XI Peidong, ZHANG Pengcheng, HE Weiyuan, TANG Bingzhe, HE Binghui, LI Tianyang
Response of nitrogen and phosphorus losses to different farming treatments in purple sloping farmland under simulated rainfall
[Background] Soil erosion has been the most serious environmental problem around the world, which leads to the losses of soil nitrogen (N) and phosphorus (P) in sloping farmland, resulting in dramatically non-point source pollution. Purple soil is widely distributed in southwestern China and is easily eroded owing to its relatively fast weathering rate of purplish parent materials. Sloping farmland is an important grain planting strategy in purple soil area, which usually experiences cross ridge and combined application of organic fertilizer and other agricultural measures to control soil erosion. This work is to determine the effects of different farming treatments on N and P losses in purple sloping farmland.[Methods] Three rainfall intensities (60, 90 and 120 mm/h) were adopted to conduct the rainfall simulations on runoff plots (length 8 m×width 4 m) located in a 15 ° purple sloping farmland.The changed processes of runoff and sediment yield and the characteristics of nitrogen and phosphorus losses were analyzed with three farming treatments including longitudinal ridge with single application of chemical fertilizer (T1, control), longitudinal ridge with chemical fertilizer and organic fertilizer (T2), and cross ridge with single application of chemical fertilizer (T3). One-way ANOVA and regression analysis were used to analyze the relationship between indicators.[Results] 1) The losses of N tended to be first increase and then maintained a certain volatility after reaching the peak, while the losses of P increased first and then declined after reaching the peak. 2) The different farming treatments showed statistically significant effects on runoff coefficient, sediment yield, and N and P losses under most conditions (P<0.05), except for the runoff coefficient (P>0.05) under the 90 mm/h intensity. 3) T2 and T3 significantly reduced the losses of N and P in comparison to T1 under different rainfall intensities, especially in lower rainfall intensity. The N and P reduction ratio were 19.36%-62.19% and 20.03%-58.01% for T2, and were 47.09%-78.45% and 50.97%-82.27% for T3, respectively. 4) Both N and P losses showed significantly positive power correlation with runoff coefficient and sediment yield (R2 is 0.787-0.893).[Conculsions] The longitudinal ridge with chemical fertilizer and organic fertilizer on the cross ridge with single application of chemical fertilizer can effectively reduce soil erosion and N and P losses in purple sloping farmland. These measures have significant effects on the prevention and control of non-point source pollution in purple sloping farming, and effectiveness of the cross ridge with single application of chemical fertilizer is more stable than the longitudinal ridge with chemical fertilizer and organic fertilizer.
DING Chao, ZHANG Shengmin, HU Wei, YAN Yue, QI Zhi, HAN Xing, ZHANG Xingyi
Field validation of gully survey of national census for soil conservation in the black soil region of Northeast China
[Background] A field survey of gully erosion in a typical black soil region was conducted to verify the results from remote sensing interpretation announced by Chinese government in 2013, aiming to provide a scientific basis for the evaluation and prevention of gully erosion in the black soil region of Northeast China.[Methods] A rolling hilly region of 450 km2 with severe gully erosion was selected as the field survey area of this study. The land use, geographic coordinates and morphological parameters of gullies were measured to be compared and analyzed with the results of the national census announcement in this study region.[Results] The remote sensing interpretation only focused on the gullies with length of 100-5 000 m. Our results showed that the gully number (1 044) obtained by field survey including the gullies of <100 m in length (235) and main gully channels (13) was nearly double that (574) from remote sensing interpretation, indicating the accuracy rate of the number of gullies confirmed by remote sensing interpretation was 72.1% in the survey area. The gully density obtained by remote sensing interpretation was 0.78 km/km2 that was close to half of that (1.2 km/km2) by field survey. The gully area by remote sensing interpretation and field survey was 1.44% and 2.45%, respectively, implying that the remote sensing interpretation underestimated the gully intensity by one class according to the national classification standard of gully erosion intensity. The lower quantity of different types of gullies obtained by remote sensing interpretation than field survey was mainly due to the low-resolution DEM and the difficulty of obtaining some gully information from satellite images. The gully volume had the optimal relation with gully area (R2=0.936).[Conculsions] Overall, both number of gullies and intensity of gully erosion in the survey area are higher than the results announced by government in 2013. The most gullies are small and medium-sized gullies developed in cultivated lands, which are mostly in the development stage and are relatively easy to manage.
