Bionic microfluidics is garnering increasing attention due to the superior fluidic performance enabled by biomimetic microstructures.Inspired by the unique structures of young pumpkin stems,we fabricate helicoidally p...Bionic microfluidics is garnering increasing attention due to the superior fluidic performance enabled by biomimetic microstructures.Inspired by the unique structures of young pumpkin stems,we fabricate helicoidally patterned microchannels with precisely controlled morphologies using the projection micro-stereolithography(PμSL)-based 3D printing technique.Our helicoidally patterned microchannels achieve approximately twice the liquid lifting height compared to similarly sized smooth microchannels.This improvement is attributed to the enhanced capillary force.The additional meniscus formed between the helicoidally patterned microstructures significantly contributes to the increased capillary effects.Furthermore,the underlying mechanisms of fluidic performance in helicoidally patterned microchannels are theorized using a newly developed equation,which is also employed to optimize the geometric parameters and fluidic performance of the biomimetic helicoidal microchannels.Additionally,our biomimetic helicoidally patterned microchannels facilitate a significant step-lifting phenomenon,mimicking tall trees'transpiration.The fluidic performance of our biomimetic helicoidally patterned microchannels show promise for applications in enhanced liquid lifting,step-lifting,clean-water production,and others.展开更多
Soil water content(SWC)and meteorological conditions,as key environmental variables influencing tree water use,vary highly within the growing season,hindering a better understanding of environmental control mechanisms...Soil water content(SWC)and meteorological conditions,as key environmental variables influencing tree water use,vary highly within the growing season,hindering a better understanding of environmental control mechanisms on canopy transpiration(Ec).Disentangling the effects of these variables on Ec across growing-season stages is crucial for Ec estimation and forest management.In this study,43-year-old Pinus tabuliformis Carr.and 31-yearold Platycladus orientalis(L.)Franco plantations in the semiarid Chinese Loess Plateau were monitored for Ec during the growing season of 2015-2020.The contributions of environmental factors to Ec were assessed using the boosted regression tree(BRT)model.Results showed that the contributions of SWC to Ec were greater at the early(May-June)and late(September)stages,while the contributions of vapor pressure deficit(VPD)and total solar radiation(Rs)to Ec increased at the middle(July-August)stage due to high soil water availability.Overall,Ec in both plantations was dominated by SWC(20.4%≤contributions≤48.8%)and Rs(22.7%≤contributions≤35.8%).Both species exhibited strong stomatal regulation of Ec.Specifically,stomatal opening was significantly inhibited by VPD at the early stage and strongly affected by SWC at the late stage.This study highlights that soil water conditions in artificial forests should be adjusted according to changes in influencing factors on Ec.Particularly during the early and late stages,measures(e.g.,land preparation,thinning,and pruning)can be implemented to improve soil moisture in such dryland forests.展开更多
Evapotranspiration is the most important expenditure item in the water balance of terrestrial ecosystems,and accurate evapotranspiration modeling is of great significance for hydrological,ecological,agricultural,and w...Evapotranspiration is the most important expenditure item in the water balance of terrestrial ecosystems,and accurate evapotranspiration modeling is of great significance for hydrological,ecological,agricultural,and water resource management.Artificial forests are an important means of vegetation restoration in the western Loess Plateau,and accurate estimates of their evapotranspiration are essential to the management and development of water use strategies for artificial forests.This study estimated the soil moisture and evapotranspiration based on the HYDRUS-1D model for the artificial Platycladus orientalis(L.)Franco forest in western mountains of Loess Plateau,China from 20 April to 31 October,2023.Moreover,the influence factors were identified by combining the correlation coefficient method and the principal component analysis(PCA)method.The results showed that HYDRUS-1D model had strong applicability in portraying hydrological processes in this area and revealed soil water surplus from 20 April to 31 October,2023.The soil water accumulation was 49.64 mm;the potential evapotranspiration(ET_(p))was 809.67 mm,which was divided into potential evaporation(E_(p);95.07 mm)and potential transpiration(T_(p);714.60 mm);and the actual evapotranspiration(ET_(a))was 580.27 mm,which was divided into actual evaporation(E_(a);68.27 mm)and actual transpiration(T_(a);512.00 mm).From April to October 2023,the ET_(p),E_(p),T_(p),ET_(a),E_(a),and T_(a) first increased and then decreased on both monthly and daily scales,exhibiting a single-peak type trend.The average ratio of T_(a)/ET_(a) was 0.88,signifying that evapotranspiration mainly stemmed from transpiration in this area.The ratio of ET_(a)/ET_(p) was 0.72,indicating that this artificial forest suffered from obvious drought stress.The ET_(p) was significantly positively correlated with ET_(a),and the R^(2) values on the monthly and daily scales were 0.9696 and 0.9635(P<0.05),respectively.Furthermore,ET_(a) was significantly positively correlated with temperature,solar radiation,and wind speed,and negatively correlated with relative humidity and precipitation(P<0.05);and temperature exhibited the highest correlation with ET_(a).Thus,ET_(p) and temperature were the decisive contributors to ET_(a) in this area.The findings provide an effective method for simulating regional evapotranspiration and theoretical reference for water management of artificial forests,and deepen understanding of effects of each influence factors on ET_(a) in arid areas.展开更多
Transpiration cooling is numerically investigated,where a cooling gas is injected through a carbon composite material into a hot gas channel.To account for microscale effects at the injection interface,an effective pr...Transpiration cooling is numerically investigated,where a cooling gas is injected through a carbon composite material into a hot gas channel.To account for microscale effects at the injection interface,an effective problem is derived.Here,effects induced by microscale structures on macroscale variables,e.g.,cooling efficiency,are taken into account without resolving the microscale structures.For this purpose,effective boundary conditions at the interface between hot gas and porous medium flow are derived using an upscaling strategy.Numerical simulations in 2D with effective boundary conditions are compared to uniform and non-uniform injection.The computations confirm that the effective model provides a more efficient and accurate approximation of the cooling efficiency than the uniform injection.展开更多
Accurate nitrogen(N)nutrition diagnosis is essential for improving N use efficiency in crop production.The widely used critical N(Nc)dilution curve traditionally depends solely on agronomic variables,neglecting crop w...Accurate nitrogen(N)nutrition diagnosis is essential for improving N use efficiency in crop production.The widely used critical N(Nc)dilution curve traditionally depends solely on agronomic variables,neglecting crop water status.With three-year field experiments with winter wheat,encompassing two irrigation levels(rainfed and irrigation at jointing and anthesis)and three N levels(0,180,and 270 kg ha1),this study aims to establish a novel approach for determining the Nc dilution curve based on crop cumulative transpiration(T),providing a comprehensive analysis of the interaction between N and water availability.The Nc curves derived from both crop dry matter(DM)and T demonstrated N concentration dilution under different conditions with different parameters.The equation Nc=6.43T0.24 established a consistent relationship across varying irrigation regimes.Independent test results indicated that the nitrogen nutrition index(NNI),calculated from this curve,effectively identifies and quantifies the two sources of N deficiency:insufficient N supply in the soil and insufficient soil water concentration leading to decreased N availability for root absorption.Additionally,the NNI calculated from the Nc-DM and Nc-T curves exhibited a strong negative correlation with accumulated N deficit(Nand)and a positive correlation with relative grain yield(RGY).The NNI derived from the Nc-T curve outperformed the NNI derived from the Nc-DM curve concerning its relationship with Nand and RGY,as indicated by larger R2 values and smaller AIC.The novel Nc curve based on T serves as an effective diagnostic tool for assessing winter wheat N status,predicting grain yield,and optimizing N fertilizer management across varying irrigation conditions.These findings would provide new insights and methods to improve the simulations of water-N interaction relationship in crop growth models.展开更多
