Nutritional disturbances and declining armand pine in Southwestern China

Abstract

The 6000 ha of Armand Pine in the Wushan mountainous area East of Sichuang Province in southwestern China, have almost declined completely. The preliminary investigation in the area shows that the needle chlorosis (yellowing) of Armand Pine is a common symptom of forest decline in the mountainous region, and a significant increase of the symptom has been seen in the past decade.The SO² and rain pH data were collected from three monitoring sites in the area.Soil and needle analysis were carried out.The preliminary results indicate that yellowing was evident at all sites of lower soil pH and that soil nutrient status of Mg deficiencies were most notable on acid soils with base saturations at 3.2 to 7.5%. Magnesium, K, Zn (particularly Mg) contents of current needles were all deficient.Exchangeable Mg in the soil of the heavily damaged forest stand was lower than that of the well-growing forest. But the degree of yellowing does not rise along with the increase of A1 concentration. The preliminary investigation in the southwest indicates that the forest damage is associated with nutritional disturbances and the existence of Mg deficiency is reported as the most predominant agent in causing symptoms of yellowing foliage.