Southern Range Research Articles

Geodetic Extension Across the Southern Basin and Range and Colorado Plateau

AbstractRates of crustal deformation in the southern Basin and Range (SBR) and Colorado Plateau (CP) provinces are relatively low in the context of the Pacific‐North America plate boundary (PA–NA); however, the accumulation of small amounts of strain over long periods of time can lead to large earthquakes such as the Mw 7.5 1887 Sonoran earthquake in northern Mexico. SBR and CP rates of deformation are difficult to quantify due to a dearth of young faulting and seismicity. Moreover, strain accumulation and release related to the adjacent, more active San Andreas and Gulf of California fault systems to the west and southwest can mask the background strain rates associated with SBR and CP tectonics. With data from an enhanced continuous GPS network, we estimate crustal surface velocities of the SBR and CP, after removing coseismic and postseismic displacements, and elastic loading effects arising from major fault zones to the (south)west. We use cluster analysis and geologic data to separate the GPS velocity field into regions and calculate distinct block rotation and uniform strain rates for each region. We find the highest strain rate region includes southwestern Arizona; an area with sparse Quaternary faults, relatively low seismicity, and a relatively large discrepancy between geodetic and geologic rates of deformation. This anomalous strain rate may reflect residual, unmodeled PA‐NA strain seeping into the Arizona study area from the west. Alternatively, it may represent the potential for one or more rare, future, large‐magnitude earthquakes or indicate strain is being released through other process(es).

Medium‐term environmental changes influence age‐specific survival estimates in a salmonid population

Abstract Human‐induced environmental change is a major stressor on freshwater habitats that has resulted in the population declines of many freshwater species. Ontogenetic shifts in habitat use and associated (st)age‐specific requirements mean that impacts of environmental stressors can influence (st)ages in a population differently, and yet relatively few studies of freshwater fish populations account for their detail. We aimed to identify environmental and biotic factors affecting survival estimated for six age‐classes of a European grayling population in the River Wylye, UK over a 17‐year period. We used a Bayesian age‐structured state space model to estimate survival of grayling cohorts between subsequent life stages (eggs to age 5 adults) for 16 annual transitions (2003–2004 to 2018–2019), whilst accounting for imperfect sampling of the population. We quantified the effects of seasonal water flow and temperature, in‐stream habitat and prey resource, and potential competitors and predators on survival between subsequent life stages. We used Bayesian variable selection to gauge their relative importance on survival. Grayling abundances declined during the study period (>75% in all age‐classes), predominately driven by a loss of mature adults. Changes to seasonal flows negatively influenced their survival: increased days of summer low flow related to decreased survival of subadults and mature adults, and lower winter flows related to reduced recruitment of juveniles from eggs. Higher summer macrophyte cover negatively influenced juvenile and subadult survival and increasing days of high temperature in summer appeared detrimental to juvenile survival. Abundance of brown trout (a potential competitor and predator) did not negatively influence grayling survival. Our results reveal the implications of environmental change on a salmonid population, where recent low summer flows and high temperatures, and below average winter flows, have negatively influenced grayling survival. These conditions appear to be becoming more frequent and persistent in our study river, which is towards the species’ southern range limit, which could render the population vulnerable to climate change. Our study demonstrates how careful analysis of long‐term population monitoring and environmental datasets can identify factors affecting (st)age‐specific fish population dynamics, and when combined with local expertise, results in realistic mitigation proposals to promote wildlife population persistence.

Climate-induced range shifts shaped the present and threaten the future genetic variability of a marine brown alga in the Northwest Pacific.

