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Life-history traits have been described disproportionately for temperate-breeding birds. Efforts to conserve global biodiversity require a more holistic understanding of avian life-history theory across biomes and geographic locations. In this account, we present the first detailed description of the breeding biology of the Bornean Stubtail (Urosphena whiteheadi). We discuss the stubtail's breeding strategies in the context of life-history theory and contrast them with those of 4 other members of the same family breeding at higher latitudes and lower elevations. The Bornean Stubtail is a tropical montane passerine belonging to the Old World Cettiidae family and endemic to the island of Borneo. Compared to other Cettiidae warblers, the Bornean Stubtail has a small clutch of 2 eggs and a long incubation period of 23.0 ± 0.10 d. At our site, their open-cup nests were constructed of moss and placed on or near the ground on vertical features in rainforest understory. The nests experienced a daily survival rate of 0.939 ± 0.006 and daily predation rate of 0.054 ± 0.006. Mean fresh egg mass was 1.87 ± 0.012 g. Egg-laying began in mid-February and continued into May. The number of active nests increased until mid-March at which point it remained relatively consistent until mid-May when it began to taper off. Nest attentiveness during incubation was low with a very long off-bout of ∼7 h every day that decreased to ∼4 h later in incubation, explaining the species' long incubation period. In contrast, nestling provisioning rates increased steadily over the nestling period (mean 12.53 ± 0.24). Nestling growth followed a logistic trend commonly seen in passerines, and near-adult sizes were reached by fledging. Rasgos de historia de vida han sido descritos desproporcionalmente en aves de reproducción en sitios templados. Los esfuerzos de conservación de la biodiversidad global requieren un entendimiento más holístico de las teorías de historias de vida a través de distintos biomas y localidades geográficas. Por ello, presentamos la primera descripción detallada de la biología reproductiva de la buscarla-colicorta Urosphena whiteheadi. Discutimos las estrategias reproductivas de la colicorta en el contexto de la teoría de historias de vida y las contrastamos con otros 4 miembros de esa familia que se reproducen en grandes alturas y elevaciones más bajas. La buscarla-colicorta Urosphena whiteheadi es un ave paserina de montaña tropical que pertenece a la familia Cettidae del Viejo Mundo y que es endémica de la isla de Borneo. Comparada con otras buscarlas-colicortas de la familia Cetiidae, la buscarla-colicorta Urosphena whiteheadi tiene unas puestas pequeñas de 2 huevos y un periodo largo de incubación de 23 ± 0.1 días. En nuestro sitio, los nidos de copa abierta fueron construidos con musgo y colocados en o cerca del suelo en elementos verticales en el sotobosque forestal. Los nidos experimentaron una tasa diaria de supervivencia de 0.939 ± 0.006 y una depredación diaria de 0.054 ± 0.006. La masa promedio de huevos fue de 1.87 ± 0.012 g. La puesta de huevos inició a mediados de febrero y continuó hasta mayo. El número de nidos activos aumentó hasta mediados de marzo, luego se mantuvo relativamente contante hasta mediados de mayo cuando empezó a disminuir. La atención al nido durante la incubación fue baja con largos periodos de ausencia ∼7 h cada día que luego disminuyeron a ∼4 h posteriormente durante la incubación, lo que explica el largo periodo de incubación de la especie. En contraste, las tasas de aprovisionamiento del nido aumentaron constantemente durante el periodo de incubación (promedio 12.53 ± 0.24). El crecimiento del polluelo siguió una tendencia logística típicamente vista en aves paserinas y tallas cercanas a las de adulto fueron alcanzadas por los volantones. Palabras clave: ave paserina de bosque tropical, cambio climático, conteo de especies, grandes alturas, historia de vida, periodo de incubación, tamaño de puesta. [ABSTRACT FROM AUTHOR]

Montane landscapes present an array of abiotic challenges that drive adaptive evolution amongst organisms. These adaptations can promote habitat specialisation, which may heighten the risk of extirpation from environmental change. For example, higher metabolic rates in an endothermic species may contribute to heightened cold tolerance, whilst simultaneously limiting heat tolerance. Here, using the climate-sensitive American pika (Ochotona princeps), we test for evidence of intraspecific adaptive variation amongst environmental gradients across the Intermountain West of North America. We leveraged results from previous studies on pika adaptation to generate a custom nuclear target enrichment design to sequence several hundred candidate genes related to cold, hypoxia and dietary detoxification. We also applied a 'genome skimming' approach to sequence mitochondrial DNA. Using genotype-environment association tests, we identified rare genomic variants associated with elevation and temperature variation amongst populations. Amongst mitochondrial genes, we identified intraspecific variation in selective signals and significant changes to the amino acid property equilibrium constant, which may relate to electron transport chain efficiency. These results illustrate a complex dynamic of adaptive variation amongst O. princeps where lineages and populations have adapted to unique regional conditions. Some of the clearest signals of selection were in a genetic lineage that includes pikas of the Great Basin region, which is also where recent localised extirpations have taken place and highlights the risk of losing adaptive alleles during environmental change., (© 2024 The Author(s). Molecular Ecology published by John Wiley & Sons Ltd.)

