海南特有种东方琼楠种群结构特征

为探讨海南特有种东方琼楠(Beilschmiedia tungfangensis)种群结构特征,在海南尖峰岭林区设置20.4hm2样地,从种群径级结构、静态生命表、存活曲线、空间分布格局等方面进行分析。结果表明:1)东方琼楠种群径级分布呈倒"J"型,为增长型种群;2)在第Ⅲ级(DBH:10～15cm)时生命期望值最高,向大龄级和小龄级呈递减趋势;3)存活曲线接近DeeveyⅢ型,呈凹型;死亡率曲线和消失率曲线呈"V"型;4)不同分析方法均表明该种群呈聚集分布,且聚群强度较大;5)聚块性指数随径级呈"正余弦"变化。     

中国植物区系新资料

在对中国科学院西双版纳热带植物园标本馆植物标本的鉴定清理工作中,发现中国新记录植物2种,兹报道如下,供有关部门和研究者参考。     

Seed Dispersal of a High Quality Fruit by Specialized Frugivores: High Quality Dispersal?1

Dispersal quality, as estimated by the cumulative effects of dispersal, germination, seed predation, and seedling survival, was examined for Beilschmiedia pendula (Lauraceae) in Monteverde, Costa Rica. I determined the pattern of dispersal by finding seeds deposited by birds, protected the seeds from seed predators with cages to assess germination and seedling survival, and examined seed predation rates with marked seeds. Seed predation, germination, and seedling survival were compared between seeds naturally dispersed by birds and seeds placed at randomly located sites. Approximately 70 percent of seeds dispersed by birds (N= 244) were deposited <10 m from crown edges of fruiting B. pendula trees, although some seeds were dispersed at least 70 m away. Larger seeds were more likely to be dispersed under or close to the parent trees, and larger seeds produced larger seedlings. Seed size was not correlated directly with seedling survival, but larger seedlings at three months were most likely to survive one year. Seed predation by mammals and insects and seedling mortality due to fungal pathogens were concentrated beneath the crowns of parent trees. Seedlings and saplings were more abundant beneath fruiting B. pendula trees, but individuals farther away were taller on average. Thus, dispersal is beneficial for B. pendula, but such benefits appear most pronounced at a small spatial scale; seeds dispersed >30 m from the crown edges actually had a lower probability of survival than those dispersed 10–20 m. Only 10 percent of B. pendula. seeds received high‐quality dispersal in terms of landing in the zone with the highest per seed probability of seedling survival 10–20 m from parental crowns.     

Dancing on the platform: Lability of floral organs of Beilschmiedia appendiculata (Lauraceae)

Floral characters are important for the systematics of the Lauraceae. However, structure and development of the flowers remain poorly known in the family. In this study, we observed the variation and early development of flowers of Beilschmiedia appendiculata, which belongs to the Cryptocarya clade of the family. The results indicate that the shoot apical meristems (SAMs) of the floral buds are enlarged and become a platform for the programmed initiation of the floral organs; floral organs develop basically in an acropetal pattern; phyllotaxis is whorled, initiation of floral primordia within a whorl is asynchronous; floral merosity is extremely variable, for example, dimerous, trimerous, tetramerous, dimerous plus trimerous, and trimerous plus tetramerous. In addition, this species has lost the innermost staminal whorl and glands are not closely associated with stamens of the third staminal whorl, which is unusual in the family Lauraceae. Our new observations broaden our knowledge of the variation of floral structure in Beilschmiedia and pose a fundamental question regarding the ecology underlying the lability of floral organs in B. appendiculata.     

A contribution to the pollen morphology of the Cryptocarya group (Lauraceae)

In this study, pollen grains of 74 taxa (84 specimens) of the Cryptocarya group, including 22 type collections, have been examined by scanning electron microscopy. Pollen grains of Aspidostemon, Endiandra, Hexapora, Potameia and Triadodaphne are described here for the first time. For the other genera (Beilschmiedia, Cryptocarya, Eusideroxylon, Potoxylon) the results of previous studies are largely confirmed, but a novel type of exine covered by clavate-baculate structures was found in a few Cryptocarya species (C. gracilis and C. macrodesme from New Caledonia, C. saligna from South America). A larger diversity of spinule morphology and density than hitherto known is documented among the African species of Beilschmiedia.     

