川西地区岷江柏种群生命表与生存分析

岷江柏 (CupressuschengianaS .Y .Hu)是国家II级保护植物 ,处于渐危状态 ,由于缺乏种群结构的研究限制了对该种的全面认识和有效保护。本文调查分析了岷江柏种群的年龄结构 ,编制了岷江柏种群的特定时间生命表 ,绘制了种群的存活曲线、死亡率曲线和消失率曲线 ,并用 4个生存函数对该种群进行了生存分析。结果表明 ,川西地区岷江柏种群处于中龄林阶段 ,种群存活曲线属Deevey III型 ,年龄结构呈增长型 ,死亡率曲线与消失率曲线变化趋势基本一致。在这一发育过程中有两个死亡高峰 ,一个出现在幼苗向幼树的过渡期(5～ 15a) ,环境胁迫是幼苗高死亡率的关键 ,另一个出现在从中龄向老龄过渡的阶段 (130～ 2 30a) ,环境制约以及人为砍伐是高死亡率的根本原因。种群生存分析表明 ,岷江柏种群累计死亡率单调增加 ,生存率单调下降 ,130年以后种群的累计死亡率均超过 95 % ,生存率都不足 5 % ,危险率超过了生存率 ;种群发育过程总体表现为前期增长 ,中期稳定 ,后期衰退。对大小结构与年龄结构的对比分析表明 ,目前广泛采用的大小结构代替年龄结构的分析方法对岷江柏这样的长寿慢生树种误差较大。

Life Table and Survival Analysis of Cupressus chengiana Population in the Western of Sichuan,China

Cupressus chengiana S.Y.Hu,which is on the verge of extinction,is the important protected plant of China.There was limited understanding and protection of this population due to lack of comprehensive investigation.In this paper,age structure of Cupressus chengiana was assayed and the specific life table was drawn.In addition,the curve of mortality rate,hazard rate and survival rate were constructed.The survival situation was estimated by the four survival functions.Cupressus chengiana population in the west Sichuan Province was in the middle-aged phase,and its survival curve can be described by Deevey-III.The population takes on an increasing tendency in its age structure and the mortality ratio curve showed the similar dynamics to hazard rate curve.The population had 2 distinct peaks of mortality,5?a to 15?a and 130?a to 200?a,respectively.It was shown that the two mortality peaks were due to the severe environmental damage,sterile land and human disturbance without restraint.The population mortality rate is increasing all along,and survival rate is decreasing all the time.Its mortality rate will exceed 95% and survival rate will decrease to below 5% after 130 years by our calculation.It is obviously that the hazard rate surpass survival rate.Generally,the population grows up dramatically in the early age,and then goes into a stable middle age,followed by a declined old age.All the results obtained in the present study showed that survival functions and age structure analysis elucidate the dynamics of Cupressus chengiana population successfully.It also was convinced that age structure analysis is much more reasonable than the size class method used widely at present.