【摘要】 【目的】探讨中国沙棘克隆生长对造林密度的早期响应及其生物量分配调节机制,确定利于种群稳定性长期维持的适宜造林密度。【方法】设置4个造林密度,即2 500、4 444、10 000、40 000株·hm^-2。调查测定时,分株生长能力采用每木检尺法,克隆繁殖能力采用子株个体计数法,克隆扩散能力采用跟踪挖掘法,地上生物量采用平均标准木法,垂直根生物量测定采用格子样方法和全挖法,水平根生物量测定采用跟踪挖掘法。【结果】随着造林密度的增大,分株地径和冠幅生长量呈对数函数下降,而树高生长量差异不显著;克隆繁殖、克隆扩散能力呈上凸抛物线变化即先升后降,且两者之间具有协同作用;地上生物量分配下降、地下生物量分配上升,水平根生物量分配也呈上凸抛物线变化即先升后降;分株生长能力与地上生物量分配呈正相关,克隆繁殖、克隆扩散能力与水平根生物量分配呈正相关。【结论】种群通过地上与地下、水平根与垂直根生物量分配调节,在分株生长与克隆繁殖、克隆扩散之间做出权衡,从而形成与造林密度相适应的个体形态和克隆生长格局。随着造林密度的增大,分株形态呈粗-中-细的变化过程,克隆繁殖和克隆扩散能力呈低-高-低的变化过程,即克隆生长格局呈离散型-聚集型-离散型、种群稳定性呈低-高-低的变化过程。最有利于克隆生长和种群稳定性维持的适宜造林密度为15 000²0 000株·hm^-2。相应的株行距为0.5 m×1.0 m⁰.7 m×1.0 m。更多还原

【Abstract】 【Objective】The population stability of Hippophae rhamniodes ssp. sinensis depends on clonal growth ability and also on levels of environmental resources. However,the effects of the planting density are not well illustrated. This study aims to determine the optimal planting density according to the clonal growth response to the planting density and the regulation mechanism of the biomass allocation. 【Method】Four planting densities,namely 2 500,4 444,10 000,and40 000 plants·hm^-2 were applied. The ramet growth ability was measured for each tally tree. The clonal propagation ability was obtained by counting the daughter ramets. The clonal expansion capability was quantified by tracking the clones. Aboveground biomass was estimated from the average standard trees. The vertical and horizontal root biomasses were determined by weighting all the roots in the grid quadrats and tracked,respectively. 【Result 】 The basal stem diameter and crown growth of the ramets showed logarithmic decreases with increasing planting density,while the height growth was independent of the density. The clonal propagation and expansion abilities showed parabola profiles,with synergistic effect between them. The biomass was allocated more to the belowground and less to the aboveground. The biomass allocation of horizontal roots showed a parabola. The growth ability of the ramets was positively correlated with the aboveground biomass allocation,and the clonal propagation and expansion abilities were positively correlated with thebiomass allocation of the horizontal roots. 【Conclusion】The population is traded-off in the biomass allocation between the above-and the below-ground and between the vertical and horizontal roots,and between ramet growth and the clonal propagation and expansion,by which forms individual shape and clonal growth configuration to adapt planting dnesity.With the increase of initial planting density,the ramet morphology changes from thick to medium and to slender,and the clonal propagation and expansion abilities did as a low-high-low pattern. That is to say,the clonal growth configuration went as a guerrilla-aggregation-guerrilla pattern,and the population stability exhibit a low-high-low changing process.According to this study,the suitable initial planting density is about 15 000 to 20 000 plants·hm^-2,which is most conducive to the clonal growth and the population stability maintenance.更多还原