Relative Soil Water Research Articles

Characterizing the hysteretic effects of water and salinity stresses on root-water-uptake

Characterizing the effects of previous water and salinity stresses is critical for the evaluation of plant water status, which, in turn, is essential for understanding soil-plant water relations and optimizing irrigation schemes. Recent research has found that hysteresis of plant response following water stress alone can be described by an exponential function of the stress degree on the previous day. To explore and quantify the effects of hysteresis concerning salinity stress and combined water-salinity stress, a hydroponic experiment and a soil column experiment on winter wheat, and a field experiment on cotton were conducted. Like water stress, previous salinity stress and combined water-salinity stress also resulted in hysteretic effects on root-water-uptake. Leaf stomatal conductance and plant transpiration rate of stressed crops could only recover gradually from a previous stressed status after re-watering. When stress was mild, compensatory recovery was found, while incomplete recovery occurred when stress was severe. Although the recovery process was closely related to stress history and type, a recovery coefficient was quantified universally with an exponential function of the stress extent on the previous day (with a coefficient of determination R2 ≥ 0.60). Consideration of hysteresis for water and salinity stresses with a mathematical model led to significant improvement in the simulation of both relative transpiration rate (R2 = 0.94, root mean squared error RMSE = 0.04, maximal absolute error MAE = 0.12) and soil water content (R2 = 0.90, RMSE = 0.01 cm3 cm–3, MAE = 0.03 cm3 cm–3), especially during the recovery periods severely affected by historical stress. Consideration of hysteresis is expected to benefit regulation of soil water and salinity and thus enhance water use efficiency. However, the mechanisms underlying hysteresis, especially the compensatory recovery mechanisms, still need to be further investigated.

Microclimate and the spatio-temporal dynamics of natural production of two ectomycorrhizal fungi from the Guineo-Sudanian ecozone in Benin

The study aims to determine the relation between the micro-climate and the natural production of Amanita subviscosa, and Lactifluus gymnocarpoides, in the Guinea-Sudanian ecozone. Nine permanent plots of 50 ×50 m were installed in three different vegetations of the “Ouémé Supérieur” forest reserve in central Benin. The mycological surveys were carried out during three (3) mycological seasons, each from June to October at a frequency of two visits per week and per plot. The number of fruiting bodies and the fresh biomass were recorded. Microclimatic parameters (soil water content, air temperature, soil temperature, relative humidity and precipitation) were measured using a rain gauge and a HOBO micro station data logger installed at the middle of each plot. We tested several Generalized Linear Mixed Effects Models (GLMM) using the lme4 package to obtain the effect of recorded microclimate factor on the number of fruit bodies of each species and the Linear Mixed Effects Model (LMM) using the package nlme for fresh biomass. The study showed that soil water content is the main driver of fungal fruiting phenology and increased biomass production. The fruiting of A. subviscosa is positively affected by air temperature and soil water content (p = 0.0004) but negatively affected by relative air humidity. The fructification of L. gymnocarpoides is only positively affected by the air temperature and negatively affected by relative air humidity and soil water content. Soil water content significantly affects the fresh biomass of A. subviscosa (p≈0) while the fresh biomass of L. gymnocarpoides is significantly affected by soil water content and relative air humidity (p≈0). All species for their natural production have specific response at microclimate parameters variation.

Effects of phosphorus application rate on distribution of 13C assimilates and spike formation in different til-lers of wheat with supplementary irrigation

To clarify the appropriate rate of phosphorus application and physiological mechanism for promoting wheat tillering and efficient utilization of phosphorus fertilizer with supplementary irrigation, we used 'Jimai 22' wheat variety as the test material, to set up three phosphorus application treatments, including low (90 kg P2O5·hm-2, P1), medium (135 kg P2O5·hm-2, P2), and high (180 kg P2O5·hm-2, P3) application rates, with no phosphorus application as the control (P0). We increased the relative soil water content of each treatment at join-ting stage and anthesis stage to 70%, and measured the area of tiller node, the content of endogenous hormones, the number of tillers in each tiller position, photosynthetic parameters, the distribution of 13C assimilates in each stem and tiller, as well as the grain yield and partial productivity of phosphate fertilizer. The results showed that compared with P0 and P1 treatments, P2 significantly increased the area of tiller node and the trans-zeatin (tZ), the photosynthetic parameters of the uppermost expanded leaves of the main stem, the total tillers per plant, and the distribution of 13C assimilates in each tiller. The number of ears per plant was increased by 0.51 and 0.36, and grain yield was increased by 40.3% and 13.2%, respectively. In P3 treatment, the number of tillers increased, but the panicles per plant, and the grain yield and phosphate fertilizer partial productivity decreased. Our results suggested that the moderate phosphorus treatment (135 kg·hm-2) under supplementary irrigation was suitable for high yield and high efficiency of wheat.

