Single-peak Curve Research Articles

Effects of Drought Stress on Key Enzymes of Carbon Metabolism, Photosynthetic Characteristics and Agronomic Traits of Soybean at the Flowering Stage under Different Soil Substrates

Soybean is an important legume food crop, and its seeds are rich in nutrients, providing humans and animals with edible oil and protein feed. However, soybean is sensitive to water requirements, and drought is an important factor limiting soybean yield and quality. This study used Heinong 84 (drought resistant variety) and Hefeng 46 (intermediate variety) as tested varieties planted in chernozem, albic, and black soils. The effects of drought stress on the activities of key enzymes in carbon metabolism and photosynthetic characteristics of soybean were studied during the flowering stage, most sensitive to water. (1) The activities of SS-1, 6PGDH, and G6PDH enzymes in soybean leaves first increased and then decreased under drought stress. The enzyme activity was the highest under moderate drought stress and weakest in the blank group. (2) Drought stress increased Phi2, PhiNO, and Fm in soybean leaves and reached the highest value under severe drought; with the increase in drought stress, PhiNPQ and Fv/Fm of soybean leaves gradually decreased, reaching the lowest under severe drought. (3) With the increase in drought stress, F0 and Fs of soybean leaves showed a single peak curve, and the maximum was at moderate drought. (4) Correlation analysis showed that F0 was greatly affected by varieties and soil types; Fs, F0, and Fm soil varieties had a great influence, and chlorophyll fluorescence parameters were affected differently under drought stress with different drought degrees. (5) Drought stress changed the agronomic traits and yield of soybean. With the increase of drought degree, plant height, node number of main stem, effective pod number, 100-seed weight and total yield decreased continuously. (6) Drought stress affected the dry matter accumulation of soybean. With the increase of drought degree, the dry matter accumulation gradually decreased. Among them, the leaf was most seriously affected by drought, and SD decreased by about 55% compared with CK. Under the condition of black soil, the dry matter accumulation of soybean was least affected by drought.

亚热带岩溶区典型常绿和落叶树种的蒸腾特征及其对环境因子的响应

植物蒸腾是水循环的重要组成部分，为了解亚热带岩溶区树木的蒸腾耗水情况，探究气候和水文地质条件对植物蒸腾的影响，运用Granier热耗散探针技术，对亚热带岩溶区次生林内的常绿树种女贞（L.lucidum）和落叶树种刺槐（R.pseudoacacia）的树干液流进行了连续监测，并同步监测了气象因子及土壤含水率（SMC），探讨在不同时间尺度下两种生活型树种的蒸腾特征及其对环境因子的响应。结果表明：（1）在季节尺度下，影响两树种整树蒸腾量（ET）的主要因子为太阳辐射强度（Rs）、气温（T）和水汽压亏缺（VPD）；女贞蒸腾量（ET_L）表现为夏季（1.29 kg/h） > 春季（0.57 kg/h） > 冬季（0.15 kg/h） > 秋季（0.13 kg/h），刺槐蒸腾量（ET_R）表现为夏季（0.90 kg/h） > 春季（0.31 kg/h） > 秋季（0.16 kg/h） > 冬季（0.04 kg/h）。（2）在日尺度下，晴天两树种ET呈现出明显的单峰日变化，且主要影响因子均为T、VPD和Rs；但由于常绿和落叶树种的生理特征差异，降雨时ET_L受到抑制，而ET_R则显著提升。（3）从昼夜层面来看，两树种夜间蒸腾量不足日蒸腾总量的35%。在夜雨现象和树木生理特征的影响下，秋冬季夜间蒸腾量占比明显高于春夏季，刺槐的平均夜间蒸腾量及其占比（1.56 kg，24.1%）高于女贞（1.08 kg，13.9%）。;Plant transpiration is an important part of water cycle in ecosystem, that is, the process of water transfer from soil to atmosphere through plants. It is driven by solar radiation, air temperature, air humidity and wind speed, and also affected by soil water storage capacity. Understanding and quantifying the influence mechanism of transpiration is an important basis to explore the water consumption of vegetation and the water balance of ecosystem. However, although the climate conditions in the subtropical karst area are good, there is a drought period of 4-5 months. At the same time, plants are often affected by water stress because of the thin soil layer and low water holding capacity of soil in karst area. The study of plant transpiration characteristics helps us understand the water consumption of trees in subtropical karst areas, and is also of great significance for exploring the impact of climate and hydro-geological conditions on plant transpiration. Granier's thermal dissipation probe method was used to continuously monitor the trunk sap flow of the evergreen tree species (L.lucidum) and the deciduous tree species (R.pseudoacacia) in the secondary forest in the subtropical karst area. The meteorological factors and soil moisture content (SMC) are also monitored simultaneously. Our purpose is to analyze the transpiration characteristics of two life-form tree species and their responses to environmental factors on different time scales. The results show that:(1) at the seasonal scale, the main factors affecting the whole-tree transpiration (ET) are solar radiation intensity (Rs), air temperature (T) and vapor pressure deficiency (VPD). The transpiration of L.lucidum (ET_L) is shown as summer (1.29 kg/h) > spring (0.57 kg/h) > winter (0.15 kg/h) > autumn (0.13 kg/h), transpiration of R.pseudoacacia (ET_R) is shown as summer (0.90 kg/h) > spring (0.31 kg/h) > autumn (0.16 kg/h) > winter (0.04 kg/h). (2) On the daily scale, the ET of the two tree species shown obvious single peak curve on sunny day, and the main factors affecting transpiration are T, VPD and Rs. However, due to the differences in the physiological characteristics of evergreen and deciduous tree species, ET_L is weakened during rainfall, while ET_R is significantly increased. (3) in terms of day and night, the nocturnal transpiration of the two tree species accounts for less than 35% of the total daily transpiration on average. Affected by the phenomenon of night precipitation and the physiological characteristics of trees, the proportion of nocturnal transpiration in the autumn and winter is significantly higher than that in the spring and summer. At the same time, the average daily nocturnal transpiration and its proportion of R.pseudoacacia (1.56 kg, 24.1%) is higher than that of L.lucidum (1.08 kg, 13.9%).

