Actual evapotranspiration of subalpine meadows in the Qilian Mountains, Northwest China

As a main component in water balance,evapotranspiration(ET)is of great importance for water saving,especially in arid and semi-arid areas.In this study,the FAO(Food and Agriculture Organization)Penman-Monteith model was used to estimate the magnitude and temporal dynamics of reference evapotranspiration(ET0)in 2014 in subalpine meadows of the Qilian Mountains,Northwest China.Meanwhile,actual ET(ETc)was also investigated by the eddy covariance(EC)system.Results indicated that ETc estimated by the EC System was 583 mm,lower than ET0(923 mm)estimated by the FAO Penman-Monteith model in 2014.Moreover,ET0 began to increase in March and reached the peak value in August and then declined in September,however,ETc began to increase from April and reached the peak value in July,and then declined in August.Total ETc and ET0 values during the growing season(from May to September)were 441 and 666 mm,respectively,which accounted for 75.73%of annual cumulative ETc and 72.34%of annual cumulative ET0,respectively.A crop coefficient(kc)was also estimated for calculating the ETc,and average value of kc during the growing season was 0.81(ranging from 0.45 to 1.16).Air temperature(Ta),wind speed(u),net radiation(Rn)and soil temperature(Ts)at the depth of 5 cm and aboveground biomass were critical factors for affecting kc,furthermore,a daily empirical kc equation including these main driving factors was developed.Our result demonstrated that the ETc value estimated by the data of kc and ET0 was validated and consistent with the growing season data in 2015 and 2016.

Characteristics of Caragana korshinskii and Hippophae rhamnoides stemflow and their significance in soil moisture enhancement in Loess Plateau, China

Stemflow of xerophytic shrubs represents a significant component of water replenishment to the soil-root system and influences water utilization of plant roots at the stand scale,especially in water-scarce semi-arid ecosystems.The stemflow of two semi-arid shrubs(Caragana korshinskii and Hippophae rhamnoides)and its effect on soil moisture enhancement were evaluated during the growing season of 2011 in the semi-arid loess region of China.The results indicated that stemflow averaged 12.3%and 8.4%of the bulk precipitation for C.korshinskii and H.rhamnoides,respectively.Individual stemflow increased in a linear function with increasing rainfall depth.The relationship between funneling ratios and rainfall suggested that there existed a rainfall depth threshold of 11 mm for both C.korshinskii and H.rhamnoides.Averaged funneling ratios were 156.6±57.1 and49.5±30.8 for C.korshinskii and H.rhamnoides,respectively,indicating that the canopy architecture of the two shrubs was an effective funnel to channel stemflow to the root area,and C.korshinskii showed a greater potential to use stemflow water in the semi-arid conditions.For individual rainfall events,the wetting front depths were approximately 2 times deeper in the rooting zone around the stems than in the bare area outside canopy for both C.korshinskii and H.rhamnoides.Correspondingly,soil water content was also significantly higher in the root area around the shrub stem than in the area outside the shrub canopy.This confirms that shrub stemflow conserved in the deep soil layers may be an available moisture source for plant growth under semi-arid conditions.

Potato absorption and phytoavailability of Cd, Ni, Cu, Zn and Pb in sierozem soils amended with municipal sludge compost

