Interest in the dynamics of soil respiration(R_(S))in subalpine forest ecosystems is increasing due to their high soil carbon density and potential sensitivity to environmental changes.However,as a principal silvicult...Interest in the dynamics of soil respiration(R_(S))in subalpine forest ecosystems is increasing due to their high soil carbon density and potential sensitivity to environmental changes.However,as a principal silvicultural practice,the long-term impacts of thinning on R_(S) and its heterotrophic and autotrophic respiration components(R_(h) and Ra,respectively)in subalpine plantations are poorly understood,espe-cially in winter.A 3-year field observation was carried out with consideration of winter CO_(2) efflux in middle-aged sub-alpine spruce plantations in northwestern China.A trench-ing method was used to explore the long-term impacts of thinning on Rs,Rn and R_(a).Seventeen years after thinning,mean annual Rs,Rn and R_(a) increased,while the contribu-tion of R_(h) to R_(s) decreased with thinning intensity.Thinning significantly decreased winter R,because of the reduction in R_(n) but had no significant effect on Ra.The temperature sensitivity(Q_(10))of R_(h) and R_(a) also increased with thinning intensity,with lower Q_(10) values for R_(h)(2.1-2.6)than for Ra(2.4-2.8).The results revealed the explanatory variables and pathways related to R_(n) and R_(a) dynamics.Thinning increased soil moisture and nitrate nitrogen(NO_(3)^(-)-N),and the enhanced nitrogen and water availability promoted R_(h) and R_(a) by improving fine root biomass and microbial activity.Our results highlight the positive roles of NO_(3)^(-)-N in stimulating R_(s) components following long-term thinning.Therefore,applications of nitrogen fertilizer are not recommended while thinning subalpine spruce plantations from the perspective of reducing soil CO_(2) emissions.The increased Q_(10) values of R_(s) components indicate that a large increase in soil CO_(2) emissions would be expected following thinning because of more pronounced climate warming in alpineregions.展开更多
The cosmic-ray neutron technology is a novel method for upscaling soil moisture,holding significant importance in drought monitoring,soil water storage estimation,calibration of remote sensing products,and data assimi...The cosmic-ray neutron technology is a novel method for upscaling soil moisture,holding significant importance in drought monitoring,soil water storage estimation,calibration of remote sensing products,and data assimilation of land surface models.However,most studies conducted soil moisture measurement experiments using static Cosmic-Ray Neutron Sensors(CRNS)and are often limited to a single landscape,lacking in-situ measurement for the cosmic-ray neutron rover across various landscapes.This study carried out soil moisture observation experiments using a cosmic-ray neutron rover in nine grassland plots,nine farmland plots,and nine desert plots of the Heihe River Basin,Northwest China.The neutron counts displayed clear variations among different plots,and an equation could represent the relationship between neutron intensity and multiple variables near the ground.The parameter N0 was the smallest for grassland and greatest for desert,and there was a significant negative correlation between Normalized Difference Vegetation Index and N0(P<0.05).Furthermore,the performance of CRNS notably improved after considering soil lattice water and soil organic matter.The Root Mean Square Error(RMSE)between the measured and oven-dried soil moisture increased with radius.Soil moisture measured by CRNS strongly supported the 100 m diameter footprint assumption(RMSE<0.044 g/g).The study offers valuable insights into the application and promotion of cosmic-ray neutron technology across various landscapes within a basin.展开更多
As a main component in water balance, evapotranspiration is of great importance for water saving and irrigation-measure making, especially in arid or semiarid regions. Although studies of evapotranspiration have been ...As a main component in water balance, evapotranspiration is of great importance for water saving and irrigation-measure making, especially in arid or semiarid regions. Although studies of evapotranspiration have been conducted for a long time, studies concentrated on oasis-desert transition zone are very limited. On the basis of the meteorological data and other parameters（e.g. leaf area index（LAI）） of an oasis-desert transition zone in the middle stream of Heihe River from 2005 to 2011, this paper calculated both reference（ET0） and actual evapotranspiration（ETc） using FAO56 Penman-Monteith and Penman-Monteith models, respectively. In combination with pan evaporation（Ep） measured by E601 pan evaporator, four aspects were analyzed：（1） ET0 was firstly verified by Ep;（2） Characteristics of ET0 and ETc were compared, while the influencing factors were also analyzed;（3） Since meteorological data are often unavailable for estimating ET0 through FAO56 Penman-Monteith model in this region, pan evaporation coefficient（Kp） is very important when using observed Ep to predict ET0. Under this circumstance, an empirical formula of Kp was put forward for this region;（4） Crop coefficient（Kc）, an important index to reflect evapotranspiration, was also analyzed. Results show that mean annual values of ET0 and ETc were 840 and 221 mm, respectively. On the daily bases, ET0 and ETc were 2.3 and 0.6 mm/d, respectively. The annual tendency of ET0 and ETc was very similar, but their amplitude was obviously different. The differences among ET0 and ETc were mainly attributed to the different meteorological variables and leaf area index. The calculated Kc was about 0.25 and showed little variation during the growing season, indicating that available water（e.g. precipitation and irrigation） of about 221 mm/a was required to keep the water balance in this region. The results provide an comprehensive analysis of evapotranspiration for an oasis-desert transition zone in the middle stream of Heihe River, which was seldom reported before.展开更多
Picea crassifolia Kom, a perennial arbor spe- cies is recognized as one of the most adaptable plants found to date in Qilian Mountains. To explore the cutting reproduction technology of P. crassifolia and reveal its r...Picea crassifolia Kom, a perennial arbor spe- cies is recognized as one of the most adaptable plants found to date in Qilian Mountains. To explore the cutting reproduction technology of P. crassifolia and reveal its rooting mechanism, cuttings of P. crassifolia with different cutting types （softwood, hardwood and root）, positions （top, upper, middle and bottom） and ages （7, 10, 15, 20, 25 year-old） were cultivated in a field experiment. One- year old softwood and hardwood cuttings were collected from 7-, 10-, 15-, 20-, and 25 year-old healthy ortets to analyze the changes from endogenous hormones and organic nutrients. Results indicate that the softwood cut- tings （0.5-1.0 cm in diameter） from upper branches of 15 year-old ortets shows better growth performance by improving rooting indexes, including a significant increasein rooting rate and a decrease in basal rot rate. Concomi- tantly, increasing rooting quantity and root length also increased. It is noteworthy that the high rooting rate of P. crassifolia cuttings due to its ability to accumulate high concentrations of indole-3-acetic acid （IAA） and total carbon （TC） rather than abscisic acid （ABA） and total nitrogen （TN）. The rooting rate was mainly regulated by the IAA/ABA and TC/TN ratio. In summary, our results suggest that the softwood cuttings （0.5-1.0 cm in diameter） from upper branches of 15 year-old P. crassifolia can be considered as an effective strategy to improve cutting rooting rate, and the IAA/ABA and TC/TN ratio was one of the main factors limiting the cutting rooting rate of P. crassifolia.展开更多
