Spatiotemporal changes of gross primary productivity and its response to drought in the Mongolian Plateau under climate change

Gross primary productivity(GPP)of vegetation is an important constituent of the terrestrial carbon sinks and is significantly influenced by drought.Understanding the impact of droughts on different types of vegetation GPP provides insight into the spatiotemporal variation of terrestrial carbon sinks,aiding efforts to mitigate the detrimental effects of climate change.In this study,we utilized the precipitation and temperature data from the Climatic Research Unit,the standardized precipitation evapotranspiration index(SPEI),the standardized precipitation index(SPI),and the simulated vegetation GPP using the eddy covariance-light use efficiency(EC-LUE)model to analyze the spatiotemporal change of GPP and its response to different drought indices in the Mongolian Plateau during 1982-2018.The main findings indicated that vegetation GPP decreased in 50.53% of the plateau,mainly in its northern and northeastern parts,while it increased in the remaining 49.47%area.Specifically,meadow steppe(78.92%)and deciduous forest(79.46%)witnessed a significant decrease in vegetation GPP,while alpine steppe(75.08%),cropland(76.27%),and sandy vegetation(87.88%)recovered well.Warming aridification areas accounted for 71.39% of the affected areas,while 28.53% of the areas underwent severe aridification,mainly located in the south and central regions.Notably,the warming aridification areas of desert steppe(92.68%)and sandy vegetation(90.24%)were significant.Climate warming was found to amplify the sensitivity of coniferous forest,deciduous forest,meadow steppe,and alpine steppe GPP to drought.Additionally,the drought sensitivity of vegetation GPP in the Mongolian Plateau gradually decreased as altitude increased.The cumulative effect of drought on vegetation GPP persisted for 3.00-8.00 months.The findings of this study will improve the understanding of how drought influences vegetation in arid and semi-arid areas.

Spatiotemporal patterns and drivers of cultivated land conversion in Inner Mongolia Autonomous Region,northern China

Protection and optimization of cultivated land resources are of great significance to national food security.Cultivated land conversion in northern China has increased in recent years due to the industrialization and urbanization of society.However,the assessment of cultivated land conversion in this area is insufficient,posing a potential risk to cultivated land resources.This study evaluated the evolution and spatiotemporal patterns of cultivated land conversion in Inner Mongolia Autonomous Region,China,and the driving factors to improve rational utilization and to protect cultivated land resources.The spatiotemporal patterns of cultivated land conversion in Inner Mongolia were analyzed using the cultivated land conversion index,kernel density analysis,a standard deviation ellipse model,and a geographic detector.Results showed that from 2000 to 2020,the trends in cultivated land conversion area and rate in Inner Mongolia exhibited fluctuating growth,with the total area of cultivated land conversion reaching 7307.59 km^(2) at a rate of 6.69%.Spatial distribution of cultivated land conversion was primarily concentrated in the Hetao Plain,Nengjiang Plain,Liaohe Plain,and the Hohhot-Baotou-Ordos urban agglomeration.Moreover,the standard deviational ellipse of cultivated land conversion in Inner Mongolia exhibited a directional southwest-northeast-southwest-northeast distribution,with the northeast-southwest direction identified as the main driving force of spatial change in cultivated land conversion.Meanwhile,cultivated land conversion exhibited an increase-decrease-increase change process,indicating that spatial distribution of cultivated land conversion in Inner Mongolia became gradually apparent within the study period.The geographic detector results further revealed that the main driving factors of cultivated land conversion in Inner Mongolia were the share of secondary and tertiary industries and per-unit area yield of grain,with explanatory rates of 57.00%,55.00%,and 51.00%,respectively.Additionally,improved agricultural production efficiency and the coordinated development of population urbanization and industry resulted in cultivated land conversion.Collectively,the findings of this study indicated that,from 2000 to 2020,the cultivated land conversion in Inner Mongolia was significant and fluctuated in time,and had strong spatial heterogeneity.The primary drivers of these events included the effects of agriculture,population,and social economy.

