An artificial simulated experiment on canopy rainfall interception
[Background] Canopy interception method at present is still in short, though simulated rainfall fixed some problems on precipitation, the research on canopy interception of tall shrubs and even arboreal forests is still limited. Beijing is located in a sub-humid and sub-arid continental monsoon climate area. This work is to study the redistribution of rainfall by the canopy.[Methods] A simulated canopy rainfall interception experiment was conducted under the condition of artificial rainfall with QY JY-503C. and the results from the canopy interception simulated experiment was compared with that of field data in Robinia pseudoacacia, Platycladus orientalis, and Pinus tabulaeformis sample plots under the condition of natural rainfall. Field data of natural rainfall was collected in July to September 2018 of 3 sample plots.[Results] 1) In the study period, canopy interception of R. pseudoacacia, P. orientalis and P. tabulaeformis sample plots were orderly 68.45 mm,78.21 mm and 90.15 mm. They respectively accounted for 26.08%、29.79% and 34.34%t of the rainfall outside the forest. 2) Compared with canopy interception rates of three tree species simulated canopy with similar leaf area index, the canopy interception rates of R. pseudoacacia, P. orientalis and P. tabulaeformis under the condition of natural rainfall were 4.57%, 2.7% and 0.63% respectively. This simulated experiment was better for canopy simulation of P. orientalis and P. tabulaeformis. 3) With the increase of leaf area index, the penetrating rainfall, throughfall ratio and stemflow rate of the same tree species under the same rainfall condition showed a decreasing trend. However, the canopy interception rate showed an increasing trend. 4) The canopy interception test of canopy model that took leaf area index as the control variable reflected canopy interception characteristics under natural rainfall conditions.[Conclusions] In the research period, the canopy interception abilities of three species are all in the middle and upper level among the different forests. This study may provide new research and test method for canopy interception research and a theoretical basis for forest eco-hydrological process and impact mechanism research.
XIA Bing, FAN Xuanmei, GUO Xiaojun, YANG Fan, ZOU Chengbin, XIONG Kunyong
Spatial distribution characteristics and analysis of soil erosion under earthquake effect: A case study of Jiuzhaigou earthquake
[Background] The natural factors affecting soil erosion are soil, rainfall and vegetation. The structure and particle composition of the soil affect the soil's ability to resist erosion and erosion. When the soil is loose, the adhesion between particles is weak, and the structure is loose, it is susceptible to water erosion. The earthquake in Jiuzhaigou caused the mountain body to be broken, soil loose and vegetation destruction in Jiuzhaigou county, which greatly increased the probability of soil erosion in Jiuzhaigou County.[Methods] Based on GIS and USLE models, the soil erosion intensity in the disaster area before and after the earthquake was quantitatively calculated, and the soil erosion parameters before and after the earthquake were briefly compared and analyzed, and the areas affected by the earthquake were divided. Combined the regional statistical analysis (Zonal) with ArcGIS, the relationship between the spatial distribution of soil erosion in this area and the distance from the fault, slope, elevation and aspect were explored.[Results] 1) Compared with that before the earthquake, the erosion area after the earthquake increased by 8.1%, the total erosion increased by 28%, and the erosion intensity increased by 18.39%. In the erosion intensity category, the area proportion of slight, light and moderate erosion all decreased after the earthquake, while the area proportion of moderate and serious and above erosion increased.2) The closer the distance from the fault was, the larger the area of the earthquake prone was. As the distance from the fault increasing, the area of the easily-affected area decreased. In the easily-affected area, the increment of erosion intensity decreases sharply with the distance from the fault increasing. 3)The areas susceptible to earthquake in the study area mainly occured at elevations of 2 000-4 000 m, accounting for 99% of the total area. In the slope range of 30°-60°, the erosion area accounted for 89.25% of the total area of the susceptible area, respectively. The areas affected by earthquake were distributed in the north slope, the northeast slope and the southeast slope, the erosion area accounted for 61.07% of the total area.[Conclusion] The spatial distribution characteristics of soil erosion are closely related to the distance, elevation, slope and aspect of the fault. This result may provide a theoretical basis for soil and water conservation after the earthquake.
