Encroachment drives facilitation at alpine shrublines

Ongoing encroachment is driving recent alpine shrubline dynamics globally,but the role of shrub-shrub interactions in shaping shrublines and their relationships with stem density changes remain poorly understood.Here,the size and age of shrubs from 26 Salix shrubline populations along a 900-km latitudinal gradient(30°-38°N)were measured and mapped across the eastern Tibetan Plateau.Point pattern analyses were used to quantify the spatial distribution patterns of juveniles and adults,and to assess spatial associations between them.Mean intensity of univariate and bivariate spatial patterns was related to biotic and abiotic variables.Bivariate mark correlation functions with a quantitative mark(shrub height,basal stem diameter,crown width)were also employed to investigate the spatial relationships between shrub traits of juveniles and adults.Structural equation models were used to explore the relationships among conspecific interactions,patterns,shrub traits and recruitment dynamics under climate change.Most shrublines showed clustered patterns,suggesting the existence of conspecific facilitation.Clustered patterns of juveniles and conspecific interactions(potentially facilitation)tended to intensify with increasing soil moisture stress.Summer warming before 2010 triggered positive effects on population interactions and spatial patterns via increased shrub recruitment.However,summer warming after2010 triggered negative effects on interactions through reduced shrub recruitment.Therefore,shrub recruitment shifts under rapid climate change could impact spatial patterns,alter conspecific interactions and modify the direction and degree of shrublines responses to climate.These changes would have profound implications for the stability of alpine woody ecosystems.

Assessing the Performance of a Dynamical Downscaling Simulation Driven by a Bias-Corrected CMIP6 Dataset for Asian Climate

In this study,we aim to assess dynamical downscaling simulations by utilizing a novel bias-corrected global climate model(GCM)data to drive a regional climate model(RCM)over the Asia-western North Pacific region.Three simulations were conducted with a 25-km grid spacing for the period 1980–2014.The first simulation(WRF_ERA5)was driven by the European Centre for Medium-Range Weather Forecasts Reanalysis 5(ERA5)dataset and served as the validation dataset.The original GCM dataset(MPI-ESM1-2-HR model)was used to drive the second simulation(WRF_GCM),while the third simulation(WRF_GCMbc)was driven by the bias-corrected GCM dataset.The bias-corrected GCM data has an ERA5-based mean and interannual variance and long-term trends derived from the ensemble mean of 18 CMIP6 models.Results demonstrate that the WRF_GCMbc significantly reduced the root-mean-square errors(RMSEs)of the climatological mean of downscaled variables,including temperature,precipitation,snow,wind,relative humidity,and planetary boundary layer height by 50%–90%compared to the WRF_GCM.Similarly,the RMSEs of interannual-tointerdecadal variances of downscaled variables were reduced by 30%–60%.Furthermore,the WRF_GCMbc better captured the annual cycle of the monsoon circulation and intraseasonal and day-to-day variabilities.The leading empirical orthogonal function(EOF)shows a monopole precipitation mode in the WRF_GCM.In contrast,the WRF_GCMbc successfully reproduced the observed tri-pole mode of summer precipitation over eastern China.This improvement could be attributed to a better-simulated location of the western North Pacific subtropical high in the WRF_GCMbc after GCM bias correction.

Different xylogenesis responses to atmospheric water demand contribute to species coexistence in a mixed pine–oak forest

Seasonal patterns of wood formation(xylogenesis)remain understudied in mixed pine-oak forests despite their contribution to tree coexistence through temporal niche complementarity.Xylogenesis was assessed in three pine species(Pinus cembroides,Pinus leiophylla,Pinus engelmannii)and one oak(Quercus grisea)coexisting in a semi-arid Mexican forest.The main xylogenesis phases(production of cambium cells,radial enlargement,cell-wall thickening and maturation)were related to climate data considering 5-15-day temporal windows.In pines,cambium activity maximized from mid-March to April as temperature and evaporation increased,whereas cell radial enlargement peaked from April to May and was constrained by high evaporation and low precipitation.Cell-wall thickening peaked from June to July and in August-September as maximum temperature and vapour pressure deficit(VPD)increased.Maturation of earlywood and latewood tracheids occurred in May-June and June-July,enhanced by high minimum temperatures and VPD in P.engelmannii and P.leiophylla.In oak,cambial onset started in March,constrained by high minimum temperatures,and vessel radial enlargement and radial increment maximized in April as temperatures and evaporation increased,whereas early wood vessels matured from May to June as VPD increased.Overall,15-day wet conditions enhanced cell radial enlargement in P.leiophylla and P.engelmannii,whereas early-summer high 15-day temperature and VPD drove cell-wall thickening in P.cembroides.Warm night conditions and high evaporation rates during spring and summer enhanced growth.An earlier growth peak in oak and a higher responsiveness to spring-summer water demand in pines contributed to their coexistence.

