Anticoccidial activity of the secondary metabolites in alpine plants frequently ingested by wild Japanese rock ptarmigans.

The Japanese rock ptarmigan (Lagopus muta japonica) is an herbivorous species of partridges that inhabits only alpine zones. Alpine plants are their main source of food. These alpine plants contain toxic compounds to deter herbivores from consuming them. A previous analysis of the alpine plants frequently consumed by Japanese rock ptarmigans revealed the presence of a unique mixture of secondary metabolites and a novel compound. Additionally, wild Japanese rock ptarmigans are often infected by two species of Eimeria parasites. When these parasites were experimentally administered to Svalbard rock ptarmigans (Lagopus muta hyperborean), which do not feed on alpine plants, the birds exhibited symptoms, such as diarrhea and depression, and in some cases, they died. Although little is known about the pathogenesis of these parasites in wild Japanese rock ptarmigans, it was hypothesized that compounds found in alpine plants, their main food source, may reduce the pathogenicity of Eimeria parasites. In the present study, we evaluated the anticoccidial activity of the compounds derived from alpine plants in vitro using Eimeria tenella, which infects chickens belonging to the same pheasant family, as an experimental model. Twenty-seven natural components were extracted from eight alpine plants. The natural components were added to E. tenella sporozoites and incubated for 24 h to evaluate their direct effect. Additionally, Madin-Darby bovine kidney cells were incubated with sporozoites and natural components for 24 h to evaluate the inhibitory effect of the components on sporozoite cell invasion. Six compounds from four alpine plants decreased sporozoite viability by up to 88.3%, and two compounds inhibited sporozoite invasion into the cells. Although further studies are needed to evaluate the effects of these components against Eimeria infections in vivo, our findings suggest that these alpine plants may reduce the degree of infection by decreasing the number of sporozoites in the intestinal tract.

Response of alpine vegetation function to climate change in the Tibetan Plateau: A perspective from solar-induced chlorophyll fluorescence.

Vegetation change in the Tibetan Plateau (TP) is a crucial indicator of climate change in alpine regions. Previous studies have reported an overall greening trend in the vegetation structure across the TP, especially in its northeastern part, in response to a warming climate. However, variations in the vegetation function and the possible drivers remain poorly understood. Considering the optimal temperature for plants in TP is usually higher than the current temperature, our hypothesis is the function and structure of alpine vegetation have changed synchronously over past few decades. To test this hypothesis, we analyzed satellite-observed solar-induced chlorophyll fluorescence (SIF) and leaf area index (LAI) in the Yellow River source (YRS) region in the northeastern TP to quantify the long-term trends in vegetation functional and structural states, respectively. The results suggest that from 1982 to 2018, SIF increased significantly in 77.71 % of the YRS area, resulting in a significant upward trend of 0.52 × 10-3 mW m-2 nm-1 sr-1 yr-1 (p < 0.001) for the regional-mean SIF. This represents a 16.1 % increase in SIF, which is close in magnitude to the increase in LAI over the same period. The synchronous changes between vegetation function and structure suggest that improved greenness corresponds to a similar level of change in carbon uptake across YRS. Additionally, we used a multiple regression approach to quantify the contribution of climatic factors to SIF changes in YRS. Our analyses show that the increases in SIF were primarily driven by rising temperatures. Spatially, temperature dominated SIF changes in most parts of YRS, except for certain dry parts in the northern and western YRS, where precipitation had a greater impact. Our results are crucial for a comprehensive understanding of climate regulations on vegetation structure and function in high-elevation regions.

Survival in nunatak and peripheral glacial refugia of three alpine plant species is partly predicted by altitudinal segregation.