高寒草甸生态系统降雨事件对不同深度土壤碳释放的试验分析

PDF HTML阅读 XML下载 导出引用 引用提醒 高寒草甸生态系统降雨事件对不同深度土壤碳释放的试验分析 DOI: 10.5846/stxb202010312791 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金重点项目（41730854） Experimental analysis of soil carbon release at different depths by rainfall events in alpine meadow ecosystem Author: Affiliation: Fund Project: National Natural Science Foundation of China (41730854) 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:以青藏高原高寒草甸生态系统为研究对象，基于LI-8150土壤CO2通量全自动连续测量系统及实验设计，对不同深度的土壤碳释放进行了连续原位观测，分析了晴天和5次持续性降水条件下不同深度土壤碳释放特征，结合土壤温湿度的观测，解析了降雨对不同深度土壤碳释放的影响及机理。结果表明：（1）在0 cm、20 cm、40 cm、70 cm深度处，土壤碳释放均呈现明显的单峰曲线变化特征，其日均值（±标准差）分别为（3.96±0.89）μmol m-2 s-1、（5.09±1.79）μmol m-2 s-1、（7.83±1.95）μmol m-2 s-1和（4.43±1.6）μmol m-2 s-1。（2）降雨提高了土壤含水量，显著抑制了土壤碳释放，且对深层的抑制作用显著大于表层。其中，第5次持续性降水事件对土壤水分的补充作用最明显（增量最大），其对土壤碳释放的抑制作用也更显著，并出现负通量（即碳吸收）。随着土壤深度的增加，观测到碳吸收现象愈加显著。（3）不同深度土壤碳释放与土壤温度、水分呈指数或二次曲线相关关系。晴天条件下，土壤含水量较稳定，土壤温度是影响各层土壤碳释放的主导因子；而降雨条件下，土壤含水量变化显著，土壤水分成为主导土壤碳释放的关键因子，并对其可能产生的机理进行了讨论。 Abstract:This study selected Qinghai-Tibet Plateau alpine meadow ecosystem as the research object. Based on the Li-8150 automated soil CO2 flux system, continuous in-situ observation of soil carbon release at different depths was carried out, and the characteristics of soil carbon release at different depths in sunny and 5 times of continuous rain events were analyzed. Combined with the observation of soil temperature and soil moisture, the effects of rainfall on soil carbon release at different depths and possible mechanisms were analyzed. The results showed that, (1) The soil respiration at 0 cm, 20 cm, 40 cm, and 70 cm all showed obvious single-peak curve, and their daily average soil respiration (±standard deviation) were (3.96±0.89) μmol m-2 s-1, (5.09±1.79) μmol m-2 s-1, (7.83±1.95) μmol m-2 s-1 and (4.43±1.6) μmol m-2 s-1. (2) Rainfall significantly increased soil moisture, and inhibited soil carbon release, and the inhibition effects of deep layer was significantly greater than that of surface layer. Among them, the fifth persistent rain event had the most obvious supplementary effect on soil moisture (the largest increment), and its inhibitory effect on soil carbon release was also more significant, even negative flux (i.e., carbon sequestration) appeared in the deep layer. With the increase of soil depth, carbon absorption was observed to be more significant. (3) The relationship between soil carbon release at different depths and soil temperature or soil moisture was correlated with the exponential correlation or quadratic curve. Under sunny conditions, the soil moisture is stable, and the soil temperature is the dominate factor to affect the surface soil respiration. While under rainfall days, soil moisture changed significantly, and became the control of soil carbon release, and its possible mechanism was discussed. 参考文献 相似文献 引证文献

