Science and Engineering of Desertification Control
82
ZHANG Min, QIAN Duo, ZHANG Yong, LI Xinhao, LIU Peng, ZHAO Hongxian, LIU Xinyue, XU Qingfeng, ZHA Tianshan
Driving forces of the variations in sap flow inCotinus coggygria in Beijing
[Background] The water conservation function of a forest ecosystem is of great significance for sustainable development in a region. The transpiration of a plantation is an important component of forest water cycle and a key indicator reflecting the water conservation function of a forest. The measurement of sap flow can accurately estimate the process of a forest plantation. [Methods] Sap flow density of plantation species, Cotinus coggygria, was continuously measured in situ during the growing season from April to September in 2021 in Mangshan National Forest Park in Beijing using thermal diffusion method. Environmental factors including air temperature (Ta), relative humidity (RH), photosynthetically active radiation (PAR) and soil volumetric water content (VWC) were measured simultaneously. Besides, vapor pressure deficit (VPD) was calculated by substituting Ta and RH into the formula. This study examined the variations of sap flow density and environmental factors on the diurnal and seasonal scale, as well as analyzed the correlation between them via regression analysis and path analysis. [Results] The cumulative transpiration was 90 mm during the growing season. On the diurnal scale, sap flow density was mainly controlled by PAR, showing a positive correlation (R2 = 0.93), There was a time lag of 0.5 h between the peak values of sap flow density and PAR. On the seasonal scale, sap flow density was mainly regulated by VPD, and there was a threshold for this regulation at 1.5 kPa. When VPD is less than 1.5 kPa, the changes in sap flow density were directly related to VPD, showing a positive linear correlation between them (R2 = 0.94). When VPD is more than 1.5 kPa, the regulatory effect of VPD on sap flow density gradually weakened, while the regulatory effect of stomatal conductance (gs) on sap flow density increased, and gs had an exponential decline with the rise of VPD (R2 = 0.88). During the mid-growing season from June to August, sap flow density increased with the rise of Ta, VPD and PAR, but there was no significant relationship with VWC. [Conclusions] It is concluded that C. coggygri had the characteristics of lower water consumption,and its sap flow density was mainly controlled by PAR on the diurnal scale and was regulated by VPD on the seasonal scale. This species can adapt to atmospheric drought by regulating stomatal conductance. This study provides scientific basis for the species selection in developing forest plantations for soil and water conservation in Beijing.
WANG Junchuan, PANG Hong, WANG Ruixia, MA Guodong, JIN Lei, ZHANG Ping
Analysis of dune movement rate and contribution rates of internal and external factors based on Google Earth Engine and Canoco
[Background] Ningxia Lingwu Baijitan National Nature Reserve (NLBNNR) is adjacent to the east coast of the middle and upper Yellow River in China, and the minimum distance from the Yellow River to it is only 5 km, while there are a large number of moving dunes in the Nature Reserve. Accurate analysis of the moving rate and its control factors of the dunes in Baijitan has a guiding role in the management measures to reduce the amount of quicksand into the Yellow River. However, the current qualitative analysis and one-to-one quantitative analysis methods limit the accurate determination of the control factors of dune moving. [Methods] Three sample plots with triangular distribution and an area of 300 m×300 m were selected in the moving sandy land in Baijitan National Nature Reserve. Based on high-resolution remote sensing images, the geomorphological characteristic parameters and dune morphology parameters, and the moving rate of dunes in eight periods from 2008 to 2021 were analyzed. Based on Google Earth Engine(GEE), several environmental factors(resultant drift potential(RDP), fraction vegetation cover (FVC)、 accumulation precipitation, average land surface temperature (LST), average air temperature) value in each period of the study area were obtained, and then redundancy analysis(RDA) was used to reveal the contribution rate of each environmental factor to the moving rate of dunes. [Results] From 2008 to 2021, the ridge-line number of mobile dune gradually decreased, whereas the average length of ridge-line increased, which implied the dunes merged during the movement in NLBNNR. The moving rates of dunes steadily decreased in five stages, with 5.62 m / a in the first stage and 4.64 m / a in the last stage. The decreasing rate in each stage was 0.22 m / a to 0.28 m / a, with a total decrease of about 1 m / a in 13 a. The control factors of the moving rate of dunes were divided into internal factors and external factors. The height, width and defect density of the dunes were the internal control factors. The height and width of the dunes had extremely significant linear negative correlation with the moving rate, and the defect density was significant positively correlated with the moving rate (P < 0.01). The contribution rates of RDP, FVC, cumulative precipitation, average LST and average air temperature to dune movement were 78.7%, 6.7%, 3.9%, 2.7% and 2.6%, respectively, indicating that only RDP was the external control factor of dune movement. [Conclusions] The number of moving dunes decreased, while the volume of single dune increased, and the moving rate of dunes dropped in five steps from 2008 to 2021 in the Nature Reserve. The main external factor controlling the moving rate of dunes was RDP in Baijitan in the past 13 years, but LST was found to be another key factor controlling dune moving during the seasonal freezing period.