Espeletia saboyana, a new species from Páramo de Saboyá, Boyacá department, Colombia, is described and illustrated. It is a caulescent rosette up to 5 m tall, with whitish-cinereous appearance, sessile leaves with elliptic laminae, cymose capitulescences with aphyllous unbranched portion and 3–5 capitula, 5–13 phyllaries, the external ones 17.4–26.0 mm long, 49–92 ray florets 13.0–18.4 mm long, and 162–347 disc florets 8.2–12.2 mm long. Espeletia saboyana is similar to E. incana, but with longer laminae, bigger foliar area, and fewer ray floret series. It is also similar to E. murilloi, but with longer ray tubes, ray paleae, disc corollas, disc styles, disc anther appendages, and disc paleae. In addition, E. saboyana is distributed allopatrically in regard to E. incana and E. murilloi. This species is informally proposed to be listed as IUCN Critically Endangered (CR), since it is restricted to a single population with extent of occurrence = 1.83 km2 and area of occupancy = 0.48 km2. Besides, this population is severely fragmented into 40–50 demes, the largest one covering only 34,000 m2. Most demes are found in humid soils and wetlands submitted to continuous habitat deterioration as water is drained for use in agriculture. Espeletia saboyana is rare or absent in these newly drained areas, which are either colonized by other species that thrive on drier soils or transformed into pastures for cattle grazing. Furthermore, analyses of size class distributions show that recruitment rates of E. saboyana are significantly lower in small demes, which, if not reversed, can further reduce population size in the near future. [ABSTRACT FROM AUTHOR]

Despite the importance of headwater catchments for the water supply of the western United States, these regions are often poorly understood, particularly with respect to quantitative understanding of evapotranspiration (ET) fluxes. Heterogeneity of land cover, physiography, and atmospheric patterns in these high‐elevation regions lead to difficulty in developing spatially‐distributed characterization of ET. As the largest terrestrial water flux behind precipitation, ET represents a significant fraction of the water budget for any watershed. Likewise, groundwater is the largest available freshwater store and has been shown to play a large role in the water balance, even in headwater systems. Using an eddy covariance tower in the East River Catchment, a Colorado River headwaters basin, we estimated water and energy fluxes in high‐elevation, complex systems to better constrain ET estimates and calculate overall water and energy budgets, including losses from groundwater. We used the eddy covariance method to estimate ET from years 2017 through 2019 at a saturated, riparian end‐member site. Owing to complexities in near surface atmospheric structure such as stable boundary layers over snowpack and shallow terrain driven flow from surrounding landscape features, energy flux and ET estimates were limited to the warm season when energy closure residuals from the eddy‐covariance system were reliably less than 30%, a threshold commonly used in eddy covariance energy flux estimation. The resulting ET estimations are useful for constraining water budget estimates at this energy‐limited site, which uses groundwater for up to 84% of ET in the summer months. We also compared East River ET magnitudes and seasonality to two other flux towers (Niwot Ridge, CO and Valles Caldera, NM), located in the Rocky Mountains. These data are useful for constraining ET estimates in similar end‐member locations across the East River Catchment. Our results show that groundwater‐fed ET is a significant component of the water balance and groundwater may supply riparian ET even during low‐snow years. [ABSTRACT FROM AUTHOR]

The majority of alpine plants are of small stature. Through their small size alpine plants are decoupled from the free atmospheric circulation and accumulate solar heat. However, a few alpine species do not follow that "rule" and protrude with their aboveground structures from the microclimatic shelter of the main canopy boundary layer. We aim at explaining the phenomenon of being tall by exploring the biomass production and carbon relations of four pairs of small and tall phylogenetically related taxa in alpine grassland. We compared species and stature-specific biomass allocation, shifts in non-structural carbohydrate (NSC) concentrations in different tissues throughout the season, and we used 13C labels to track carbon transfer from leaves to belowground structures. Small and tall herbs did not differ in their above- to belowground biomass allocation. The NSC composition (starch, fructan, simple sugars) and allocation did not show a stature-specific pattern, except for higher concentrations of simple sugars in tall species during their extended shoot growth. In relative terms, tall species had higher NSC pools in rhizomes, whereas small species had higher NSC pools in roots. Our findings do not place tall alpine forbs in an exceptional category in terms of biomass allocation and carbohydrate storage. The tall versus small stature of the examined herbs does not seem to be associated with specific adjustments in carbon relations. 13C pulse labelling revealed early C autonomy in young, unfolding leaves of the tall species, which are thus independent of the carbon reserves in the massive belowground organs. [ABSTRACT FROM AUTHOR]

