Post-fire recolonization of dominant epiphytic lichen species on Quercus hypoleucoides (Fagaceae)

Following a forest fire (27 500 ha) in 1994, post-fire recolonization of Quercus hypoeleucoides by epiphytic lichens was documented as changes in lichen cover, number of small thalli, specific factors that affected reestablishment of lichens, and modes of dispersal. Three sites in the Chiricahua Mountains (Arizona, USA) were chosen according to the severity of fire damage—unburned, moderately burned, and severely burned. From 1994 through 1997, the amount of dead lichen cover significantly increased at the moderately burned site. For the same time period, the amount of live lichen cover significantly increased at the severely burned site. Numbers of new thalli increased significantly at the severely burned site each year but only in the last year (1996–1997) for the moderately burned site. Bark texture and proximity to trees with lichens were among the most important physical factors for recolonization. The most important means of dispersal for Flavopunctelia praesignis was fragmentation. For Punctelia hypoleucites, the primary means of dispersal was spores. Increases in live lichen cover and numbers of new thalli occur faster in severely burned areas probably due to the loss of lichens on tree trunks, which provides space and a lack of competition.     

Taxonomic significance of flavonoid variation in temperate species of Nothofagus

Forty-two flavonoids and a stilbene (pinosylvin) were identified in the leaf exudates of 11 temperate species of Nothofagus from South America, Australia and New Zealand. The flavonoid profiles demonstrate significant taxonomic value at the subgeneric level. Most species of subgenus Fuscospora are characterized by the presence of pinosylvin, galangin and galangin methyl ethers. Kaempferol-type flavonols are abundant in subgenus Lophozonia while these flavonols are largely absent from species of subgenus Fuscospora. The flavonoid patterns are largely in agreement with a recent subgeneric classification of Nothofagus.     

Ecological studies on the plants of fagaceae V. Growth in the sapling stage and minimal participation of reserve materials in the formation of annual new shoots of the evergreenQuercus glauca thunb

The growth in the sapling stage and participation of reserve materials in the formation of annual new shoots were studied in the evergreen treeQuercus glauca. The growth and some allometric relationship were analyzed for 1-to 4-year-oldQ. glauca plants. Each individual was felled at the foot, or all the leaves were removed at the end of the growth season (December). Sprouts were formed on the remaining stump and new shoots were formed from winter buds under dark or light conditions. The dry weight of each plant part was measured before and afte,, the formation of these new shoots. The amount of reserve materials in each plant part was estimated from the difference in allometric relatationships before and after the formation of new shoots. Although the results showed that a small amount of reserve material existed in roots, the participation of reserve materials in the formation of annual new shoots was negligible inQ. glauca growing under usual conditions, and substrates for the formation of new shoots were derived from the products of photosynthesis in old leaves and developing new leaves. Some of the growth characteristics ofQ. glauca were compared with those of the deciduous speciesQuercus variabilis to explain ecological behavior of the two species in warmtemperate secondary forests.     

栎链蚧属分类地位讨论及一新种记述：同翅目：蚧总科：链蚧科

栎链蚧属(Asterodiaspis)是专性寄生于壳斗科(Fagacea)植物的特有类群之一,部分种类的雌成虫寄生于同一寄主的不同部位(茎干、叶片)时,在形态上表现出一定的差异,从而表现为食干型(stem-form)和食叶型(leaf-form)的分化,这种生态二型现象(ecologieal dimorphism)表现出本类群的复杂多样性。本文在新种双型栎链蚧A.biformis sp.nov.形态记述的基础上,认为新栎链蚧属Neoasterodiaspis Borchsenius,     

Rapid appearance of 13C in biogenic isoprene when 13CO2 is fed to intact leaves

Biogenic isoprene substantially affects atmospheric chemistry, but it is not known how or why many plants, especially trees, make isoprene. We fed ¹³CO₂ to leaves of Quercus rubra and monitored the incorporation of ¹³C into isoprene by mass spectrometry. After feeding ¹³CO₂ for 9 min we found all possible labelling patterns from completely unlabelled to fully labelled isoprene. By 18 min, 84% of the carbon atoms in isoprene were ¹³C. Labelling of the last 20% of the carbon atoms was much slower than labelling of the first 80%. The rate of labelling of isoprene was similar to that reported for phosphoglyceric acid indicating that there is a close linkage between the carbon source for isoprene synthesis and the photosynthetic carbon reduction pathway.     

