Background: Forests in forest-steppe ecotones are usually highly fragmented and much of the forested area is exposed to climate and land-use-related edge effects.
Aim: To test the hypothesis that the epiphytic lichen diversity at the forest edges was reduced compared with that in the forest interior, and to analyse lichen diversity in comparison with the more highly elevated and more continental Mongolian Altai.
Methods: Six plots each in the interior and the edge with a total of 240 Larix sibirica trees were studied in the Katon-Karagai National Park, East Kazakhstan.
Results: Species richness and evenness at the tree level were higher in the interior than at the edge. The epiphytic lichen diversity in the forest interior was similar in the Kazakh and Mongolian Altai, whereas that at the forest edge was lower in the Mongolian Altai.
Conclusions: Strong degradation of the forest edges in the Kazakh Altai is the probable cause of the reduced epiphytic lichen diversity compared with the interior. The similar species richness in the forest interiors of the Kazakh and Mongolian Altai suggests that the differences at the forest edge are probably, at least partly, due to different land-use regimes and not to differences in macroclimate. 相似文献
Lipophilic extractive metabolites in different parts of the shoot system (needles and defoliated twigs) of Korean pine, Pinus koraiensis, and Siberian pine, Pinus sibirica, were studied by GC/MS. Korean pine needles comprised mainly bornyl p‐coumarate, heterocyclic 15‐O‐functionalized labdane type acids (lambertianic acid), 10‐nonacosanol, sterols and their esters. While Siberian pine needles contained less bornyl p‐coumarate, lambertianic acid, sterols and their esters, but were richer in other 15‐O‐functionalized labdane type acids. The major components of the twig extract of P. koraiensis were lambertianic acid, abietane and isopimarane type acids, cembrane type alcohols, 8‐O‐functionalized labdanoids, sterols, sterol esters, and acylglycerols. The same extract of P. sibirica differed in larger amounts of other 15‐O‐functionalized labdane type acids and pinolenic acid glycerides, but in less quantities of cembranoids and 8‐O‐functionalized labdanoids. The labdane type pinusolic acid was detected for the first time in Korean pine. P. koraiensis was found to be unique in the genus for an ability to synthesize phyllocladane diterpenoids. The content of bound Δ5‐unsaturated polymethylene‐interrupted fatty acids in the twig extracts of the both pines was similar or superior to that in their seed oil. Among the pines’ metabolites tested isocembrol was strongest in inhibition of both α‐glucosidase (IC50 2.9 μg/ml) and NO production in activated macrophages (IC50 3.6 μg/ml). 相似文献
The pollen tube enters the embryo sac through the crassinucellus at the micropylar end, and brings about the porogamy. The embryogeny corresponds to the Solanad type. The defference of the suspensor structure is notable by comparing it with the other genera of Zygophyllaceae that have been studied. The endosperm is of the Nuclear type. Mitosis is the main form of the free endosperm nuclei proliferation. No cell plates develop in the early free nuclear division, however, they appear in late development, without developing into the cell wall and disappear ultimately. At the late globular embryo stage, cell formation in endosperm starts first from the micropylar end. The first anticlinal walls develop from the cell plate that is initiated from tile phragmoplast as a result of normal cytokinesis. Follwing this a wall begins to grow from the base of the cell plates, the outer growing margin soon fuses with the wall of the central cell, and the inner growing margin continues to grow towards the central vacuole. The growing walls branch and eventually fuse on the side nearest the central vacuole. Thus, the first periclinal walls are initiated, and a complete endosperm cell is formed. Along with the development of embryo, cell is gradually formed in the endosperm from the micropylar end towards the chalazal end, but the chalazal endosperm is still coenocytic until the endosperm disintegrate completely. The mature seed has no endosperm. 相似文献
Structural aspects of source–sink relations in current-year and second-year shoots of Siberian fir were investigated. The period of linear growth of current-year shoots was accompanied by a decrease in the size of starch granules in chloroplasts and the number of mitochondria, as well as by the disappearance of lipid inclusions in the mesophyll cells of second-year needles. Growth processes did not affect seasonal changes in the structure of chloroplast grana in these cells. After the termination of shoot growth, large polysaccharide globules appeared in the cytoplasm of mesophyll cells in second-year needles. It is possible that the formation of these inclusions prevents the inhibition of the photosynthesis by starch, which was accumulated in chloroplasts. 相似文献