CHEN Yuxuan, YANG Qinke, LIU Baoyuan, HUANG Chenlu, WANG Chunmei, PANG Guowei
Assessment of soil erosion intensity in Pearl River Basin based on CSLE model
[Background] Soil erosion has seriously threatened the social and economic development in many regions of the world. The Pearl River Delta is one of the most dynamic economic zones in China and even the world. The Pearl River Basin is located in the south subtropical region, with the disadvantages of heavy precipitation and thin soil. Coupled with the interference of human activities, soil erosion has become more severe. However, it is still insufficient in the current research on the spatial differentiation characteristics and main controlling factors of soil erosion in the Pearl River Basin, which is not suitable for the prosperous economy. Therefore, it is urgent to make use of modern scientific and technological means to systematically study soil erosion in this area.[Methods] In this study, the Pearl River Basin was selected as the study area, and China Water Conservancy Survey (WRI) was used to set up sampling survey units. The Chinese Soil Loss Equation (CSLE) was used, based on the sample survey unit data interpreted by high-resolution remote sensing images and thematic data on soil erosion factors. The map algebra and spatial interpolation were used to calculate the soil erosion rate map in the study area, and to analyze the spatial pattern of soil erosion in the Pearl River Basin. Furthermore, the geo-detector method was used to quantitatively identify the main influencing factors.[Results] 1) Among the factors affecting soil erosion rate, R and LS are generally higher, which were the main inducing factors of soil erosion. The B factor value was low, while the E and T factor values were high. The study area had good vegetation coverage and was the main inhibitor of soil erosion. 2) The soil erosion in the Pearl River Basin mainly concentrated in Guizhou and Yunnan provinces, central Guangxi and coastal areas of Guangdong province. The areas of intense and extremely intense erosion were relatively small and distributed on relatively scattered sloping farmland. The mean values of soil erosion rate mapped by map algebra and spatial interpolation were 791.78 t/(km2·a) and 615.37 t/(km2·a) respectively. The mean values of the two soil erosion rates were relatively close. The average value of soil erosion rate calculated by map algebra method was higher, which might be related to the difficulty of integrating water conservation measures into the calculation. 3) Except for hilly and mountainous area of Zhejiang-Fujian, land use pattern was the main controlling factor of soil erosion, and the influencing factor Q value was above 47%. Secondly, B factor had a great influence on soil erosion rate and its spatial distribution. T factor ranked the third, and K factor and R factor had little influence. That was related to the high vegetation coverage in the study area, which was dominated by forest and grass vegetation.[Conculsions] Two methods of map algebra and spatial interpolation are used to map soil erosion in the Pearl River Basin. Soil erosion is mainly controlled by land use and biological measures. Adjusting land use structure and optimizing the soil conservation function of vegetation are the main direction of future management. This study may provide a reliable scientific basis for ecological environment restoration and soil conservation in this region, and promote the development of soil erosion research in subtropical region.
