A preliminary investigation of population of Cycas panzhihuaensis in Panzhihua

摘要

This paper reports the preliminary results of an investigation for ten years on the populations of Cycas panzhihuaensis at Bagunanhe. The lowest point where the cycad grows is 150 m above Jinshajiang River, and the highest point where the cycad grows is 150 m below the top of the mountain. The most densely populated zone of this species ranges from 1700-2150 m in absolute vertical elevation where each individual cycad covers an average area of 2 sequare meters. In the most sparsely populated zone each individual cycad covers an area of 47 square meters. The highest cycad individual is 3.5 m high. The longest leaf is 2.3 m long, with 150 pairs of pinnae. The longest male cone is 90 cm long. The plant individuals which cone continually for three years, take 5% of the total plant of the population; the biggest female cone has a diameter of 40 cm. The number of megasporophyll in a female cone can reach 120. The female cone with complete pollination (artificial pollination) can set 10-360 seeds. The individual plant which can cone every year, takes 2-3% of the total cycads of the population. In the last part of this paper, the influences of human's activity and natural factors on the habits of Cycas panzhihuaensis are discussed.