Glaciation‐induced environmental changes during the last glacial maximum (LGM) have strongly influenced species' distributions and genetic diversity patterns in the northern high latitudes. However, these effects have seldom been assessed on sessile species in the Northwest Pacific. Herein, we chose the brown alga Sargassum thunbergii to test this hypothesis, by comparing present population genetic variability with inferred geographical range shifts from the LGM to the present, estimated with species distribution modelling (SDM). Projections for contrasting scenarios of future climate change were also developed to anticipate genetic diversity losses at regional scales. Results showed that S. thunbergii harbours strikingly rich genetic diversity and multiple divergent lineages in the centre‐northern range of its distribution, in contrast with a poorer genetically distinct lineage in the southern range. SDM hindcasted refugial persistence in the southern range during the LGM as well as post‐LGM expansion of 18 degrees of latitude northward. Approximate Bayesian computation (ABC) analysis further suggested that the multiple divergent lineages in the centre‐northern range limit stem from post‐LGM colonization from the southern survived lineage. This suggests divergence due to demographic bottlenecks during range expansion and massive genetic diversity loss during post‐LGM contraction in the south. The projected future range of S. thunbergii highlights the threat to unique gene pools that might be lost under global changes.

Assessing the impact of climate change – and its uncertainty – on snow cover areas by using cellular automata models and stochastic weather generators

Climate change will modify the spatiotemporal distribution of water resources in the future. Snow availability in alpine systems plays an important role for water dependent ecosystems, water demand supply, tourism, and hydropower. The assessment of the impact of climate change (and its uncertainty) on snow is a key subject in determining suitable adaptation strategies in these systems. In this paper, we propose a new methodology for assessing the impact of climate change on snow cover areas (SCAs). We have developed the Monte Carlo method analysis to combine several approaches to generate multiple input series and propagate them within a previously calibrated SCA cellular automata model. This generates potential future local scenarios from regional climate models. These scenarios are used to generate multiple series by using a stochastic weather generator. The methodology also includes an approach to correct the outputs bias of the stochastic weather generators when it is needed. Finally, the historical and the corrected multiple future weather series are used to simulate the impact on the SCA by using a cellular automata model. It is a novel approach that allows us to quantify the impact and uncertainty of climate change on the SCA. The methodology has been applied to the Sierra Nevada (southern Spain), which is the most southern alpine mountain range in Europe. In the horizon 2071–2100, under the RCP 8.5 emission scenario, we estimate mean reductions of SCA that will move from 42 to 66% from December to February. The reductions are higher for the rest of the year (from March to May reductions of between 47 and 95% and from September to November reductions of between 54 and 100%). These SCA changes may be roughly equivalent to an elevation shift of snow of around 400 m.

New records and southern range extension of the Annamite striped rabbit Nesolagus timminsi in Vietnam

Abstract The Annamite striped rabbit Nesolagus timminsi is a little-known and Endangered lagomorph endemic to the Annamites ecoregion of Vietnam and Laos. The species’ known distribution extends from the northern to central Annamites. Here, we report the first records of the species from the southern Annamites. We recorded camera-trap photographs of Annamite striped rabbit in Bidoup – Nui Ba National Park, located in Lam Dong province, Vietnam. The photographs represent the first records of the species from the southern Annamites, and a significant southern range extension. We discuss the implications of this finding for Annamite striped rabbit conservation.

Demographic and ecogeographic factors limit wild grapevine spread at the southern edge of its distribution range.

The spatial distribution of plants is constrained by demographic and ecogeographic factors that determine the range and abundance of the species. Wild grapevine (Vitis vinifera ssp. sylvestris) is distributed from Switzerland in the north to Israel in the south. However, little is known about the ecogeographic constraints of this species and its genetic and phenotypic characteristics, especially at the southern edge of its distribution range in the Levant region. In this study, we explore the population structure of southern Levantine wild grapevines and the correlation between demographic and ecogeographic characteristics. Based on our genetic analysis, the wild grapevine populations in this region can be divided into two major subgroups in accordance with a multivariate spatial and ecogeographical clustering model. The identified subpopulations also differ in morphological traits, mainly leaf hairiness which may imply adaptation to environmental stress. The findings suggest that the Upper Jordan River population was spread to the Sea of Galilee area and that a third smaller subpopulation at the south of the Golan Heights may represent a distinguished gene pool or a recent establishment of a new population. A spatial distribution model indicated that distance to water sources, Normalized difference vegetation index, and precipitation are the main environmental factors constraining V. v. sylvestris distribution at its southern distribution range. These factors in addition to limited gene flow between populations prevent further spread of wild grapevines southwards to semi‐arid regions.

