Altitudinal Distribution Limits Research Articles

An experimental test of niche versus dispersal limitation of the distribution limit of the Ghost Antler Lichen,Pseudevernia cladonia, along a temperate–boreal elevation gradient

Understanding the mechanisms underlying species’ distribution limits is critical for predicting how species may respond to environmental change. For species restricted to mountain summits, there is concern that climatic changes may result in increasingly restricted distributions. Two central mechanisms govern species distribution limits: (i) niche limitations–environmental conditions beyond distribution limits that are insufficient for survival and reproduction, and (ii) dispersal limitations that prevent colonization of suitable habitat beyond distribution limits. Here, we conducted a transplant experiment to examine the effect of niche versus dispersal limitation on the altitudinal distribution limit of the Ghost Antler Lichen ( Pseudevernia cladonia (Tuck.) Hale & Culb.) that, within Québec, Canada, is restricted to high-elevation mountain summits in the southeast. Along an elevation gradient, we transplanted individuals into sites within its distribution, at the edge, and beyond its distribution. We observed that survival and performance were greatest within its distribution and decreased markedly beyond its distribution, supporting our prediction that this lichen is niche limited along the elevation gradient. We suggest that cooler and more humid conditions at the summit are important environmental factors for this species’ persistence. Our findings suggest that projected climatic changes in these montane habitats may result in less suitable habitat for this species.

Conservation Genetics of the Only Honeysuckle Azalea (Rhododendron luteum) Population Present in Greece

Honeysuckle azalea (Rhododendron luteum) has only a single population occurrence in Greece, on Lesvos Island of the north-eastern Aegean Sea. The genetic diversity of this population was studied in a population of n = 37 individuals randomly sampled in a transect spanning between the highest and lowest natural altitudinal distribution limits in Mt. Ordymnos, SW Lesvos. A modified DNA extraction and isolation protocol was used to overcome problems of DNA quality due to secondary metabolite activity. Genetic variation was investigated based on molecular Inter Simple Sequence Repeat (ISSR) markers. Results showed the presence of a sufficient amount of genetic diversity for the maintenance of adaptive potential. Genetic diversity was lower but comparable to that of other Rhododendron species sampled from the centre of their natural distribution, despite the relatively small population size, negative anthropogenic pressure and population isolation due to the island environment. Some structuring of genetic diversity was indicated based on a PCoA analysis and the genetic distance dendrogram, while spatial autocorrelation was highly significant. Results point towards the need to assign a protection status to the whole area of the species’ natural distribution on Lesvos Island. Moreover, it is proposed that an in situ Gene Conservation Unit (GCU) be established in the core of this population in Lesvos as part of the Network of the European Forest Genetic Resources Programme, while the establishment of ex situ conservation is also advised.

Social Parasite Ants in the Alps: a New Site of the Vulnerable Myrmica myrmicoxena and New Uppermost Altitudinal Limit for M. microrubra

We conducted a survey on the Alpine fauna of one of the largest Natural Park of the Italian Alps (Stelvio National Park) in the framework of a broad ecological monitoring of Alpine biodiversity. A two-years standardized sampling employing pitfall traps along a 1200 m altitudinal gradient led to the discovery of two interesting inquiline social parasite ants of the genus Myrmica: M. myrmicoxena Forel, 1895 and M. microrubra Seifert, 1993. Myrmica myrmicoxena, which is classified as Vulnerable according to the IUCN Red List, was so far known from only three sites across a narrow geographic range between Italy and Switzerland. Our data support the previous hypothesis over its ecology and host association. Myrmica microrubra is considered an incipient species of high evolutionary interest, sometimes regarded as an intraspecific form of M. rubra. While having a wide distribution in Europe, its presence in Italy was hitherto known only from a single site, and our record extends its altitudinal distribution limit in Europe upwards by about 600 m.