Response of ecosystem carbon storage to land use change from 1985 to 2050 in the Ningxia Section of Yellow River Basin,China

Regional sustainable development necessitates a holistic understanding of spatiotemporal variations in ecosystem carbon storage(ECS),particularly in ecologically sensitive areas with arid and semi-arid climate.In this study,we calculated the ECS in the Ningxia Section of Yellow River Basin,China from 1985 to 2020 using the Integrated Valuation of Ecosystem Services and Tradeoffs(InVEST)model based on land use data.We further predicted the spatial distribution of ECS in 2050 under four land use scenarios:natural development scenario(NDS),ecological protection scenario(EPS),cultivated land protection scenario(CPS),and urban development scenario(UDS)using the patch-generating land use simulation(PLUS)model,and quantified the influences of natural and human factors on the spatial differentiation of ECS using the geographical detector(Geodetector).Results showed that the total ECS of the study area initially increased from 1985 until reaching a peak at 402.36×10^(6) t in 2010,followed by a decreasing trend to 2050.The spatial distribution of ECS was characterized by high values in the eastern and southern parts of the study area,and low values in the western and northern parts.Between 1985 and 2020,land use changes occurred mainly through the expansion of cultivated land,woodland,and construction land at the expense of unused land.The total ECS in 2050 under different land use scenarios(ranked as EPS>CPS>NDS>UDS)would be lower than that in 2020.Nighttime light was the largest contributor to the spatial differentiation of ECS,with soil type and annual mean temperature being the major natural driving factors.Findings of this study could provide guidance on the ecological construction and high-quality development in arid and semi-arid areas.

Effect of salinization on soil properties and mechanisms beneficial to microorganisms in salinized soil remediation-a review

Salinized soil is an important reserved arable land resource in China.The management and utilization of salinized soil can safeguard the current size of arable land and a stable grain yield.Salt accumulation will lead to the deterioration of soil properties,destroy soil production potential and damage soil ecological functions,which in turn will threaten global water and soil resources and food security,and affect sustainable socio-economic development.Microorganisms are important components of salinized soil.Microbial remediation is an important research tool in improving salinized soil and is key to realizing sustainable development of agriculture and the ecosystem.Knowledge about the impact of salinization on soil properties and measures using microorganisms in remediation of salinized soil has grown over time.However,the mechanisms governing these impacts and the ecological principles for microbial remediation are scarce.Thus,it is imperative to summarize the effects of salinization on soil physical,chemical,and microbial properties,and then review the related mechanisms of halophilic and halotolerant microorganisms in salinized soil remediation via direct and indirect pathways.The stability,persistence,and safety of the microbial remediation effect is also highlighted in this review to further promote the application of microbial remediation in salinized soil.The objective of this review is to provide reference and theoretical support for the improvement and utilization of salinized soil.

Modern pollen assemblages and their relationships with vegetation and climate on the northern slopes of the Tianshan Mountains, Xinjiang, China

The reconstruction of paleovegetation and paleoclimate requires an understanding of the relationships between surface pollen assemblages and modern vegetation and climate.Here,we analyzed the characteristics of surface pollen assemblages across different vegetation zones in the Tianshan Mountains.Using surface pollen analysis and vegetation sample surveys at 75 sites on the northern slopes of the Tianshan Mountains,we determined the correlation between the percentage of dominant pollen types and the corresponding vegetation cover.Redundancy analysis was used to investigate the relationships between surface pollen assemblages and environmental factors.Our results show that the Tianshan Mountains contain several distinct ecological regions,which can be divided into five main vegetation zones from low to high altitudes:mountain desert zone(Hutubi County(HTB):500-1300 m;Qitai County(QT):1000-1600 m),mountain steppe zone(HTB:1400-1600 m;QT:1650-1800 m),mountain forest zone(HTB:1650-2525 m;QT:1850-2450 m),subalpine meadow zone(HTB:2550-2600 m;QT:2500-2600 m),and alpine mat vegetation zone(HTB:2625-2700 m;QT:2625-2750 m).The surface pollen assemblages of different vegetation zones can accurately reflect the characteristics of the mountainous vegetation patterns on the northern slopes of the Tianshan Mountains when excluding the widespread occurrence of Chenopodiaceae,Artemisia,and Picea pollen.Both average annual precipitation(P_(ann))and annual average temperature(T_(ann))affect the distribution of surface pollen assemblages.Moreover,P_(ann) is the primary environmental factor affecting surface pollen assemblages in this region.A significant correlation exists between the pollen percentage and vegetation cover of Picea,Chenopodiaceae,Artemisia,and Asteraceae.Moreover,Picea,Chenopodiaceae,and Artemisia pollen are over-represented compared with their corresponding vegetation cover.The Asteraceae pollen percentage roughly reflects the distribution of a species within the local vegetation.These results have important implications for enhancing our understanding of the relationship between surface pollen assemblages and modern vegetation and climate.

