Conditions for the development of the Pinus pumila zone of Hokkaido,northern Japan

The development of the Pinus pumila zone of Hokkaido, northern Japan is discussed on the basis of an examination of the Warmth Index (WI). The Pinus pumila zone is developed on deforested areas in the boreal subalpine belt, and is characterized by strong wind and heavy snow accumulation in winter, and by the presence of rocky fields. It is concluded that in Japan, including Hokkaido, this high mountain zone generally is intrazonal, belonging mainly to the subalpine belt, and that such zones are not common in Europe and North America. Its formation is due mainly to present-day wind, snow and substrate conditions and partly to conditions prevailing during the glacial period.     

Impacts of long-term snow climate change on a high-elevation cold desert shrubland, California, USA

Ecological responses to 50-year old manipulations of snow depth and melt timing were assessed using snow fences arrayed across 50 km of a shrub–conifer landscape mosaic in eastern California, USA. We compared how increased, decreased, and ambient snow depth affected patterns of vegetation community composition, fire fuel accumulation, and annual tree ring growth. We also tested the effect of snow depth on soil carbon storage based on total C content under the two co-dominant shrub species (Artemisia tridentata and Purshia tridentata) in comparison with open, intershrub sites. Increased snow depth reduced the cover of the N-fixing shrub P. tridentata but not the water-redistributing shrub A. tridentata. Annual ring growth was greater on +snow plots and lower on ?snow plots for the conifer Pinus jeffreyi but not for Pinus contorta. Graminoid cover and aboveground biomass indicated higher fire fuel accumulation where snow depth was increased. Dead shrub stem biomass was greater regardless of whether snow depth was increased or decreased. Results demonstrate community shifts, altered tree growth, feedbacks on carbon storage, and altered fire fuel accumulation as a result of changes in snow depth and melt timing for this high-elevation, snow-dominated ecotone under future climate scenarios that envision increased or decreased snow depth.     

How the timberline formed: altitudinal changes in stand structure and dynamics around the timberline in central Japan

Background and Aims

Altitudinal timberlines are thought to move upward by global warming, a crucial topic in ecology. Tall tree species (the conifer Abies mariesii and the deciduous broad-leaved Betula ermanii) dominate the sub-alpine zone between 1600 and 2500 m a.s.l., the timberline, on Mount Norikura in central Japan. Dwarf pine Pinus pumila dominates above the timberline to near the summit (3026 m a.s.l.). This study evaluated how the timberline formed on Mount Norikura by examining altitudinal changes in stand structure and dynamics around the timberline.

Methods

One hundred and twenty-five plots of 10 m × 10 m were established around the timberline (2350–2600 m a.s.l.). Trunk diameter growth rate during 6 years was examined for A. mariesii, B. ermanii and P. pumila. Mortality during this period and mechanical damage scars on the trunks and branches due to strong wind and snow were examined for A. mariesii only.

Key Results

The density, maximum trunk height and diameter of A. mariesii in plots decreased with altitude. The maximum trunk height of B. ermanii decreased with altitude, but density and maximum trunk diameter did not decrease. In contrast, the density of P. pumila abruptly increased from around the timberline. A strong negative correlation was found between the densities of P. pumila and tall tree species, indicating their interspecific competition. Trunk diameter growth rates of A. mariesii and B. ermanii did not decrease with altitude, suggesting that these two tall tree species can grow at the timberline. The ratio of trees with mechanical damage scars increased with altitude for A. mariesii, a tendency more conspicuous for larger trees. The mortality of larger A. mariesii was also greater at higher altitude. Tall tree species may not increase their trunk height and survive around the timberline because of mechanical damage.

Conclusions

This study suggests that the altitudinal location of the timberline is mainly affected by mechanical damage due to strong wind and snow rather than by growth limitation due to low temperature. Therefore, the timberline would not move upward even under global warming if these growth and mortality characteristics do not change for a long time.     

