Alpine Elevation Research Articles

Solar radiation explains litter degradation along alpine elevation gradients better than other climatic or edaphic parameters.

Organic matter (OM) decomposition has been shown to vary across ecosystems, suggesting that variation in local ecological conditions influences this process. A better understanding of the ecological factors driving OM decomposition rates will allow to better predict the effect of ecosystem changes on the carbon cycle. While temperature and humidity have been put forward as the main drivers of OM decomposition, the concomitant role of other ecosystem properties, such as soil physicochemical properties, and local microbial communities, remains to be investigated within large-scale ecological gradients. To address this gap, we measured the decomposition of a standardized OM source - green tea and rooibos tea - across 24 sites spread within a full factorial design including elevation and exposition, and across two distinct bioclimatic regions in the Swiss Alps. By analyzing OM decomposition via 19 climatic, edaphic or soil microbial activity-related variables, which strongly varied across sites, we identified solar radiation as the primary source of variation of both green and rooibos teabags decomposition rate. This study thus highlights that while most variables, such as temperature or humidity, as well as soil microbial activity, do impact decomposition process, in combination with the measured pedo-climatic niche, solar radiation, very likely by means of indirect effects, best captures variation in OM degradation. For instance, high solar radiation might favor photodegradation, in turn speeding up the decomposition activity of the local microbial communities. Future work should thus disentangle the synergistic effects of the unique local microbial community and solar radiation on OM decomposition across different habitats.

Positive community effects of nurse-plant shrubs along a tropical alpine elevation gradient: are they linked with plant water relations?

Positive community effects of nurse-plant shrubs along a tropical alpine elevation gradient: are they linked with plant water relations?

Middle Miocene Climate and Stable Oxygen Isotopes in Europe Based on Numerical Modeling

AbstractThe Middle Miocene (15.99–11.65 Ma) of Europe witnessed major climatic, environmental, and vegetational change, yet we are lacking detailed reconstructions of Middle Miocene temperature and precipitation patterns over Europe. Here, we use a high‐resolution (∼0.75°) isotope‐enabled general circulation model (ECHAM5‐wiso) with time‐specific boundary conditions to investigate changes in temperature, precipitation, and δ18O in precipitation (δ18Op). Experiments were designed with variable elevation configurations of the European Alps and different atmospheric CO2 levels to examine the influence of Alpine elevation and global climate forcing on regional climate and δ18Op patterns. Modeling results are in agreement with available paleobotanical temperature data and with low‐resolution Middle Miocene experiments of the Miocene Model Intercomparison Project (MioMIP1). However, simulated precipitation rates are 300–500 mm/yr lower in the Middle Miocene than for pre‐industrial times for central Europe. This result is consistent with precipitation estimates from herpetological fossil assemblages, but contradicts precipitation estimates from paleobotanical data. We attribute the Middle Miocene precipitation change in Europe to shifts in large‐scale pressure patterns in the North Atlantic and over Europe and associated changes in wind direction and humidity. We suggest that global climate forcing contributed to a maximum δ18Op change of ∼2‰ over high elevation (Alps) and ∼1‰ over low elevation regions. In contrast, we observe a maximum modeled δ18Op decrease of 8‰ across the Alpine orogen due to Alpine topography. However, the elevation‐δ18Op lapse rate shallows in the Middle Miocene, leading to a possible underestimation of paleotopography when using present‐day δ18Op—elevation relationships data for stable isotope paleoaltimetry studies.

Flexible steel structures used for ski tunnels in Parang Mountains, Romania

Abstract The main idea of this project was to create an access road for the tourists and also to improve the winter sports conditions, especially the ski, in the beautiful Parag Mountains. It was a very challenging project, as the road takes until 1600 m at alpine elevation. One of the structures was delivered and assembled in November 2019, in 3 weeks of hard weather conditions, with a 5 working men team.