Different vulnerabilities of Quercus ilex L. to freeze- and summer drought-induced xylem embolism: an ecological interpretation

Quercus ilex L. growing in the southern Mediterranean Basin region is exposed to xylem embolism induced by both winter freezing and summer drought. The distribution of the species in Sicily could be explained in terms of the different vulnerability to embolism of its xylem conduits. Naturally occurring climatic conditions were simulated by: (1) maintaining plants for 3h at ambient temperatures of 0, -1.5, -2.5, -5.0 and -11°C; and (2) allowing plants to dry out to ratios of their minimum diurnal leaf water potentials (Ψ₁) to that at the turgor loss point (Ψ_tlp) of 0.6, 0.9, 1.05, 1.20 and 1.33. The loss of hydraulic conductivity of one-year-old twigs reached 40% at -1.5°C and at Ψ₁/Ψ_tlP= 1.05. Recovery from these strains was almost complete 24 h after the release of thermal stress or after one irrigation, respectively. More severe stresses reduced recovery consistently. The percentages of xylem conduits embolized following application of the two stresses, were positively related to xylem conduit diameter. The capability of the xylem conduits to recover from stress was positively related to the conduit diameter in plants subjected to summer drought, but not in the plants subjected to winter freezing stress. The ecological significance of the different vulnerabilities to embolism of xylem conduits under naturally occurring climatic conditions is discussed.     

The effects of seed size, cotyledon reserves, and herbivory on seedling survival and growth in Quercus rugosa and Q. laurina (Fagaceae)

In a greenhouse experiment, seedling survival of two oak species (Quercus rugosa and Q. laurina) was greatly affected by the excision of cotyledons 1 mo after germination, with a greater impact on Q. laurina. The effect of seed size was also significant for both species, with a positive correlation between seed mass and survival and growth. The effect of cotyledon excision on seedling growth persisted throughout the first growing season in Q. rugosa and was not analyzed for Q. laurina due to the low number of seedlings that survived cotyledon excision. Seed size significantly affected seedling height, diameter, leaf area, and biomass at 6 mo. Seed size and cotyledon retention affected the ability of Q. rugosa to recover from herbivory, as both factors had a significant effect on relative growth rates after aerial biomass removal. The results show that seedlings originating from large seeds can better endure loss of cotyledons and aerial biomass and thus are better equipped to confront stress early in their lives.     

壳斗科植物摘录(Ⅳ)

<正> 乔木,高达25米,芽近圆球形,芽鳞阔卵形,被早脱落的棕色微柔毛,顶部边缘有红褐色蜡鳞,小枝干后黑褐色,密布微凸起的皮孔。叶近革质,卵状椭圆形或披针形,长10—15厘米,宽3.5—5厘米,顶部渐尖或尾状尖,基部一侧略短且偏斜,宽楔形或急尖,边全缘或近顶部边缘有1—3小裂齿,中脉在叶面凸起,侧脉每边9—12条,网状支脉纤细,新生嫩叶背面沿叶脉被疏长柔毛及散布暗灰色蜡鳞,叶柄长8—10毫米,幼嫩时被疏长柔毛及蜡鳞。雄花序为圆锥花序,花序轴被疏长毛及星芒状蜡鳞,花8—4朵一簇,雌花有花柱8     

中国芸香科及壳斗科植物资料

<正> 芸香科 Rutaceae 酒饼簕属 Atalantia Correa 薄皮酒饼簕 Atalantia henryi (Swingle) Huang, comb. nov. Atalantia racemosa Wight et Arn. var. henryi Swingle in Journ. Arn. Arb. 21:127, 1. 4, Pf. 1—4,1940 et in Webb. et Batc. Citrus Indust. 1:329. 1948; Huang in Acta Phytotax. Sin. 8:115. 1959.     

Castanopsone and castanopsol two new triterpenoids from Castanopsis indica

The isolation of two coumarins and five triterpenoids from Castanopsis indica is described. These have not been reported from this genus previously. The structures of two of the three new triterpenoids have been elucidated by chemical reactions and physical methods.