FANG Yingchao, ZHANG Yao, GE Hua, KONG Zhigang, JIANG Yi, ZHAO Fei
Effects of moisture content and relative density in weathering residual sand soils on shear strength
[Background] In the granite distribution area of Longling section of China-Myanmar oil and gas pipeline, the slope soil erosion of pipeline operation slope is very serious. The previous treatment experience shows that the conventional soil and water conservation measures have poor effect on the fully weathered granite backfill soil. For this, pertinence treatment measure research needs to develop. The shear strength of fully weathered granite backfill soil is affected by its moisture content and relative density. Optimizing themoisture content and relative density of backfill soil to improve the shear strength of soil is an important measure to control the erosion on the slope of Longling section of China-Myanmar oil and gas pipeline. [Methods] In this paper, the fully weathered granite backfill soil from the pipe trench of the China-Myanmar oil and gas pipeline in Longling county was selected as the test soil. The moisture content and relative density were measured by ring knife method. The shear strength parameters were determined by direct shear test with quadruple direct shear apparatus. Slow shear method was selected according to specification. The slope erosion modulus was measured by artificial simulated rainfall test. Two groups of soil samples were equipped according to the interval of 5% moisture content and 0.2 relative density, respectively, and the effects of moisture content and dry density on shear strength were analyzed. [Results] 1) With the dry density of 1.30 g / cm3 soil samples as a benchmark, when the soil moisture content is 5%, 10%, 15%, 20% and 25%, the cohesion C is 9.15, 13.67, 20.33, 8.87 and 3.63 kPa, respectively, and the internal friction angle ψ is 36.83°, 33.11°, 34.59°, 34.85ånd 32.42°, respectively. The 15% moisture content is the optimal moisture content. 2) Taking the soil sample with 15% water content as a reference, the cohesion C of soil with density ratio at 0.06, 0.27, 0.51, 0.72 and 0.83 are 20.00, 20.33, 26.75, 26.96 and 31.12 kPa, respectively, and the internal friction angle ψ are 31.77°, 34.59°, 36.97°, 39.07° and 41.88°, respectively. When the relative density of the soil increases from 0.06 to 0.83, the cohesion and internal friction Angle of the soil increase by 53% and 18%, respectively. When the relative density is 0.50, the improvement effect of soil shear strength parameters is the best. 3) The results of artificial simulated rainfall experiments show that the slope soil erosion modulus is related to the shear strength of soil, especially negatively correlated with cohesion. [Conclusions] The results show that the moisture content of fully weathered granite backfill soil increases, and the cohesion increases first and then decreases rapidly, and the internal friction angle decreases gradually, under the same dry density. Under the same moisture content, the cohesion and internal friction angle increase with the increase of relative density. Under the same moisture content, increasing the relative density of soil can effectively improve the anti-erosion ability of soil.