Shrub presence has an important effect on the structuring of ground beetles in desert ecosystems. In this study, in order to determine how shrubs and different species influence ground beetle assemblages in a sandy de...Shrub presence has an important effect on the structuring of ground beetles in desert ecosystems. In this study, in order to determine how shrubs and different species influence ground beetle assemblages in a sandy desert scrubland dominated by two different shrub species, namely Calligonum mongolicum and Nitraria sphaerocarpa, we sampled the ground beetles using pitfall traps during spring, summer and autumn in 2012. At the community level, the activity density of the ground beetles was shown to be significantly higher under shrubs than in intershrub bare habitats in spring; but an opposite pattern occurred in autumn, suggesting the presence of sea- son-specific shrub effects on the activity density of the ground beetles. Meanwhile, at the trophic group level, the activity density and species richness of predators were significantly greater under shrubs than in intershrub bare habitats in spring, whereas an opposite trend occurred on the activity density in autumn. N. sphaerocarpa shrubs had a positive effect on the activity density of herbivores in the three seasons, and C. mongolicum shrubs had a positive effect on the activity density of detritivores in spring and autumn. At the species level, more Microdera sp. was captured under shrubs than in intershrub bare habitats in spring. During the same time, we also found that C. mongolicum shrubs had a positive effect on Blaps gobiensis in spring, Carabus sp. in autumn, and Tentyria sp. in spring and autumn, and N. sphaerocarpa shrubs had a positive effect on Cyphogenia chinensis, Sternoplax setosa in spring and summer, and Curculionidae sp. 1 in summer and autumn. The study results suggest that shrub presence, shrub species and season variation are important factors for ground beetle assemblages in this desert ecosystem, but the responses of beetles differed among trophic and taxonomic levels.展开更多
Shrub is an important factor on structuring ground arthropod communities in desert ecosystems. In this study, in order to determine how shrubs and their species influence ground arthropod distribution patterns in a sa...Shrub is an important factor on structuring ground arthropod communities in desert ecosystems. In this study, in order to determine how shrubs and their species influence ground arthropod distribution patterns in a sandy desert scrubland dominated by two different shrub species, Calligonum mongolicum and Nitraria sphaerocarpa, the ground arthropods were sampled with pitfall traps during spring, summer and autumn. At the community level, total arthropod abundance was shown to be significantly higher under shrubs than in intershrub bare areas in spring; similar patterns occurred in terms of the richness of arthropod groups in the spring and over three seasons, suggesting season-specific shrub presence effects on arthropod activity. In addition, more arthropods were found under N. sphaerocarpa shrubs than under C. rnongolicum shrubs in autumn, suggesting season-specific effects of shrub species of arthropod activity, whereas more arthropods taxa were captured under C. mongoIicum than N. sphaerocarpa. At the trophic group level, the abundances of predator and herbivore arthropods were significantly greater under shrubs than in intershrub bare habitats, whereas herbivore arthropods were more abundant under N. sphaerocarpa than C. rnongolicum, and an opposite rule was detected for predator arthropods At the family level, the mean abundances of Carabidae, Curculionidae, Gnaphosidae and Lycosidae were significantly higher in the shrub microhabitats than in the intershrub bare habitat, there was no significant difference between habitats on the mean abundances of Formicidae and Tenebrionidae. The study results suggested that shrub presence and shrub species variation are important determinants of ground arthropod assemblages in this desert ecosystem, but the responses of ar- thropods differed among trophic and taxonomic groups.展开更多
Understanding the effect of biodiversity on ecosystem function is critical to promoting the sustainability of ecosystems and species conservation in natural ecosystems. We observed species composition, species richnes...Understanding the effect of biodiversity on ecosystem function is critical to promoting the sustainability of ecosystems and species conservation in natural ecosystems. We observed species composition, species richness and aboveground biomass,and simulated the competitive assemblages in a natural grassland ecosystem of China, aiming to test some assumptions and predictions about biodiversity–stability relationships. Our results show that aboveground productivity and temporal stability increased significantly with increasing species richness, and via a combination of overyielding, species asynchrony, and portfolio effects. Species interactions resulted in overyielding caused by trait-independent complementarity, and were not offset by a negative dominance effect and trait-dependent complementarity effect. Therefore, the mechanisms underlying the biodiversity effect shifted from the selection effect to the complementarity effect as diversity increased, and both effects were coexisted but the complementarity effect represent a mechanism that facilitates long term species coexistence in a natural grassland ecosystem of China.展开更多
Carex brunnescens(Pers.)Poir.is considered to be the only clonal herb found to date that can develop and form fixed dunes in Maqu alpine degraded grasslands of northwestern China.However,due to strong dormant characte...Carex brunnescens(Pers.)Poir.is considered to be the only clonal herb found to date that can develop and form fixed dunes in Maqu alpine degraded grasslands of northwestern China.However,due to strong dormant characteristics of C.brunnescens seeds,the sand-fixing effect of the plant is severely limited.This study explores a technique that can rapidly promote the seed germination of C.brunnescens,and also investigates the adaptation and sand-fixing effect by cultivating C.brunnescens seedlings to establish living sand barriers in the sand ridges of moving sand dunes.Results show that the seed germination rate obtained a maximum of 63.7%or 65.1%when seeds were treated with 150 mg/L gibberellic acid(GA3)for 24 h followed by soaking in sulfuric acid(98%H2SO4)for 2.5 min or sodium hydroxide(10%NaOH)for 3.5 h,and then germinated(25°C in daytime and 5°C at nighttime)in darkness for 10 d.After breaking seed dormancy of C.brunnescens,the living sand barrier of C.brunnescens(plant spacing 15−20 cm;sand barrier spacing 10−20 m)was established in the perpendicular direction to the main wind in the middle and lower parts of the sand ridges on both sides of the moving sand dunes.When the sand ridges were leveled by wind erosion,the living sand barrier(plant spacing 15−20 cm;sand barrier spacing 0.5−1.0 m)of C.brunnescens was reestablished on the wind-eroded flat ground.Finally,a stable sand-fixing surface can be formed after connecting the living sand barriers on both sides,thus achieving a good sand-fixing effect.These findings suggest that rapid seed germination technology combined with the sand−fixing method of C.brunnescens can shorten the seed germination period and make the seedling establishment become much easier which may be an effective strategy to restore and reconstruct Maqu degraded grasslands.展开更多
Climate constitutes the main limiting factor for tree-ring growth in high-elevation forests, and the relationship between tree-ring growth and climate is complex. Based on tree-ring chronology and meteorological data,...Climate constitutes the main limiting factor for tree-ring growth in high-elevation forests, and the relationship between tree-ring growth and climate is complex. Based on tree-ring chronology and meteorological data, the influence of precipitation, mean temperature and mean minimum temperature at yearly, seasonal and monthly scales on the tree-ring growth of Picea crossifolia was studied at treeline ecotones in the Qilian Mountains, northwestern China. The results show that growing season temperatures of previous and current years are important limiting factors on tree-ring growth, particularly June mean temperature and mean minimum temperature of current year. The precipitations in the previous winter and current spring have a positive correlation, and in the current fall has a negative correlation with tree-ring growth, but these correlations are not significant. Our results suggest that temperature controls tree-ring growth more strongly than precipitation at treeline ecotones in the Qilian Mountains.展开更多