Geochronological and geochemical constraints on the granitic gneiss in the Huozhou Complex: implications for the tectonic evolution of the Trans-North China Orogen

The Trans-North China Orogen is a major Neoarchean Paleoproterozoic collisional orogenic belt above the North China Craton, formed due to prolonged and complex processes. Even though many NeoarcheanPaleoproterozoic magmatic and metamorphic activities have been reported, due to the Huozhou Complex’s small outcropping range, little attention has been paid to the origin of various igneous rocks of the Huozhou Complex in the center of the Trans-North China Orogen. The Huozhou Complex, located south of the Luè liang, Wutai, and Hengshan complexes, is an important window into the Early Precambrian structure and evolution of the North China Craton. Its magma and metamorphism are crucial to understanding the development of the structural evolution of the Trans-North China Orogen. The Huozhou metamorphic complex area exposes a range of Precambrian metamorphic rocks, among which the most extensively dispersed is felsic biotite plagioclase gneiss. In this study comprehensive geological field survey, micropetrology,chronology, geochemistry, and Hf isotope analysis were carried out for the Qinggangping and Anziping gneiss in the north of the Huozhou Complex. The results show that the magmatic zircon age of the Qinggangping gneiss is2196 ± 14 Ma, and its protolith is I-type granite, formed by partial melting of igneous rocks in the absence of weathering. Its source is mainly the juvenile crust from depleted mantle dating 2431–2719 Ma, with a small amount of mantle-derived material. The Anziping gneiss has a metamorphic zircon age of 1931 ± 13 Ma with an S-type granite protolith belonging to peraluminous granite.The Anziping gneiss is formed by recycling pre-existing crustal components at 2613–2848 Ma. A minor quantity of mantle-derived magma is also introduced to the crust simultaneously. The samples of Qinggangping gneiss and Anziping gneiss show the characteristics of obvious negative Nb, Ti, and P elements in the spider diagram of primitive mantle standardization. This implies that the rocks have the characteristics of magmatic rocks in an island arc or subduction environment, which could have formed in the tectonic environment of the continental margin arc.

2.7-Ga-old mafic dike in the Trans-North China Orogen of the North China Craton and its tectonic significance

We studied an Archean mafic dike in the TransNorth China Orogen of the North China Craton, which has a magmatic age of 2701 ± 83 Ma and is currently the oldest mafic dike in the North China Craton. Such an old dike is extremely rare in the world. The presence of mafic dikes indicates that the North China Craton was in a tensional tectonic environment at 2.7 Ga. Geochemical characteristics reveal that this mafic dike belongs to continental tholeiitic basalt. Results from Hf isotope analysis reveal that the mafic dike originates from a depleted mantle. The plate assembly in the North China landmass was realized during the Archean era(2.7 Ga), and a thick and stable continental crust was formed. Therefore, the first cratonization of the North China Craton was completed before 2.7 Ga. The intrusion of the 2.7-Ga-old mafic dike from the deep lithospheric mantle of the continent indicates that the North China Craton has undergone a period of extensional tectonic activity. This event marks a significant extensional event that occurred after the cratonization of the North China Craton.

Diversity of soil bacteria and fungi communities in artificial forests of the sandy-hilly region of Northwest China

Soil erosion is a serious issue in the sandy-hilly region of Shanxi Province,Northwest China.There has been gradual improvement due to vegetation restoration,but soil microbial community characteristics in different vegetation plantation types have not been widely investigated.To address this,we analyzed soil bacterial and fungal community structures,diversity,and microbial and soil environmental factors in Caragana korshinskii Kom.,Populus tomentosa Carr.,Populus simonii Carr.,Salix matsudana Koidz,and Pinus tabulaeformis Carr.forests.There were no significant differences in the dominant bacterial community compositions among the five forest types.The alpha diversity of the bacteria and fungi communities showed that ACE(abundance-based coverage estimator),Chao1,and Shannon indices in C.korshinskii forest were significantly higher than those in the other four forest types(P<0.05).Soil organic matter,total nitrogen,and urease had a greater impact on bacterial community composition,while total nitrogen,β-glucosidase,and urease had a greater impact on fungal community composition.The relative abundance of beneficial and pathogenic microorganisms was similar across all forest types.Based on microbial community composition,diversity,and soil fertility,we ranked the plantations from most to least suitable as follows:C.korshinskii,S.matsudana,P.tabulaeformis,P.tomentosa,and P.simonii.

