Effects of an increase in summer precipitation on leaf, soil, and ecosystem fluxes of CO₂ and H₂O in a sotol grassland in Big Bend National Park, Texas

• Published in: Oecologia Vol. 151; no. 4; pp. 704 - 718
• Main Authors: Patrick, Lisa, Cable, Jessica, Potts, Daniel, Ignace, Danielle, Barron-Gafford, Greg, Griffith, Alden, Alpert, Holly, Van Gestel, Natasja, Robertson, Traesha, Huxman, Travis E, Zak, John, Loik, Michael E, Tissue, David
• Format: Journal Article
• Language: English
• Published: Berlin Berlin/Heidelberg : Springer-Verlag 01-04-2007; Springer-Verlag; Springer; Springer Nature B.V
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Asparagaceae - metabolism; Biological and medical sciences; Biosphere; Bouteloua curtipendula; carbon; Carbon dioxide; Carbon Dioxide - metabolism; Carbon fixation; carbon sinks; Chihuahuan Desert; Climate models; Climatology. Bioclimatology. Climate change; Dasylirion leiophyllum; Desert soils; Deserts; Earth, ocean, space; Ecosystem; Ecosystem fluxes; Ecosystems; Evaporation; Evapotranspiration; Exact sciences and technology; External geophysics; Fundamental and applied biological sciences. Psychology; General aspects; Global Change and Conservation Ecology; Global climate; Grasses; Grasslands; Leaves; Meteorology; Moisture content; National parks; Photosynthesis; Plant Leaves - metabolism; Plants; Poaceae - metabolism; Precipitation; Precipitation manipulation; Rain; Respiration; Seasons; Shrubs; Soil - analysis; Soil ecology; soil respiration; Soil water; Summer; Synecology; Terrestrial ecosystems; Texas; Transpiration; Water - metabolism; Texas; Chihuahuan Desert; United States; Monocotyledones; Carbon dioxide; Chihuahua Mexico; Precipitation manipulation; North America; precipitation; climate modification; grasslands; Dasylirion leiophyllum; Gramineae; Angiospermae; flux; Bouteloua; soils; Ecosystem fluxes; atmospheric precipitation; Big Bend National Park; Increase; Plant leaf; water; deserts; global change; ecosystems; Bouteloua curtipendula· Chihuahuan Desert; Spermatophyta
• ISSN: 0029-8549; 1432-1939
• DOI: 10.1007/s00442-006-0621-y

Global climate models predict that in the next century precipitation in desert regions of the USA will increase, which is anticipated to affect biosphere/atmosphere exchanges of both CO₂ and H₂O. In a sotol grassland ecosystem in the Chihuahuan Desert at Big Bend National Park, we measured the response of leaf-level fluxes of CO₂ and H₂O 1 day before and up to 7 days after three supplemental precipitation pulses in the summer (June, July, and August 2004). In addition, the responses of leaf, soil, and ecosystem fluxes of CO₂ and H₂O to these precipitation pulses were also evaluated in September, 1 month after the final seasonal supplemental watering event. We found that plant carbon fixation responded positively to supplemental precipitation throughout the summer. Both shrubs and grasses in watered plots had increased rates of photosynthesis following pulses in June and July. In September, only grasses in watered plots had higher rates of photosynthesis than plants in the control plots. Soil respiration decreased in supplementally watered plots at the end of the summer. Due to these increased rates of photosynthesis in grasses and decreased rates of daytime soil respiration, watered ecosystems were a sink for carbon in September, assimilating on average 31 mmol CO₂ m-² s-¹ ground area day-¹. As a result of a 25% increase in summer precipitation, watered plots fixed eightfold more CO₂ during a 24-h period than control plots. In June and July, there were greater rates of transpiration for both grasses and shrubs in the watered plots. In September, similar rates of transpiration and soil water evaporation led to no observed treatment differences in ecosystem evapotranspiration, even though grasses transpired significantly more than shrubs. In summary, greater amounts of summer precipitation may lead to short-term increased carbon uptake by this sotol grassland ecosystem.