TY - JOUR
T1 - A micrometeorological flux perspective on brush management in a shrub-encroached Sonoran Desert grassland
AU - Vivoni, Enrique R.
AU - Pérez-Ruiz, Eli R.
AU - Scott, Russell L.
AU - Naito, Adam T.
AU - Archer, Steven R.
AU - Biederman, Joel A.
AU - Templeton, Nicole P.
N1 - Funding Information:
We acknowledge funding from the U.S. Department of Agriculture ( 2015-67019-23314 ), U.S. Army Research Office ( 56059-EV-PCS ), the Department of Energy's Office of Science (for US-SRM operations) and Arizona Agricultural Experiment Station ( ARZT-1361610-H12-223 ). We thank Ross Bryant, Adam P. Schreiner-McGraw, and Cody A. Anderson for help with equipment maintenance and data collection. The USDA is an EEO employer. Datasets for US-SRM and US-SRS are available from the AmeriFlux network, which is funded by the U.S. Department of Energy's Office of Science. Undergraduates Alyiah Branz, Cameron Burleson, Victoria Friess, Ethan Finch, Alex Grant, Travis McElroy, Alaina Michaels, Kalyn Miller, Jesus Quinn, Courtney Pijanowski, Sarah Posner, Damian Radine, Emily Runnion, Carley Schwartz, Alyssa Sierra, Bridget Slomka, and Karen Wang provided field vegetation data collection support. Thoughtful comments and suggestions from two anonymous reviewers helped improve the manuscript. Data sets are available at: (1) US-SRM at http://ameriflux.lbl.gov/sites/siteinfo/US-SRM , and (2) US-SRS at http://ameriflux.lbl.gov/sites/siteinfo/US-SRS .
Publisher Copyright:
© 2021 Elsevier B.V.
PY - 2022/2/15
Y1 - 2022/2/15
N2 - 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.
AB - 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.
KW - Brush management
KW - Eddy covariance
KW - Micrometeorological fluxes
KW - Prosopis velutina
KW - Rangeland
KW - Woody plant encroachment
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U2 - 10.1016/j.agrformet.2021.108763
DO - 10.1016/j.agrformet.2021.108763
M3 - Article
AN - SCOPUS:85120668081
SN - 0168-1923
VL - 313
JO - Agricultural and Forest Meteorology
JF - Agricultural and Forest Meteorology
M1 - 108763
ER -