Genetic variation and differentiation of the two river sculpins,Cottus nozawae andC. amblystomopsis,deduced from allozyme and restriction enzyme-digested mtDNA fragment length polymorphism analyses

Genetic differentiation of the two sibling species,Cottus nozawae andC. amblystomopsis, from the northern part of Japan (Hokkaido Island and the Tohoku District) was investigated using allozyme variations and restriction fragment length polymorphisms of mitochondrial DNA. Although the two species are morphologically very similar, previously being thought to be a single species, they have different life-cycles;C. nozawae has a fluvial life-cycle with a small number of large-sized eggs, whereasC. amblystomopsis is an amphidromous species with a large number of small-sized eggs. Four populations ofC. amblystomopsis from Hokkaido Island and 24 populations ofC. nozawae (22 from Hokkaido Island and 2 from the Tohoku District) were sampled and examined Intrapopulational differentiation in the two species was measured by examining several indexes, including proportion of polymorphic loci (P), mean heterozygosity (H) and nucleotide diversity (π). All measurements were higher in theC. amblystomopsis populations, suggesting that intrapopulational variation inC. nozawae was less than inC. amblystomopsis and reflecting the difference in effective population sizes between them. Cluster analyses were performed using the UPGMA method, based on the data matrices of genetic distance (D) and the net nucleotide difference (δ) between populations. TheC. nozawae andC. amblystomopsis populations from Hokkaido Island composed a large cluster (Hokkaido group), while theC. nozawae populations from the Tohoku District composed a different cluster (Tohoku group). Bootstrap probabilities deduced from 1000 bootstrap replications for presence or absence of restriction sites showed that the mtDNA haplotypes detected within the Tohoku Group occurred in 99.9% of the bootstrap replicates outside the mtDNA haplotypes of the Hokkaido group, while those within the Hokkaido group occurred in 3.5–64.9% of bootstrap replicates. Consequently, the Hokkaido populations of the two species (Hokkaido group) were genetically close to each other, whileC. nozawae from the Tohoku District (Tohoku group) were distant from the Hokkaido group. These results suggest that the ancestral populations of the two species on Hokkaido Island shared the same gene pool, even after becoming geographically isolated from the ancestral population ofC. nozawae in the Tohoku District by the formation of the Tsugaru Straits.     

Initial establishment and regeneration processes of an outlying isolated <Emphasis Type="Italic">Fagus crenata</Emphasis> Blume forest stand in the northernmost boundary of its range in Hokkaido,northern Japan

We investigated initial establishment and regeneration of an outlying isolated Fagus crenata forest stand at the northernmost boundary of its range in Hokkaido, northern Japan. The study site was located in the Sannosuke beech forest (42°46′48″N, 140°23′43″E), a representative outlying beech stand beyond its continuous range. A rectangular 0.75 ha plot was established on a southwest-facing slope and divided into 300 square sub-plots of 25 m². Within each sub-plot, stems over 5 cm in diameter at breast height (DBH) were identified and measured. Furthermore, the location of stems over 10 cm in DBH (canopy stem) was recorded within each sub-plot, and their increment core samples were extracted. Wood from fallen logs was sampled to estimate the species composition of the coarse woody debris. Micro-relief of the plot was investigated by leveling with compasses for a 2.5 m × 2.5 m grid system. In the plot, the population of F. crenata was divided into three sub-populations by their frequency distribution of age. The oldest sub-population, over 121 years old, had been established in small-localized gap in the plot. The sub-population between 81 and 120 years old and the sub-population less than 80 years old were regenerated after a landslide and windthrow in a 1954 typhoon, respectively. Furthermore, dominant species in the plot shifted from Quercus mongolica var. grosseserrata to F. crenata. Consequently, regeneration of F. crenata, i.e., expansion of forest stands, at the northernmost boundary of its range was primarily dependent on episodic natural disturbance, which may be responsible for the reduction of their migration rate in Hokkaido, northern Japan.     

