Historical climate stability and anthropogenic refugia jointly shape the biogeography of old trees in the central part of the Yellow River Basin of China

Old trees are affected by natural drivers (climate, topography, and soil) and protected by cultural factors (temples, ancestral halls, and legends). However, our knowledge of how the presence and growth status of old trees might be maintained by intertwined climatic, soil, and cultural forces is remains limited. To decouple their relative significance on the spatial presence and maximal growth (diameter at breast height) of the top ten old tree species, we utilized a novel historical baseline (1989 pre-urbanization census) in the central Yellow River Basin, China to eliminating the confounding effects of recent rapid urbanization. We combined four cultural drivers (human footprint, and distances to temples, ancestral halls, and legends) and seven natural drivers (elevation, temperature seasonality, precipitation stability, aridity index, soil pH, soil bulk density, and soil fertility Principal Component Analysis), independently evaluating their effects using Ensemble Species Distribution Models (SDMs) and XGBoost- SHapley additive explanation machine learning. We found that distances to temples and ancestral halls are the important decisive factors for the spatial presence of old trees, exhibiting strict distance-decay thresholds. Specifically, religious sites favored evergreen conifers, with 84.34% of Platycladus orientalis and 62.92% of Pinus tabuliformis populations concentrated within a < 3 km core radius. The presence probability dropped sharply beyond specific cultural boundaries: 0.6 km for P. orientalis , 0.7 km for both Sabina chinensis and Sophora japonica , and 1.2 km for P. tabuliformis and Ulmus pumila . In contrast, the maximal growth of old trees is driven by a dual-refuge mechanism relying heavily on historical climate stability (precipitation stability) and soil micro-environments. Our findings have significant ramifications for conservation: (1) preserving historic structures and old trees in tandem to establish holistic biocultural units; (2) leveraging traditional clan networks as essential community-based conservation sanctuaries; and (3) implementing targeted management strategies that optimize soil physical properties while buffering against climate aridity to ensure precise conservation.