Effects of drying-rewetting alternation on water-holding capacity of sandy soil added with super absorbent polymer
[Background] Super absorbent polymer (SAP) is a kind of polymer with high hydrophilicity and repeated suction function. In arid and semi-arid areas, it is an effective measure to add SAP to sandy soil in order to restore ecological environment and improve physical and chemical properties of soil. For SAP applied in arid and semi-arid sandy soil, its durability is related to the long-term effect of drought resistance and moisture preservation. Drying-rewetting alternation is a common phenomenon in arid and semi-arid areas. SAP added to the soil will absorb water and expand when climate is wet, and slowly lose water when climate is dry, and go through the process of repeated water absorption and water loss. Although the existing studies have mentioned the possible impact of this process on the water retention performance of the SAP, there are few experimental verification and analysis of the impact mechanism.[Methods] In order to study the effect of drying-rewetting alternation on sand soil with SAP, sand soil in Lingwu city of Ningxia Hui Autonomous Region was selected as the research object. Different cycles of drying-rewetting alternation, different types and amounts of SAP were selected as experimental variables to complete the simulated soil column experiment. The soil physical and chemical properties, soil cumulative evaporation, soil water characteristic curves and soil moisture availability were selected as the test indexes.[Results] 1) The saturated water content and total porosity of sandy soil with SAP increased, the Gardner model parameter a of sand soil with SAP increased, and the cumulative evaporation decreased. The more the amount of SAP was, the greater the impact was. The water-holding capacity of sandy soil containing 6 g/kg acrylamide acrylate copolymer cross-linker was the best. 2) After several drying-rewetting alternations, the effect of increasing the soil water-holding capacity was reduced, the saturated water content and total porosity of sandy soil decreased, and the cumulative evaporation of sandy soil increased. After several drying-rewetting alternations, the water-holding capacity of sand soil with high dosage of SAP weakened more than that with low dosage of SAP. 3) The soil available water content of the sand soil with SAP increased after 1 to 3 cycles of drying-rewetting alternation and it decreased after 3 to 6 cycles of drying-rewetting alternation. After 10 drying-rewetting alternations, the soil water-holding capacity of sand soil with SAP was still better than that of sandy soil without SAP.[Conclusions] The drying-rewetting alternation may weaken the water-holding capacity of sand soil with SAP by reducing the saturated water content and total porosity. However, the drying-rewetting alternation increases the soil available water content of the sand soil with SAP and then decreases, thus SAP still has a strong application value.
LI Changzhun, CHEN Lixin, DUAN Wenbiao, LI Shaoran, LI Yifei, YU Yingying, ZHU Jiahui, ZHAO Gerong
Effects of litter treatment on soil organic carbon, total nitrogen and total phosphorus in different forest types
[Background] By removing and adding litter, the effects of litter treatment on soil active organic carbon and soil nutrients of Pinus koraiensis plantation and broad-leaved K.koraiensis forest were explored, which provided scientific basis and practical reference for sustainable management of the two forest types.[Methods] In May 2018, the questions stated above were studied in Liangshui National Nature Reserve of Xiaoxing'an Mountains by setting up test plots, removing and adding litter, collecting and analyzing soil samples and data processing. The experiment was conducted to remove litter, add double litter and keep the original litter unchanged (control). Each treatment has three replicates. In May, August and October 2018, soil samples in 0-20 cm were collected in each test unit. Bring the soil sample back to the laboratory in time for processing.[Results] In K.koraiensis plantation, litter removal treatment had significant effects on soil easily oxidized organic carbon, particulate organic carbon and light fraction carbon (P<0.05). Adding litter treatment had no significant effects on soil easily oxidized organic carbon, but had significant effects on soil particulate organic carbon and light fraction carbon (P<0.05). Litter treatment had no significant effect on soil easily oxidized organic carbon, but had significant effect on soil particulate organic carbon and light fraction carbon (P<0.05). Adding litter treatment had no significant effect on soil easily oxidized organic carbon, but had significant effect on soil particulate organic carbon and light fraction carbon (P<0.05). The effect of litter removal treatment on soil total organic carbon of two forest types was significant (P<0.05), but the effect of litter addition treatment on soil total organic carbon was not significant; the effect of litter removal and litter addition treatment on soil total nitrogen and total phosphorus was not significant. The effects of litter removal and addition on soil C/N of K. pine plantation were not significant; the effects of litter removal on soil C/N of broad-leaved P.koraiensis plantation were significant (P<0.05), but the effects of litter addition on soil C/N were not significant.[Conclusions] In P. koraiensis plantation, adding litter treatment had no significant effect on soil easily oxidized organic carbon, while removing litter treatment had significant effect (P<0.05) on soil easily oxidized organic carbon; in broad-leaved K. pine plantation, adding and removing litter treatment had no significant effect on soil easily oxidized organic carbon. In the two types of forest, the removal and addition treatments had significant effects (P<0.05) on soil particulate organic carbon and light fraction carbon. In the two forest types, the effect of litter removal on soil total organic carbon was significant(P<0.05), but the effect of litter addition was not significant; the effect of litter removal and litter addition on soil total nitrogen and total phosphorus was not significant.