Isolation and characterization of polymorphic microsatellite loci in <Emphasis Type="Italic">Ardisia crenata</Emphasis> (Myrsinaceae)

Ardisia crenata, an evergreen shrub native to East Asia, has been a serious invasive plant to the southeastern USA. Here 13 polymorphic microsatellite loci were isolated and characterized from an enrichment genomic library of A. crenata. The average allele number of these microsatellites was four per locus, ranging from two to seven. The ranges of observed and expected heterozygosity were 0.000–1.000 and 0.239–0.789, respectively. These microsatellite markers will be useful for investigating population genetics and reproductive ecology of A. crenata.     

Contrasting patterns of nuclear microsatellite genetic structure of Fraxinus mandshurica var. japonica between northern and southern populations in Japan

Aim The aim of this study is to detect extant patterns of population genetic structure of Fraxinus mandshurica var. japonica in Japan, and to provide insights into the post‐glacial history of this species during the Holocene. Location Hokkaido and Honshu islands, Japan (including the Oshima and Shimokita peninsulas). Methods We examined nine polymorphic nuclear microsatellite loci to assess genetic variation within and among 15 populations across almost the entire range of the species in Japan. Extant patterns of geographical structure were analysed using Bayesian clustering, Monmonier’s algorithm, analysis of molecular variance, Mantel tests and principal coordinates analysis. Recent bottlenecks within populations and regional genetic variation were also assessed. Results Northern populations (Hokkaido Island and the Shimokita Peninsula) formed a single homogeneous deme, maintaining the highest level of allelic diversity on the Oshima Peninsula. By contrast, southern populations (Honshu Island) demonstrated strong substructure on both coasts. Specifically, populations on the Pacific side of Honshu exhibited significant bottlenecks and erosion of allelic diversity but preserved distinct subclusters diverging from widespread subclusters on the Japan Sea side of this island. Main conclusions Genetic evidence and life history traits suggest that F. mandshurica occupied cryptic northern refugia on the Oshima Peninsula during the Last Glacial Maximum, which is reflected in the species’ extant northern distribution. Strong geographical structure in southern populations, in agreement with fossil pollen records, suggests geographical isolation by mountain ranges running north–south along Honshu. Given that this tree species is cold‐adapted and found in riparian habitats, populations on the Pacific side of Honshu probably contracted into higher‐elevation swamps during warm post‐glacial periods, leading to a reduction of effective population sizes and rare allelic richness.     

Phenetic diversity in the <Emphasis Type="Italic">Fritillaria camschatcensis</Emphasis> population grown on the Sapporo campus of Hokkaido University

Triploid Fritillaria camschatcensis (L.) Ker-Gawler (2n = 3x = 36) is a wild species growing in the low-lying areas of Hokkaido Island, Japan, including the Sapporo campus of Hokkaido University. Many F. camschatcensis plants grew on the campus about a century ago, but we seldom find the plants nowadays and so a project to restore this species is being planned. Because preservation of genetic diversity and composition in populations has become a major target of conservation, this study compared variation in the F. camschatcensis population on the Sapporo campus with that in two other populations in Hokkaido. Phenetic variation assessed by 57 randomly amplified polymorphic DNA markers showed that the three populations were significantly distinct from each other; analysis of molecular variance showed 64.3% of variation (P < 0.001) existed among the three populations. Comparison of phenetic diversity on the Sapporo campus population with that in the two other populations showed that the Sapporo campus population contained large genetic variation despite reduced plant numbers. These results indicate that multiplying F. camschatcensis individuals on the Sapporo campus is adequate to restore the Sapporo campus population because this population contains enough genetic diversity, and that transplanting from other populations should be avoided so as not to introduce different genotypes into the campus. These results will be used to design the restoration strategy.     

