NAU will receive $496,555 from the NSF for the three-year\nproject, with an additional $203,445 going to collaborators at the University\nof New Mexico.<\/p>\n\n\n\n
The study looks at two types of water loss\u2014evaporation, in\nwhich water moves directly from the soil to the atmosphere, and transpiration,\nwhen water is piped from the soil to the atmosphere by plants. Scientists have\nstruggled to make the effects of these processes distinct, coining the catchall\nterm \u201cevapotranspiration\u201d to describe water moving from Earth\u2019s soil into the\natmosphere.<\/p>\n\n\n\n
Up to now, that\u2019s worked. It doesn\u2019t anymore.<\/p>\n\n\n\n
\u201cWe\u2019re at the point now where we have to pick it apart,\u201d\nSamuels-Crow said. \u201cOur goal in this project is to understand what climate\ndrivers are behind these two really important processes that take water from\nthe soil and stick it into the atmosphere.\u201d<\/p>\n\n\n\n
She\u2019s joined in this research by co-PIs Kiona Ogle<\/strong>, also a SICCS professor; Marcy Litvak, a biology professor at the University of New Mexico; and John Bradford, a research scientist with the U.S. Geological Survey in Flagstaff. The team will collect data at six sites in New Mexico, from ecosystems that range from desert grasslands and shrublands to pinyon and juniper woodlands, Ponderosa pine forests and high-altitude mixed conifer forest. They picked these sites because they already have a decade of data about fluxes and climate conditions; Litvak has been measuring the flow of water, carbon dioxide and energy between the atmosphere and ecosystems in these sites since 2008.<\/p>\n\n\n\n The measuring process is a bit complicated, Samuels-Crow\nsaid. Using a machine that measures isotopes in water, which she and Ogle\nacquired through a Technology and Research Initiative Fund grant from the\nArizona Board of Regents, the team can determine what isotopes are present in\nthe soil water and in the water vapor in the atmosphere. They know that heavier\nisotopes of both hydrogen and oxygen (2H, 17O and 18O) evaporate more slowly\nthan lighter isotopes (1H and 16O). Thus, if you spilled water on the sidewalk\nand let half of it evaporate, what would be left in the puddle would have a\nhigher concentration of heavy isotopes, while the water vapor that evaporated\nfrom the puddle would have a higher concentration of lighter isotopes. The same\nholds true for water in the top layers of soil.<\/p>\n\n\n\n So that\u2019s evaporation. In transpiration, the plant is\ngetting water from its root source, which is likely much deeper in the\nground\u201412 inches vs. three inches, for example. Using an instrument that\nmeasures water vapor coming directly off the plant in real time likely will show\nan isotope range that is more in line with the isotopes found in water that\noccurs much deeper in the soil.<\/p>\n\n\n\n On top of that, some of the sites have instruments that\nmeasure water flow (\u201csap flow\u201d) in trees, which is a direct measurement of\ntranspiration. This data is difficult to apply to an entire ecosystem, but it\u2019s\none more dataset they can collect.<\/p>\n\n\n\n Once they have all of this disparate data, Ogle will use\nthem to create statistical models that attempt to break down the effects of\nevapotranspiration into evaporation and transpiration. It won\u2019t answer all the\nquestions, but it will introduce valuable new information into a critical\nconversation about the availability of water in an increasingly hot, dry\nclimate. <\/p>\n\n\n\n \u201cWe expect to show that history matters for understanding\nwater loss from these systems such that the amount of water lost from soils to\nthe atmosphere via transpiration will depend on the preceding environmental\nconditions that occurred days, weeks or months ago,\u201d Ogle said. \u201cThese \u2018lagged\neffects\u2019 are typically ignored by predictive models, yet they could be really\nimportant for predicting how water loss, and the water cycle in general, will\nchange in the future.\u201d<\/p>\n\n\n\n The USGS\u2019s Bradford can use these new datasets and models to\ncalibrate SOILWAT, a mechanistic model of soil water, to better separate\nevaporation and transpiration and to evaluate the potential importance of such\nlagged effects.<\/p>\n\n\n\n \u201cThose types of models go into water resource planning in\nthe Southwest,\u201d Samuels-Crow said. \u201cBy doing this, what we\u2019re hoping is to get\na better sense of these different drivers of evaporation and transpiration,\nwhen they\u2019re active, under what conditions they\u2019re active. For instance, if you\nincrease temperature, we can tell what changes about our water resources\nbecause we\u2019ll know how much less is getting down into shallow groundwater\nbecause the physical processes or evaporation has moved that water elsewhere.<\/p>\n\n\n\n \u201cIt\u2019s not going to radically change our understanding, but\nit is going to provide the SOILWAT with valuable information for its models, and\nwater managers use that tool in planning.\u201d<\/p>\n\n\n\n It\u2019s a small but important piece of the water management\npuzzle in this region but also globally.<\/p>\n\n\n\n \u201cWater is a critical resource in the Southwest, and\nunderstanding how the water cycle is impacted by plants, soils and climate is\nimportant to predicting changes in water availability,\u201d Ogle said. \u201cI think\nthat people of the Southwest generally appreciate their surroundings and access\nto public lands and diverse ecosystems. Our ecosystems may be threatened by\ncontinued climate change, and this research will contribute data and results\nthat are important to predicting how our ecosystems may change in the future\nand to helping identify those ecosystems or biomes that may be most vulnerable\nto such future changes.\u201d<\/p>\n\n\n\n![\"High-elevation](\"https:\/\/in.nau.edu\/news\/wordpresst\/uploads\/sites\/153\/wp-content\/uploads\/2019\/06\/Unknown-1-450x600.jpeg\")
![\"NAU](\"http:\/\/in.nau.edu\/news\/wordpresst\/uploads\/sites\/153\/wp-content\/uploads\/2018\/08\/NAU_primary-281_3514-1-e1536853679171.png\")
<\/figure>
Heidi Toth | NAU Communications
(928) 523-8737 | heidi.toth@nau.edu<\/a><\/p>\n<\/div><\/div>\n","protected":false},"excerpt":{"rendered":"