Effects of nurse shrubs on symbioses between soil fungi and associated plants along a tropical alpine elevation gradient

Effects of nurse shrubs on symbioses between soil fungi and associated plants along a tropical alpine elevation gradient

Decreasing molecular diversity of soil dissolved organic matter related to microbial community along an alpine elevation gradient

Characterization of soil dissolved organic matter (DOM) and understanding of the interactions between soil microbial communities and DOM molecules along elevation gradients in alpine ecosystems are still limited. To unravel these interactions and how they change along alpine elevation gradients, we sampled topsoil in the Sygera Mountains (Tibet, China) at elevations between 3800 and 4600 m. The molecular characteristics of soil DOM were determined using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) and soil microbial composition was identified by high-throughput sequencing. Among the seven components of DOM, the lignins/CRAM (carboxyl-rich alicyclic molecules)-like structure dominated at all elevations, followed by tannins, while the relative abundance of unstable substances, including lipids, aliphatic/protein, and carbohydrates, was lower. As elevation increased, the molecular diversity, degree of oxidation, aromaticity, and unsaturation of soil DOM decreased. The abundance and diversity of soil bacteria and fungi also generally decreased with elevation. Both bacteria and fungi play an important role in the degradation of DOM molecules, but bacteria appear to have greater degradation ability. Among them, Proteobacteria and Bacteroidetes mainly promote the degradation of lignins/CRAM-like structure molecules, while Basidiomycota mainly degrade more unstable substrates. Co-occurrence network analysis revealed complex correlations between specific microbial groups and DOM molecules. Our results suggest that more active cycling of soil DOM could occur in alpine ecosystems due to climate warming, as the result of increased vegetation productivity and litter input in response to rising temperature promoting the relative abundance of microbial groups capable of degrading lignins/CRAM-like structures in soil DOM.

Soil respiration variation along an altitudinal gradient in the Italian Alps: Disentangling forest structure and temperature effects

On the mountains, along an elevation gradient, we generally observe an ample variation in temperature, with the associated difference in vegetation structure and composition and soil properties. With the aim of quantifying the relative importance of temperature, vegetation and edaphic properties on soil respiration (SR), we investigated changes in SR along an elevation gradient (404 to 2101 m a.s.l) in the southern slopes of the Alps in Northern Italy. We also analysed soil physicochemical properties, including soil organic carbon (SOC) and nitrogen (N) stocks, fine root C and N, litter C and N, soil bulk densities and soil pH at five forest sites, and also stand structural properties, including vegetation height, age and basal area. Our results indicated that SR rates increased with temperature in all sites, and 55–76% of SR variability was explained by temperature. Annual cumulative SR, ranging between 0.65–1.40 kg C m-2 yr-1, decreased along the elevation gradient, while temperature sensitivity (Q10) of SR increased with elevation. However, a high SR rate (1.27 kg C m-2 yr-1) and low Q10 were recorded in the mature conifer forest stand at 1731 m a.s.l., characterized by an uneven-aged structure and high dominant tree height, resulting in a nonlinear relationship between elevation and temperature. Reference SR at 10°C (SRref) was unrelated to elevation, but was related to tree height. A significant negative linear relationship was found between bulk density and elevation. Conversely, SOC, root C and N stock, pH, and litter mass were best fitted by nonlinear relationships with elevation. However, these parameters were not significantly correlated with SR when the effect of temperature was removed (SRref). These results demonstrate that the main factor affecting SR in forest ecosystems along this Alpine elevation gradient is temperature, but its regulating role can be strongly influenced by site biological characteristics, particularly vegetation type and structure, affecting litter quality and microclimate. This study also confirms that high elevation sites are rich in SOC and more sensitive to climate change, being prone to high C losses as CO2. Furthermore, our data indicate a positive relationship between Q10 and dominant tree height, suggesting that mature forest ecosystems characterized by an uneven-age structure, high SRref and moderate Q10, may be more resilient.