Photosynthesis ( P n ), transpiration ( E ) and water use efficiency ( WUE ) of more than 66 arid sand species from different environmental habitats, shifting sand dune, fixed sand dune, lowland and wetland in ...Photosynthesis ( P n ), transpiration ( E ) and water use efficiency ( WUE ) of more than 66 arid sand species from different environmental habitats, shifting sand dune, fixed sand dune, lowland and wetland in the Maowusu Sand Area were analyzed and the relation among these characteristics and the resource utilization efficiency, taxonomic categories and growth forms of the species were assessed. The results showed that species from Chenopodiaceae, Gramineae, Leguminosae which possessed the C 4 photosynthesis pathway, or C 3 pathway and also with nitrogen_fixation capacities had higher or the highest P n values, i.e., 20～30 μmol CO 2·m -2 ·s -1 , while that of evergreen shrub of Pinaceae had the lowest P n values, i.e., 0～5 μmol CO 2·m -2 ·s -1 . Those species from Compositae, Scrophulariaceae, and Gramineae with C 3 pathway but no N_fixation capacity had the highest E rates, i.e., 20～30 mmol H 2O·m -2 ·s -1 and again the evergreen shrub together with some species from Salicaceae and Compositae had the lowest E rates, i.e., 0～5 mmol H 2O·m -2 ·s -1 . Species from Leguminosae, Gramineae and Chenopodiaceae with C 4 pathway or C 3 pathway with N_fixation capacity, both shrubs and grasses, generally had higher WUE . However, even the physiological traits of the same species were habitat_ and season_specific. The values of both P n and E in late summer were much higher than those in early summer, with average increases of 26%, 40% respectively in the four habitats. WUE in late summer was, however, 12% lower. Generally, when the environments became drier as a result of habitats changed, i.e., in the order of wetland, lowland, fixed sand dune and shifting sand dune, P n and E decreased but WUE increased.展开更多
Transpiration element is included in the integrated stomatal conductance photosynthesis model by considering gaseous transfer processes, so the present model is capable to simulate the influence of boundary layer con...Transpiration element is included in the integrated stomatal conductance photosynthesis model by considering gaseous transfer processes, so the present model is capable to simulate the influence of boundary layer conductance. Leuning in his revised Ball's model replaced relative humidity with VPD s (the vapor pressure deficit from stomatal pore to leaf surface) and thereby made the relation with transpiration more straightforward, and made it possible for the regulation of transpiration and the influence of boundary layer conductance to be integrated into the combined model. If the differences in water vapor and CO 2 concentration between leaf and ambient air are considered, VPD s , the evaporative demand, is influenced by stomatal and boundary layer conductance. The physiological responses of photosynthesis, transpiration, and stomatal function, and the changes of intercellular CO 2 and water use efficiency to environmental factors, such as wind speed, photon flux density, leaf temperature and ambient CO 2, are analyzed. It is shown that if the boundary layer conductance drops to a level comparable with stomatal conductance, the results of simulation by the model presented here differ significantly from those by the previous model, and, in some cases, are more realistic than the latter.展开更多
To know the annual water consumption of forest, it is necessary to acquire the annual transpiration value of stands. This paper is based on the data measured in the typical weather of the growth season, from 1998 to 2...To know the annual water consumption of forest, it is necessary to acquire the annual transpiration value of stands. This paper is based on the data measured in the typical weather of the growth season, from 1998 to 2000, with the LI 1600 Steady Porometer and the general weather information. The daily variation of transpiration in black locust forest ( Robinia pesudoacacia L.) is modeled by Penman Monteith equation. As a result of the model, a continuous daily transpiration in the growth season was calculated. The net radiation, intercepted by black locust forest canopy, was acquired from a semi empirical equation of measuring net radiation R n with the extinction coefficient k and leaf area index LAI . The canopy integral stomatic resistance is a mimesis with an empirical equation of measuring data. Compared with measuring data, the relative error of the modeled ones is less than 12% averagely. At last, the total transpiration of black locust forest during the period of 1998 and 2000 in the growth season of May to October, as an average transpiration of the different density stands, were 192 46, 187 07 and 195 59?mm respectively.展开更多
We tested the transpiration rate ( Tr ) of seven\|year\|old field and two\|year\|old potted Malus pumila cv.Goldspur under different conditions of illumination and soil water. The results showed that the interre...We tested the transpiration rate ( Tr ) of seven\|year\|old field and two\|year\|old potted Malus pumila cv.Goldspur under different conditions of illumination and soil water. The results showed that the interrelationship between Tr of Malus pumila cv.Goldspur and illumination and soil water content ( SWC ) was quite remarkable. Tr increased with the increase of light intensity and SWC . However, when one of the environmental stresses of illumination and water existed, the improvement of the other condition couldn't make Tr rise greatly. Only when SWC was higher than 11%, which arrived at over 55% of the field content ( FC ), or the photosynthetic active radiation ( PAR ) higher than 400?μmol·s -1 m -2 , Tr could rise greatly with the increase of PAR or SWC . But when SWC was higher than 15%, which reached over 75% of FC or PAR higher than 1?000?μmol·s -1 ·m -2 , Tr would not change a lot with the change of PAR or SWC . That PAR and SWC influenced the magnitude of stomatic resistance( RS ) and leaf water potential ( Ψ l) was the basic reason for the Tr responded to them. Light stress reduced the open degree of stomas, so when severe light stress existed ( PAR <100?μmol·s -1 ·m -2 ), RS was larger ( RS >2 0?s·cm -1 ), which led to the decrease of Tr(Tr <5?μgH 2O·s -1 ·cm -2 ). When severe water stress existed( SWC <11% and<55% of FC and soil water potential Ψ ws <-1 15?MPa), RS was higher than 4 00?s·cm -1 and Ψ l lower than -2 10?MPa, which led to Tr lower than 11?μgH 2O·s -1 ·cm -2 . When soil water was adequate( SWC >15% amd over 75% of FC , and Ψ ws >-0 50?MPa), RS was lower than 2 00?s·cm -1 , Ψ l higher than -1 65?MPa and Tr would be higher than 15?μgH 2O·s -1 ·m -2 . The range of SWC , 11%～15%, which accounted for 55% to 75% of FC , and correspond RS (2 00～4 00?s·cm -1 ) were the turning area, where the variable curve of Tr transited from a variable trend to another variable one. It could be considered as the range to control soil water.展开更多