The importance of determining species sensitivity to environmental change: a tree frog example

AbstractConservation schemes typically place species into categories, ranging roughly from rare to common or from vulnerable to least concern. Although a species may not be categorized as rare or vulnerable, it still may be sensitive to environmental change and, therefore, at risk of decline. To illustrate the importance of determining species sensitivity, we documented the relative sensitivities of four species of tree frogs, none of which have been designated particularly rare or vulnerable, to environmental change. Our research was conducted in central Florida, where prior research had suggested that Dryophytes femoralis and Dryophytes gratiosus were more sensitive to environmental change than Dryophytes cinereus and Dryophytes squirellus. A comparison of species characteristics and a field study of local abundances supported the dichotomy. Particularly, important environmental factors affecting the two more‐sensitive species adversely appear to be habitat selectivity, at a smaller scale, and nearness to the species’ southern range limits, at a larger scale. We suspected that one of the more‐sensitive species, D. gratiosus, is particularly sensitive to environmental change and that the cause is related to reproduction and/or growth. A series of laboratory analyses suggested strongly that the realized production of adults was less for D. gratiosus than for D. femoralis. Despite their identical placement in categorization schemes, the four species exhibited substantial differences in sensitivity to environmental change. A strong case can be made that the degree of sensitivity of D. gratiosus warrants increased conservation attention for the species. Our results indicate the potential value of field work and the generation of species‐specific information in improving categorization schemes, of broadening the categorization criteria typically employed, to accommodate sensitivity to environmental change, and of considering geographical scale in categorization schemes more than is done at present.

ClimPlant: Realized climatic niches of vascular plants in European forest understoreys

AbstractMotivationDetailed knowledge on the climatic tolerances of species is crucial to understand, quantify and predict the impact of climate change on biodiversity and ecosystem functions. However, quantitative data are limited; often, only expert‐based qualitative estimates are available. With the ClimPlant database, we capitalize on the link between species distribution ranges and macroclimate to infer the realized climatic niches of 968 European forest plant species.Main types of variables containedThe ClimPlant database contains information on the distribution of monthly, growing‐season and annual mean, minimum and maximum temperature and total precipitation within the distribution range of 968 European forest plants.Spatial location and grainEurope in 10 arc‐min grid cells; the study area has been cropped rectangularly at 15° W (Atlantic Ocean), 60° E (Ural Mountains), 25° N (Sahara) and 75° N (Arctic Ocean).Time period and grainThe distribution ranges of forest plant species are based on two renowned distribution atlases. The monthly mean, minimum and maximum temperature and precipitation between 1970 and 2000 were extracted from WorldClim v.2.Major taxa and level of measurementNine hundred and sixty‐eight vascular plant species of European forests, with taxonomy following the Euro+Med PlantBase nomenclature .Software formatData in 56 CSV files, with 1,000 values for monthly, growing season and annual observations of mean, minimum and maximum temperature and precipitation in the distribution range for every species. One summary CSV file with summary statistics (mean, median, fifth and 95th percentile), for every species, of each climatic variable, together with seven key geographical descriptors: area of the distribution range, latitude and longitude of the centroid, and northern, eastern, western and southern range limits within the study area.

New stygofauna from Texas, USA: three new species of Parabathynellidae (Crustacea: Bathynellacea)

ABSTRACT Three new species of Parabathynellidae (Crustacea: Bathynellacea) are described using morphological and molecular data, and additional populations identified as Texanobathynella cf. bowmani are placed within a molecular phylogeny for the group. The finding of Montanabathynella pecosensis sp. nov. entails a southern range expansion of over 1500 km for the genus, previously thought to be restricted to Montana, USA. Montanabathynella pecosensis sp. nov. displays a unique combination of morphological features, including eight main teeth on the labrum; four and six teeth on the pars incisiva and pars molaris of the mandible, respectively; eight teeth on the distal endite of MxI; epipod present on ThII and III; four teeth on the first segment of female ThVIII; and an unpronounced anal operculum. The other two new species described here belong to the genus Texanobathynella Delamare Deboutteville et al., 1975, previously consisting of only two species. Both species, Texanobathynella aaronswinki sp. nov and T. coloradoensis sp. nov., display combinations of morphological features distinct from the other two previously known species of the genus. Mitochondrial (COI) and nuclear (18S) markers support the validity of the new species and enable us to place them, along with T. cf. bowmani, within a larger phylogenetic framework of the Parabathynellidae.