Temperature sensitivity of CO2 efflux in soils from two alpine elevation levels with distinct bedrock types

Predicted increase in climate warming will affect soil organic carbon (SOC) dynamics in vulnerable cold alpine environments. In contrast to freeze and thaw cycles, less is known about the effects of temperature regimes in the range between 2 and 10 °C on SOC availability to soil microorganisms. For this reason, CO2 efflux, extracellular enzyme activities and microbial communities were measured in an incubation experiment with three temperature treatments: (T1) continuous 10 °C, (T2) cooled down to 2 °C, and (T3) rewarmed from 2 to 10 °C. Two forest soils at low elevation and two grassland soils at high elevation were taken from two sites with distinct bedrock types (limestone at Hochschwab, gneiss and schist at Rauris). The CO2 efflux did not differ significantly between the elevation levels at the two sites. In the continuous warm treatment T1, the relative decline in CO2 efflux was stronger in the two Rauris than in the two Hochschwab soils during the 0–123 days period. In the cooling treatment T2, the cumulative ΣCO2C efflux of the Hochschwab soils was lowered by 32% and that of the Rauris soils by only 19% compared with T1 during the 30–123 days period. In the rewarming treatment T3, the ΣCO2 efflux was on average 33% higher than that of treatment T1 during the 91–123 days period, ranging from +8% to +62%. Phospholipid fatty acid (PLFA) composition and extracellular enzyme activities were not markedly affected by incubation time or temperature treatments. The differences in bedrock properties had stronger effects on the ΣCO2 efflux, enzyme activities as well as total PLFA content and composition than elevation level or vegetation. Other, largely unknown factors control the rewarming effects on the mobilisation of a labile SOC pool.

Spatial and evolutionary predictability of phytochemical diversity

To cope with environmental challenges, plants produce a wide diversity of phytochemicals, which are also the source of numerous medicines. Despite decades of research in chemical ecology, we still lack an understanding of the organization of plant chemical diversity across species and ecosystems. To address this challenge, we hypothesized that molecular diversity is not only related to species diversity, but also constrained by trophic, climatic, and topographical factors. We screened the metabolome of 416 vascular plant species encompassing the entire alpine elevation range and four alpine bioclimatic regions in order to characterize their phytochemical diversity. We show that by coupling phylogenetic information, topographic, edaphic, and climatic variables, we predict phytochemical diversity, and its inherent composition, of plant communities throughout landscape. Spatial mapping of phytochemical diversity further revealed that plant assemblages found in low to midelevation habitats, with more alkaline soils, possessed greater phytochemical diversity, whereas alpine habitats possessed higher phytochemical endemism. Altogether, we present a general tool that can be used for predicting hotspots of phytochemical diversity in the landscape, independently of plant species taxonomic identity. Such an approach offers promising perspectives in both drug discovery programs and conservation efforts worldwide.

Microbial necromass formation, enzyme activities and community structure in two alpine elevation gradients with different bedrock types

Microbial necromass is an important part of soil organic carbon (SOC), but the changes in its contribution along elevational gradients and soil types are poorly understood. At two sites, the alkaline site Hochschwab and the acidic site Rauris, soil samples from three elevation levels and depths were analysed for amino sugars as microbial necromass indices, extracellular enzymes, and phospholipid fatty acids (PLFA) as microbial biomass indices. The three elevation levels at each site represented similar temperature and precipitation regimes. Microbial necromass contribution to SOC was lower (26%) at the alkaline site than at the acidic site (37%), indicating lower transformation of microbial biomass into stable SOC and support the increased accumulation of fungal necromass under N limitation at Hochschwab. Fungi generally dominate microbial necromass, with 88% at Hochschwab and 77% at Rauris. At the alkaline site Hochschwab, phenoloxidase, peroxidase and phosphatase enzymes activities were lower by 96%, 98% and 75%, respectively than at the acidic Rauris site, but not those of the hydrolytic enzymes β-glucosidase, exo-glucanase, exo-chitinase, and protease, indicating retarded decomposition of plant residues. Gram positive bacteria dominate bacterial biomass at both sites, with 70% at Hochschwab and 72% at Rauris. The higher fungal to bacterial PLFA ratio suggest increased contribution of fungi to total microbial PLFA at Hochschwab due to the better adaptability of fungi to the site-specific environmental conditions. Effects along alpine elevation gradients depend on vegetation induced changes in soil properties, which interact with bedrock properties.