Taxonomic review of the genus <Emphasis Type="Italic">Cottiusculus</Emphasis> (Cottoidei: Cottidae) with description of a new species from the Sea of Japan

A taxonomic review of the cottid genus Cottiusculus Jordan and Starks 1904 established three species, C. nihonkaiensis sp. nov., C. schmidti, and C. gonez. Cottiusculus nihonkaiensis sp. nov., which had been previously confused with C. schmidti, is described on the basis of 32 specimens (44.8–77.9 mm, SL) collected from the Sea of Japan. The new species is very similar to C. schmidti in having a curved barbless uppermost preopercular spine and the lateral line extending past the caudal fin base, but is distinguishable as follows: nasal spines simple or sometimes weakly bicuspid (vs. deeply bicuspid in C. schmidti); first dorsal fin not elongated in either males or females (vs. elongated in males); ventral lateral and lateral line cirri present (vs. absent). The former is known from the Sea of Japan coasts of Hokkaido, Honshu, Kyushu and the Korean Peninsula, and Volcano Bay, Hokkaido, and the latter from the Pacific coast of Tohoku District, Japan. Cottiusculus gonez, known from the Sea of Japan, Sea of Okhotsk and Pacific coast of Hokkaido, is characterized by having a simple nasal spine, the uppermost preopercular spine almost straight with two small cusps dorsally, posterior cusp barbed, and the lateral line almost reaching to the caudal fin base. A lectotype of C. gonez is designated here. Sequence differences in the cytochrome b gene among the above three species of Cottiusculus are also presented.     

Effects of microenvironmental heterogeneity on the seed-to-seedling process and tree coexistence in a riparian forest

In a temperate riparian forest, the effects of substrate types, canopy gaps and conspecific seedfall density were investigated on the seed-to-seedling process for the five dominant species (Aesculus turbinata, Fagus crenata, Acer mono, Pterocarya rhoifolia and Cercidiphyllum japonicum). Densities of seedfall and subsequent seedling recruits were measured in the stand over a period of 6 years. A model assuming that local density of seedling recruits is proportional to seedfall density in the preceding year significantly explained a spatial variation in seedling recruits for all species. Several environmental factors were then added. Substrate composition had a positive effect on P. rhoifolia and C. japonicum. P. rhoifolia was favored by gravel substrate, which also explained the adult distribution of this species in this forest. C. japonicum appeared to be facilitated by a mineral-soil substrate. However, the distributions of this substrate and adults of C. japonicum did not follow each other closely. A. mono was negatively affected by gaps, and F. crenata was negatively affected by conspecific seedfall density. In contrast, A. turbinata was not significantly affected by any of the environmental factors tested. The microenvironmental heterogeneity in this forest explained species coexistence to a limited extent in the context of seed-to-seedling processes. Performances at later stages of the life-cycle and/or catastrophic disturbances (e.g. landslides) might have a stronger influence on species coexistence in this forest.     

Leaf Size and Leaf Area Index in <Emphasis Type="Italic">Fagus sylvatica</Emphasis> Forests: Competing Effects of Precipitation,Temperature, and Nitrogen Availability

Plants across diverse biomes tend to produce smaller leaves and a reduced total leaf area when exposed to drought. For mature trees of a single species, however, the leaf area–water supply relationship is not well understood. We tested the paradigm of leaf area reduction upon drought by a transect study with 14 mature Fagus sylvatica forests along a steep precipitation gradient (970–520 mm y⁻¹) by applying two independent methods of leaf size determination. Contrary to expectation, average leaf size in dry stands (520–550 mm y⁻¹) was about 40% larger and SLA was higher than in moist stands (910–970 mm y⁻¹). As a result of increased leaf sizes, leaf area index significantly increased from the high- to the low-precipitation stands. Multiple regression analyses suggested that average leaf size was primarily controlled by temperature, whereas the influence of soil moisture and soil C/N ratio was low. Summer rainfall of the preceding year was the most significant predictor of total leaf number. We assume that leaf expansion of beech was independent of water supply, because it takes place in May with ample soil water reserves along the entire transect. In contrast, bud formation, which determines total leaf number, occurs in mid-summer, when droughts are severest. We conclude that leaf expansion and stand leaf area of beech along this precipitation gradient are not a simple function of water availability, but are controlled by several abiotic factors including spring temperature and possibly also nitrogen supply, which both tend to increase toward drier sites, thus overlaying any negative effect of water shortage on leaf development.     