On the risk grading classification and control for the selection of greening tree species
[Background] The selection of greening tree species is the key work to promote land greening and ecosystem restoration. In addition, the diversity of tree species is one of the most important ways to improve regional biodiversity. Due to the potential risks for the selection of greening tree species, how to search the optimum balance among varied greening tree species becomes the urgent problem in practices. It was well acknowledged that the classification and control of risk grading for greening tree species selection is an important measures to promote the diversity of tree species selection and improve the quality of afforestation.[Methods] Based on the theory of risk management, this study constructed the standards for the classification of risk grading for greening tree species from the perspectives of theory and practice using the combined results of vegetation division and survey monitoring in China.[Results] According to the classification principle, the risk level of tree species selection was divided into five levels, and correspondingly mitigation measures were supplied. 1) The first level owned the small risk. It should be used as the preferred tree species, but not the conservative selection to reduce the diversity of tree species selection. 2) The second risk level was also the small risk and tree species in this grade were worth to recommend. 3) The third level is general risk and tree species in this grade were applied appropriately. 4) The risk in the fourth level was higher. These tree species in this grade were not recommended to apply in large-scale. If exceeding a certain scale, it was necessary to demonstrate feasibility argumentation for preventing biological invasion. 5) The fifth level was the highest risk, this grade of tree species should be strictly prohibited except for necessary scientific research.[Conculsions] The establishment of risk classification of greening tree species and corresponding resolving measures is helpful to enrich tree species selection, and has great meaning for afforestation in large-scale and ecosystem restoration.
Spatial patterns of forest ecosystem services in Liaoning province
[Background] Forests are the important component of terrestrial ecosystems and provide a variety of benefits for human. The assessment of forest ecosystem services has become a bridge linking human society and the natural environment.[Methods] Based on the forest resources data in Liaoning province in 2017, we used the national standard specifications of the People's Republic of China "Specifications for Assessment of Forest Ecosystem Service in China" (GB/T 38582-2020) with the distributed measurement method to assess the services of soil conservation, forest nutrition retention, water conservation, carbon fixation and oxygen release, purification of atmospheric environment, in the Liaoning province. Grey relational method was used to analyze the influencing factors.[Results] 1) The amount of soil conservation in the forest ecosystem of Liaoning province in 2017 was 24 846.82×104 t; a total of 2 198.03×104 t of fertilizers was preserved; the amount of forest nutrient retention was 59.00×104 t; water conservation was 208.20×108 m3; carbon fixation was 1 938.55×104 t; oxygen release was 4 440.79×104 t; the forest ecosystem provided 3.89×1025 negative ion and absorbed 79.32×104 t of gaseous pollutants, and retented 10 153.67×104 t TSP, the masses of retented PM10 and PM2.5 substances were 2 164.40×104 kg and 613.12×104 kg respectively. 2) The service function of forest ecosystem generally presented the distribution pattern of mountainous area in eastern Liaoning > Northwest area > The coastal area of central and southern. Dandong, Fushun and Benxi had higher services and made proportion of more than 40% services, while Shenyang, Jinzhou and Panjin have lower services. 3) The factor with the highest degree of correlation with ecosystem service was precipitation (0.779 7-0.819 9), and the correlation between climate factors and service functions was higher than policy factors and socio-economic factors.[Conculsions] This study can provide a scientific basis for scientifically carrying out forestry ecological projects in different regions of Liaoning Province, timely adjusting the direction of forestry development, and designing the path to realize the value of ecological products.
ZHANG Zeyu, SUN Ruizhe, ZHAO Yunlong, LI Zefang, AN Ni, ZHOU Zihao, LI Guanglu
Experiment on terraced field of ramming earth construction in the expansive soil area of southern Shaanxi
[Background] This work aims to study the improvement effect of quicklime and cement on expansive soil and provide important theoretical support and technical basis for the construction of terraces in southern Shaanxi.[Methods] Taking typical expansive soil as the object, the expansive soil was mixed with certain proportion of quicklime and cement(2%, 4%, 6%, and 8%), then the mixed soil was compacted with a compaction density of 1.65 g/m3 under the condition that the soil moisture was 22%. The traditional soil physical methods were used to determine the disintegration resistance, soil anti-scour ability, and the mechanical strength of the expansive soil terraces.[Results] 1) As the proportion of added quicklime or cement increased, both the expansive rate and expansive force of the expansive soil decreased significantly. When the addition proportion exceeded 4%, the expansive rate and expansive force reduced. 2) After adding 2% quicklime and cement, expansive soil collapsed the fastest. After adding more than 4% quicklime and cement, the disintegration speed of the expansive soil began to be gradually reduced, especially the performance was the best while adding 6% quicklime and 8% cement. 3) With the proportion of quicklime and cement added, the impulse resistance of the expansive soil gradually increased. After adding 2% of quicklime and cement, the impulse resistance of the expansive soil was greatly enhanced, and with the increase of the adding proportion, the impulse resistance of the expansive soil was not significant. 4) With the proportion of quicklime and cement increased, the water stability of the expansive soil gradually increased, and when the proportion of quicklime increased to 8%, the water stability of expansive soil began to decrease.[Conculsions] Adding cement and quicklime to the expansive soil way reduce the expansive rate of the expansive soil, and improve the anti-disintegration, impulse resistance and water stability of the soil. Under the premise of considering the economic benefits of the terrace construction, adding 4% quicklime and 6% cement can achieve the construction effect of the optimal expansion of the terraced fields.
