Vegetation dynamics in the fens of Chautagne (Savoie,France) after the cessation of mowing

The mechanisms controlling secondary succession on eutrophic peat are analyzed on an area of 500 ha marsh near the Lac du Bourget in the Rhône floodplain between Geneva and Lyon. After describing the succession, the authors compare the succession with that described for fens in England.During succession, three categories of phenomena occur:-Predictable phenomena based on the occurrence of well-established relationships between species with a high cover density. When mowing ceases, populations with increasingly higher biomasses reach dominance one by one.-Phenomena which were to be expected although the manner in which they occurred were more difficult to predict, such as the conditions in which woody plants take over.-Phenomena hidden in the framework of a synchronic analysis. The lowering of the water table, for example, can modify the entire community of species occurring in the sequence as well as the competition between species. The pecularities of each type of ecological situation made it difficult to develop general models.     

桤柏混交林的氮素积累与生物循环

桤柏混交林的氮素积累与生物循环石培礼杨修（中国科学院自然资源综合考察委员会,北京１００１０１）钟章成（西南师范大学生命科学系,重庆６３０７１５）ＴｈｅＡｃｃｕｍｕｌａｔｉｏｎａｎｄＢｉｏｌｏｇｉｃａｌＣｙｃｌｉｎｇｏｆＮｉｔｒｏｇｅｎｉｎｔｈｅＡｌｄ...     

The role of fruit diet within a temperate breeding bird community in southern Spain

In southern temperate regions many fleshy-fruited plant species ripen their fruits during the breeding or early post-breeding season and these are consumed by resident birds. I studied the frugivore community of the summer-fruiting tree Frangula alnus ssp. baetica in southern Spain and the significance of fruit in the diet of adult and recently fledged birds. Twelve species consumed F. alnus fruits. Almost 97% of the foraging visits were carried out by the four most abundant species, Robin Erithacus rubecula, Blackcap Sylvia atricapilla, Blackbird Turdus merula and Blue Tit Parus caeruleus. During the ripening season Robins and Blackcaps concentrated at fruit-rich sites. Entire families of Blackcap and Blackbird regularly entered fruiting trees together. In contrast, adult Robins always foraged solitarily, and accounted for only 4% of the tree visits, while 96% were realized by recently fledged birds of the first brood. In all species, young birds foraged as efficiently as adults. F. alnus fruits are not part of the regular nestling diet, but they are a significant part of the diet for recently fledged Robins during their postnatal dispersal. Conversely, these are the most important and effective seed dispersers while adult Robins scarcely take part in the dispersal of F. alnus seeds.     

国产冻绿属的分类处理

对国产冻绿属植物进行了分类学处理,确认有5种l变种,列出了分种检索表,提出2个新组合.     

Isolation and characterization of 16 polymorphic microsatellite loci for Frangula alnus (Rhamnaceae)

We report the first 16 polymorphic nuclear microsatellite markers developed for Frangula alnus (Rhamnaceae). Markers were tested on all three subspecies as well as on three local populations, including analyses of both leaf and seed endocarps. A total of 87 alleles were found (mean number of alleles per locus was 5.44) for 72 individuals genotyped. Observed and expected heterozygosities ranged from 0.097 to 0.792 and from 0.093 to 0.794, respectively. The levels of polymorphism and exclusionary power of the developed markers render them applicable for parentage analyses and measurements of seed dispersal through direct comparison of endocarps and adult tree genotypes.     

Is patience a virtue? Succession, light, and the death of invasive glossy buckthorn (Frangula alnus)

Non-native, invasive glossy buckthorn (Frangula alnus P. Mill.) threatens North American forests by inhibiting tree regeneration. While glossy buckthorn commonly invades younger, developing forests, we hypothesized that this species is competitively excluded as secondary succession proceeds. Specifically, we tested the hypothesis that glossy buckthorn mortality in New Hampshire forests is associated with low levels of photosynthetically active radiation (PAR), low levels of nutrients in the soil, and greater abundance of shade tolerant tree species. Twenty-six living and 26 dead glossy buckthorn individuals were randomly selected on three, mid-successional study sites in southeastern New Hampshire, USA. Shrub ages, indicated by wood ring counts, showed that both living and dead shrubs were members of the same cohort, roughly 16–18 years of age. Living and dead shrubs were compared as to (1) tree basal area in the surrounding forest (estimated by plot sampling), (2) light intensity in the vicinity of the buckthorn crowns (measured by Sunfleck Ceptometer), (3) canopy openness and % total transmitted PAR (estimated by hemispheric photography), and (4) concentrations of available Ca, P, Mg, and K in the B horizon. Relative to live buckthorn shrubs, dead individuals were associated with greater basal area of shade tolerant species, decreased PAR in the vicinity of shrub crown, and decreased soil concentrations of Ca, P, and Mg. The results are consistent with the hypothesis that competition for light and perhaps nutrients limits the ability of glossy buckthorn to persist in late successional stands. If these relationships are causal, active removal of glossy buckthorn might not be required to reduce its abundance in late successional stands.     

Root-nodules formation byPenicillium sp. onAlnus glutinosa andAlnus incana

A non identified species ofPenicillium induced the formation of nodules on the root system of two species of alder (Alnus glutinosa and A.incana). These so-called myconodules looked like young actinorhizae. Namely only some cortical cells of the young transformed root were invaded by the mycelium. Plasmalemma of the host-cell surrounded the hyphae when they penetrated in the cell, but then the fungus colonized all the cell, the contents of which degenerated. In spite of this necrophytic relationships the plant showed no evident damage after the infection.     

Short-Lived Tree Species and Their Role as Indicators for Plant Diversity in the Restoration of Natural Forests

Anthropogenic forests, particularly conifer monocultures, today constitute a large proportion of Central European woodland. Conversion of such forest stands into abundantly structured mixed‐species woodland is within the focus of ecosystem restoration and is considered to affect forest biodiversity. Short‐lived tree species play an important role in such conversion processes and may serve as focal species. However, not much is known about their relationship with forest biodiversity. In this study, the short‐lived tree species, European mountain ash (Sorbus aucuparia L.), European white birch (Betula pendula Roth), Downy birch (B. pubescens Ehrh.), and Glossy buckthorn (Frangula alnus P. Mill.), commonly occurring throughout Central Europe, are investigated with regard to their relationship with plant diversity. The focus is on their occurrences in Scots pine (Pinus sylvestris L.)–dominated forests in the Northeast German lowlands. A significant increase in vascular plant diversity is revealed in stands with the selected species’ presence, in comparison to stands without them. Increase in plant species numbers is highest where the respective species occurs in the tree and/or shrub layer, compared with their presence only in the herb layer. For bryophyte species, there is a less strong inverse relationship. An analysis of different species groups, such as threatened, woody, and typical forest species of higher plants, reveals no decrease in species numbers in these groups if short‐lived tree species are present. It is concluded that short‐lived tree species can be indicators for plant diversity assessment within forest restoration processes. As to causal explanations, effects of differing site conditions, assessed by use of Ellenberg indicator values, are discussed as well as possible active effects of the tree species changing their environment.