Effects of wind and thermal conditions on timberline formation in central Japan: a lattice model

The upper distribution limit of tall tree species Abies mariesii is the timberline in central Japan, and dwarf pine Pinus pumila dominates above the timberline to near the summit. My previous studies suggested that the main cause of the timberline formation is the increase in mortality due to strong wind in winter rather than low growth due to low summer temperature. This study evaluated how wind velocity affects timberline formation and if the altitude of timberline moves upward due to high thermal conditions, by using a lattice model. Increase in wind velocity throughout the altitude lowered the altitudes of upper distribution limits of the two species. On the contrary, prolonged growth period due to high thermal conditions increased the upper distribution limit of P. pumila, and the upper distribution limit of A. mariesii was hardly affected by the change of growth period. However, the upward shift of the upper distribution limit of P. pumila due to the prolonged growth period in the model would not be realistic because P. pumila had already distributed up to near the summit. This study concludes that A. mariesii is a superior competitor to P. pumila at low altitudes with low wind velocity, but dwarf pine P. pumila can dominate at higher altitudes because A. mariesii suffers severe mechanical damage due to strong wind in winter, and that the altitude of the timberline does not move upward even under high thermal conditions due to global warming.     

Aboveground net production and dry matter allocation ofPinus pumila forests in the Kiso mountain range,central Japan

Aboveground net production rates of the subalpine stone pine (Pinus pumila) forests in central Japan were estimated by the summation method; net production was defined as the sum of annual biomass increment and annual loss due to death. In the two pine stands of different scrub heights, P1 (200 cm) and P2 (140 cm), aboveground biomass reached 177 and 126 ton ha⁻¹, respectively. Leaf biomass was about 14 ton ha⁻¹ in each stand. The estimates of aboveground net production during the 2 year period (1987–1989) averaged 4.1 and 3.7 ton ha⁻¹ y⁻¹ in P1 and P2, respectively, which were at the lowest among the pine forests in the world. Two indices of efficiency of energy fixation, that is, the ratio of net production to the total radiation during a growing season and the ratio of net production to total radiation per unit of leaf weight, were evaluated. Both efficiency indices for the twoP. pumila stands fell in the range obtained for other Japanese evergreen conifer forests. This suggested that the low annual net production of the stone pine stands were mainly due to a limitation in the length of the growing season. The pine forests were also characterized by a small allocation (about 17%) of aboveground net production into biomass increment, in comparison with other evergreen conifer forest types. Annual net carbon gain in theP. pumila forests was suggested to be largely invested in leaf production at the expense of the growth of woody parts.     

Establishment and growth pattern of <Emphasis Type="Italic">Pinus pumila</Emphasis> under a forest canopy in central Kamchatka

We investigated the spatial distribution and growth of the Siberian dwarf pine (Pinus pumila) in a valley–foothill larch–birch (Larix cajanderi–Betula platyphylla as canopy trees) mixed forest of fire origin located in central Kamchatka with the aim of elucidating the ecological features of P. pumila when it is an undergrowth species in a forest. The spatial distribution of all individuals of all tree species was clumped, and the spatial distribution of the two canopy tree species did not repulsively affect that of P. pumila (i.e., its establishment site). These results suggest that the regeneration of P. pumila does not depend on canopy gaps. However, the analysis using a growth model indicated that the canopy trees negatively affected the growth of P. pumila and that the negative effect of L. cajanderi on P. pumila growth was stronger than that of B. platyphylla. The direction of the crown extension of P. pumila was weakly related to the open-space direction. Our results suggest that, although the spatial pattern of establishment of P. pumila is not repulsed by the distribution of canopy trees, the crown can spread horizontally toward the more sparsely populated areas of the canopy trees where they may have higher growth rates.     

