Soil respiration and plant growth across a chronosequence of tallgrass prairie reconstructions

An understanding of changes in soil respiration (Rs) and plant growth in tallgrass prairies planted into formerly cultivated land is critical if we are to predict the effects of grassland reconstructions on belowground carbon cycling. In addition, predicting changes in the ecosystem carbon balance in grassland reconstructions will require identifying the climatic and biological controls on Rs across a landscape of cultivated and reconstructed grassland ecosystems. This study used a 12 yr chronosequence of tallgrass prairie reconstructions in central Iowa, including a no-till soybean field (age 0), to quantify the relationship between tallgrass prairie age, R s, root biomass, root ingrowth, and aboveground production. We also assessed the strength and interaction of soil temperature and soil moisture in predictions of Rs across the chronosequence. Linear regressions showed a significant increase in standing root biomass carbon (R2 = 0.89) and growing season Rs (R2= 0.83) with prairie reconstruction age while changes in aboveground production and root ingrowth were less predictable. Growing season (gs) Rs represented the largest carbon flux among prairie ages, ranging from 624 g C m-2 gs -1 in the soybean cropping system to 939 g C m-2 gs -1 in the oldest reconstruction (age 12), and was positively correlated with changes in root biomass. Among all tallgrass prairie reconstructions there was a strong, positive relationship between soil temperature and R s (R2 = 0.80 to R2 = 0.91) while the effect of soil moisture was greatest for the youngest prairie (age 4). Soil temperature was less correlated with Rs in the no-till soybean field (R 2 = 0.40) and the inclusion of soil moisture added limited additional predictive power (R2 = 0.48). Our findings indicate that an increase in cumulative Rs with prairie reconstruction age was related to the interaction of soil temperature and the accumulation of root biomass with young grassland development.