Event Title

Evaluating the Seasonal Sensitivity of Soil Respiration to Rainfall and Snowmelt in Urban and coniferous ecosystems

Presenter Information

Kerri Russell
Zachary Aanderud

Location

USU Eccles Conference Center

Event Website

http://water.usu.edu

Start Date

4-5-2016 5:36 PM

End Date

4-5-2016 5:39 PM

Description

Almost 10% of atmospheric CO2 passes through soil on a yearly basis and this store of mineralizable C (2,344 Pg) exceeds what is found in the atmosphere as CO2 (750 Pg) and vegetation (560 Pg) combined. While most of the C influx to terrestrial ecosystems can be attributed to photosynthesis during the spring and summer months, processes governing the efflux of C, such as mineralization processes and soil respiration, occur throughout the year. Winter respiration can account for more than 50% of the C sequestered by higher plants during the growing season. Summer pulses of CO2 from rewetted soils may elevate nighttime net ecosystem exchange up to 95%, resulting in a significant net carbon loss from ecosystems, and contribute upwards of 25% of an ecosystem's terrestrial carbon budget. However, summer and winter respiration is highly variable and may be regulated by fluctuations in environmental variables that covary with the timing of rainfall and snowmelt. Nutrient levels, such as N deposition and urban and agricultural runoff from human activities, may also enhance soil respiration dynamics. To better understand intra- and inter-annual variation and urbanizations effect on CO2 efflux, we are evaluating the sensitivity of soil respiration to rainfall- and snowpack-induced fluctuations in temperature and moisture in three coniferous forests and urban ecosystems. We are measuring soil respiration, moisture, and temperature with Vaisala CO2 GMP220-series probes at two depths (5 and 20 cm) to calculate flux rates and Acclima SDI-12 Interface sensors to measure moisture and temperature. Besides evaluating soil respiration sensitivity (i.e., CO2 evolved per unit change in moisture or temperature), we are evaluating the legacy effects of natural rainfall and snowfall on the structure of soil microbial communities using target metagenomics of 16s rDNA. Results so far from one montane and urban site in the Provo River watershed suggest that soil respiration is higher in soils beneath snow in montane systems than snow-bare urban soils. Winter diel fluctuations in CO2 are more pronounced in montane systems (spanning as much as 200 ppm) potentially due to soils freezing at night and impeding microbial activity. CO2 efflux following snowmelt in urban systems is beginning to increase, with the largest fluctuations in CO2 occurring in deeper soils. We will continue our investigation for the next two years and initiate our modeling efforts once we have logged an entire season of data. We expect our findings will help predict soil respiration links to diel, seasonal, and urbanization effects.

Comments

A poster by Kerri Russell, who is with Brigham Young University, Plant and Wildlife Sciences

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Apr 5th, 5:36 PM Apr 5th, 5:39 PM

Evaluating the Seasonal Sensitivity of Soil Respiration to Rainfall and Snowmelt in Urban and coniferous ecosystems

USU Eccles Conference Center

Almost 10% of atmospheric CO2 passes through soil on a yearly basis and this store of mineralizable C (2,344 Pg) exceeds what is found in the atmosphere as CO2 (750 Pg) and vegetation (560 Pg) combined. While most of the C influx to terrestrial ecosystems can be attributed to photosynthesis during the spring and summer months, processes governing the efflux of C, such as mineralization processes and soil respiration, occur throughout the year. Winter respiration can account for more than 50% of the C sequestered by higher plants during the growing season. Summer pulses of CO2 from rewetted soils may elevate nighttime net ecosystem exchange up to 95%, resulting in a significant net carbon loss from ecosystems, and contribute upwards of 25% of an ecosystem's terrestrial carbon budget. However, summer and winter respiration is highly variable and may be regulated by fluctuations in environmental variables that covary with the timing of rainfall and snowmelt. Nutrient levels, such as N deposition and urban and agricultural runoff from human activities, may also enhance soil respiration dynamics. To better understand intra- and inter-annual variation and urbanizations effect on CO2 efflux, we are evaluating the sensitivity of soil respiration to rainfall- and snowpack-induced fluctuations in temperature and moisture in three coniferous forests and urban ecosystems. We are measuring soil respiration, moisture, and temperature with Vaisala CO2 GMP220-series probes at two depths (5 and 20 cm) to calculate flux rates and Acclima SDI-12 Interface sensors to measure moisture and temperature. Besides evaluating soil respiration sensitivity (i.e., CO2 evolved per unit change in moisture or temperature), we are evaluating the legacy effects of natural rainfall and snowfall on the structure of soil microbial communities using target metagenomics of 16s rDNA. Results so far from one montane and urban site in the Provo River watershed suggest that soil respiration is higher in soils beneath snow in montane systems than snow-bare urban soils. Winter diel fluctuations in CO2 are more pronounced in montane systems (spanning as much as 200 ppm) potentially due to soils freezing at night and impeding microbial activity. CO2 efflux following snowmelt in urban systems is beginning to increase, with the largest fluctuations in CO2 occurring in deeper soils. We will continue our investigation for the next two years and initiate our modeling efforts once we have logged an entire season of data. We expect our findings will help predict soil respiration links to diel, seasonal, and urbanization effects.

https://digitalcommons.usu.edu/runoff/2016/2016Posters/23