Little information about biodiversity patterns in high‐elevation aquatic systems has been gathered, even though these patterns are important for understanding the impacts of human activities. The source region of the Yangtze River, a typical alpine zone with vulnerable and sensitive ecosystems, was selected. Phytoplankton, which play a critical functional role as freshwater primary producers, serve as an important ecological indicator of aquatic systems. Here, systematic surveys on the water environment and phytoplankton were carried out to examine how the phytoplankton community varies with elevation based on hypothesized structural equation models (SEMs) in 10 typical rivers of the Yangtze River source region in March and October 2018. In total, 58 species of phytoplankton belonging to 28 genera were identified. The relationship between species abundance and elevation for phytoplankton showed unimodal elevational patterns. The results of the SEMs showed that all studied aspects affecting the phytoplankton community were directly or indirectly associated with elevation. The synergistic effects of human activities and basic environmental factors (terrestrial productivity and slope gradient) were the drivers affecting the phytoplankton community in the Yangtze River source region. Climate, topography, human activities and other factors are significantly different with changes in elevation, resulting in significant differences in the structure of aquatic communities at different elevations. Human activities were the major drivers affecting the phytoplankton community along the elevational gradient. As the elevation decreased, the disturbances to aquatic ecosystems caused by human activities intensified in the study area. [ABSTRACT FROM AUTHOR]

Populations along steep environmental gradients are subject to differentiating selection that can result in local adaptation, despite countervailing gene flow, and genetic drift. In montane systems, where species are often restricted to narrow ranges of elevation, it is unclear whether the selection is strong enough to influence functional differentiation of subpopulations differing by a few hundred meters in elevation. We used targeted capture of 12 501 exons from across the genome, including 271 genes previously implicated in altitude adaptation, to test for adaptation to local elevations for 2 highland hummingbird species, Coeligena violifer (n = 62) and Colibri coruscans (n = 101). For each species, we described population genetic structure across the complex geography of the Peruvian Andes and, while accounting for this structure, we tested whether elevational allele frequency clines in single nucleotide polymorphisms (SNPs) showed evidence for local adaptation to elevation. Although the 2 species exhibited contrasting population genetic structures, we found signatures of clinal genetic variation with shifts in elevation in both. The genes with SNP-elevation associations included candidate genes previously discovered for high-elevation adaptation as well as others not previously identified, with cellular functions related to hypoxia response, energy metabolism, and immune function, among others. Despite the homogenizing effects of gene flow and genetic drift, natural selection on parts of the genome evidently optimizes elevation-specific cellular function even within elevation range-restricted montane populations. Consequently, our results suggest local adaptation occurring in narrow elevation bands in tropical mountains, such as the Andes, may effectively make them "taller" biogeographic barriers. [ABSTRACT FROM AUTHOR]

Microfungi associated with woody plants on the Qinghai–Tibet Plateau (QTP) were investigated, and four collections associated with Potentilla fruticosa were obtained from Gansu and Qinghai provinces in China. Morphologically, they line well with Lentitheciaceae in having subglobose to globose ascomata with brown setae on the papilla but can be distinguished from other genera by its superficial, globose, black, thick-walled ascomata, and fusiform, hyaline (rarely pale brown), one-septate ascospores, surrounded by an entire mucilaginous sheath. The phylogenetic analyses based on a combined SSU, ITS, LSU and TEF1-α sequence data showed that four isolates formed a monophyletic clade among the genera of Lentitheciaceae, and present as a distinct lineage (sister clade to Darksidea). Therefore, we introduce a new genus Crassoascoma, with C. potentillae as the type to accommodate these taxa. Detailed description and illustration are provided, and the establishment of new taxa is justified with morphology and phylogenetic evidence.

The alpine belt hosts the treeless vegetation above the high elevation climatic treeline. The way alpine plants manage to thrive in a climate that prevents tree growth is through small stature, apt seasonal development, and ‘managing’ the microclimate near the ground surface. Nested in a mosaic of micro-environmental conditions, these plants are in a unique position by a close-by neighborhood of strongly diverging microhabitats. The range of adjacent thermal niches that the alpine environment provides is exceeding the worst climate warming scenarios. The provided mountains are high and large enough, these are conditions that cause alpine plant species diversity to be robust against climatic change. However, the areal extent of certain habitat types will shrink as isotherms move upslope, with the potential areal loss by the advance of the treeline by far outranging the gain in new land by glacier retreat globally.

