|DOLD, CHRISTIAN - Orise Fellow|
|BUYUKCANGAZ, HAKAN - Uludag University|
|RONDINELLI, WESLEY - Texas A&M University|
|Sauer, Thomas - Tom|
Submitted to: Agriculture Forest Meteorology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/17/2016
Publication Date: 7/14/2016
Publication URL: https://handle.nal.usda.gov/10113/5638462
Citation: Dold, C., Buyukcangaz, H., Rondinelli, W., Prueger, J.H., Sauer, T.J., Hatfield, J.L. 2016. Long-term carbon uptake of agro-ecosystems in the Midwest. Agriculture Forest Meteorology. 232:128-140. doi: 10.1016/j.agrformet.2016.07.012.
Interpretive Summary: The Midwest region is one of the most important crop production areas for corn and soybean, but also comprises remnants of original tallgrass prairie vegetation. Predictions assume a negative impact of climate change on the region, either by the abundance or the lack of precipitation or increasing temperatures. In this study, corn, soybean and tallgrass prairie sites were investigated in central Iowa from 2006 – 2015. This period of time had contrasting weather conditions. The amount of carbon stored and assimilated were highest in corn and lowest in soybean, related to the vegetation’s efficiency to use water and radiation for carbon assimilation. Tallgrass prairie vegetation assimilated and stored more carbon than a soybean agro-ecosystem. The corn and soybean sites showed higher heterotrophic respiration of carbon than prairie vegetation during the off season. However, corn assimilated and stored the highest amounts of carbon during the growing season, which ameliorated the annual carbon balance. Air temperature increased the amount and efficiency of carbon assimilation. Carbon uptake in corn and soybean was negatively affected by excessive precipitation, probably due to water-logged soil conditions. Both individual analyses suggest that carbon assimilation of corn and soybeans increases in dry-warm years and decreases in wet-cold years. The carbon assimilation of tallgrass prairie increased with precipitation and air temperature, suggesting that warm-wet years ameliorate carbon assimilation and dry-cold years have adverse effects on carbon uptake. Agro-ecosystems in the Midwest are affected differently by extreme weather conditions which need to be considered for developing sustainable adaptation strategies in response to future climate variability impacts.
Technical Abstract: The Midwest is one of the most important production areas for corn and soybean worldwide, but also comprises remnants of natural tallgrass prairie vegetation. Future predictions suggest that corn (Zea mays L.) and soybean (Glycine max (L.) Merr.) production in the Midwest may be limited by precipitation and temperature due to climate change. Cross-biome long-term studies in situ are needed to understand carbon assimilation and impact of climate change on the entire region. In this study, we investigated the differences of gross primary production (GPP) and net ecosystem production (NEP) among typical (agro-) ecosystems of corn, soybean and tallgrass prairie from eddy flux stations from 2006 – 2015 under contrasting weather conditions. Corn had the highest annual GPP and NEP with 1321 and 328 g C m-2 yr-1, while soybean had significantly lower GPP and NEP with 640 and -39 g C m-2 yr-1, respectively. Corn and soybean NEP was linear related (p < 0.05) to leaf area index (LAI), height or phenological stage, confirming the strong link between plant growth and ecosystem carbon balance. Tallgrass prairie had average values of GPP and NEP of 928 and 50 g C m-2 yr-1 which were significantly lower than corn, but significantly higher than soybean. Probably the long fallow period on cropland, which enhanced heterotrophic respiration, and the low carbon assimilation of soybean reduced its overall carbon balance. Values for GPP and NEP were reflected in inherent water use efficiency (IWUE*) and light use efficiency (LUE) among the agroecosystems. In addition, IWUE*, LUE or GPP of crops and tallgrass prairie were linearly related (p < 0.05) to precipitation, volumetric soil water content (VWC) and maximum air temperature. Air temperature increased IWUE* in both, cropland and prairie vegetation. However, rainfall and VWC affected crops and prairie vegetation differently: while excessive rainfall and VWC reduced GPP or IWUE* in cropland, prairie vegetation GPP and LUE were adversely affected by reduced VWC or precipitation. Future measures of climate change adaption should consider the contrasting effects of precipitation and VWC among the different agro-ecosystems in the Midwestern USA.