Mountain biota survived the Quaternary cold stages most probably in peripheral refugia and/or ice-free peaks within ice-sheets (nunataks). While survival in peripheral refugia has been broadly demonstrated, evidence for nunatak refugia is still scarce. We generated RADseq data from three mountain plant species occurring at different elevations in the southeastern European Alps to investigate the role of different glacial refugia during the Last Glacial Maximum (LGM). We tested the following hypotheses. (i) The deep Piave Valley forms the deepest genetic split in the species distributed across it, delimiting two peripheral refugia. (ii) The montane to alpine species Campanula morettiana and Primula tyrolensis survived the LGM in peripheral refugia, while high-alpine to subnival Saxifraga facchinii likely survived in several nunatak refugia. (iii) The lower elevation species suffered a strong population decline during the LGM. By contrast, the higher elevation species shows long-term stability of population sizes due to survival on permanently ice-free peaks and small population sizes at present. We found peripheral refugia on both sides of the Piave Valley, which acted as a major genetic barrier. Demographic modelling confirmed nunatak survival not only for S. facchinii but also for montane to alpine C. morettiana. Altitudinal segregation influenced the species' demographic fluctuations, with the lower elevation species showing a significant population increase at the end of the LGM, and the higher elevation species either showing decrease towards the present or stable population sizes with a short bottleneck. Our results highlight the role of nunatak survival and species ecology in the demographic history of mountain species.

Warming affects leaf light use efficiency and functional traits in alpine plants: evidence from a 4-year in-situ field experiment.

Introduction: Light use efficiency (LUE) is a crucial determinant of plant productivity, while leaf functional traits directly affect ecosystem functions. However, it remains unclear how climate warming affects LUE and leaf functional traits of dominant species in alpine meadows. Methods: We conducted a 4-year in-situ field warming experiment to investigate the eco-physiological characteristics for a dominant species (Elymus nutans) and a common species (Potentilla anserina) on the Tibetan Plateau. The leaf traits, photosynthesis and fluorescence characteristics were measured, along with the soil physical-chemical properties associated with the two species. Results and discussions: Experimental warming increased the leaf LUE, maximum photochemical efficiency, non-photochemical quenching, relative water content and specific leaf area for both species. However, there was a decrease in leaf and soil element content. Different species exhibit varying adaptability to warming. Increasing temperature significantly increased the photosynthetic rate, stomatal conductance, transpiration rate, total water content, and specific leaf volume of E. nutans; however, all these traits exhibited an opposite trend in P. anserina. Warming has a direct negative impact on leaf LUE and an indirectly enhances LUE through its effects on leaf traits. The impact of warming on plant photosynthetic capacity is primarily mediated by soil nutrients and leaf traits. These results indicate that the two different species employ distinct adaptive strategies in response to climate change, which are related to their species-specific variations. Such changes can confer an adaptive advantage for plant to cope with environmental change and potentially lead to alterations to ecosystem structure and functioning.

An investigation into the potential for upward range expansion in high-montane species on the roof of the world.

Climate warming is occurring in high-mountain areas at a faster rate than the global average. To escape the increasing temperatures, alpine species may shift in distribution upwards, threatening cold-adapted nival plant specialists. However, little is known about the success of seedling emergence and establishment at high altitudes outside the current range, particularly in the highest mountain areas of the Himalayas. We selected four native alpine species occurring around 4000 m a.s.l. and sowed seeds at the natural growing site (GS), at a high elevation site (HS; 5000 m a.s.l.) and at high elevation with soil from the growing site (HS-S) in the Khumbu Valley, north-eastern Nepal. We monitored seedling emergence and establishment for two consecutive years. Seedling emergence and establishment varied between species. Emergence was similar between GS and HS and improved at HS-S. Establishment was low at high elevations with all but one species having high mortality after winter. Seedling emergence of low elevation plants is possible at high elevations in the Everest region, indicating species may be able to shift their distribution range upwards. However, successful establishment may be limited by the soil and high winter mortality at high elevations, although not in all species. Climate warming will potentially lead to upward migration of some Himalayan plant species, leading to altered community composition in high-mountain areas.

Genome Size in the Arenaria ciliata Species Complex (Caryophyllaceae), with Special Focus on Northern Europe and the Arctic.