Microstructure and flow behaviour of a quenching and partitioning steel at elevated temperatures

ABSTRACT Hot compression tests were carried out on a quench and partitioning steel in the temperature range of 850-1050 °C and strain rates of 10-3- 1 s-1. The single-peak flow curves were appeared at high strain rates and low temperatures and the multi-peaks at the opposite condition. It was found that the mechanism of dynamic recrystallization (DRX) changes by passing from 950 °C due to dynamic precipitation of carbide particles. The microstructural characterizations using optical microscopy and electron back scattered diffraction (EBSD) techniques revealed various mechanisms of DRX in different deformation conditions. EBSD results showed opposite variations of high and low angle grain boundaries with increasing deformation temperature and decreasing strain rate. By using the hyperbolic sine constitutive equation, the value of apparent activation energy at the typical strain of 0.5 was determined as 297.67 kJ/mol.

Quantitative assessment of renal perfusion in children with UPJO by contrast enhanced ultrasound: A pilot study

Contrast-enhanced ultrasound (CEUS) is a new potential modality for the quantitative evaluation of the microvascular perfusion of a parenchymal organ. To prospectively and quantitatively analyse the role of CEUS in evaluating renal perfusion for assessing renal function in children with ureteropelvic junction obstruction (UPJO). The study protocol was approved by the local ethics committee, and written informed consent was obtained from the patients' parents or guardians. Ultrasonography, CEUS, and radioisotope renography were performed for 51 children (42 boys, 9 girls; mean age, 6.75±4.14 years) with unilateral UPJO. The slope of the ascending curve (A), time to peak (TTP), peak intensity (PI), and area under the curve (AUC) were recorded during CEUS; quantitative data were calculated by QLab system (semiautomated border tracking, Philips Healthcare) software. Sensitivity and specificity values were determined for CEUS with respect to radioisotope renography. CEUS was used to evaluate 102 kidneys in 51 patients, for which the perfusion time-intensity curve (TIC) was determined. The TIC of renal cortical perfusion in all groups showed an asymmetrical single-peak curve, which could be clearly distinguished between the experimental group and the control group. Compared with the control group, the experimental group showed a markedly prolonged TTP but a significantly decreased A (P<0.05). There was no significant correlation between the AUC, PI and differential renal function (DRF), but the correlation coefficient between TTP, A and DRF remained significant (p<0.001).The receiver operating characteristic (ROC) curves drawn to differentiate DRF using the TTP value yielded an area under the ROC curve (AUROC) of 0.86. For a quantitative assessment of DRF less than 40% by CEUS, the sensitivity and specificity values were 92.86% and 76.14%, respectively. Unlike in previous studies, no significant difference in the AUC or PI was found between the control group and the experimental group in this study (P>0.05). Renal blood perfusion could not be evaluated overall by CEUS. Parenchymal thinning may be considered a limitation to CEUS. This preliminary experience represents the first report of evaluating the diagnostic value of CEUS in assessing renal function in children with UPJO. CEUS is a highly sensitive, rapid, and cost-effective diagnostic imaging modality for detecting and monitoring renal function noninvasively.

Effects of drought stress on antioxidant enzymes in common bean (Phaseolus vulgaris L.) seedlings

Drought is one of the most severe environmental constraints which reduces common bean production worldwide. Exploration of the physiological mechanism of common bean under drought stress is important for the efficient production and variety selection of common beans. In the present study, non-droughtresistant variety (Longyundou10) and drought-resistant variety (Longyundou17) were identified to elucidate the effects of drought stress on antioxidant system of common beans at seedling stage. Under drought stress, APX and SOD activities showed a single peak curve that first increased and then decreased, and the dynamic changes of CAT and POD activities were more complicated. Under different levels of drought treatment, the average values of APX, SOD, CAT and POD activities of common bean were found to be higher than those of normal water conditions, and the average values were the highest under severe drought stress, indicating that these antioxidant enzymes were stimulated under drought stress. Bangladesh J. Bot. 50(3): 873-878, 2021 (September) Special

Development and evaluation of cement/emulsified-asphalt based piezoelectric sensors for road weigh-in-motion system