Shallow erosion on grassland slopes in the European Alps – Geomorphological classification, spatio-temporal analysis, and understanding snow and vegetation impacts

Erosion with the subsequent loss of soil and soil fertility is one of the urgent environmental problems worldwide. On grassland slopes from the montane to the alpine elevation zones of the European Alps, shallow erosion is a widespread and regionally increasing phenomenon. This group of mechanical denudation processes includes shallow landslides and nival abrasion (i.e., by snow gliding and avalanches), which are displacing patches of vegetation, soil and unconsolidated material. The resulting bare ground areas as well as the dislocated material are susceptible to further transport by water, snow, or wind. Our review summarizes the current knowledge on the main geomorphological processes for Alpine grassland erosion, namely shallow landslides and abrasion by snow movements as well as combinations of both processes. We shortly discuss the basic and variable controlling factors and further present a comprehensive approach for identifying and classifying shallow erosion phenomena and processes. In this context, the possibilities, limitations, and challenges for identification, classification and analysis of these processes by remote sensing are discussed in detail. Furthermore, the article focuses particularly on the role of snow-related processes, the relationship of erosion and vegetation, and the re-stabilization of affected areas by plants. Finally, we outline the discussion on the impact of land-use and climate change on these shallow erosion processes and identify the main research gaps that should be bridged in order to both better understand and deal with these erosion types on Alpine slopes.

Seasonal changes in arthropod diversity patterns along an Alpine elevation gradient

Deciphering patterns in species distributions and species interactions along ecological gradients are fundamental topics in ecology. Theory holds that species diversity is greater and interactions are stronger under warmer and more stable environments, such as low elevations and latitudes. However, recent findings have shown conflicting evidence, potentially due to seasonal effects. We aimed to address this gap by studying seasonal changes in arthropod communities over an elevation gradient in the Swiss Alps, as well as herbivore‐predator interactions and their resulting consequences on plant herbivory levels. Overall, we found hump‐shaped patterns in arthropod abundance, richness and diversity with increasing elevation, with all factors peaking below the tree line. However, these patterns varied seasonally, with strong mid‐elevation peaks at the beginning of the summer, shifting to a pattern of linear decrease at the beginning of the fall. In searching for mechanisms explaining these changes, we found that shifts in arthropod communities over elevation and seasons usually followed shifts in vegetation productivity estimates. Other factors, such as top‐down control by natural enemies, which was generally stronger at low elevations, and plant species‐specific resistance rates along elevation gradients were also implicated as drivers of diversity and herbivory rates. These results highlight the complexity of arthropod communities' responses to environmental gradients, which vary during the season in response to relative changes in both bottom‐up and top‐down forces.

Interactions between nurse-plants and an exotic invader along a tropical alpine elevation gradient: growth-form matters

Conceptual models of how interactions with native species influence invasions emphasize competition, but recent evidence suggests facilitation can promote invasion in stressful environments. However, how nurse-plants with contrasting growth-forms and distribution interact with invaders remains unexplored, although it could offer insights on nurse/exotic interaction mechanisms. We asked whether shrub and cushion nurses differed in their effects on the exotic Rumex acetosella in sites at four elevations in the high tropical Andes (4100–4400 m), shrubs dominating the lowest sites and cushions the highest sites. During the dry season, we measured soil organic matter (SOM) and water content (SWC) under the shrub Hypericum laricifolium, the cushion Azorella julianii, and adjacent areas outside. We compared Rumex’s performance under each situation, measuring midday leaf temperatures (Tleaf), vapor pressure deficit (VPD), minimum water potentials (Ψmin) and leaf nitrogen (Nleaf) and compared the number, size and proportion of fruiting ramets within sampling rings in each situation. SOM and SWC were higher at all elevations under cushions, then under shrubs and lower outside. Rumex’s density was generally reduced under shrubs but increased on cushions. However, both nurses had positive effects along the gradient on Rumex’s size, reproduction, water balance and Nleaf, shrubs having stronger effects on Tleaf and VPD and cushions on Nleaf. Our results indicate that alternating nurses influenced an invader’s physiological performance to different extents via contrasting effects on shading and soil resources, leading to mixed competitive/facilitative effects of shrubs on the exotic’s demography, while cushions had more consistent facilitative effects across elevations.