ZHANG Wei, YANG Hailong, ZHANG Songyang, YANG Penghui, YANG Siyuan
Study on comprehensive properties of polyurethane used as curing material of coal gangue
[Background] The Muli mining area is an indispensable water conservation area and the core component of the ecological security barrier in the Qilian Mountains, and its ecological status is extremely important. However, with a large number of excavations, the Muli mining area has accumulated largescale coal gangue piles. The weathering deposits on the surface of these coal gangue slopes cause preferential flow, resulting in a series of ecological and environmental problems such as soil damage, soil erosion, and slope instability. In order to solve the above ecological and environmental problems, this paper chose Muli mining area as the research area. [Methods] In view of the insufficient research on the actual effect and key influencing factors of polyurethane solidified coal gangue, this study carried out 45 groups of uniaxial compression tests of coal gangue-polyurethane solidified specimens with different proportions, and 60 groups of artificial rainfall tests of coal gangue-polyurethane solidified slopes under different working conditions. The main mechanical properties, permeability and technical economy of coal gangue-polyurethane composites were studied. The analytic hierarchy process was used to comprehensively evaluate different mix ratios, and to reveal the key influencing factors, and screen the optimal mix ratio scheme. [Results] 1) Polyurethane concentration contributed the most to improving the compressive strength of the solidified specimens, while the elastic modulus was mainly affected by the particle size of coal gangue. 2) The average runoff rate of solidified coal gangue slope was proportional to the concentration of polyurethane, proportional to the density of coal gangue, and inversely proportional to the particle size; the average sediment yield was inversely proportional to particle size of coal gangue, density of coal gangue and polyurethane concentration. The stable infiltration rate was proportional to the particle size of coal gangue, and the density of coal gangue was inversely proportional to the polyurethane concentration and inversely proportional to the density. 3) The comprehensive evaluation of 45 groups of coal gangue-polyurethane curing schemes was carried out. When the particle size was 0 0.5 mm, the comprehensive evaluation value was 0.260 68 0.725 35. When the particle size was 0.5 1 mm, the comprehensive evaluation value was 0.313 86 0.442 87. When the particle size was 1 2 mm, the comprehensive evaluation value was 0.266 33 0.311 14. [Conclusions] The optimal slope stabilization scheme is coal gangue with the particle size 0 0.5 mm, the density 1.55 g / cm3, polyurethane concentration 3.5% The coal gangue-polyurethane curing scheme may greatly improve the compressive strength of the slope, and effectively reduce the infiltration performance, while maintaining a good economy (about 17 RMB Yuan / m2). The research results have important technical reference for the ecological restoration project of Muli Coal Mine.
KONG Lingjian, ZHANG Lin, WANG Yingnan, ZHANG Ming, SHI Xingping, HUANG Zhanbin
Experiments on the configuration of serpentine slag soil and its improved planting substrate in alpine mining area: A case study of the West Copper Mine in Qinghai
[Background] This study explores the impact of mineral resource development on regional soil quality, addressing challenges like soil structure damage and fertility decline in alpine mining areas. The proposed solution involves combining serpentine residue soil with raw soil from early mine construction, incorporating local materials like sheep manure, TG amendment, and water retaining agent. The goal is to enhance soil structure and nutrient conditions, establishing a suitable soil matrix for vegetation recovery. This approach aims to improve soil water and nutrient retention in mining areas, supporting soil restoration in high-altitude regions like Qinghai West Copper Mine [Methods] In this study, samples representing storage raw soil and serpentine residue soil were collected from platforms 4290 and 4138 of Qinghai West Copper Mine using a three-mixed-one sampling method. The experiments included substrate formulation tests, potting tests, and field plot planting substrate amendment tests to assess their effects on soil properties and growth of one and six plant species. Physical and chemical indicators such as soil bulk weight, pH, porosity, EC, and nutrient content were measured using standard methods. Microsoft Excel and SPSS 26 were used to analyze the experimental data for statistics and to determine the significance of differences. [Results] 1) Different ratios of serpentine residue soil and raw soil significantly affected the physicochemical properties of the substrate. When the ratio of serpentine residue soil to raw soil was 6 颐 4, the formulated soil bulk density, pH, and electrical conductivity decreased by 2.20%, 7.95%, and 19.88%, respectively, compared to the pure serpentine residue soil control (CK). Meanwhile, soil salt, soil capillary porosity, soil field water-holding capacity, available phosphorus, available potassium, total nitrogen, and hydrolyzable nitrogen contents increased significantly by 15.12%, 7.02%, 75.23%, 328.88%, 117.65%, and 32.38%, respectively, meeting the basic requirements of a greening substrate. 