Subalpine Environments Research Articles

Effects of seed dispersal and microsite features on seedling establishment in New Zealand fleshy-fruited perennial mountain plants

Factors determining the effectiveness of animals as seed dispersers include effects of gut passage on seed viability and germination, the microsite into which seeds are deposited, and potential post‐dispersal impacts on establishment through predation and herbivory. We determined the relative importance of key pre‐ and post‐ seed dispersal processes for eight fleshy fruited montane and subalpine woody species that occur naturally in montane‐subalpine mixed shrub‐grassland in New Zealand's Southern Alps. A full factorial field experiment measuring the effects of fruit pulp removal, beneath‐canopy microsite (shade/open), vegetative competition (turf dug/not), and seed/seedling herbivore exclusion (caged/uncaged) on germination, seedling survival and height growth was carried out for 3.5 years. Only three species began germination within one year of sowing while all species experienced at least some germination by 3.5 years, showing the importance of long‐term studies in the subalpine environment. The shade treatment gave the highest germination success, seedling survival and seedling heights for seven of the eight species. Fruit pulp removal, herbivore exclusion and reduced competition were all retained in some final top models, but less often than shade and with smaller effects on means. The seed disperser fauna of New Zealand's mountain flora has transformed from predominantly native birds to exotic mammals over the past century. Birds and mammals likely move seeds to different microsites. Since shady microsites were more important than fruit pulp removal, any changes in plant recruitment caused by changing disperser faunas are likely to come from different seed deposition sites.

Effects of prescribed burning on soil organic C, aggregate stability and water repellency in a subalpine shrubland: Variations among sieve fractions and depths

Soil organic matter, aggregation and water repellency are relevant interrelated soil properties that can be affected by fire. The aim of this work was to analyse the effects of shrub prescribed burning for pasture reclamation on the soil aggregate stability, organic carbon and water repellency of different soil depths and aggregate sizes in a subalpine environment. Soil samples were collected from an area treated by an autumnal low-intensity prescribed fire in the Central Pyrenees (NE-Spain) at 0–1, 1–2, 2–3 and 3–5 cm depths just before and ~1 h, 6 months and 12 months after burning. Samples were separated as whole soil (<10 mm) and 6 sieve fractions, <0.25, 0.25–0.5, 0.5–1, 1–2, 2–4 and 4–10 mm. We analysed soil organic C (SOC), aggregate stability (AS) and soil water repellency (SWR). In the unburned samples, SOC and SWR were higher in the <0.25 to 2 mm sieve fractions than the 2 to 10 mm sieve fractions. Fire severely and significantly decreased the SOC content in the whole soil and the <0.25 mm fraction at 0–1 cm depth and in the 0.25–0.5 mm fraction at 0–2 cm depth. SWR was reduced by burning mainly at 0–1 cm depth for the whole soil and the <0.25 to 2 mm sieve fractions. Nevertheless, the AS of the 0.25–0.5 mm aggregates increased after fire, while the rest of the sieve fractions remained virtually unaffected. One year after the prescribed burning, SOC slightly increased and SWR recovered in the fire-affected fractions, while the AS for all aggregate sizes and depths showed a considerable decrease. The results suggest that the direct effects of burning are still present one year after burning, and the post-fire situation may pose an increased risk of soil loss. Furthermore, our results indicate that fine soil fractions are more likely to be affected by fire than coarser soil fractions and highly influence the whole soil behaviour.

Micro and material climate monitoring in wooden buildings in sub-Alpine environments

Wood is one of the most important construction materials and its use in building applications has further expanded in recent decades. In order to enable even more extensive and reliable use of wood in outdoor applications, factors affecting wood’s service life need to be understood. It is well known that fungal degradation of wood is predominantly affected by temperature (T) and moisture content (MC). In order to elucidate the influence of these two factors, long term monitoring of T, relative humidity (RH) and MC at four locations was carried out: a model house made of thermally modified wood in Mozirje (1), the WWII partisan hospital Franja (2), a hayrack in Pokljuka (3) and a house in the north of Slovenia in Vrba (4). The results clearly showed that fungal degradation of wood is influenced by MC and T. In addition, the influence of micro-climatic conditions on fungal decay was shown.