Stress gradient hypothesis predicted that facilitative interactions usually increase in intensity and are importance with abiotic stress.By contrast,facilitation may be lost in time,when it involves the growth of bene...Stress gradient hypothesis predicted that facilitative interactions usually increase in intensity and are importance with abiotic stress.By contrast,facilitation may be lost in time,when it involves the growth of benefactors or beneficiaries.Less is known about which response pattern is more common in arid desert.We present an empirical study to explore shrub-annual interactions at the community and individual level along the course of a single growing season in a desert steppe in northwest China.Here the severity of drought stress may increase in time due to uneven precipitation during plant growing season.We assessed growth responses of annuals in understory where two dominant shrubs were removed.Annuals responses showed a switch from weakly positive to more strongly positive beneath Calligonum mongolicum,whereas from positive to negative beneath Nitraria sphaerocarpa during the growing season.Additionally,annual species with contrasting functional traits showed distinct growth responses to canopies removal.There was evidence of an increase in soil moisture below the canopy of shrubs,but a decrease in potential evaporation rate and photosynthetically active radiation,which can partly explain these species-specific responses.We conclude that the balance between competitive and facilitative effects in shrub-annual interactions is not only governed by the severity of stress but also determined by plant traits,such as canopy structure of shrubs and functional traits of their understory annuals.展开更多
Furrow irrigation with film-mulched agricultural beds is being promoted in the arid region of northwest China because it improves water utilization. Two-dimensional infiltration patterns under film-mulched furrows can...Furrow irrigation with film-mulched agricultural beds is being promoted in the arid region of northwest China because it improves water utilization. Two-dimensional infiltration patterns under film-mulched furrows can provide guidelines and criteria for irrigation design and operation. Our objective was to investigate soil water dynamics during ponding irrigation infiltration of mulched furrows in a cross-sectional ridge-furrow configuration, using laboratory experiments and mathematical simulations. Six experimental treatments, with two soil types （silt loam and sandy loam）, were investigated to monitor the wetting patterns and soil water distribution in a cuboid soil chamber. Irrigation of mulched furrows clearly increased water lateral infiltration on ridge shoulders and ridges, due to enhancement of capillary driving force. Increases to both initial soil water content （SWC） and irrigation water level resulted in increased wetted soil volume. Empirical regression equations accurately estimated the wetted lateral distance （Rl） and downward distance （Rd） with elapsed time in a variably wetted soil medium. Optimization of model parameters followed by the Inverse approach resulted in satisfactory agreement between observed and predicted cumulative infiltration and SWC. On the basis of model calibration, HYDRUS-2D model can accurately simulate two-dimensional soil water dynamics under irrigation of mulched furrows. There were significant differences in wetting patterns between unmulched and mulched furrow irrigation using HYDRUS-2D simulation. The Rd under the mulched furrows was 32.14% less than the unmulched furrows. Therefore, film-mulched furrows are recommended in a furrow irrigation system.展开更多
Ultraviolet（UV） radiation has significant effects on ecosystems, environments, and human health, as well as atmospheric processes and climate change. Two ultraviolet radiation datasets are described in this paper. O...Ultraviolet（UV） radiation has significant effects on ecosystems, environments, and human health, as well as atmospheric processes and climate change. Two ultraviolet radiation datasets are described in this paper. One contains hourly observations of UV radiation measured at 40 Chinese Ecosystem Research Network stations from 2005 to 2015. CUV3 broadband radiometers were used to observe the UV radiation, with an accuracy of 5%, which meets the World Meteorology Organization＇s measurement standards. The extremum method was used to control the quality of the measured datasets. The other dataset contains daily cumulative UV radiation estimates that were calculated using an all-sky estimation model combined with a hybrid model. The reconstructed daily UV radiation data span from 1961 to 2014. The mean absolute bias error and root-mean-square error are smaller than 30% at most stations, and most of the mean bias error values are negative, which indicates underestimation of the UV radiation intensity. These datasets can improve our basic knowledge of the spatial and temporal variations in UV radiation. Additionally, these datasets can be used in studies of potential ozone formation and atmospheric oxidation, as well as simulations of ecological processes.展开更多
Understanding the variation in a plant’s water sources is critical to understanding hydrological processes in water-limited environments. Here, we measured the stable-isotope ratios(δ18 O) of xylem water of Caragana...Understanding the variation in a plant’s water sources is critical to understanding hydrological processes in water-limited environments. Here, we measured the stable-isotope ratios(δ18 O) of xylem water of Caragana microphylla, precipitation,soil water from different depths, and groundwater to quantitatively analyze the proportion of water sources for the shrub.We found that the water sources of C. microphylla differed with the plant’s ages and the seasons. The main water source for young shrubs was upper-soil water, and it showed significant changes with seasonal precipitation inputs. In summer,the proportion contributed by shallow water was significantly increased with increased precipitation inputs. Then, the contribution from shallow-soil water decreased with the decline in precipitation input in spring and autumn. However, the adult shrubs resorted to deep-soil layers and groundwater as the main water sources during the whole growing season and showed much less seasonal variation. We conclude that the main water source of the young shrubs was upper-soil water and was controlled by precipitation inputs. However, once the shrub gradually grew up and the roots reached sufficient depth, the main water sources change from the upper-soil layer recharged by precipitation to deep-soil water and groundwater, which were relatively stable and abundant in the desert ecosystem. These results also suggest that desert shrubs may be able to switch their main water sources to deep and reliable water sources as their age increases, and this adjustment to water availability carries significant importance for their acclimation to the desert habitat.展开更多
Oasisization is a process of converting a natural desert into a man-made oasis in order to satisfy social needs under certain economical and technical conditions. This paper substitutes space for time in order to stud...Oasisization is a process of converting a natural desert into a man-made oasis in order to satisfy social needs under certain economical and technical conditions. This paper substitutes space for time in order to study physical property changes of oasis soil along the oasisization in about a 1,000-year period. This research focuses on providing the bases for better understanding the process of oasisization. The results show: (1) In about 1,000-year chronological scale, the bulk density and the saturated soil hydraulic conductivity of the surface layer (0-20 cm) significantly reduced with the increase of land reclamation time, while soil porosity, stability of aggregates, and silt content significantly increased. The soil bulk density of the unreclaimed filed (0 year) and the reclaimed field (about 1,000 years) in the surface layer (0-20 cm) are 1.51 g/cm3 and 1.35 g/cm3, the total porosity are 43.16% and 49.27%, the capillary porosity are 38.73% and 47.10%, the water-stable aggregate (】0.25 mm) content are 24.60% and 49.59%, the sand content are 85.42% and 61.56%, the clay content are 3.93% and 4.80%, the specific surface area are 128 cm2/g and 231 cm2/g, and the saturated hydraulic conductivity are 0.74 cm/h and 0.34 cm/h, respectively. (2) In the first 30 years of the oasis reclamation, the changes are relatively fast, and the rates of the saturated soil hydraulic conductivity, dry aggregate (】0.25 mm), water-stable aggregate (】0.25 mm) content, and specific surface area are 0.01 cm/h·yr, 0.58%/yr, 0.50%/yr, and 1.48 cm2/g yr, respectively.展开更多
