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<p>Stomatal conductance (<span class="inline-formula"><i>g</i>_s</span>) of all coexisting species regulates transpiration in arid and semiarid grasslands prone to droughts. However, the effect of drought stress on canopy conductance (<span class="inline-formula"><i>G</i>_s</span>) is debated, and the interactive effects of abiotic and biotic constraints on <span class="inline-formula"><i>G</i>_s</span> remain poorly understood. Here, we used <span class="inline-formula">¹⁸</span>O enrichment above the source water (<span class="inline-formula">Δ¹⁸</span>O) of leaf organic matter as a proxy for <span class="inline-formula"><i>G</i>_s</span> in order to increase the understanding of these effects. Three grassland transects were established along aridity gradients on the Loess Plateau (LP), the Inner Mongolian Plateau (MP), and the Tibetan Plateau (TP), which differ with respect to solar radiation and temperature conditions. Results showed that <span class="inline-formula"><i>G</i>_s</span> consistently decreased with increasing aridity within transects. <span class="inline-formula"><i>G</i>_s</span> on the TP was lower than that on the other two plateaus for a given level of aridity due to low temperature and high radiation. The primary determinant of drought stress on <span class="inline-formula"><i>G</i>_s</span> was soil moisture (SM) on the LP and MP, whereas it was the vapor pressure deficit (VPD) on the TP. Solar radiation exhibited a consistently negative effect on <span class="inline-formula"><i>G</i>_s</span> via drought stress within transects, while temperature had negative effects on <span class="inline-formula"><i>G</i>_s</span> on the TP but no effect on the LP or MP. Adding the interaction of leaf area and abiotic factors increases the percentage of explained variability in <span class="inline-formula"><i>G</i>_s</span> by 17 % and 36 % on the LP and MP, respectively, although this is not the case on the TP, where the climate exerts an overwhelming effect. These results highlight the need to integrate multiple stressors and plant properties to determine spatial variability in <span class="inline-formula"><i>G</i>_s</span>.</p>