Az évjárat hatása magyar szürke szarvasmarha legelő vegetációjára 2022- és 2023-ban ― Esettanulmány

The "Szűzföld" area, managed by the Pro Vértes Public Foundation, has been managed for nature conservation and economic grazing since 1998 with Hungarian grey cattle. In the present work the vegetation data of the pasture were analysed for the years 2022-2023, in order to investigate the effect of the weather conditions in an extremely dry year (2022) and an extremely wet year (2023) using 2 × 2 m coenological records. To analyse the ecological indicators of species, we used Borhidi's relative plant ecological indicators: relative nitrogen demand (NB) and relative soil water and soil moisture (WB) scores. We also assessed the data according to Simon's conservation value categories (TVK) and Borhidi's social behaviour types (SBT). The grassland management assessment of the vegetation was based on the forage value scores of the species used by Klapp et al. The results showed no significant differences in species in the two years, but significant differences in cover values. In the year with rainfall, the proportion of accompanying species decreased, while the proportion of weeds and natural disturbance tolerant species increased. The amount of grasses and legumes increased, which are important for grassland management.

Különböző gyepkezelések hatásának cönológiai és természetvédelmi vizsgálati eredményei üde gyepen

In grassland management systems, the various agrotechnical elements have to be used in many cases on "primitive grasslands", where the coordination of agricultural and nature conservation tasks is necessary. Here, animal husbandry is the main aspect, which includes the long-term preservation of the quality of the pasture, as well as the most economical use of the pasture and keeping the animals as cheap as possible. The tests were carried out on a grassy area on the border of the settlement of Aba. We examined the vegetation of 8 plots of the same size in the area and the quantitative and qualitative composition of the biomass produced there. In this thesis, we provide data on the vegetation composition and evaluation of the following treatments. The plots and treatments were as follows: I. plot-ventilated; II. parcel-relaxed; III. plot loosened and ventilated; ARC. parcel control; V. plot-ventilated and 15 t/ha manure; VI. plot loosened and 15 t/ha manure; VII. plot loosened, ventilated and 15 t/ha manure; VIII. plot loosened, ventilated and 30 t/ha manure. In each plot, 5 ceenological recordings were made using 4 x 4 m quadrats. The estimated coverage of each species was given in %, taking into account the proportion of grasslands and other species. Among Borhidi's plant ecological indicators, the species were evaluated based on the NB (relative values of nitrogen demand) and WB (relative soil water and soil moisture indicator numbers). The social behavior types (SZMT) were also defined based on Borhidi's work, and the nature conservation value categories (TVK) were defined according to Simon. The lifestyle analysis was performed based on Pignatti's lifestyle types. Based on the data, the composition of the vegetation of each plot changed significantly compared to the data of the control plot IV. A direct proportionality can be discovered between the increase in the cover value of the dominant lawn grasses, primarily Festuca arundinacea, Dactylis glomerata, Alopecurus pratensis, and Fabaeceae species (e.g. Lathyrus tuberosus, Lotus corniculatus) and the amount of applied nutrients. Based on the coenological survey of the eight examined areas, the control area (IV.) showed the most natural state, which was confirmed by the species composition and number of species. The IV. plots are close to I., II. and III. for plot recordings, which proves that aeration and loosening do not worsen the condition of the lawn, but rather promote the preservation of its natural state. The VII-VIII. plots have the smallest number of species, but based on the life form spectrum, naturalness indicators, nature conservation value categories and social behavior types, they are not very disturbed habitats. No significant difference can be detected between the effect of lawn loosening and lawn aeration, but III. plot, where both treatments were carried out, was closer to the control area. Regarding the effect of the lawn management methods, it was possible to produce a starting data set in the long term (with the same environmental conditions). Overall, the study gave valuable results regarding the age of change occurring during the application of different lawn management methods, and was also effective from an economic point of view.