The main aim of the present study has been the completion of genome size data for the diverse arctic-alpine A. ciliata species complex, with special focus on the unexplored arctic taxon A. pseudofrigida, the north-European A. norvegica, and A. gothica from Gotland (Sweden). Altogether, 46 individuals of these three Nordic taxa have been sampled from seven different regions and their genome size estimated using flow cytometry. Three other alpine taxa in the A. ciliata complex (A. multicaulis, A. ciliata subsp. ciliata, and A. ciliata subsp. bernensis) were also collected and analyzed for standardization purposes, comprising 20 individuals from six regions. A mean 2c value of 1.65 pg of DNA was recorded for A. pseudofrigida, 2.80 pg for A. norvegica, and 4.14 pg for A. gothica, as against the reconfirmed 2c value of 1.63 pg DNA for the type taxon A. ciliata subsp. ciliata. Our results presenting the first estimations of genome sizes for the newly sampled taxa, corroborate ploidy levels described in the available literature, with A. pseudofrigida being tetraploid (2n = 4x = 40), A. norvegica possessing predominantly 2n = 8x = 80, and A. gothica with 2n = 10x = 100. The present study also reconfirms genome size and ploidy level estimations published previously for the alpine members of this species complex. Reflecting a likely complex recent biogeographic history, the A. ciliata species group comprises a polyploid arctic-alpine species complex characterized by reticulate evolution, polyploidizations and hybridizations, probably associated with rapid latitudinal and altitudinal migrations in the Pleistocene-Holocene period.

Competitors alter selection on alpine plants exposed to experimental climate change.

Investigating how climate change alters selection regimes is a crucial step toward understanding the potential of populations to evolve in the face of changing conditions. Previous studies have mainly focused on understanding how changing climate directly influences selection, while the role of species' interactions has received little attention. Here, we used a transplant experiment along an elevation gradient to estimate how climate warming and competitive interactions lead to shifts in directional phenotypic selection on morphology and phenology of four alpine plants. We found that warming generally imposed novel selection, with the largest shifts in regimes acting on specific leaf area and flowering time across species. Competitors instead weakened the selection acting on traits that was imposed directly by warming. Weakened or absent selection in the presence of competitors was largely associated with the suppression of absolute means and variation of fitness. Our results suggest that although climate change can impose strong selection, competitive interactions within communities might act to limit selection and thereby stymie evolutionary responses in alpine plants facing climate change.

Species-Specific Responses to Human Trampling Indicate Alpine Plant Size Is More Sensitive than Reproduction to Disturbance.

Human disturbance, such as trampling, is an integral component of global change, yet we lack a comprehensive understanding of its effects on alpine ecosystems. Many alpine systems are seeing a rapid increase in recreation and in understudied regions, such as the Coast Mountains of British Columbia, yet disturbance impacts on alpine plants remain unclear. We surveyed disturbed (trail-side) and undisturbed (off-trail) transects along elevational gradients of popular hiking trails in the T'ak't'ak'múy'in tl'a In'inyáxa7n region (Garibaldi Provincial Park), Canada, focusing on dominant shrubs (Phyllodoce empetriformis, Cassiope mertensiana, Vaccinium ovalifolium) and graminoids (Carex spp). We used a hierarchical Bayesian framework to test for disturbance by elevation effects on total plant percent cover, maximum plant height and diameter (growth proxies), and buds, flowers, and fruits (reproduction proxies). We found that trampling reduces plant cover and impacts all species, but that effects vary by species and trait, and disturbance effects only vary with elevation for one species' trait. Growth traits are more sensitive to trampling than reproductive traits, which may lead to differential impacts on population persistence and species-level fitness outcomes. Our study highlights that disturbance responses are species-specific, and this knowledge can help land managers minimize disturbance impacts on sensitive vegetation types.

Extent of intraspecific trait variability in ecologically central and marginal populations of a dominant alpine plant across European mountains.