Landscapes of the mountainous regions in northwestern China comprise a unique pattern of vegetation,consisting of a mosaic of grassland and shrub-forest.Forests generally self-organize into ordered structures and coal...Landscapes of the mountainous regions in northwestern China comprise a unique pattern of vegetation,consisting of a mosaic of grassland and shrub-forest.Forests generally self-organize into ordered structures and coalesce into blocks on north-facing slopes or stripes along southeast-facing slopes,with Picea crassifolia being the most representative and dominant tree species.We investigated the tree-water status and soil-moisture dynamics at a forest site(Guantan)of the Qilian Mountains in northwest China.The 30-minute-interval measurements of tree-sap flow during the growing season of 2008 are presented,and the potential functional relations between tree transpiration and environmental factors are evaluated.Soil moisture and solar energy were identified as the most influential factors,explaining more than 70%of the variance in sap flow.Based on field measurements obtained at the forest site,a stochastic model of soil-moisture dynamics was tested;and the steady-state probability density functions(PDFs)of the long-term soil-moisture dynamics and static tree-water stress were estimated using the validated model and parameters.We found that the model reproduced measured soil moisture well,despite all the simplifying assumptions.The generated PDF of long-term soil moisture was relatively open,with middle to low average values;and the calculated density of the static tree-water stress at the forest site was largely concentrated between 0 and 0.6,suggesting a moderate water-stress situation in most cases.We argue that both water and energy are limiting factors for vegetation at the forest site.In addition,the tradeoff between reduced evapotranspiration(ET)from limited solar energy and increased soil-moisture availability may create a stressed but tolerable environment and,in turn,produce a relatively constant ecological niche favorable to Picea crassifolia growth.展开更多
Face-to-face interviews(n=860) were conducted to determine cash-gift behavior, cognition and complexity of social relations, and family water consumption for agricultural production in a typical oasis area in Northwes...Face-to-face interviews(n=860) were conducted to determine cash-gift behavior, cognition and complexity of social relations, and family water consumption for agricultural production in a typical oasis area in Northwest China. The survey results revealed cash gifts to be the second-largest expenditure(1,330 Yuan) for rural households, far beyond the average spending on health(854.1 Yuan) or education(890.8 Yuan). The amount of cash-gift expenditures indirectly reflects a family's social relations level, and our developed Social Relations Extent Coefficient—based on cash-gift and food expenditures—can directly reflect the extent or level of these relationships. Different types of farmers or farming families have different coefficients. The coefficient also shows how social station affects a family's water resource utilization, and how water is distributed among different types of farmers. Despite the current inequities, however, promotion of better agricultural techniques and large-scale cultivation in this area could help distribute water resources more equitably and effectively.展开更多
Water consumption is a key role in improving the efficiency and sustainability of water management in arid environments.In this study, we explored an approach based on meta-analysis, MODIS NDVI products, land-use spat...Water consumption is a key role in improving the efficiency and sustainability of water management in arid environments.In this study, we explored an approach based on meta-analysis, MODIS NDVI products, land-use spatial distribution, andsoil water physical parameters to gain insight into long-term and large scale distribution of land use and water consumption,maintain maximum Zhangye Oasis area according to Heihe River runoff, and suitable water resource management inZhangye Oasis. This approach was initiated in order to improve the efficiency of irrigation and water resource managementin arid regions. Results showed that Heihe River runoff can maintain a maximum Zhangye Oasis area of 22.49×104 hm2.During the 2000−2016 growing seasons, actual oasis water consumption ranged from 11.35×108 m3 to 13.73×108 m3, witha mean of (12.89 ± 0.60)×108 m3;if maintaining agricultural production and oasis stability was chosen, oasis water consumptionranged from 10.24×108 m3 to 12.37×108 m3, with a mean of (11.62 ± 0.53)×108 m3. From the perspective of waterresources management and ecosystem stability, it is necessary to reduce the area of Zhangye Oasis or choose the minimumwater consumption method to manage the oasis, to ease the pressure of water shortage and maintain stable and sustainabledevelopment of the Zhangye Oasis. These results can provide future practical guidance for water resource management ofcoordinated development of the economy and the environment in an arid area.展开更多
Overuse of irrigation water to ensure the crop yield of maize plants has caused serious water shortage problems in the middle reach of Heihe River, China. Thus, further research on the physiological characteristics, i...Overuse of irrigation water to ensure the crop yield of maize plants has caused serious water shortage problems in the middle reach of Heihe River, China. Thus, further research on the physiological characteristics, i.e., photosynthetic rate and leaf transpiration rate, are urgently needed to develop an efficient irrigation management system. In this paper, we selected two common soil textures （sandy loam, sand） and three one-time irrigation volumes （60 mm, 20 mm, 0 mm） in order to analyze the impact of soil conditions on the physiological characteristics of maize plants. Physiological and meteorological factors, soil water content and plant growing parameters were synchronously monitored on Jun. 30, Jul. 25 and Aug. 27 of 2012. The results indicate that sandy loam is better than sand for the growth of maize plants and single irrigation may provide limited influence on the physiological characteristics. Thus, increasing irrigation times and decreasing one-time volume is suggested for an efficient irrigation system.展开更多
Nebkhas, discrete mounds of sand and vegetation, are a common landscape feature critical to the stability of desert ecosystems and supported by limited precipitation. Nebkha morphology and spatial pattern vary in land...Nebkhas, discrete mounds of sand and vegetation, are a common landscape feature critical to the stability of desert ecosystems and supported by limited precipitation. Nebkha morphology and spatial pattern vary in landscapes, but it is unclear how they change along precipitation gradients in arid and semi-arid regions. In this study we determined morphology and soil nutrient patterns of nebkha from different regions of northwestern China. The objective of this study was to understand zonal differences among nebkhas and how morphological characteristics and soil nutrient patterns of nebkha change along a precipitation gradient in northwestern China. Our results shows that mean annual precipitation(MAP) had significant effects on morphological characteristics of nebkhas such as height, area, and volume which significantly decreased with an increase in MAP. MAP had significant positive effects on shrub cover and species richness of nebkha. Soil nutrients such as soil organic matter(SOM), total carbon(TC), total nitrogen(TN), and total phosphorus(TP) in the 0-10 cm layer increased with an increase of MAP, and soil nutrient content within nebkhas was higher than in inter-nebkha areas.We concluded that nebkhas are "fertile islands" with an important role in ecosystem dynamics in study regions. Further,MAP is a key factor which determined zonal differences, morphological, and soil nutrients patterns of nebkhas. However,disturbance, such as animal grazing, and planted sand-stabilizing vegetation accelerated the degeneration of nebkha landscapes. We recommend implementation of protective measures for nebkhas in arid and semi-arid areas of China.展开更多
The aim of this study is to explore a way that quantify the qualitative equation of bone growth and remodeling which was based on the animal Experiment of rapid-growing Rats in Different Stress Environment. These resu...The aim of this study is to explore a way that quantify the qualitative equation of bone growth and remodeling which was based on the animal Experiment of rapid-growing Rats in Different Stress Environment. These results were proved to be of good stability and identification precision with the numerical method of inversion. It suggested that the growing coefficient and the threshold in function were variables changing with time and space. The idea and method used in the research of bone growth and remodeling adaptation in this paper also provided clue and reference to establish other models for living system.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos.41701296 and 42277481)the Natural Science Foundation of Gansu Province (GrantNo.22JR5RA058)the Youth Science and Technology Fund Program of Gansu Province (Grant No.22JR5RA087).
