We report our experimental study on chemical patterns in a spatial open reactor using the Belousov-Zhabotinsky reaction. A phase diagram showing different regimes of spiral dynamics is presented. The focus of the study is on transitions leading to defect-mediated turbulence (spiral turbulence). Some new interesting phenomena are described, including a transition from one type of spiral turbulence to another type, and the re-entry from spiral turbulence into ordered spiral waves. We also try to characterize different states of turbulence using the hierarchical structure theory. (C) 2003 American Institute of Physics.