Shrub range expansion alters diversity and distribution of soil fungal communities across an alpine elevation gradient.

Global climate and land use change are altering plant and soil microbial communities worldwide, particularly in arctic and alpine biomes where warming is accelerated. The widespread expansion of woody shrubs into historically herbaceous alpine plant zones is likely to interact with climate to affect soil microbial community structure and function; however, our understanding of alpine soil ecology remains limited. This study aimed to (i) determine whether the diversity and community composition of soil fungi vary across elevation gradients and to (ii) assess the impact of woody shrub expansion on these patterns. In the White Mountains of California, sagebrush (Artemisia rothrockii) shrubs have been expanding upwards into alpine areas since 1960. In this study, we combined observational field data with a manipulative shrub removal experiment along an elevation transect of alpine shrub expansion. We utilized next-generation sequencing of the ITS1 region for fungi and joint distribution modelling to tease apart effects of the environment and intracommunity interactions on soil fungi. We found that soil fungal diversity declines and community composition changes with increasing elevation. Both abiotic factors (primarily soil moisture and soil organic C) and woody sagebrush range expansion had significant effects on these patterns. However, fungal diversity and relative abundance had high spatial variation, overwhelming the predictive power of vegetation type, elevation and abiotic soil conditions at the landscape scale. Finally, we observed positive and negative associations among fungal taxa which may be important in structuring community responses to global change.

Scale sensitivity of the relationship between alpha and gamma diversity along an alpine elevation gradient in central Nepal

AbstractAimComponents of scale, such as grain, focus and extent, influence the spatial patterns of alpha and gamma diversity and the relationships between them. We explored these scale relations by testing whether the gamma diversity and alpha diversity along an elevation gradient were related independent of scale and whether the elevational patterns of herbaceous and woody species richness were dependent on scale.LocationLangtang National Park, Nepal.MethodsWe estimated alpha diversity (plot richness) for woody and herbaceous plant species along an alpine elevation gradient (3,900–5,000 m a.s.l.) in nested plots of 1 m2, 16 m2 and 100 m2 and gamma diversity (regional richness) from published sources. Generalized linear modelling was used to analyse alpha and gamma diversity and their correspondence at different grain sizes.ResultsElevational trends of gamma and alpha diversity were significantly correlated for both woody and herbaceous species at all grain sizes. The concordance increased with increasing grain size and area for gamma diversity estimation, particularly for the monotonously decreasing elevational gamma and alpha diversity patterns of woody species. The hump‐shaped patterns of elevational gamma and alpha diversity for herbaceous species were also significantly correlated, but the concordance between the alpha diversity of herbaceous species and local gamma diversity was stronger. Elevational patterns of alpha diversity were coarsely consistent across grain sizes, although the patterns became more pronounced at larger grain sizes.Main conclusionsThe correspondence of elevational gamma and alpha diversity was largely scale invariant, implying that elevational and possibly other geographical diversity patterns can reliably be studied at different spatial scales. Nonetheless, the alpha diversity pattern was the least pronounced at fine grain size, particularly for woody life‐forms. This finding suggests that for large‐scale patterns such as elevational gradients at regional or continental scales, coarse grain sizes and large areas for gamma estimation are more appropriate.