Piezoelectric composites (PCs) have great potential in traffic information perception. In this study, 2–2 cement/emulsified asphalt PCs were prepared by the cutting-filling method, and a set of preparation technology was formed. The finite element model of PC and road structure was established to simulate the loading process of moving load, and the influence of embedded PCs on road structure was further discussed. In addition, the effects of the buried depth and offset distance of PCs on the mechanical electrical effect were studied. The results indicated that the buried depth had a little effect on the mechanical electrical effect of PCs, and this effect would be amplified when the load was close to the buried position: the shallower the PCs were buried, the greater the output voltage. When the load was in the direct-acting zone, the voltage output curve was a multi-peak curve, and the attenuation of the voltage peak with the offset distance was small; when the load was in the indirect-acting zone, the output curve was a single peak curve, and the output voltage decayed rapidly with the increase of the offset distance. It was found that the load level was linearly related to the voltage peak value, and the high-precision axle load detection could be achieved by embedding PCs in the road, so as to realize the weigh-in-motion of the road.

Energy flux observation in a shrub ecosystem of a gully region of the Chinese Loess Plateau

Flux observations are important for understanding the basic processes of carbon and water cycling in an ecosystem. In 2020 (1 January 2020 to 31 December 2020), we continuously monitored the surface energy fluxes of a shrub ecosystem using an eddy covariance system. Additionally, meteorological variables, such as temperature and rainfall, were measured. The study site was located in Chunhua of China, which is a gully region of the Chinese Loess Plateau. The diurnal and seasonal dynamic changes in the energy balance of this region were analysed, Bowen and energy balance ratios were calculated, and environmental factors affecting the variations in latent (LE) and sensible heat fluxes (H) were explored. The results showed that the annual net radiation (Rn), LE, H, and soil heat flux (G) were 2385.6, 1059.1, 787.6, and - 48.3 MJ/m2, respectively, with 490.58 MJ/m2 energy remaining undetected. The main part of the annual energy of the shrub ecosystem was latent heat, accounting for 44.4% of Rn. A seasonal variation in each energy component was evident, and the diurnal variation showed a single peak curve. LE in the growing season was dominant, and the proportion of LE and H in the net radiation in the non-growing season showed little difference. The Bowen ratio changed monthly and significantly fluctuated from 0.2 in July to 4.0 in December. It was high in winter and low in summer, with little fluctuation. The annual energy balance ratio was 0.8. The energy balance closure in the non-growing season was greater than that in the growing season. Both H and LE were significantly correlated with net radiation, and H was negatively correlated with rainfall, soil moisture, and soil temperature. Unlike H, LE was significantly positively correlated with soil temperature. In addition, LE was positively correlated with air humidity gradient and water vapour pressure difference.

Spatial distribution and associations of dead woods in natural spruce-fir secondary forests

To reveal the community succession rule of natural secondary forest, we investigated basic characteristics and coordinates of each tree (DBH≥1 cm) within a plot (100 m×100 m) using the adjacent grid method and examined the distribution pattern and spatial associations of dead woods in a natural spruce-fir secondary forest in Jingouling Forest Farm, Wangqing Forestry Bureau, Jilin Province, China. The results showed that the diameter class distribution of dead woods showed the pattern of left single-peak curve, while the logs showed the pattern of multi-peak curve. The relationship between the abundance of dead woods and the standing individuals of a particular species was inconsistent. There was a significant negative exponential relationship between the number of dead woods and mixing degree of trees. The distribution of dead woods was concentrated at the 0-8 m scale. With the increases of scale, it gradually changed to random or uniform, with the random distribution being dominant. The aggregation distribution of dead woods with middle (10 cm≤DBH＜20 cm) and small (1 cm≤DBH＜10 cm) DBH was the main reason for the aggregation distribution of dead woods at small scale below 8 m. The spatial associations between dead woods and stan-ding trees at different diameter classes were significantly different. The relationship between dead woods and saplings (1 cm≤DBH＜5 cm) was closely correlated. The dead woods with large DBH and saplings showed a significant positive association at 2-25 m scale. There was no spatial association between dead woods and small trees (5 cm≤DBH＜15 cm). At the 0-3 m scale, there was a positive association between the middle trees (15 cm≤DBH＜25 cm) and dead woods of small and middle DBH. At the 9, 11-14 and 15, 42-45 m scales, dead woods of small and middle DBH were significantly negatively associated with large trees (DBH≥25 cm). In conclusion, biological traits, diameter class distribution, and spatial distribution affected the abundance and diameter class distribution of dead woods. The species with low mixing degree tended to have more dead woods. The diameter and scale would affect the spatial distribution of dead woods. The spatial correlation between dead woods and standing trees varied across diameter classes and scales.

