Response of degraded Populus euphratica architectural variables to ecological engineering project in the lower Tarim River – A meta-analysis

Abstract

Since its implementation in 2000, the ecological water diversion project (EWDP) has played a pivotal role in rehabilitating degraded desert riparian woodlands in the Tarim River Basin. While an extensive body of peer-reviewed research has objectively quantified the EWDP impacts on Populus euphratica forest regeneration, the predominant reliance on limited tree architectural variables employed in previous studies has constrained deeper understanding of riparian forest-EWDP interactions. This study synthesizes 635 observational datasets extracted from 21 rigorously screened publications searched in Web of Science Core Collection and China Knowledge Network Literature Database (CNKI) through a meta-analytical framework to systematically evaluate EWDP-ecological responses of P. euphratica under varying water management regimes. Our results demonstrate that EWDP significantly enhanced degraded forest recovery metrics, with mean increases of 60.28 % (crown diameter), 6.73 % (radial growth), 8.1 % (branch growth), and 12.81 % (growth ring index), respectively. Multivariate analysis identified dual-channel water diversion as the optimal delivery method, with peak efficacy achieved at annual water allocations of 3 × 10⁸ to 6 × 10⁸ m³ during the P. euphratica growing season (minimum 120 days duration). Notably, a 1–2-year lag effect was observed between water delivery initiation and measurable recovery responses. These findings establish an operational threshold for ecological flow releases and highlight the critical need for phenology-driven water scheduling aligned with P. euphratica species' hydraulic requirements. The proposed adaptive water management framework provides critical insights for optimizing water allocation strategies and ecological rehabilitation in arid regions under increasing hydrological uncertainty.