BACKGROUND AND AIMS: Studying trait variability and restricted gene flow between populations of species can reveal species dynamics. Peripheral populations commonly exhibit lower genetic diversity and trait variability due to isolation and ecological marginality, unlike central populations experiencing gene flow and optimal conditions. This study focused on Carex curvula, the dominant species in alpine acidic meadows of European mountain regions. The species is sparser in dry areas such as the Pyrenees and Balkans, compared to the Central-Eastern Alps and Carpathians. We hypothesized that distinct population groups could be identified based on their mean functional trait values and their correlation with the environment; we predicted that ecologically marginal populations would have stronger trait correlations, lower within-population trait variability (intraspecific trait variability, ITV) and lower genetic diversity than populations of optimal habitats. METHODS: Sampling was conducted in 34 populations that spanned the entire distribution range of C. curvula. We used hierarchical clustering to identify emergent functional groups of populations, defined by combinations of multiple traits associated with nutrient economy and drought tolerance (e.g. specific leaf area, anatomy). We contrasted the geographical distribution of these groups in relation to environment and genetic structure. We compared pairwise trait relationships, within-population trait variation (ITV) and neutral genetic diversity between groups. KEY RESULTS: Our study identified emergent functional groups of populations. Those in the southernmost ranges, specifically the Pyrenees and Balkan region, showed drought-tolerant trait syndromes and correlated with indicators of limited water availability. While we noted a decline in population genetic diversity, we did not observe any significant changes in ITV in ecologically marginal (peripheral) populations. CONCLUSIONS: Our research exemplifies the relationship between ecological marginality and geographical peripherality, which in this case study is linked to genetic depauperation but not to reduced ITV. Understanding these relationships is crucial for understanding the biogeographical factors shaping trait variation.

Elevation provenance affects photosynthesis and its acclimation to temperature in the high-Andes alpine herb Phacelia secunda.

We analysed whether Phacelia secunda populations from different elevations exhibit intrinsic traits associated with diffusive and biochemical components of photosynthesis, and if they differ in acclimation of photosynthesis to warmer temperatures. We hypothesized that P. secunda will have similar photosynthetic performance regardless of altitudinal provenance and that plants from high elevations will have a lower photosynthetic acclimation capacity to higher temperature than plants from low elevations. Plants from 1600, 2800 and 3600 m a.s.l. in the central Chilean Andes were collected and grown under two temperature regimes (20/16 °C and 30/26 °C day/night). The following photosynthetic traits were measured in each plant for the two temperature regimes: AN , gs , gm , Jmax , Vcmax , Rubisco carboxylation kcat c . Under a common growth environment, plants from the highest elevation had slightly lower CO2 assimilation rates compared to lower elevation plants. While diffusive components of photosynthesis increased with elevation provenance, the biochemical component decreased, suggesting compensation that explains the similar rates of photosynthesis among elevation provenances. Plants from high elevations had lower photosynthetic acclimation to warmer temperatures compared to plants from lower elevations, and these responses were related to elevational changes in diffusional and biochemical components of photosynthesis. Plants of P. secunda from different elevations maintain photosynthetic traits when grown in a common environment, suggesting low plasticity to respond to future climate changes. The fact that high elevation plants had lower photosynthetic acclimation to warmer temperature suggests higher susceptibility to increases in temperature associated with global warming.

Genome-environment associations along elevation gradients in two snowbed species of the North-Eastern Calcareous Alps.

BACKGROUND: Anthropogenic climate change leads to increasing temperatures and altered precipitation and snowmelt patterns, especially in alpine ecosystems. To understand species' responses to climate change, assessment of genetic structure and diversity is crucial as the basis for the evaluation of migration patterns, genetic adaptation potential as well as the identification of adaptive alleles. RESULTS: We studied genetic structure, diversity and genome-environment associations of two snowbed species endemic to the Eastern Alps with a large elevational range, Achillea clusiana Tausch and Campanula pulla L. Genotyping-by-sequencing was employed to assemble loci de novo, call variants and perform population genetic analyses. Populations of either species were distinguishable by mountain, and to some extent by elevation. We found evidence for gene flow between elevations. Results of genome-environment associations suggested similar selective pressures acting on both species, emanating mainly from precipitation and exposition rather than temperature. CONCLUSIONS: Given their genetic structure and amount of gene flow among populations the two study species are suitable to serve as a model for genetic monitoring of climate change adaptation along an elevation gradient. Consequences of climate change will predominantly manifest via changes in precipitation and, thus, duration of snow cover in the snowbeds and indirectly via shrub encroachment accompanied by increasing shading of snowbeds at lower range margins. Assembling genomes of the study species and studying larger sample sizes and time series will be necessary to functionally characterize and validate the herein identified genomic loci putatively involved in adaptive processes.

Development of SSR markers for Carex curvula (Cyperaceae) and their importance in investigating the species genetic structure.