Abrupt change of winter temperature over the Mongolian Plateau during 1961-2017

Studying the abrupt change of winter temperature(ACWT)over the Mongolian Plateau(MP,including Inner Mongolia Autonomous Region and State of Mongolia)is of great significance for understanding the spatiotemporal distribution of temperature and the mechanism of global climate change.Monthly temperature data during 1961–2017was collected,and the abrupt change point was determined by the Mann–Kendall test and sliding ttest,to analyze the characteristics and causes of ACWT.The results showed that(a)The winter temperature has rapidly increased with a trend of 0.41℃/10a,which was significantly higher than that of the rest area of Chinese mainland,indicating that climate change in the MP was more sensitive to global warming.(b)The abrupt change point occurred in 1988,with temperature of-15.5℃and-14.1℃before and after abrupt change,respectively.The ACWT in 50°N was 1–3 years later than that in 40°N,and the isotherms of different temperatures moved northward by 10–200 km,especially-16℃isotherms moved approximately 200 km northward after 1988.(c)The Arctic Oscillation(AO)and Mongolian High(MH)anomaly affects winter temperature over the MP.When the AO is unusually strong,the MH and East Asian winter monsoon are weak,and southerly winds prevail in most regions,which is not conducive to the cold air developing southward,leading to higher winter temperature in the MP.Overwise,abnormally northerly winds prevail and temperature is low.Meanwhile,the abrupt change time of AO occurred in 1987 before winter temperature.It shows that the AO indirectly causes winter temperatures to rise by influencing the MH and is also the main driving factor of ACWT.

Bibliometrics-based Research Hotspots and Development Trends in Eco-hydrology of Dammed Rivers

Water conservation initiatives satisfy the demand for water supply,electricity generation,irrigation,and flood control.While helping humanity,they have also altered the ecosystem of natural rivers,impacted river ecology,disrupted river continuity,and jeopardized the existence of aquatic creatures in rivers.Studying the impacts of dam construction on rivers can enhance our knowledge of river ecological and environmental concerns and help sustain the health of river ecosystems,thereby realizing the harmony between humans and water in both theoretical and practical aspects.This study used bibliometrics and constructed an author-keyword 2-mode matrix network using Co-Occurrence software to identify the hotspots and research trend in eco-hydrology of dammed rivers.We identified‘FLOW’‘SEDIMENT’‘QUALITY’and‘MODEL’as the research hotspots in the ecological impact of dammed rivers,and combined the related literatures,we highlight the research progress in the four directions.Then the research shortcomings and prospect were discussed,including strengthening the monitoring and analysis of critical ecological variables,enhancing the hydrological monitoring density for small rivers,strengthening the research of relationship between eutrophication and zooplankton,establishing multiscale approaches,and combining multi-sources information technologies to improve parameter accuracy in the model research.

Spatial and Temporal Evolution Characteristics of Extreme Precipitation and Isohyets in Ningxia

The multi-scale spatial and temporal evolution characteristics of extreme precipitation and isohyets in Ningxia were studied using daily,monthly,and annual precipitation data from 20 meteorological stations in Ningxia over the last 60 years.The results revealed that the intensity of rainstorms in Ningxia had decreased slightly over the previous 60 years,with the intensity of rainstorms in southern and central Ningxia being higher than in northern areas.Ningxia's annual and seasonal precipitation varied regionally,declining from the southeast to the northwest.Annual,spring and autumn precipitation exhibited a significantly declining trend from 1960 to the early 21^(st)century;summer precipitation displayed a slightly decreasing trend;and winter precipitation showed a significantly increasing trend.Nevertheless,there was a noticeable increase in annual and seasonal precipitation after 2005.From the 1960s to the 2000s,the 200 mm isohyet moved slowly southward,while the 400 mm isohyet jumped southward twice in the 1970s and 2000s before jumping considerably northward in the 2010s to reach their northernmost region.