Phytocoenotical behaviour of boreal plant species in broadleaved-forest zone communities

Phytocoenotic behaviour of 11 species of boreal vascular plants and mosses is analyzed within the broadleaved-forest zone in comparison with that in different subzones of the boreal-forest zone, based upon the set of 1417 relevés made in European Russia in 1996–2017. The significance of differences in species cover is estimated by means of the one-way ANOVA. The cover of species like Vaccinium myrtillus, V. vitis-idaea, andHylocomium splendens in broadleaved / spruce forests of zonal types is constantly decreasing southwards. On the contrary, the cover of Luzula pilosain Scots pine forests and Pleurozium schreberi and Dicranum polysetum in paludified Norway spruce forests is subject to southward increase. Finally, Oxalis acetosella and Equisetum sylvaticum demonstrate maximae of their cover in forests of zonal types in the southern-boreal and hemiboreal subzones. The dark-coniferous boreal forest “cortege” of species is breaking down into several different floristic elements in the broadleaved-forest zone. These are: “vaccinietal” species p. p. sensu Yu. D. Kleopov (like Vaccinium myrtillus), “quasi-boreal” species sensu V. B. Sochava (Oxalis acetosella, Maianthemum bifolium, Trientalis europaea), hygromesophytes with aged areas (Equisetum sylvaticum), associated species with European-Ancient-Mediterranean nemoral (Luzula pilosa) or East-Asian boreal-montane (Rubus saxatilis) origins. Phytocoenotical behaviour of species is not always different in the intrazonal and the zonal community types but is rather similar in many cases like those of Vaccinium vitis-idaea and Equisetum sylvaticum. The more distinct differences in species positions are found in the extrazonal communities. The statistically proved differences are lacking in phytocoenotical behaviour of Maianthemum bifolium and Trientalis europaea in different zones and subzones due to either florogenetical, or purely methodical reasons, the latter connected with low abundance but high constancy of these species. Disintegration of vegetation “corteges” and individualization of coenotic patterns of species previously growing together are usually observed at the climatically determined (zonal / subzonal or altitudinal) distribution limits.

Middle and Late Holocene altitudinal distribution limit changes of Fagus crenata forest, Mt. Kurikoma, Japan indicated by stomatal evidence

This study proposes a new method to detect changes of altitudinal distribution limit of a plant species based on the stomatal analysis of fossilized leaves. We use the Holocene fossil leaves of Fagus crenata (Japanese beech), a dominant deciduous tree in the cool temperate zone, from different horizons in a peat bog in Mt. Kurikoma, north Japan. Results of palaeo‐CO2 concentration reconstructed from the stomatal analysis indicate palaeo‐CO2 fluctuation between 317 and 352 ppmv during the Middle–Late Holocene, which was more variable and higher than Greenland and Antarctic ice‐core records. This result is possibly influenced by the oceanic CO2 uptake, which increased with the strengthening of the Tsushima Warm Current during the Middle Holocene. The stomatal index (SI) variation range of fossil Fagus crenata leaves in the Middle Holocene was higher than that of the modern population at a given altitude, indicating transportation of leaves from an altitude higher than the site of fossil deposition. A decreasing trend of the SI variation range between 5000 and 2500 cal. a BP can possibly be attributed to the downward shift of the upper distribution limit of Fagus crenata from an altitude higher than or similar to the present limit to the area surrounding the fossil deposition site. This downward shift of the upper distribution limit of Fagus crenata was simultaneous with temperature and humidity decreases and correlated with the decreasing East Asian Summer Monsoon intensity and a cooling event around 4000 cal. a BP.

Air moisture signals in a stable oxygen isotope chronology of dwarf shrubs from the central Tibetan Plateau.