Impacts of re-vegetation on soil water dynamics in a semiarid region of Northwest China

Understanding how vegetation (shrub) cover in drylands affects local-to-regional soil water dynamics and associated water balances is of immense importance because of the abundance of afforestation projects worldwide. Vegetation's role in the control of soil water presents a particular challenge to soil water storage (SWS) management in the drylands of China. To address this knowledge gap, we conducted a two-year study in the Mu Us Desert of northwest China. The study involved the acquisition of in-situ soil water measurements within the first 180 cm of soil at three sand dune sites characterized by their differences in % shrub cover. The sand dunes varied from a vegetation-free, bare-ground sand dune site (BF) and two partly vegetated sites, one with medium-level (40 %) and another with high shrub cover (80 %; MF and HF, respectively). Results revealed that the site with the high shrub cover (HF) suffered a net reduction in soil water content (SWC) by up to 32.7 and 39.8 % in the shallow and deep subsoil (0–100 and 100–180 cm), respectively, when compared to corresponding changes at the BF site. Soil water content was shown to be largely influenced by site properties, namely shrub biomass and litter density (p < 0.05). Due to aboveground vegetation and rainfall interception by the litter, 32.2 mm of effective rainfall was reduced to the soil for every 10 %-increase in shrub cover. Bands of soil water depletion during the dry year did not fully recover during the following wet year, resulting in the development of a dried soil layer with an average SWC of 4.6–7.8 %. Increased evapotranspiration (ETtotal) led to a decrease in SWS and relative extractable soil water (REW), which caused ETtotal at HF to be lower than the rate observed at MF. These findings highlight the need for improvements in current restoration strategies, meant at striking a balance between vegetation restoration and SWC by developing optimal plant-community cover and mosaicked vegetation systems.

Differentiated responses of daytime and nighttime sap flow to soil water deficit in a larch plantation in Northwest China

Tree transpiration contributes to the forest water budget and its environmental responses differ between daytime and nighttime. Elucidating these divergent responses separately from their biophysical controls is crucial for ascertaining the forest-water relationship in changing environments. To investigate the biophysical controls on daytime and nighttime sap flow (Qd and Qn), the sap flux density, meteorological conditions, soil moisture, and canopy leaf area index (LAI) were simultaneously monitored in a Larix principis-rupprechtii plantation in the Liupan Mountains of Northwest China during the growing seasons (June to September) of three hydrological years (2019, 2021, and 2022). The results showed that the main control factors for Qd and Qn varied depending on the timescale. The variation in Qd was mainly controlled by daytime solar radiation (Rd), vapour pressure deficit (VPDd), relative extractable soil water (REWd) and LAI at a daily scale, but only by Rd at a monthly scale and only by VPDd at an interannual scale. The variation in Qn was mainly controlled by the nighttime vapour pressure deficit (VPDn) and relative extractable soil water (REWn), LAI, and Qd at a daily scale but only by VPDn at monthly and interannual scales. The responses of Qd and Qn to soil water deficit were different and varied by timescale. At the daily scale, the effect of VPDd on Qd became weak, while the effect of VPDn on Qn became strong in drier years (2021 and 2022). At the monthly scale, as the main controlling factor of the monthly variation in Qd (Qn), Rd (VPDn) played a decisive role in the wet (dry) months. At the interannual scale, VPD limited Qd but drove Qn, leading to a decrease in Qd and an increase in Qn with increasing soil water deficit. Overall, our findings revealed the different responses of Qd and Qn to biophysical factors and underscored that Qd and Qn should be explored both separately and synchronously; additionally, our results indicated that the proportion of Qn might increase if soil water stress is increased due to future climate change.

The relationship between habitat factors and the nutrient contents of wild Allium victorialis L. in the Changbai Mountains

Allium victorialis L. (Family: Liliaceae) is an herb with nutritional and medicinal properties. In Jilin Province, China, A. victorialis is mainly distributed in the Changbai Mountains and grows in various habitat conditions. However, the relationship between habitat factors and the nutritional quality of A. victorialis in the Changbai Mountains has not yet been examined. We assessed the nutritional quality of five A. victorialis populations growing in five different habitats in the Changbai Mountains and analyzed the relationship between nutritional quality and habitat factors. Allium victorialis populations in this region were primarily found in the undergrowth at elevations above 500 m and within specific ranges of air temperature, air relative humidity, soil temperature, and soil water content. Among the habitat factors investigated, canopy density significantly affected several nutritional components of A. victorialis; however, elevation had a significant effect only on the total flavonoid content, and the vitamin C content was not strongly associated with the main habitat factors in this study. During germplasm selection and artificial cultivation, it is important to simulate the growth conditions of the original habitat. Our results provide useful information for site selection and environmental condition optimization for the artificial cultivation of A. victorialis.

