The abundances of soil viruses and bacteria in a 7-year field experiment which addresses the long-term ecosystem consequences of mowing, nutrient addition, water addition, and temperature elevation in a temperate steppe in northern China are reported here. The estimated viral and bacterial abundances in this field were 2*10~8 and 2*10~7/g dry soil, respectively. The viral and bacterial abundances were not altered by mowing or nitrogen/phosphorus addition. Water addition and temperature elevation increased significantly bacterial abundance (by 58% and 31%, respectively), with no significant changes in viral abundance, which implies negative direct effects of these two environmental factors on viral survival or growth. These results suggest that bacterial growth in this soil may have been limited by environmental conditions such as moisture content and temperature, but not by resource availability. We also discussed the role viruses may play in the feedback between climate warming and microbial responses.