Meteorological and snow distribution data in the Izas Experimental Catchment (Spanish Pyrenees) from 2011 to 2017

Abstract. This work describes the snow and meteorological data set available for the Izas Experimental Catchment in the Central Spanish Pyrenees, from the 2011 to 2017 snow seasons. The experimental site is located on the southern side of the Pyrenees between 2000 and 2300 m above sea level, covering an area of 55 ha. The site is a good example of a subalpine environment in which the evolution of snow accumulation and melt are of major importance in many mountain processes. The climatic data set consists of (i) continuous meteorological variables acquired from an automatic weather station (AWS), (ii) detailed information on snow depth distribution collected with a terrestrial laser scanner (TLS, lidar technology) for certain dates across the snow season (between three and six TLS surveys per snow season) and (iii) time-lapse images showing the evolution of the snow-covered area (SCA). The meteorological variables acquired at the AWS are precipitation, air temperature, incoming and reflected solar radiation, infrared surface temperature, relative humidity, wind speed and direction, atmospheric air pressure, surface temperature (snow or soil surface), and soil temperature; all were taken at 10 min intervals. Snow depth distribution was measured during 23 field campaigns using a TLS, and daily information on the SCA was also retrieved from time-lapse photography. The data set (https://doi.org/10.5281/zenodo.848277) is valuable since it provides high-spatial-resolution information on the snow depth and snow cover, which is particularly useful when combined with meteorological variables to simulate snow energy and mass balance. This information has already been analyzed in various scientific studies on snow pack dynamics and its interaction with the local climatology or topographical characteristics. However, the database generated has great potential for understanding other environmental processes from a hydrometeorological or ecological perspective in which snow dynamics play a determinant role.

Diversity of winter photoinhibitory responses: a case study in co-occurring lichens, mosses, herbs and woody plants from subalpine environments.

Winter evergreens living in mountainous areas have to withstand a harsh combination of high light levels and low temperatures in wintertime. In response, evergreens can activate a photoprotective process that consists of the downregulation of photosynthetic efficiency, referred to as winter photoinhibition (WPI). WPI has been studied mainly in woody evergreens and crops even when, in many instances, other functional groups such as lichens or bryophytes dominate in alpine and boreal habitats. Thus, we aimed to (1) assess the occurrence of WPI within overwintering evergreens comprising woody species, herbs, mosses and lichens, (2) compare the recovery kinetics among those groups and (3) clarify the role of thylakoid proteins and pigments in both processes: WPI and recovery. With this aim, WPI was analyzed in 50 species in the field and recovery kineticcs were studied in one model species from each functional group. Results showed that high levels of WPI are much more frequent among woody plants than in any other group, but are also present in some herbs, lichens and mosses. Winter conditions almost always led to the de-epoxidation of the xanthophyll cycle. Nevertheless, changes in the de-epoxidation level were not associated with the activation/deactivation of WPI in the field and did not match changes in photochemical efficiency during recovery treatments. Seasonal changes in thylakoid proteins [mainly D1 (photosystem II core complex protein) and PsbS (essential protein for thermal dissipation)] were dependent on the functional group. The results highlight the diversity of physiological solutions and suggest a physical-mechanical reason for the more conservative strategy of woody species compared with other groups.

Mechanistic examination of causes for narrow distribution in an endangered shrub: a comparison of its responses to drought stress with a widespread congeneric species