Analysis of Subgrade Vibration and Dynamic Stress of Heavy Haul Railway with High Embankment based on ZL-TNTLM Program

Aiming at the high embankment section of heavy-load Railway, a finite element model of dynamic response of subgrade structure under train load is established, and ZL-TNTLM program is used to apply load excitation. The results show that the dynamic stress on the top of the roadbed is a single peak curve under heavy train load, and the peak value of the vertical acceleration vibration changes obviously under heavy train load, and presents a periodic change With the increase of the train speed, the dynamic pressure stress of the track bed and the foundation bed does not increase obviously with the increase of the train speed, but fluctuates and changes slowly; the dynamic stress and the vertical acceleration in the roadbed attenuate non-linearly along the depth direction The attenuation of acceleration is greater than dynamic stress along the direction of subgrade depth. The results are of theoretical and engineering significance for revealing the dynamic stress and vertical acceleration mechanism of heavy-haul railway subgrade under the change of high-speed train speed.

N and P addition increase soil respiration but decrease contribution of heterotrophic respiration in semiarid grassland

Fertilization is an effective measure to decrease soil erosion by promoting vegetation restoration, while it affects soil respiration (Rs) greatly through influencing soil properties and plant root growth. A factorial combination of N addition (0, 50 and 100 kg N ha-1 yr-1 defined as N0, N50, and N100) and P addition (0, 40 and 80 kg P2O5 ha-1 yr-1 defined as P0, P40, and P80) experiment was conducted in a farming-withdrawn grassland to investigate the Rs and its components (heterotrophic respiration, Rh; autotrophic respiration, Ra) in responses to different nitrogen (N) and phosphorus (P) addition levels from May 2018 to October 2019 on the semiarid Loess Plateau. Results showed that Rs, Rh and Ra presented single-peak curves both in diurnal and seasonal variations across all N and P addition treatments. The highest Rs, Rh and Ra values during the day occurred at 12:00–14:00 and the highest values during the year appeared in July, which were consistent with soil temperature changes. Rs, Rh and Ra increased significantly under N and/or P addition from May to September. Compared with no fertilization, Rh and Ra significantly increased by 4.2–5.1% and 43.9–46.4%, and by 13.2–15.8% and 23.0–34.2% under N or P addition alone, respectively. N and P combined addition increased Rh and Ra by 25.4–30.7% and 62.0–111.4% than N or P addition alone. Rs and Ra reached the highest values under N100 combined with P80 addition, but Rh reached the highest values under N50 combined with P80 addition treatment. Annual cumulative CO2 emission increased by 24.4%−26.5% under N addition alone, 17.0–27.4% under P addition alone and 42.2–68.7% under N and P combined addition. Compared with no fertilization, root biomass and soil microbial biomass carbon significantly increased by 15.8–122% and 5.2–92.5% after N and P additions, respectively. However, the positive effect of N and P addition on Rh was weaker than that of Ra, which decreased the contribution of Rh to Rs. Our findings point to the need of rational N and P combination to tradeoff biomass production improvement and soil carbon emission when applying fertilization to promote grassland restoration in semiarid Loess Plateau.

Application of the Beta Probability Density Function for Representing Infiltration of Water-Repellent Soil

Laboratory experiments were conducted to investigate the infiltration of water-repellent soil. The most suitable mathematical model to represent infiltration of water-repellent soil was investigated and water infiltration into this column was measured for both hydrophilic and water-repellent soils of the Guishui River Basin. The results showed a monotonous increase and decrease in cumulative infiltration and infiltration rate over time within the hydrophilic soil, respectively. In contrast, the results for water-repellent soil showed: (1) The existence of a turning point in cumulative infiltration above which the infiltration rate increased sharply, with higher initial soil moisture content resulting in an earlier and larger increase in the infiltration rate; (2) A larger stable infiltration rate after the peak compared to that before the peak, with the overall infiltration rate presenting a single peak curve if the beginning of rapid infiltration is ignored. The applicability of the Kostiakov, segmented Kostiakov, Gaussian, segmented Gaussian, Beta and segmented Beta function infiltration models were analysed for the two soil types. The numerical analysis indicated that: (3) The Kostiakov and Beta function models showed better applicability for both hydrophilic and water-repellent soils; (4) For water-repellent soil, the Gaussian function infiltration model not only represented the monotonous decrease in infiltration rate, but also demonstrated a steady infiltration rate during the initial stage and a gradual increase and decrease in infiltration rate pre- and post-peak, respectively. Similarly, the Beta function model was able to represent the monotonous decrease in infiltration rate, and the segmented Beta function represented the U-shaped change in rapid infiltration before the threshold as well as the gradual increase and right-skewed distribution curve of infiltration pre- and post-turning point in water-repellent soil. The Beta function model achieved the highest simulation accuracy and showed the widest applicability.