Overwintering strategy of wild free-ranging and enclosure-housed Japanese raccoon dogs (<Emphasis Type="Italic">Nyctereutes procyonoides albus</Emphasis>)

The raccoon dog, Nyctereutes procyonoides, is a canid with a passive overwintering strategy in northern Europe. However, the behaviour and physiology of the Japanese subspecies, N. p. albus, which has fewer chromosomes than the other subspecies, remain unknown. We measured body temperature, body composition and blood biochemistry of wild free-ranging and fasted enclosure-housed N. p. albus during boreal winter in Hokkaido, Japan. Body temperature of N. p. albus decreased from 38°C in autumn to 35.9–36.7°C while maintaining a circadian rhythm in late February (n = 3). A transient 18–36% decrease in resting heart rate occurred when body temperature was low (n = 2). Despite a 33–45% decrease in body weight due to winter fasting, circulating glucose, total protein and triglyceride levels were maintained (n = 4). Serum urea nitrogen dropped by 43–45% from autumn to spring, suggesting protein conservation during fasting. The overwintering survival strategy of N. p. albus in central Hokkaido is based upon large changes in seasonal activity patterns, winter denning and communal housing without the large decrease in body temperature that is characteristic of subarctic animals exhibiting hibernation or torpor. Naoya Kitao, Daisuke Fukui and Peter G. Osborne contributed equally to this work     

Probability distributions,vulnerability and sensitivity in Fagus crenata forests following predicted climate changes in Japan

Question: How much is the probability distribution of Fagus crenata forests predicted to change under a climate change scenario by the 2090s, and what are the potential impacts on these forests? What are the main factors inducing such changes? Location: The major islands of Japan. Methods: A predictive distribution model was developed with four climatic factors (summer precipitation, PRS; winter precipitation, PRW; minimum temperature of the coldest month, TMC; and warmth index, WI) and five non‐climatic factors (topography, surface geology, soil, slope aspect and inclination). A climate change scenario was applied to the model. Results: Areas with high probability (> 0.5) were predicted to decrease by 91%, retreating from the southwest, shrinking in central regions, and expanding northeastwards beyond their current northern limits. A vulnerability index (the reciprocal of the predicted probability) suggests that Kyushu, Shikoku, the Pacific Ocean side of Honshu and southwest Hokkaido will have high numbers of many vulnerable F. crenata forests. The forests with high negative sensitivity indices (the difference between simulated probabilities of occurrence under current and predicted climates) mainly occur in southwest Hokkaido and the Sea of Japan side of northern Honshu. Conclusion: F. crenata forest distributions may retreat from some islands due to a high WI. The predicted northeastward shift in northern Hokkaido is associated with increased TMC and PRS. High vulnerability and negative sensitivity of the forests in southern Hokkaido are due to increased WI.     

Soil Organic Carbon Accumulation in Intensively Managed <Emphasis Type="Italic">Phyllostachys praecox</Emphasis> Stands

Area of bamboo forest (Phyllostachys praecox) has rapidly increased in southern China during the last 20 years due to its high economic value. Aims of this study were to analyse the temporal and spatial variations of soil organic matter (SOM) in heavily winter mulched bamboo stands and to estimate potential for carbon sequestration. Total of 60 soil profiles with 0–15 years of bamboo plantation were sampled from three towns in Lin’an County. Results showed that with increased plantation years, SOM decreased slightly at the beginning (1–5 years), and then rose up steadily. Based on the average of the three locations, the highest SOM content of 75.82 g/kg was the surface layer (0–10 cm) of the 15 years. As plantation year increased, the variation of SOM in the surface layer (0–10 cm) was represented by a parabolic shape, and in the second layer (10–20 cm), it was a similar mode, but less vigorous. Soil organic carbon (SOC) storage significantly increased during 5 to 15 years after it reached full production, and the calculated annual SOC increment in 0–40 cm soil profile was about 6.3 t C/ha/year. Therefore, extended Phyllostachys praecox forests can be considered as one option for countering CO₂ emissions and regional climate change.     