Background and Purpose: Trees growing at high elevations are particularly sensitive to climate variability. In this study, tree-ring chronologies of Pinus heldreichii Christ. have been developed to examine their dynamism along a 350 km latitudinal gradient. Materials and Methods: Sampling was conducted in 6 high elevation sites along a latitudinal gradient from Kosovo and Albania. Two opposite cores from 148 healthy and dominant P. heldreichii trees were taken using an increment borer. The cores were mounted and sanded, and after a rigorous cross-dating, the ring widths were measured to a resolution of 0.01 mm using the LINTAB 6 measuring device. The ARSTAN program was used for tree-ring series detrending and site chronologies’ development. The relationship between radial growth and climate, as well as between temporal patterns of P. heldreichii growth were investigated using simple correlation analysis and principal component analysis (PCA) over the common period 1951-2013. Results: Radial growth variability of Bosnian pine increased with latitude and elevation. Significant correlations among our chronologies and others from neighbouring countries indicated that our chronologies possess a good regional climatic signal. P. heldreichii growth at all sampling sites was significantly influenced by seasonal and mean annual temperatures, as well as by the July drought. Thus, temperature was the main driving force of species growth, showing a larger control at spatial scale than precipitation. The difference in species growth patterns along the latitudinal gradient is implicated by the common action of climatic and non-climatic factors (age and human activity). With continued warming and precipitation decrease during the second half of the 20th century, P. heldreichii growth from these high elevation sites resulted in being more sensitive to drought. This climatic signal is assumed to be stronger in the future due to climate change. Conclusions: P. heldreichii chronologies developed in our study possess a good local and regional climatic signal. Temperature was the main driving force of P. heldreichii growing in these high elevations sites. The reduction of P. heldreichii growth during the second half of the 20th century due to temperature rise and rainfall decrease imposes the necessity to continue investigations​ on potential impacts of climate warming on species growing near the tree-line.

Emissions from fuel combustion and agricultural activities contribute significantly to the continuous atmospheric entrainment of pollutants into protected and vulnerable ecosystems where long-term monitoring is often a challenge. Here, results are presented from a 26-year study (1989–2015) of wet precipitation collected at Paradise Station (1654 m above sea level), Mount Rainier National Park, Washington, USA. Weekly samples were analyzed for pH, conductivity and major anions and cations. While precipitation concentrations for sulfate, nitrate, protons and conductivity peaked in the early 2000s, overall trends decreased by 54%, 46%, 41%, and 37%, respectively. Associated pH values increased from 5.2 to 5.6, and were largely controlled by non-sea-salt contributions of sulfate and neutralizing calcium, potassium and magnesium. Between 1999 and 2015, nitrogen (N) deposition rates from ammonium increased by a factor of 3.6, from 0.27 to 0.96 kg N ha−1 yr−1 (p = 0.02), while nitrate deposition did not change statistically (0.91–0.74 kg N ha−1 yr−1, p = 0.30). Combined, these N sources are reaching reported critical loads of 2.0 kg N ha−1 yr−1. Results indicate that emission regulations focused on stationary sources have effectively decreased apparent acid precipitation, however, increased nitrogen deposition from ammonium may lead to further fertilization and acidification of delicate soils and waters. Continued long-term monitoring is thus imperative to track continued anthropogenic inputs to vulnerable ecosystems. • Acid precipitation at Mount Rainier National Park decreased since 1989. • Nitrogen deposition from ammonium increased by 260% since 1999. • Ammonium and nitrate contribute equally to nitrogen deposition since 2010. • Nitrogen deposition remains below the critical load. [ABSTRACT FROM AUTHOR]

Other than penguins, only one bird species—the White-winged Diuca Finch (Idiopsar speculifera)—is known to nest directly on ice. Here we provide new details on this unique behavior, as well as the first description of a White-fronted Ground-Tyrant (Muscisaxicola albifrons) nest, from the Quelccaya Ice Cap, in the Cordillera Vilcanota of Peru. Since 2005, >50 old White-winged Diuca Finch nests have been found. The first 2 active nests were found in April 2014; 9 were found in April 2016, 1 of which was filmed for 10 d during the 2016 nestling period. Video of the nest revealed infrequent feedings (>1 h between visits), slow nestling development (estimated 20–30 d), and feeding via regurgitation. The first and only active White-fronted Ground-Tyrant nest was found in October 2014, beneath the glacier in the same area. Three other unoccupied White-fronted Ground-Tyrant nests and an eggshell have been found since, all on glacier ice. At Quelccaya, we also observed multiple species roosting in crevasses or voids (caves) beneath the glacier, at elevations between 5,200 m and 5,500 m, including both White-winged Diuca Finch and White-fronted Ground-Tyrant, as well as Plumbeous Sierra Finch (Phrygilus unicolor), Rufous-bellied Seedsnipe (Attagis gayi), and Gray-breasted Seedsnipe (Thinocorus orbignyianus). These nesting and roosting behaviors are all likely adaptations to the harsh environment, as the glacier provides a microclimate protected from precipitation, wind, daily mean temperatures below freezing, and strong solar irradiance (including UV-B and UV-A). Indeed, the global range of White-winged Diuca Finch coincides relatively closely with the distribution of Andean glaciers, and because no nests are known to have been found away from ice, this species may be a glacier obligate. Given the number of individuals observed and diversity of species associated with, and possibly dependent on, the ice, ongoing loss of tropical glaciers may have a direct, negative effect on High Andean biodiversity. [ABSTRACT FROM AUTHOR]

