白龙江沙滩林场退化人工云杉林次生演替阶段优势种群结构特征

Dominant Population Structure in Secondary Succession Stage of Degraded Artificial Picea Asperata Forest of Shatan Forest Farm Located in Bailongjiang Forest Region,Gansu Province

为了解白龙江上游沙滩林场退化人工云杉林次生演替阶段的群落物种组成与生存现状,通过样地调查和数据统计,绘制优势种群结构图,编制静态生命表,拟合并分析存活曲线,运用数量化方法和时间序列模型分析种群动态,预测种群发展趋势,为该林区次生林的可持续经营提供理论依据。结果表明:次生林群落乔木层共有树种13种,人工云杉林大量死亡,红桦、糙皮桦和岷江冷杉的重要值之和占所有种的80%以上,为该群落的优势种;岷江冷杉种群结构完整,生命期望值与死亡率相对稳定,幼龄个体存活率高,为增长型种群,桦木林幼龄个体比例低,生命期望值波动较大,种群结构不稳定;3个优势种群存活曲线均符合Deevey-Ⅱ型,但又有所区别,其它小规模种群结构多不完整;数量化动态分析表明3个优势种群均为增长型,冷杉种群稳定性最高,红桦次之,糙皮桦种群易受外界干扰。本研究表明,现存群落为桦木—岷江冷杉林群落,各种群尚处于相互适应的变化阶段,群落结构不稳定;岷江冷杉种群更新良好,具有进一步增长趋势,桦木种群逐渐趋于衰退,人工云杉林必会完全淘汰。该群落最终演替成为冷杉林群落的趋势明显,即演替过程为人工云杉林—次生林—岷江冷杉林群落,后期经营应多为冷杉的生长创造有利条件。

The population dynamic of secondary succession stage of degraded artificial Picea asperata forest of Shatan forest farm in Bailongjiang upstream was studied and its dominant population structure,static life table,survival curve were analyzed based on field investigation and data statistics with quantitative methods and time series models,in order to comprehend its species composition and survival status and predict the trend of population development as a theoretical basis for sustainable management of secondary forest in this forest area in the future.The result showed that there were 13 species in arbor layer of secondary forest community and large quantities of artificial P.asperata forests trees in the community.As dominant species in the community,the sum of important values of Betula albosinensis,Betula utilis and Abies faxoniana accounted for more than 80%of all.Moreover,A.faxoniana as expanding population,owned complete population structure,relatively stable life expectancy and mortality rates and higher survival rate of young individuals.Conversely,Birch forest had lower survival rate of young individuals,fluctuating life expectancy and unstable population structure.Furthermore,the survival curves of the 3 dominant populations were consistent with Deevey-Ⅱ,but some differences existed,and the structures of other small populations were mostly incomplete.In addition,quantitative dynamic analysis showed that the 3 dominant populations were all expanding populations.A.faxoniana had highest population stability,then B.albosinensis,and B.utilis was vulnerable to external disturbance.Finally,this study indicated that the existing community was Birch-A.faxoniana forest community in study area,and every population was still in the stage of mutual adaptation and showed unstable community structure.The population of A.faxoniana regenerate better and emerged further growth trend,but Birch forest went into decline and P.asperata forest plantation would be completely phased out.The community had an obvious tendency to become fir forest community,that was the succession process was P.asperata forest plantation,secondary forest,then A.faxoniana community,so advantages for the growth of fir forest should be provided in the future.