Molecular investigation of protistan diversity along an elevation transect of alpine lakes

AME Aquatic Microbial Ecology Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials AME 78:25-37 (2016) - DOI: https://doi.org/10.3354/ame01798 Molecular investigation of protistan diversity along an elevation transect of alpine lakes Lars Grossmann1,*, Manfred Jensen1, Ram Vinay Pandey2, Steffen Jost1, David Bass3,4, Roland Psenner5, Jens Boenigk1 1Biodiversity Department and Centre for Water and Environmental Research, University of Duisburg-Essen, 45141 Essen, Germany 2Institute of Population Genetics, Veterinaerplatz 1, 1210 Vienna, Austria 3Department of Life Sciences, Natural History Museum, London SW7 5BD, UK 4Centre for Environment, Fisheries and Aquaculture Science (Cefas), Barrack Road, The Nothe, Weymouth, Dorset DT4 8UB, UK 5Institute of Ecology, University of Innsbruck, Technikerstrasse 25, 6020 Innsbruck, Austria *Corresponding author: lars.grossmann@uni-due.de ABSTRACT: Ecological gradients are one of the main reasons for changes in biodiversity. However, whether what is known to be true for plants and animals also applies to protists in the same way is largely unknown. Along an alpine elevation gradient, including 29 freshwater lakes, we investigated ecological drivers of protistan diversity and community structure, as well as the explanatory value of the species-area relationship for protistan diversity using a deep-sequencing approach. We found that species richness does not decrease with elevation, nor is elevation a major factor explaining the observed shifts in community composition. The observed protistan communities differ depending on many factors, with pH and nutrient concentrations being most important. Considering distinct subgroups, Chrysophyceae accurately reflect the pattern of the overall protistan community. Within the investigated elevation gradient, species richness was correlated with the area of individual lakes irrespective of their elevation. However, we found no support for decreasing species richness with elevation, as known for plants and animals. KEY WORDS: Eukaryotic microbial diversity · High throughput sequencing · Algae · Protozoa · Chrysophytes · Evenness · Dinophyta Full text in pdf format Supplement 1Supplement 2 PreviousNextCite this article as: Grossmann L, Jensen M, Pandey RV, Jost S, Bass D, Psenner R, Boenigk J (2016) Molecular investigation of protistan diversity along an elevation transect of alpine lakes. Aquat Microb Ecol 78:25-37. https://doi.org/10.3354/ame01798 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AME Vol. 78, No. 1. Online publication date: November 17, 2016 Print ISSN: 0948-3055; Online ISSN: 1616-1564 Copyright © 2016 Inter-Research.

Snowbeds are more affected than other subalpine-alpine plant communities by climate change in the Swiss Alps.

While the upward shift of plant species has been observed on many alpine and nival summits, the reaction of the subalpine and lower alpine plant communities to the current warming and lower snow precipitation has been little investigated so far. To this aim, 63 old, exhaustive plant inventories, distributed along a subalpine–alpine elevation gradient of the Swiss Alps and covering different plant community types (acidic and calcareous grasslands; windy ridges; snowbeds), were revisited after 25–50 years. Old and recent inventories were compared in terms of species diversity with Simpson diversity and Bray–Curtis dissimilarity indices, and in terms of community composition with principal component analysis. Changes in ecological conditions were inferred from the ecological indicator values. The alpha‐diversity increased in every plant community, likely because of the arrival of new species. As observed on mountain summits, the new species led to a homogenization of community compositions. The grasslands were quite stable in terms of species composition, whatever the bedrock type. Indeed, the newly arrived species were part of the typical species pool of the colonized community. In contrast, snowbed communities showed pronounced vegetation changes and a clear shift toward dryer conditions and shorter snow cover, evidenced by their colonization by species from surrounding grasslands. Longer growing seasons allow alpine grassland species, which are taller and hence more competitive, to colonize the snowbeds. This study showed that subalpine–alpine plant communities reacted differently to the ongoing climate changes. Lower snow/rain ratio and longer growing seasons seem to have a higher impact than warming, at least on plant communities dependent on long snow cover. Consequently, they are the most vulnerable to climate change and their persistence in the near future is seriously threatened. Subalpine and alpine grasslands are more stable, and, until now, they do not seem to be affected by a warmer climate.