Sand-fixing vegetation regulates deep percolation and soil water dynamics in semiarid sandy land: Evidence from a deep percolation recorder and in-situ test

Deep percolation (DP) determines the sustainable utilization of regional groundwater resources and provides large hydrological benefits to ecosystems in semiarid sandy regions. However, studies involving DP variability have rarely conducted in-situ tests with different vegetation coverages (VC) and vegetation types using direct measurements. This study measured soil moisture and DP for four years in five plots, with DP measured using a deep percolation recorder: mobile sand (MS) as the control group; Artemisia ordosica semifixed (AOSF) with VC of 30%–35% and Artemisia ordosica fixed (AOF) with VC of 70%–75% (AOSF and AOF stand ages: 30–40 years), representing different vegetation coverages; and Salix psammophila fixed (SPF) and Pinus sylvestrix var. Mongolica fixed (PSMF) with the same VC of 45%–50% (SPF and PSMF stand ages: 30 years), representing different vegetation types. The effects of sand-fixing vegetation on DP and soil water were evaluated using the relative extractable soil water (RESW) and soil water storage deficit metrics. DP occurrence in MS was closely related to rainfall amounts of > 10 mm and high-intensity rainfall rather than the total annual rainfall. Increases in vegetation coverages and forest selection significantly reduced DP and RESW compared with MS. DP in the shrub plot (SPF) was significantly higher than that in the forest plot (PSMF). Plants utilized water from different sources among the sandy land types: the shallow (0–80 cm) and deep layers (80–200 cm) in PSMF and AOF, and only from the shallow layer in AOSF and SPF. However, compared with MS, soil water storage deficit occurred to varying degrees in each plot. This study can provide a scientific reference for the restoration of the ecology and water cycle in sandy regions.

Cross-pollination with native genotypes improves fruit set and yield quality of Peruvian cacao

The cacao tree (Theobroma cacao) is a billion-dollar crop species of which the yields are greatly constrained by, amongst others, pollination limitation. Manual pollen supplementation has been proposed to counter pollination deficits, thus improving yield quantity and potentially also quality, as the origin of the pollen can be controlled. In native cacao, low self- and cross-compatibility rates and the interaction with abiotic growth conditions are expected to limit manual pollination benefits. Here we compared supplementation of self-pollen with cross-pollen of five native genotypes selected for their sensorial quality as pollen donors. Simultaneously, we assessed how temperature, relative air humidity and soil water content influenced fruit set and evaluated qualitative differences between pollen-supplemented and open pollinated fruits. Success of manual self-pollination was very low (0.5 %) but increased 3–8-fold in cross-pollination experiments. Cross-pollination success rates depended on the genotype of the pollen donor, irrespective of genetic distance between pollen donor and recipient. Further, seed weight and premium seed content was higher in fruits resulting from pollen-supplemented than from open-pollinated flowers. Fruit set was also affected by the interaction of temperature and relative humidity, but not by soil water content. Together, our findings suggest that reproductive traits of native cacao systems are constrained by genetic compatibility and some abiotic factors. Even though manual pollen supplementation with native genotypes can clearly benefit both fruit quantity and quality, it is labor intensive and hence costly to implement. Natural cross-pollination by planting compatible genotypes selected for sensorial quality could simultaneously avoid high costs and improve fruit quality, potentially resulting in net economic gains for smallholder farmers.