The genetic structure of <Emphasis Type="Italic">Quercus crispula</Emphasis> in northeastern Japan as revealed by nuclear simple sequence repeat loci

Previous studies have reached different discussions about the genetic variation and genetic structure of Quercus crispula populations in northeastern Japan. This is a common oak species in Eastern Asia. Some studies have suggested that the populations in northeastern Japan were derived from those remaining in the southwest after the last glacial maximum (LGM), whilst other studies have found evidence that populations persisted in northeastern Japan during the LGM. Using seven highly polymorphic nuclear simple sequence repeat loci, we investigated the genetic structure of 16 Q. crispula populations along a latitudinal gradient in northeastern Japan (northern Honshu and Hokkaido), spanning about half of the species’ biogeographic range in the country. Although the level of population differentiation was low (F _ST = 0.021; G^￠_\textST G^{\prime}_{\text{ST}}  = 0.090), two geographically differentiated clusters were detected by STRUCTURE analysis. The first cluster included most of the populations in Hokkaido, and may indicate continued survival throughout past glacial periods. We found a significant decrease in allelic richness with latitude, so the second cluster may represent an expansion of the lineage from Honshu during the post-glacial period. These results should enhance our understanding of historical north–south migrations of this species in northeastern Japan.     

Climate signals in the ring widths and stable carbon, hydrogen and oxygen isotopic composition of Larix decidua growing at the forest limit in the southeastern European Alps

The southeastern border of the European Alps is not well resourced with high-resolution climate proxies and experiences a distinct climatic regime from the northern and western Alpine zones. Here, we present new high-resolution climatic proxies (AD 1907–2006) from ring widths and stable carbon (δ¹³C), non-exchangeable hydrogen (δ²H) and oxygen (δ¹⁸O) isotope ratios of cellulose extracted from Larix decidua tree rings, growing at the forest limit in the southeastern European Alps (Slovenia). δ¹³C, δ²H and δ¹⁸O are strongly (p < 0.001) and positively correlated with each other. June temperature has the strongest control on tree ring width (TRW), while later summer conditions (July–August) influence the stable isotope composition. All four proxies are strongly correlated (r > 0.4; p < 0.001) with summer temperature and also sunshine hours, while precipitation has less impact. A combination of TRW and δ¹³C provides the greatest potential for reconstructing past temperatures (June–August) with significant (p < 0.001) correlations with gridded temperatures extending across a very large part of southern and western Europe west of the Carpathian Mountains. The water isotopes (oxygen and hydrogen) record conditions in the Adriatic and Mediterranean, which are the source area for the air masses that bring precipitation to this region giving strong correlations with temperatures in southern Italy and the western part of the Balkan Peninsula. Combining proxies with different spatial and temporal signals allows the strength and spatial footprint of climate signals to be enhanced. These findings open new perspectives for climate reconstruction in the southeastern European Alps and Western Balkans.     

The Rate of Degradation of Chemical Cues Indicating Predation Risk: An Experiment and Review

Many prey taxa use kairomones or alarm pheromones to assess the risk of predation in aquatic environments, and the rate at which these cues attenuate determines how precisely they indicate the local density of predators. We estimated the rate of degradation of chemical cues generated by Aeshna dragonfly larvae feeding on Rana temporaria tadpoles. The half‐life of the cue was 35 h and was not influenced by whether it was aged in pond water or tap water or whether other tadpoles were present in the container in which cue‐aging occurred. A review of other published estimates of predator cue half‐life revealed values of 0.2–126 h, and variation among studies was unrelated to the type of aging water, the venue in which water was aged or prey behavior observed (laboratory, field), or the type of behavior that was recorded. We conclude that factors affecting the persistence of predator cues remain uncertain in spite of their importance for understanding the evolution of induced defenses.     