2) Pot planting results indicated that forage grasses like Elymus dahuricus showed increased emergence when planted alone or mixed with six grass seeds at a 6 颐 4 ratio of serpentine residue soil to raw soil, with a 10.34% and 25% increase, respectively. Additionally, the height, aboveground biomass, and belowground biomass of E. dahuricus increased by 7.25%, 87.00%, and 246.95% compared to the control CK. 3) The field plot planting test indicated that with a formulation ratio of 6颐 4 for serpentine residue soil to raw soil, and the addition of 1 kg / m2 TG amendment, 12 g / m2 KM 3005 water retaining agent, and 3.12 kg / m2 of goat slate manure, the seedling height and biomass in the gradient test of goat slate manure and TG amendment increased by 38.30% and 200.43%, and 21.43% and 358.02%, respectively, compared to the control. These findings have been applied in an engineering demonstration. [Conclusions] The study concludes that a 6颐 4 mix of serpentinite slag soil and local raw soil improves physicochemical properties in high-altitude mining areas. This ratio enhances soil structure, lowers pH and conductivity, and increases pore density and water retention. Enriched with nutrients, it supports better grass growth. Pot experiments confirm suitability for seedling emergence and overall growth. Field trials with serpentinite slag soil, raw soil, sheep manure, TG amendment, and KM 3005 water retaining agent promote superior ecological restoration in soil-deficient, high-altitude mining areas.
ZHAO Zhonghe, TU Panpan, CHEN Huan, ZOU Yan, SONG Huiping, FENG Zhengjun
Effects of different upper bearing materials of eco-blanket on soil moisture regime and plant growth
[Background] Eco-blanket, a convenient material for the restoration of mining area, can control soil erosion and reduce water evaporation. Traditional eco-blanket generally use non-woven fabrics as the upper bearing material. The non-woven fabrics can effectively bear the substrate of eco-blanket and prevent soil erosion, but sometimes it will impede the water infiltration and plant germination. Therefore, it is necessary to find a substitute for the non-woven fabric as the upper bearing material to improve the performance of eco-blanket in mining area restoration. [Methods] A greenhouse experiment was conducted to compare the performances of four different upper bearing materials (fiber paper, thin nonwoven fabric, thick non-woven fabric and knitted fabric) in affecting plant growth, water infiltration rate and soil water content. Bermuda(Cynodon dactylon)grass was planted in a plastic slope with a length of 50 cm, a width of 25 cm and a height of 10 cm for 30 d. The plant growth indexes (vegetation coverage, plant height, plant density and aboveground biomass), the water infiltration rates and changes of soil moisture were detected regularly. [Results] 1) After 30 d of planting, the hierarchy of plant growth indexes was observed as follows: the knitted fabric group showcased superior plant growth and demonstrated the most even distribution of plants on the slope, followed by the thin non-woven fabric group, the fiber paper group, and lastly, the thick non-woven fabric group. 2) At the day 30, the descending order of infiltration levels was the knitted fabric group leading with 0.52 L, then the fiber paper group at 0.47 L, followed by the thin non-woven fabric at 0.44 L, and finally the thick non-woven fabric at 0.41 L. Compared to the day 10, these values increasedby 18.0%, 14.3%, 17.5% and 17.9%, respectively. 3) Within 24 h, soil moisture content for each treatment decreased progressively over time. The fiber paper group, in particular, recorded a significantly lower soil moisture content than the other three groups. The fiber paper group experienced a 28.4% reduction in soil moisture, substantially more pronounced than the reductions in the thick non-woven group at 12.7%, the thin nonwoven group at 16.2%, and the knitted fabric group at 17.2%. [Conclusions] Based on the above results, the knitted fabric seemed to be the best upper bearing material in this study. Its performance in water infiltration and evaporation reduction were ideal and showed no suppression for plant germination, leading to the best vegetation restoration in the four materials. The knitted fabric is therefore an ideal upbearing material, which can replace traditional non-woven fabric and improving the performance of ecoblanket in slope vegetation restoration.