Annually resolved biological climate proxies beyond the altitudinal and latitudinal distribution limit of trees are rare. In such regions, several studies have demonstrated that annual growth rings of dwarf shrubs are suitable proxies for palaeoclimatic investigations. In High Asia, the pioneer work of Liang et al. (Liang E, Lu X, Ren P, Li X, Zhu L, Eckstein D, 2012. Annual increments of juniper dwarf shrubs above the tree line on the central Tibetan Plateau: a useful climatic proxy. Annals of Botany109: 721-728) confirmed the suitability of shrub growth-ring chronologies for palaeoclimatic research. This study presents the first sensitivity study of an annually resolved δ18O time series inferred from Wilson juniper (Juniperus pingii var. wilsonii) from the northern shoreline of lake Nam Co (Tibetan Plateau). Based on five individual dwarf shrub discs, a statistically reliable δ18O chronology covering the period 1957-2009 was achieved (expressed population signal = 0.80). Spearman's correlation analysis between the δ18O chronology and climate variables from different sources was applied. In a first step, the suitability of various climate data was evaluated. Examinations of climate-proxy relationships revealed significant negative correlations between the δ18O shrub chronology and summer season moisture variability of the previous and current year. In particular, relative humidity of the previous and current vegetation period significantly determined the proxy variability (ρ = -0.48, P < 0.01). Furthermore, the δ18O variability of the developed shrub chronology significantly coincided with a nearby tree-ring δ18O chronology of the same genus (r = 0.62, P < 0.01). The δ18O shrub chronology reliably recorded humidity variations in the Nam Co region. The chronology was significantly correlated with a nearby moisture-sensitive tree-ring δ18O chronology, indicating a common climate signal in the two chronologies. This climate signal was likely determined by moisture variations of the Asian summer monsoon. Local climate effects were superimposed on the supra-regional climate signature of the monsoon circulation. Opposing δ18O values between the two chronologies were interpreted as plant-physiological differences during isotopic fractionation processes.

Altitudinal distribution limits of aquatic macroinvertebrates: an experimental test in a tropical alpine stream

1. Temperature and oxygen are recognised as the main drivers of altitudinal limits of species distributions. However, the two factors are linked, and both decrease with altitude, why their effects are difficult to disentangle.2. This was experimentally addressed using aquatic macroinvertebrates; larvae of Andesiops (Ephemeroptera), Claudioperla, (Plecoptera), Scirtes (Coleoptera) and Anomalocosmoecus (Trichoptera), and the amphipod Hyalella in an Ecuadorian glacier‐fed stream (4100–4500 m a.s.l.). The following were performed: (i) quantitative benthic sampling at three sites to determine altitudinal patterns in population densities, (ii) transplants of the five taxa upstream of their natural altitudinal limit to test the short‐term (14 days) effect on survival, and (iii) in situ experiments of locomotory activity as a proxy for animal response to relatively small differences in temperature (5 °C vs. 10 °C) and oxygen saturation (55% vs. 62%).3. The transplant experiment reduced survival to a varying degree among taxa, but Claudioperla survived well at a site where it did not naturally occur. In the in situ experiment, Scirtes and Hyalella decreased their activity at lower oxygen saturation, whereas Andesiops and Anomalocosmoecus did so at a low temperature. The decrease in activity from a high to a low temperature and oxygen for the five taxa was significantly correlated with their mortality in the transplant experiment.4. Together the present experiments indicate that even relatively small differences in temperature and oxygen may produce effects explaining ecological patterns, and depending on the taxon, either water temperature or oxygen saturation, without clear interacting effects, are important drivers of altitudinal limits.

Climatic niche conservatism and biogeographical non-equilibrium in Eschscholzia californica (Papaveraceae), an invasive plant in the Chilean Mediterranean region.