Effects of light and temperature on the attachment and development of <Emphasis Type="BoldItalic">Gloiopeltis tenax</Emphasis> and <Emphasis Type="BoldItalic">Gloiopeltis furcata</Emphasis> tetraspores

Two 60-day experiments were conducted to study the influence of photon flux density (PFD) and temperature on the attachment and development of Gloiopeltis tenax and Gloiopeltis furcata tetraspores. In the first experiment, tetraspores of the two Gloiopeltis species were incubated at five temperature ranges (8°C, 12°C, 16°C, 20°C, 24°C) under a constant PFD of 80 μmol photons m⁻² s⁻¹ with a photoperiod of 12:12. In a second experiment, tetraspores were incubated under five PFD gradients (30, 55, 80, 105, 130 μmol photons m⁻² s⁻¹) at a constant temperature of 16°C with a photoperiod of 12:12. Maximum density of attached tetraspores was observed at 16°C for both species. Maximum per cent of spore germinating into disc was recorded at 12–16°C for G. tenax and 8–12°C for G. furcata. Maximum per cent of discs producing erect axes for G. tenax and G. furcata were recorded at 24°C and 20°C, respectively. Light had no significant effect on tetraspore attachment and developing into disc, but it affected the growth, sprouting and survival of its discs. Under 30–55 μmol photons m⁻² s⁻¹, the discs of the two species of Gloiopeltis did not form thallus until the end of the experiment. Optimum PFD range for G. tenax discs was 80–105 μmol photons m⁻² s⁻¹, whilst it was 80–130 μmol photons m⁻² s⁻¹ for G. furcata. Results presented in this study are expected to assist the progress of artificial seeding of Gloiopeltis.     

Climatic controls on distribution of Fagus crenata forests in Japan

Abstract. We used classification tree analysis to develop a climate‐based distribution model for Fagus crenata forests in Japan. Four climatic variables judged likely to affect the distribution of the species (summer and winter precipitation, minimum temperature of the coldest month and Kira's warmth index) were chosen as independent variables for the model. Latitudinal and longitudinal information was also used to examine effects of spatial autocorrelation on the model. The climatic factors associated with the distribution of the forests were analysed using a classification tree to devise prediction rules. Predicted areas of high probability for forest occurrence lay mainly on the Sea of Japan side of northern Honshu and southern Hokkaido. This is consistent with actual forest distribution. Some areas with high predicted probabilities of F. crenata forest occurrence were beyond the current natural northern range limits of these forests. Since these areas were widely scattered, it was assumed that the species has been hindered from colonizing them due to dispersal limitations. Deviance‐weighted scores, used to compare magnitudes of the contributions of predictor variables, revealed winter precipitation as the most influential factor, followed by the warmth index, the minimum temperature of the coldest month and summer precipitation. Attempts were made to generate ecological explanations for the effects of the four climatic factors on the distribution of F. crenata forests.     

Impact of altitudinal gradients on energetics and efficiencies of N<Subscript>2</Subscript>-fixation in alder–cardamom agroforestry systems of the eastern Himalayas

The impact of altitudinal gradients on the performance of alder–cardamom agroforestry systems was analyzed on nitrogenase activity, N₂-fixation efficiency, and stand energetics and efficiencies in the eastern Himalayas. Acetylene reduction (AR activity) measurements showed that nitrogenase activity considerably increased with advancing altitudes from 500 to 800 m to a peak at 900–1,200 m. AR activity was fairly high, between 1,300 and 1,700 m, and sharply decreased in the stands between 1,800 and 2,100 m. AR activity increased in the growing season and peaked in the rainy season. This significantly coincided with cardamom flowering during the onset of growing season to full fruiting stage at peak activity period. AR activity was dependent on soil temperature and moisture and showed a positive relationship. Nodule moisture was also a limiting factor for AR activity and showed a positive correlation. Diurnal changes showed a marked variation with highest AR activity between 8 and 12 h. The performance of commercial cardamom crop is dependent on the associated shade trees. Yield potential significantly coincided with the rate of N₂-fixation both at age chronosequence and altitudinal gradients. The management comprises growing large number of alder until 10 years and thinning, and gap filling of cardamom up to 20 years. Such maintenance caused non-equilibrium conditions that favored systems efficiency and excellent production until 20 years. System efficiency sharply declined at low rates of N₂-fixation, AR activity, root nodule production, and agronomic yield due to the influence of stand age and altitudinal gradients. Agroforestry stands at 900–1,700 m were more energy cost-effective due to the lower energy required for per-kg N-fixation with high N supply (115–155 kg ha⁻¹) confirming functionally efficient than those stands at extreme higher and lower altitudinal ranges. Therefore, replantation of alder and cardamom and phase wise agroforestry rotation after 20 years could be an ecologically and economically sustainable management practice.     