Elevation‐dependent warming in high‐elevation regions is of great interest to many researchers, but global assessment of seasonal signals of elevation‐dependent warming has received little attention. Here, using monthly mean temperatures from 2,104 global stations for the period 1961–2010, we find that the temperature trends are highly significant in all seasons for the high‐elevation stations (>500 m a.s.l.) as well as their low‐elevation counterparts over the study period. For the high‐elevation stations, the warming is the strongest in winter, followed by autumn, spring and summer, with the magnitudes of 2.165, 1.355, 1.344 and 1.256 °C/50 year, respectively. With the exception of spring, the trend in three other seasons is clearly higher for the high‐elevation stations than their low‐elevation counterparts. A significant altitudinal amplification trend is detected for all seasons for the high‐elevation stations based on the elevation band method, and the amplification amplitude for autumn and winter is about two times that for spring and summer. Furthermore, stepwise regression analysis reveals that the trends of each season for the high‐elevation stations are closely related to altitude and latitude, suggesting that there exist not only an altitudinal amplification trend but also a latitudinal amplification trend on the seasonal scale for the high‐elevation stations in the past 50 years. It was also found that the warming in each season for the high‐elevation stations is linearly related to the temperature lapse rates in altitudinal and latitudinal directions due in large part to the mathematical shape of Stefan–Boltzmann law in these two directions. [ABSTRACT FROM AUTHOR]

The study provides descriptive information of the floristic composition, forest structure and effects of disturbance on forest structure of a mid-elevation (≥ 1800 ≤ 2100 m amsl) tropical montane evergreen forests (sholas) in the Nilgiri Mountains, southern India. Sampling plots of 10 × 100 m (1000 m2, 0.1 ha) were surveyed in ten different locations within a large patch, giving a total sample area of approximately 1 ha. All individual stems (≥ 1 cm dbh) of trees, shrubs and lianas from these plots were identified to species level and counted. A total of 3896 individuals (≥ 10 cm dbh) comprising 97 species, 79 genera and 45 families were included. On average there were a total of 1246 individual stems of at least 10 cm per hectare with a basal area 53.33 m2 ha-1. The species abundance distribution did not differ significantly from a log-normal distribution. According to the Importance value index (IVI), five species, namely Litsea glabrata, Lasianthus venulosus, Meliosma simplicifolia, Daphniphyllum neilgherrense and Neolitsea fischeri were dominant species in the community and influenced forest structure more than any other species present. Lauraceae, Rubiaceae, Euphorbiaceae, Myrtaceae and Symplocaceae were most dominant families according to the Family Importance Value index (FIV). Our results also suggest that disturbance influences tree species richness and density and liana density and basal area, in addition toforest structure and changes species composition. Moreover, the study shows that one-hectare floristic inventories of shola forests can provide a useful tool for assessing plant biodiversity, and provide useful information for effective conservation and management of nature reserves. [ABSTRACT FROM AUTHOR]

The environment of high-altitudinal cold deserts of Western Himalaya is characterized by extensive development of biological soil crusts, with cyanobacteria as dominant component. The knowledge of their taxonomic composition and dependency on soil chemistry and elevation is still fragmentary. We studied the abundance and the phylogenetic diversity of the culturable cyanobacteria and eukaryotic microalgae in soil crusts along altitudinal gradients (4600-5900 m) at two sites in the dry mountains of Ladakh (SW Tibetan Plateau and Eastern Karakoram), using both microscopic and molecular approaches. The effects of environmental factors (altitude, mountain range, and soil physico-chemical parameters) on the composition and biovolume of phototrophs were tested by multivariate redundancy analysis and variance partitioning. Both phylogenetic diversity and composition of morphotypes were similar between Karakorum and Tibetan Plateau. Phylogenetic analysis of 16S rRNA gene revealed strains belonging to at least five genera. Besides clusters of common soil genera, e.g., Microcoleus, Nodosilinea, or Nostoc, two distinct clades of simple trichal taxa were newly discovered. The most abundant cyanobacterial orders were Oscillatoriales and Nostacales, whose biovolume increased with increasing elevation, while that of Chroococales decreased. Cyanobacterial species richness was low in that only 15 morphotypes were detected. The environmental factors accounted for 52 % of the total variability in microbial data, 38.7 % of which was explained solely by soil chemical properties, 14.5 % by altitude, and 8.4 % by mountain range. The elevation, soil phosphate, and magnesium were the most important predictors of soil phototrophic communities in both mountain ranges despite their different bedrocks and origin. The present investigation represents a first record on phylogenetic diversity of the cyanobacterial community of biological soil crusts from Western Himalayas and first record from altitudes over 5000 m. [ABSTRACT FROM AUTHOR]