Species climate requirements are useful for predicting their geographic distribution. It is often assumed that the niche requirements for invasive plants are conserved during invasion, especially when the invaded regions share similar climate conditions. California and central Chile have a remarkable degree of convergence in their vegetation structure, and a similar Mediterranean climate. Such similarities make these geographic areas an interesting natural experiment for testing climatic niche dynamics and the equilibrium of invasive species in a new environment. We tested to see if the climatic niche of Eschscholzia californica is conserved in the invaded range (central Chile), and we assessed whether the invasion process has reached a biogeographical equilibrium, i.e., occupy all the suitable geographic locations that have suitable conditions under native niche requirements. We compared the climatic niche in the native and invaded ranges as well as the projected potential geographic distribution in the invaded range. In order to compare climatic niches, we conducted a Principal Component Analysis (PCA) and Species Distribution Models (SDMs), to estimate E. californica's potential geographic distribution. We also used SDMs to predict altitudinal distribution limits in central Chile. Our results indicated that the climatic niche occupied by E. californica in the invaded range is firmly conserved, occupying a subset of the native climatic niche but leaving a substantial fraction of it unfilled. Comparisons of projected SDMs for central Chile indicate a similarity, yet the projection from native range predicted a larger geographic distribution in central Chile compared to the prediction of the model constructed for central Chile. The projected niche occupancy profile from California predicted a higher mean elevation than that projected from central Chile. We concluded that the invasion process of E. californica in central Chile is consistent with climatic niche conservatism but there is potential for further expansion in Chile.

A snail perspective on the biogeography of Sulawesi, Indonesia: origin and intra-island dispersal of the viviparous freshwater gastropod Tylomelania.

The complex geological history of the Indonesian island Sulawesi has shaped the origin and subsequent diversification of its taxa. For the endemic freshwater snail Tylomelania a vicariant origin from the Australian margin has been hypothesized. Divergence time estimates from a mtDNA phylogeny based on a comprehensive island-wide sampling of Tylomelania fit regional tectonic constraints and support the ‘out-of-Australia’ vicariance hypothesis. The Banggai-Sula region of the Sula Spur, the Australian promontory colliding with West Sulawesi during the Miocene, is identified as a possible source area for the colonization of Sulawesi by the ancestor of Tylomelania. The molecular phylogeny also shows a rapid diversification of Tylomelania into eight major lineages with very little overlap in their distribution on the island. Haplotype networks provide further evidence for a strong spatial structure of genetic diversity in Tylomelania. Distribution boundaries of the major lineages do at best partially coincide with previously identified contact zones for other endemic species groups on Sulawesi. This pattern has likely been influenced by the poor dispersal capabilities and altitudinal distribution limits of this strict freshwater inhabitant. We suggest that late Miocene and Pliocene orogeny in large parts of Sulawesi has been the vicariant event driving primary diversification in Tylomelania.

Phenotypic plasticity facilitates resistance to climate change in a highly variable environment

Increased summer drought will exacerbate the regeneration of many tree species at their lower latitudinal and altitudinal distribution limits. In vulnerable habitats, introduction of more drought-tolerant provenances or species is currently considered to accelerate tree species migration and facilitate forest persistence. Trade-offs between drought adaptation and growth plasticity might, however, limit the effectiveness of assisted migration, especially if introductions focus on provenances or species from different climatic regions. We tested in a common garden experiment the performance of Pinus sylvestris seedlings from the continental Central Alps under increased temperatures and extended spring and/or summer drought, and compared seedling emergence, survival and biomass allocation to that of P. sylvestris and closely related Pinus nigra from a Mediterranean seed source. Soil heating had only minor effects on seedling performance but high spring precipitation doubled the number of continental P. sylvestris seedlings present after the summer drought. At the same time, twice as many seedlings of the Mediterranean than the continental P. sylvestris provenance were present, which was due to both higher emergence and lower mortality under dry conditions. Both P. sylvestris provenances allocated similar amounts of biomass to roots when grown under low summer precipitation. Mediterranean seedlings, however, revealed lower phenotypic plasticity than continental seedlings under high precipitation, which might limit their competitive ability in continental Alpine forests in non-drought years. By contrast, high variability in the response of individual seedlings to summer drought indicates the potential of continental P. sylvestris provenances to adapt to changing environmental conditions.

