不同生境下景宁玉兰灌丛萌株形态及其生殖特征

Morphological and reproductive characteristics of the sprouts of Magnolia sinostellata thickets in different habitats

景宁玉兰是萌生能力很强的灌木树种,为了解不同生境下景宁玉兰萌枝形态及其生殖特征,选择了灌丛(SH)、黄山松林(PTF)、落叶阔叶林(DBF)、杉木林(CLF)和林缘(FE)等5种坡向一致的生境类型,通过典型样地调查,比较分析了5种不同生境下景宁玉兰萌枝数量、大小、高度、枝系、开花及结实等性状。结果表明:(1)景宁玉兰在黄山松林下的分布密度最高,但5种生境下景宁玉兰每丛的萌枝数量没有差异,每丛最大萌枝基径对每丛萌枝数有一定影响,但最大萌枝高度与每丛萌枝数没有关系。在所有调查的景宁玉兰居群中,大于2根以上萌枝的灌丛达82.5%,说明萌生更新在种群繁衍中发挥着重要作用。(2)在落叶阔叶林下的萌枝基径显著小于其他生境(P<0.05),黄山松林下一级枝粗度和长度显著小于其他生境(P<0.05);灌丛中的总分枝率和逐步分枝率最高,灌丛和林缘生境的逐步分枝率(SBR_(2:3))高于其他生境。(3)生殖萌枝基径(r=0.320,P<0.05)和高度(r=0.349,P<0.05)与花量均呈显著正相关关系。杉木林下景宁玉兰生殖萌枝的花量显著高于黄山松林、落叶阔叶林和林缘生境(P<0.05)。虽然黄山松林下景宁玉兰萌枝开花率及开花萌枝比例最低,但其果实大小、单果种子粒数及每丛结实率却较高(P<0.05)。(4)景宁玉兰对环境变化极为敏感,生境类型和海拔对萌枝形态和生殖性状均有一定影响。研究表明,景宁玉兰萌生特征主要受其内在生物学特性所控制,而萌枝形态及生殖特征则与其所处环境条件更为密切。

The Magnolia sinostellata species has a strong sprouting ability. To understand the morphological and reproductive properties of the sprouts of the tree species growing in different environments,five habitat types,including the shrubberies (SH),Pinus taiwanensis forest (PTF),deciduous broad-leaved forest (DBF),Cunninghamia lanceolata forest (CLF),and forest edges (FE) were selected on the same aspect. The number,basal diameter,height,branching patterns,flowering and fruiting characteristics of the sprouts of M. sinostellata were investigated in the representative sites at five different habitats. The results showed that (1) the plant density of M. sinostellata was the highest in the P. taiwanensis forest. No differences were observed in the sprout number of each cluster across the five habitats. A certain relationship was observed between the basal diameter of the largest sprout and the sprout number of each cluster,but no relationship was observed between the height of the largest sprout and the sprout number of each cluster across the five habitats. In all populations investigated,82.5% of all thickets were composed of more than two sprouts,indicating that sprouting plays an important role in the regeneration of the M. sinostellata population in Lishui. (2) Except for the sprout number,the morphological parameters ( basal diameter,length,overall bifurcation ratio,stepwise bifurcation ratio ( SBR 1:2 and SBR 2:3 ),and length of first-order branch) of the sprouts varied with different habitats. The basal diameters of the sprouts of M. sinostellata growing in the deciduous broad-leaved forests were the smallest across the five habitats. The basal diameters and lengths of the first-order branches of M. sinostellata growing in the P. taiwanensis forests were the smallest across the five habitats. The overall and stepwise bifurcation ratios in the shrubberies and the stepwise bifurcation ratios (SBR 2:3 ) at the forest edges were the highest across the five habitats. (3) Both the basal diameter and height of the reproductive sprouts were significantly and positively related to the flower number per reproductive sprout (P<0.05). The flower numbers per reproductive sprout and reproductive sprout ratios showed certain differences across the different habitats. The flower numbers per reproductive sprout in the C. lanceolata forests were significantly greater than those in the P. taiwanensis and broad-leaved forests and at the forest edges (P<0.05). The flower numbers per reproductive sprout and reproductive sprout ratios in both the P. taiwanensis and deciduous broad-leaved forests were lower than those in the other habitats,but the fruit sizes,seeds of each fruit,and mean fruit-setting ratio of each cluster in the P. taiwanensis forests were the highest across all habitats. (4) The M. sinostellata plants were sensitive to the environmental changes. Except for the sprout number and stepwise bifurcation ratio (SBR 2:3 ),the morphological parameters and reproductive characters of sprouts were significantly influenced by habitats and altitudes. This study indicated that the sprouting properties of M. sinostellata were mainly controlled by the inherent biological properties. On the other hand,the morphological and reproductive characteristics were markedly related to the environmental conditions.