YANG Chuanqing, CHEN Hang, GU Zheyan, WANG Wei, JU Jing, CHEN Lidong, ZHU Huagang
Analysis on influencing factors of runoff evolution in typical watershed of the upper Huaihe River: Illustrated by the case of the Bailianya basin
[Background] For last 30 years, the global temperature rose with the influence of the precipitation spatial distribution pattern. Economic and social development, the spatial and temporal of the runoff varied significantly, and its evolution also showed a strong randomness at the same time. The Bailianya river basin is located in Dabie mountain, which is the watershed between Yangtze River basin and Huaihe River basin. The study on the characteristics of runoff change in the Bailianya river basin and its relationship with environmental factors may provide decision-making basis for regional flood control and disaster reduction, industrial and agricultural production and rational utilization of soil and water resources.[Methods] The variation characteristics of the runoff of Bailianya basin and its correlation with major environmental factors from 1970 to 2009 was detected through the Mann-Kendall test, Yamamoto method of signal-to-noise ratio and the cross wavelet transform analysis. The relationship between time series of environmental factors and runoff in different frequency domain was revealed using cross wavelet analysis. The response of runoff to the change of underlying surface elements was also clarified based on the analysis of remote sensing images in 3 stages. The coupled oscillations of runoff time series, precipitation and air temperature in Bailianya river basin were investigated from the frequency domain, which reflected the correlation between runoff and climatic factors on different time scales.[Results] 1) The distribution of runoff was uneven during the year and mainly concentrated in June and July. The 2 abrupt changes of runoff occurred in 1983 and 2004-2005. Runoff demonstrated a small cycle of 0.5-3 year(s). 2) There was strong correlation between runoff and precipitation at a cycle of 1-2 year(s) in 1986-1996 and at a cycle of 2.5-4 year(s) in 1998-2002. Runoff responded to precipitation fast with most high energy time-frequency domain characterized by phase relationship. 3) Interactions between the runoff and the temperature were mainly concentrated in a cycle of 1-3.8 year(s) in 1988-2000. The phase of temperature was prior to that of the runoff. Runoff responded to temperature with a time lag. The change of underlying surface elements strongly changed the nature of the surface of the basin, and had certain influence on the hydrological cycle at different time and space scales, causing the change of runoff and confluence conditions in the basin, and thus changing the hydrological process of the basin. Forest and farmland were the main underlying factors that caused runoff change in Bailianya basin, and had obvious influence on runoff change. With the increase of forest area and the decrease of farmland area, runoff showed a decreasing trend.[Conclusions] With the change of climate variation and underlying surface condition, the runoff of Bailianya river basin varies significantly in the interannual period and within a year, showing different correlation characteristics with different environmental factors. Precipitation in Bailianya river basin is the direct factor of the runoff change. The response of the runoff to air temperature is of time delay. Compared with forest, farmland is weak in rainfall interception and infiltration, and the conversion of farmland to forest will lead to the relative reduction of runoff.
