Ecological Consequences of Transient Outbreaks of Siberian Larch Casebearer,Coleophora sibiricella Flkv., in the Udmurt Republic

A transient population outbreak of the Siberian larch casebearer, Coleophora sibiricella Flkv. (Lepidoptera, Coleophoridae), in a protective forest strip and its consequences for the host tree species (Larix sibirica Ledeb.) have been studied for the first time. It has been shown that one-time complete defoliation by this pest and the following infestation by xylophagous insects result in tree death, while the productivity of surviving trees decreases significantly. The results of this study indicate that the Siberian larch casebearer is a major phyllophagous pest of larch and that its populations must be monitored by specialists in forest pathology.     

Expansion of Evergreen Conifers to the Larch-Dominated Zone and Climatic Trends

The expansion of so-called evergreen conifers (EGCs), including Siberian stone pine, spruce, and fir, along the transect oriented from the boundary of the larch-dominated zone (LDZ; mixed forests of the Yenisei Ridge) to its center has been studied. The normalized dispersal coefficient calculated as K _i = (n _i – N _i )/(n _i + N _i ), where n _i and N _i are the relative numbers of the ith species in the undergrowth and the upper layer, respectively, serves as an indicator of the expansion. It has been found that the K _i values for EGCs (and birch) are higher than the K _i of larch even in the zone absolutely dominated by larch, where the relative numbers of EGCs in the upper layer is less than 1%. The EGC undergrowth has mainly been formed during the past 20–30 years, which is correlated with the trend of summer temperatures The spread of EGCs in the LDZ depends on the frequency of forest fires. The decrease in the time intervals between fires in the 20th century to 65 years (versus 100 years in the 19th century) may have prevented the expansion of competing species in the LDZ. The results obtained indicate that EGCs and birch penetrate into the zone traditionally dominated by larch, which is related to climatic changes during the past three decades. At the same time, tree stand density is increasing in the forest-tundra ecotone, and larch is spreading further into the tundra zone.__________Translated from Ekologiya, No. 3, 2005, pp. 186–193.Original Russian Text Copyright © 2005 by Kharuk, Dvinskaya, Ranson, Im.     

Change in the Life Cycle Strategy of Fish under the Effect of Chronic Water Pollution

Fish of a polymorphic and evolutionarily young species Coregonus lavaretusfrom a subarctic lake that has been polluted for more than 60 years are used as an example for analyzing principal trends in the dynamics of structural and functional organization of fish populations. It is shown that fish exposed to sublethal doses of toxic substances for a long time have a smaller body size, the period of their sexual maturation becomes more variable, and the frequency of spawning and life span decrease. The biochemical and bioenergetic mechanisms of variation in populations are analyzed. The ecological expediency of change in the life cycle strategy corresponding to r-selection (conversion to a short reproductive cycle) is substantiated.     

Structure and Dynamics of Tree Stands at the Upper Timberline in the Western Part of the Putorana Plateau

Russian Journal of Ecology - Analysis of the age structure of Dahurian larch (Larix gmelinii Rupr.) forests in the western part of the Putorana Plateau (Sukhie Gory Range) and comparison of...     

Effect of toxic pollution on fish populations and mechanisms for maintaining population size

The effect of pollution on fish populations has been analyzed. It has been demonstrated that the strategy of the fish life cycle changes in the direction corresponding to r-selection. Smaller individuals that mature at an earlier age and are preadapted to energy allocation for maintaining a higher metabolic rate and activating detoxification gain a survival advantage under toxic conditions. If young females whose gametogenesis is within the normal range join the spawning stock, the population size is successfully maintained but its parameters and gene pool are changed.     

Ecophysiological Responses of Larix sibiricaLedeb. and Pinus sibiricaDu Tour Undergrowth to Climate Change

The effects of probable climate change—an increase in atmospheric CO₂(by two times), air temperature, precipitation—on CO₂exchange and temperature dependence of net photosynthesis in the larch and Siberian stone pine undergrowth formed in the light larch forests of West Siberia were studied in chambers with an artificial climate. The change of the aforementioned ecological factors caused an increase in the temperature optima of photosynthesis and the range of optimum temperatures (in the case of Siberian stone pine, to a slightly greater degree). Therefore, the ranges of both species may broaden, and the Siberian stone pine can expand to the north, displacing larch tree stands.     

Dynamics of the timberline in high mountain areas of the nether-polar Urals under the influence of current climate change

Changes in the altitudinal position of the timberline in high mountain areas of the Nether-Polar Urals and basic factors that influence such changes have been revealed on the basis of comparison of the age structure of Siberian larch (Larix sibirica) and arctic birch (Betula tortuosa) tree stands and photographs made in different years. On the mountain slopes studied, an upward shift of the timberline took place in areas covered in winter with thick snow (in the late 18th century), with Siberian larch being the pioneer species. Larch began colonizing areas with a thin snow cover in the 20th century. Birch appeared later and has since strengthened its positions. The increase in winter temperatures and precipitation facilitated the expansion of the forest.     

