A micrometeorological flux perspective on brush management in a shrub-encroached Sonoran Desert grassland

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