Morphometric differentiation,patterns of interfertility,and the genetic basis of character evolution inCrepis tectorum (Asteraceae)

Morphometric analyses of populations ofCrepis tectorum raised under uniform conditions support the earlier finding based on herbarium studies that extensive divergence has taken place in western Europe with a centre of diversity in the Baltic lowland area. A crossing experiment showed that subsp.pumila on the island of Öland has acquired a wide range of derived characters without the establishment of strong reproductive barriers, the only exception being a weak tendency for crosses with other populations on Öland to yield more fertile F₁ offspring than crosses with weedy and non-weedy populations in adjacent regions. Canadian weed populations showed a more uniform response in crosses with subsp.pumila than did morphologically similar weed populations scattered throughout Central Europe. While F₂ data suggest a monogenic basis of differences in the extent of leaf dissection, other distinctive traits appear to be governed by multiple genetic factors with individually slight effects.     

Chloroplast DNA typing by PCR-SSCP in thePinus pumila-P. parviflora var.pentaphylla complex (Pinaceae)

Pinus hakkodensis has been considered as a hybrid betweenP. pumila andP. parviflora var.pentaphylla. Chloroplast DNA typing of this putative hybrid and hypothesized parental species in the Tanigawa Mountains, Japan, was conducted by PCR and single-strand conformation polymorphism (SSCP) of the intergenic spacer betweentrnL(UAA)3′ exon andtrnF(GAA) of cpDNA. Each of the hypothesized parental species collected from other mountain regions displayed a diagnostic SSCP pattern, whereas all morphological intermediates sampled in the Tanigawa Mountains had the SSCP pattern ofP. parviflora var.pentaphylla. Furthermore, some individuals classified on the basis of needle morphology as belonging toP. pumila in this mountain region showed the SSCP pattern ofP. parviflora var.pentaphylla. This may suggest that pollen-mediated uni-directional introgression fromP. parviflora var.pentaphylla toP. pumila occurs in the Tanigawa Mountains.     

Ecological geography of the range of theAbies mariesii forest in northeast Honshu,Japan, with special reference to the physiographic conditions

In the subalpine areas of the snowy regions of Japan (the Japan Sea side), there are some mountains with no or very small stands ofAbies mariesii, although this species dominates the subalpine coniferous forests of the region. In order to discuss the cause and process of this phenomenon, present horizontal and vertical ranges, as well as physiographic conditions, of theA. mariesii forest were examined in detail on the mountains in the Tohoku District. Sites in the subalpine zone were classified into two types: ‘azonal sites’ which should be excluded from the habitat ofA. mariesii because of their edaphic or small-scale climatic properties, and ‘zonal sites’. Mountains with vast less-inclined zonal sites generally had well developed stands ofA. mariesii forest. On the mountains with only small, solitary stands ofA. mariesii, the distribution was limited to flats or slightly inclined slopes at relatively low altitudes. These less-inclined zonal sites were regarded as an important habitat for theA. mariesii forest in the Hypsithermal period and the extent of these sites controls the extent of the stands in that period and the success of the subsequent range expansion of the forest.     

Topographic control of vegetation in a mountain big sagebrush steppe

Mountain big sagebrush steppes in Wyoming have strong spatial patterning associated with topography. We describe the spatial variability of vegetation in a sagebrush steppe, and test the relationship between topography and vegetation using canonical correlation. Results of the analysis suggest that the main control over vegetation distribution in this system is wind exposure. Exposed sites are characterized by cushion plant communities and Artemisia nova, and less exposed sites by the taller sagebrush species Artemisia tridentata ssp. vaseyana. Topographic depressions and leeward slopes are characterized by aspen stands and nivation hollows. Measurements of soil microclimate suggest that a major influence of topographic position on vegetation is snow redistribution and its effect on soil moisture and temperature.Abbreviations ARNO Artemisia nova - ARTRW Artemisia tridentata ssp. wyomingensis - ARTRV Artemisia tridentata ssp. vaseyana - PUTR Purshia tridentata - RIP riparian community - POTR Populus tremuloides - NIV nivation hollow community     

Phylogenetic relationships of the Japanese minnows,Pseudorasbora (Cyprinidae), as inferred from mitochondrial 16S rRNA gene sequences