Relationships between diurnal and seasonal variation of photosynthetic characteristics of Eucalyptus plantation and environmental factors under dry-season irrigation with fertilization

Eucalyptus is widely planted in South China and has high economic and ecological values. However, the seasonal drought in southern China severely limits the productivity of Eucalyptus plantation. In this study, the dry-season irrigation was carried out after the conventional production and planting of Eucalyptus. The diurnal changes of photosynthetic characteristics of Eucalyptus plantations were measured in July, October 2017 and January, May 2018 to explore the diurnal and seasonal variations and their responses to both dry-season irrigation and environmental factors. The results showed that during the first-year growth of Eucalyptus urophylla × E. grandis plantation, (1) the diurnal changes of the trees under different treatments showed single-peak curves with the varied occurrence time of the highest photosynthetic characteristics in different months; the E. urophylla × E. grandis without dry-season irrigation (CK and F) had transpiration midday depression in January and that with the only dry-season irrigation (W) exhibited both photosynthetic and transpiration midday depression in May. (2) The trees of CK and F were subjected to mild drought stress in the dry season and their maximum photosynthetic and transpiration rate were lower than those of W and WF treatment respectively, but they had higher maximum WUE. The trees of W had significantly higher daily net CO2 assimilation and daily water transpiration in dry season. (3) The diurnal changes of photosynthetic characteristics were mainly influenced by water vapor pressure deficit (VPD) at the corresponding time of the month. (4) In the short-term treatments, dry-season irrigation and fertilization significantly increased the biomass of E. urophylla × E. grandis. Dry-season irrigation alleviated the mild drought stress for gas exchange in the dry season and further promote the biomass of E. urophylla × E. grandis. This study provided an important practical exploration for improving the productivity of E. urophylla × E. grandis plantation in seasonal arid areas.

Statistical characteristics and risk zoning of different duration heavy rainfall in Shanxi

Based on different duration heavy rainfall data and the associated disaster situation, geographic information, socio-economic characteristics, river network density, and geological hazard-prone zoning of 109 stations in Shanxi Province in the past 38 years, a statistical analysis of different duration heavy rainfall events in Shanxi Province was carried out. In addition, a comprehensive risk zoning was performed using hierarchy analysis and weighted comprehensive evaluation methods. The results show that: (1) the spatial distribution of the extreme value indicates the following: the mountain area is larger than that of the basin, and the south is greater than the north and has a shorter time-effect and a stronger local distribution of the extreme value. Yuanqu County (YuanQ) has the highest concentration area of all different duration heavy rainfall events within 12 h. (2) Within 12 h., the occurrence frequency of different duration heavy rainfall has the spatial distribution characteristics of being higher in the south and lower in the north, higher in the mountain area than in the basin area, higher in the eastern mountain area than in the western mountain area, and obviously concentrated in the southeast. YuanQ is a high incidence area of short-duration heavy rainfall over 1 h. and 3 h., and Jincheng City (JinC) is a high incidence area of heavy rainfall over 6 h and 12 h.. (3) Severe precipitation with different durations occurs in July–August every year, and the frequency of hourly heavy rainfall is the highest. (4) The intra-day distributions of heavy rainfall over a period of 1 h., 3 h., and 12 h. are single-peak curves, with peaks at 18:00, 19:00 and 09:00, respectively; the intra-day distribution of heavy rainfall over 6 h. is a double peak curve, with peaks at 06:00 and 20:00. (5) The variation trend of the annual occurrence times of short-duration heavy precipitation is similar for 1 h, 3 h, and 6 h, and the growth rate is the highest in southeastern Shanxi Province. The variation trend of the occurrence times of heavy rainfall over 12-h. is different from that of 1-h., 3-h., and 6-h. short-duration heavy rainfall. The rate of growth is the largest in the eastern and western mountain areas of Shanxi Province. (6) The whole area of JinC, the east of Yuncheng City (YunC), and the southeast of Changzhi City (CZ) are the high-risk areas for all different duration heavy precipitation disaster-causing factors within 12 h. As the duration of heavy rainfall increases, the high-risk areas with respect to disaster factors in Linfen City (LF) and CZ increase. (7) JinC, YunC, and Liulin County (LL) are high-risk areas for the comprehensive risk of different duration heavy rainfall within 12 h, and LF and CZ districts increase the extent of high-risk areas with the increase in the duration of heavy precipitation.