文摘Interest in the dynamics of soil respiration(R_(S))in subalpine forest ecosystems is increasing due to their high soil carbon density and potential sensitivity to environmental changes.However,as a principal silvicultural practice,the long-term impacts of thinning on R_(S) and its heterotrophic and autotrophic respiration components(R_(h) and Ra,respectively)in subalpine plantations are poorly understood,espe-cially in winter.A 3-year field observation was carried out with consideration of winter CO_(2) efflux in middle-aged sub-alpine spruce plantations in northwestern China.A trench-ing method was used to explore the long-term impacts of thinning on Rs,Rn and R_(a).Seventeen years after thinning,mean annual Rs,Rn and R_(a) increased,while the contribu-tion of R_(h) to R_(s) decreased with thinning intensity.Thinning significantly decreased winter R,because of the reduction in R_(n) but had no significant effect on Ra.The temperature sensitivity(Q_(10))of R_(h) and R_(a) also increased with thinning intensity,with lower Q_(10) values for R_(h)(2.1-2.6)than for Ra(2.4-2.8).The results revealed the explanatory variables and pathways related to R_(n) and R_(a) dynamics.Thinning increased soil moisture and nitrate nitrogen(NO_(3)^(-)-N),and the enhanced nitrogen and water availability promoted R_(h) and R_(a) by improving fine root biomass and microbial activity.Our results highlight the positive roles of NO_(3)^(-)-N in stimulating R_(s) components following long-term thinning.Therefore,applications of nitrogen fertilizer are not recommended while thinning subalpine spruce plantations from the perspective of reducing soil CO_(2) emissions.The increased Q_(10) values of R_(s) components indicate that a large increase in soil CO_(2) emissions would be expected following thinning because of more pronounced climate warming in alpineregions.
基金supported by the National Natural Science Foundation of China(Nos.42071044,42230720)the Strategic Priority Research Program of the Chinese Academy of Sciences(CAS)(No.XDA23060304)the Youth Innovation Promotion Association CAS(No.2020420).
文摘The cosmic-ray neutron technology is a novel method for upscaling soil moisture,holding significant importance in drought monitoring,soil water storage estimation,calibration of remote sensing products,and data assimilation of land surface models.However,most studies conducted soil moisture measurement experiments using static Cosmic-Ray Neutron Sensors(CRNS)and are often limited to a single landscape,lacking in-situ measurement for the cosmic-ray neutron rover across various landscapes.This study carried out soil moisture observation experiments using a cosmic-ray neutron rover in nine grassland plots,nine farmland plots,and nine desert plots of the Heihe River Basin,Northwest China.The neutron counts displayed clear variations among different plots,and an equation could represent the relationship between neutron intensity and multiple variables near the ground.The parameter N0 was the smallest for grassland and greatest for desert,and there was a significant negative correlation between Normalized Difference Vegetation Index and N0(P<0.05).Furthermore,the performance of CRNS notably improved after considering soil lattice water and soil organic matter.The Root Mean Square Error(RMSE)between the measured and oven-dried soil moisture increased with radius.Soil moisture measured by CRNS strongly supported the 100 m diameter footprint assumption(RMSE<0.044 g/g).The study offers valuable insights into the application and promotion of cosmic-ray neutron technology across various landscapes within a basin.
基金founded by the National Natural Science Foundation of China (40930634, 41125002)
文摘As a main component in water balance, evapotranspiration is of great importance for water saving and irrigation-measure making, especially in arid or semiarid regions. Although studies of evapotranspiration have been conducted for a long time, studies concentrated on oasis-desert transition zone are very limited. On the basis of the meteorological data and other parameters（e.g. leaf area index（LAI）） of an oasis-desert transition zone in the middle stream of Heihe River from 2005 to 2011, this paper calculated both reference（ET0） and actual evapotranspiration（ETc） using FAO56 Penman-Monteith and Penman-Monteith models, respectively. In combination with pan evaporation（Ep） measured by E601 pan evaporator, four aspects were analyzed：（1） ET0 was firstly verified by Ep;（2） Characteristics of ET0 and ETc were compared, while the influencing factors were also analyzed;（3） Since meteorological data are often unavailable for estimating ET0 through FAO56 Penman-Monteith model in this region, pan evaporation coefficient（Kp） is very important when using observed Ep to predict ET0. Under this circumstance, an empirical formula of Kp was put forward for this region;（4） Crop coefficient（Kc）, an important index to reflect evapotranspiration, was also analyzed. Results show that mean annual values of ET0 and ETc were 840 and 221 mm, respectively. On the daily bases, ET0 and ETc were 2.3 and 0.6 mm/d, respectively. The annual tendency of ET0 and ETc was very similar, but their amplitude was obviously different. The differences among ET0 and ETc were mainly attributed to the different meteorological variables and leaf area index. The calculated Kc was about 0.25 and showed little variation during the growing season, indicating that available water（e.g. precipitation and irrigation） of about 221 mm/a was required to keep the water balance in this region. The results provide an comprehensive analysis of evapotranspiration for an oasis-desert transition zone in the middle stream of Heihe River, which was seldom reported before.
基金supported by the National Natural Science Foundation of China(Grant No.31360086)the grant from the major state basic research development program of china(973 program,No.2013CB429903)
文摘Picea crassifolia Kom, a perennial arbor spe- cies is recognized as one of the most adaptable plants found to date in Qilian Mountains. To explore the cutting reproduction technology of P. crassifolia and reveal its rooting mechanism, cuttings of P. crassifolia with different cutting types （softwood, hardwood and root）, positions （top, upper, middle and bottom） and ages （7, 10, 15, 20, 25 year-old） were cultivated in a field experiment. One- year old softwood and hardwood cuttings were collected from 7-, 10-, 15-, 20-, and 25 year-old healthy ortets to analyze the changes from endogenous hormones and organic nutrients. Results indicate that the softwood cut- tings （0.5-1.0 cm in diameter） from upper branches of 15 year-old ortets shows better growth performance by improving rooting indexes, including a significant increasein rooting rate and a decrease in basal rot rate. Concomi- tantly, increasing rooting quantity and root length also increased. It is noteworthy that the high rooting rate of P. crassifolia cuttings due to its ability to accumulate high concentrations of indole-3-acetic acid （IAA） and total carbon （TC） rather than abscisic acid （ABA） and total nitrogen （TN）. The rooting rate was mainly regulated by the IAA/ABA and TC/TN ratio. In summary, our results suggest that the softwood cuttings （0.5-1.0 cm in diameter） from upper branches of 15 year-old P. crassifolia can be considered as an effective strategy to improve cutting rooting rate, and the IAA/ABA and TC/TN ratio was one of the main factors limiting the cutting rooting rate of P. crassifolia.
