Lande R
Department of Biology, University of Chicago, 60637, Chicago, IL, USA.
Oecologia. 1988 May;75(4):601-607. doi: 10.1007/BF00776426.
Calassical demographic methods applied to life history data on the northern spotted owl yield and estimate of the annual geometric rate of increase for the population of λ=0.96±0.03, which is not significantly different from that for a stable population (λ=1.00). Sensitivity analysis indicates that adult annual survivorship has by far the largest influence on λ, followed by the probability that juveniles survive dispersal, and the adult annual fecundity. Substantial temporal fluctuations in demographic parameters have little effect on the long-run growth rate of the population because of the long adult life expectancy. A model of dispersal and territory occupancy that assumes demographic equilibrium is evaluated using data on the amount of old forest habitat remaining in the Pacific Northwest and the current occupancy of this habitat by northern spotted owls. This model is employed to predict the effect of future habitat loss and fragmentation on the population, implying that extinction will result if the old forest is reduced to less than a proportion 0.21±0.02 of the total area in a large region. The estimated minimum habitat requirement for the population is greater than that allowed in management plants by the USDA Forest Service.
将经典人口统计学方法应用于北方斑点鸮的生活史数据，得出该种群年几何增长率的估计值为λ = 0.96±0.03，这与稳定种群的增长率（λ = 1.00）没有显著差异。敏感性分析表明，成年个体的年存活率对λ的影响最大，其次是幼体在扩散过程中的存活概率以及成年个体的年繁殖力。由于成年个体预期寿命较长，人口统计学参数的大幅时间波动对种群的长期增长率影响较小。利用太平洋西北地区剩余老龄森林栖息地面积以及北方斑点鸮目前对该栖息地的占据情况数据，评估了一个假设人口统计平衡的扩散和领地占据模型。该模型用于预测未来栖息地丧失和破碎化对种群的影响，这意味着如果在一个大区域内老龄森林面积减少到总面积的比例低于0.21±0.02，将会导致物种灭绝。该种群估计的最小栖息地需求大于美国农业部林业局管理计划所允许的面积。