Land surface actual evapotranspiration is an important process that influences the Earth's energy and water cycles and determines the water and heat transfer in the soil-vegetation-atmosphere system.Meanwhile,the ...Land surface actual evapotranspiration is an important process that influences the Earth's energy and water cycles and determines the water and heat transfer in the soil-vegetation-atmosphere system.Meanwhile,the cryosphere's hydrological process is receiving extensive attention,and its water problem needs to be understood from multiple perspectives.As the main part of the Chinese cryosphere,the Tibetan Plateau faces significant climate and environmental change.There are active interaction and pronounced feedback between the environment and ETa in the cryosphere.This article mainly focuses on the research progress of ETa in the Tibetan Plateau.It first reviews the ETa process,characteristics,and impact factors of typical underlying surfaces in the Tibetan Plateau(alpine meadows,alpine steppes,alpine wetlands,alpine forests,lakes).Then it compares the temporal and spatial variations of ETa at different scales.In addition,considering the current greening of cryosphere vegetation due to climate change,it discusses the relationship between vegetation greening and transpiration to help clarify how vegetation activities are related to the regional water cycle and surface energy budget.展开更多
Information on cotton evapotranspiration (ET) during the seedling growth stage and under field conditions is scarce because ET is a difficult parameter to measure. Our objective was to use weighable lysimeters to meas...Information on cotton evapotranspiration (ET) during the seedling growth stage and under field conditions is scarce because ET is a difficult parameter to measure. Our objective was to use weighable lysimeters to measure daily values of cotton seedling ET. We designed and built plastic weighable micro-lysimeters (ML) that were 0.35 m deep with a soil volume of 6300 cm3. The soil core was obtained in-situ by pushing the ML well casing into the soil using a commercial soil sampler. The soil core was weighed with tension and compression type load-cells, where a change in mass of 18 g·d-1 was equivalent to a water evaporation of 1 mm·d-1. We compared load-cell measurements of changes in mass to values measured with a portable field scale by linear regression analysis, and the slope was equal to 1, indicating no statistical difference (P = 0.05) between the two measurements. We measured and compared seedling height, root length and leaf area of cotton plants in the ML with cotton plants in the surrounding area and this comparison showed that the ML used was suitable to measure cotton seedling ET for the first 30 days after seed emergence. The root mean squared error for crop height was 0.09 cm, for leaf area index (LAI) was 0.03 m2·m-2 and 6.5 cm for root length. Also, soil temperature at a 0.1 m depth was statistically (P = 0.05) the same in and outside the ML’s. For two planting dates, we measured daily values of soil water evaporation (E) and cotton seedling ET. The day following an irrigation event, E was ~ 9 mm d-1 and quickly declined the following days. Results showed that ML’s provide an accurate tool to measure water losses from the soil and cotton plants with a LAI of ≤0.2.展开更多
The ratio of transpiration to evapotranspiration (T/ET) is a key parameter for quantifying water use efficiency of ecosystems and understanding the interaction between ecosystem carbon uptake and water cycling in the ...The ratio of transpiration to evapotranspiration (T/ET) is a key parameter for quantifying water use efficiency of ecosystems and understanding the interaction between ecosystem carbon uptake and water cycling in the context of global change.The estimation of T/ET has been paid increasing attention from the scientific community in recent years globally.In this paper,we used the Priestly-Taylor Jet Propulsion Laboratory Model (PT-JPL) driven by regional remote sensing data and gridded meteorological data,to simulate the T/ET in forest ecosystems along the North-South Transect of East China (NSTEC) during 2001-2010,and to analyze the spatial distribution and temporal variation of T/ET,as well as the factors influencing the variation in T/ET.The results showed that:(1) The PT-JPL model is suitable for the simulation of evapotranspiration and its components of forest ecosystems in Eastern China,and has relatively good stability and reliability.(2) Spatial distribution of T/ET in forest ecosystems along NSTEC was heterogeneous,i.e.,T/ET was higher in the north and lower in the south,with an averaged value of 0.69;and the inter-annual variation of T/ET showed a significantly increasing trend,with an increment of 0.007/yr (p<0.01).(3) Seasonal and inter- annual variations of T/ET had different dominant factors.Temperature and EVI can explain around 90%(p<0.01) of the seasonal variation in T/ET,while the inter-annual variation in T/ET was mainly controlled by EVI (53%,p<0.05).展开更多
The impact of the interannual variability (IAV) of vegetation on the IAV of evapotranspiration is investigated with the Community Land Model (CLM3.0) and modified Dynamic Global Vegetation Model (DGVM). Two sets of 50...The impact of the interannual variability (IAV) of vegetation on the IAV of evapotranspiration is investigated with the Community Land Model (CLM3.0) and modified Dynamic Global Vegetation Model (DGVM). Two sets of 50-year off-line simulations are used in this study. The simulations begin with the same initial surface-water and heat states and are driven by the same atmospheric forcing data. The vegetation exhibits interannual variability in one simulation but not in the other simulation. However, the climatological means for the vegetation are the same. The IAV of the 50-year annual total evapotranspiration and its three partitions (ground evaporation, canopy evaporation, and transpiration) are analyzed. The global distribution of the evapotranspiration IAV and the statistics of evapotranspiration and its components in different ecosystems show that the IAV of ground evaporation is generally large in areas dominated by grass and deciduous trees, whereas the IAV of canopy evaporation and transpiration is large in areas dominated by bare soil and shrubs. For ground evaporation, canopy evaporation, and transpiration, the changes in IAV are larger than the mean state over most grasslands and shrublands. The study of two sites with the same IAV in the leaf area index (LAI) shows that the component with the smaller contribution to the total evapotranspiration is more sensitive to the IAV of vegetation. The IAV of the three components of evapotranspiration increases with the IAV of the fractional coverage (FC) and the LAI. The ground evaporation IAV shows the greatest increase, whereas the canopy evaporation shows the smallest increase.展开更多
[ Objective] The paper presents the diumal changes of photosynthesis and transpiration of different alfalfa varieties and their relationship with the associated physiological and ecological factors during branching st...[ Objective] The paper presents the diumal changes of photosynthesis and transpiration of different alfalfa varieties and their relationship with the associated physiological and ecological factors during branching stage, so as to provide a basis for the development, utilization, and breed- ing of alfalfa. [ Method] Under natural conditions, the diurnal changes of net photosynthetic rate （Pn）, transpiration rate （Tr）, the relevant physio- logical factors including leaf temperature （TI）, stomatal conductance （Gs） and intemal COn concentration （Ci）, as well as the relevant physiologi- cal factors including photosynthetic available radiation （PAR）, CO2 concentration in field （Ca） and air temperature （Ta） were measured in four al- falfa varieties （Algonguin, WL323 HQ, WL414, and Millionaire）. The water use efficiency （WUE） and light use efficiency （LUE） were calculated, and the correlation among them was also analyzed. [Result] The Pn, Tr, PAR and Ta of the four varieties appeared to vary in a single-peak curve; the sequence of WUE was WL323 HQ ~ Algonguin ~ WL414 ~ Millionaire; there was no significant difference in LUE of the four alfalfa varieties; coef- ficient analysis showed that Pn was mainly affected by PAR, Gs, and Ci, while Tr by PAR and Ta. [ Conclusion] WL323 HQ is the variety with high Pn, high WUE and low Tr, and it has strong adaptability to drought. In four alfalfa varieties, PAR, Ta, Gs, and TI are the primary determining fac- tors while Ca and Ci the limiting factors of Tr; Gs is the primary determining factor while Ci the limiting factor of Pn.展开更多