基金funded by the National Basic Research Program of China (2013CB429903)the National Natural Science Foundation of China (41201248, 31170496)
文摘Shrub presence has an important effect on the structuring of ground beetles in desert ecosystems. In this study, in order to determine how shrubs and different species influence ground beetle assemblages in a sandy desert scrubland dominated by two different shrub species, namely Calligonum mongolicum and Nitraria sphaerocarpa, we sampled the ground beetles using pitfall traps during spring, summer and autumn in 2012. At the community level, the activity density of the ground beetles was shown to be significantly higher under shrubs than in intershrub bare habitats in spring; but an opposite pattern occurred in autumn, suggesting the presence of sea- son-specific shrub effects on the activity density of the ground beetles. Meanwhile, at the trophic group level, the activity density and species richness of predators were significantly greater under shrubs than in intershrub bare habitats in spring, whereas an opposite trend occurred on the activity density in autumn. N. sphaerocarpa shrubs had a positive effect on the activity density of herbivores in the three seasons, and C. mongolicum shrubs had a positive effect on the activity density of detritivores in spring and autumn. At the species level, more Microdera sp. was captured under shrubs than in intershrub bare habitats in spring. During the same time, we also found that C. mongolicum shrubs had a positive effect on Blaps gobiensis in spring, Carabus sp. in autumn, and Tentyria sp. in spring and autumn, and N. sphaerocarpa shrubs had a positive effect on Cyphogenia chinensis, Sternoplax setosa in spring and summer, and Curculionidae sp. 1 in summer and autumn. The study results suggest that shrub presence, shrub species and season variation are important factors for ground beetle assemblages in this desert ecosystem, but the responses of beetles differed among trophic and taxonomic levels.
基金funded by one of National Basic Research Program of China (No. 2013CB429903)National Natural Science Foundation of China (Grant Nos. 41201248 and 31170496)
文摘Shrub is an important factor on structuring ground arthropod communities in desert ecosystems. In this study, in order to determine how shrubs and their species influence ground arthropod distribution patterns in a sandy desert scrubland dominated by two different shrub species, Calligonum mongolicum and Nitraria sphaerocarpa, the ground arthropods were sampled with pitfall traps during spring, summer and autumn. At the community level, total arthropod abundance was shown to be significantly higher under shrubs than in intershrub bare areas in spring; similar patterns occurred in terms of the richness of arthropod groups in the spring and over three seasons, suggesting season-specific shrub presence effects on arthropod activity. In addition, more arthropods were found under N. sphaerocarpa shrubs than under C. rnongolicum shrubs in autumn, suggesting season-specific effects of shrub species of arthropod activity, whereas more arthropods taxa were captured under C. mongoIicum than N. sphaerocarpa. At the trophic group level, the abundances of predator and herbivore arthropods were significantly greater under shrubs than in intershrub bare habitats, whereas herbivore arthropods were more abundant under N. sphaerocarpa than C. rnongolicum, and an opposite rule was detected for predator arthropods At the family level, the mean abundances of Carabidae, Curculionidae, Gnaphosidae and Lycosidae were significantly higher in the shrub microhabitats than in the intershrub bare habitat, there was no significant difference between habitats on the mean abundances of Formicidae and Tenebrionidae. The study results suggested that shrub presence and shrub species variation are important determinants of ground arthropod assemblages in this desert ecosystem, but the responses of ar- thropods differed among trophic and taxonomic groups.
基金supported by the National Basic Research Program of China (No. 2013CB429903)the National Natural Science Foundation of China (Nos. 41471024 41771038)
文摘Understanding the effect of biodiversity on ecosystem function is critical to promoting the sustainability of ecosystems and species conservation in natural ecosystems. We observed species composition, species richness and aboveground biomass,and simulated the competitive assemblages in a natural grassland ecosystem of China, aiming to test some assumptions and predictions about biodiversity–stability relationships. Our results show that aboveground productivity and temporal stability increased significantly with increasing species richness, and via a combination of overyielding, species asynchrony, and portfolio effects. Species interactions resulted in overyielding caused by trait-independent complementarity, and were not offset by a negative dominance effect and trait-dependent complementarity effect. Therefore, the mechanisms underlying the biodiversity effect shifted from the selection effect to the complementarity effect as diversity increased, and both effects were coexisted but the complementarity effect represent a mechanism that facilitates long term species coexistence in a natural grassland ecosystem of China.
基金the Project of the Youth Talent Development Fund of the Northwest Institute of Eco−Environment and ResourcesChinese Academy of Science(CAREERI)(Y851C81001)+1 种基金the National Natural Science Foundation of China(41877162)the Instrument Functional Development Project from the Technology Service Center of CAREERI(Y429C51007).
文摘Carex brunnescens(Pers.)Poir.is considered to be the only clonal herb found to date that can develop and form fixed dunes in Maqu alpine degraded grasslands of northwestern China.However,due to strong dormant characteristics of C.brunnescens seeds,the sand-fixing effect of the plant is severely limited.This study explores a technique that can rapidly promote the seed germination of C.brunnescens,and also investigates the adaptation and sand-fixing effect by cultivating C.brunnescens seedlings to establish living sand barriers in the sand ridges of moving sand dunes.Results show that the seed germination rate obtained a maximum of 63.7%or 65.1%when seeds were treated with 150 mg/L gibberellic acid(GA3)for 24 h followed by soaking in sulfuric acid(98%H2SO4)for 2.5 min or sodium hydroxide(10%NaOH)for 3.5 h,and then germinated(25°C in daytime and 5°C at nighttime)in darkness for 10 d.After breaking seed dormancy of C.brunnescens,the living sand barrier of C.brunnescens(plant spacing 15−20 cm;sand barrier spacing 10−20 m)was established in the perpendicular direction to the main wind in the middle and lower parts of the sand ridges on both sides of the moving sand dunes.When the sand ridges were leveled by wind erosion,the living sand barrier(plant spacing 15−20 cm;sand barrier spacing 0.5−1.0 m)of C.brunnescens was reestablished on the wind-eroded flat ground.Finally,a stable sand-fixing surface can be formed after connecting the living sand barriers on both sides,thus achieving a good sand-fixing effect.These findings suggest that rapid seed germination technology combined with the sand−fixing method of C.brunnescens can shorten the seed germination period and make the seedling establishment become much easier which may be an effective strategy to restore and reconstruct Maqu degraded grasslands.
基金supported by the Major Research Plan of National Natural Science Foundation of China (No. 91025014),the National Natural Science Foundation of China (No. 30800147)
文摘Climate constitutes the main limiting factor for tree-ring growth in high-elevation forests, and the relationship between tree-ring growth and climate is complex. Based on tree-ring chronology and meteorological data, the influence of precipitation, mean temperature and mean minimum temperature at yearly, seasonal and monthly scales on the tree-ring growth of Picea crossifolia was studied at treeline ecotones in the Qilian Mountains, northwestern China. The results show that growing season temperatures of previous and current years are important limiting factors on tree-ring growth, particularly June mean temperature and mean minimum temperature of current year. The precipitations in the previous winter and current spring have a positive correlation, and in the current fall has a negative correlation with tree-ring growth, but these correlations are not significant. Our results suggest that temperature controls tree-ring growth more strongly than precipitation at treeline ecotones in the Qilian Mountains.