Hyperspectral Inversion and Analysis of Zinc Concentration in Urban Soil in the Urumqi City of China

Excessive accumulation of zinc(Zn)in urban soil can lead to environmental pollution and pose a potential threat to human health and the ecosystem.How to quickly and accurately monitor the urban soil zinc content on a large scale in real time and dynamically is crucial.Hyperspectral remote sensing technology provides a new method for rapid and nondestructive soil property detection.The main goal of this study is to find an optimal combination of spectral transformation and a hyperspectral estimation model to predict the Zn content in urban soil.A total of 88 soil samples were collected to obtain the Zn contents and related hyperspectral data,and perform 18 transformations on the original spectral data.Then,select important wavelengths by Pearson’s correlation coefficient analysis(PCC)and CARS.Finally,establish a partial least squares regression model(PLSR)and random forest regression model(RFR)with soil Zn content and important wavelengths.The results indicated that the average Zn content of the collected soil samples is 60.88 mg/kg.Pearson’s correlation coefficient analysis(PCC)and CARS for the original and transformed wavelengths can effectively improve the correlations between the spectral data and soil Zn content.The number of important wavelengths selected by CARS is less than the important wavelengths selected by PCC.Partial least squares regression model based on first-order differentiation of the reciprocal by CARS(CARS-RTFD-PLSR)is more stable 2 and has the highest prediction ability(R=0.937,RMSE=8.914,MAE=2.735,RPD=3.985).The CARS-RTFD-PLSR method can be used as a means of prediction of Zn content in soil in oasis cities.The results of the study can provide technical support for the hyperspectral estimation of the soil Zn content.

Simulation of urban expansion using geographical similarity transition rules and neighbourhood sizes

Most existing cellular automata(CA)models impose strict requirements on the number and spatial distribution of samples.This makes it a challenge to capture spatial heterogeneity in urban dynamics and meet the modeling needs of large and complex geographic areas.This paper presents a CA model based on geographically optimal similarity(GOS)transition rules and similarly sized neighborhoods(SSN).By comparing the similarity in geographical configuration between samples and predicted points,the model enables a comprehensive characterization of the driving mechanism behind urban expansion and its self-organizing scope.This helps to mitigate the impact of sample selection and assumptions about spatial stationarity on simulation results.The performance of GOS-SSN-CA simulation was tested by taking the urban expansion in the Changsha-Zhuzhou-Xiangtan urban agglomeration in China as an example.The results show that GOS can derive more accurate and reliable urban transition rules with fewer samples,thereby significantly reducing spatial prediction errors compared with logistic regression.Moreover,SSN selects different neighborhood sizes to represent the difference between the local self-organizing range and surrounding cells,thus further improving the simulation accuracy and restricting urban expansion morphology.Overall,GOS-SSN-CA effectively characterizes the geographical similarity of urban expansion,improves simulation accuracy while constraining the urban expansion form,and enhances the practical application value of CA.

Cloud Top Pressure Retrieval Using Polarized and Oxygen A-band Measurements from GF5 and PARASOL Satellites

Cloud top pressure(CTP)is one of the critical cloud properties that significantly affects the radiative effect of clouds.Multi-angle polarized sensors can employ polarized bands(490 nm)or O_(2)A-bands(763 and 765 nm)to retrieve the CTP.However,the CTP retrieved by the two methods shows inconsistent results in certain cases,and large uncertainties in low and thin cloud retrievals,which may lead to challenges in subsequent applications.This study proposes a synergistic algorithm that considers both O_(2)A-bands and polarized bands using a random forest(RF)model.LiDAR CTP data are used as the true values and the polarized and non-polarized measurements are concatenated to train the RF model to determine CTP.Additionally,through analysis,we proposed that the polarized signal becomes saturated as the cloud optical thickness(COT)increases,necessitating a particular treatment for cases where COT<10 to improve the algorithm's stability.The synergistic method was then applied to the directional polarized camera(DPC)and Polarized and Directionality of the Earth’s Reflectance(POLDER)measurements for evaluation,and the resulting retrieval accuracy of the POLDER-based measurements(RMSEPOLDER=205.176 hPa,RMSEDPC=171.141 hPa,R^(2)POLDER=0.636,R^(2)DPC=0.663,respectively)were higher than that of the MODIS and POLDER Rayleigh pressure measurements.The synergistic algorithm also showed good performance with the application of DPC data.This algorithm is expected to provide data support for atmosphere-related fields as an atmospheric remote sensing algorithm within the Cloud Application for Remote Sensing,Atmospheric Radiation,and Updating Energy(CARE)platform.