Dynamics of the soil respiration response to soil reclamation in a coastal wetland

The soil carbon (C) pools in coastal wetlands are known as “blue C” and have been damaged extensively owing to climate change and land reclamation. Because soil respiration (RS) is the primary mechanism through which soil carbon is released into the atmosphere at a global scale, investigating the dynamic characteristics of the soil respiration rate in reclaimed coastal wetlands is necessary to understand its important role in maintaining the global C cycle. In the present study, seasonal and diurnal changes in soil respiration were monitored in one bare wetland (CK) and two reclaimed wetlands (CT, a cotton monoculture pattern, and WM, a wheat–maize continuous cropping pattern) in the Yellow River Delta. At the diurnal scale, the RS at the three study sites displayed single-peak curves, with the lowest values occurring at midnight (00:00 a.m.) and the highest values occurring at midday (12:00 a.m.). At the seasonal scale, the mean diurnal RS of the CK, CT and WM in April was 0.24, 0.26 and 0.79 μmol CO2 m−2 s−1, and it increased to a peak in August for these areas. Bare wetland conversion to croplands significantly elevated the soil organic carbon (SOC) pool. The magnitude of the RS was significantly different at the three sites, and the yearly total amounts of CO2 efflux were 375, 513 and 944 g CO2·m−2 for the CK, CT and WM, respectively. At the three study sites, the surface soil temperature had a significant and positive relationship to the RS at both the diurnal and seasonal scales, and it accounted for 20–52% of the seasonal variation in the daytime RS. The soil water content showed a significant but negative relationship to the RS on diurnal scale only at the CK site, while it significantly increased with the RS on seasonal scale at all study sites. Although the RS showed a noticeable relationship to the combination of soil temperature and water content, the synergic effects of these two environment factors were not much higher than the individual effects. In addition, the correlation analysis showed that the RS was also influenced by the soil physico-chemical properties and that the soil total nitrogen had a closer positive relationship to the RS than the other nutrients, indicating that the soil nitrogen content plays a more important role in promoting carbon loss.

Optimizing biochar application to improve soil physical and hydraulic properties in saline-alkali soils

Biochar application has been a promising approach to improve soil quality but their optimal amount in improving physical and hydraulic properties remains contradictory and inconclusive. The objective of this study was to examine and propose an optimal biochar application amount in saline alkali soil considering their impact on soil physical and hydraulic properties. A three-year field experiment was conducted in the saline-alkali soils under plastic film-mulched drip irrigation in Xinjiang, China. The studied physical and hydraulic properties included bulk density, soil porosity, saturated soil water content (θs), permanent wilting point (PWP), field capacity (FC), plant available water (PAW), spatial distribution of soil water content, planar soil water storage (PSWS), and soil evaporation. The treatments included biochar application amounts of 0 (CK), 10 (B10), 50 (B50), and 100 t ha−1 (B100) in 2018. Additional two treatments with 25 t ha−1 (B25) and 30 t ha−1 (B30) were added in 2019 and 2020, respectively. A four-parameter Gaussian function was fitted to the single-peak curves of the studied hydraulic properties vs. biochar application amounts to determine the most optimal biochar application amount. The results indicated that: (1) All of the biochar treatments significantly decreased bulk density and increased soil porosity over CK; (2) B10 and B25 treatments significantly increased θs, FC, PAW, PWP, and PSWS of root zones in the film-mulched zones over CK, but reverse results were observed in the B50 and B100 treatments; (3) Daily and cumulative soil evaporation were increased in no mulch zones of all biochar treatments over CK; (4) A dose of 21.9 t ha−1 was recommended as the most optimal biochar application amount for improving physical and hydraulic properties of saline-alkali soil. This research provided useful information on biochar application amounts for improving physical and hydraulic properties in saline-alkali soil.

Cooling load characteristic and uncertainty analysis of a hub airport terminal

The airport terminal is a multi-region public transport building with special functions and the cooling load is a basic parameter determining the air-conditioning system for this special building. The large uncertainty in the parameters of the terminal cooling load calculation will affect the input data, which will lead to the uncertainty of the model results. In this paper, the load of a typical hub airport terminal is simulated and calculated on the basis of uncertainty analysis, and the sensitivity analysis of the influencing factors is carried out. The result shows that compared with the given parameters, more accurate average probability distribution and peak load distribution of terminal cooling load can be obtained under uncertainty parameters. The average load of the terminal is in the range of 55.2–78.5 W/m2 within the 95% confidence interval, and the peak load is in the range of 79.8–117.9 W/m2 within the 95% confidence interval. Load curves of various areas in the terminal are clustered. The results show that there are two main types of areas, i.e. one exhibits a single-peak curve and the other exhibits a peak-flat curve, which demonstrate the load characteristics of different zones. The sensitivity analysis shows that the most performance influencing factors are indoor temperature and humidity set point.