ZHENG Yi, LI Suyan, SUN Xiangyang, QU Bingpeng, LI Xiaochong, WANG Xinyu, XIONG Kaiyi
Application performance of tree pit cover plate made of green waste
[Background] In order to cover the bare tree pits in our cities and look for an innovative and ecological approach of organic cover. The cover plate, which was added the environmentally friendly waterborne polyurethane adhesive into green waste (dead branches of Cupressus funebris) were used to cover the bare tree pits. Application performances were carried out to determine its capacity of water-holding, ability of pressure resistance and resistance to cigarette burning in the indoor simulation experiment.[Methods] The size of dead branches of C. funebris was divided into 2 types:0~1 cm length(fine) and 1~3 cm length(coarse). The added amounts of waterborne polyurethane adhesive were in 5 levels (20%, 25%, 30%, 35% and 40%, respectively). Then the raw materials and the adhesive were mixed up thoroughly and was put into the size 10 cm×10 cm×5 cm cuboid opening mold and pressed with 20 kPa pressure, 10 different sizes of cover plates were obtained at last. Its capacity of water-holding, ability of pressure resistance and resistance to cigarette burning was determined.[Results] 1) The cost of cover plate with area of 1 m2 and thickness of 5 cm (the amount of adhesive was 25%) was RMB 87 Yuan, almost 1/5 cost of the same size cast iron cover plate.2) All cover plates had a certain density deviation and had a slight water absorption thickness expansion phenomenon. 3) There was a significant logarithmic function between water-holding capacity and soaking time, and there was a significant power function between water absorption rate and soaking time. The 5 fine branched cover plates had a higher water-holding capacity than that of 5 coarse branched cover plates, but its pressure resistance was slighter than the five fine branched cover plates. The water-holding capacity was highest, 2 209.25 g/kg and 999.15 g/kg respectively, when the amount of the adhesive of fine branched and coarse branched cover plates were at 25% and 30%, the effective interception capacity and effective rate of interception capacity were also maximum. 4) Compression strength of all cover plates were considerably higher than 0.52 MPa (Maximum pressure generated by a pedestrian weighing 100 kg during normal walking), all cover plates had not been burned by cigarettes.[Conclusions] Among all cover plates, fine branched with the 25% amount of waterborne polyurethane adhesive, had the largest water-holding capacity, ability of pressure resistance and resistance to cigarette burning. Therefore, not only could it cover the bare tree pits in our cities replacing the traditional inorganic cover material such as the cast iron but also utilize garden waste adequately and environmentally friendly.
Advances in the study of the stability of soil organic carbon storage affected by water erosion
[Background] Water erosion is an important process which causes shifts in the soil organic carbon storage and the global carbon cycle process. The physicochemical and biological stabilities of soil organic carbon are strongly affected by water erosion. Recently, growing studies show that the replacement of soil carbon on an eroding area is a crucial mechanism, the transport of organic carbon is re-aggregated in a depositional area then buried in the deep layer, and episodic erosion can bury a lot of erosion materials in low-lying depositional sites. Therefore, more and more investigators suggest water erosion leads to an increase of soil organic carbon storage.[Methods] We collected all relevant literature for this review. Based on these reference, we reviewed mechanisms of water erosion, current status and types of water erosion, divergence of carbon source or sink for CO2 under water erosion, factors impacting water erosion, effects of water erosion on soil organic carbon stock, effects of water erosion on soil carbon stability, and to further strengthen the study areas.[Results] Many investigators studied the relationship between water erosion and biogeochemical cycling at eroding and depositional zone, and obtained a series of beneficial results. 1) There are effects of water erosion on soil carbon storage. Soil scientists and agronomists understood that soil erosion by water released carbon, thus recognized as carbon source process. While geologist in sedimentation studied that water erosion resulted in soil carbon sink. 2) The mechanisms of soil organic carbon stability are classified as selective stabilization, physical protection, and orgao-mineral binding chemical stabilization. Selective stabilization refers to that the recycling period of some carbon is very long in over 100 years, thus they are not decomposed in this period. The physical protection refers to that soil particles, aggregates, layered silicate, molecular hydrophobicity and molecular nesting block the organic carbon and decomposer, so that it cannot be fully contacted and exist stably in the soil for a long time. Orgao-mineral binding chemical stabilization refers to that the organic carbon and soil mineral binding through coordination body exchange, polyvalent cationic bridge, hydrogen binding and molecular electrostatic attraction, so as to prolong the time of organic carbon turnover. 3) The research trends in this field include 4 aspects:Transport loss and composition change of dissolved organic carbon under erosion, migration and loss of organic carbon components by different erosion dynamics, renewal and stability of organic carbon in eroded in situ region, and stability of organic carbon in sedimentary area and its mechanism.[Conclusions] Current researches about soil carbon stability under water erosion demonstrate that the mechanisms of soil organic carbon stability are affected by water erosion.
