Predictors of a successful external cephalic version: a population-based cohort study.

Vegetation transpiration is a central pathway through which semi-arid grasslands return plant-accessible water to the lower atmosphere and participate in precipitation recycling. In water-limited ecosystems, vegetation is therefore not only a passive recipient of rainfall but also a mediator of land–atmosphere water exchange. Quantifying the contribution of transpiration-derived moisture to precipitation is important for diagnosing hydroclimatic sensitivity, ecosystem water availability, and grassland resilience under climate variability (; ). The Inner Mongolia Autonomous Region (China) occupies a transition between the East Asian monsoon and the mid-latitude westerlies, a critical hydroclimatic boundary zone with strong interannual precipitation variability and tight land–atmosphere coupling across extensive grasslands and agro-pastoral mosaics (; ). In such settings, small shifts in the balance between large-scale advection and locally recycled vapor can alter rainfall efficiency, isotopic composition, and soil–plant water availability (; ). Separating vegetation transpiration from surface evaporation and externally advected moisture is therefore necessary for understanding how grassland vegetation contributes to the regional precipitation budget. Zhenglan Banner provides a useful testbed for this question because it is embedded in this regional hydroclimatic gradient and contains semi-arid vegetation, shallow groundwater influence, and event-scale isotope observations (; ). Conceptually, this framing builds on decades of work linking precipitation isotopes to moisture origin and phase-change history, from the meteoric-water line and condensation temperature effects to kinetic enrichment during evaporation and sub-cloud exchange (). Recent syntheses show that continental precipitation often contains a substantial recycled component and that land-surface change can shift source regions and delivery pathways of moisture (; ). For semi-arid grasslands, this recycled component has a direct plant-ecological meaning because it connects vegetation water use, canopy–atmosphere exchange, and the moisture supply contributing to precipitation. Eulerian–Lagrangian tracking and analytical frameworks have mapped the origin and fate of atmospheric water, emphasizing the dynamical controls on terrestrial recycling and its sensitivity to surface fluxes and circulation anomalies (; ). Over northern China, monsoon–westerlies interactions modulate moisture transport and vertical motion, yielding coherent swings in rainfall and extremes across the monsoon boundary zone, conditions emblematic of Inner Mongolia’s hydroclimate (; ). These insights motivate a vegetation-aware view of precipitation recycling that is spatially explicit, event-resolved, and mechanistically interpretable, while still accounting for the competing roles of plant transpiration, surface evaporation, and advected vapor (). Stable water isotopes provide a practical basis for separating these moisture sources because they integrate moisture history across space and time (; ). Classical isotope theory explains how equilibrium and kinetic fractionation imprint δO, δD (equivalent to δ²H), and deuterium-excess on atmospheric vapor and precipitation as functions of condensation temperature, humidity, transport history, and re-evaporation, while global datasets such as GNIP provide empirical baselines that connect these fractionations to regional circulation regimes (; ). However, using isotopes to identify vegetation-mediated recycling remains difficult in semi-arid interiors. isotope records are sparse, precipitation is intermittent, satellite variables are often incomplete during cloudy or convective periods, and two land-derived components—vegetation transpiration and open-water or soil evaporation—must be separated from externally advected moisture under limited event samples (; ). These limitations restrict the direct use of isotope-informed mixing models for estimating plant-transpiration contributions at event and annual scales.