Submerging stress response mechanism of 4 local herbaceous plants in the water-level-fluctuating zone of the Wanzhou section of the Three Gorges Reservoir Area
[Background] Screening and restoration of artificial vegetation is one of the important measures to control the ecological environment of the water-level-fluctuating zone of the Three Gorges Reservoir Area. In order to select more flood-resistant species suitable for vegetation construction and temporal spatial replacement, 4 indigenous herbaceous plants, Houttuynia cordata, Rumex acetosa, Kalimeris indica and Xanthium sibiricum) from the Three Gorges Reservoir (Wanzhou section), surviving in the recession period were taken to our experimental station for investigating their response mechanisms to short-term submerging stress.[Methods] Above 4 plants were treated for pot submerging and restoring experiment lasting 30 d. The plants were randomly divided into 3 groups of each 10 pots, CK group was under nature outside and no more adding water, the submerged group was watering until the top of plants, and the submerged + restored group was first 15 d submerged and later 15 d under natural outside condition. Morphological,photosynthetic and physiological and biochemical indices were measured at first day, 15 d, and 30 d respectively. The result data were processed by SPSS19.0 and One-way ANOVA.[Results] 1)The aboveground parts of H. cordata and K. indica were successively necrotic after 15 d of submerging, the aboveground parts of R. acetosa and X. sibiricum were survived for about 22 d, and the root length of X. sibiricum increased significantly in the environment of submerging and restoring. 2)After 15 d of submergence, the contents of proline (Pro), superoxide dismutase (SOD), catalase (CAT) and root activity(TTC content)of R. acetosa increased significantly compared to CK. After 15 d of restoring, net photosynthetic rate (Pn), transpiration rate (Tr), malondialdehyde (MDA), TTC, soluble sugar content and antioxidant enzyme activity increased significantly compared to CK. 3)After 15 d of submergence, MDA content, Pro content, SOD, CAT activity and TTC value of X. sibiricum increased significantly compared to CK, especially the values of Pro and TTC reached a very prominent difference. After 15 d of restoring, Pn, stomatal conductance (Gs), Pro content,SOD, CAT activity and TTC value increased notably. 4)After 15 d of submergence, Pn, intercellular CO2 concentration (Ci), CAT activity of H. cordata increased compared to CK, but no significant changes were observed after 15 d of restoring. 5)After 15 d of submergence, Ci, Gs, TTC, Pro, CAT of K. indica decreased drastically, MDA and SOD increased significantly.[Conculsions] The results indicated that X. sibiricum and R. formosana regulated the submerging stress mainly by enhancing root activity, antioxidant enzymes activity and Pro content, and the photosynthetic indexes and root activity were stimulated and enhanced after restoring, showing they were sensitive to submerging or had high submerging-tolerance. The photosynthetic index of H. cordata decreased significantly and no timely response in physiological aspect after submergence,showing it was insensitive to submerging stress. K. indica maintained energy balance of root system in anoxic environment by reducing root activity, showing it had lower submerging-tolerance.