Different people,different wild:Comparing and mapping wilderness representation in Wuyishan National Park,China

It is essential to better integrate wilderness representations of different stakeholders into wilderness conservation.The way in which local residents and other stakeholders frame the construction of wilderness of protected areas in developing countries are poorly understood.In these areas,land use policy and decision may lead to conflicts.This study aims to explore existing public wilderness representations using a questionnaire survey(n=514)administered amongst tourists and other stakeholders in the Wuyishan National Park,in southeast China.The spatial differences in public representations of wilderness across different stakeholder groups were compared against expert knowledge.We found that integrated wilderness representation maps of different stakeholder groups were consistent,namely'area where wild animals live','area with no human influence','a barren and lonely area'.However,three sub-representations of the individual stakeholders varied significantly.Moreover,expert-based wilderness mapping did not reflect public representations accurately,and an integrated wilder-ness quality map considering wilderness representations across both stakeholders and experts can better identify detailed wilderness areas.Our study provides new insights and technical support for future exploration of wilder-ness conservation and mapping in China and other countries with insufficient awareness of wilderness values and investigations in a regional scale.

Changes of Soil Labile Organic Carbon in Different Land Uses in Sanjiang Plain, Heilongjiang Province

In the Sanjiang Plain,Northeast China,the natural wetland is undergoing a rapid conversion into agricultural land,which has resulted in drastic ecological changes in the region. To investigate the effects of different land uses on soil labile organic carbon,soils of Calamagrostis angustifolia wetland,Carex lasiocarpa wetland,dry farmland,paddy field,forest land and abandoned cultivated land were collected for measuring the contents of soil microbial biomass carbon (MBC),dissolved organic carbon (DOC),readily oxidizable carbon (ROC) and carbohydrate carbon (CHC). The results show that soil organic carbon contents follow the order: Carex lasiocarpa wetland>Calamagrostis angustifolia wetland>forest land>paddy field>dry farmland. The contents of MBC and DOC in Calamagrostis angustifolia and Carex lasiocarpa wetlands are significantly higher than those in other land use types. The contents of CHC and ROC are the highest in Calamagrostis angustifolia wetland and the lowest in dry farmland. The contents of all the labile organic carbon increase along with the years of abandonment of cultivated land. The ratios of MBC,DOC and ROC to SOC also follow the order: Carex lasiocarpa wetland>Calamagrostis angustifolia wetland>forest land>paddy field>dry farmland,while the ratio of CHC to SOC is paddy field>forest field>Carex lasiocarpa wetland>Carex lasiocarpa wetland>dry farmland. When natural wetlands were cultivated,the activity of soil organic carbon tends to reduce in some extent due to the disappearance of heterotrophic environment and the reduction of vegetation residue. Thus,the abandonment of cultivated land is an effective way for restoring soil organic carbon.

Bio-geomorphologic features and growth process of Tamarix nabkhas in Hotan River Basin, Xinjiang

Tamarix nabkha is one of the most widespread nabkhas, distributing in the arid region of China. Based on the observations outdoors and the simulation experiments in laboratories, analysis in this paper refers to the biological geomorphologic features and growth process of Tamarix nabkhas in the middle and lower reaches of the Hotan River, Xinjiang. And the results indicate that the ecological type of Tamarix in the study area is a kind of Tugaic soil habitat based on the deep soil of the Populus Diversifolia forests and shrubs. This type of habitat can be divided into three kinds of sub-habitats which demonstrate the features of ecological environment of Tamarix nabkhas during the differential developed phases. Meanwhile, the Tamar, ix nabkha can exert intensified disturbance current on wind-sand flow on the ground,and its root and stems not only have strong potential of sprouting but are characteristic of wind erosion-tolerance, resistance to be buried by sand and respectively tough rigid of the lignified branches, for it has a rather longer life-time. Thus, the wind speed profile influenced by the Tamarix nabkha is different from the Phragmites nabkha and Alhagi nabkha. And the structure of the wind flow is beneficial to aeolian sand accumulating in/around Tamarix shrub, which can create unique Tamarix nabkhas with higher average gradient and longer periodicity of life. Tamarix nabkha evolution in the area experienced three stages： growth stage, mature and steady stage and withering stage. In each stage, morphological features and geomorphic process of Tamarix nabkha are different due to the discrep- ant interaction between the nabkha and aeolian sand flow.