Voluminous Paleogene volcanism in the southern Mesa Central, Mexico: Unravelling the fissure-fed origin of rhyolitic ignimbrites of the Villa Garcia-Loreto Volcanic Complex

The southern portion of the Mesa Central (MC) physiographic province is covered by numerous Oligocene to Miocene volcanic successions that are part of the Sierra Madre Occidental silicic large igneous province. The MC merges with the Sierra Madre Occidental and the southern Basin and Range extensional province. The voluminous Villa Garcia-Loreto Volcanic Complex (VGLVC) is located in the southern portion of the MC and consists of predominantly rhyolitic lava flows, and voluminous products of explosive rhyolitic volcanism, mainly as lava-like to rheomorphic ignimbrite sheets. The volcanism in the area appears in two events, first, at 60.4 ± 0.3 Ma (K–Ar whole-rock age) with the fissure-fed eruption of an andesitic lava and second, with the fissure-fed eruption of two densely-welded, crystal-poor ignimbrites at 31.59 ± 0.14 Ma and 28.66 ± 0.07 Ma (40Ar–39Ar sanidine ages). Chondrite-normalized rare earth element patterns and primitive mantle normalized multi-element patterns show enrichment in light rare earth elements (LREE) and high field strength elements (HFSE). Geochemical analysis and mineral chemistry show that the andesitic magmas were generated by partial melting of the uppermost mantle in a subduction-related setting and ascended directly through the brittle crust and erupted along N-S trending faults. Rhyolitic magmas were generated by partial melting of the lower crust in an intra-plate and extensional setting, associated with an intense phase of the southern Basin and Range extension. During the ascent and storage in a shallow magma chamber fractional crystallization of mainly feldspars and pyroxene was the major process taking place in the evolution of the magma. Geophysical results suggest that the volcanic rocks of the VGLVC were originated by fissure-fed eruptions associated with the Loreto Graben fault. The major Basin and Range faults locally reach a depth of 7 km and trending in NNW-SSE direction. The combined results show that the Basin and Range extension favored the formation, ascent, and eruption of rhyolitic and andesitic magmas in the southern MC.

Gas Exchange, Water Use Efficiency, and Biomass Partitioning among Geographic Sources of Acer saccharum Subsp. saccharum and Subsp. nigrum Seedlings in Response to Water Stress.

Responses to water stress were measured for sugar maple (Acer saccharum subsp. saccharum Marshall) sources from Oklahoma (Caddo sugar maple), Missouri, Tennessee, Ontario, and a black maple (Acer saccharum subsp. nigrum F. Michx.) source from Iowa. Seedling sources were selected for differences in temperature and precipitation of their geographic origins. Seedlings were preconditioned through moist (watered daily) or dry (watered every 4–7 days) cycles and then exposed to prolonged water stress. As water stress increased, dry preconditioned 17-week-old sugar maple seedlings from Oklahoma, Missouri, and Tennessee, sources from warmer, and/or drier climates with greater restrained photosynthesis, stomatal conductance, and water use efficiency than those from cooler and moister climates. Under imposed water stress, the Ontario and Iowa sourced seedlings increased their root to shoot ratios and decreased their specific leaf area, mechanisms for drought avoidance. However, no corresponding changes in these values occurred for Oklahoma, Missouri, and Tennessee sources and for the variable of leaf wilting across all sources. Results from this study suggest greater tolerance of water stress in the Oklahoma, Missouri, and Tennessee ecotypes from the western and southern range of sugar maple resulted primarily with water use efficiency (WUE) rather than other water stress coping mechanisms. Findings from this study provide evidence to support selection of sugar maples sources for forestation.