The endangered status and narrow distribution in Syringa pinnatifolia , a sub-alpine shrub species, were primarily caused by its poor drought adaptation related to its lower degree of physiological adjustment despite its greater degree of morphological plasticity. Although deep rooting is usually considered a drought-tolerant trait, we found that Syringa pinnatifolia, a deep rooting and hydrotropic shrub, has a limited distribution in arid areas. To elucidate the mechanisms for its narrow distribution, we conducted two experiments to examine the physiological and morphological responses to water availability and heterogeneity in S. pinnatifolia and a widespread congeneric species, S. oblata. We measured gas exchange, water use efficiency, and plasticity index in plants of these two species grown at different levels of soil water regimes and in containers with patched water distribution. Our results showed that high photosynthetic capacity in the narrowly distributed S. pinnatifolia was an important factor enabling its survival in the harsh sub-alpine environment. High photosynthetic capacity in S. pinnatifolia, however, was obtained at the expense of high transpiratory water loss, resulting in lower integrative water use efficiency. Biomass allocation to roots in S. pinnatifolia increased by 73 % when soil water increased from 75 to 95 % field capacity, suggesting that S. pinnatifolia could be less competitive for above-ground resources under favorable water regimes. The horizontal root hydrotropism and vertical root hydrotropism of S. pinnatifolia in soil with patched water patterns were likely related to compensation for leaf water loss at low soil water level, indicating a limited capacity for homeostasis within the plant for water conservation and lower level of inherent drought-tolerance. In summary, greater degree of morphological plasticity but lower degree of physiological adjustment may be the main causes for the hydrotropism and narrow distribution of S. pinnatifolia in the sub-alpine habitats.

Towards understanding the fossil record better: Insights from recently deposited plant macrofossils in a sclerophyll-dominated subalpine environment

Accumulations of plant macrofossils in lake sediments and other sedimentary deposits are increasingly being used to refine our understanding of past vegetation history, ecological processes and related climate conditions. However, past vegetation studies based on the use of disarticulated plant structures need to consider the specific potential for fossilisation of different species and different plant organs. Such knowledge is available for many systems, but the taphonomy of sclerophyll floras is very poorly known.To provide understanding of the taphonomic processes affecting the representation of sclerophyllous plant species in fossil assemblages this study investigated the potential source vegetation of plant remains extracted from modern sediments of a subalpine lake in Tasmania, southernmost Australia. It was found that the vast majority of the leaf types represented in the sediments belong to broadleaf sclerophyllous species living in close proximity to the lake, although the representation of species was not related to their values of leaf mass per unit area.Additionally, a bias between the abundance of species in the standing vegetation and the number of leaves of the same species in sediments was observed. Thus, small-leaved shrub species, such as many members of Ericaceae, produce comparatively many more leaves and tend to be over-represented in sediments. In contrast, even though, large-leaved tree species such as Eucalyptus and Nothofagus are dominant in the standing vegetation, they produce substantially fewer foliar organs per ground area of vegetation.Accounting for these discrepancies, we developed an intrinsic representativity index that provides a more accurate picture of the relationship between the leaf assemblages incorporated in the sediments and the abundance of these species in the source vegetation.

Ericaceous plant-fungus network in a harsh alpine-subalpine environment.

In terrestrial ecosystems, plant species and diverse root-associated fungi form complex networks of host-symbiont associations. Recent studies have revealed that structures of those below-ground plant-fungus networks differ between arbuscular mycorrhizal and ectomycorrhizal symbioses. Nonetheless, we still remain ignorant of how ericaceous plant species, which dominate arctic and alpine tundra, constitute networks with their root-associated fungi. Based on a high-throughput DNA sequencing data set, we characterized the statistical properties of a network involving 16 ericaceous plant species and more than 500 fungal taxa in the alpine-subalpine region of Mt. Tateyama, central Japan. While all the 16 ericaceous species were associated mainly with fungi in the order Helotiales, they varied remarkably in association with fungi in other orders such as Sebacinales, Atheliales, Agaricales, Russulales and Thelephorales. The ericaceous plant-fungus network was characterized by high symbiont/host preferences. Moreover, the network had a characteristic structure called 'anti-nestedness', which has been previously reported in ectomycorrhizal plant-fungus networks. The results lead to the hypothesis that ericaceous plants in harsh environments can host unexpectedly diverse root-associated fungal taxa, constituting networks whose structures are similar to those of previously reported ectomycorrhizal networks but not to those of arbuscular mycorrhizal ones.

Subalpine conifers in different geographical locations host highly similar foliar bacterial endophyte communities.