Effects of sludge utilization on the mobility and phytoavailability of heavy metals in soil-plant systems have attracted broad attention in recent years. In this study, we analyzed the effects of municipal sludge compost （MSC） on the solubility and pIant uptake of Cd, Ni, Cu, Zn and Pb in a soil-potato system to explore the mobility, potato plant uptake and enrichment of these five heavy metals in sierozem soils amended with MSC through a potato cultivation trial in Lanzhou University of China in 2014. Ridge regression analysis was conducted to investigate the phytoavailability of heavy metals in amended soils. Furthermore, CaC12, CH3COONH4, CH3COOH, diethylene triamine pentacetic acid （DTPA） and ethylene diamJne tetraacetic acid （EDTA） were used to extract the labile fraction of heavy metals from the amended soils. The results show that the MSC could not only improve the fertility but also increase the dissolved organic carbon （DOC） content of sierozem soils. The total concentrations and labile fraction proportions of heavy metals increase with increasing MSC percentage in sierozem soils. In amended soils, Cd has the highest solubility and mobility while Ni has the lowest solubility and mobility among the five heavy metals. The MSC increases the concentrations of heavy metals in the root, stem, peel and tuber of the potato plant, with the concentrations being much higher in the stem and root than in the peel and tuber. Among the five heavy metals, the bioconcentration factor value of Cd is the highest, while that of Ni is the lowest. The complexing agent （DTPA and EDTA） extractable fractions of heavy metals are the highest in terms of phytoavailability. Soil properties （including organic matter, pH and DOC） have important impacts on the phytoavailability of heavy metals. Our results suggest that in soil-potato systems, although the MSC may improve soil fertility, it can also increase the risk of soils exposed to heavy metals.

Current patterns of plant diversity and phylogenetic structure on the Kunlun Mountains

Large-scale patterns of biodiversity and the underlying mechanisms that regulate these patterns are central topics in biogeography and macroecology.The Qinghai-Tibet Plateau serves as a natural laboratory for studying these issues.However,most previous studies have focused on the entire Qinghai-Tibet Plateau,leaving independent physical geographic subunits in the region less well understood.We studied the current plant diversity of the Kunlun Mountains,an independent physical geographic subunit located in northwestern China on the northern edge of the Qinghai-Tibet Plateau.We integrated measures of species distribution,geological history,and phylogeography,and analyzed the taxonomic richness,phylogenetic diversity,and community phylogenetic structure of the current plant diversity in the area.The distribution patterns of 1911 seed plants showed that species were distributed mainly in the eastern regions of the Kunlun Mountains.The taxonomic richness,phylogenetic diversity,and genera richness showed that the eastern regions of the Kunlun Mountains should be the priority area of biodiversity conservation,particularly the southeastern regions.The proportion of Chinese endemic species inhabiting the Kunlun Mountains and their floristic similarity may indicate that the current patterns of species diversity were favored via species colonization.The Hengduan Mountains,a biodiversity hotspot,is likely the largest source of species colonization of the Kunlun Mountains after the Quaternary.The net relatedness index indicated that 20 of the 28 communities examined were phylo-genetically dispersed,while the remaining communities were phylogenetically clustered.The nearest taxon index indicated that 27 of the 28 communities were phylogenetically clustered.These results suggest that species colonization and habitat filtering may have contributed to the current plant diversity of the Kunlun Mountains via ecological and evolutionary processes,and habitat filtering may play an important role in this ecological process.

Effects of three coniferous plantation species on plant-soil feedbacks and soil physical and chemical properties in semiarid mountain ecosystems

Background:Large-scale afforestation can significantly change the ground cover and soil physicochemical properties,especially the soil fertility maintenance and water conservation functions of artificial forests,which are very important in semi-arid mountain ecosystems.However,how different tree species affect soil nutrients and soil physicochemical properties after afforestation,and which is the best plantation species for improving soil fertility and water conservation functions remain largely unknown.Methods:This study investigated the soil nutrient contents of three different plantations(Larix principis-rupprechtii,Picea crassifolia,Pinus tabuliformis),soils and plant-soil feedbacks,as well as the interactions between soil physicochemical properties.Results:The results revealed that the leaves and litter layers strongly influenced soil nutrient availability through biogeochemical processes:P.tabuliformis had higher organic carbon,ratio of organic carbon to total nitrogen(C:N)and organic carbon to total phosphorus(C:P)in the leaves and litter layers than L.principis-rupprechtii or P.crassifolia,suggesting that higher C:N and C:P hindered litter decomposition.As a result,the L.principis-rupprechtii and P.crassifolia plantation forests significantly improved soil nutrients and clay components,compared with the P.tabuliformis plantation forest.Furthermore,the L.principis-rupprechtii and P.crassifolia plantation forests significantly improved the soil capacity,soil total porosity,and capillary porosity,decreased soil bulk density,and enhanced water storage capacity,compared with the P.tabuliformis plantation forest.The results of this study showed that,the strong link between plants and soil was tightly coupled to C:N and C:P,and there was a close correlation between soil particle size distribution and soil physicochemical properties.Conclusions:Therefore,our results recommend planting the L.principis-rupprechtii and P.crassifolia as the preferred tree species to enhance the soil fertility and water conservation functions,especially in semi-arid regions mountain forest ecosystems.