ZHU Hong, WANG Lu, KONG Linggang, BI Sisheng, MENG Shiyuan, ZHANG Zhihao, WANG Huatian, ZHAN Zhongcai, LIU Xiumei, TANG Jin, CHEN Shuying, CONG Guizhi
Effect of irrigation with magnetized saline water on grape seedlings and ionic homeostasis
[Background] Plant growth can be inhibited by salinity conditions, which could lead to an osmotic stress and ion poisoning, hence causing decreases in yield and quality of crops. The magnetic technology, as a primer eco-friendly technique, can be used to the exploration and utilization of saline water. Consequently, the magnetic saline water could contribute to reduce the increasing pressure on freshwater resources in irrigation farming, especially in saline areas.[Methods] A pot experiment was carried out in a greenhouse, and two-year-old seedlings of Vitis vinifera×V. labrusca 'Summer Black' were used as the test materials. The irrigational experiments were performed by different concentration of NaCl solution (0, 3.0 and 6.0 g/L) under magnetic and non-magnetic treatments. The characteristics of biomass, survival ratio, salt sensitive index, roots morphology parameters and ionic content (Na+, K+, Ca2+ and Mg2+) were determined using harvested method and atomic absorption spectrometry (AAS). The aim in our study is to explore the effect of saline water on grape seedling growth under magnetic field.[Results] 1) The seedling growth and biomass of grapes were suppressed after suffering to saline conditions, while the survival ratio of the seedlings decreased in the treatment of 6.0 g/L NaCl solution. However, the irrigation with magnetized water stimulated the seedling growth, increased the shoots length, biomass, root/shoot ratio and survival ratio, while decreased the salt sensitive index. 2) The Na+ contents in grape seedlings raised with the increase of NaCl solution (P<0.05), whereas the ratios of K+/Na+, Ca2+/Na+, Mg2+/Na+ significantly decreased (P<0.05). Differing from increasing content of Na+ in non-magnetized water managements, magnetically treated water resulted in a lower Na+ contents, but an enhancement in the ability of rejecting Na+ in grape stem and root as well as in the absorption and transportation of K+, Ca2+ and Mg2+, also increases in the accumulation of Ca2+ and Mg2+ in leaves.[Conclusions] From the above results, we could see that, the seedling growth is improved when irrigating with magnetized saline water, also the salt tolerance and ion homeostasis of grapevines is enhanced by impacting of magnetic treatment. And these positive influences induced by the magnetic field would provide a theoretical foundation for the application of the magnetic technology in saline areas and saline water management.
PAN Xi, LUO Wei, DUAN Xingwu, ZHONG Ronghua, LI Yuxiang
Advances in evaluation methods of soil and water conservation benefits in China
[Background] China is among the countries that suffer most serious soil erosion in the world. During the process of soil erosion control, various methods were developed to evaluate the benefits of soil and water conservation measures. However, it is difficult to select a method from so many for specific context due to lack of a systemic summary of the evaluation methods to clarify and compare the advantages and scope of application of existing methods.[Methods] Based on literature survey, we summarized the characteristics, strengths and weaknesses and scope of application of the existing evaluation methods. The information of the methods was collected from 33 core papers out of 892 papers published in Chinese in the past 20 years with the keywords of "soil and water conservation" and "benefits evaluation".[Results] Eleven methods were widely used to evaluate the benefits of soil and water conservation at present, including empirical evaluation method, BP artificial neural network method, genetic algorithm, double-set assessment indexes system method, fuzzy comprehensive evaluation method, grey correlation analysis method,TOPSIS method, ontology knowledge base method, matter-element extension model, weighted summation formula method, and comprehensive evaluation methods. There are different scopes of application for different methods according to their characteristics, advantages and limitations. Weighted summation method is mainly suitable for evaluation in large-scale region or watershed as it has no requirements on the number of indicators and takes the relationships among the indicators into consideration. Genetic algorithm and TOPSIS method are more suitable for comparison of benefits among different soil and water conservation measures and measures selection; because these two methods could be used to calculate the optimal solution for the benefits obtained from different soil and water conservation measures. Fuzzy comprehensive evaluation method and grey correlation analysis are suitable for areas with complex environments where data are scarce or difficult to acquire, which had lower requirements for data and could generate more objective evaluation results.[Conclusions] In the future, researches should be focused on the exploration and application of new methods by combining computer technology and artificial intelligence, integrating theories with multiple methods, and modeling, etc. In order to improve the benefits of soil and water conservation projects, the application of evaluation methods should be selected according to local physical and socio-economic conditions with long-term monitoring and timely adjustment. Besides, relevant departments should draft general criteria for benefits evaluation of soil and water conservation, which could be used among different soil erosion prevention areas across the country to facilitate comparison among different areas, and promote the performance of soil and water conservation projects in China.