Pines in the subalpine environment at Niwot Ridge, CO, have been found to host communities of acetic acid bacteria (AAB) within their needles. The significance and ubiquity of this pattern is not known, but recent evidence of nitrogen (N)-fixing activity in Pinus flexilis (limber pine) foliage calls for a better understanding of the processes that regulate endophytic communities in forest tree canopies. Here, to test if AAB dominate the foliar bacterial microbiota in other subalpine locations, we compared the 16S rRNA community in needles from P. flexilis and P. contorta (lodgepole pine) growing in the Eastern Sierra Nevada, CA, and Niwot Ridge, CO. AAB made up the majority of the bacterial community in both species at both sites. Multiple distinct AAB taxa, resolved at the single nucleotide level, were shared across host species and sites, with dominant OTUs identical or highly similar to database sequences from cold environments, including high altitude air sampled in Colorado, and the endosphere of Arctic plants. Our results suggest strong selection for community composition, potentially amplified by the long lifespan of individual Pinus needles, along with low dispersal constraints on canopy bacteria.

Targeted Capture Sequencing in Whitebark Pine Reveals Range-Wide Demographic and Adaptive Patterns Despite Challenges of a Large, Repetitive Genome.

Whitebark pine (Pinus albicaulis) inhabits an expansive range in western North America, and it is a keystone species of subalpine environments. Whitebark is susceptible to multiple threats – climate change, white pine blister rust, mountain pine beetle, and fire exclusion – and it is suffering significant mortality range-wide, prompting the tree to be listed as ‘globally endangered’ by the International Union for Conservation of Nature and ‘endangered’ by the Canadian government. Conservation collections (in situ and ex situ) are being initiated to preserve the genetic legacy of the species. Reliable, transferrable, and highly variable genetic markers are essential for quantifying the genetic profiles of seed collections relative to natural stands, and ensuring the completeness of conservation collections. We evaluated the use of hybridization-based target capture to enrich specific genomic regions from the 27 GB genome of whitebark pine, and to evaluate genetic variation across loci, trees, and geography. Probes were designed to capture 7,849 distinct genes, and screening was performed on 48 trees. Despite the inclusion of repetitive elements in the probe pool, the resulting dataset provided information on 4,452 genes and 32% of targeted positions (528,873 bp), and we were able to identify 12,390 segregating sites from 47 trees. Variations reveal strong geographic trends in heterozygosity and allelic richness, with trees from the southern Cascade and Sierra Range showing the greatest distinctiveness and differentiation. Our results show that even under non-optimal conditions (low enrichment efficiency; inclusion of repetitive elements in baits), targeted enrichment produces high quality, codominant genotypes from large genomes. The resulting data can be readily integrated into management and gene conservation activities for whitebark pine, and have the potential to be applied to other members of 5-needle pine group (Pinus subsect. Quinquefolia) due to their limited genetic divergence.

To what extent does vegetation composition and structure influence beetle communities and species richness in private gardens in New Zealand?

Private gardens comprise a large proportion of urban green space and can contain diverse and structurally complex vegetation, typically dominated by exotic species, but potentially providing resources for a diverse invertebrate fauna. We determined how much beetle diversity and community structure were influenced by vegetation composition and structure, native vegetation, garden land covers, and proximity and extent of neighbourhood green spaces in 55 gardens in Dunedin, New Zealand. We recorded 164 species from 29 families after 10 days of pitfall trapping; 68% native, 15% exotic. Beetle diversity exceeded that reported in other less modified New Zealand habitats, possibly due to high habitat heterogeneity at the scale of the garden but also the variety of habitats present at a larger scale but separated by relatively short distances within this small city and across a short altitudinal gradient, from sea level to sub-alpine environments. Number of shrubs (2–5m), woody plant density, and area of lawn and hedge influenced beetle richness, diversity and community structure, but explained <30% of variation between gardens. We found no effect of mean diversity of herbaceous vegetation in bed use, mowing and composting on diversity or community structure. Proximity to green space, woody plant diversity and vegetation structural complexity influenced beetle community composition, but correlations were weak. Although only 17% of all woody plants were native, most beetle species were native. With the exception of gardens that had very little vegetation, landscaping choices appeared to have little effect on beetle diversity and assemblage composition.