BACKGROUND: Microsatellite primers were developed and tested to genotype several populations of Carex curvula s. l. (Cyperaceae), in order to infer the phylogeographic relationships of the populations within species and the boundaries between the two described subspecies: C. curvula subsp. curvula and C. curvula subsp. rosae. METHODS AND RESULTS: Candidate microsatellite loci were isolated based on next-generation sequencing. We tested 18 markers for polymorphism and replicability in seven C. curvula s. l. populations and identified 13 polymorphic loci with dinucleotide repeats. Genotyping results showed the total number of alleles per locus varied from four to 23 (including both infrataxa), and the observed and expected heterozygosity ranged between 0.1 to 0.82 and 0.219 to 0.711, respectively. Furthermore, the NJ tree showed a clear separation between C. curvula subsp. curvula and C. curvula subsp. rosae. CONCLUSION: The development of these highly polymorphic markers proved to be very efficient not only in delineating between the two subspecies, but also in genetic discriminating at population level within each infrataxon. They are promising tools for evolutionary studies in Cariceae section, as well as in providing knowledge on patterns of the species phylogeography.

Diversified chemical profiles of cuticular wax on alpine meadow plants of the Qinghai-Tibet Plateau.

MAIN CONCLUSION: The alpine meadow plants showed great intra- and inter-genera variations of chemical profiles of cuticular waxes. Developing an understanding of wax structure-function relationships that will help us tackle global climate change requires a detailed understanding of plant wax chemistry. The goal in this study was to provide a catalog of wax structures, abundances, and compositions on alpine meadow plants. Here, leaf waxes from 33 plant species belonging to 11 families were sampled from alpine meadows of the east side of the Qinghai-Tibet Plateau. Across these species, total wax coverage varied from 2.30 µg cm-2 to 40.70 µg cm-2, showing variation both within as well as between genera and suggesting that wax variation is subject to both environmental and genetic effects. Across all wax samples, more than 140 wax compounds belonging to 13 wax compound classes were identified, including both ubiquitous wax compounds and lineage-specific compounds. Among the ubiquitous compounds (primary alcohols, alkyl esters, aldehydes, alkanes, and fatty acids), chain length profiles across a wide range of species point to key differences in the chain length specificity of alcohol and alkane formation machinery. The lineage-specific wax compound classes (diols, secondary alcohols, lactones, iso-alkanes, alkyl resorcinols, phenylethyl esters, cinnamate esters, alkyl benzoates, and triterpenoids) nearly all consisted of isomers with varying chain lengths or functional group positions, making the diversity of specialized wax compounds immense. The comparison of species relationships between chemical data and genetic data highlighted the importance of inferring phylogenetic relationships from data sets that contain a large number of variables that do not respond to environmental stimuli.

Genomic convergence underlying high-altitude adaptation in alpine plants.

Evolutionary convergence is one of the most striking examples of adaptation driven by natural selection. However, genomic evidence for convergent adaptation to extreme environments remains scarce. Here, we assembled reference genomes of two alpine plants, Saussurea obvallata (Asteraceae) and Rheum alexandrae (Polygonaceae), with 37,938 and 61,463 annotated protein-coding genes. By integrating an additional five alpine genomes, we elucidated genomic convergence underlying high-altitude adaptation in alpine plants. Our results detected convergent contractions of disease-resistance genes in alpine genomes, which might be an energy-saving strategy for surviving in hostile environments with only a few pathogens present. We identified signatures of positive selection on a set of genes involved in reproduction and respiration (e.g., MMD1, NBS1, and HPR), and revealed signatures of molecular convergence on genes involved in self-incompatibility, cell wall modification, DNA repair and stress resistance, which may underlie adaptation to extreme cold, high ultraviolet radiation and hypoxia environments. Incorporating transcriptomic data, we further demonstrated that genes associated with cuticular wax and flavonoid biosynthetic pathways exhibit higher expression levels in leafy bracts, shedding light on the genetic mechanisms of the adaptive "greenhouse" morphology. Our integrative data provide novel insights into convergent evolution at a high-taxonomic level, aiding in a deep understanding of genetic adaptation to complex environments.

Warming delays but grazing advances leaf senescence of five plant species in an alpine meadow.