Impact of solar geoengineering on wildfires in the 21st century in CESM2/WACCM6

Abstract. We quantify future changes in wildfire burned area and carbon emissions in the 21st century under four Shared Socioeconomic Pathways (SSPs) scenarios and two SSP5-8.5-based solar geoengineering scenarios with a target surface temperature defined by SSP2-4.5 – solar irradiance reduction (G6solar) and stratospheric sulfate aerosol injections (G6sulfur) – and explore the mechanisms that drive solar geoengineering impacts on fires. This study is based on fully coupled climate–chemistry simulations with simulated occurrence of fires (burned area and carbon emissions) using the Whole Atmosphere Community Climate Model version 6 (WACCM6) as the atmospheric component of the Community Earth System Model version 2 (CESM2). Globally, total wildfire burned area is projected to increase over the 21st century under scenarios without geoengineering and decrease under the two geoengineering scenarios. By the end of the century, the two geoengineering scenarios have lower burned area and fire carbon emissions than not only their base-climate scenario SSP5-8.5 but also the targeted-climate scenario SSP2-4.5. Geoengineering reduces wildfire occurrence by decreasing surface temperature and wind speed and increasing relative humidity and soil water, with the exception of boreal regions where geoengineering increases the occurrence of wildfires due to a decrease in relative humidity and soil water compared with the present day. This leads to a global reduction in burned area and fire carbon emissions by the end of the century relative to their base-climate scenario SSP5-8.5. However, geoengineering also yields reductions in precipitation compared with a warming climate, which offsets some of the fire reduction. Overall, the impacts of the different driving factors are larger on burned area than fire carbon emissions. In general, the stratospheric sulfate aerosol approach has a stronger fire-reducing effect than the solar irradiance reduction approach.

Estimating the effect of water shortage on olive trees by the combination of meteorological and Sentinel-2 data

ABSTRACT Relative soil water content (RSWC) is widely used to characterize the impact of water stress (WS) on vegetation. In bi-layer ecosystems, such as olive groves, this impact must be primarily estimated for the tree component, which, having greater rooting depth, responds more slowly to WS than understory grass. This complicates the application of methods for RSWC prediction, which must be properly adapted to consider the deeper soil layer influential on olive trees. The current study investigates the modification of a recently proposed RSWC simulation method based on a combination of meteorological and satellite-derived normalized difference vegetation index (NDVI) data. The application of the method to an olive grove in Central Italy requires the estimation of both weather and NDVI contributions affecting solely olive trees, which is carried out through the use of appropriate data processing techniques. The RSWC estimates obtained reasonably reproduce the ground RSWC observations referred to the 1 m soil layer, which are representative of the WS affecting olive trees (r2 = 0.795, RMSE = 0.15 and MBE = −0.09). The limits and prospects of this method are finally discussed with particular reference to the possible integration of the RSWC estimates within more complex ecosystem models.

Selected indigenous drought tolerant rhizobium strains as promising biostimulants for common bean in Northern Spain.

Drought is the most detrimental abiotic stress in agriculture, limiting crop growth and yield and, currently, its risk is increasing due to climate change. Thereby, ensuring food security will be one of the greatest challenges of the agriculture in the nearest future, accordingly it is essential to look for sustainable strategies to cope the negative impact of drought on crops. Inoculation of pulses with biostimulants such as rhizobium strains with high nitrogen fixation efficiency and drought-tolerance, has emerged as a promising and sustainable production strategy. However, some commercial inoculums are not effective under field conditions due to its lower effectiveness against indigenous rhizobium strains in the establishment of the symbiosis. Thus, in the present study, we evaluated the ability to improve drought tolerance in common bean plants of different indigenous rhizobia strains isolated from nearby crop fields in the Basque Country either affected by drought or salinity. The plants in this trial were grown in a climatic chamber under controlled conditions and exposed to values of 30% relative soil water content at the time of harvest, which is considered a severe drought. From the nine bacteria strains evaluated, three were found to be highly efficient under drought (namely 353, A12 and A13). These strains sustained high infectiveness (nodulation capacity) and effectiveness (shoot biomass production) under drought, even surpassing the plants inoculated with the CIAT899 reference strain, as well as the chemically N-fertilized plants. The tolerance mechanisms developed by plants inoculated with 353, A12 and A13 strains were a better adjustment of the cell wall elasticity that prevents mechanical damages in the plasma membrane, a higher WUE and an avoidance of the phenological delay caused by drought, developing a greater number of flowers. These results provide the basis for the development of efficient common bean inoculants able to increase the yield of this crop under drought conditions in the Northern Spain and, thus, to be used as biostimulants. In addition, the use of these efficient nitrogen fixation bacteria strains is a sustainable alternative to chemical fertilization, reducing cost and minimizing its negative impact on environment.