Cover as a simple predictor of biomass for two shrubs in Tibet

Knowledge of the quantitative relationship between plant cover and its corresponding biomass for shrubs is not well known, especially for those on the Tibetan Plateau. Based on investigations of 35 sites, 90 plots and 95 standard individuals for two typical shrub species (Rhododendron nivale Hook. f. and Sophora moorcroftiana (Benth.) Baker) across Tibet, we developed allometric models for biomass estimation from measurements of crown diameter and/or height. We found that the parameters of crown projection area (CPA), height and their product (volume) were all significantly (p<0.01) correlated with dry mass of different organs for both species at individual level. The CPA rather than volume best predicted aboveground dry mass. This is because that the bulk density declined significantly with increasing plant height, leading to the inappropriateness for plant height itself being employed as a parameter in biomass estimation, especially for shrubs in smaller size groups. At community level, cover was tightly correlated with the aboveground, belowground and total biomass (R2=0.97–0.99). Therefore, biomass for the two shrubs can be simply estimated by measuring plant cover, which enables rapid estimation of shrubland carbon stock at large scales by using satellite data and repeated experiments over time. This non-destructive method using cover to estimate shrub biomass can be applied not only in arid ecosystems but also in alpine or subalpine environment.

Evaluation of a moderate resolution imaging spectroradiometer triangle-based algorithm for evapotranspiration estimates in subalpine regions

The current study evaluates the application of a moderate resolution imaging spectroradiometer (MODIS) triangle-based method to estimate evapotranspiration (ET) in subalpine environments. Topographic corrections and improved soil moisture representation are applied to a previously developed net radiation (Rn) model and triangle algorithm to develop an 8-day average ET product based solely on satellite products. We evaluate modeled Rn and MODIS ET (MOD-ET) against ground-based values at four sites in the Sierra Nevada of northern California and also present a comparison between two monthly distributed ET datasets [operational simplified surface energy balance (SSEBop) and MODIS MOD16]. Modeled daily Rn results indicate a systematic underestimation (between −83 and −110 W/m2 bias). Consequently, Rn is bias-corrected before calculating MOD-ET. MOD-ET validation shows correlations between 0.15 and 0.45 with errors between 73 and 126 W/m2. MOD-ET and SSEBop ET report correlations of 0.36 and 0.20, respectively, on average, compared to ground-based monthly ET. MOD16 underestimates monthly totals, with bias values on the range of −14 to −144 W/m2. Semiarid conditions and scale differences between the MODIS pixel and station contribute to errors with respect to observation. Overall, MOD-ET provides reasonable ET estimates and may better capture temporal dynamics in environments undergoing chronic disturbance.

Can we discriminate snow avalanches from other disturbances using the spatial patterns of tree-ring response? Case studies from the Presidential Range, White Mountains, New Hampshire, United States

Dendrogeomorphology has been recognized as a useful tool to reconstruct past snow avalanche chronologies, especially in remote areas where archives are non-existent. In recent years, there have been a multiplicity of snow avalanche studies based on tree-ring analysis. Yet, the dendrogeomorphic procedure applied to snow avalanches still lacks consensus within the scientific community. This paper illustrates four issues regarding this method encountered on a dataset encompassing 293 trees sampled from 4 sites in the White Mountains (New Hampshire, United States). (1) Separating a sample in an upslope and downslope subgroup allowed to reconstruct a more thorough avalanche chronology. (2) On the other hand, a strong response at a site sheltered from any avalanche track was attributed to extreme snow loadings with a return period well above 100 years. (3) In addition to climatic disturbances, ecological disturbances such as windthrows can cause an anatomical response in the trees similar to snow avalanches. An avalanche track might act as a wind tunnel, making the underlying runout zone a suitable site to windfalls. Sampling in transects can assist in determining the limit between avalanche-related and wind-related disturbances. (4) Early-spring torrential floods and avalanche activities at a multi-process site exhibit distinct spatial patterns in the dendrogeomorphological response that allow discrimination between the two processes in the reconstruction of past chronologies. While the dendrogeomorphologist should be cautious of these issues, their acknowledgement is an opportunity to understand the interactions between the different ecological, climatic and geomorphological processes operating on the forested slopes in the alpine–subalpine environment.