The response of Kousa dogwood （Cornus kousa Buerg.） to extreme stresses was investigated by RGB image analysis in the hot, dry and windy summer in 2007 in Yamaguch, Japan. Results show that tip and margin leaf scorc...The response of Kousa dogwood （Cornus kousa Buerg.） to extreme stresses was investigated by RGB image analysis in the hot, dry and windy summer in 2007 in Yamaguch, Japan. Results show that tip and margin leaf scorch was observed on many Kousa dogwood trees and clearly dark brown defense barrier appeared on scorched leaves. The defense barrier withdrew back from distal to proximal gradually until successful control of scorching, and left a series of unsuccessful defense traces. By responsive analysis of leaf color homogeneity with RGB image analysis method, a sharp logistic equation was obtained for the relative green/luminance （RGL） value of scorched leaves. By the meteorological analysis, the occurrence of dogwood leaf scorch-back was almost synchronous with the aridity peak period. It sug- gested that during the sudden aridity increment the extreme water stresses induce the defense response of Kousa dogwood tree to shear the excessive transpiration leaf area, and prevent the rest of the trees from further water loss. Image pixet analysis showed that 40.2% leaf area of sampled dogwood trees was reduced through the partial leaf scorch-back by the end of August in 2007. In contrast, only 13.2% leaf area was reduced from the same trees in 2008, for the reason of sufficient precipitation during first half year. In any case, the Kousa dogwood trees indeed reduced their transpiration surface area and appeared a surface reduction pattern differing from those shedding leaves or withering all the aboveground. Based on desiccation process analysis, it is considered that the interaction of the leaf dried back and the self-defense response was the key of the transpiration surface reduction （TSR） of Kousa dogwood during sudden hot and droughty stresses.展开更多
The transpiration characteristics of the tamarind artificial forest in the arid-hot valleys of Jinshajiang River, Yunnan were investigated through the measurement of the transpiration rate, stomatal conductance of tam...The transpiration characteristics of the tamarind artificial forest in the arid-hot valleys of Jinshajiang River, Yunnan were investigated through the measurement of the transpiration rate, stomatal conductance of tamarind leaf and the related envi- ronmental factors. The results showed that the transpiration of the tamarind in the clear sky had the close positive correlations with photosynthetically active radiation and air temperature and negative correlation with atmosphere moisture in the whole growth period. The daily change tendency of the transpiration rate was the similar with stomatal conductance, and the transpiration had the positive correlation with stomatal conductance. The transpiration rate of tamarind was highest in the rainy season of June and July and was relatively low in the drought season of March and April. The transpiration water consumption in rainy season of June and July was obviously higher than that in drought season of March and April. It fully suggested that the tamarind showed very good drought resistance and adaptability to the arid-hot valleys of Yunnan .展开更多
Evidence exists of nighttime transpiration and its potential impact on plant/water relations for species in a diversity of ecosystems. However, relevant data related to typical desert riparian forest species remains l...Evidence exists of nighttime transpiration and its potential impact on plant/water relations for species in a diversity of ecosystems. However, relevant data related to typical desert riparian forest species remains limited Accordingly, we measured sap flow velocity of Populus euphratica using the heat ratio method between 2012 and2014. Nocturnal stem sap flow was separated into nighttime and stem refilling using the ‘‘forecasted refilling''method. Nighttime transpiration was observed for each phenophase. The highest value was during the full foliation period but lowest during leaf expansion and defoliation periods. The contribution of nighttime transpiration to daytime transpiration was an average of 15% but this was comparatively higher during the defoliation period. Relationships between nighttime transpiration, vapor pressure deficits, and air temperatures were more closely associated than with wind speed in all phenophases. Moreover, we found that nighttime transpiration linearly correlated to vapour pressure deficit during the first and the full foliation periods, but nighttime transpiration showed exponential correlations to air temperatures during the same phenophases. Additionally, environmental drivers of transpiration were significantly different between nighttime and daytime(P \ 0.05). Driving forces behind nighttime transpiration were characterized by many factors, and integrated impacts between these multiple environmental factors were complex. Future studies should focus on these integrated impacts on nighttime transpiration, and the physiological mechanisms of nighttime transpiration should be investigated, given that this could also influence its occurrence and magnitude during different phenophases.展开更多
Transpiration cooling technique is a reusable and high-efficiency thermal protection system(TPS),which is potential to improve the reusability and security of re-entry space vehicle.Relatively low density,high permeab...Transpiration cooling technique is a reusable and high-efficiency thermal protection system(TPS),which is potential to improve the reusability and security of re-entry space vehicle.Relatively low density,high permeability and high porosity are general requirements for porous media of transpiration cooling systems.In this work,a new porous high entropy metal hexaboride(Y0.2Yb0.2Sm0.2Nd0.2Eu0.2)B6 is designed and prepared by the in-situ reaction/partial sintering method.Two reaction routes are designed to synthesize(Y0.2Yb0.2Sm0.2Nd0.2Eu0.2)B6,including boron thermal reduction and borocarbon thermal reduction.The as-prepared porous HE(Y0.2Yb0.2Sm0.2Nd0.2Eu0.2)B6 ceramics possess homogeneous microstructure and exhibit low density,high porosity,high compressive strength and high permeability.The combination of these properties makes porous HE(Y0.2Yb0.2Sm0.2Nd0.2Eu0.2)B6 promising as a candidate porous media for various transpiration cooling applications.展开更多
基金supported by National Natural Science Foundation of China through Grant Nos.52495000,52332012 and 52176093partially supported by Beijing Huiyangdao Health Technology Co.,Ltd。
文摘Bionic microfluidics is garnering increasing attention due to the superior fluidic performance enabled by biomimetic microstructures.Inspired by the unique structures of young pumpkin stems,we fabricate helicoidally patterned microchannels with precisely controlled morphologies using the projection micro-stereolithography(PμSL)-based 3D printing technique.Our helicoidally patterned microchannels achieve approximately twice the liquid lifting height compared to similarly sized smooth microchannels.This improvement is attributed to the enhanced capillary force.The additional meniscus formed between the helicoidally patterned microstructures significantly contributes to the increased capillary effects.Furthermore,the underlying mechanisms of fluidic performance in helicoidally patterned microchannels are theorized using a newly developed equation,which is also employed to optimize the geometric parameters and fluidic performance of the biomimetic helicoidal microchannels.Additionally,our biomimetic helicoidally patterned microchannels facilitate a significant step-lifting phenomenon,mimicking tall trees'transpiration.The fluidic performance of our biomimetic helicoidally patterned microchannels show promise for applications in enhanced liquid lifting,step-lifting,clean-water production,and others.