Regional differences in rapid evolution during severe drought.

Climate change is increasing drought intensity, threatening biodiversity. Rapid evolution of drought adaptations might be required for population persistence, particularly in rear‐edge populations that may already be closer to physiological limits. Resurrection studies are a useful tool to assess adaptation to climate change, yet these studies rarely encompass the geographic range of a species. Here, we sampled 11 populations of scarlet monkeyflower (Mimulus cardinalis), collecting seeds across the plants’ northern, central, and southern range to track trait evolution from the lowest to the greatest moisture anomaly over a 7‐year period. We grew families generated from these populations across well‐watered and terminal drought treatments in a greenhouse and quantified five traits associated with dehydration escape and avoidance. When considering pre‐drought to peak‐drought phenotypes, we find that later date of flowering evolved across the range of M. cardinalis, suggesting a shift away from dehydration escape. Instead, traits consistent with dehydration avoidance evolved, with smaller and/or thicker leaves evolving in central and southern regions. The southern region also saw a loss of plasticity in these leaf traits by the peak of the drought, whereas flowering time remained plastic across all regions. This observed shift in traits from escape to avoidance occurred only in certain regions, revealing the importance of geographic context when examining adaptations to climate change.

Comparisons of the Spatial Extent of Eastern U.S. Tree Species between Expert-Drawn Little’s Range Map and Forest Inventory and Analysis

Elbert Little’s tree species range maps and Forest Inventory and Analysis (FIA) are two important data sources used to create historic and current tree species distributions. Yet, explicit comparisons do not exist between the two data sets. We developed a statistical procedure to compare forty-seven tree species of expert-drawn Little’s range maps to point-to-grid maps of FIA in terms of their northern and southern range extent and range porosity. First, we computed varying percentiles of species occurrence for northern and southern ranges using empirical cumulative distribution functions. Then, we evaluated distributional differences between the maps using the nonparametric two-sample Kolmogorov–Smirnov and Anderson–Darling statistics and compared these results to the conventional Jaccard dissimilarity index. Our methods found map dissimilarities near northern and southern range extents and range porosity that conventional methods failed to detect. We also found that map disparity is related to an untraceable source of errors related to abundance of species for Little’s range map and, to a lesser extent, forest area changes over the forty years. We conclude that Little’s range map has an overall tendency to draw generous range extents with little emphasis on range porosity for abundant species compared to FIA.

Does the Breeding Biology of the Eurasian Stone-Curlew Burhinus oedicnemus in South-Western Morocco Differ between Grazed Steppe and Irrigated Farmland?

Birds associated with steppe and pseudosteppe habitats are one of the most threatened avian communities in Europe, given their recent decline due to agriculture intensification and land abandonment. Large-scale conversion of natural and rural areas into irrigated farmlands is ongoing in North Africa, but the effects of this habitat modification on steppe bird species are not investigated. In this study, we investigated the breeding biology of the Eurasian Stone-curlew nesting in grazed steppes and irrigated farmlands in south-western Morocco. Breeding data were collected during 2017 and 2018 breeding seasons on 59 nests. Egg volume was significantly higher in grazed steppes than in irrigated farmlands (37.3 ± 2.30 cm3 vs 35.1 ± 2.11 cm3, average ± SD), possibly due to greater food availability in the former habitat. On the other hand, daily nest survival over the incubation period did not differ between habitats and it was quite high (0.85 [95% CI: 0.71–0.93]) also when compared to the data available for other regions. These results suggest that birds nesting in protected areas characterized by traditional pastoralism might find better conditions for reproduction which allow them to lay larger eggs. In addition, the ongoing process of agricultural intensification in the area does not seem to affect the likelihood of nest failure. Our data add to the few available pieces of evidence regarding the effect of breeding habitat on the reproductive biology of the Stone-curlew in the southern range of its distribution. Further data are needed in order to understand the conservation implication of our findings and, in particular, how the observed variability of egg size might affect chick quality and survival.