Holocene soils/paleosols in the okstindan mountains, nordland: stratigraphy and extractable fe and al

A chronosequence of surface and buried soils in moraines and outwash, ranging in age from iddle to ate olocene, i.e., Little Ice Age, and forming under alpine and subalpine vegetation in the kstindan ountains of central‐north orway (66o ) (ksskolten) was studied to determine if topographic/stratigraphic setting, weathering characteristics, soil/paleosol properties, / analysis, and extractable and could be used to elucidate information on paleoenvironment and age. The geochemical data previously published and geological mapping by the orwegian eological urvey indicate a uniform parent material in these profiles. Slight geochemical anomalies of higher , h and r in organic‐rich horizons are related to vegetation and/or higher water content at various times, confirmed by extractable evidence. The data interpretation also shows that extractable , principally o, is useful in identifying previous perched water tables, possibly generated by permafrost. The activity ratio of o/d (oxalate to dithionite) and the ratio d/t (dithionite to total ) appear useful in distinguishing older from younger soils on the basis of the conversion of ferrihydrite to goethite+hematite. Pyrophosphate extracts, proved useful in determining movement of organically bound , and showed a pronounced difference between the alpine and subalpine environments. Oxalate‐extractable and dithionite‐extractable proved of little value in relative age determination, presumably because sodium dithionite does not extract all crystalline .

The influence of terracettes on the surface hydrology of steep-sloping and subalpine environments: some preliminary findings

Abstract. Alpine and mountain slopes represent important pathways that link high-altitude grazing areas to meadows and rangelands at lower elevations. Given the often acute gradients associated with such environments, they potentially represent highly efficient runoff conveyance routes that facilitate the downslope movement of runoff and associated material during erosion events. Many such slopes host series of small steps, or "terracettes". The juxtaposition of terracettes against the natural downslope flow path of non-complex slopes leads us to hypothesise that they may influence typical hillslope processes by intercepting or capturing surface runoff. Here we report preliminary results and some tentative conclusions from ongoing work to explore this possibility. Google Earth was used to initially identify a ca. 400 m2 well-developed terracette system situated on a west-facing slope with gradients ranging from 25 to 40° (46 to 84 %). A digital elevation model (DEM) of the terracettes was constructed using spatial data taken from a relevant section of topographic map. The DEM was then queried using a flow-accumulation algorithm and the results displayed in a geographic information system. The output data provided "proof of concept" that terracettes can capture surface runoff. The generation of empirical data from a series of rainfall/runoff simulations performed on the same section of terracettes supports this finding. Results from both work components indicate that sections of a terracette system may intercept runoff and could act as preferential flow pathways. By contrast, some sections appeared to act as depositional sites. We cautiously predict that these areas could act as retention zones for the temporary storage of runoff-associated substances. Greater understanding of the exact influence of terracettes on surface hydrology in steep-sloping and subalpine environments could benefit the future management of grazing and rangelands in such areas.

Chronosequence development and soil variability from a variety of sub-alpine, post-glacial landforms and deposits in the southeastern San Juan Mountains of Colorado

