沼泽交错带白桦—长白落叶松优势种群的年龄结构及其动态

Age structure and population dynamics of dominant species in a Betula platyphylla—Larix olgensis forest on swamp ecotone

关键词:  白桦, 长白落叶松, 辽东桤木, 种群动态, 生命表, 生存分析, 谱分析, 时间序列预测, 长白山

Key words:  Betula platyphylla, Larix olgensis, Alnus hirsuta, population dynamics, life table, survival analysis, spectral analysis, time sequence analysis, Changbai Mountain

摘要:

采用径级结构替代年龄结构与建立种群年龄结构模型相结合的方法,研究沼泽交错带白桦—长白落叶松优势种群的年龄结构特征。结果表明:白桦、长白落叶松和辽东桤木种群的年龄结构呈纺锤型,龄级—个体数间的关系可用Lognormal函数表征; 种群动态量化指数V'_pi为辽东桤木(9.57%)>白桦(4.02%)>长白落叶松(1.83%),均趋近于0,说明种群处于稳定型向衰退型过渡阶段; 白桦、长白落叶松及辽东桤木种群幼龄个体严重不足,白桦和辽东桤木种群的存活曲线趋于Odum-B₃型,而长白落叶松种群趋于Deevey-I型。白桦、长白落叶松及辽东桤木种群具有前期增长、中后期衰退的特征; 白桦、长白落叶松和辽东桤木种群数量受基波影响显著,种群整个生活史阶段未显现小周期波动,种群发展较稳定; 随着时间的推移,在未来2、4和6个龄级后,白桦、长白落叶松和辽东桤木种群老龄个体数均有增加,但由于更新幼苗个体稀少,未来必然呈衰退趋势。森林—沼泽交错带的白桦、长白落叶松及辽东桤木种群对外界环境变化有强烈的敏感性和脆弱性,人类活动扰动会影响其发育与演变,从而提高了森林—沼泽交错带地区沼泽化的风险。因此,应减少人类活动对森林—沼泽交错带的干扰,加强对这一地区植被群落的保护与管理。

Abstract:

In order to reveal the trend of population development and provide the basis for swamp ecotone population's recovery and management, we studied dominate species in a Betula platyphylla—Larix olgensis forest on swamp ecotone, elaborated its current situation and quantity dynamic, by adopting space as substitute for time, and taking trunk size structure in place of age structure, study on age structure of the dominate species in a Betula platyphylla—Larix olgensis forest. Based on the life table of population and the theory of survival analysis, we worked out the life table of Betula platyphylla, Larix olgensis and Alnus hirsuta population and estimated the survival curve, mortality curve, as well as other important parameters. Population dynamics were analyzed by using dynamic quantitative index, spectral analysis and time-sequence model. The results showed that the age structure of Betula platyphylla and Larix olgensis population were spindle type, Lognormal function can represent the relationship between age and number of individuals. Dynamic index V'_pi with the order of Alnus hirsuta(9.57%)> Betula platyphylla(4.02%)> Larix olgensis(1.83%), the populations tend to be stable, and the populations enter the transition phase of recession. The mortality was high in early stage, the number of saplings was gravely insufficient. The survival curve of the Betula platyphylla and Alnus hirsuta population indicated that it approached a Odum-B₃ type, however, the survival curve of the Larix olgensis revealed that it approached a Deevey-I type; Four survival functions curves suggested that the Betula platyphylla, Larix olgensis and Alnus hirsuta population would have an early increase then recession in mid to late-stage. Spectral analysis of the population demonstrated that the first harmonic have a significant on the dynamic of population,there was not a marked periodic fluctuation in the progress of natural regeneration of Betula platyphylla, Larix olgensis and Alnus hirsuta, the development of whole population trend to stability; The time sequence model predicted that the number of old age individuals would ascent in the coming two, four and six age classes in Betula platyphylla, Larix olgensis and Alnus hirsuta populations, but the regeneration seedling was rare, so the population tend to degenerate are inevitable. Forest-swamp ecotone are more sensitive and vulnerable to environment change, humanactivities have a significant impact on the development and evolution of Betula platyphylla, Larix olgensis and Alnus hirsuta populations, which improve the risk of forest transition into swamp, therefore, we should minimize disturbance and strengthen the protection and management of vegetation communities on forest-swamp ecotone, so as to create favorable conditions for the succession of forest-swamp ecotone communities to forest.