Abstract: The term forest decline refers to a disease form premature progressive loss of vigor and health to death. Forest decline caused primarily by chronic stress or sequential results to the tree-non-organisms and organisms. Symptoms of decline include slow growth, sparse, undersized and/or chlorotic leaves, premature leaf margins, premature display of autumn color, and premature leaf drop. However, the trend of simplifying the caused factors are often observed. Currently, most of the researches focus on finding the main causes and relationship among the factors.