Breeding of native cool-season grasses has the potential to improve forage production and expand the range of bioenergy feedstocks throughout western North America. Basin wildrye (Leymus cinereus) and creeping wildrye (Leymus triticoides) rank among the tallest and most rhizomatous grasses of this region, respectively. The objectives of this study were to develop interspecific creeping wildrye (CWR) × basin wildrye (BWR) hybrids and evaluate their biomass yield relative to tetraploid ‘Trailhead’, octoploid ‘Magnar’ and interploidy-hybrid ‘Continental’ BWR cultivars in comparison with other perennial grasses across diverse single-harvest dryland range sites and a two-harvest irrigated production system. Two half-sib hybrid populations were produced by harvesting seed from the tetraploid self-incompatible Acc:641.T CWR genet, which was clonally propagated by rhizomes into isolated hybridization blocks with two tetraploid BWR pollen parents: Acc:636 and ‘Trailhead’. Full-sib hybrid seed was also produced from a controlled cross of tetraploid ‘Rio’ CWR and ‘Trailhead’ BWR plants. In space-planted range plots, the ‘Rio’ CWR × ‘Trailhead’ BWR and Acc:641.T CWR × Acc:636 BWR hybrids displayed high-parent heterosis with 75% and 36% yield advantages, respectively, but the Acc:641.T CWR × ‘Trailhead’ BWR hybrid yielded significantly less than its BWR high-parent in this evaluation. Half-sib CWR × BWR hybrids of Acc:636 and ‘Trailhead’ both yielded as good as or better than available BWR cultivars, with yields similar to switchgrass (Panicum virgatum), in the irrigated sward plots. These results elucidate opportunity to harness genetic variation among native grass species for the development of forage and bioenergy feedstocks in western North America.

Sediments containing terrestrial and aquatic mollusks and ostracodes from the Ziegler Reservoir fossil site (2705 m elevation) near Snowmass Village, Colorado, span ~ 130–87 ka (MIS 5e through 5b). The southeastern area of the site where taxa were recovered was a relatively fresh, shallow, well-vegetated wetland during MIS 5e through 5c time, approximately 2 m deep, with a total dissolved solids value of ~ 200–1000 mg L − 1 . The wetland was seasonally or annually variable and groundwater discharged along the margins of the bounding moraine. Groundwater likely contributed solutes to the system and may have contributed 18 O-enriched water. Based on stable isotopes from ostracode calcite (δ 18 O OST and δ 13 C OST ), seasonal evaporation occurred and the dissolved inorganic carbon pool was unexpectedly enriched in 13 C. The mollusk and ostracode faunas changed little across the MIS 5e/5d/5c boundaries, whereas a distinct change in the ostracode fauna occurred between the deposition of Unit 11 and Unit 13, which corresponds in time to the MIS 5c/5b boundary, indicating some combination of increased surface and/or groundwater flow, a decrease in water temperature, and a freshening and a possible deepening of the wetland. [ABSTRACT FROM AUTHOR]

To examine the influence of landscape characteristics and landscape position on aquatic biogeochemistry, we sampled a total of 76 lakes within 14 different lake-chains spanning the latitudinal extent of the high-elevation Sierra Nevada (California). We measured water chemistry, dissolved organic matter (DOM), nutrients, and biotic variables in study catchments that encompassed representative ranges of area (3-22 km), elevation (2,200-3,700 m.a.s.l), elevation change (50-700 m), and average slope (13°-26°). Hierarchical models were used to account for variability in biogeochemistry because they explicitly maintain the framework of lakes within individual lake-chains while accounting for variation among lake-chains. Unconditional means models, where lake-chain was a random effect, revealed significant differences among lake-chains for nearly all biogeochemical variables. Models explained 42-95% of this variability, with the majority of the variation (70%) explained by the among lake-chain component. To explore the amount of additional variation explained by lake landscape position, we added lake network number (LNN) to models. LNN explained a significant amount of additional variation (7% average) in 8 of 23 biogeochemical parameters. However, it explained more variability within individual lake-chains (75%), where among lake-chain differences did not obscure patterns. Patterns of increase with LNN were found for dissolved organic carbon and nitrogen, fluorescence of DOM, alkalinity, and bacterioplankton abundance, whereas nitrate and nitrogen to phosphorus nutrient ratios decreased. LNN explained variation because it served as a proxy for underlying catchment characteristics that changed consistently along downstream flow paths. To characterize the amount of variation explained by catchment characteristics alone, we fit a third model that included lake-chain as a random effect and landscape or lake morphometry attributes as fixed effects. Catchment characteristics explained about as much additional variation (6%) as LNN, but for substantially more biogeochemical parameters (18 out of 23). The catchment characteristics most predictive of biogeochemistry were land-cover factors delineating alpine and subalpine zones (elevation, slope, or proportions of rock or shrub cover). In general, catchment characteristics were stronger predictors of biogeochemistry than characteristics of lake morphometry, emphasizing the relative importance of landscape processes in snowmelt-dominated lake ecosystems. [ABSTRACT FROM AUTHOR]