Seasonal dynamics of soil water content in the typical vegetation and its response to precipitation in a semi-arid area of Chinese Loess Plateau

Soil water content is a key limiting factor for vegetation growth in the semi-arid area of Chinese Loess Plateau and precipitation is the main source of soil water content in this area.To further understand the impact of vegetation types and environmental factors such as precipitation on soil water content,we continuously monitored the seasonal dynamics in soil water content in four plots(natural grassland,Caragana korshinskii,Armeniaca sibirica and Pinus tabulaeformis)in Chinese Loess Plateau.The results show that the amplitude of soil water content fluctuation decreases with an increase in soil depth,showing obvious seasonal variations.Soil water content of artificial vegetation was found to be significantly lower than that of natural grassland,and most precipitation events have difficulty replenishing soil water content below a depth of 40 cm.Spring and autumn are the key seasons for replenishment of soil water by precipitation.Changes in soil water content are affected by precipitation,vegetation types,soil evaporation and other factors.The interception effect of vegetation on precipitation and the demand for water consumption by transpiration are the key factors affecting the efficiency of soil water replenishment by precipitation in this area.Due to artificial vegetation plantation in this area,soil will face a water deficit crisis in the future.

The adaptive strategies of yaks to live in the Asian highlands

The yak(Bos grunniens),an indigenous herbivore raised at altitudes between 3,000 and 5,000 m above sea level,is closely linked to more than 40 ethnic communities and plays a vital role in the ecological stability,livelihood security,socio-economic development,and ethnic cultural traditions in the Asian highlands.They provide the highlanders with meat,milk,fibres,leather and dung(fuel).They are also used as pack animals to transport goods,for travel and ploughing,and are important in many religious and traditional ceremonies.The Asian highlands are known for an extremely,harsh environment,namely low air temperature and oxygen content and high ultraviolet light and winds.Pasture availability fluctuates greatly,with sparse pasture of poor quality over the long seven-month cold winter.After longterm natural and artificial selections,yaks have adapted excellently to the harsh conditions:1)by genomics,with positively selected genes involved in hypoxia response and energy metabolism;2)anatomically,including a short tongue with a weak sense of taste,and large lung and heart;3)physiologically,by insensitivity to hypoxic pulmonary vasoconstriction,maintaining foetal haemoglobin throughout life,and low heart rate and heat production in the cold season;4)behaviourlly,by efficient grazing and selecting forbs with high nutritional contents;5)by low nitrogen and energy requirements for maintenance and low methane emission and nitrogen excretion,namely,‘Low-Carbon’and‘Nitrogen-Saving’traits;6)by harboring unique rumen microbiota with a distinct maturation pattern,that has coevolved with host metabolism.This review aims to provide an overview of the comprehensive adaptive strategies of the yak to the severe conditions of the highlands.A better understanding of these strategies that yaks employ to adapt to the harsh environment could be used in improving their production,breeding and management,and gaining benefits in ecosystem service and a more resilient livelihood to climate change in the Asian highlands.

