In the mixed C₃/C₄ grassland of the southern Great Plains, United States, the invasive woody legume, honey mesquite (Prosopis glandulosa), affects grass production and composition differently beneath the canopy (subcanopy) than in spaces between trees (intercanopy) due in part to the dominant presence of C₃ Texas wintergrass (Nassella leucotricha) beneath the mesquite canopy and soil enrichment from N-fixation by mesquite. This arrangement, unlike most Prosopis systems worldwide that have C₄ grass or C₃ subshrub understories, uniquely affects grass production spatially and seasonally during mesquite expansion and possibly after anthropogenic removal of mesquite. We compared herbaceous and soil N responses in subcanopy and intercanopy microsites during the first 2 yr following a root-killing herbicide mesquite treatment. Perennial grass (PGR) and total herbaceous (THB) production were greater in treated than untreated intercanopy and subcanopy microsites at 1-yr post treatment, with Texas wintergrass comprising the largest portion of PGR. In yr 2, PGR production declined in both treated microsites with no differences between treatments. However, THB production remained greater in treated than untreated microsites due mainly to increased annual forb production that supplanted PGR production from yr 1. Increased annual forb production in treated microsites in yr 2 was likely due to high rainfall in the fall of yr 1 that stimulated forb seed germination, increased light from the loss of shading by mesquite, and soil inorganic N that increased from yr 1 to yr 2. Pretreatment spatial heterogeneity of herbaceous composition and soil N, caused by mesquite, affected post-treatment patterns of herbaceous production. The unexpected replacement of PGR by annual forbs in yr 2 revealed that grass forage production following brush control can deviate markedly from predicted models under certain conditions.

在美国大平原南部的混合C ₃ / C ₄草原中，入侵性木本豆科植物豆科植物蜂蜜（豆科植物Prosopis glandulosa）对冠层下（亚冠层）草的产量和组成的影响与树间空间（冠层间）的影响不同。部分原因是豆科灌木冠下主要存在C ₃德州冬草（Nassella leucotricha），并且豆科灌木通过固氮作用使土壤富集。这种安排与全球大多数具有C ₄草或C _3的Prosopis系统不同亚灌木灌木林在豆科灌木丛扩张期间以及可能在人为去除豆科灌木丛后，在空间和季节上对草产量有独特的影响。我们比较了根除草剂除草剂豆科灌木处理后的前2年中，亚冠层和冠层间微站点中草和土壤氮素的响应。在处理后的1年中，处理过的多年生草（PGR）和总草皮（THB）的产量高于未处理的冠间和冠层下的微场所，其中德克萨斯州冬草占PGR的最大部分。在第2年，两种处理过的微地点的PGR产量均下降，两种处理之间无差异。但是，经过处理的微型站点的THB产量仍然高于未处理的微型站点，这主要是由于每年的单叶草产量增加，取代了从1年起的PGR产量。在第2年中，经过处理的微型站点的年Forb产量增加，可能是由于第1年的秋季降雨增加，刺激了Forb种子的发芽，由于豆科灌木遮荫的损失增加了光照，并且土壤无机N从第1年增加到了2年。豆科灌木林引起的草本成分和土壤氮的空间异质性影响了草本植物生产的后处理方式。在第2年中，年度草料意外地替代了PGR，这表明在某些条件下，进行刷子控制后的草料生产可能会明显偏离预测模型。豆科灌木林引起的草本成分和土壤N的预处理空间异质性影响了草本植物生产的后处理模式。在第2年中，年度草料意外地替代了PGR，这表明在某些条件下，进行刷子控制后的草料生产可能会明显偏离预测模型。豆科灌木林引起的草本成分和土壤N的预处理空间异质性影响了草本植物生产的后处理模式。在第2年中，年度草料意外地替代了PGR，这表明在某些条件下，进行刷子控制后的草料生产可能会明显偏离预测模型。