We characterized spatial and temporal variability in net ecosystem production (NEP), community respiration (CR), and gross primary production (GPP) over an ice-free season in an oligotrophic high-elevation lake using high-frequency measurements of dissolved oxygen. We combined the use of free-water and incubation chamber measurements to compare pelagic and benthic habitats and estimate their relative contributions to whole-lake metabolism. Despite a brief period of predominant heterotrophy after snowmelt, both free-water and incubation chamber measurements confirmed autotrophy of the epilimnion in all habitats throughout the ice-free season. In contrast, benthic incubation chambers showed the benthos to be consistently heterotrophic. Although temperature was the strongest seasonal driver of benthic metabolism, bacterioplankton density and indexes of organic matter quality explained the most variability in pelagic metabolism. Driven largely by benthic metabolism, free-water measurements of GPP and CR were twice as high in littoral than pelagic habitats. However, rates of water column primary production overlying the littoral benthos were high enough to overcome net benthic heterotrophy, and seasonal mean NEP in littoral habitats remained positive and not significantly different from pelagic habitats. Benthic rates averaged about 25% of whole-lake metabolism. Pelagic metabolism measurements were affected by littoral rates about half the time, with the degree of isolation between the two a function of advection and water column stability. These results emphasize the importance of characterizing spatial and temporal variability in metabolism within the context of physical dynamics and challenge the notion that benthic metabolism will necessarily be larger than pelagic metabolism in oligotrophic lakes. [ABSTRACT FROM AUTHOR]

Although high elevation meadows are often considered to be primarily temperature-limited, aboveground net primary production (ANPP) is influenced by both growing season length (GSL) and soil moisture (SM). Progress in understanding these responses comes from studies at individual sites that are often focused on single abiotic drivers, so little is known about how climatic constraints relate to one another and limit ANPP at larger scales. We examined the independent and combined effects of these two key climate drivers (GSL and SM) across a suite of high elevation meadows from two continents. We also sampled gradients of each variable at a single site to explore mechanisms for SM and GSL limitations. Here, we show that high elevation meadows are limited by both GSL and SM levels. GSL constrained maximum ANPP by approximately 4 g m d whereas average daily ANPP beneath this constraint was significantly influenced by SM. Carbon isotope and plant/soil nitrogen data suggest that SM influenced ANPP through its impact on nitrogen availability. Increases in GSL can increase ANPP unless those increases are accompanied by SM decreases. These interactive effects can produce distinct ecological patterns and must be considered when predicting high elevation meadow responses to future climate changes. [ABSTRACT FROM AUTHOR]

Abstract: The level and mechanism of resistance to damage from freezing temperatures is related to the ambient temperatures experienced by plants. High-elevation habitats exhibit a thermal gradient in the air–soil profile, exposing ground-level species to more rigorous thermal microhabitats than well aboveground species. Such gradients could explain an inverse relationship between freezing temperature damage (LT50) and plant height, such that leaves of smaller plants tolerate freezing conditions, while leaves of taller plants avoid them. However, microclimatic data have not been included in previous studies evaluating those patterns. On the other hand, a proposed trade-off between plant functional traits and freezing resistance suggest that leaves of growth-forms with higher intensity of growth are less freezing resistant than those with lower growth intensity. In this work, we determined whether the ability to resist freezing temperatures is related to plant height or growth-form in 37 high-elevation species from the Central Chilean Andes. We proposed that (1) plants with contrasting heights are exposed to different thermal conditions during freezing events, (2) the level and the mechanism of freezing resistance are inversely related to plant height, and that (3) the level of freezing resistance varied between plants with low- and high-growth intensities. We found that high-Andean species of different heights are exposed to different thermal conditions depending on the distance from the ground. However, neither level nor mechanisms of freezing resistance were related to plant height. Leaves of both short and tall plants showed similar LT50 and their main freezing resistance mechanism was tolerance. Moreover, leaves of growth-forms with high- and low-growth intensity resisted similar freezing temperatures. Our results are discussed in relation to environmental conditions that characterize the Central Chilean Andes. [Copyright &y& Elsevier]

Microfungi associated with woody plants on the Qinghai–Tibet Plateau (QTP) were investigated, and four collections associated with Potentilla fruticosa were obtained from Gansu and Qinghai provinces in China. Morphologically, they line well with Lentitheciaceae in having subglobose to globose ascomata with brown setae on the papilla but can be distinguished from other genera by its superficial, globose, black, thick-walled ascomata, and fusiform, hyaline (rarely pale brown), one-septate ascospores, surrounded by an entire mucilaginous sheath. The phylogenetic analyses based on a combined SSU, ITS, LSU and TEF1-α sequence data showed that four isolates formed a monophyletic clade among the genera of Lentitheciaceae, and present as a distinct lineage (sister clade to Darksidea). Therefore, we introduce a new genus Crassoascoma, with C. potentillae as the type to accommodate these taxa. Detailed description and illustration are provided, and the establishment of new taxa is justified with morphology and phylogenetic evidence. [ABSTRACT FROM AUTHOR]