Climate changes and overstory recruitment of larch at the northern timberline in the Yamal Peninsula

Studies on overstory recruitment of the Siberian larch (Larix sibirica Ledeb.) in open larch forests depending on the time of seedling establishment (1880–1980) have been performed in the northern timberline ecotone on the Yamal Peninsula. Two periods of active larch establishment have been revealed: from 1900 to 1935 and from 1950 to 1970. A comparison of these data with the results of instrumental observations on temperature and precipitation has shown that the overstory recruitment of larch in valleys of northern rivers is largely dependent on July air temperatures in the first years of tree life, when seedlings grow 10–20 cm high.     

Anthropogenic evolution of animals: Facts and their interpretation

Problems concerning microevolutionary transformations in animal populations are considered. It is shown that genetic variation is the main factor providing the basis for adaptation to environmental changes, including toxic pollution. The selection pressure of a toxic factor gives an advantage in survival to more resistant genotypes in animal populations, which eventually leads to the reduction of their genetic diversity and potential for adaptation to other natural or anthropogenic stress factors. Microevolutionary transformations follow the pattern of r-selection, i.e., occur in favor of smaller, earlier maturing individuals capable of expending a greater proportion of their energy resources for reproduction.     

Effect of Climatic Changes on Radial Increment and Age Structure Formation in High-Mountain Larch Forests of the Kuznetsk Ala Tau

The relationship between growth indices and renewal rates of the Siberian larch (Larix sibiricaLedeb.) stands that have grown at the timberline in the Kuznetsk Ala Tau mountains during the past 350 years was analyzed. The age generations of larch were formed in the 1640s, 1660s, 1680s, 1700s, 1720s, 1740s, 1760s–1770s, 1800s–1810s, 1850s, 1870s–1880s, 1900s, 1920s, and 1930s–1940s. It was shown that the formation of these age generations coincided with 10- to 30-year periods of increased growth of larch and improved temperature conditions in summer.     

Structure and formation of conifer stands in the upper timberline ecotone on the North Chuya Ridge,Central Altai

The structure of Siberian stone pine (Pinus sibirica Du Tour.) and Siberian larch (Larix sibirica Ledeb.) stands and specific features of their formation have been studies in the forest-tundra ecotone on the North Chuya Ridge (2235–2475 m a.s.l.). Changes in the structure of these stands along the transition from the upper boundary of closed forests to the high-mountain tundra have proved to have an ambiguous pattern. Both tree species form mixed clusters of similar-aged trees in the lower part of the ecotone but grow singly, in scatters, in its upper part. The formation of conifer stands (tree clusters) in the lower part of the ecotone, on the slopes of the Aktru River valley, began during climate warming in the second half of the 19th century. The expansion of confers to its upper part took place markedly later, in the early 20th century (Siberian larch) or even in the 1930s (Siberian stone pine).     

Postfire succession in a forest of the cryolithozone: The example of central Yakutia

The results of studies on postfire succession in larch forests of the permafrost zone are discussed. The main directions of successional processes in burned-out areas of different ages are described. It has been shown that secondary pyrogenic successions in larch forests follow the scheme of rapid regeneration without tree species replacement and the model of succession tolerance. Groups of plant species with different life strategies and indicator species characterizing different stages of the overgrowing of burned-out areas have been identified.     

Characteristics of Cajander Larch (<Emphasis Type="Italic">Larix cajanderi</Emphasis> Mayr) on Dredging Waste Dumps in the Amur Region

Former dredging sites were studied in the taiga zone of the Amur region (in Khabarovsk Krai). The involvement of Larix cajanderi in plant succession on dredging waste dumps was revealed. Some morphological-anatomical parameters of L. cajanderi needles were compared in trees growing on the dumps and in adjacent open larch stands on waterlogged peaty soils.__________Translated from Ekologiya, No. 4, 2005, pp. 259–263.Original Russian Text Copyright © 2005 by Osipov, Burundukova.     

Assessment of phytomass changes in an alpine <Emphasis Type="Italic">Geranium-Hedysarum</Emphasis> meadow after the removal of dominants: The results of a ten-year experiment

Changes in the aboveground phytomass of a Geranium-Hedysarum meadow community and its constituent species after the removal of dominants, Geranium gymnocaulon and Hedysarum caucasicum, over ten years have been studied in the Northwestern Caucasus. Responses of individual species to this intervention have been revealed. It has been shown that the phytomass of nondominant species increases under such conditions, but this cannot fully counterbalance the loss of phytomass resulting from the removal of dominants. Dominant species of Geranium-Hedysarum meadows exert different influences on the community structure and also compete with each other. However, this competition is fairly weak, which is probably due to considerable divergence of these species with respect to resource consumption.     

