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ARS Home » Plains Area » Las Cruces, New Mexico » Range Management Research » Research » Publications at this Location » Publication #409102

Research Project: Science and Technologies for the Sustainable Management of Western Rangeland Systems

Location: Range Management Research

Title: Carbon implications for woody plant encroachment – The role of dryland plant phenology along a gradient of state change

item Browning, Dawn
item Alfieri, Joseph
item Prueger, John
item Denham, Sander
item BARNES, MALLORY - Indiana University
item Bestelmeyer, Brandon
item LEVI, MATT - University Of Georgia

Submitted to: American Geophysical Union
Publication Type: Abstract Only
Publication Acceptance Date: 9/1/2023
Publication Date: 12/11/2023
Citation: Browning, D.M., Alfieri, J.G., Prueger, J.H., Denham, S.O., Barnes, M.L., Bestelmeyer, B.T., Levi, M. 2023. Carbon implications for woody plant encroachment – The role of dryland plant phenology along a gradient of state change. American Geophysical Union. Abstract.

Interpretive Summary:

Technical Abstract: Globally drylands represent a highly variable and potentially important role in the carbon cycle. Heterogeneous geomorphology and soils coupled with dynamic vegetation states challenge efforts to quantify carbon pools and fluxes in spatially-extensive dryland ecosystems. The shift from perennial grasslands to increasingly fragmented shrub-dominated systems is documented in mesic to dryland systems worldwide. We quantified patterns in 2022 gross primary productivity (GPP) and ecosystem respiration at three sites at the Jornada Experimental Range in southern New Mexico across a 9-km gradient using the eddy covariance (EC) method. Sites range from a mesquite shrubland (DUNE) with bare inter-shrub spaces to perennial grassland (BOER) and a shrub-invaded grassland (NOVEL). While sites experience similar meteorological conditions (e.g., net radiation, air temperature, wind speed/direction), they differ in plant communities and soil stability. Our goal was to better understand processes driving carbon and water fluxes across a gradient of ecological state change. There were strong respiration pulses at the BOER site 1-2 days after rain. Cross-correlations between GPP and rainfall at daily, weekly, and monthly lags revealed lag times of 2-3 weeks at BOER, 1-2 weeks at DUNE, and 5 days to 1 week at NOVEL. Cumulative GPP values for DUNE and NOVEL (391.6 and 465.2 g C m2, respectively) were similar while GPP was slightly higher for BOER (529.0 g C m2). GPP at NOVEL reached peak values in August while BOER and DUNE reached peak GPP in September. GPP at the BOER site emerged between February and April, prior to the other two sites. In situ plant phenology observations from the co-located NEON JORN site identified GPP contributions from annual grasses and forbs. The NOVEL site demonstrated the shortest lag time between GPP and rainfall which explains reaching peak production earlier that was sustained through the monsoon season. These insights have ramifications for understanding the uncertainty vegetation state change can add to forecasts of productivity and estimates of carbon fluxes and pools in drylands.