Abstract: Modeling how the role of forests in the carbon cycle will respond to predicted changes in water availability hinges on an understanding of the processes controlling water use in ecosystems. Recent studies in forest ecosystem modeling have employed data-assimilation techniques to generate parameter sets that conform to observations, and predict net ecosystem CO2 exchange (NEE) and its component processes. Since the carbon and water cycles are linked, there should be additional process information available from ecosystem H2O exchange. We coupled SIPNET (Simple Photosynthesis EvapoTranspiration), a simplified model of ecosystem function, with a data-assimilation system to estimate parameters leading to model predictions most closely matching the net CO2 and H2O fluxes measured by eddy covariance in a high-elevation, subalpine forest ecosystem. When optimized using measurements of CO2 exchange, the model matched observed NEE (RMSE=0.49gCm−2) but underestimated transpiration calculated independently from sap flow measurements by a factor of 4. Consequently, the carbon-only optimization was insensitive to imposed changes in water availability. Including eddy flux data from both CO2 and H2O exchange to the optimization reduced the model fit to the observed NEE fluxes only slightly (RME=0.53gCm−2), however this parameterization also reproduced transpiration calculated from independent sap flow measurements (r 2 =0.67, slope=0.6). A significant amount of information can be extracted from simultaneous analysis of CO2 and H2O exchange, which improved the accuracy of transpiration estimates from measured evapotranspiration. Conversely, failure to include both CO2 and H2O data streams can generate results that mask the responses of ecosystem carbon cycling to variation in the precipitation. In applying the model conditioned on both CO2 and H2O fluxes to the subalpine forest at the Niwot Ridge AmeriFlux site, we observed that the onset of transpiration is coincident with warm soil temperatures. However, after snow has covered the ground in the fall, we observed significant inter-annual variability in the fraction of evapotranspiration composed of transpiration; evapotranspiration was dominated by transpiration in years when late fall air temperatures were high enough to maintain photosynthesis, but by sublimation from the surface of the snowpack in years when late fall air temperatures were colder and forest photosynthetic activity had ceased. Data-assimilation techniques and simultaneous measurements of carbon and water exchange can be used to quantify the response of net carbon uptake to changes in water availability by using an ecosystem model where the carbon and water cycles are linked. [Copyright &y& Elsevier]

Mechanisms underlying catchment export of nitrogen (N) during seasonal transitions (i.e., winter to spring and summer to autumn) were investigated in high-elevation catchments of the Sierra Nevada using stable isotopes of nitrate and water, intensive monitoring of stream chemistry and detailed catchment N-budgets. We had four objectives: (1) determine the relative contribution of snowpack and soil nitrate to the spring nitrate pulse, (2) look for evidence of biotic control of N losses at the catchment scale, (3) examine dissolved organic nitrogen ( DON) export patterns to gain a better understanding of the biological and hydrological controls on DON loss, and (4) examine the relationship between soil physico-chemical conditions and N export. At the Emerald Lake watershed, nitrogen budgets and isotopic analyses of the spring nitrate pulse indicate that 50 to 70% of the total nitrate exported during snowmelt (ca. April to July) is derived from catchment soils and talus; the remainder is snowpack nitrate. The spring nitrate pulse occurred several weeks after the start of snowmelt and was different from export patterns of less biologically labile compounds such as silica and DON suggesting that: (1) nitrate is produced and released from soils only after intense flushing has occurred and (2) a microbial N-sink is operating in catchment soils during the early stages of snowmelt. DON concentrations varied less than 20–30% during snowmelt, indicating that soil processes tightly controlled DON losses. [ABSTRACT FROM AUTHOR]

A chemical survey of 69 high-altitude lakes in seven national parks in the western United States was conducted during the fall of 1999; the lakes were previously sampled during the fall of 1985, as part of the Western Lake Survey. Lakes in parks in the Sierra/southern Cascades (Lassen Volcanic, Yosemite, Sequoia/Kings Canyon National Parks) and in the southern Rocky Mountains (Rocky Mountain National Park) were very dilute; median specific conductance ranged from 4.4 to 12.2 μS cm-1 and median alkalinity concentrations ranged from 32.2 to 72.9 μeq L-1. Specific conductances and alkalinity concentrations were substantially higher in lakes in the central and northern Rocky Mountains parks (Grand Teton, Yellowstone, and Glacier National Parks), probably due to the prevalence of more reactive bedrock types. Regional patterns in lake concentrations of NO3 and SO4 were similar to regional patterns in NO3 and SO4 concentrations in precipitation, suggesting that the lakes are showing a response to atmospheric deposition. Concentrations of NO3 were particularly high in Rocky Mountain National Park, where some ecosystems appear to be undergoing nitrogen saturation. [ABSTRACT FROM AUTHOR]

The alpine belt hosts the treeless vegetation above the high elevation climatic treeline. The way alpine plants manage to thrive in a climate that prevents tree growth is through small stature, apt seasonal development, and 'managing' the microclimate near the ground surface. Nested in a mosaic of micro-environmental conditions, these plants are in a unique position by a close-by neighborhood of strongly diverging microhabitats. The range of adjacent thermal niches that the alpine environment provides is exceeding the worst climate warming scenarios. The provided mountains are high and large enough, these are conditions that cause alpine plant species diversity to be robust against climatic change. However, the areal extent of certain habitat types will shrink as isotherms move upslope, with the potential areal loss by the advance of the treeline by far outranging the gain in new land by glacier retreat globally. [ABSTRACT FROM AUTHOR]