基金financial supported by the National Basic Research Program of China (2013CB429903)the National Natural Science Foundation of China (41301603)
文摘Stress gradient hypothesis predicted that facilitative interactions usually increase in intensity and are importance with abiotic stress.By contrast,facilitation may be lost in time,when it involves the growth of benefactors or beneficiaries.Less is known about which response pattern is more common in arid desert.We present an empirical study to explore shrub-annual interactions at the community and individual level along the course of a single growing season in a desert steppe in northwest China.Here the severity of drought stress may increase in time due to uneven precipitation during plant growing season.We assessed growth responses of annuals in understory where two dominant shrubs were removed.Annuals responses showed a switch from weakly positive to more strongly positive beneath Calligonum mongolicum,whereas from positive to negative beneath Nitraria sphaerocarpa during the growing season.Additionally,annual species with contrasting functional traits showed distinct growth responses to canopies removal.There was evidence of an increase in soil moisture below the canopy of shrubs,but a decrease in potential evaporation rate and photosynthetically active radiation,which can partly explain these species-specific responses.We conclude that the balance between competitive and facilitative effects in shrub-annual interactions is not only governed by the severity of stress but also determined by plant traits,such as canopy structure of shrubs and functional traits of their understory annuals.
基金supported by National Natural Science Foundation of China (NO. 41401036)China Postdoctoral Science Foundation (NO. 2015T81070, 2014M560818)West Light Foundation of the Chinese Academy of Sciences
文摘Furrow irrigation with film-mulched agricultural beds is being promoted in the arid region of northwest China because it improves water utilization. Two-dimensional infiltration patterns under film-mulched furrows can provide guidelines and criteria for irrigation design and operation. Our objective was to investigate soil water dynamics during ponding irrigation infiltration of mulched furrows in a cross-sectional ridge-furrow configuration, using laboratory experiments and mathematical simulations. Six experimental treatments, with two soil types （silt loam and sandy loam）, were investigated to monitor the wetting patterns and soil water distribution in a cuboid soil chamber. Irrigation of mulched furrows clearly increased water lateral infiltration on ridge shoulders and ridges, due to enhancement of capillary driving force. Increases to both initial soil water content （SWC） and irrigation water level resulted in increased wetted soil volume. Empirical regression equations accurately estimated the wetted lateral distance （Rl） and downward distance （Rd） with elapsed time in a variably wetted soil medium. Optimization of model parameters followed by the Inverse approach resulted in satisfactory agreement between observed and predicted cumulative infiltration and SWC. On the basis of model calibration, HYDRUS-2D model can accurately simulate two-dimensional soil water dynamics under irrigation of mulched furrows. There were significant differences in wetting patterns between unmulched and mulched furrow irrigation using HYDRUS-2D simulation. The Rd under the mulched furrows was 32.14% less than the unmulched furrows. Therefore, film-mulched furrows are recommended in a furrow irrigation system.
文摘Ultraviolet（UV） radiation has significant effects on ecosystems, environments, and human health, as well as atmospheric processes and climate change. Two ultraviolet radiation datasets are described in this paper. One contains hourly observations of UV radiation measured at 40 Chinese Ecosystem Research Network stations from 2005 to 2015. CUV3 broadband radiometers were used to observe the UV radiation, with an accuracy of 5%, which meets the World Meteorology Organization＇s measurement standards. The extremum method was used to control the quality of the measured datasets. The other dataset contains daily cumulative UV radiation estimates that were calculated using an all-sky estimation model combined with a hybrid model. The reconstructed daily UV radiation data span from 1961 to 2014. The mean absolute bias error and root-mean-square error are smaller than 30% at most stations, and most of the mean bias error values are negative, which indicates underestimation of the UV radiation intensity. These datasets can improve our basic knowledge of the spatial and temporal variations in UV radiation. Additionally, these datasets can be used in studies of potential ozone formation and atmospheric oxidation, as well as simulations of ecological processes.
基金supported by the National Science Foundation for Distinguished Young Scholars of China (Grant No. 41701035)the Key Program of National Natural Science Foundation of China (Grant No. 41630861)the National Science Foundation for Post-doctoral Scientists of China (Grant No. 2016M602902)
文摘Understanding the variation in a plant’s water sources is critical to understanding hydrological processes in water-limited environments. Here, we measured the stable-isotope ratios(δ18 O) of xylem water of Caragana microphylla, precipitation,soil water from different depths, and groundwater to quantitatively analyze the proportion of water sources for the shrub.We found that the water sources of C. microphylla differed with the plant’s ages and the seasons. The main water source for young shrubs was upper-soil water, and it showed significant changes with seasonal precipitation inputs. In summer,the proportion contributed by shallow water was significantly increased with increased precipitation inputs. Then, the contribution from shallow-soil water decreased with the decline in precipitation input in spring and autumn. However, the adult shrubs resorted to deep-soil layers and groundwater as the main water sources during the whole growing season and showed much less seasonal variation. We conclude that the main water source of the young shrubs was upper-soil water and was controlled by precipitation inputs. However, once the shrub gradually grew up and the roots reached sufficient depth, the main water sources change from the upper-soil layer recharged by precipitation to deep-soil water and groundwater, which were relatively stable and abundant in the desert ecosystem. These results also suggest that desert shrubs may be able to switch their main water sources to deep and reliable water sources as their age increases, and this adjustment to water availability carries significant importance for their acclimation to the desert habitat.
文摘Oasisization is a process of converting a natural desert into a man-made oasis in order to satisfy social needs under certain economical and technical conditions. This paper substitutes space for time in order to study physical property changes of oasis soil along the oasisization in about a 1,000-year period. This research focuses on providing the bases for better understanding the process of oasisization. The results show: (1) In about 1,000-year chronological scale, the bulk density and the saturated soil hydraulic conductivity of the surface layer (0-20 cm) significantly reduced with the increase of land reclamation time, while soil porosity, stability of aggregates, and silt content significantly increased. The soil bulk density of the unreclaimed filed (0 year) and the reclaimed field (about 1,000 years) in the surface layer (0-20 cm) are 1.51 g/cm3 and 1.35 g/cm3, the total porosity are 43.16% and 49.27%, the capillary porosity are 38.73% and 47.10%, the water-stable aggregate (】0.25 mm) content are 24.60% and 49.59%, the sand content are 85.42% and 61.56%, the clay content are 3.93% and 4.80%, the specific surface area are 128 cm2/g and 231 cm2/g, and the saturated hydraulic conductivity are 0.74 cm/h and 0.34 cm/h, respectively. (2) In the first 30 years of the oasis reclamation, the changes are relatively fast, and the rates of the saturated soil hydraulic conductivity, dry aggregate (】0.25 mm), water-stable aggregate (】0.25 mm) content, and specific surface area are 0.01 cm/h·yr, 0.58%/yr, 0.50%/yr, and 1.48 cm2/g yr, respectively.