Using growth rates and otolith shape to identify the population structure of Umbrina canosai (Sciaenidae) from the Southwestern Atlantic

ABSTRACT Identifying populations and establishing the connectivity between neighbouring stocks are central issues for the assessment and management of coastal marine fish species. In this paper, we analysed the population structure of the demersal sciaenid argentine croaker Umbrina canosai, endemic in the warm, temperate southwestern Atantic between southeastern Brazil (SE) and Argentina, by combining two phenotypic techniques: otolith shape analysis and fish growth rate. Three otolith morphotypes were consistently identified, one in the northern latitudinal range in SE, and two in the southern range of the species from southern Brazil to Argentina. Two stocks with differences in growth rate were identified, one with a significantly smaller asymptotic length in the northern range (L ∞ = 340.08; k = 0.267; t0 = −2.177) and the second in the southern range (L ∞ = 425.08; k = 0.236; t0 = −2.46), where no growth differences were observed between fishes with the two otolith morphotypes. Although genetically U. canosai can be considered to form a single panmictic population, growth and otolith shape indicate that there are two different stocks, one in southeastern Brazil and another in the southern distribution, confirming previous parasitological studies. The difference in otolith morphotypes in the southern range suggests that two subpopulations share the same reproductive grounds, although probably feed in different locations.

Seven decades of southern range dynamics of Canada lynx.

The range of the Canada lynx (Lynx canadensis) has contracted substantially from its historical range. Using harvest records, we found that the southern range of the lynx in Ontario in the late 1940s collapsed and then, in a short period of time, increased to its largest extent in the mid‐1960s when the lynx range spread south of the boreal forest for a decade. After this expansion, the southern range contracted northwards beginning in the 1970s. Most recently, there has been a slight expansion between 2010 and 2017. We have attributed these dynamics on the southern range periphery to the fluctuation of the boreal lynx population in the core of the species' range. In addition, connectivity to boreal lynx populations and snow depth seemed to condition whether the lynx expanded into an area. However, we did not find any evidence to suggest that these changes were due to anthropogenic landscape disturbances or competition. The boreal lynx population does not reach the peak abundance it once did, without which we would not expect to see large expansions of the southern lynx range as in the mid‐1960s. Our results suggest that the southern lynx range in Ontario has been driven by the magnitude of the boreal lynx population cycle, connectivity to the boreal forest, and snow conditions. Future persistence of lynx in the southern range periphery will likely depend on dynamics in the range core.

Life-history theory provides a framework for detecting resource limitation: a test of the Nutritional Buffer Hypothesis.

For ungulates and other long-lived species, life-history theory predicts that nutritional reserves are allocated to reproduction in a state-dependent manner because survival is highly conserved. Further, as per capita food abundance and nutritional reserves decline (i.e., density dependence intensifies), reproduction and recruitment become increasingly sensitive to weather. Thus, the degree to which weather influences vital rates should be associated with proximity to nutritional carrying capacity-a notion that we refer to as the Nutritional Buffer Hypothesis. We tested the Nutritional Buffer Hypothesis using six moose (Alces alces) populations that varied in calf recruitment (33-69 calves/100 cows). We predicted that populations with high calf recruitment were nutritionally buffered against the effects of unfavorable weather, and thus were below nutritional carrying capacity. We applied a suite of tools to quantify habitat and nutritional condition of each population and found that increased browse condition, forage quality, and body fat were associated with increased pregnancy and calf recruitment, thereby providing multiple lines of evidence that declines in calf recruitment were underpinned by resource limitation. From 2001 to 2015, recruitment was more sensitive to interannual variation in weather (e.g., winter severity, drought) and plant phenology (e.g., duration of spring) for populations with reduced browse condition, forage quality, and body fat, suggesting these populations lacked the nutritional reserves necessary to buffer demographic performance against the effects of unfavorable weather. Further, average within-population calf recruitment was determined by regional climatic variation, suggesting that the pattern of reduced recruitment near the southern range boundary of moose stems from an interaction between climate and resource limitation. When coupled with information on habitat, nutrition, weather, and climate, life-history theory provides a framework to estimate nutritional limitation, proximity to nutritional carrying capacity, and impacts of climate change for ungulates.