YIN Xiaoai, YANG Xiuchao, HOU Rui, ZHAO Longshan, ZHANG Jinxin
Determination of canopy leaf area index of maize based on smart phone
[Background] Crop canopy plays an important role on rainfall distribution and soil and water conservation, and leaf area index (LAI) is a common quantitative index of crop canopy. There are two kinds of direct method and indirect method in the current measurement of plant leaf area. The direct method is time consuming and has poor repeatability, while the indirect method is complicated and requires expensive equipment and is not convenient to be carried in field. Based on the existing problems of crop canopy measuring method, this study aims to explore a fast measurement method of maize LAI using the mobile phone. It provides scientific and technological conditions for further improving the method of determining canopy parameters by using smart phones and developing an effective mobile APP for canopy LAI measurement.[Methods] In this study, according to the characteristics of maize canopy, PVC pipe and simulated leaves were used to simulate the canopy model of maize plants at different growth stages (elongation period, small trumpet period, big trumpet period, tasseling period and mature period). The canopy LAI of maize was measured through the processes of mobile phone image acquisition, canopy shadow area extraction and correction, model construction and verification. The experiment included 3 solar altitude (30°, 60° and 90°). The number of maize plants was 1, 2, 3, 6 and 9 plants respectively to represent different sampling areas. The plant row spacing was 30 cm×50 cm.[Results] There was a significant correlation between the number of planted plants and the projected canopy area (P<0.05). There was no significant relationship between the solar altitude and the projected area taken by mobile phones (P>0.05), the canopy projection areas (SM) extracted from mobile phone images was taken as the independent variable, and the canopy projection area (SC) drawn on coordinate paper was taken as the dependent variable. The optimal fitting equation of the two was as follows:SC=-0.009 6S2M+171.38SM-3 612.3 (R2=0.98). The fitting degree of this equation was high and reached significant level (P<0.05). There was a power function relationship between the projected area (SC) drawn by coordinate paper and the actual area (Sleaf), and the function relationship was as follows:Sleaf=0.141 2S0.985C(R2=0.97), P<0.05, the regression equation had a high degree of fitting.[Conculsions] The LAI measurement method designed in this paper is feasible, that is, the canopy LAI could be accurately determined by extracting the shadow area taken by smart phones (R2=0.96). This method simplifies the canopy area measurement of maize and provides a convenient solution for the monitoring of canopy parameters in the field.
Tensile deformation characteristics of a single root of Cassia bicapsularis in karst areas
[Background] The role of vegetation (grasses, shrubs, and trees) in slope stability and erosion has been well recognized and incorporated. The plant material especially the root system plays an important role in stabilizing slope and enhancing soil strength. The root system is very significant especially in karst areas with little soil and lots of stones. Root tensile properties are the basis for enhancing slope stability, and the process of root tensile deformation reflects the process of root system resisting external force. Therefore, it is useful to study the tensile properties of plants in karst area.[Methods] In order to explore the tensile deformation characteristics of a single root of Cassia bicapsularis, 5-year-old shrubs were selected as the research objects. Under the condition of different root diameter levels, different root length levels (50 and 100 mm) and different tensile rate levels (10 and 500 mm/min), the tensile force of a single root and tensile strength of a single root were assessed via tensile test for a single root. Furthermore, the stress-strain curves during the tensile process were recorded by experimental machine.[Results] 1) The tensile force of a single root of C. bicapsularis increased with the increase of root diameter according to a power function, while the tensile strength of a single root decreased with the increase of root diameter according to a logarithmic function. 2) The tensile deformation modes of C. bicapsularis were various and the process was complex. According to the shape of stress-strain curve, the curves were divided into three types:serrated type, single peak type and multi-peak type, and different types of curves corresponded to different deformation processes of a single root. The roots deformed in different ways to resist external forces, including elastic deformation, elastic-plastic deformation and root skin tearing. Different single roots exerted maximum tensile force through different deformation modes. 3) Chi-square test was carried out for stress-strain curves with different root lengths and different tensile rates. The results showed that there was no significant correlation between root length and tensile deformation characteristics of a single root, but the tensile rate had significant effect on the tensile deformation characteristics. When the tensile rate was 500 mm/min, all of the stress-strain curves were single peak type, because the fiber bundles were broken before they exerted tensile properties to external forces at a faster rate.[Conculsions] In this study, the root system of C. bicapsularis plays a better role in stabilizing the slope through complex deformation during tension. In the process of stretching, the complex deformation mode is used to resist deformation by the single root of C. bicapsularis. When landslide occurs, the complex deformation mode is more conducive to maintaining the stability of slope. But the root system is more likely to be destroyed at a faster stretching rate. The mechanical characteristics of single root deformation of plant roots were discussed in order to provide a theoretical basis for the mechanism of soil consolidation and slope protection of roots in karst areas.