The phylogenetic relationships among threePseudorasbora fishes (Cyprinidae, Sarcocheiichthyinae) occurring in Japan (P. parva, P. pumila pumila andP. pumila subsp. sensu Nakamura [1963]) were inferred from nucleotide sequences of the mitochondrial 16S rRNA gene. The sequences. of 1240 bp, were determined and compared for 22 specimens from 2–8 populations for each taxon, with a singlePungtungia herzi specimen as an outgroup. A total of 171 sites (13.8%) were variable among the specimens, but only 0–2 sites within each population. The phylogenetic relationships estimated by neighbor-joining, maximum-parsimony and maximum-likelihood methods confirmed a sister relationship between the twoP. pumila subspecies, with a high level of confidence. However, their genetic distinction from each other (4.1±0.4SD % sequence difference on average) was at a level similar to that between them andP. parva (5.9±0.5%). The geographic distribution of the twoP. pumila subspecies, which are separated by the Fossa Magna region, suggests that the genetic divergence of the two subspecies originated from a vicariant process separating the freshwater ichthyofaunas of eastern and western Honshu.Pseudorasbora parva populations were divided into two genetic groups (1.8±0.2% sequence difference), one group comprising continental and part of the Japanese populations, and the other the remaining Japanese populations. This suggests that at least two genetically divergent lineages had been originally distributed in Japan, but a strong possibility remains that the present situation has resulted from artificial transplantation.     

Spatial distribution of cpDNA and mtDNA haplotypes in a hybrid zone betweenPinus pumila andP. parviflora var.pentaphylla (Pinaceae)

Pinus species exhibit paternal chloroplast inheritance and maternal mitochondrial inheritance. This independent inheritance of two cytoplasmic genomes provides an exceptional environment for discriminating female (seeds) and male (pollen) components of gene flow across hybridizing species. We obtained mitochondrial genetic markers diagnostic toP. parviflora var.pentaphylla andP. pumila by PCR amplification of the intron ofnad1 on mtDNA, and examined the spatial-distribution pattern of the mtDNA haplotypes in a hybrid zone betweenP. parviflora var.pentaphylla andP. pumila in the Tanigawa Mountains of Japan. These data, in conjunction with previous information on cpDNA haplotypes and needle morphology, revealed contrastive patterns of introgression of two cytoplasmic genomes. CpDNA introgression has occurred uni-directionally fromP. parviflora var.pentaphylla toP. pumila. Conversely, mtDNA introgression has occurred in the opposite direction, fromP. pumila toP. parviflora var.pentaphylla. Levels of introgression are roughly equivalent for cpDNA and mtDNA. The contrastive spatial distribution pattern of cpDNA and mtDNA haplotypes could be caused by differential movement of seeds and pollen for interspecific genetic exchange.     

Impact of hydrodynamic changes on the zonation of helophytes

Water movement has a strong impact on the development and persistence of helophyte stands along large water bodies. The decline ofScirpus andPhragmites stands in the Rhine-Meuse estuary (The Netherlands), due to changed hydrodynamic conditions (reduced tidal action, increased shoreline erosion), illustrates the effects of large-scale hydrological regulation. Hydrodynamic factors partly explain the distribution and composition of helophyte vegetation bordering the open water. A vertical zonation emerges during the stages of dispersal, germination, seedling establishment and adult growth of the plants. Differences between species may result in the occupation of different water-depth zones. Additionally, gradients of wave exposure result in a horizontal zonation along water bodies. Restrictions to helophyte development due to the hydrological regime and wave attack should be taken into account in wetland restoration studies. Water-level management, instead of a strict control of water levels, should be one of the key elements of water management in the future.     

