The temporal and spatial variation of soil respiration in pepper ( Capsicum annuum L.), eggplant (Solanum melongena L.) and maize (Zea mays L.) agro-ecosystems in Northwest of China

Soil respiration is a crucial factor in estimating the carbon budget accurately. In order to explore the temporal and the spatial variation of soil respiration in different agro-ecosystems, soil respiration and environmental factors were measured in pepper (Capsicum annuum L.), eggplant ( Solanum melongena L.) and maize ( Zea mays L.) ecosystems during the growing season from June to September in 2009. The pronounced seasonal and diurnal variations of soil respiration behaved similarly in the three ecosystems. The soil respiration reached a seasonal peak in July and a seasonal trough in September. The diurnal maximum values appeared between 1300h and 1500h, and the minimum values were between 0300h and 0500h. The seasonal and diurnal variations were significantly affected by soil temperature (Q 10 value from 1.32 to 2.71) and air temperature (Q 10 value from 1.25 to 2.03), but not significantly to soil moisture and air relative humidity in the three ecosystems. Soil respiration was measured near the plant, between plants in the rows (inter-plants) and between rows (inter-rows). The results showed a significant tendency of soil respiration near the plant > inter plants > inter rows in the maize ecosystem, but not in pepper and eggplant ecosystems, indicating spatial variation and vegetation type are needed to be considered when estimating carbon emissions from soil respiration.