Surficial processes acting on post-glacial alpine and sub-alpine landscapes vary at small temporal and spatial scales and are thus often difficult to conceptualize in the context of large-scale landscape evolution models. Soils developing in this setting can thus provide valuable information about landform genesis, sedimentology and age. Relatively few post-glacial chronosequences have been examined in these settings however, particularly for the variety of landforms and parent materials that exist within alpine and sub-alpine environments. Here, we examine a chronosequence of relatively young, post-glacial landforms with varying parent materials and climate histories. We dug and described 39 soil pits in the upper Conejos River Valley of Colorado on a variety of deposits and landforms, including alluvial fans, terraces, colluvium, glacial till, and terminal moraines, and compared soil properties with radiocarbon ages from the area. Our results suggest that some typical chronosequence soil properties (e.g., pH, structure, color) do not correlate with time over short time scales. However, extractable iron ratios (Feo/Fed) show a relatively strong correlation with age across late-Pleistocene and Holocene time scales and maximum profile clay content shows a weak but statistically significant relationship with age. Both of these trends are stronger when examined across a single parent material. Differences in initial parent material texture and dust inputs seem to be the most significant complicating factors over post-glacial time scales. Soil property development through time is most inconsistent in cumulic alluvial fan soils. This observation may indicate that alluvial fans are more responsive to sub-basin scale processes as opposed to fluvial terraces that are more likely respond to processes active across the entire basin. These differences would explain why stratigraphically similar alluvial fans are mantled by soils with varying development. Nonetheless, horizonation, clay content, and extractable iron ratios provide a useful tool for correlating young deposits, assigning ages, and interpreting the geomorphic history of complex post-glacial environments.

A 10-year demographic study of a small mammal community in the Australian Alps

This paper describes a 10-year study of the community of two species of small rodents (Mastacomys fuscus, Rattus fuscipes) and one species of dasyurid marsupial (Antechinus swainsonii) in the subalpine zone of the Australian Alps. Each species exhibited differing life-histories with respect to population numbers, intra- and interannual fluctuations in numbers, reproduction, proportion of young in the population, winter survival, immigration and longevity. Of the two species of rodents, M. fuscus had the lowest population numbers, was the least fecund, had the highest rate of survival, and the smallest fluctuations in numbers. A. swainsonii was the least numerous species, and the winter die-off of males and the high fecundity of females resulted in much greater fluctuations in numbers than for either rodent. For all species, there were interannual variations in most demographic parameters, suggesting considerable flexibility in response to annual variations in the environment. None of the three species is known to hibernate, nor is there any evidence of cyclicity, as shown by some species of subarctic and arctic small mammals. Comparisons are made with subalpine small mammals in other parts of the world and the influence of the subalpine environment in determining population numbers is considered.

Introduction—Losing the High Ground: Rapid Transformation of Tropical Island Alpine and Subalpine Environments

Introduction—Losing the High Ground: Rapid Transformation of Tropical Island Alpine and Subalpine Environments

Total phosphorus reference condition for subalpine lakes: A comparison among traditional methods and a new process-based watershed approach

Different methods for estimating the total phosphorus (TP) reference conditions of lakes have rarely been compared. This work tests the uncertainty and accuracy of the most frequently used approaches (Morpho-edaphic index -MEI-, export coefficient, diatoms and pigment-inferred TP models) for 35 subalpine lakes. Furthermore, we propose a new process-based watershed approach that was tested on a subalpine environment and consists of combining a space for time substitution with a space for space substitution. The possible presence of uncontaminated or less contaminated environments inside or next to the watershed can be exploited by training a hydrological transport watershed model according to the uncontaminated conditions and then applying the calibration to the entire watershed, which reconstructs a natural or semi-natural TP load scenario. We found that the root mean square error (RMSE) for the MEI is 4 μg L−1. However, its application is limited for lakes that present with an alkalinity ≤1 meq L−1. For lakes with a higher alkalinity, we observed a loss of predictive capability that results from the lower solubility of phosphorus under conditions of high calcium content. The export coefficient model was applied with a mean export coefficient and presents similar prediction capabilities as the MEI. The chlorophyll-inferred TP model shows a higher uncertainty (RMSE = 8 μg L−1); however, it produced fewer underestimations and overestimations. With regards to the diatom-inferred TP model, we are only able to evaluate an uncertainty of 5 μg L−1 at the European level. Finally, the proposed process-based watershed approach adequately predicted the reference condition of the selected lake and had an uncertainty lower than the other methods (2 μg L−1). We conclude by revealing the potential and limitations of this approach in the field of ecological lake modelling more and more attracted by TP pristine load inputs in studies on the effects of climate change and eutrophication of lakes.