Dependencies of larch (Larix sibirica Ledeb.) growth and reproductive organ formation on its infestation by a phyllophagous miner, larch casebearer (Coleophora sibiricella Flkv., Lepidoptera, Coleophoridae) were studied. The work was performed in the sustained outbreak of the larch casebearer in the forest-steppe-larch forest at Kuznetsk Alatau. For the representative tree groups, we determined shoot linear growth, the number of axillary buds, trunk radial growth, the number of micro- and macrostrobili produced, and the contents of water, monoses, starch, and nitrogenous compounds in needles as dependent on the infestation density. We found that infestation exceeding 0.5 larvae per brachyblast significantly suppressed tree growth and reproductive organ formation. At this threshold value of infestation, a significant inhibition of shoot linear growth can serve a marker for suppressed trunk radial growth and reproductive organ formation. The lower degree of infestation did not suppress larch growth and even stimulated it. This observation, along with our data on the changes in the composition of nitrogenous and carbohydrate compounds in damaged needles, demonstrates the active character of interaction between the host tree and the phyllophagous insect, a transit of the source function from damaged needles to healthy ones, and the stimulated reparation of the assimilation apparatus. 相似文献
We explored two mutually nonexclusive hypotheses on autumnal leaf colouration. The co-evolutionary hypothesis states that
autumnal leaf colouration functions as a handicap signal to herbivorous insects, whereas the photoprotection hypothesis posits
that plant pigments primarily protect the plant against cold-induced photoinhibition and enhance nutrient transfer. To contrast
both hypotheses, we compared yellow and red leaf colouration in three groups of mountain ash (Sorbus aucuparia L.). Two montane groups of different age were characterised by low aphid numbers and low temperature, and a lowland group
by high aphid numbers and high temperature. There were no consistent altitudinal differences in leaf colouration. Compared
to young trees, adult trees developed fewer red but more yellow leaves at high altitude. In the lowland population, the development
of red leaf colour was related to decreasing daytime temperature, whereas the appearance of yellow leaf colouration corresponded
to the decreasing photoperiod. This is consistent with the photoprotection hypothesis. Individual differences in red and yellow
leaf colouration were inversely correlated to the number of fruits, which might be interpreted as a trade-off between reproductive
and protective commitment.
Temperature effects explained variation in aphid numbers over time and leaf colouration explained aphid distribution on a
given day. As predicted by the co-evolutionary hypothesis, strongly coloured individuals harboured fewer aphids than green
or dull-coloured ones. Since decreasing temperature reduced the number of migrating aphids but induced red leaf colouration,
these processes are not mutually fine-tuned, which likely restricts the potential for co-evolution between mountain ash and
aphids. 相似文献
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. 相似文献
In this study, two ursane-type triterpenes, i. e., ursolic acid (UA) and 3-O-β-acetoxyursolic acid (AUA), were isolated and quantified in Sorbus intermedia (EHRH.) PERS. fruits. UA and AUA levels differed slightly throughout fruit maturation, and both triterpenes showed similar dynamics of accumulation with the highest levels found in ripe fruits (up to 6.33±0.56 and 1.17±0.18 mg/g dw. of UA and AUA, respectively). The extracts derived from unripe fruits displayed significant cytotoxic effects against WM793, DU-145, PC3, 8505C, Caco2 and A549 cells, but no correlation between UA and AUA levels and cytotoxicity was found. On the other hand, extracts from mature fruits were not active towards almost all of the tested cell lines. The chemometric approach showed that the extracts derived from fruits harvested earlier clustered to form a clearly distanced group from extracts prepared from more-mature fruits. The extracts at higher concentrations formed separate groups, which indicated the concentration-dependent effect of these extracts on the cells. 相似文献