基金supported by the National Key Research&Development Project of China(No.2022YFF1300403)the National Natural Science Foundation of China(Nos.U21A2011,41971129,and 32401663)the Open Fund of the State Key Laboratory of Loess Science(No.SKLLQG2423).
文摘Soil water content(SWC)and meteorological conditions,as key environmental variables influencing tree water use,vary highly within the growing season,hindering a better understanding of environmental control mechanisms on canopy transpiration(Ec).Disentangling the effects of these variables on Ec across growing-season stages is crucial for Ec estimation and forest management.In this study,43-year-old Pinus tabuliformis Carr.and 31-yearold Platycladus orientalis(L.)Franco plantations in the semiarid Chinese Loess Plateau were monitored for Ec during the growing season of 2015-2020.The contributions of environmental factors to Ec were assessed using the boosted regression tree(BRT)model.Results showed that the contributions of SWC to Ec were greater at the early(May-June)and late(September)stages,while the contributions of vapor pressure deficit(VPD)and total solar radiation(Rs)to Ec increased at the middle(July-August)stage due to high soil water availability.Overall,Ec in both plantations was dominated by SWC(20.4%≤contributions≤48.8%)and Rs(22.7%≤contributions≤35.8%).Both species exhibited strong stomatal regulation of Ec.Specifically,stomatal opening was significantly inhibited by VPD at the early stage and strongly affected by SWC at the late stage.This study highlights that soil water conditions in artificial forests should be adjusted according to changes in influencing factors on Ec.Particularly during the early and late stages,measures(e.g.,land preparation,thinning,and pruning)can be implemented to improve soil moisture in such dryland forests.
基金financially supported by the National Natural Science Foundation of China(42071047,41771035)the Basic Research Innovation Group Project of Gansu Province(22JR5RA129)the Excellent Doctoral Program in Gansu Province(24JRRA152).
文摘Evapotranspiration is the most important expenditure item in the water balance of terrestrial ecosystems,and accurate evapotranspiration modeling is of great significance for hydrological,ecological,agricultural,and water resource management.Artificial forests are an important means of vegetation restoration in the western Loess Plateau,and accurate estimates of their evapotranspiration are essential to the management and development of water use strategies for artificial forests.This study estimated the soil moisture and evapotranspiration based on the HYDRUS-1D model for the artificial Platycladus orientalis(L.)Franco forest in western mountains of Loess Plateau,China from 20 April to 31 October,2023.Moreover,the influence factors were identified by combining the correlation coefficient method and the principal component analysis(PCA)method.The results showed that HYDRUS-1D model had strong applicability in portraying hydrological processes in this area and revealed soil water surplus from 20 April to 31 October,2023.The soil water accumulation was 49.64 mm;the potential evapotranspiration(ET_(p))was 809.67 mm,which was divided into potential evaporation(E_(p);95.07 mm)and potential transpiration(T_(p);714.60 mm);and the actual evapotranspiration(ET_(a))was 580.27 mm,which was divided into actual evaporation(E_(a);68.27 mm)and actual transpiration(T_(a);512.00 mm).From April to October 2023,the ET_(p),E_(p),T_(p),ET_(a),E_(a),and T_(a) first increased and then decreased on both monthly and daily scales,exhibiting a single-peak type trend.The average ratio of T_(a)/ET_(a) was 0.88,signifying that evapotranspiration mainly stemmed from transpiration in this area.The ratio of ET_(a)/ET_(p) was 0.72,indicating that this artificial forest suffered from obvious drought stress.The ET_(p) was significantly positively correlated with ET_(a),and the R^(2) values on the monthly and daily scales were 0.9696 and 0.9635(P<0.05),respectively.Furthermore,ET_(a) was significantly positively correlated with temperature,solar radiation,and wind speed,and negatively correlated with relative humidity and precipitation(P<0.05);and temperature exhibited the highest correlation with ET_(a).Thus,ET_(p) and temperature were the decisive contributors to ET_(a) in this area.The findings provide an effective method for simulating regional evapotranspiration and theoretical reference for water management of artificial forests,and deepen understanding of effects of each influence factors on ET_(a) in arid areas.
基金Funding Open Access funding enabled and organized by Projekt DEAL.Financial support has been provided by the German Research Foundation(Deutsche Forschungsgemeinschaft-DFG)in the framework of the Sonderforschungsbereich Transregio 40.
文摘Transpiration cooling is numerically investigated,where a cooling gas is injected through a carbon composite material into a hot gas channel.To account for microscale effects at the injection interface,an effective problem is derived.Here,effects induced by microscale structures on macroscale variables,e.g.,cooling efficiency,are taken into account without resolving the microscale structures.For this purpose,effective boundary conditions at the interface between hot gas and porous medium flow are derived using an upscaling strategy.Numerical simulations in 2D with effective boundary conditions are compared to uniform and non-uniform injection.The computations confirm that the effective model provides a more efficient and accurate approximation of the cooling efficiency than the uniform injection.
基金supported by the National Key Research and Development Program of China(2022YFD2001005)the Key Research&Development Program of Jiangsu province(BE2021358)+2 种基金the National Natural Science Foundation of China(32271989)the Natural Science Foundation of Jiangsu province(BK20220146)the Jiangsu Independent Innovation Fund Project of Agricultural Science and Technology[CX(23)3121].