Variation of nectar production in relation to plant characteristics in protandrous Aconitum gymnandrum

Aims Floral nectar plays a vital role in plant reproductive success by attracting pollinators.Nectar traits of a flower can depend directly on plant characteristics other than environmental factors and exhibit extensive flower-and plant-level variations.studies on nectar traits frequently focused on intraplant variation for dichogamous plants,but few have paid attention to both intra-and interplant nectar variations in relation to plant characteristics.revealing within-and among-plant variation and its relative magnitude is important for our understanding of how pollinator-mediated selection can act on nectar traits and evolution of nectar traits.Methods Through investigating protandrous Aconitum gymnandrum populations at the alpine meadows and Wetland Ecosystems research station of lanzhou university,we examined the relationships between nectar production per flower and plant characteristics(e.g.flower position within inflorescences,flo-ral sexual phases,flowering time,inflorescence size and floral attractive traits).Important Findings A.gymnandrum exhibited a declining gradient in the nectar volume along inflorescences,with more nectar in basal flowers than distal ones.Protandrous flowers of A.gymnandrum did not show gender-biased nectar production while the nectar volume varied with differ-ent stages of floral sexual phases.The significant correlation between the first flowering date of individuals and the mean nectar volume per flower was positive in 2013,but became negative in 2014,sug-gesting complex effects of biotic and abiotic factors.The mean nectar volume per flower was not related to inflorescence size(the num-ber of total flowers per plant).Furthermore,nectar production was weakly associated with floral attractive traits(the petal width and the galea height),even if the effect of flowering time of individuals was removed,suggesting that the honesty of floral traits as signals of nec-tar reward for pollinators is not stable in this species.

Plasticity of floral sex allocation within inflorescences of hermaphrodite Aconitum gymnandrum

Aims sex allocation in plants is often plastic,enabling individuals to adjust to variable environments.However,the predicted male-biased sex allocation in response to low resource conditions has rarely been experimentally tested in hermaphroditic plants.in particular,it is unknown whether distal flowers in linear inflorescences show a larger shift to male allocation relative to basal flowers when resources are reduced.in this study,we measure position-depend-ent plasticity of floral sex allocation within racemes of Aconitum gymnandrum in response to reduced resource availability.Methods using a defoliation treatment in the field applied to potted plants from a nested half-sibling design,we examined the effects of the treatment,flower position,family and their interactions.Important Findingsallocation to male function increased with more distal flower posi-tion,while female allocation either did not change with position or declined at the most distal flowers.Defoliation significantly reduced the mass of both the androecium and gynoecium,but not anther number or carpel number.gynoecial mass declined more strongly with defoliation than did androecial mass,resulting in a significant increase in the androecium/gynoecium ratio as predicted by sex allocation theory.Plastic responses of androecium mass and gynoecium mass were affected by flower position,with less mass lost in basal flowers,but similar plastic magnitude in both sexual traits across flower position lead to consistent variation in the androecium/gynoecium ratio along the inflorescence.a sig-nificant treatment*paternal family interaction for the androecium/gynoecium ratio is evidence for additive genetic variation for plastic floral sex allocation,which means that further evolution of alloca-tion can occur.

Applications of beneficial plant growth promoting rhizobacteria and mycorrhizae in rhizosphere and plant growth:A review

Because of climate change and the highly growing world population,it becomes a huge challenge to feed the whole population.To overcome this challenge and increase the crop yield,a large number of fertilizers are applied but these have many side effects.Instead of these,scientists have discovered beneficial rhizobacteria,which are environmentally friendly and may increase crop yield and plant growth.The microbial population of the rhizosphere shows a pivotal role in plant development by inducing its physiology.Plant depends upon the valuable interactions among the roots and microbes for the growth,nutrients availability,growth promotion,disease suppression and other important roles for plants.Recently numerous secrets of microbes in the rhizosphere have been revealed due to huge development in molecular and microscopic technologies.This review illustrated and discussed the current knowledge on the development,maintenance,interactions of rhizobacterial populations and various proposed mechanisms normally used by PGPR in the rhizosphere that encouraging the plant growth and alleviating the stress conditions.In addition,this research reviewed the role of single and combination of PGPR,mycorrhizal fungi in plant development and modulation of the stress as well as factors affecting the microbiome in the rhizosphere.