CAI Junshun, WANG Jingxue, XIAO Huijie, XIN Zhiming, WANG Baitian, LI Junran
Wind-sand characteristics and prevention effect of shelterbelt in Ulan Buh desert oasis
[Background] Farmland shelterbelt plays an important role in keeping soil and water and controlling wind erosion. In recent years, with the development of technology, the research of effectiveness on shelterbelts for prevention wind and resistance sand has gradually been various. Although a large number of researches have been investigated, the research of wind-sand characteristic on field measurement in a region area is necessary, due to the different structure of shelterbelts and topography in other regions. [Methods] Based on the data of wind speed, wind direction and sand monitored by two towers located in desert-oasis transition zone and inside oasis in Ulan Buh desert from 2019 to 2020, the characteristics of wind field and sand movement was analyzed through using statistical methods. Combined the wind speed and sand transportation at 9 different measurement heights and times, the relationship of wind-sand and height, time and space were explored. [Results] 1) The wind direction is dominated by northeast and southwest directions with frequency percentage of 14% and 13% in the desert-oasis transition zone, and with the percent of 12% and 11% in the oasis, respectively. 2) The mean wind speed gradually increased with measurement height in both of desert-oasis transition zone and inner area of oasis. Prevented by shelterbelts, the mean wind speed decreased from the desert-oasis transition zone to inner area of oasis. The records of wind speed decreased about 8.8% and 7.8% when the wind speed in ≥4 8 m / s and ≥8 m / s, respectively. 3) The monthly maximum mean wind speeds in desert-oasis transition zone and inner area of oasis reached peaks in summer, autumn and the end of spring. From the desert-oasis transition zone to oasis, the proportion of summer wind speed in the northeast (NE) direction decreased from 20% to 15%, and the proportion of winter wind speed in the southwest (SW) direction decreased from 20% to 16% . Meanwhile, the monthly maximum mean wind speed showed a linear relationship with the mean value of wind speeds. 4) The sediment fluxes in both regions had the decreasing tendency with the increase of observation height. Affected by the shelterbelt, the decreases of horizontal sand flux and vertical sand flux in the same observation height were 65% and 36%, respectively. The sand transportation was dominated by east and east-southeast directions in both regions. This tendency was less affected by observation height in oasis, but may be changed in different heights in desert oasis transition zone. Drift potential decreased from desert-oasis transition zone to oasis. [Conclusions] Shelterbelts systems in desert oasis has obvious influence on the wind and sand activities in the regional scale, and can reduce the soil and water loss caused by wind erosion. This result may provide a scientific basis for the optimization and adjustment of the shelterbelt effectiveness. It has great value to maintain the sustainable development in oasis.
ZHANG Yuexin, MA Yunxia, MA Xiuzhi, LI Gangtie, ZHANG Bo
Effects of four arbuscular mycorrhizal fungi inoculation on the drought resistance of Ulmus pumila seedlings
[Background] Elm (Ulmus pumila) is a masculine tree species with well-developed root system, rapid growth and drought tolerance, and it is an ideal tree species for afforestation in arid and semi-arid sandy areas. However, in recent decades, frequent droughts due to global climate change have led to serious degradation of elm forest ecosystems. The ability of arbuscular mycorrhizal (AM) fungi to form a reciprocal community with host plant roots and improve the growth and development of host plants is of great significance to the improvement of terrestrial ecosystem functions. In this experiment, we investigated the physiological mechanism of AM fungi increasing the drought resistance of U. pumila by artificially simulating the drought environment, and screened the drought-tolerant strains, so as to provide preliminary theoretical preparation and technical support for mycorrhizal technology to restore