文摘Accurate nitrogen(N)nutrition diagnosis is essential for improving N use efficiency in crop production.The widely used critical N(Nc)dilution curve traditionally depends solely on agronomic variables,neglecting crop water status.With three-year field experiments with winter wheat,encompassing two irrigation levels(rainfed and irrigation at jointing and anthesis)and three N levels(0,180,and 270 kg ha1),this study aims to establish a novel approach for determining the Nc dilution curve based on crop cumulative transpiration(T),providing a comprehensive analysis of the interaction between N and water availability.The Nc curves derived from both crop dry matter(DM)and T demonstrated N concentration dilution under different conditions with different parameters.The equation Nc=6.43T0.24 established a consistent relationship across varying irrigation regimes.Independent test results indicated that the nitrogen nutrition index(NNI),calculated from this curve,effectively identifies and quantifies the two sources of N deficiency:insufficient N supply in the soil and insufficient soil water concentration leading to decreased N availability for root absorption.Additionally,the NNI calculated from the Nc-DM and Nc-T curves exhibited a strong negative correlation with accumulated N deficit(Nand)and a positive correlation with relative grain yield(RGY).The NNI derived from the Nc-T curve outperformed the NNI derived from the Nc-DM curve concerning its relationship with Nand and RGY,as indicated by larger R2 values and smaller AIC.The novel Nc curve based on T serves as an effective diagnostic tool for assessing winter wheat N status,predicting grain yield,and optimizing N fertilizer management across varying irrigation conditions.These findings would provide new insights and methods to improve the simulations of water-N interaction relationship in crop growth models.
文摘Photosynthesis ( P n ), transpiration ( E ) and water use efficiency ( WUE ) of more than 66 arid sand species from different environmental habitats, shifting sand dune, fixed sand dune, lowland and wetland in the Maowusu Sand Area were analyzed and the relation among these characteristics and the resource utilization efficiency, taxonomic categories and growth forms of the species were assessed. The results showed that species from Chenopodiaceae, Gramineae, Leguminosae which possessed the C 4 photosynthesis pathway, or C 3 pathway and also with nitrogen_fixation capacities had higher or the highest P n values, i.e., 20～30 μmol CO 2·m -2 ·s -1 , while that of evergreen shrub of Pinaceae had the lowest P n values, i.e., 0～5 μmol CO 2·m -2 ·s -1 . Those species from Compositae, Scrophulariaceae, and Gramineae with C 3 pathway but no N_fixation capacity had the highest E rates, i.e., 20～30 mmol H 2O·m -2 ·s -1 and again the evergreen shrub together with some species from Salicaceae and Compositae had the lowest E rates, i.e., 0～5 mmol H 2O·m -2 ·s -1 . Species from Leguminosae, Gramineae and Chenopodiaceae with C 4 pathway or C 3 pathway with N_fixation capacity, both shrubs and grasses, generally had higher WUE . However, even the physiological traits of the same species were habitat_ and season_specific. The values of both P n and E in late summer were much higher than those in early summer, with average increases of 26%, 40% respectively in the four habitats. WUE in late summer was, however, 12% lower. Generally, when the environments became drier as a result of habitats changed, i.e., in the order of wetland, lowland, fixed sand dune and shifting sand dune, P n and E decreased but WUE increased.
文摘Transpiration element is included in the integrated stomatal conductance photosynthesis model by considering gaseous transfer processes, so the present model is capable to simulate the influence of boundary layer conductance. Leuning in his revised Ball's model replaced relative humidity with VPD s (the vapor pressure deficit from stomatal pore to leaf surface) and thereby made the relation with transpiration more straightforward, and made it possible for the regulation of transpiration and the influence of boundary layer conductance to be integrated into the combined model. If the differences in water vapor and CO 2 concentration between leaf and ambient air are considered, VPD s , the evaporative demand, is influenced by stomatal and boundary layer conductance. The physiological responses of photosynthesis, transpiration, and stomatal function, and the changes of intercellular CO 2 and water use efficiency to environmental factors, such as wind speed, photon flux density, leaf temperature and ambient CO 2, are analyzed. It is shown that if the boundary layer conductance drops to a level comparable with stomatal conductance, the results of simulation by the model presented here differ significantly from those by the previous model, and, in some cases, are more realistic than the latter.
基金SupportedbytheNationalNaturalScienceFoundationofChina(39970 6 2 2 )andtheTeachingandResearchAwardProgramforYongCadremanTeachersinHigherEducationInstitutionsofMOE P .R .China
文摘To know the annual water consumption of forest, it is necessary to acquire the annual transpiration value of stands. This paper is based on the data measured in the typical weather of the growth season, from 1998 to 2000, with the LI 1600 Steady Porometer and the general weather information. The daily variation of transpiration in black locust forest ( Robinia pesudoacacia L.) is modeled by Penman Monteith equation. As a result of the model, a continuous daily transpiration in the growth season was calculated. The net radiation, intercepted by black locust forest canopy, was acquired from a semi empirical equation of measuring net radiation R n with the extinction coefficient k and leaf area index LAI . The canopy integral stomatic resistance is a mimesis with an empirical equation of measuring data. Compared with measuring data, the relative error of the modeled ones is less than 12% averagely. At last, the total transpiration of black locust forest during the period of 1998 and 2000 in the growth season of May to October, as an average transpiration of the different density stands, were 192 46, 187 07 and 195 59?mm respectively.
文摘We tested the transpiration rate ( Tr ) of seven\|year\|old field and two\|year\|old potted Malus pumila cv.Goldspur under different conditions of illumination and soil water. The results showed that the interrelationship between Tr of Malus pumila cv.Goldspur and illumination and soil water content ( SWC ) was quite remarkable. Tr increased with the increase of light intensity and SWC . However, when one of the environmental stresses of illumination and water existed, the improvement of the other condition couldn't make Tr rise greatly. Only when SWC was higher than 11%, which arrived at over 55% of the field content ( FC ), or the photosynthetic active radiation ( PAR ) higher than 400?μmol·s -1 m -2 , Tr could rise greatly with the increase of PAR or SWC . But when SWC was higher than 15%, which reached over 75% of FC or PAR higher than 1?000?μmol·s -1 ·m -2 , Tr would not change a lot with the change of PAR or SWC . That PAR and SWC influenced the magnitude of stomatic resistance( RS ) and leaf water potential ( Ψ l) was the basic reason for the Tr responded to them. Light stress reduced the open degree of stomas, so when severe light stress existed ( PAR <100?μmol·s -1 ·m -2 ), RS was larger ( RS >2 0?s·cm -1 ), which led to the decrease of Tr(Tr <5?μgH 2O·s -1 ·cm -2 ). When severe water stress existed( SWC <11% and<55% of FC and soil water potential Ψ ws <-1 15?MPa), RS was higher than 4 00?s·cm -1 and Ψ l lower than -2 10?MPa, which led to Tr lower than 11?μgH 2O·s -1 ·cm -2 . When soil water was adequate( SWC >15% amd over 75% of FC , and Ψ ws >-0 50?MPa), RS was lower than 2 00?s·cm -1 , Ψ l higher than -1 65?MPa and Tr would be higher than 15?μgH 2O·s -1 ·m -2 . The range of SWC , 11%～15%, which accounted for 55% to 75% of FC , and correspond RS (2 00～4 00?s·cm -1 ) were the turning area, where the variable curve of Tr transited from a variable trend to another variable one. It could be considered as the range to control soil water.