Responses to climate by tree-ring widths and maximum latewood densities of two Abies species at upper and lower altitudinal distribution limits in central Japan

This study examined the effects of climate on tree-ring widths and maximum latewood densities of Abies veitchii and Abies mariesii at the upper and lower distribution limits in central Japan. A. veitchii and A. mariesii dominated at the lower and upper parts of the subalpine zone, respectively. Residual chronologies of tree-ring width and maximum latewood density were developed for the two Abies species at the upper and lower distribution limits, and were compared with monthly mean temperatures and monthly sums of precipitation. Tree-ring widths of the two Abies species at the upper and lower distribution limits positively correlated with temperatures during the beginning of the dormant season and during the growing season of the current year, except for A. veitchii at the lower distribution limit, which showed no positive correlation with temperature. Maximum latewood densities of the two Abies species at the upper and lower distribution limits positively and negatively correlated with temperatures and precipitation, respectively, during the growing season of the current year. Therefore, tree-ring widths and maximum latewood densities of the two Abies species were sensitive to low temperature, except for the tree-ring width of A. veitchii at the lower distribution limit with the warmest thermal conditions along the altitude. Global warming is suggested to affect maximum latewood densities and tree-ring widths of the two Abies species along the altitude.

Environmental change without climate change?

Environmental change without climate change?

Differences between tree species seedling and adult altitudinal distribution in mountain forests during the recent warm period (1986–2006)

Spatial fingerprints of climate change on tree species distribution are usually detected at latitudinal or altitudinal extremes (arctic or alpine tree line), where temperatures play a key role in tree species distribution. However, early detection of recent climate change effects on tree species distribution across the overall temperature gradient remains poorly explored. Within French mountain forests, we investigated altitudinal distribution differences between seedling (≤50 cm tall and &gt;1 yr old) and adult (&gt;8 m tall) life stages for 17 European tree taxa, encompassing the entire forest elevation range from lowlands to the subalpine vegetation belt (50–2250 m a.s.l.) and spanning the latitudinal gradient from northern temperate to southern Mediterranean forests. We simultaneously identified seedlings and adults within the same vegetation plots. These twin observations gave us the equivalent of exactly paired plots in space with seedlings reflecting a response to the studied warm period (1986–2006) and adults reflecting a response to a former and cooler period. For 13 out of 17 species, records of the mean altitude of presence at the seedling life stage are higher than that at the adult life stage. The low altitudinal distribution limit of occurrences at the seedling life stage is, on average, 29 m higher than that at the adult life stage which is significant. The high altitudinal distribution limit also shows a similar trend but which is not significant. Complementary analyses using modelling techniques and focusing on the optimum elevation (i.e. the central position inside distribution ranges) have confirmed differences between life stages altitudinal distribution. Seedlings optima are mostly higher than adults optimum, reaching, on average, a 69 m gap. This overall trend showing higher altitudinal distribution at the seedling life stage in comparison to the adult one suggests a main driver of change highly related to elevation, such as climate warming that occurs during the studied period. Other drivers of change that could play an important role across elevation or act at more specific scales are also discussed as potential contributors to explain our results.

