藏东南川滇高山栎天然林的种内与种间竞争指数的海拔差异

Altitudinal Differences in Intraspecific and Interspecific Competition Index of Natural Forests of Quercus aquifolioides in Southeast Tibet

【目的】通过定量分析藏东南地区不同海拔的川滇高山栎天然林的种内与种间竞争指数,揭示海拔对林木竞争指数的影响,为川滇高山栎天然林的经营和保护提供理论参考。【方法】在西藏林芝市巴宜区鲁朗镇,根据海拔梯度设置4块川滇高山栎天然林样地,土壤类型为山地暗棕壤,林分特征为针阔混交林。对样地内的竞争木和对象木进行调查,采用Hegyi单木竞争模型分析各样地内林木的种内与种间竞争;用幂函数、对数函数、指数函数、多项式、Logistic这5种模型拟合川滇高山栎对象木胸径与其竞争指数变化的回归关系,并选择最优函数。【结果】1)不同海拔的川滇高山栎天然林内的竞争指数不同,海拔3740 m(样地a)、3640 m(样地b)、3540 m(样地c)和3440 m(样地d)样地的种内竞争指数分别占总竞争指数的17.11%、22.26%、30.79%和70.13%,表明样地a、b、c以种间竞争为主,样地d以种内竞争为主。2)在川滇高山栎的伴生树种中,以急尖长苞冷杉的竞争力最强,其次是白桦,竞争力最弱的是糙皮桦。3)在所有样地中,川滇高山栎的竞争指数随对象木胸径增加而不断减小,呈显著负相关。在样地a中对象木胸径与其竞争指数关系的最优模型为幂函数模型,样地b、c的最优模型为三次多项式模型,样地d的最优模型则为指数函数。【结论】藏东南的川滇高山栎林天然林在海拔3440 m以种内竞争为主,在海拔3540~3740 m以种间竞争为主。川滇高山栎的竞争指数随林木胸径增加而下降,在胸径到达25 cm时趋于平稳,采用拟合的模型能有效预测川滇高山栎林的竞争指数。

【Objective】Through quantitative analysis of Interspecific and inter-specific competition index of natural forest of Quercus aquifolioides at different altitudes in southeast Tibet,the influence of altitude on forest competition index was revealed,which provides a theoretical basis for the management and protection of Q.aquifolioides natural forest.【Method】Four sample plots were set up in the Q.aquifolioides natural forest according to the altitudinal gradients in Lulang Town,Bayi District,Nyingchi City,Tibet,with dark brown mountain soil and mixed coniferous and broadleaved forest.Competitive and target trees sample plots were investigated.Hegyi single tree competition model was used to study the interspecific and inter-specific competition in the Q.aquifolioides natural forests at different altitudes;a total of five models,including the power function,logarithmic,exponential,polynomial and Logistic model were used to fit the regression relationship between DBH of target trees of Q.aquifolioides and their competition index,and the optimal function was selected.【Result】1)The competition index of Q.aquifolioides natural forest at different altitudes was different.The Interspecific competition index of 3740 m(plot a),3640 m(plot b),3540 m(plot c),and 3440 m(plot d)accounted for 17.11%,22.26%,30.79%,and 70.13%of the total competition index,respectively,indicating that plot a,b,and c were dominated by inter-specific competition,and plot d was dominated by intra-specific competition.2)Among the associated tree species of Q.aquifolioides,the competitiveness of Abies georgei var.smithii was the strongest,followed by Betula platyphylla,and the weakest was B.utilis.3)In all plots,the competition index of Q.aquifolioides decreased with the increase of DBH,showing a significant negative correlation.In plot a,the optimal model of the relationship between DBH and competition index of the competitive tree is the power function model,the optimal models of plot b and c are the cubic polynomial model,and the optimal model of plot d is the exponential function.【Conclusion】Q.aquifolioides natural forest in southeastern Tibet is dominated by intraspecific competition at an altitude of 3440 m,and interspecific competition at an altitude of 3540-3740 m.The competition index of Q.aquifolioides decreased with the increase of DBH,and tended to be stable when DBH reached 25 cm.The fitted model can be used to effectively predict the competition index of Q.aquifolioides forest.