Growth phenology adjusts to seasonal changes in water availability in coexisting evergreen and deciduous mediterranean oaks

Different leaf(evergreen vs.deciduous habit)and xylem(diffuse-vs.ring-porous wood)traits represent contrasting strategies to face seasonal changes in water availability and temperature.However,how contrasting leaf and xylem habits of coexisting tree species affect stem wood formation and tree-ring development remains poorly understood.Here,we investigated the spatio-temporal patterns of wood formation in two deciduous oaks(Quercus faginea and Quercus petraea)and two evergreen oaks(Quercus ilex and Quercus suber)coexisting in seasonally dry Mediterranean forests along an aridity gradient in Spain.We hypothesized that growth responses to drought and intra-and inter-annual growth patterns would differ between functional groups.We simulated intra-and interannual growth using a modified version of the Vaganov-Shashkin(VS)process-based,growth model.The VS model simulations were used to estimate growth changes under a high emission scenario(RCP 8.5)for the current distribution of the study oak species and to forecast their future performance under warm(4.8℃)conditions in the Iberian Peninsula.Our simulations indicate that climate warming would induce a shortening of the ringgrowth season and a reduction of radial growth in evergreen and deciduous Mediterranean oaks,particularly in dry sites from southern and eastern Iberia currently occupied by Q.ilex and Q.faginea.Evergreen oaks may better recover after dry periods than deciduous oaks by resuming growth after the summer drought.Low soil water availability in spring would be more detrimental to growth of deciduous oaks.Process-based growth models should be refined and validated to better forecast changes in tree growth as a function of climate.

Narcea—an unknown,ancient cultivated rose variety from northern Spain

The present work reports the discovery and the complete characterisation of an ancient cultivated rose variety found growing in a private garden in the southwest of the Principality of Asturias(northern Spain).The variety is here given the name Narcea.The majority of roses currently cultivated belong to the so-called group of‘Modern Roses’,all of which were obtained after 1867 via artificial crosses and improvement programmes.All are destined for ornamental use.Until the 19th century,the great majority of the many ancient cultivated roses in Europe were used in perfumery and cosmetics,or had medicinal uses.Rosa damascena and Rosa centifollia are still grown and used by the French and Bulgarian perfume industries.The Asturian Massif of the Cantabrian Mountain Range provides a natural habitat for some 75%of the wild members of the genus Rosa,but until now there was no evidence that this area was home to ancient cultivated roses.A complete botanical description is here provided for a discovered ancient rose.It is also characterised according to a series of sequence tagged microsatellite sites,and its agronomic features are reported.In addition,a histological description(optical and scanning electronic microscope studies)of the petals is offered,along with an analysis of the volatile compounds present in these organs as determined by solid phase microextraction and gas chromatography-mass spectroscopy.The results reveal the uniqueness of this ancient type of rose and suggest it may be of interest to the perfume industry.

Tree growth is more limited by drought in rear-edge forests most of the times

Background:Equatorward,rear-edge tree populations are natural monitors to estimate species vulnerability to climate change.According to biogeographical theory,exposition to drought events increases with increasing aridity towards the equator and the growth of southern tree populations will be more vulnerable to drought than in central populations.However,the ecological and biogeographical margins can mismatch due to the impact of ecological factors(topography,soils)or tree-species acclimation that can blur large-scale geographical imprints in trees responses to drought making northern populations more drought limited.Methods:We tested these ideas in six tree species,three angiosperms(Fagus sylvatica,Quercus robur,Quercus petraea)and three gymnosperms(Abies alba,Pinus sylvestris and Pinus uncinata)by comparing rear-edge tree populations subjected to different degrees of aridity.We used dendrochronology to compare the radial-growth patterns of these species in northern,intermediate,and southern tree populations at the continental rear edge.Results and conclusions:We found marked variations in growth variability between species with coherent patterns of stronger drought signals in the tree-ring series of the southern populations of F.sylvatica,P.sylvestris,and A.alba.This was also observed in species from cool-wet sites(P.uncinata and Q.robur),despite their limited responsiveness to drought.However,in the case of Q.petraea the intermediate population showed the strongest relationship to drought.For drought-sensitive species as F.sylvatica and P.sylvestris,southern populations presented more variable growth which was enhanced by cool-wet conditions from late spring to summer.We found a trend of enhanced vulnerability to drought in these two species.The response of tree growth to drought has a marked biogeographical component characterized by increased drought sensitivity in southern populations even within the species distribution rear edge.Nevertheless,the relationship between tree growth and drought varied between species suggesting that biogeographical and ecological limits do not always overlap as in the case of Q.petraea.In widespread species showing enhanced vulnerability to drought,as F.sylvatica and P.sylvestris,increased vulnerability to climate warming in their rear edges is forecasted.Therefore,we encourage the monitoring and conservation of such marginal tree populations.