Antarctic hairgrass expansion in the South Shetland archipelago and Antarctic Peninsula revisited

Populations of both native higher Antarctic plants, Deschampsia antarctica and Colobanthus quitensis, increased during the last decades. However, for D. antarctica, previous population studies on the South Shetland Islands and the Antarctic Peninsula have been too sporadic, patchy, and methodologically different to allow general conclusions. Our aim was to compare sites with D. antarctica along a north–south latitudinal transect with an integral census method to assess the possible impact of climatic change on grass population dynamics. During two summer seasons (2009–2010), plant populations were censed on Fildes and Coppermine Peninsula and several localities on the west coast of the Antarctic Peninsula. Largest plant populations were found on Fildes Peninsula with vegetation cover (VC) of 44–46%. Six out of eleven stands of D. antarctica on Coppermine Peninsula were new records, with increasing plant number and VC (0.1–22%). In the Antarctic Peninsula, contrarily to our expectation, only at Forbes Point, D. antarctica VC was relatively high (ca. 2%) and a new stand of C. quitensis was found. At three previously reported sites, plants had disappeared. Our monitoring confirms that northern D. antarctica populations are expanding, but that this expansion is not continuous along the Antarctic Peninsula and inconsistent with the gradient of relative temperature increase in north–south direction. We suggest that other abiotic and biotic factors are influencing the colonization and expansion of vascular plants in this particular ecosystem.     

Intra-annual variability of anatomical structure and δ<Superscript>13</Superscript>C values within tree rings of spruce and pine in alpine,temperate and boreal Europe

Tree-ring width, wood density, anatomical structure and ¹³C/¹²C ratios expressed as δ¹³C-values of whole wood of Picea abies were investigated for trees growing in closed canopy forest stands. Samples were collected from the alpine Renon site in North Italy, the lowland Hainich site in Central Germany and the boreal Flakaliden site in North Sweden. In addition, Pinus cembra was studied at the alpine site and Pinus sylvestris at the boreal site. The density profiles of tree rings were measured using the DENDRO-2003 densitometer, δ¹³C was measured using high-resolution laser-ablation-combustion-gas chromatography-infra-red mass spectrometry and anatomical characteristics of tree rings (tracheid diameter, cell-wall thickness, cell-wall area and cell-lumen area) were measured using an image analyzer. Based on long-term statistics, climatic variables, such as temperature, precipitation, solar radiation and vapor pressure deficit, explained <20% of the variation in tree-ring width and wood density over consecutive years, while 29–58% of the variation in tree-ring width were explained by autocorrelation between tree rings. An intensive study of tree rings between 1999 and 2003 revealed that tree ring width and δ¹³C-values of whole wood were significantly correlated with length of the growing season, net radiation and vapor pressure deficit. The δ¹³C-values were not correlated with precipitation or temperature. A highly significant correlation was also found between δ¹³C of the early wood of one year and the late wood of the previous year, indicating a carry-over effect of the growing conditions of the previous season on current wood production. This latter effect may explain the high autocorrelation of long-term tree-ring statistics. The pattern, however, was complex, showing stepwise decreases as well as stepwise increases in the δ¹³C between late wood and early wood. The results are interpreted in the context of the biochemistry of wood formation and its linkage to storage products. It is clear that the relations between δ¹³C and tree-ring width and climate are multi-factorial in seasonal climates.