Honey mesquite (Prosopis glandulosa Torr.) may maintain apical dominance after a treatment that causes partial top-kill (PTK) and leaves canopies with “stem flagging.” In contrast, top-killing treatments stimulate multistemmed regrowth (i.e., basal sprouting; BSP). Because this difference may impact competition with grasses, a better understanding of physiology associated with PTK and BSP canopies compared with untreated canopies is needed. We quantified predawn leaf water potential (Ψ_PD), leaf-level gas exchange rates (photosynthesis [A] and stomatal conductance [g_s]), and whole-tree stomatal conductance (G_s) of untreated, PTK, and BSP mesquites 2−11 yr after aerial herbicide application in a north Texas savanna. Total leaf area was nearly 4 × greater in untreated and BSP compared with PTK trees. In a few situations where soil moisture stress was greatest, untreated mesquites exhibited more negative Ψ_PD and lower leaf-level gas exchange than did PTK mesquites. BSP mesquites occasionally had greater Ψ_PD and leaf-level gas exchange than untreated mesquites. Since imbalances in root-to-shoot ratios caused by PTK were largely not manifested at the leaf-physiology level, PTK mesquites likely adjusted rapidly to herbicide disturbance. When g_s was scaled to the whole canopy, G_s estimates were 3–4 × greater in untreated and BSP than PTK trees. Thus, canopy leaf area was the primary driver of differences in whole-canopy G_s. It is LIKELY that transpiration would be lower in a stand of untreated mesquites compared with PTK mesquites of similar stand density and basal areas before treatment, as results from comparing untreated and PTK mesquites indicate. Partially top-killed trees that maintain apical dominance and do not resprout should compete less with grasses for water and light and facilitate species diversity and heterogeneity.

引起部分顶杀（PTK）并带有“茎杆标记”的冠层的治疗后，蜂蜜豆科灌木（Prosopis glandulosa Torr。）可能会保持根尖的优势。相比之下，杀伤力最高的疗法会刺激多茎再生成（即基底发芽； BSP）。由于这种差异可能会影响与草的竞争，因此与未处理的树冠相比，需要更好地了解与PTK和BSP树冠相关的生理。我们量化黎明前叶水势（Ψ _PD），叶级的气体交换率（光合作用[甲]和气孔导度[克_小号]），和全树气孔导度（g ^_小号）未经处理的PTK和BSP在北德克萨斯大草原上进行空中除草剂施药后2-11年。与PTK树相比，未经处理的BSP和BSP的总叶面积大了近4倍。在一些土壤水分胁迫最大的情况下，未经处理的豆科灌木皮表现出比PTK豆科灌木更大的负_PD和较低的叶面气体交换。与未经处理的豆科灌木相比，BSP豆科灌木有时具有更大的_PD和叶面气体交换。由于PTK引起的根与茎比的失衡在叶生理水平上基本没有表现出来，因此PTK豆科灌木可能很快适应了除草剂的干扰。当g _s缩放到整个树冠时，G _s未经处理和BSP的估计值比PTK树高3-4倍。因此，冠层叶面积是整个冠层G _s差异的主要驱动力。幸运的是，与未经处理的豆科灌木丛相比，未经处理的豆科灌木丛的蒸腾量要比处理前的相同林分密度和基部面积的PTK豆科灌木低。保持顶端优势并且不萌芽的部分顶级杀伤力强的树木应与草竞争较少的水分和光照，并促进物种多样性和异质性。