Soil moisture (SM) is central to the global land-atmosphere interaction and is of significant research importance. However, the dynamic structural features of SM remain insufficiently explored. This study utilizes GLDAS-Noah SM data from 1948 to 2024 to develop a collaborative framework for quantifying SM contributions, based on “three-dimensional decomposition + covariance attribution.” It decomposes Total Soil Moisture Variability (TSMV) into two major temporal dynamics: long-term trends (Trend) and inter-annual variability (IAV), assessing the contributions of different soil depths, seasonal variations, and temporal dynamics to TSMV, thereby laying the methodological groundwork for analyzing global TSMV structural features. Furthermore, the relationship between SM and the gross primary productivity (GPP) of different ecosystems remains unclear. This study further integrates the MODIS MCD12C1 and GOSIF GPP datasets to explore the correlation between SM and GPP on a global scale. The results indicate that between 2000 and 2024, global Total Soil Moisture (TSM) shows a marked declining trend, with SM decreasing synchronously across all seasons. The IAV contribution from the 40–200 cm soil layer to TSMV is more significant, and this contribution exhibits notable spatial variation. Globally, SM and GPP show an overall positive correlation, particularly in the 10–100 cm root zone of grasslands and croplands, where the correlation is especially pronounced.

土壤湿度（Soil Moisture, SM）是全球陆地-大气相互作用的核心要素，具有极高的研究价值。然而，当前对土壤湿度的动态结构特征仍探究不足。本研究采用1948年至2024年的GLDAS-Noah土壤湿度数据集，构建了一套基于"三维分解+协方差归因"的量化土壤湿度贡献度的协同分析框架。研究将总土壤湿度变率（Total Soil Moisture Variability, TSMV）分解为两大时间动态分量：长期趋势与年际变率（Inter-Annual Variability, IAV），并评估了不同土壤深度、季节变化及时间动态分量对总土壤湿度变率的贡献，为全球总土壤湿度变率的结构特征分析奠定了方法学基础。此外，不同生态系统的土壤湿度与总初级生产力（Gross Primary Productivity, GPP）之间的关联仍尚不明确。本研究进一步整合MODIS MCD12C1与GOSIF GPP数据集，在全球尺度上探究了土壤湿度与总初级生产力的相关性。研究结果显示：2000年至2024年间，全球总土壤湿度呈现显著下降趋势，各季节土壤湿度均同步降低；40–200厘米土层的年际变率对总土壤湿度变率的贡献更为突出，且该贡献存在显著的空间差异；全球范围内，土壤湿度与总初级生产力整体呈正相关关系，尤其在草地与农田的10–100厘米根系层区域，二者相关性尤为显著。