Leaf senescence is the final stage in the life cycle of leaves and is critical to plants' fitness as well as to ecosystem carbon and nutrient cycling. To date, most understanding about the responses of leaf senescence to environmental changes has derived from research in forests, but the topic has been relatively neglected, especially under grazing conditions, in natural grasslands. We conducted a 3-year manipulative asymmetric warming with moderate grazing experiment to explore the responses of leaf senescence of five main species in an alpine meadow on the Qinghai-Tibetan Plateau. We found that warming prolonged leaf longevity through earlier leaf-out and later leaf senescence, and grazing prolonged it through a greater advance in leaf-out than first leaf coloration for all plants. Warming did not affect leaf nitrogen (N) content or N resorption efficiency (NRE), but grazing increased N content in coloring leaves for P. anserine and P. nivea and decreased NRE for K. humilis, P. anserine under no-warming, and for P. nivea under warming. The interactive effects of warming and grazing on leaf phenology and leaf traits depended on species identity and year. There were positive relationships between leaf-out and leaf senescence mainly derived from grazing, and positive relationships between NRE from old leaves and leaf senescence for three out of five plant species. Therefore, our results indicated that earlier leaf-out could result in earlier leaf senescence only under grazing, but depending on plant species. Delayed leaf coloring increased NRE from old leaves for some plant species measured under warming and grazing. Our results suggested that alpine plants may develop strategies to adapt to warming and grazing to assimilate more carbon through prolonged leaf longevity rather than increased NRE through earlier leaf coloring in the alpine meadow.

Genome Size in the Arenaria ciliata Species Complex (Caryophyllaceae), with Special Focus on A. ciliata subsp. bernensis, a Narrow Endemic of the Swiss Northern Alps.

The genus Arenaria (Caryophyllaceae) comprises approximately 300 species worldwide; however, to date, just six of these taxa have been investigated in terms of their genome size. The main subject of the present study is the A. ciliata species complex, with special focus on A. ciliata subsp. bernensis, an endemic plant occurring in the Swiss Northern Alps. Altogether, 16 populations and 77 individuals of the A. ciliata complex have been sampled and their genome sizes were estimated using flow cytometry, including A. ciliata subsp. bernensis, A. ciliata s.str., A. multicaulis, and A. gothica. The Arenaria ciliata subsp. bernensis shows the highest 2c-value of 6.91 pg of DNA, while A. gothica showed 2c = 3.69 pg, A. ciliata s.str. 2c = 1.71 pg, and A. multicaulis 2c = 1.57 pg. These results confirm the very high ploidy level of A. ciliata subsp. bernensis (2n = 20x = 200) compared to other taxa in the complex, as detected by our chromosome counting and previously documented by earlier work. The genome size and, thus, also the ploidy level, is stable across the whole distribution area of this taxon. The present study delivers additional support for the taxonomic distinctiveness of the high alpine endemic A. ciliata subsp. bernensis, which strongly aligns with other differences in morphology, phylogeny, phenology, ecology, and plant communities, described previously. In affirming these differences, further support now exists to re-consider the species status of this taxon. Upgrading to full species rank would significantly improve the conservation prospects for this taxon, as, because of its precise ecological adaptation to alpine summit habitats, the A. ciliata subsp. bernensis faces acute threats from accelerated climate warming.

Ecological lags govern the pace and outcome of plant community responses to 21st-century climate change.

Forecasting the trajectories of species assemblages in response to ongoing climate change requires quantifying the time lags in the demographic and ecological processes through which climate impacts species' abundances. Since experimental climate manipulations are typically abrupt, the observed species responses may not match their responses to gradual climate change. We addressed this problem by transplanting alpine grassland turfs to lower elevations, recording species' demographic responses to climate and competition, and using these data to parameterise community dynamics models forced by scenarios of gradual climate change. We found that shifts in community structure following an abrupt climate manipulation were not simply accelerated versions of shifts expected under gradual warming, as the former missed the transient rise of species benefiting from moderate warming. Time lags in demography and species interactions controlled the pace and trajectory of changing species' abundances under simulated 21st-century climate change, and thereby prevented immediate diversity loss.

Acclimation to water stress improves tolerance to heat and freezing in a common alpine grass.