Physiological Responses of Chionanthus retusus Seedlings to Drought and Waterlogging Stresses

Understanding the adaptability of Chionanthus retusus Lindl. et Paxt. to extreme water conditions will help in exploring the potential application of this species in barren mountains. Three-year-old Chionanthus retusus seedlings were used in a greenhouse pot experiment that analyzed the effect of different moisture gradients on growth, photosynthetic and fluorescence characteristics, protective enzyme system, osmotic substance regulation and cell membrane damage. The results indicated that C. retusus can effectively grow at a relative soil water content of 44.6% and above and can maintain growth for 20 days under flooded conditions. Under drought stress, net photosynthesis rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), and intercellular carbon dioxide concentration (Ci) all showed a trend of gradual decrease. The trend of change was similar under waterlogging conditions. The maximal quantum yield of PSII photochemistry (Fv/Fm), actual photochemical efficiency of PSII (ΦPSII), photochemical quenching coefficient (qP), and electron transport rate (ETR) all decreased as drought deepened. Malondialdehyde (MDA) content decreased first and then increased. However, superoxide dismutase (SOD) activity content, peroxidase (POD) activity content, and proline (Pro) activity content showed a trend of increasing and then decreasing. C. retusus had good adaptability in the slight drought treatment group and flooded treatment group but showed intolerance in the high drought group, which could still last for approximately 21 days. C. retusus was found to have a strong adaptability to water stress and can be used as an afforestation tree in barren mountains.

不同时间尺度下华北落叶松人工林冠层蒸腾与环境因子的关系

PDF HTML阅读 XML下载 导出引用 引用提醒 不同时间尺度下华北落叶松人工林冠层蒸腾与环境因子的关系 DOI: 10.5846/stxb202107151903 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 内蒙古自治区关键技术攻关计划项目(2021GG0033);内蒙古自治区林业和草原局科研能力提升项目;内蒙古自治区自然科学基金项目(2021MS03101) Relationship between canopy transpiration of larch plantation and environmental factors at different time scales Author: Affiliation: Fund Project: 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:在半干旱区连续2年监测华北落叶松(Larix principis-rupprechtii)的树干液流、气象因子和土壤体积含水量,分析不同时间尺度下人工林冠层蒸腾与环境因子的关系。结果表明:不同时间尺度下,华北落叶松人工林冠层蒸腾的季节变化均呈单峰曲线,即先增大后减小的趋势;2016年、2017年日蒸腾量分别为1.58 mm/d和1.71 mm/d,生长季蒸腾总量分别为241.30 mm和260.97 mm。在日尺度下,气温、太阳辐射强度和饱和水汽压差是影响华北落叶松人工林冠层蒸腾主要环境因子;月尺度下,气温、风速、降水和土壤水分是冠层蒸腾的主要影响因子;冠层蒸腾与降水、大气相对湿度的相关关系由日尺度下的负相关到月尺度的正相关,相关性增强。总体来看,随时间尺度由小到大,气温、风速、大气相对湿度、降水、土壤水分对冠层蒸腾的影响作用增大,而太阳辐射强度、饱和水汽压差的作用减弱;在未来增温增雨趋势下,研究区生长季将延长,华北落叶松人工林冠层蒸腾量可能会加大。 Abstract:Canopy transpiration is a major part of forestland water balance and a fundamental datum in understanding the planted forest ecophysiology in dry regions. Quantitatively analyzing variation of canopy transpiration induced by the environmental factors is beneficial for a better estimation forestland water balance and prediction the plantation ecophysiology. But the response mechanism of canopy transpiration to environmental factors may be different in different time scales, so it needs to be further understood. This study was conducted in a 42-year-old Larix principis-Rupprechtii plantation (a density of 1933 trees/hm2) at the middle position of a north facing slope in the Inner Mongolian Daqingshan National Nature Reserve, a semi-arid region of China. Firstly, the sap flow velocity in ten healthy and dominant Larix principis-Rupprechtii trees, soil volumetric water content and meteorological factors including air temperature, precipitation, solar radiation intensity, air relative humidity and wind speed, were observed during two growing seasons (May 1 to September 30) in 2016 and 2017 which precipitation was 435.00 mm and 348.80 mm, respectively. Then, sap flow velocity values which was measured by the thermal diffusion method, were upscaled to the forest canopy level. Finally, the relationship between canopy transpiration and the environmental factors at different time scales was analyzed. The results showed that the seasonal changes of canopy transpiration showed a single peak curve under the different time scales, that was, the trend of increase first and then decrease. In 2016 and 2017, the average value of daily canopy-level transpiration was 1.58 mm/d and 1.71 mm/d, respectively, and the total transpiration in the growing season was 241.30 mm and 260.97 mm, respectively. On the daily scale, air temperature, solar radiation intensity and saturated vapor pressure deficit markedly affected canopy transpiration. At the monthly scale, air temperature, wind speed, precipitation and soil volumetric water content were the main influencing factors of canopy transpiration. The correlation between transpiration and precipitation and air relative humidity increased from negative correlation on the daily scale to positive correlation on the monthly scale. In general, with time scale from small to large, the effects of air temperature, wind speed, air relative humidity, precipitation and soil water content on canopy transpiration increase, while the effects of solar radiation intensity and saturated vapor pressure deficit decrease. With the trend of increasing temperature and rainfall in the future, the growing season of Larix principis-Rupprechtii in the study area will be prolonged, and the canopy transpiration may increase. 参考文献 相似文献 引证文献

