Many field experiments have been conducted to examine the effects of warming on terrestrial ecosystems. However, the impacts of the predicted warming on belowground ecosystem are not still clear. We conducted an in situ experimental warming at a cool temperate grassland to clarify the responses of belowground ecosystem to temperature increase.

This study was conducted at Zoysia japonica grassland in central Japan. We established control and warmed plots and soil temperature (2 cm in depth) in warmed plots was increased by about 1−2ºC using infrared heaters during the growing season of 2009−2011. Aboveground plant biomass was estimated using point-frame method. Soil samples were collected to examine some soil properties such as C and N contents. Microbial biomass was determined according to phospholipid fatty acid content.

Aboveground plant biomass was increased by experimental warming. While the warming tended to reduce soil organic matter content, it increased ammonium nitrate content. These results suggest that the warming would stimulate organic matter decomposition (mineralization). Soil microbial biomass was slightly decreased by the warming, probably due to decrease in soil moisture. Our observations suggest that the warming would affect the C and N cycle through the changes in rate of mineralization and size of pools.