Ways and countermeasures to achieve carbon-neutral in soil and water conservation
[Background] In order to achieve carbon neutrality by 2060, China will adopt stronger policies and measures. Controlling soil erosion and establishing a good ecological environment is not only the demand of ecological civilization construction, but also an important way to achieve the goal of carbon neutrality.[Methods] This paper introduces the impact of severe soil erosion on the carbon source and sink of ecosystem, analyzes the carbon emission reduction effect of soil and water conservation engineering measures, forest and grass measures, agricultural measures and ecological clean small watershed management. And puts forward the ways and countermeasures of carbon neutral soil and water conservation.[Results and Conclusions] In order to achieve greater emissions reductions, we need to find new breakthroughs in soil and water conservation. We need to implement the assessment index of soil and water conservation restoration and control of carbon sink increase. Including but not limited to:1) Implement the assessment index of soil and water conservation and restoration and control of carbon sink increase, and scientifically evaluate the contribution of soil and water conservation ecological restoration to carbon peak and carbon neutrality. 2) carry out intensive planning and implementation of soil and water conservation and ecological restoration projects, and enhance the carbon sequestration capacity of ecosystems and the carbon sequestration capacity of forests and grasslands. 3) Comprehensive implementation of ecological clean small watershed construction, continue to tap the potential of soil and water conservation carbon sink growth. 4) Enhance the carbon absorption capacity of agro-ecosystem, combined with comprehensive treatment of mountains, rivers, forests, farmland, lakes and grass, and contribute a steady stream of green power to negative emissions.
SONG Xiuyu, WANG Yunzhu, ZHANG Yu, LI Jinpeng, ZHANG Hengshuo, CHENG Jinhua, ZHA Tonggang
Differences analysis of soil and water conservation measures between schemes and construction drawing designs of soil and water conservation
[Background] Comparing the differences between soil and water conservation schemes (SWCS) and construction drawing designs (CDD) may effectively master the implementation and effects of soil and water conservation measures, and hence providing technical support for the sustainable development of soil and water conservation for production and construction project.[Methods] Differences of 4 rainwater utilization measures (rainwater pipeline, permeable pavement, low elevation greenbelt, and rainwater harvesting pool) and 4 vegetation measures (arbor, shrubs, herb and grass-embedded bricks) of 50 typical projects in Beijing between SWCS and CDD were compared, and situations of compliance with standard for 3 indexes of the forest coverage, rainwater utilization rate and rate of hardened ground were analyzed.[Results] 1) There were widespread differences in soil and water conservation measures between SWCS and CDD. There were markedly differences in one or more water conservation measures for 90% of the 50 analyzed projects, and the number of projects with obvious differences in rainwater utilization measures was lower than that of vegetation measures. 2) Except the rainwater harvesting pool, there were obvious differences in the other three rainwater utilization measures. Except the socking bricks, the other three vegetation measures showed obvious differences, with the largest reduction rate of trees was 84.3% and the largest increase rate of shrubs was 103.2%. 3) Soil and water loss indicators reached the standard well, with rainwater utilization rate, forest coverage, and control rate of hardening ground were 90%, 84% and 100% respectively.[Conclusions] Therefore, the main reason of the differences between SWCS and CDD was that the following design was complied with the scheme of protecting indexes of soil and water losses, but ignoring the specific layout system of soil and water conservation systems. The process management should be strengthened in the coming projects of production and construction projects.