Convergence of community composition during secondary succession on Zokor rodent mounds on the Tibetan Plateau

Aims The community succession theory is much debated in ecology.We studied succession on Zokor rodent mounds on the Tibetan Plateau to address several fundamental questions,among them:(i)During secondary succession,does the community composition converge towards one community state or multiple states depending on the initial colonization?(ii)Do mound communities located in different background communities exhibit different assembly trajectories?Methods In a sub-alpine meadow,we investigated a total of 80 mound com-munities at several successional stages in three different background communities resulting from different management histories and compared their changes in species composition.The distribution of plant communities over time was analyzed with quantitative clas-sification and ordination methods.The co-occurrence patterns of species were evaluated at each successional stage,and the degree of convergence/divergence among communities was obtained by calculating two beta-diversity indices.Important Findings During secondary succession,species richness of mound com-munities changed over time,and this change was dependent on the background community.Five life-form groups exhibited different dynamic patterns in species richness and plant cover.Community composition and the degree of species co-occur-rence between communities increased over time since disturb-ance.There was much variation in species composition at earlier stages of succession,but communities on older mounds became more similar to each other and to their surrounding vegetation over the course of secondary succession.Post-disturbance suc-cession of Zokor mound communities transitioned from‘multiple alternative states’to‘background-based deterministic commu-nity assembly’over time.Tradeoffs between competition and colonization,as well as the characteristics of different life-forms and mass effects within a limited species pool are the mecha-nisms responsible for convergence of mound communities.

Increased community compositional dissimilarity alleviates species loss following nutrient enrichment at large spatial scales

Aims Anthropogenic activities have drastically increased nutrient availabil-ity,resulting in declines in species richness in many plant communi-ties.However,most previous studies have explored only species-loss patterns and mechanisms over small sampling areas,so their results might overestimate species loss at larger spatial scales.The aim of this research was to explore species diversity change patterns and species-loss rates at multiple scales in alpine meadow communities following nutrient enrichment.Specifically,we asked two closely related ques-tions:(i)do changes in species diversity and species-loss patterns differ among spatial scales?and(ii)how does community compositional dissimilarity and species turnover change among spatial scale?Methods This study was implemented in an alpine meadow community,which is regarded as one of the most sensitive and vulnerable ter-restrial ecosystems to anthropogenic nutrient enrichment.We conducted a fertilization experiment that involved the addition of nitrogen(N),phosphorus(P)and a mixture of both to a series of quadrats ranging from 1 to 16 m2 over 5 years to study the variations in the patterns of species diversity in response to nutrient additions at different spatial scales.Important Findings Our results showed that the changes in species diversity and species loss were dependent on the type of fertilization and the spatial scale.After N and NP fertilization,species diversity significantly decreased at the small scale but not at the large scale,and the rate of species loss decreased as the spatial scale increased.In contrast,the differences between the P addition and control communities were negligible at both the small and large spatial scales.N fertilization caused species to be lost from the small sampling scale,but because different species were lost from dif-ferent samples,there was an increase in compositional dissimilarity at larger spatial scales,which reduced the total number of species lost when measured at larger scales.These findings highlight spatial scale in evalu-ating the biodiversity loss after fertilization and suggest that the compo-sitional dissimilarity might play an important role in mediating species loss after fertilization.Our study significantly improved our understanding of changes in species diversity and species loss at different spatial scales under nutrient-enrichment scenarios.