喜马拉雅山不同森林群落主要树种叶片元素性状与生物量之间的关系

植物需要多种基本元素调节并保持其特定比例以维持生长发育,叶片元素含量反映了植物的功能及其对环境的适应性.然而,在森林海拔梯度上,我们对于资源获取、光合作用和生长相关的叶片元素如何调节森林生物量仍知之甚少.本研究在喜马拉雅山干城章嘉峰地区沿热带森林(海拔80m)至高山树线(海拔4200m)设置海拔梯度样带,每间隔海拔100m设置一个样点,对116个树种的1859个个体测定了叶片中10种元素(C、N、P、K、Ca、Mg、Zn、Fe、Cu和Mn)的含量,通过计算叶片元素含量的群落加权平均值(反映优势物种的性状优势度,表征质量比效应)和功能离散度(反映物种在生态位空间内的聚集或者离散程度,表征互补效应),探究叶片元素含量及其离散程度沿海拔梯度分异特征,解析其对森林群落生物量的影响.研究结果表明,较强的叶片元素质量比效应和较弱的互补效应有利于森林群落生物量的积累.叶片元素性状多样性与海拔的共同作用对生物量的解释量(解释方差:52.2%)高于元素性状多样性的解释量(解释方差:0.05%~21%).海拔调节了树种性状多样性在生物量积累中的作用,互补效应在低海拔和高海拔地区对生物量的影响分别体现为积极和消极作用,这表明海拔和互补效应之间也存在交互作用.此外,海拔和质量比效应的交互作用对海拔梯度上生物量的影响也存在异质性.本研究表明,不同森林群落生物量的积累可能受到由海拔调控的性状多样性的影响.尽管较高的性状分异不利于生物量的积累,但能增强高海拔地区树种对胁迫环境的适应性.

Linking leaf elemental traits to biomass across forest biomes in the Himalayas

Plants require a number of essential elements in different proportions for ensuring their growth and development.The elemental concentrations in leaves reflect the functions and adaptations of plants under specific environmental conditions.However,less is known about how the spectrum of leaf elements associated with resource acquisition,photosynthesis and growth regulates forest biomass along broad elevational gradients.We examined the influence of leaf element distribution and diversity on forest biomass by analyzing ten elements(C,N,P,K,Ca,Mg,Zn,Fe,Cu,and Mn)in tree communities situated every 100 meters along an extensive elevation gradient,ranging from the tropical forest(80 meters above sea level)to the alpine treeline(4200 meters above sea level)in the Kangchenjunga Landscape in eastern Nepal Himalayas.We calculated communityweighted averages(reflecting dominant traits governing biomass,i.e.,mass-ratio effect)and functional divergence(reflecting increased trait variety,i.e.,complementarity effect)for leaf elements in a total of 1,859 trees representing 116 species.An increasing mass-ratio effect and decreasing complementarity in leaf elements enhance forest biomass accumulation.A combination of elements together with elevation explains biomass(52.2%of the variance)better than individual elemental trait diversity(0.05%to 21%of the variance).Elevation modulates trait diversity among plant species in biomass accumulation.Complementarity promotes biomass at lower elevations,but reduces biomass at higher elevations,demonstrating an interaction between elevation and complementarity.The interaction between elevation and mass-ratio effect produces heterogeneous effects on biomass along the elevation gradient.Our research indicates that biomass accumulation can be disproportionately affected by elevation due to interactions among trait diversities across vegetation zones.While higher trait variation enhances the adaptation of species to environmental changes,it reduces biomass accumulation,especially at higher elevations.