Release in Manitoba,Canada oftownesilitus bicolor [HYM.: Braconidae], an European parasite ofPhyllotreta spp. [Col.: Chrysomelidae]

Townesilitus bicolor (Wesmael), a parasite of some crucifer-infesting species ofPhyllotreta in Europe, was released in Manitoba Canada in 1978–83, in an attempt to reduce populations ofPhyllotreta cruciferae (Goeze) andP. striolata (Fab.). Releases totalled 1936 adults ofT. bicolor and approximately 2639Phyllotreta collected in Manitoba and parasitized in the laboratory. No evidence of establishment was found up to 1985 at either of the 2 release sites. The small numbers of parasite released, and dispersal of the host population twice each year, have reduced the probability of the parasite becoming established and of establishment being detected. Contribution n^o 1248     

The effect of snow cover on lemming population cycles in the Canadian High Arctic

Rising temperatures and changes in the precipitation regime will have a strong impact on the quality of the snow cover in the Arctic. A snow cover of good quality protecting lemmings from cold temperatures and predators is thought to be an important factor for maintaining the cyclic dynamic of their populations in the tundra. We examined if the characteristics of annual fluctuations (amplitude and shape of phases) in brown lemming (Lemmus trimucronatus) density could be determined by snow depth, snow density, sub-nivean temperature and persistence of snow. Using an 18-year time series of brown lemming abundance on Bylot Island in the Canadian Arctic, we tested if snow variables could explain the residual variation between the observed lemming density and the one predicted by models where cyclicity had been accounted for. Our analysis provides support for the hypothesis that snow cover can affect the amplitude and possibly also the periodicity of lemming population cycles in the High Arctic. Summer abundance of brown lemmings was higher following winters with a deep snow cover and a low-density snow pack near the ground but was unaffected by the date of establishment or melting and duration of the snow cover. Two snow variables showed a temporal trend; mean winter snow depth tended to increase and date of establishment of the hiemal threshold occurred earlier over time. These temporal trends, which should be favourable to lemmings, may explain why healthy population cycles have apparently been maintained at our study site contrary to other Arctic sites.     

Detecting snow-related signals in radial growth of Pinus uncinata mountain forests

Climate warming is responsible for observed reduction in snowpack depth and an earlier and faster melt-out in many mountains of the Northern Hemisphere. Such changes in mountain hydroclimate could negatively affect productivity and tree growth in high-elevation forests, but few studies have investigated how and where recent warming trends and changes in snow cover influence forest growth. A network comprising 36 high-elevation Pinus uncinata forests was sampled in the NE Iberian Peninsula, mainly across the Spanish Pyrenees, using dendrochronology to relate tree radial growth to a detailed air temperature and snow depth data. Radial growth was negatively influenced by a longer winter snow season and a higher late-spring snowpack depth. Notably, the effect of snow on tree growth was found regardless the widely reported positive effect of growing-season air temperatures on P. uncinata growth. No positive influence of moisture from spring snowmelt on annual growth of P. uncinata was detected in sampled forests. Tall trees showed a lower growth responsiveness to snow than small trees. Decreasing trends in winter and spring snow depths were detected at most Pyrenean forests, suggesting that the growth of high-elevation P. uncinata forests can beneficiate for a shallower and of shorter duration snowpack associated with warmer conditions. However, water-limited sites located on steep slopes or on rocky substrates, with poor soil-water holding capacity, could experience drought stress because of early depleted snow-related soil moisture.     

Identifying conservation priority ponds of an endangered minnow, <Emphasis Type="Italic">Pseudorasbora pumila</Emphasis>, in the area invaded by <Emphasis Type="Italic">Pseudorasbora parva</Emphasis>

We investigated the occurrence pattern of the pond-living endangered cyprinid, Pseudorasbora pumila, and also compared its habitat characteristics with those of the congeneric invasive species, Pseudorasbora parva, in the contact zone. Comparison of 16 environmental variables among the P. pumila habitats, P. parva habitats, and unoccupied ponds revealed that conductivity was a common limitation factor of distribution of both species. We found that emergent vegetation occupancy along the pond bank was the most important factor determining P. pumila occurrence and that ponds with steep banks may have a low probability of containing P. parva. We constructed a logistic regression model to predict the establishment risk of P. parva in ponds occupied by P. pumila. The model demonstrated that more than half of the ponds exhibited a high establishment risk of P. parva. Principal component analysis using six parameters selected from stepwise logistic regression analysis revealed that seven unoccupied ponds had the potential to sustain P. pumila, suggesting that our study site is capable of supporting more P. pumila populations and expanding the current range.     