Measuring and modeling evapotranspiration of a Populus euphratica forest in northwestern China

Vegetation is sparsely distributed in the arid regions of northwestern China, and accurately measuring and partitioning of evapotranspiration is of importance for ecosystems in such areas. In this study, we measured and analyzed diurnal and phenological variations in evapotranspiration using the eddy–covariance method based on the Penman–Monteith, Priestley–Taylor, Shuttleworth–Wallace models, a newly proposed improved dual source model and a clumped model in a forest reserve in the Ejin oasis of Populus euphratica in 2015 and 2016 growing seasons. A sensitivity analysis was performed for the models with higher accuracies and we examined the biotic and abiotic controls on evapotranspiration. The results show that the total amounts of evapotranspiration during the two growing seasons in 2015 and 2016 were 622 and 612 mm, respectively. Phenological variations in evapotranspiration produced single-peak curves, while diurnal variations reflected the influence of high temperatures on some afternoons. The Priestley–Taylor and the improved dual source models gave the most accurate evapotranspiration values at the daily scale and appeared to be most suitable for the estimation of evapotranspiration for the species in arid regions. In addition, both models were the most sensitive to net radiation (Rn).

Spatiotemporal variation of reference evapotranspiration in Shanxi Province, China

Based on data of daily precipitation, temperature, sunshine hours, relative humidity, wind speed and vapor pressure of 70 meteorological stations from 1960 to 2019 in Shanxi Province, the Penman-Monteith model was applied to calculate the reference evapotranspiration (ET0). The spatiotemporal variations of ET0 as well as the ET0 in different climatic zones and at different altitudes were quantitatively analyzed. The results showed that the mean annual ET0 decreased from west to east in 1960-2019. A jumping point was detected in 1982, with the mean annual ET0 increased both in 1960-1982 and 1983-2019. The monthly and ten-day changes of ET0 showed single peak curves. The variation of ET0 in different climatic zones was as follows: ET0 in temperate and semi-arid areas was higher than that in warm temperate and semi-humid areas and warm temperate and semi-arid areas in spring, summer, autumn and the whole year, while in winter, the highest ET0 was in warm temperate and semi-humid areas. ET0 varied with altitudes, with ET0 in <660 m altitude areas being higher than that in other altitudes in summer, autumn, winter and the whole year.

Ecological stoichiometry and biomass responses of Agropyron michnoi under simulated N deposition in a sandy grassland, China

Sandy grassland in northern China is a fragile ecosystem with poor soil fertility. Exploring how plant species regulate growth and nutrient absorption under the background of nitrogen (N) deposition is crucial for the management of the sandy grassland ecosystem. We carried out a field experiment with six N levels in the Hulunbuir Sandy Land of China from 2014 to 2016 and explored the Agropyron michnoi Roshev. responses of both aboveground and belowground biomasses and carbon (C), N and phosphorus (P) concentrations in the plant tissues and soil. With increasing N addition, both aboveground and belowground biomasses and C, N and P concentrations in the plant tissues increased and exhibited a single-peak curve. C:N and C:P ratios of the plant tissues first decreased but then increased, while the trend for the N:P ratio was opposite. The peak values of aboveground biomass, belowground biomass and C concentration in the plant tissues occurred at the level of 20 g N/(m2·a), while those of the N and P concentrations in the plant tissues occurred at the level of 15 g N/(m2·a). The maximum growth percentages of aboveground and belowground biomasses were 324.2% and 75.9%, respectively, and the root to shoot ratio (RSR) decreased with the addition of N. N and P concentrations in the plant tissues were ranked in the order of leaves>roots>stems, while C concentration was ranked as roots>leaves>stems. The increase in N concentration in the plant tissues was the largest (from 34% to 162%), followed by the increase in P (from 10% to 33%) and C (from 8% to 24%) concentrations. The aboveground biomass was positively and linearly correlated with leaf C, N and P, and soil C and N concentrations, while the belowground biomass was positively and linearly correlated with leaf N and soil C concentrations. These results showed that the accumulation of N and P in the leaves caused the increase in the aboveground biomass, while the accumulation of leaf N resulted in the increase in the belowground biomass. N deposition can alter the allocation of C, N and P stoichiometry in the plant tissues and has a high potential for increasing plant biomass, which is conducive to the restoration of sandy grassland.