[Judging method of individual age and age structure of Stellera chamaejasme population in degraded steppe].
Based on the minute observation of branches morphology of root-crown of Stellera chamaejasme in Cleistogenes squarosa community and its growth characteristics, this paper studied the age structure of S. chamaejasme population, and an individual age judging method "the times of quasi-dichotomous branching plus two" was put forward for the first time. Remnant stubbles, branch trace, and annular trace on the root crown were regarded as important morphological features, and used to confirm the times of quasi-dichotomous branching. The results showed that the oldest individuals at three grazing succession stages (i.e., heavy grazing, over grazing and extreme grazing) were 15, 16 and 19 years old, respectively. Among all age classes, the numbers of eight years old individuals were the largest, and the age ratio was 18.71%, 24.20% and 19.06%, respectively, at the different succession stages. There were no one- and two-year old individuals at heavy grazing stage, and no one-year old individuals at the other two grazing stages. The age structures of the populations were "early declining types", and the survival curves were similar to protuberant type or Deevey I type. The numbers of old age individuals (thirteen years old and more) at the three succession stages accounted for 4.83%, 2.84% and 14.02%, respectively. The age structure of the population tended to aging with the increase of grazing intensity.
Xing
Fu
F
Institute of Grassland Science, Northeast Normal University, Changchun 130024, China. xingf@nenu.edu.cn
Gou
Jixun
J
Wei
Chunyan
C
D010946:Plants, Medicinal / Q000033:anatomy & histology / Q000254:growth & development; D010947:Plants, Toxic / Q000033:anatomy & histology / Q000254:growth & development; D006109:Poaceae / Q000254:growth & development*; D029645:Thymelaeaceae / Q000033:anatomy & histology* / Q000254:growth & development; D013997:Time Factors