Reconstruction of summer precipitation in the Southern Urals over the last 375 years based on analysis of radial increment in the Siberian larch

Considerable correlation was revealed between the annual radial increment of the Siberian larch (Larix sukaczewii Dyl.) and monthly precipitation in May, June, and July of the current year in the Southern Urals. The regression model of the dependence of latewood growth on the amount of precipitation in May to July was used for reconstructing spring-summer precipitation in the region over the past 375 years (from 1631 to 2005).     

Effect of Ecological Factors on the Accumulation of Fluorine by Larches, <Emphasis Type="Italic">Larix gmelinii</Emphasis> (Rupr.) Rupr. and <Emphasis Type="Italic">L. sibirica</Emphasis> Ledeb., in Eastern Siberia

The accumulation of fluorine in the trunk wood and branches of Larix gmelinii growing on soils with a naturally increased fluoride content and of L. sibirica growing in a zone affected by atmospheric emissions from an aluminum plant has been studied. Based on results of in vivo and in vitro experiments, it is concluded that larch trees manifest individual differences in their response to fluorine.     

Effect of site conditions on the formation of wood anatomical structure in the cajander larch (Larix cajanderi Mayr) in the Amur region

Studies on the Cajander larch (Larix cajanderi) in the Amur region have been performed to evaluate the effect of growth conditions on the development of wood anatomical structure during ontogeny, including the course and rate of definitive (mature) wood formation. Adaptive changes in wood anatomy have been revealed in trees growing in waterlogged areas underlain by permafrost.     

Genetic Diversity in Annual Xerohalophytes of the Family Chenopodiaceae along Soil Moisture and Salinity Gradients

Genetic polymorphism has been studied in populations of two annual xerohalophyte species of the family Chenopodiaceae, Atriplex tatarica and Sedobassia sedoides, growing on soils with different levels of soil moisture and sodium and potassium ion contents. A tendency toward decrease in the percentage of polymorphic loci in A. tatarica at higher soil salinity and increase in the observed heterozygosity of S. sedoides populations at higher levels of soil potassium has been revealed, with parameters of genetic variation in either species showing no dependence on soil moisture. Soil potassium deficiency is a stress factor for S. sedoides at both physiological and population-genetic levels. Mechanisms controlling sodium absorption and maintaining ion homeostasis and also a high level of homozygosity in S. sedoides indicate the improvement of stress tolerance in this annual species.

     

Host Specificity of Flukes of the Genus Sphaerostomum (Trematoda: Opecoelidae) within Their Geographic Ranges

The host specificity of flukes belonging to the genus Sphaerostomum (S. bramae and S. globiporum) in the center and at the periphery of the genus range is discussed. Both fluke species are specific parasites of cyprinids. However, fish of nine other families and one cyclostome species have also been recorded as their hosts. At the periphery of the range, the spectrum of definitive hosts is broader than in the center owing to a greater number of unspecific hosts. In the center, unspecific hosts are represented by six fish species (Esox lucius, Misgurnus fossilis, Perca fluviatilis, Lota lota, Gymnocephalus cernuus, and Salmo sp.), four of which are predators. At the periphery, 11 fish species, including six predators (Anguilla anguilla, Barbatula barbatula, Cottus gobio, Cobitis taenia, Coregonus lavaretus, Salmo trutta, Alosa sp., Potamoschistus minutus, E. lucius, P. fluviatilis, and L. lota), and the cyclostome Lampetra fluviatilis are unspecific hosts. In the peripheral populations, compared to central, flukes manifest greater adaptive plasticity and can infest new hosts.     

Forest-tundra larch forests and climatic trends

Climate-related changes that occurred in the Ary-Mas larch forests (the world’s northernmost forest range) in the last three decades of the 20th century have been analyzed. An analysis of remote-sensing images made by Landsat satellites in 1973 and 2000 has provided evidence for an increase in the closeness of larch forest canopy (by 65%) and the expansion of larch to the tundra (for 3–10 m per year) and to areas relatively poorly protected from wind due to topographic features (elevation, azimuth, and slope). It has also been shown that the radial tree increment correlates with summer temperatures (r = 0.65, τ = 0.39) and the amounts of precipitation in summer (r = ?0.51, τ = 0–41) and winter (r = ?0.70, τ = ?0.48), decreases with an increase in the closeness of forest canopy (r = ?0.52, p > 0.8; τ = ?0.48, p > 0.95), and increases with an increase in the depth of soil thawing (r = 0.63, p > 0.9; τ = 0.46, p > 0.9). The density of undergrowth depends on temperatures in winter (τ = 0.53, p > 0.8) and summer (r = 0.98, p > 0.99, τ = 0.9, p > 0.99) and the date of the onset of the growing period (r = ?0.60, p > 0.99; τ = ?0.4, p > 0.99) and negatively correlates with the amount of precipitation in summer (r = ?0.56, p > 0.99, τ = ?0.38, p > 0.99).