Population structure,gene diversity,and differentiation in natural populations of Cedar pines (Pinus subsect.Cembrae,Pinaceae) in the USSR

Twelve natural populations of four cedar pine species,Pinus sibirica, P. cembra, P. pumila, andP. koraiensis, occurring in the Soviet Union were investigated by starch-gel electrophoresis. Frequencies of 55 alleles at 19 loci were determined. Interpopulation genetic diversity inP. sibirica andP. pumila was only 2–4 per cent of the total genetic diversity. Nei's distance coefficient (Dn) was used to estimate the level of genetic differentiation among conspecific populations and among species. Dn values among populations ranged from 0.006 to 0.038. A dendrogram constructed using Dn values divided cedar pines species into 2 clusters:sibirica-cembra (Dn = 0.030) andpumila-koraiensis (Dn = 0.143). Nei's distance between these clusters was 0.232. On the basis of the data obtained it was possible to draw the following conclusion:P. sibirica, P. pumila, andP. koraiensis are distinct species, whileP. cembra should apparently be regarded as geographicalP. sibirica race.     

Dynamics and dry matter production of belowground woody organs ofPinus pumila trees growing on the Kiso mountain range in central Japan

Size, biomass and spatial distribution patterns of belowground woody organs ofPinus pumila trees were investigated. Dry weight estimates of five sample trees were between 14 and 36 kg tree⁻¹. Belowground stems accounted for about 32% of the total tree weight. However, the belowground stems had extensive barkless portions, indicating that the decomposition of dead belowground stems was an important source of organic matter in the soil. The, basal diameters of adventitious roots tended to become smaller as their orginating positions neared the ground surface. It was suggested thatP. pumila trees regenerate by successively producing adventitious roots from their buried stems and moving down the slope.     

Comparison of genetic population structure between two cyprinids, <Emphasis Type="Italic">Hemigrammocypris rasborella</Emphasis> and <Emphasis Type="Italic">Pseudorasbora pumila</Emphasis> subsp., in the Ise Bay basin,central Honshu,Japan

Two small cyprinid fishes, Hemigrammocypris rasborella and Pseudorasbora pumila subsp. (sensu Nakamura 1963), inhabit similar habitats and often occur sympatrically in the Ise Bay basin, central Honshu Island, Japan. Their genetic population structures were revealed, using sequence data from the mitochondrial cytochrome b gene, and then compared. Hemigrammocypris rasborella populations in the Ise Bay area formed a monophyletic group that has been isolated from eastern (Tenryu River) and western (Lake Biwa–Yodo River) populations at least for several hundred thousand years. Pseudorasbora pumila subsp., endemic to the Ise Bay area, was estimated to have become isolated from its sister subspecies, P. p. pumila, about 5 million years ago. Both H. rasborella and P. pumila subsp. had centers of genetic diversity around the Okazaki Plain in the eastern part of the basin and showed trans-bay distribution of haplotypes or haplotype groups. Their common population structure was explained by geological features in the Ise Bay area, in which a large paleo-river system developed in regression periods, suggesting gene flow among populations of each species in the mid to lower reaches of the paleo-river. Based on the estimated expansion or divergence time, however, not all populations experienced gene flow during the Last Glacial. In contrast to the maintenance of high genetic diversity in H. rasborella, almost all populations of P. pumila subsp. have lost mitochondrial DNA genetic diversity. This implies that effective population size of P. pumila subsp. tended to be smaller, probably because of differences in reproductive ecology, even though the two species have been exposed to similar environmental changes. For conservation of the two species, genetic and adaptive differentiation among local populations should be considered, and attention should be paid to inbreeding depression, especially in P. pumila subsp. An erratum to this article can be found at