vegetation and improve ecological environment in arid and semi-arid areas. [Methods] Funneliformis mosseae, Claroideoglomus etunicatum, Rhizophagus intraradices and their mixtures of above three were selected as experimental agents, and potted elm seedlings used as experimental materials. Three water gradients were set by manual water control: normal water supply, moderate drought, and severe drought. The root shoot ratio, mycorrhizal infestation rate, mycorrhizal dependence, photosynthetic parameters, malondialdehyde content, peroxidase, catalase and peroxide dismutase activities of elm seedlings under different treatments were measured, and the data were statistically analyzed by Microsoft Excel 2012, and the data were analyzed by two-factor ANOVA with SPSS23 software, and the fuzzy integrated evaluation method of affiliation function was used to comprehensively evaluate the drought resistance of different strains. [Results] 1) Under different moisture conditions, inoculation with AM fungi increased the plant height, root shoot ratio and mycorrhizal dependence of U. pumila seedlings to different degrees and decreased the mycorrhizal infestation rate compared with the uninoculated control plants. 2) Under three moisture conditions, inoculation with AM fungi decreased the malondialdehyde content of U. pumila seedlings to different degrees and increased the catalase, peroxidase and peroxidase activities of U. pumila seedlings compared with the control plants. 3) The net photosynthetic rate, transpiration rate and leaf stomatal conductance of U. pumila seedlings gradually decreased and the intercellularCO2 concentration gradually increased as the water supply decreased. 4) Mycorrhizal elm seedlings were all more drought tolerant than non-mycorrhizal seedlings, and their drought tolerance was from the strongest to the weakest in the order of mixed bacterial agent > C. etunicatum > R. intraradices > F. mosseae > CK. [Conclusions] Under water stress, AM fungi could make U. pumila seedlings more adaptable to soil moisture changes, and the mixed mycorrhizal agent had the best drought tolerance.
Spatial-temporal heterogeneity of coupling coordination between rocky desertification and urbanization in Guangxi
[Background] Karst rocky desertification is a typical ecological environment issue in the southwest karst region. How to correctly understand the coupling relationship between karst rocky desertification and urbanization is a necessary condition for formulating karst rocky desertification control policies and guiding the sustainable development of cities and towns. [Methods] Based on Google Earth Engine calling Landsat images, an evaluation model of karst rocky desertification degree was constructed and comprehensive karst rocky desertification indexes were calculated. The comprehensive urbanization indexes were calculated using the entropy method and the linear weighting method, and the temporal and spatial characteristics of the evolution of the coupling coordination degree of karst rocky desertification and urbanization from 2000 to 2020 were explored with the help of the coupling coordination degree model. [Results] 1) The degree of karst rocky desertification shows a downward trend, but the regional differences are obvious. Severe and very severe karst rocky desertification is concentrated in the central and southwestern regions; the level of urbanization is developing rapidly, and the urbanization level in the eastern region is higher than that in the western region. 2) The coupling and coordination degree between karst rocky desertification and urbanization has been continuously improved, gradually transitioning from “uncoordinated development, urbanization lags behind” in 2000 to “ transformed development, karst rocky desertification lags behind” in 2020. 3) The faster the urbanization level improves in counties and districts, the more obvious the effect of karst rocky desertification control, and the corresponding coupling coordination degree is higher. [Conclusions] The results of this study can provide reference for the local government to better formulate sustainable development urbanization plan and better balance urbanization and ecological environmental protection.
