Plant species richness in multiyear wet and dry periods in the Chihuahuan Desert

Authors: Peters, Debra; Savoy, Heather; Stillman, Debra; HUANG, HAITAO - New Mexico State University; HUDSON, AMY - Orise Fellow; SALA, OSVALDO - Arizona State University; VIVONI, ENRIQUE - Arizona State University

Submitted to: Climate
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/6/2021
Publication Date: 8/13/2021
Citation: Peters, D.C., Savoy, H.M., Stillman, D.S., Huang, H., Hudson, A.R., Sala, O.E., Vivoni, E.R. 2021. Plant Species Richness in Multiyear Wet and Dry Periods in the Chihuahuan Desert. Climate. 9(8):130. https://doi.org/10.3390/cli9080130.
DOI: https://doi.org/10.3390/cli9080130

Interpretive Summary: We examined the importance of multi-year periods of precipitation to patterns in species richness in grasslands and shrublands of the Chihuahuan Desert. Co-located precipitation and species richness data for 26 years from 12 locations at the USDA ARS Jornada Experimental Range were compared. Breakpoint analysis was used to identify the multi-year period, either dry, wet or average. We found five sequential peiods: AVG1 (1993-1999, mean=22 cm/yr), DRY1 (2000-2003, mean=18 cm/yr), WET (2004-2008, mean=30 cm/yr), DRY2 (2009-2012, mean=18 cm/yr), and AVG2 (2013-2018, 24 cm/yr). As expected, most species were found for most locations in the wet period. However, there were two other patterns in richness that were unrelated to precipitation amount: (1) AVG1 had more richness yet lower precipitation compared with AVG2, and (2) DRY2 had more species than DRY1 yet both periods had the same amount of precipitation. Our results show that precipitation characteristics of seasonality, storm depth, dry day interval, and wet and dry spells that correpond with species functional traits of photosyntheric pathway, rooting depth, and reponse of dominant species are important to richness patterns.

Technical Abstract: In drylands, most studies of extreme precipitation events examine impacts of single years, yet multiple year periods are expected to have larger effects on ecosystem dynamics. Our goal in this study was to determine the relationships between precipitation characteristics of wet or dry periods with patterns in species richness for grassland and shrubland ecosystems. Co-located daily precipitation and seasonal plant species richness data were obtained for 26 years (1993-2018) from 12 locations at a research site in the northern Chihuahuan Desert. Breakpoint analyses of water-year precipitation showed five sequential periods: AVG1 (1993-1999; mean=22 cm/y), DRY1 (2000-2003; mean=18 cm/y), WET (2004-2008; mean=30 cm/y), DRY2 (2009-2012; mean=18 cm/y), and AVG2 (2013-2018; mean=24 cm/y). For most locations, species richness was highest in the wet period. For the other period-location combinations, there was one of two patterns that were unrelated to total precipitation: (1) AVG1 had higher richness, yet lower precipitation compared with AVG2 or (2) DRY2 had more species than DRY1, yet both periods had the same amount of rainfall. Precipitation characteristics such as seasonality, storm depth, dry day interval, and wet and dry spells, drove changes in species richness that corresponded with photosynthetic pathways, root morphology, and impacts on dominant species. Understanding these relationships provides insights to species-level dynamics in drylands under a changing climate.