中国樟科植物拾零

报道了中国樟科植物的１个新种,２个新组合,１个新异名和２个新分布。     

昆明西山半湿润常绿阔叶林及其〖HJ*3〗〖HJ*2〗次生演替群落的更新特征

对昆明西山国家森林公园处于不同演替阶段的云南油杉林、云南油杉-滇青冈混交林和滇青冈林内木本植物幼苗的种类组成、数量及更新方式等进行了调查分析。结果表明:在所调查的共144个25m2的样方中,共记录到木本植物幼苗32科45属共49种。随着演替的进行,幼苗总密度表现出先增加后降低的趋势,处于演替中期的云南油杉-滇青冈混交林内幼苗最丰富,平均密度达80株.25m-2。在不同演替阶段各植被类型中,实生和萌生两种更新方式同时存在,单一的更新方式可能使群落的更新面临较大的风险。幼苗发生了顶死或梢枯后,从其根颈处生出多个萌枝形成多干基株的更新方式结合了实生和萌生更新各自的优点,是幼苗在与环境长期作用过程中进化出的一种有效对策。     

Factors limiting the recruitment of Quercus schottkyana,a dominant evergreen oak in SW China

Quercus schottkyana is a dominant species of oak in the Asian evergreen broad-leaved forests in southwestern China but seedlings are uncommon and recruitment is rare. Annual acorn production by Q. schottkyana is variable and the acorns are exposed to a series of mortality risks. Understanding the factors that limit recruitment of the oak requires knowledge of the oak's life cycle from acorn production to germination and seedling establishment. In this study, we first tested the effects of acorn density on establishment of seedlings by placing batches of acorns at different densities throughout the study area. Second, we tested the effects of herbivores on seedling survival by erecting fences around both natural and transplanted seedling populations. Our results show that even though the rate of seedling establishment increases as acorn density increases (for 32-8000 acorns·m^-2), survival rates of seedlings in the field were generally low (0-0.6%). We show that seedling recruitment of Q. schottkyana is mainly limited to the acorn stage where 88% of the acorns died from the combined effects of desiccation and predation by weevils (Curculio) and bark beetles (Coccotrypes sp.). Herbivory results in the death of some seedlings and consequently also affects the recruitment of seedlings of Q. schottkyana.     

Effects of forest fragment management on vegetation condition and maintenance of canopy composition in a New Zealand pastoral landscape

Residual forest fragments in areas dominated by pastoral agriculture can have high value for biodiversity conservation but are still subject to ongoing degradation as (i) processes initiated by fragmentation continue to operate, for example, changes in canopy replacement probabilities; and (ii) deleterious processes impinge upon them from the surrounding matrix, for example, browsing and trampling by vagrant livestock. Responses by management to slow or reverse these processes require evaluation. Stock (mainly cattle and sheep) exclusion by fencing and mammal pest (mainly Trichosurus vulpecula (brushtail possum)) control are currently used as management tools to maintain or improve the vegetation condition of fragments in New Zealand. We examined the effectiveness of these tools by sampling vegetation composition, forest structure and regeneration of woody species in 41 old‐growth fragments dominated by Beilschmiedia tawa, selected to populate a factorial design that included four different fencing classes (unfenced, fenced 2–10, 10–20 and >20 years ago), with and without sustained mammal pest control. Fencing for more than 10 years led to higher abundances of native ground ferns and shrubs, and lower abundances and numbers of mostly adventive herbaceous ground cover species. In contrast, lianes were less abundant with mammal pest control, whereas herbs were more abundant. Fencing led to a high‐density pulse of seedlings and saplings of woody species within 10 years that then thinned. Mammal pest control allowed increases in abundance of some species palatable to T. vulpecula, and increased the ratio of canopy to subcanopy seedlings in the regeneration pulse caused by fencing. Neither treatment, however, led to the restoration of indigenous species richness to reference forest levels, nor allowed densities of juveniles of shade‐tolerant canopy species to establish to levels commensurate with replacement of existing canopy trees. Most woody seedlings that established following fencing were of short‐lived subcanopy species. These management actions will therefore slow but not reverse the long‐term degradation of these forest fragments, which will eventually differ substantially from continuous forest under current management regimes. Additional measures such as replanting may be necessary not only to ensure replacement of some current species but also to restore lost species.     

滇青冈和高山栲种子昆虫寄生及其对种群更新的影响

对昆明西山地区滇青冈(Cyclobalanopsis glaucoides)和高山栲(Castanopsis delavayi)种子(坚果)虫蛀率在两个年份、整个落种期和山坡不同部位的变化情况进行研究,结果表明：① 寄生于滇青冈种子内的象甲为青冈象(Curculio megadens)和Curculio sp.,寄生于高山栲种子内的象甲是Curculio sp.和剪枝象(Cyllorhynchites sp.);② 滇青冈样地的虫蛀率为2484%~2760%,样地间无显著差异,两年间的平均虫蛀率亦无显著差异;高山栲样地间虫蛀率为1794%~2655%,有显著差异性,两年间的平均虫蛀率也有显著差异。③ 高山栲的下落种子虫蛀率随时间逐步下降,9月和10月中下旬出现两个虫蛀率的高峰期;高山栲种子内寄生的昆虫落地后即入土化蛹,滇青冈落地种子内的寄生昆虫在初期会滞留一段时间;④ 虫蛀率与林下实生苗数量无显著相关性,实生苗多集中在大树周围以及草本层植物较丰富的小生境。