WANG Qian, XIE Yingchao, LI Mingwei, LI Qiang, CHEN Jingling, KOU Yuanbo
Study on base line of CWSI for Quercus variabilis seedlings based on energy balance principle
[Background] In order to accurately determine the linear regression relationship between leaf temperature difference and atmospheric vapor pressure difference (VPD) of Quercus variabilis seedlings under the condition of adequate water supply, and to optimize the crop water stress index (CWSI) empirical model established by predecessors, Zhengzhou city in Henan province, where plant drought is a significant problem, was selected as the main research area, aiming to analyze and understand the dynamic change of soil water and the response degree of plants in a more representative way, so as to build a more applicable CWSI model and soil water diagnosis model. [Methods] The temperature, solar radiation, leaf temperature difference and atmospheric vapor pressure difference of Q. variabilis seedlings in the pot experiment were measured by dry-wet reference surface method in research base of College of Forestry, Henan Agricultural University. The reasonable upper and lower baselines of CWSI model of Q. variabilis seedlings were determined by theoretical analysis and calculation of energy balance principle. [Results] Under dry reference plane condition, the leaf temperature difference ∆t干 of Q. variabilis seedlings was significantly positively correlated with solar radiation Q, and the upper baseline of CWSI empirical model was determined as a straight line: ∆t干 = 0.007Q + 1.621. Under the wet reference plane, there was a negative correlation between leaf temperature difference ∆t湿 and V (VPD) of atmospheric saturated water vapor pressure difference, and the linear regression relationship was significant. The optimized lower baseline of CWSI empirical model was obtained: ∆t湿 = 1.218V + 1.987. Thus, the CWSI empirical model after optimizing the lower baseline is I = tca (1.218V + 1.987)/ (0.007Q + 1.621) (1.218V + 1.987), tca is the measured leaf-air temperature difference. The CWSI value of Q. variabilis seedlings was calculated by using the optimized CWSI model with the obtained upper and lower baseline. The linear relationship between CWSI value I and soil moisture θ was significant. The diagnostic formula is θ = 24.65I + 27.91. The relationship between CWSI and soil moisture content was as follows: 12% soil moisture corresponded to mild drought, and CWSI was about 0.65. The soil moisture of 8% 10% corresponded to moderate drought, and the CWSI was 0.75 0.8. Soil moisture of 5% 8% corresponds to severe drought and CWSI is 0.8 0.95. When soil moisture was lower than 5% and CWSI was greater than 0.95, the seedling stress was fatal. [Conclusions] The relationship between leaf temperature difference and VPD can be more accurately determined by the heat budget calculation method of energy balance equation, so as to optimize the CWSI model, and then calculate the linear relationship between CWSI of different crops and soil moisture according to this model, and obtain the soil moisture diagnosis model. The soil moisture of different crops or forest plants can be diagnosed according to the solar radiation and air temperature and humidity of remote sensing leaves and weather stations.
ZHANG Yuxuan, WANG Yunqi, WANG Yujie, YANG Feng, ZHU Junlin, ZHENG Yonglin, LI Manyi, MENG Xiangjiang, XUE Lanlan
Nitrogen and phosphorus contents and ecological stoichiometry of seedlings of four plant species in Jinyun Mountain in response to simulated acid rain
[Background] Acid rain pollution can indirectly affect plants through direct leaching to plants or by causing soil acidification. Nitrogen (N) and phosphorus (P) are important components for the growth and development of organisms, and acid rain leaching to plant seedlings can affect the N and P content of plants, and different concentrations of acid rain treatment affect different plant species differently. The study area is located in the Jinyun Mountains of Chongqing, which is one of the most affected areas by acid rain in China. The aim of the study is to investigate the relationship between plant nutrients and their stoichiometry and their responses to acid rain by investigating the effects of acid rain on the N and P contents and ecological stoichiometry of plant seedlings. [Methods] Taking two-year Cunninghamia lanceolata, Pinus massoniana, Cinnamomum camphora and Phyllostachys edulis seedlings as the research objects, in May 2021 in Jinyun Mountain, Chongqing, the pH value was set to 7.0 (control), 4.5, 3.5 and 2.5, a total of 4 gradients, record as CK, pH4.5, pH3.5 and pH2.5 respectively,an in situ simulated acid rain spraying trial was carried out for a period of 4 months. The N, P content and stoichiometric ratio of different measured plant seedlings were analyzed, and the nitrogenphosphorus ratio was calculated. [Results] Under different concentrations of acid rain, the N and P contents of leaves of C. lanceolata, P. massoniana, C. camphora and P. edulis were higher than those of roots and stems. The sensitivity coefficient of N content in roots and leaves of seedlings to acid rain treatment was higher than that of stems. At pH3.5 and pH4.5 of C. lanceolata and P. massoniana were N-limited, P. edulis was N-limited at pH3.5, and C. camphora was P-limited at pH3.5 and pH4.5. Organ N:P measured characteristics had different effects, affecting the balance of N and P content in plant seedlings. There was a positive correlation between N and P contents in C. lanceolata, P. massoniana, C. camphora and P. edulis roots, and N and P contents showed a certain proportion of composition and coordination. [Conclusions] Different plants respond differently to acid rain treatment, and the nutrient content of plants and their distribution among various organs are related to the morphological and structural characteristics of the plants themselves and the characteristics of external environmental changes.
