This spring’s stirring art event was the arrival of a West Coast organized survey of Karel Appel’s painting, 1950 to 1960, at the Art Center in La Jolla. San Diegans got a good look at the Dutchman’s turn to Tachism, his veering from static shapes and smooth surfaces to savage entanglements and a haptic troweling on of pigments. Evolution? Rather, perhaps, Appel is first driving color, his strength, and spatial organization, his desire, to a making or breaking point to find out about his own substance. — At the same time, the Center’s one-man show gallery featured Kenneth Callahan’s esoteric