Decomposition of beech (Fagus sylvatica) and pine (Pinus nigra) litter along an Alpine elevation gradient: Decay and nutrient release

Litter decomposition is an important process for cycling of nutrients in terrestrial ecosystems. The objective of this study was to evaluate direct and indirect effects of climate on litter decomposition along an altitudinal gradient in a temperate Alpine region. Foliar litter of European beech (Fagus sylvatica) and Black pine (Pinus nigra) was incubated in litterbags during two years in the Hochschwab massif of the Northern Limestone Alps of Austria. Eight incubation sites were selected following an altitudinal/climatic transect from 1900 to 900masl. The average remaining mass after two years of decomposition amounted to 54% (beech) and 50% (pine). Net release of N, P, Na, Al, Fe and Mn was higher in pine than in beech litter due to high immobilization (retention) rates of beech litter. However, pine litter retained more Ca than beech litter. Altitude retarded decay (mass loss and associated C release) in beech litter during the first year only but had a longer lasting effect on decaying pine litter. Altitude comprises a suite of highly auto-correlated characteristics (climate, vegetation, litter, soil chemistry, soil microbiology, snow cover) that influence litter decomposition. Hence, decay and nutrient release of incubated litter is difficult to predict by altitude, except during the early stage of decomposition, which seemed to be controlled by climate. Reciprocal litter transplant along the elevation gradient yielded even relatively higher decay of pine litter on beech forest sites after a two-year adaptation period of the microbial community.

Application of Cable Erection Method to Construction of Concrete Arch Bridge in Alpine and High Elevation Area

1# bridge traffic engineering of LiangHeKou hydropower station is located in ganzi region in sichuan province. The altitude of main construction areas lies above the 2700m, perennial mean temperature ranges from-4.9 – 7.9°C,extreme low temperature reach-42.9°C,the temperature difference between day and night,which may adversely affect the execution of the precast concrete and cable erection. Based on the fully and deeply analyse and optimal approaches, We solved several key engineering challenges in precast arch box construction, and also provided valuable experiences for similar projects.

Lignin decomposition along an Alpine elevation gradient in relation to physicochemical and soil microbial parameters

Lignin is an aromatic plant compound that decomposes more slowly than other organic matter compounds; however, it was recently shown that lignin could decompose as fast as litter bulk carbon in minerals soils. In alpine Histosols, where organic matter dynamics is largely unaffected by mineral constituents, lignin may be an important part of soil organic matter (SOM). These soils are expected to experience alterations in temperature and/or physicochemical parameters as a result of global climate change. The effect of these changes on lignin dynamics remains to be examined and the importance of lignin as SOM compound in these soils evaluated. Here, we investigated the decomposition of individual lignin phenols of maize litter incubated for 2 years in-situ in Histosols on an Alpine elevation gradient (900, 1300, and 1900 m above sea level); to this end, we used the cupric oxide oxidation method and determined the phenols' (13) C signature. Maize lignin decomposed faster than bulk maize carbon in the first year (86 vs. 78% decomposed); however, after the second year, lignin and bulk C decomposition did not differ significantly. Lignin mass loss did not correlate with soil temperature after the first year, and even correlated negatively at the end of the second year. Lignin mass loss also correlated negatively with the remaining maize N at the end of the second year, and we interpreted this result as a possible negative influence of nitrogen on lignin degradation, although other factors (notably the depletion of easily degradable carbon sources) may also have played a role at this stage of decomposition. Microbial community composition did not correlate with lignin mass loss, but it did so with the lignin degradation indicators (Ac/Al)s and S/V after 2 years of decomposition. Progressing substrate decomposition toward the final stages thus appears to be linked with microbial community differentiation.