Low impact of climate change on subalpine grasslands in the Swiss Northern Alps

AbstractWhile phenological shifts and migration of isolated species under climate change have already been observed on alpine summits, very few studies have focused on community composition changes in subalpine grasslands. Here we use permanent plots monitored since 1954 and precisely located phytosociological censuses from 1970 to study compositional changes of subalpine grasslands in two distinct regions of the Swiss Northern Alps. In both areas, warming trends during the monitoring period were associated with changes in land management (abandonment of goat and sheep pasturing or grazing replaced by mowing). Old and recent inventories were compared with correspondence analyses (CA). Ecological indicator values, community‐affinities and biological traits of the species were used to infer the factors responsible for triggering the observed changes. In both regions, subalpine grasslands were stable with smaller changes than have previously been observed in alpine environments. Only a few species appeared or disappeared and changes were generally limited to increasing or decreasing frequency and cover of certain taxa. At one site, grazing abandonment favored fallow species. Some of these species were located at their upper altitudinal distribution limits and may have spread because of rising temperatures. In both areas, declining species were predominantly alpine and low‐growing species; their decline was probably due to increased competition (e.g., shadow) with more vigorous subalpine taxa no longer limited by grazing. We conclude that vegetation communities can respond rapidly to warming as long as colonization is facilitated by available space or structural change. In the subalpine grasslands studies, changes were mainly driven by land management. These communities have a dense vegetation cover and newly arriving herbaceous species preferring warmer conditions may take some time to establish themselves. However, climate disturbances, such as exceptional drought, may accelerate community changes by opening gaps for new species.

Age-Specific and Season-Specific Mollusk Damage to Seedlings of Grassland Asteraceae

seedlings of the montane C. pseudophrygia and the closely related, widely distributed C. jacea revealed similar growth patterns and nearly the same damage, and therefore gave no indication that the lower altitudinal distribution limit of C. pseudophrygia may be caused by a more severe seedling herbivory. In contrast to Centaurea, the highly palatable Arnica montana seedlings were completely consumed within a few days after transplantation, irrespective of age class and without any regeneration events, supporting previous hypotheses that mollusk herbivory is a limiting factor for the geographical range of Arnica montana. In general, the results confirm that a high sampling resolution in time is of great importance to detect agespecific mortality factors in plant population studies.

Patterns of Shrub Invasion into High Mountain Grasslands of the Northern Calcareous Alps, Austria

Both land use and expected climate change will probably cause range shifts of tree and shrub species in the European Alps. Attempts to predict the magnitude and direction of these processes will produce reliable results only if they consider both abiotic habitat conditions and biotic interactions. In this study we analyze recruitment patterns of Pinus mugo Turra in different grassland communities of the Northern Calcareous Alps, Austria. Pinus mugo is the most important invader of abandoned subalpine pastures in the area and the predominant woody plant at the current timberline. Results indicate strong dependence of colonization success on propagule pressure and differential invasibility of grassland types but only a marginal impact of local-scale site conditions, at least within the species’ current altitudinal distribution limits. Because the grassland matrix at and above the current treeline is dominated by a particularly invasible grassland type, a possible climate change–driven upward movement of Pinus mugo shrublands may take place quite rapidly. In contrast, encroachment on abandoned subalpine pastures is frequently delayed by competition with vigorous grassland canopies.

Growth responses of Matteuccia struthiopteris plants from northern and southern Norway exposed to different temperature and photoperiod treatments

Plants of the fern Matteuccia struthiopteris from northern and southern populations in Norway were studied in a phytotron. Relative growth rate (RGR), growth period, and sporophyll production were measured under different photoperiod (12–24 h) day‐length and temperature (9–21 °C) treatments. For the southern plants, there were no significant differences between the different light treatments, but for the northern plants there was a significant (p&lt;0.01) linear increase in the mean maximum RGR with increasing day‐length. Small, but statistically significant (p&lt;0.01) differences were found between northern and southern plants when the mean maximum RGR‐values were compared. When plants from different origin were exposed to different treatment, there were major differences between the populations in the production of sporophylls (p&lt;0.0001). Southern plants produced in average three times more sporophylls than the northern plants, and they had also higher proportions of fertile plants. Diurnal alternating temperature treatments gave no significant (p&gt;0.05) effect on the mean maximum RGR compared with constant temperatures, but they gave significantly higher production of sporophylls. In general, the northern plants had a higher temperature threshold (approximately 12 °C) for sporophyll production than the southern plants (approximately 9 °C). Plants exposed to 24 h with natural light were generally more often fertile than plants exposed to a shorter photoperiod. The mean maximum RGR‐values and time needed to develop the fronds at the 9 °C treatment were fairly equal to those found under natural conditions close to the altitudinal distribution limit of M.struthiopteris in W Norway. In general, the investigation showed that the applied temperature and light treatments affected sporophyll production more than vegetative growth.