C:N:P stoichiometry of perennial herbs’ organs in the alpine steppe of the northern Tibetan Plateau

The patterns of C:N:P stoichiometry across ecosystems are important in understanding biogeochemical processes. The stoichiometry of nutrients at the leaf and root level have been reported previously, but relationships of other plant organs, such as stems and the reproductive organs, remain unclear. We collected 228 samples of leaves, roots, stems and reproductive organs from 11 common plant species at 25 sites on the Tibetan Plateau to explore the relationships of C:N:P stoichiometry both within and across plant organs. The average C concentrations in the roots, leaves, stems and reproductive organs were 427.32, 410.51, 421.11 and 416.72 mg g-1, respectively. The shoot tissues(leaves, stems and reproductive organs) had significantly higher N and P concentrations than the roots. The N and P concentrations had a significant positive correlation within the same organ. The nutrient concentrations(N and P) and nutrient ratios(C:N, C:P and N:P) were significantly correlated across all pairwise organ combinations. Our data suggest that alpine perennial herbs share similar evolutionary histories and have constrained patterns of covariation for C concentrations, with differential patterns for N and P stoichiometry across organs. Our data also indicate that covarying sets of nutrient traits are consistent across environments and biogeographical regions and demonstrate convergent evolution in plant nutritional characteristics in extreme alpine environments.

Paleo-Tethyan Oceanic Crust Subduction in the Eastern Section of the East Kunlun Orogenic Belt:Geochronology and Petrogenesis of the Qushi'ang Granodiorite

The Qushi’ang granodiorite（QSG） is located at the central east of the ophiolitic melange belt in the East Kunlun Orogenic Belt（EKOB） in the northern margin of the Qinghai-Tibetan Plateau. LA-MC-ICP-MS zircon U–Pb dating suggests that the granodiorite and mafic microgranular enclaves（MMEs） crystallized 246.61±0.62 and 245.45±0.9 Ma ago, respectively. Granodiorite, porphyritic diorite, and MMEs are metaluminous and medium-K calk-alkaline series, with island-arc magma features, such as LILE enrichment and HFSE depletion. The porphyritic diorite has high Cr（13.50 ppm to 59.01 ppm）, Ni（228.53 ppm to 261.29 ppm）, and Mg~#（46–54）. Granodiorite and porphyritic diorite have similar mineral compositions and evolved major and trace elements contents, particularly Cr and Ni, both of which are significantly higher than that in granites of the same period. The crystallization age of MMEs is close to that of granodiorite, and their major and trace elements contents are in-between porphyritic diorite and granodiorite. The results suggest that the original mafic magma, which was the product of mantle melting by subduction process, intruded into the lower crust（Kuhai Rock Group）, resulting in the formation of granodiorite. Countinous intrusion of mafic magma into the unconsolidated granodiorite formed MMEs and porphyritic diorite. The granodiorite reformed by late-stage strike-slip faulting tectonic event indicates that the strike-slip fault of Middle Kunlun and the collision of the Bayanhar block with East Kunlun were later than 246 Ma. Therefore, the formation of the QSG not only indicates the critical period of evolution of East Kunlun but also represents the tectonic transition from oceanic crust subduction to slab breaking.

Spatiotemporal variability of precipitation during 1961-2014 across the Mongolian Plateau

Precipitation is the dominant factor that controls vegetation growth and land-use practices in the arid and semiarid Mongolian Plateau(MP), so the spatiotemporal heterogeneity of precipitation change has been an important scientific question in the region. This study investigated the spatiotemporal characteristics of annual and seasonal precipitation across the entire MP based on monthly precipitation data from 136 meteorological stations during 1961–2014 by using a modified Mann–Kendall test, Sen's slope, Morlet Wavelet Transform, and geostatistical methods. Results show the following: 1) Annual precipitation decreased slightly from 1961 to 2014.Stations with positive and negative trends were 41.9%and 58.1%, respectively. Significant positive trends were mainly in the southwestern and northeastern regions of the plateau, whereas significant negative trends were in the northern and southeastern regions.2) Precipitation decreased at rates of-5.65 and-0.41 mm/decade in summer and autumn, respectively, but increased at 1.91 and 0.51 mm/decade in spring and winter. The contribution of spring and winter precipitation to the annual amount increased significantly, but that of summer precipitation decreased significantly. 3) A large majority of stations(80.2%) showed decreasing trends in summer,whereas 89.7% and 83.1% of stations showed increasing trends in spring and winter. The spatial distribution of trend magnitude in seasonal precipitation amount was strongly heterogeneous. 4)By climatic zones, precipitation increased in humid and arid zones, but decreased in a semiarid zone. On the whole, the MP experienced a drying trend, with significant regional differentiation and seasonal variations.