Alpine plants in Australia are increasingly exposed to more frequent drought and heatwaves, with significant consequences for physiological stress responses. Acclimation is a critical feature that allows plants to improve tolerance to environmental extremes by directly altering their physiology or morphology. Yet it is unclear how plant performance, tolerance, and recovery are affected when heat and water stress co-occur, and whether prior exposure affects responses to subsequent climate extremes. We grew a common alpine grass species under high or low watering treatments for three weeks before exposure to either none, one, or two heat stress events. We determined photosynthetic heat and freezing tolerance (LT50, mean temperature causing 50% irreversible damage to photosystem II) and growth. Physiological adjustments to low watering, including more negative water potentials and reduced growth, were also characterised by improved tolerance to high and low-temperature extremes. Shifts to higher heat tolerance were also evident with increasing exposure to heat stress events, though freezing tolerance was not affected. Acclimation effects were mostly short-term, however; prior exposure to heat and/or water stress had little to no effect on growth and thermal tolerance following the six-week recovery period. We conclude that rapid acclimation to water and heat stress that co-occur during summer enhances the capacity of alpine plants to tolerate increasingly frequent temperature extremes.

Air or soil temperature matters the responses of alpine plants in biomass accumulation to climate warming.

Climate change has substantially affected plant phenology and growth on the Qinghai-Tibetan Plateau (QTP), while it remains unclear how plant phenology and growth impact the plant biomass under climate change. We used long-term data (from 1997 to 2017) for four plants, Stipa purpurea, Artemisia scoparia, Kobresia humilis and Astragalus laxmannii in the alpine meadow to examine the relationships among multiple climate factors, vegetative growth, reproductive growth, intrinsic growth rate and biomass. The order of returning to green determines the growth strategies of different plants, the earliest plants to green (p < 0.05) (e.g., Stipa purpurea and Artemisia scoparia) would choose the strategy of vegetative growth (p < 0.05); the earlier plants (p < 0.05) (e.g., Kobresia humilis) would be regulated by both vegetative growth and reproductive growth (p < 0.05); while the latest plant to green (p < 0.05) such as Astragalus laxmannii, would choose intrinsic growth rate rather than growing season (P < 0.05). Temperature was the most important drivers for key phenological phases and growth patterns of four species, different factors play a role in different stages of the growth period, i.e., in the early and late stage is the soil temperature, while in the middle stage is the average temperature or the maximum temperature, and all the optimum thresholds were >30 day. These findings provide the in-situ evidences of long-term changes in phenology and its associated growth on the biomass of alpine plants on the QTP in the era of climate change.

Spatial variations of root-associated bacterial communities of alpine plants in the Qinghai-Tibet Plateau.

Exploring the geospatial variation of root-associated microbiomes is critical for understanding plant-microbe-environment interactions and plant environmental adaptability. Root-associated bacterial communities from the three compartments [rhizosphere surrounding soil (RSS), rhizosphere soil (rhizosphere), and root endosphere (endophytic)] are influenced by multiple factors, including plant species and geographical locations. Nonetheless, these communities remain poorly understood under harsh conditions. In this study, we selected four dominant alpine plants on the Qinghai-Tibet Plateau (i.e., Elymus nutans, Festuca sinensis, Kobresia pygmaea, and Kobresia humilis) to investigate their root-associated bacterial communities across 11 geographical locations and determine the factors driving spatial variation. The results showed that the microbiota of the three compartments had significantly different community compositions, with more Pseudomonadaceae and Enterobacteriaceae present in the endosphere. Spatial variations in root endophytic microbiota were mainly governed by stochastic processes, which were different from the deterministic processes in the other two compartments. Meanwhile, the geographical location had greater effects on bacterial communities than plant species, and the spatial variation of α-diversity in the endosphere was much higher than that in the RSS and rhizosphere. We further found that the differentiation of bacterial diversity in the endosphere among sympatric plant species was enhanced by higher annual precipitation, lower soil nutrients (carbon and nitrogen), and pH. For example, the coefficient of variation of endosphere Pseudomonadaceae abundance was positively correlated with annual mean precipitation, whereas that of Enterobacteriaceae abundance was negatively correlated with soil pH. The co-occurrence network analysis identified a higher proportion of bacterial coexistence in the endosphere (70.9%) than in the RSS (49.5%) and rhizosphere soil (50.9%). Finally, we revealed the relative convergence of endophytic communities among sympatric plant species in the alpine grasslands.