Demographic Trends in the Cactaceae

I. Abstract Although our biological knowledge regarding cactus species is thorough in many areas, only in recent years have ecologists addressed their demographic behavior. Here we attempt a first review of the present knowledge on cactus demography, including an analysis of the published information on species with different growth forms and life-history traits. Our review shows that cactus distribution ranges are determined by environmental heterogeneity and by species-specific physiological requirements. Temperature extremes may pose latitudinal and altitudinal distribution limits. At a more local scale, soil properties dramatically affect cactus distribution. Most cacti show a clumped spatial distribution pattern, which may be the reflection of a patchy resource distribution within their heterogeneous environments. The association of cacti with nurse plants is another factor that may account for this aggregated distribution. Many cacti grow in association with these perennial nurse plants, particularl...

Betula ermanii, a Dominant Subalpine and Subarctic Treeline Tree Species in Japan: Ecological Traits of Deciduous Tree Life in Winter

Betula ermanii (Japanese mountain birch), a dominant tree species of the subalpine and subarctic treeline ecotones in East Asia, was investigated with respect to frost hardiness, bud phenology, and woody-tissue respiration above and below snow at the treeline on Mt. Fuji, Japan. On the Pacific-facing south slope, the minimum air temperature regime at 2450 m altitude is not harmful to the viability of previous year's shoots and emerging leaves. Betula ermanii will approach its upper distribution limit where the risk of spring frost damage in immature tissues interferes with the need for a minimum length of the growing season. In the cold Pacific winter climate of Japan, susceptibility of bursting buds and dehardened shoots to frost down to -7°C late in May is a major determinant for the species' altitudinal distribution limit at 2800 m altitude. It is concluded that two periods of minimum temperature affect the upper distribution of a deciduous broad-leaved tree species in temperate climates: (1) periods of subzero temperature which determine the occurrence of spring frost damage and affect the beginning of the growing season and (2) cool periods during the growing season that affect development and ripening of overwintering plant compartments.

Soil Temperatures near the Distribution Limit of the Mountain Birch (Betula pubescens ssp. czerepanovii): Implications for Seedling Nitrogen Economy and Survival

This paper (1) describes soil temperature conditions in an area close to the altitudinal and latitudinal distribution limit of the mountain birch, and (2) evaluates whether soil temperature is likely to impose a limit on nitrogen uptake and subsequent reductions in growth and survival. Soil temperature was monitored at two depths (–5 and –10 cm) during 3 yr in forested and nearby nonforested sites both at low altitude (ca. 400 m) and at forest line (ca. 650 m) in the Torneträsk area, northern Swedish Lapland (68°21′N, 18°49′E). The mean summer soil temperature was ca. +6 to +7°C and +5 to +7°C at –5 and –10 cm, respectively. Forest-line soils were on average 0.8°C warmer than valley soils. We found no statistically significant differences in soil temperature between sites colonized by mountain birch and nearby nonforested habitats. Given present soil temperatures, there is thus no reason why (mature) trees should not survive also on alpine and subalpine heaths currently not colonized by birch. However, relating these temperature recordings to experimentally determined relationships between soil temperature and seedling nitrogen (N) uptake, and between N uptake and survival, indicates that the mountain birch seedlings are unlikely to survive their first winter under soil temperature conditions normally prevailing in this area. Our analysis suggests that successful seedling establishment can be expected on disturbed sites when the growing season (15 June to 15 August) mean soil temperature is ca. 12°C or higher. In comparison, growing season soil temperature under undisturbed vegetation (at –5 cm) was on average ca 8.2°C during our 3 yr of soil temperature measurements. Air temperature during the same period was 1.1°C warmer than the average for the last 86 yr (1913–1998, 11.0 versus 9.9°C).