Woody plant encroachment typically limits the forage productivity of managed rangelands and alters a panoply of semiarid ecosystem processes and services. Intervention strategies to reduce woody plant abundance, collectively termed “brush management”, often lack observations to quantify and interpret changes in ecosystem processes. Furthermore, comparative studies between treated and untreated areas should account for heterogeneity since plant composition, microclimate, topoedaphic factors, and historical land use can substantially vary over short distances in drylands. Here, we quantify ecosystem responses to brush management after a single aerial herbicide application on an 18 hectare shrub-encroached grassland (savanna) in southern Arizona, USA. We conducted a pre- and post-treatment comparison of a flux tower site in the treated area with that of a tower in a nearby control site. The comparison, spanning a seven year period, included: (1) ground, airborne, and satellite-based measurements of vegetation structure, and (2) eddy covariance measurements. The herbicide treatment defoliated the dominant shrub (velvet mesquite, Prosopis velutina) and led to a temporary reduction in summer greening, but full foliar recovery occurred within two years. Contrary to expectations, perennial grass cover decreased and bare soil cover increased on the treated site. Relative amounts of evapotranspiration were reduced, while carbon uptake increased during the 2 year post-treatment period at the treated site due to a higher water use efficiency in the following spring. During mesquite recovery, carbon uptake was enhanced by higher gross primary productivity and accompanied by a decrease in ecosystem respiration relative to the untreated site. Mesquite recovery was facilitated by access to deep soil water, carbohydrate reserves in rooting systems, and a lower competition from reduced perennial grass cover.

木本植物的侵占通常会限制管理牧场的草料生产力，并改变一整套半干旱生态系统过程和服务。减少木本植物丰度的干预策略，统称为“灌木管理”，通常缺乏量化和解释生态系统过程变化的观察。此外，处理过和未处理过的地区之间的比较研究应该考虑到异质性，因为植物组成、小气候、地形因素和历史土地利用在干旱地区的短距离内可能会有很大差异。在这里，我们量化了在美国亚利桑那州南部 18 公顷被灌木侵占的草原（稀树草原）上施用单次空中除草剂后生态系统对灌木管理的反应。我们对处理区域的助焊剂塔站点与附近控制站点的塔进行了预处理和后处理比较。跨越七年的比较包括：(1) 地面、空中和基于卫星的植被结构测量，以及 (2) 涡度协方差测量。除草剂处理使主要灌木（天鹅绒豆科植物、Prosopis velutina）并导致夏季绿化暂时减少，但在两年内叶面完全恢复。与预期相反，在处理过的地点，多年生草覆盖减少，裸土覆盖增加。蒸散的相对量减少了，而在处理地点的 2 年后期处理期间，由于次年春天的用水效率更高，碳吸收量增加。在豆科灌木恢复期间，与未处理地点相比，较高的总初级生产力增加了碳吸收，并伴随着生态系统呼吸的减少。获得深层土壤水、根系中的碳水化合物储备以及多年生草覆盖减少带来的较低竞争促进了豆科灌木的恢复。