塔里木河干流中游胡杨种群特征与动态分析

通过样地调查和数据统计,编制胡杨种群静态生命表,绘制存活曲线、生存率曲线、累计死亡率曲线、种群死亡密度曲线和危险率曲线,分析种群数量特征。同时,结合种群动态量化方法及时间序列预测,分析种群数量动态变化。结果表明:胡杨种群年龄结构呈金字塔型,幼龄级所占比例较大;存活曲线接近Deevey C(凹)型,且动态指数大于0,表明胡杨种群结构合理,为增长型种群。4个函数曲线表明,胡杨种群前期幅度变化较大,后期趋于稳定。时间序列分析表明,由于丰富的后续资源,种群能够稳定生长。

Characteristic and Dynamics Analysis of Populus euphratica Populations at the Middle Reaches of the Tarim River

Desert Populus euphratica forests grow widely in the Tarim River Basin,an arid desert region. Survival and development of desert P. euphratica has great ecological benefits,economic returns and social effects. Since the 1960s,water and land resources have been overexploited in the upper reaches of the Tarim River,which has resulted in a large number of nonbearing trees and degeneration and even death of P. euphratica forests in large areas,and damaged directly the sustainable development of oasis agriculture and ecological balance. Based on field investigation and data analysis,in this paper,a static life table of P. euphratica populations is worked out,the curves of survival,survival rate,cumulative mortality rate,mortality density and risk rate of P. euphratica populations are charted,and the population dynamic trend is analyzed using time sequence analysis and flop index so as to reveal the population structure,quantitative dynamics,survival status and development trend of P. euphratica forests in the future,and also provide the theoretical basis for rationally utilizing the P. euphratica resources and conserving the dominant P. euphratica populations. The results show that the size structure of P. euphratica during the study period was in a positive pyramidal shape,and the proportion of young trees was high. The proportion of I-Ⅱ age class was up to 66.2%,indicating that there were abundant subsequent seedling resources to support the growth of P. euphratica populations at the middle reaches of the Tarim River. The survival curve of P. euphratica populations was DeeveyC-shaped (concave-shaped) at the middle reaches of the Tarim River. In addition,dynamic index was 47.72% and higher than O,indicating the structure of P. euphratica populations was good enough.Time sequence prediction models for the populations show that the number of aged P. euphratica trees will increase in the future,and P. euphratica populations will grow steadily because of the rich subsequent seedling resources.