喜马拉雅山区高山冰缘植物并不能从变暖中受益

普遍认为变暖有利于高山植被生态系统,并已经导致冰缘植物向高海拔的扩张.珠峰山谷金字塔气象站(海拔5050 m)1994~2018的气象记录显示,高海拔山区呈显著的暖干化趋势.然而,我们依然不清楚暖干化是否对冰缘植被更新和分布造成显著影响?本研究在喜马拉雅山中段3个山谷建立了8块(30 m×120 m)滇藏方枝柏(Juniperus indica)和高山柏(Juniperus squamata)灌木线样地(海拔介于4344~5074 m之间).样地调查揭示,自20世纪90年代之前所有样地种群更新呈增加的趋势,然而90年代以来更新持续下降.种群更新与春季、夏季温度之间呈现显著的负相关关系,暗示了暖干化加剧了水分胁迫,并限制了种群的更新.另外,近60年来所有灌木线位置稳定.近30年遥感数据也证实,研究区冰缘植被无变绿趋势,甚至出现2%-6%的植被生长减弱现象.因此,进一步研究应该探讨冰缘植被生长减弱对喜马拉雅山区水循环和生物多样性的影响.

Effects of the allelopathic plant Artemisia herba-alba Asso on the soil seed bank of a semi-arid plant community

Aims Seed bank strongly influences composition and structure of above-ground vegetation.Little attention has been paid to the role of allel-opathy driving soil seed bank dynamics,even though allelochemicals released by allelopathic plants might determine whether a species can or cannot germinate from the soil seed bank and,therefore,to co-exist in the neighborhood of the allelopathic species.Hence,the effects of allelopathic plants on community organization through the effects of allelochemicals on soil seed bank remain largely unknown.In this study,we assessed spatial heterogeneities in soil seed bank caused by the presence of allelopathic plants,and evaluated allelo-pathic effects on seed bank germination and seedling mortality.Methods We examined the effects of the allelopathic shrub Artemisia herba-alba Asso on the spatial structure(in terms of species richness and seed density)of the soil seed bank of a semi-arid ecosystem in NE Spain.Specifically,we evaluated seed bank richness and density at three microsites:under the canopy of A.herba-alba individuals,under the canopy of Salsola vermiculata L.(a non-allelopathic shrub)individuals,and in bare soil.In addition,we assessed the effects of aqueous extract of A.herba-alba on soil seed bank germination(seed-ling emergence and emergence timing)and seedling mortality.Important Findings We found that seed bank richness and density were higher under shrub canopy than they were in bare soil.A.herba-alba and S.vermiculata microsites had similar seed bank richness.However,seed bank density was higher under A.herba-alba because of the high abundance of A.herba-alba seeds.Aqueous extract reduced seedling emergence from the seed bank by 50%,and affected mortality of some emerged seedlings.On the other hand,aqueous extract did not influence the emergence timing of seedlings.We conclude that,although the presence of allelo-pathic plants does not cause relevant changes in seed bank struc-ture relative to similar non-allelopathic shrubs,their presence can actually result in a reduction of seedling emergence from the seed bank,which leads to low plant species richness and density nearby.To our knowledge,this is the first study to examine the effect of an allelopathic plant on the structure and germination in an entire soil seed bank.

Effects of small-scale disturbances and elevation on the morphology,phenology and reproduction of a successful geophyte

Aims We aimed to find out how a geophyte,Merendera montana,occupies a wide ecological,elevational and climatic range.This occurrence in that environmental array is outstanding not only among geophytes but also in the whole flora of the Iberian Peninsula,where only a very few plants show such an apparent success.Specifically,we compared morphological and reproductive traits,and frequency of different types of reproduction in disturbed and undisturbed grasslands.Furthermore,we have analyzed the phenology of this plant by trying to understand how it manages to spread in an exceptional elevational gradient of 2000 m,with contrasting climatic regimes between the mediterranean and the alpine regions.Methods We measured the plant density of M.montana populations in different types of Pyrenean grasslands either with or without small-scale disturbances at seven sites from the basal to the alpine belt(400–2300 m a.s.l.).In each one of these populations,100 individuals—1200 in total—were uprooted to measure their morphological features as well as type and occurrence of reproduction.Phenology(flowering and fruiting dates and leaf lifespan)was estimated using 5 years of records in the studied areas and>200 herbarium sheets from the whole altitudinal rank and collected in the last 30 years.Differences in plant densities were analyzed with non-parametric Mann–Whitney U-test;differences in morphological traits,fruit and seed production associated with disturbance,with one-way analysis of covariance test(general linear model).Finally,linear regression analyses were used to determine the relationships between clonal reproduction and elevation and those between flowering,fruiting and senescence and date and elevation.Important Findings In all cases,plant density in disturbed grasslands was significantly higher than in undisturbed grasslands.Plant height and weight,bulb depth,leaf width and bulb and root weight were higher in disturbed plots.Disturbed and undisturbed plots were similar in most aspects of sexual reproduction,including fruiting percentage and seed production,but average seed weight was higher in the disturbed plots.Clonal reproduction and the synchrony of both types of reproduction were significantly higher in disturbed plots.Flowering and leaf emergence dates were not affected by disturbance but at the lowest elevations,they happened at least 2 months later than at the highest elevations.Summarizing,clonal reproduction,advantage in seedling establishment and an unusual but favorable phenology are the main factors in explaining the success of this geophyte colonizing disturbed soils that,in consequence,allow M.montana to settle in a wide range of climatic and ecological conditions.

