Effects of agricultural management regimes on rotating cropland ecosystem respiration and its components in Southeast China

Investigating ecosystem, soil and aboveground respiration under different agricultural management regimes (i.e., fertilization, crop types and plowing practices) is critical for better understanding the processes of agricultural carbon cycles. The effects of agricultural management regimes on ecosystem respiration and its soil and aboveground respiration components have not been well identified. We performed a field experiment to measure ecosystem and soil respiration under different management regimes. Air temperature, soil temperature, soil moisture, crop growth characteristics [aboveground biomass (AB), leaf biomass (LB), leaf area index (LAI), specific leaf area (SLA), plant height (PH)] and crop productivity indexes [i.e., yield and biomass of a thousand seeds (BTS)] were also measured. The WrP4 treatment, where nitrogen was applied as chemical fertilizer and straw, had significantly (P < 0.05) higher seasonal cumulative ecosystem respiration (SCER) than the treatments where only chemical nitrogen was applied. Rice paddies had significantly (P < 0.05) lower SCER and seasonal cumulative soil respiration (SCSR) than upland plots during the 2003 summer growing season. No-till treatment significantly (P < 0.05) increased the SCER compared with plowing treatment. Plowing practices had different effects on the SCSR in the different growing seasons. The highest annual ecosystem respiration during the 2002‒2003 and 2003‒2004 rotation years was higher than that in previous studies that used the eddy covariance (EC) technique in croplands. The percentage of soil to ecosystem respiration varied from 31% to 81% across treatments. The SCER across treatments during the winter wheat growing seasons was significantly (P < 0.05) correlated with temperature, maximum aboveground biomass (MAB), maximum leaf biomass (MLB), maximum specific leaf area (MSLA) and BTS. Seasonal variations in ecosystem and soil respiration could be modelled by temperature, moisture, AB, LAI and PH. Moreover, the aboveground respiration coefficient decreased with increasing LAI and PH in the winter wheat, maize and rice plots.