The effects of fertilization on the trait-abundance relationships in a Tibetan alpine meadow community

Aims Comparisons of the trait-abundance relationships from various habitat types are critical for community ecology,which can offer us insights about the mechanisms underlying the local community assembly,such as the relative role of neutral vs.niche processes in shaping community structure.Here,we explored the responses of trait-abundance relationships to nitrogen(N),phosphorus(P)and potassium(K)fertilization in an alpine meadow.Methods Five fertilization treatments(an unfertilized control and additions of N,P,K and NPK respectively)were implemented using randomized block design in an alpine Tibetan meadow.Species relative abundance(SRA),plant above-ground biomass and species richness were measured in each plot.For 24 common species,we measured species functional traits:saturated height,specific leaf area(SLA)and leaf dry matter content(LDMC)in each treatment but seed size only in the unfertilized control.Standard major axis(SMA)regression and phylogenetically independent contrasts(PICs)analysis were used to analyse species trait-abundance relationships in response to different fertilization treatments.Important Findings Positive correlations between SRA and saturated height were raised following N,P and NPK fertilizations,which indicated an increase in light competition in these plots.In P fertilized plots,SRA was also positively correlated with LDMC because tall grasses with a nutrients conservation strategy often have a relative competitive advantage in capturing limited light and soil nutrients.In K fertilized plots,neither the trait-abundance relationships nor above-ground biomass or species richness significantly differed from that in the control,which suggests that K was not a limiting resource in our study site.These significant correlations between species traits and relative abundance in fertilized treatment suggest that trait-based selection plays an important role in determining species abundance within local communities in alpine meadows.

Ecogeographical variation of 12 morphological traits within Pinus tabulaeformis: the effects of environmental factors and demographic histories

Aims More data are needed about how genetic variation(GV)and envi-ronmental factors influence phenotypic variation within the natural populations of long-lived species with broad geographic distribu-tions.To fill this gap,we examined the correlations among envi-ronmental factors and phenotypic variation within and among 13 natural populations of Pinus tabulaeformis consisting of four demo-graphically distinct groups within the entire distributional range.Methods Using the Akaike’s information Criterion(AiC)model,we measured 12 morphological traits and constructed alternative candidate models for the relationships between each morphological trait and key climatic variables and genetic groups.We then compared the AiC weight for each candidate model to identify the best approximating model for ecogeographical variation of P.tabulaeformis.The partitioning of vari-ance was assessed subsequently by evaluating the independent vari-ables of the selected best models using partial redundancy analysis.Important Findings Significant phenotypic variation of the morphological traits was observed both within individual populations and among populations.Variation partition analyses showed that most of the phenotypic variation was co-determined by both GV and climatic factors.GV accounted for the largest proportion of reproductive trait variation,whereas local key climatic factors(i.e.actual evapotranspiration,AET)accounted for the largest proportion of phenotypic variation in the remaining investigated traits.Our results indicate that both genetic divergence and key environmental factors affect the phenotypic variation observed among populations of this species,and that reproductive and vegetative traits adaptively respond differently with respect to local environmental conditions.This partitioning of factors can inform those making predictions about phenotypic variation in response to future changes in climatic conditions(particularly those affecting AET).

放牧对青藏高原高寒草地种子萌发性状选择的影响

以前的研究表明放牧能够引起草地生物与非生物环境的显著变化,但这种变化影响草地群落对种子萌发特征的选择机制尚不清楚。因此,我们旨在回答:放牧是否对草地群落中萌发特征的组成和多样性产生显著影响。我们在实验室检测了研究草地群落内主要物种种子的萌发特性,并比较了这些植物在放牧和非放牧草地上的表现。在此基础上,比较了放牧草地和非放牧草地的各萌发性状的群落加权平均值和萌发性状多样性,从而了解放牧草地和非放牧草地是否存在不同的萌发性状结构。研究结果表明,在物种水平上,放牧和非放牧草地各物种的多度变化与物种的萌发性状无显著关系。但在群落水平上,与非放牧草地相比,放牧草地的物种普遍具有较高的种子萌发率;放牧草地种子萌发对变温的正响应显著大于非放牧草地,而且放牧草地种子萌发温度生态位宽度小于非放牧草地。与非放牧草地相比,放牧草地种子萌发性状多样性增加,萌发性状均匀度降低。放牧可以改变微生境,从而通过环境过滤改变草地群落对萌发性状的选择,导致草地群落的萌发性状于放牧前后在群落水平上存 在显著差异。