Temporal and spatial variation in population structure among brooding sea stars in the genus Leptasterias.

Temporal genetic studies of low‐dispersing organisms are rare. Marine invertebrates lacking a planktonic larval stage are expected to have lower dispersal, low gene flow, and a higher potential for local adaptation than organisms with planktonic dispersal. Leptasterias is a genus of brooding sea stars containing several cryptic species complexes. Population genetic methods were used to resolve patterns of fine‐scale population structure in central California Leptasterias species using three loci from nuclear and mitochondrial genomes. Historic samples (collected between 1897 and 1998) were compared to contemporary samples (collected between 2008 and 2014) to delineate changes in species distributions in space and time. Phylogenetic analysis of contemporary samples confirmed the presence of a bay‐localized clade and revealed the presence of an additional bay‐localized and previously undescribed clade of Leptasterias. Analysis of contemporary and historic samples indicates two clades are experiencing a constriction in their southern range limit and suggests a decrease in clade‐specific abundance at sites at which they were once prevalent. Historic sampling revealed a dramatically different distribution of diversity along the California coastline compared to contemporary sampling and illustrates the importance of temporal genetic sampling in phylogeographic studies. These samples were collected prior to significant impacts of Sea Star Wasting Disease (SSWD) and represent an in‐depth analysis of genetic structure over 117 years prior to the SSWD‐associated mass die‐off of Leptasterias.

Distribution, ecology, morphology and reproductive biology of Sphagnum majus in the south of its range (Hautes-Fagnes, Belgium)

Sphagnum majus (Russ.) C. Jens. is a rare dioecious peat moss in its southern range, and in particular, in southern Belgium (Wallonia). Based on original field observations and revision of herbarium material, the distribution of this species in Wallonia is revised and updated. Although it is the most common of the two subspecies, S. majus subsp. norvegicum is reported from Belgium for the first time.The two subspecies are easily differentiated in the field based on macroscopic features, but high levels of variability of microscopic features were observed between the two subspecies in some populations. Sphagnum majus has a very specific niche and is nearly restricted to lithalsas, which are threatened ecological environments in the context of global climatic warming. In Wallonia, male plants of Sphagnum majus subsp. norvegicum are more common than in northern Europe. Capsule production was, however, observed at only one location.

The growth responses of Araucaria angustifolia to climate are adjusted both spatially and temporally at its northern distribution limit

Temporal instability and spatial inconsistency in tree growth sensitivity to climate have been reported, but little attention has been given to tropical species. Araucaria angustifolia (Bertol.) Kuntze. (Araucariaceae) is a critically endangered South American subtropical and tropical conifer. It offers the potential to evaluate alterations in tree growth responses as it is climate-sensitive and presents a core zone of distribution in the Brazilian meridional highlands (with small disjunct patches occurring in its most southern and northern ranges). Previous dendrochronological studies in the central and most southern distribution range of A. angustifolia showed different climate-related growth responses, which raises the question of whether the growth responses of A. angustifolia to climate are consistent over space and stable over time at the species' northern distribution limit? We developed well-replicated tree-ring chronologies for A. angustifolia at the species' northern distribution limit, examined its growth dynamics, and evaluated climate-growth relationships. The growth patterns of A. angustifolia allowed the synchronization of its tree ring time-series and the construction of two tree-ring width chronologies (at Brejo da Lapa – BL and Vale das Araucárias – VA) of 55 years and 171 years respectively. The chronologies demonstrated stable and robust signal strengths. Climate-growth response analyses indicated significant positive correlations of the VA chronology with precipitation variables, and with temperature variables in the BL chronology. Different diametric growth patterns were detected between BL and VA. We observed consistent reductions of growth responses to the climate in recent decades. Forest structure and dynamics, disturbance regime, local environmental factors, and climate change could generate physiological alterations and explain variations in A. angustifolia’s growth responses and increments. The species showed different sensitivities to climatic factors both spatially and temporally, and different growth patterns at its northern distribution limit.