Effects of nitrogen application rate on the accumulation of 13C assimilates after flowering and water-nitrogen use efficiency of wheat under supplemental irrigation based on soil moisture.

This study aimed to explore nitrogen fertilizer management measures to synergistically improve wheat yields and water and nitrogen use efficiency under supplemental irrigation based on soil moisture in the Huang Huai winter wheat area. Wheat variety "Yannong 1212" was used as the test material. There were three nitrogen application levels, 150 kg·hm-2 (N1), 210 kg·hm-2 (N2), and 270 kg·hm-2 (the conventional nitrogen application rate in the Huang Huai winter wheat area, N3), with the relative soil water content of 0-40 cm of each treatment was supplemented to 70% at the jointing and flowering stages. We investigated the effects of nitrogen rates on photosynthetic characteristics of flag leaves after flowering, 13C assimilate accumulation and transport, and water and nitrogen use efficiency after flowering of wheat. The results showed that photosynthetic capacity of flag leaves in the N2 and N3 was significantly higher than that in N1 14-35 days after flowering, and that there was no significant diffe-rence between N2 and N3 treatments. The 13C isotope tracing results showed that the translocation amount of 13C assimilates in vegetative organs in N2 was 12.1% and 7.1% higher than that in N1 and N3, respectively. The distribution amount of 13C assimilates in grains at maturity was 10.1% and 5.3% higher than that of N1 and N3, respectively. The amount of nitrogen fertilizer affected water consumption, water consumption proportion, and total water consumption in different growth stages of wheat. Water consumption during the whole growth period showed no difference between N2 and N3 treatments, but both were significantly higher than that for N1. Water consumption and water consumption proportion of N2 were higher from the jointing to maturity stages, water use efficiency of N2 was 7.5% and 4.8%, and grain yield was 4.7% and 10.9% higher than that of N3 and N1 treatments, respectively. The partial productivity of nitrogen fertilizer was 34.6% higher in the N2 than that of N3. Considering wheat grain yield and water and nitrogen use efficiency, 210 kg·hm-2 nitrogen application was the best rate under water-saving condition of supplementary irrigation after soil moisture measurement in the study area.

Development and application of a relative soil water content - transpiration efficiency curve for screening high water use efficiency wheat cultivars.

Improving water use efficiency (WUE) has been proven to be a prosperous way to produce more grain in drought-prone areas. Transpiration efficiency (TE) has been proposed as a criterion for screening cultivars with high WUE. This study quantifies the relations of TE to relative soil water content (RSWC) gradients using pot experiments and evaluates the capability of the relations of TE-RSWC on assessing the cultivar performance in field yield and WUE. Twelve winter wheat cultivars were grown at 6 RSWC, 12.1, 24.2, 36.3, 48.4, 60.5, and 72.6% of field capacity (FC = 24.8 g/g) for 33 days in tightly sealed pots preventing soil evaporation. The results showed that TE decreased power functionally following the increase in RSWC for all cultivars. The relationship could be described as TE = TE FC × (RSWC) b, named TE–RSWC curve. This curve could be divided into an orderly area where the rank of cultivars was stable when RSWC ≤ 12.1% or RSWC ≥ 72.6% and a disorderly area where the rank was unstable when 12.1% < RSWC < 72.6%. To assess the consistency of pot TE to field yield and WUE, the same 12 varieties were grown under rainfed and two irrigations (75 mm at the jointing and flowering stages, respectively). TE FC was found to be positively related to field yield and WUE independent of irrigation. TE measured near the wilting point was negatively related to field yield and WUE. These results indicated that TE FC could be used as a surrogate for screening high-yield and high-WUE cultivars. The consistency and inconsistency can be attributed to the orderly area and disorderly area of the TE–RSWC curves.