基金supported by the West Light Foundation of the Chinese Academy of Sciences(awarded to Dr.Hu Liu in 2018)the Youth Innovation Promotion Association of the Chinese Academy of Sciences(awarded to Dr.Hu Liu in 2016)
文摘Landscapes of the mountainous regions in northwestern China comprise a unique pattern of vegetation,consisting of a mosaic of grassland and shrub-forest.Forests generally self-organize into ordered structures and coalesce into blocks on north-facing slopes or stripes along southeast-facing slopes,with Picea crassifolia being the most representative and dominant tree species.We investigated the tree-water status and soil-moisture dynamics at a forest site(Guantan)of the Qilian Mountains in northwest China.The 30-minute-interval measurements of tree-sap flow during the growing season of 2008 are presented,and the potential functional relations between tree transpiration and environmental factors are evaluated.Soil moisture and solar energy were identified as the most influential factors,explaining more than 70%of the variance in sap flow.Based on field measurements obtained at the forest site,a stochastic model of soil-moisture dynamics was tested;and the steady-state probability density functions(PDFs)of the long-term soil-moisture dynamics and static tree-water stress were estimated using the validated model and parameters.We found that the model reproduced measured soil moisture well,despite all the simplifying assumptions.The generated PDF of long-term soil moisture was relatively open,with middle to low average values;and the calculated density of the static tree-water stress at the forest site was largely concentrated between 0 and 0.6,suggesting a moderate water-stress situation in most cases.We argue that both water and energy are limiting factors for vegetation at the forest site.In addition,the tradeoff between reduced evapotranspiration(ET)from limited solar energy and increased soil-moisture availability may create a stressed but tolerable environment and,in turn,produce a relatively constant ecological niche favorable to Picea crassifolia growth.
基金supported by Social Science Foundation of China(17CGL032)Gansu Provincial key research and development foundation(17YF1FA134)
文摘Face-to-face interviews(n=860) were conducted to determine cash-gift behavior, cognition and complexity of social relations, and family water consumption for agricultural production in a typical oasis area in Northwest China. The survey results revealed cash gifts to be the second-largest expenditure(1,330 Yuan) for rural households, far beyond the average spending on health(854.1 Yuan) or education(890.8 Yuan). The amount of cash-gift expenditures indirectly reflects a family's social relations level, and our developed Social Relations Extent Coefficient—based on cash-gift and food expenditures—can directly reflect the extent or level of these relationships. Different types of farmers or farming families have different coefficients. The coefficient also shows how social station affects a family's water resource utilization, and how water is distributed among different types of farmers. Despite the current inequities, however, promotion of better agricultural techniques and large-scale cultivation in this area could help distribute water resources more equitably and effectively.
基金This study was funded under the National Natural Science Foundation of China project(91425302).
文摘Water consumption is a key role in improving the efficiency and sustainability of water management in arid environments.In this study, we explored an approach based on meta-analysis, MODIS NDVI products, land-use spatial distribution, andsoil water physical parameters to gain insight into long-term and large scale distribution of land use and water consumption,maintain maximum Zhangye Oasis area according to Heihe River runoff, and suitable water resource management inZhangye Oasis. This approach was initiated in order to improve the efficiency of irrigation and water resource managementin arid regions. Results showed that Heihe River runoff can maintain a maximum Zhangye Oasis area of 22.49×104 hm2.During the 2000−2016 growing seasons, actual oasis water consumption ranged from 11.35×108 m3 to 13.73×108 m3, witha mean of (12.89 ± 0.60)×108 m3;if maintaining agricultural production and oasis stability was chosen, oasis water consumptionranged from 10.24×108 m3 to 12.37×108 m3, with a mean of (11.62 ± 0.53)×108 m3. From the perspective of waterresources management and ecosystem stability, it is necessary to reduce the area of Zhangye Oasis or choose the minimumwater consumption method to manage the oasis, to ease the pressure of water shortage and maintain stable and sustainabledevelopment of the Zhangye Oasis. These results can provide future practical guidance for water resource management ofcoordinated development of the economy and the environment in an arid area.
基金supported by the China Postdoctoral Science Foundation (Grant No. 2015M572622)the National Natural Science Foundation of China (Grant No. 41501044)
文摘Overuse of irrigation water to ensure the crop yield of maize plants has caused serious water shortage problems in the middle reach of Heihe River, China. Thus, further research on the physiological characteristics, i.e., photosynthetic rate and leaf transpiration rate, are urgently needed to develop an efficient irrigation management system. In this paper, we selected two common soil textures （sandy loam, sand） and three one-time irrigation volumes （60 mm, 20 mm, 0 mm） in order to analyze the impact of soil conditions on the physiological characteristics of maize plants. Physiological and meteorological factors, soil water content and plant growing parameters were synchronously monitored on Jun. 30, Jul. 25 and Aug. 27 of 2012. The results indicate that sandy loam is better than sand for the growth of maize plants and single irrigation may provide limited influence on the physiological characteristics. Thus, increasing irrigation times and decreasing one-time volume is suggested for an efficient irrigation system.
基金supported by the National Basic resource survey (2017FY100200)Natural Science Foundation of China subsidization project (41471435)the West Light Program for Talent Cultivation of the Chinese Academy of Sciences。
文摘Nebkhas, discrete mounds of sand and vegetation, are a common landscape feature critical to the stability of desert ecosystems and supported by limited precipitation. Nebkha morphology and spatial pattern vary in landscapes, but it is unclear how they change along precipitation gradients in arid and semi-arid regions. In this study we determined morphology and soil nutrient patterns of nebkha from different regions of northwestern China. The objective of this study was to understand zonal differences among nebkhas and how morphological characteristics and soil nutrient patterns of nebkha change along a precipitation gradient in northwestern China. Our results shows that mean annual precipitation(MAP) had significant effects on morphological characteristics of nebkhas such as height, area, and volume which significantly decreased with an increase in MAP. MAP had significant positive effects on shrub cover and species richness of nebkha. Soil nutrients such as soil organic matter(SOM), total carbon(TC), total nitrogen(TN), and total phosphorus(TP) in the 0-10 cm layer increased with an increase of MAP, and soil nutrient content within nebkhas was higher than in inter-nebkha areas.We concluded that nebkhas are "fertile islands" with an important role in ecosystem dynamics in study regions. Further,MAP is a key factor which determined zonal differences, morphological, and soil nutrients patterns of nebkhas. However,disturbance, such as animal grazing, and planted sand-stabilizing vegetation accelerated the degeneration of nebkha landscapes. We recommend implementation of protective measures for nebkhas in arid and semi-arid areas of China.
文摘The aim of this study is to explore a way that quantify the qualitative equation of bone growth and remodeling which was based on the animal Experiment of rapid-growing Rats in Different Stress Environment. These results were proved to be of good stability and identification precision with the numerical method of inversion. It suggested that the growing coefficient and the threshold in function were variables changing with time and space. The idea and method used in the research of bone growth and remodeling adaptation in this paper also provided clue and reference to establish other models for living system.
