Spatial Analysis of Astragalus verus Olivier Dieback: Understanding Patterns and Implications for Conservation in
Asieh Sheikhzadeh1, Hossein Bashari1, Mostafa Tarkesh Esfahani1
1Department of Natural Resources Isfahan University of Technology Isfahan Iran.
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Astragalus verus Olivier, a species native to Iran, is experiencing dieback, particularly in the Zagros and Central Iran regions. This study examines whether dieback patterns are spatially non-random and influenced by soil conditions. Twelve rangeland sites dominated by A. verus and showing signs of dieback were selected. At each site, a 100 m2 plot was randomly established to record the coordinates of all perennial species, focusing on live and dead A. verus individuals, followed by soil physicochemical analyses. Spatial patterns were evaluated using Ripley's K functions and nearest neighbor indices. Dieback showed positive correlations with sand content and electrical conductivity, and negative correlations with soil moisture, silt, and clay. While the overall plant community shifted from clumped to uniform spatial patterns with increasing spatial scale (distance from reference plants), the spatial distributions of live and dead A. verus individuals remained largely random, suggesting ecological independence. These findings indicated that A. verus mortality is likely driven by localized environmental stressors rather than density-dependent interactions and highlight the value of spatial point pattern analysis for diagnosing species decline and guiding conservation in rangeland ecosystems.
