荒漠珍稀灌木半日花种群数量动态的谱分析

Spectral Analysis of Dynamics of Rare Eremophyte Helianthemum ordosicum Population

依据不同坡位的半日花(Helianthemum ordosicum)种群的野外样方调查数据,运用谱分析数学方法,对其种群数量动态变化进行了分析研究。结果表明:在以地径级差划分龄级的基础上,半日花种群天然更新过程的动态是通过半日花不同龄级的株数分布波动而表现的。不同坡位半日花种群的数量动态过程受基波影响最明显,并且波动还表现出明显的中、小周期。不同坡位种群均存在基本周期1/2的12～15mm地径增量的中等长度的周期波动,以及2.00～6.25mm地径增量的小周期波动。这种中、小周期波动与环境压力、种间竞争及自身生理特性等有关。由于不同坡位的生境条件不同,表现为从坡下部到坡上部,半日花种群数量变动的波动小周期(地径增量表型)逐渐缩短。人为干扰对不同坡位半日花种群动态的波动产生影响。半日花种群数量动态变化的这种周期性的波动可使半日花种群的自我稳定性得以维持与延续。

Based on plot survey data at different slope positions, the dynamics of Helianthemum ordosicum population were analyzed using the spectral analysis method. Results showed that the natural regeneration dynamics of H. ordosicum population were presented as fluctuation of the distribution of individuals by age classes determined from the ground diameter. The quantitative dynamics of H. ordosicum population at different slope positions were greatly affected by the base wave. The apparent midand small-scale periodic fluctuations also existed. The mid-scale periodic fluctuations were about half of the base waves in the 12 mm- 15 mm increment of ground diameter, and the small-scale periodic fluctuations were reflected in the 2.00 mm- 6.25 mm increment of ground diameter regardless of slope positions. The mid- and smallscale periodic fluctuations were related to the environment pressure, interspecific competition and the intrinsic physiological characteristics. Because of the different habitat conditions, the small-scale periodism in the increment of ground diameter decreased from the lower slope position to the upper slope position in H. ordosicum population. Human disturbance also affected the periodic fluctuations. The periodic fluctuations of the quantitative dynamics maintained and sustained the self-stability in H. ordosicum populations.