Patterns of trends in niveograph characteristics across the western United States from snow telemetry data

The snowpack is changing across the globe,as the climate warms and changes.We used daily snow water equivalent(SWE)niveograph(time series of SWE)data from 458 snow telemetry(SNOTEL)stations for the period 1982 through 2012.Nineteen indices based on amount,timing,time length,and rates were used to describe the annual temporal evolution in SWE accumulation and ablation.The trends in these annual indices were computed over the time period for each station using the Theil-Sen slope.These trends were then clustered into four groups to determine the spatial pattern of SWE trends.Temperature and precipitation data were extracted from the PRISM data set,due to the shorter time period of temperature measurement at the SNOTEL stations.Results show that SNOTEL stations can be clustered in four clusters according to the observed trends in snow indices.Cluster 1 stations are mostly located in the Eastern-and South-eastern most parts of the study area and they exhibit a generalized decrease in the indices related with peak SWE and snow accumulation.Those stations recorded a negative trend in precipitation and an increase in temperature.Cluster 4 that is mostly restricted to the North and North-west of the study area shows an almost opposite pattern to cluster 1,due to months with positive trends and a more moderate increase of temperature.Stations grouped in clusters 2 and 3 appear mixed with clusters 1 and 4,in general they show very little trends in the snow indices.

Shifting of summertime weather extremes in Western Europe during 2012-2020

Over the past decades,droughts and heatwaves frequently appeared in Western Europe(45°-65°N,10°W-20°E)during boreal summer,causing huge impacts on human society and ecosystems.Although these extremes are projected to increase in both frequency and intensity under a warming climate,our knowledge of their interdecadal variations and causes is relatively limited.Here we show that the droughts and heatwaves in Western Europe have shifted in their trends in the last decade:for 1979-2012,wind speed and precipitation have both strengthened in Western Europe;for 2012-2020,however,Western Europe have experienced declined wind speed,decreased precipitation,and higher air temperature,leading to more frequent droughts and heatwaves there.Recent changes in the WE climate and extremes are related to the variations of the North Atlantic westerly jet stream.In 1979-2012(2012-2020),the westerly jet stream shifted equatorward(poleward),which enhanced(reduced)transportation of water vapor fluxes from the North Atlantic Ocean to the European land areas,resulting in wetter(drier)surface in Western Europe.Further analysis suggests that phase changes in the Pacific Decadal Oscillation could have played a key role in regulating the position of the jet stream,providing important implications for decadal predictions of the Western Europe summertime climate and weather extremes.

Diversity and host assemblage of avian haemosporidians in different terrestrial ecoregions of Peru

Characterizing the diversity and structure of host–parasite communities is crucial to understandingtheir eco-evolutionary dynamics.Malaria and related haemosporidian parasites are responsible forfitness loss and mortality in bird species worldwide.However,despite exhibiting the greatest ornithologicalbiodiversity,avian haemosporidians from Neotropical regions are quite unexplored.Here,we analyze the genetic diversity of bird haemosporidian parasites(Plasmodium andHaemoproteus)in 1,336 individuals belonging to 206 bird species to explore for differences in diversityof parasite lineages and bird species across 5 well-differentiated Peruvian ecoregions.Wedetected 70 different haemosporidian lineages infecting 74 bird species.We showed that 25 out ofthe 70 haplotypes had not been previously recorded.Moreover,we also identified 81 new host–parasite interactions representing new host records for these haemosporidian parasites.Our outcomesrevealed that the effective diversity(as well as the richness,abundance,and Shannon–Weaver index)for both birds and parasite lineages was higher in Amazon basin ecoregions.Furthermore,we also showed that ecoregions with greater diversity of bird species also had highparasite richness,hence suggesting that host community is crucial in explaining parasite richness.Generalist parasites were found in ecoregions with lower bird diversity,implying that the abundanceand richness of hosts may shape the exploitation strategy followed by haemosporidian parasites.These outcomes reveal that Neotropical region is a major reservoir of unidentified haemosporidianlineages.Further studies analyzing host distribution and specificity of these parasites inthe tropics will provide important knowledge about phylogenetic relationships,phylogeography,and patterns of evolution and distribution of haemosporidian parasites.