基金This research was jointly funded by the"Strategic Priority Research Program"of the Chinese Academy of Sciences(XDA2006020102)the Second Tibetan Plateau Scientific Expedition and Research Program(2019QZKK0201)+1 种基金National Natural Science Foundation of China(41801047,41701082),the China Postdoctoral Science Foundation funded project(2018M631589)the Open Research Fund Program of State Key Laboratory of Cryospheric Science,Northwest Institute of Eco-Environment and Resources,CAS(SKLCS-OP-2020-11).
文摘Land surface actual evapotranspiration is an important process that influences the Earth's energy and water cycles and determines the water and heat transfer in the soil-vegetation-atmosphere system.Meanwhile,the cryosphere's hydrological process is receiving extensive attention,and its water problem needs to be understood from multiple perspectives.As the main part of the Chinese cryosphere,the Tibetan Plateau faces significant climate and environmental change.There are active interaction and pronounced feedback between the environment and ETa in the cryosphere.This article mainly focuses on the research progress of ETa in the Tibetan Plateau.It first reviews the ETa process,characteristics,and impact factors of typical underlying surfaces in the Tibetan Plateau(alpine meadows,alpine steppes,alpine wetlands,alpine forests,lakes).Then it compares the temporal and spatial variations of ETa at different scales.In addition,considering the current greening of cryosphere vegetation due to climate change,it discusses the relationship between vegetation greening and transpiration to help clarify how vegetation activities are related to the regional water cycle and surface energy budget.
文摘Information on cotton evapotranspiration (ET) during the seedling growth stage and under field conditions is scarce because ET is a difficult parameter to measure. Our objective was to use weighable lysimeters to measure daily values of cotton seedling ET. We designed and built plastic weighable micro-lysimeters (ML) that were 0.35 m deep with a soil volume of 6300 cm3. The soil core was obtained in-situ by pushing the ML well casing into the soil using a commercial soil sampler. The soil core was weighed with tension and compression type load-cells, where a change in mass of 18 g·d-1 was equivalent to a water evaporation of 1 mm·d-1. We compared load-cell measurements of changes in mass to values measured with a portable field scale by linear regression analysis, and the slope was equal to 1, indicating no statistical difference (P = 0.05) between the two measurements. We measured and compared seedling height, root length and leaf area of cotton plants in the ML with cotton plants in the surrounding area and this comparison showed that the ML used was suitable to measure cotton seedling ET for the first 30 days after seed emergence. The root mean squared error for crop height was 0.09 cm, for leaf area index (LAI) was 0.03 m2·m-2 and 6.5 cm for root length. Also, soil temperature at a 0.1 m depth was statistically (P = 0.05) the same in and outside the ML’s. For two planting dates, we measured daily values of soil water evaporation (E) and cotton seedling ET. The day following an irrigation event, E was ~ 9 mm d-1 and quickly declined the following days. Results showed that ML’s provide an accurate tool to measure water losses from the soil and cotton plants with a LAI of ≤0.2.
基金National Key Research and Development Program of China,No.2015CB954102National Natural Science Foundation of China,No.31700417,No.41571424
文摘The ratio of transpiration to evapotranspiration (T/ET) is a key parameter for quantifying water use efficiency of ecosystems and understanding the interaction between ecosystem carbon uptake and water cycling in the context of global change.The estimation of T/ET has been paid increasing attention from the scientific community in recent years globally.In this paper,we used the Priestly-Taylor Jet Propulsion Laboratory Model (PT-JPL) driven by regional remote sensing data and gridded meteorological data,to simulate the T/ET in forest ecosystems along the North-South Transect of East China (NSTEC) during 2001-2010,and to analyze the spatial distribution and temporal variation of T/ET,as well as the factors influencing the variation in T/ET.The results showed that:(1) The PT-JPL model is suitable for the simulation of evapotranspiration and its components of forest ecosystems in Eastern China,and has relatively good stability and reliability.(2) Spatial distribution of T/ET in forest ecosystems along NSTEC was heterogeneous,i.e.,T/ET was higher in the north and lower in the south,with an averaged value of 0.69;and the inter-annual variation of T/ET showed a significantly increasing trend,with an increment of 0.007/yr (p<0.01).(3) Seasonal and inter- annual variations of T/ET had different dominant factors.Temperature and EVI can explain around 90%(p<0.01) of the seasonal variation in T/ET,while the inter-annual variation in T/ET was mainly controlled by EVI (53%,p<0.05).
基金supported by the National Basic Research Program of China (973 Program, Grant No. 2009CB421406)the National High Technology Research and Development Program of China (863 Program, Grant No. 2009AA122100)
文摘The impact of the interannual variability (IAV) of vegetation on the IAV of evapotranspiration is investigated with the Community Land Model (CLM3.0) and modified Dynamic Global Vegetation Model (DGVM). Two sets of 50-year off-line simulations are used in this study. The simulations begin with the same initial surface-water and heat states and are driven by the same atmospheric forcing data. The vegetation exhibits interannual variability in one simulation but not in the other simulation. However, the climatological means for the vegetation are the same. The IAV of the 50-year annual total evapotranspiration and its three partitions (ground evaporation, canopy evaporation, and transpiration) are analyzed. The global distribution of the evapotranspiration IAV and the statistics of evapotranspiration and its components in different ecosystems show that the IAV of ground evaporation is generally large in areas dominated by grass and deciduous trees, whereas the IAV of canopy evaporation and transpiration is large in areas dominated by bare soil and shrubs. For ground evaporation, canopy evaporation, and transpiration, the changes in IAV are larger than the mean state over most grasslands and shrublands. The study of two sites with the same IAV in the leaf area index (LAI) shows that the component with the smaller contribution to the total evapotranspiration is more sensitive to the IAV of vegetation. The IAV of the three components of evapotranspiration increases with the IAV of the fractional coverage (FC) and the LAI. The ground evaporation IAV shows the greatest increase, whereas the canopy evaporation shows the smallest increase.