Deep soil water deficit causes Populus simonii Carr degradation in the three north shelterbelt region of China

Large-scale afforestation exacerbates soil water scarcity in a semiarid region of northern China, causing the formation of a dried soil layer (DSL) and ecosystem degradation, and overmature Populus simonii Carr (>30 years) degradation in the Three North Shelterbelt Program (TNSP) area has recently been observed. Determining the relationship between degraded Populus simonii Carr and soil water deficit is essential for afforestation in semiarid regions. We monitored soil water content (SWC) to a 160 cm depth in an area with five degradation degrees (healthy, light degradation, moderate degradation, severe degradation, and dead) to investigate soil water dynamics and DSL characteristics from May 2018 to December 2021. The results showed that: compared with that of healthy Populus simonii Carr (94.7 ± 26.2 mm), the shallow layer (0–80 cm) soil water storage of severely degraded (114.1 ± 29.9 mm) and dead Populus simonii Carr (128.0 ± 35.7 mm) was restored by 19.4 mm and 33.3 mm, respectively. However, the deep-layer (80–160 cm) SWC was difficult to recover and a DSL gradually developed, the DSL − SWC was only 9.3–11.95 %. The deep-layer relative extractable soil water (REW) of healthy Populus simonii Carr was significantly higher than that of moderately degraded, severely degraded, and dead Populus simonii Carr (P < 0.05). The deep-layer SWC decreased with increasing degradation due to coarser soils and increased BD. A greater bulk density (BD) and higher sand proportion reduced the soil water holding capacity. Poor site conditions reduced the resistance of shelterbelts, causing the degradation and mortality of Populus simonii Carr during drought. Therefore, our results improve the understanding of the soil water dynamics and degradation mechanism of Populus simonii Carr, providing a theoretical basis for managing and maintaining the TNSP.

Coordination of leaf hydraulic and economic traits in Cinnamomum camphora under impervious pavement

BackgroundPaved urban environments can pose great threats to the physiological functioning and ecological services of street trees. In this context, assessment of leaf phenotypic plasticity is crucial for understanding the ecological strategy of tree species under impervious pavements.ResultsIn this study, we measured a set of leaf economic traits, hydraulic traits of Cinnamomum camphora, and surrounding environmental factors in a street site (the soil was covered by the impervious pavement) and a park site (the soil was covered by grass) in Hefei, eastern China. Compared with the park site, trees in the street site had higher stomatal length (SL), leaf thickness (LT), maximum photochemical quantum yield of photosystem II (Y(II)), and lower stomatal density (SD), specific leaf area (SLA), the leaf water potential at 50% loss of hydraulic conductance (P50), and leaf turgor loss point (TLP). Redundancy analysis showed that air relative humidity and volumetric soil water content caused these traits to be altered.ConclusionsOur results showed that C. camphora adapted to the street pavement environment through the coordination of leaf economic and leaf hydraulic traits, and adopted the slow investment return type in the leaf economic spectrum and high drought resistance to meet its actual physiological needs. This finding provides a new perspective for understanding the physiological strategies of street trees to adapt to urban pavement environments.

Highly sensitive few-layer MoS2 nanosheets as a stable soil moisture and humidity sensor

In this work, an MoS2 nanosheet based ultrasensitive humidity and soil moisture sensor has been developed. MoS2 nanosheets are obtained by sonication based surfactant-induced exfoliation. The performance of the sensor is examined at room temperature (25 ∘C) with respect to various relative humidity (RH) levels and soil water content (θg). A 434 fold variation (35–15200 pF) in capacitance value is seen when the relative humidity level changes from 11% to 96%. The response and recovery times of the microsensor are approximately 30 s and 40 s, respectively. The capacitance of the MoS2 based sensor increases monotonically when the soil moisture content increases from 3.6% to 53% and 2.3–45% for black and red soil, respectively. The observed variation in capacitance corresponding to θgB = 53% (black soil moisture content) and θgR = 45% (red soil moisture content) is approximately 250 and 200 times that observed for the respective dry soil samples. The error in the soil moisture response measurement for the temperature variation from 25 ∘C to 70 ∘C is ± 2.52%. The device features stable performance for six months with reasonably high accuracy (maximum error ± 1.50%). The soil sensing results show fast response (35 s), negligible hysteresis error (2.80% at θgB = 31.9%), long-term stability (6 months and more), and good reproducibility (with more than 10 cycles).