橡胶人工林生态系统养分循环研究I．无性系PR107氮素体循环

通过对儋州地区，林分结构相近、立地条件相似、抚管措施相同、林龄不同（2a～28a）的橡胶无性系PR107的生物量和分配格局、生产力、氮素积累与固定、氮素归还、凋落物及氮素利用效率进行比较研究，发现它们之间存在较明显的差别，并表现出不同的养分生物学特性。试验结果表明：（1）橡胶树不同器官氮素含量高低顺序为：叶>树枝>树根>树皮>树干>胶乳，而积累量和分配格局则为：树干>树枝>树叶>树皮>树根>胶乳。在橡胶树28a生长周期中，养分积累总量可达5639.12kg/hm2，其中氮素约为1606.13kg/hm2，占28.48%。（2）随着树龄的增长，橡胶树枯落物量和由此向土壤归还的氮素总量也逐年增加，氮素归还率也逐年增加。据测定，不同树龄橡胶树每年枯落物总量约为0.295～11.08t/hm2,由枯落物向土壤归还的养分总量达13.44～431.4kg/hm2.a，其中氮约为5.28～162.62kg/hm2。（3）橡胶树体对氮素的利用效率基本上随着树龄的增加逐渐降低，各器官对氮素的利用效率大小顺序为：树干>树皮>胶乳>树枝>树根>树叶。

Study on nutrient cycle of ecosystem in rubber plantation:I. Nitrogen cycle in Clone PR107

The biomass allocation, productivity, nitrogen cycle of clone PR107 in XiLian, XiQing, and CATAS farm state, DanZhou, Hainan province, were compared study by selecting the similar stands in stand structure, site and management practices, but different stand ages, from 2 to 28-year-old. The results showed that the 2a to 28a rubber trees were significantly different in biomass allocation, productivity allocation, nitrogen accumulation, fallitter, nitrogen return and nitrogen use efficiency (NUE). The rubber trees of different ages had showed different nutrient biological traits. (i) The nitogen amount in different organs was relative to age of trees and season. The order of nitrogen percentage in organs’ was: leaf>branch>root>bark>trunk>latex. However, it’s accumulation and allocation was: trunk>branch>leaf>bark>root>latex. Nitrogen accumulation in 28yr growth period of PR107 was 5639.12 kg/hm2, in which nitrogen was 1606.13 kg/hm2, and 28.84%. (ii) Along with age growth of rubber tree, the total fallitter, nitrogen return amount to soil and return ratio of nitrogen from fallitter were increased, of which 0.295～11.08t/hm2 of fallitter and 13.44~431.4kg/hm2 of nutrition be returned by fallitter per one year, including 5.28～162.62kg/hm2 of nitrogen. (iii) The NUE was varied among different age trees and organs, which was higher at younger trees, and then lower gradually along with age growth. The order of NUE in different organs was: trunk>bark>latex>branch>root>leaf. Keywords: rubber tree, clone PR107, nutrient cycle, nitrogen