文摘[ Objective] The paper presents the diumal changes of photosynthesis and transpiration of different alfalfa varieties and their relationship with the associated physiological and ecological factors during branching stage, so as to provide a basis for the development, utilization, and breed- ing of alfalfa. [ Method] Under natural conditions, the diurnal changes of net photosynthetic rate （Pn）, transpiration rate （Tr）, the relevant physio- logical factors including leaf temperature （TI）, stomatal conductance （Gs） and intemal COn concentration （Ci）, as well as the relevant physiologi- cal factors including photosynthetic available radiation （PAR）, CO2 concentration in field （Ca） and air temperature （Ta） were measured in four al- falfa varieties （Algonguin, WL323 HQ, WL414, and Millionaire）. The water use efficiency （WUE） and light use efficiency （LUE） were calculated, and the correlation among them was also analyzed. [Result] The Pn, Tr, PAR and Ta of the four varieties appeared to vary in a single-peak curve; the sequence of WUE was WL323 HQ ~ Algonguin ~ WL414 ~ Millionaire; there was no significant difference in LUE of the four alfalfa varieties; coef- ficient analysis showed that Pn was mainly affected by PAR, Gs, and Ci, while Tr by PAR and Ta. [ Conclusion] WL323 HQ is the variety with high Pn, high WUE and low Tr, and it has strong adaptability to drought. In four alfalfa varieties, PAR, Ta, Gs, and TI are the primary determining fac- tors while Ca and Ci the limiting factors of Tr; Gs is the primary determining factor while Ci the limiting factor of Pn.
文摘The response of Kousa dogwood （Cornus kousa Buerg.） to extreme stresses was investigated by RGB image analysis in the hot, dry and windy summer in 2007 in Yamaguch, Japan. Results show that tip and margin leaf scorch was observed on many Kousa dogwood trees and clearly dark brown defense barrier appeared on scorched leaves. The defense barrier withdrew back from distal to proximal gradually until successful control of scorching, and left a series of unsuccessful defense traces. By responsive analysis of leaf color homogeneity with RGB image analysis method, a sharp logistic equation was obtained for the relative green/luminance （RGL） value of scorched leaves. By the meteorological analysis, the occurrence of dogwood leaf scorch-back was almost synchronous with the aridity peak period. It sug- gested that during the sudden aridity increment the extreme water stresses induce the defense response of Kousa dogwood tree to shear the excessive transpiration leaf area, and prevent the rest of the trees from further water loss. Image pixet analysis showed that 40.2% leaf area of sampled dogwood trees was reduced through the partial leaf scorch-back by the end of August in 2007. In contrast, only 13.2% leaf area was reduced from the same trees in 2008, for the reason of sufficient precipitation during first half year. In any case, the Kousa dogwood trees indeed reduced their transpiration surface area and appeared a surface reduction pattern differing from those shedding leaves or withering all the aboveground. Based on desiccation process analysis, it is considered that the interaction of the leaf dried back and the self-defense response was the key of the transpiration surface reduction （TSR） of Kousa dogwood during sudden hot and droughty stresses.
基金the National Key Technologies Research and Development Program in the Eleventh Five-Year Plan of China (2006BAC01A11)the Natural Science Foundation of Yunnan Province (2006D0092M, 2007C235M)
文摘The transpiration characteristics of the tamarind artificial forest in the arid-hot valleys of Jinshajiang River, Yunnan were investigated through the measurement of the transpiration rate, stomatal conductance of tamarind leaf and the related envi- ronmental factors. The results showed that the transpiration of the tamarind in the clear sky had the close positive correlations with photosynthetically active radiation and air temperature and negative correlation with atmosphere moisture in the whole growth period. The daily change tendency of the transpiration rate was the similar with stomatal conductance, and the transpiration had the positive correlation with stomatal conductance. The transpiration rate of tamarind was highest in the rainy season of June and July and was relatively low in the drought season of March and April. The transpiration water consumption in rainy season of June and July was obviously higher than that in drought season of March and April. It fully suggested that the tamarind showed very good drought resistance and adaptability to the arid-hot valleys of Yunnan .
基金financially supported by the Key Research Program of Frontier Sciences CAS(QYZDJ-SSWDQC031)Key Project of the Chinese Academy of Sciences(KZZDEW-04-05)+1 种基金the National Natural Science Foundation of China(91025024)the ‘‘Western Light’’ project of the Chinese Academy of Science
文摘Evidence exists of nighttime transpiration and its potential impact on plant/water relations for species in a diversity of ecosystems. However, relevant data related to typical desert riparian forest species remains limited Accordingly, we measured sap flow velocity of Populus euphratica using the heat ratio method between 2012 and2014. Nocturnal stem sap flow was separated into nighttime and stem refilling using the ‘‘forecasted refilling''method. Nighttime transpiration was observed for each phenophase. The highest value was during the full foliation period but lowest during leaf expansion and defoliation periods. The contribution of nighttime transpiration to daytime transpiration was an average of 15% but this was comparatively higher during the defoliation period. Relationships between nighttime transpiration, vapor pressure deficits, and air temperatures were more closely associated than with wind speed in all phenophases. Moreover, we found that nighttime transpiration linearly correlated to vapour pressure deficit during the first and the full foliation periods, but nighttime transpiration showed exponential correlations to air temperatures during the same phenophases. Additionally, environmental drivers of transpiration were significantly different between nighttime and daytime(P \ 0.05). Driving forces behind nighttime transpiration were characterized by many factors, and integrated impacts between these multiple environmental factors were complex. Future studies should focus on these integrated impacts on nighttime transpiration, and the physiological mechanisms of nighttime transpiration should be investigated, given that this could also influence its occurrence and magnitude during different phenophases.
基金financial supported by the National Natural Science Foundation of China(Nos.51672064 and U1435206).
文摘Transpiration cooling technique is a reusable and high-efficiency thermal protection system(TPS),which is potential to improve the reusability and security of re-entry space vehicle.Relatively low density,high permeability and high porosity are general requirements for porous media of transpiration cooling systems.In this work,a new porous high entropy metal hexaboride(Y0.2Yb0.2Sm0.2Nd0.2Eu0.2)B6 is designed and prepared by the in-situ reaction/partial sintering method.Two reaction routes are designed to synthesize(Y0.2Yb0.2Sm0.2Nd0.2Eu0.2)B6,including boron thermal reduction and borocarbon thermal reduction.The as-prepared porous HE(Y0.2Yb0.2Sm0.2Nd0.2Eu0.2)B6 ceramics possess homogeneous microstructure and exhibit low density,high porosity,high compressive strength and high permeability.The combination of these properties makes porous HE(Y0.2Yb0.2Sm0.2Nd0.2Eu0.2)B6 promising as a candidate porous media for various transpiration cooling applications.
